A story for Christmas

This is a true story. It happened within the past year. Therefore it is not the Christmas Story. But it is about the spirit of Christmas. You may have heard it before. Nonetheless, it is worth a second look during this season of goodwill to all. Here is the story:

A flight attendant came to the pilot and said, “We have HR on board.” (HR stands for Human Remains.) The pilot asked the flight attendant to have the escort board early. He wished to see him.

A young army sergeant entered the flight deck. The pilot asked about his soldier. “My soldier is on his way back to Virginia,” he said. (Military escorts speak of their fallen as if they are still alive.)

The pilot asked if there was anything he could do. The sarge politely said, “No.” They shook hands. The escort went to the back of the plane.

After takeoff, the pilot was told by a flight attendant, “I just found out that the family of the soldier we are carrying is on board. The father, mother, wife and two-year old daughter are escorting their son, husband and father home. And they are upset because they were not able to see the container before leaving.”

The flight was a connecting flight with a four hour lay over. The father asked if it was possible to view his son before his last leg home. The family wanted to witness the body being taken off the plane.

The pilot said he would try. He decided to bypass normal communications. He contacted his flight dispatcher directly. He forwarded the father’s request. The dispatcher said that he would get back to the pilot.

Two hours went by. No word from the ground. The pilot then asked for an update. The reply read: “Captain, sorry it has taken so long to get back to you . . . Upon arrival a dedicated escort team will meet the aircraft. The team will escort the family to the ramp and plane side. A van will be used to load the remains, with a secondary van for the family. The family will be taken to a private area inside the terminal where the remains can be seen from a ramp. When the connecting flight arrives the family will again be escorted to the ramp to watch the remains being loaded. Captain, most of us here in flight control are veterans. Please pass our condolences on to the family.”

The pilot thanked the ground crew. The message was printed out and given to the father.

After landing at the busy airport, the pilot was told by the ramp controller that all traffic was being held for his plane. Then the pilot realized that once the seat belt sign was turned off all passengers, as usual, would stand at once in their effort to disembark ASAP and thus delay the family.

So the pilot made arrangements to stop short of the gate. He made this announcement, ” Ladies and gentlemen, this is your Captain speaking. We have a passenger on board who deserves your honor and respect. His name in Private ___, a soldier who recently lost his life. Private ___ is under your feet in the cargo hold. Escorting him today is Sergeant ___. Also on board are his father, mother, wife and daughter. Your flight crew is requesting all passengers remain in their seats to allow the family to exit the aircraft first. Thank you.”

The plane slowly taxied to the gate and shutdown. The pilot noticed the flight attendants crying. Every passenger was seated. All waited for the family to exit. When the family got up to leave, a single passenger slowly started to clap. Then two. Moments later, more clapping. Then the entire plane. “God bless you . . . I’m sorry . . . Thank you,” and other kind words were quietly spoken to the family as they made their way down the aisle.

Later when the passengers left, they thanked the pilot. Tears were in many an eye.

That is our story for Christmas. Were you surprised at everyone’s reactions? Do you think that this was an unusual, an exceptional plane load of people? Or that it represents the norm, that any pilot, any flight dispatcher, any ramp controller, any airline passenger would have reacted in the same way?

I believe the latter. It was just another fanfare for the common man. Within each of us there is something deep inside that is good and kind. Most of the time it is well hidden. Let’s stop playing hide and seek. There is no need to confine your thoughts and your feelings. Let them out. All of them. Show the world, not just your doctor, that you have a pulse

Διάδρομος Απογείωσης/Προσγείωσης [GR]

Αερολιμένας Helsinki-Vantaa , διάδρομος 33

Ο διάδρομος (RWY) είναι ένας οριοθετημένος χώρος στο έδαφος, όπου τα αεροσκάφη απογειώνονται και προσγειώνονται. Στην καθομιλουμένη χρησιμοποιούμε τον όρο "αεροδιάδρομος", αντί για διάδρομος. Αυτό είναι λάθος καθώς οι αεροδιάδρομοι είναι οριοθετημένες περιοχές, αλλά βρίσκονται στον αέρα. Οι διάδρομοι μπορεί να είναι κατασκευασμένοι από τον άνθρωπο, με την χρήση υλικών όπως άσφαλτος, τσιμέντο ή και μίξη αυτών των δύο ή μπορεί να είναι 'φυσικοί' όπως σε ιδιωτικά αεροδρόμια που ο δάδρομος είναι από γρασίδι, χώμα ή ακόμα και πάγο-χιόνι.

Προσανατολισμός και διαστάσεις

Οι διάδρομοι είναι ονομσμένοι με αριθμούς από το 01 έως το 36. Αυτοί οι αριθμοί προκύπτουν από τις μοίρες μια πυξίδας. Έτσι ο 09 ανατολικός θα είναι στις 90°, ο 18 βόριος θα είναι στις 180°,ο 27 θα είναι δυτικός στις 270° και ο 36 θα είναι στον νότο, στις 360° (αντί για 0°). Ο διάδρομος μπορεί να χρησιμοποιηθεί και από τις δυο κατευθύνσεις και η κάθε κατεύθυνση έχει το δικό της όνομα. π.χ. "διάδρομος 33" από την μια και "διάδρομος 15" από την άλλη κατεύθυνση. Οι δύο αριθμοί έχουν απόσταση ίση με 18 (= 180°).

Διεθνές αεροδρόμιο El Dorado

 ,διάδρομος 31R/13L

Αν υπάρχουν περισσότεροι από ένας διάδρομοι στην ίδια κατεύθυνση (παράλληλοι), ο κάθε διάδρομος συνοδεύεται με (L) για αριστερά, (C) για το κέντρο και (R) για δεξιά. Για παράδειγμα ο διάδρομος δεκαπέντε αριστερός είναι 15L. Ο διάδρομος 03L ονομάζεται 21R, όταν χρησιμοποιείται από την αντίθετη.

Σα μεγάλα αεροδρόμια όπως του Los Angeles, Detroit Metropolitan Wayne County, Hartsfield-Jackson Atlanta, Denver, and Dallas-Fort Worth, που έχουν περισσότερους από 3 παράλληλους διαδρόμους, αλλάζουν τα ονόματά τους κατά 10 μοίρες για να αποφευχθεί η σύγχιση. Για παράδειγμα στο Los Angeles ονομάζουν τους διαδρόμους 6L, 6R, 7L, και 7R, παρόλο που είναι παράλληλοι. Στο Dallas-Fort Worth, υπάρχουν 5 παράλληλοι, που ονομάζονται 17L, 17C, 17R, 18L, και 18R. Όλοι είναι προσανατολισμένοι στις 175.4 μοίρες.
Για την καλύτερη κατανόηση μέσω του ασυρμάτου, κάθε ψηφίο του διαρόμου προφέρεται ξεχωριστά. Συνηθίζεται να αναφέρεται ένα μηδενικό πριν τον αεροδιάδρομο (πχ για τον 90 θα πούμε 'διάδρομος  μηδέν εννιά μηδέν). Αυτό έχει καθιερωθεί από τον διεθνή οργανισμό πολιτικής αεροπορίας (ICAO).

Ο ακριβής προσανατολισμός του διαδρόμου, αλλάζει με την πάροδο του χρόνου, καθώς οι μαγνητικοί πόλοι της γης αργά μεταβάλλουν τον μαγνητικό προσανατολισμό. Ανάλογα με την θέση του αεροδρομίου , κρίνεται απαραίτητο να γίνονται αλλαγές στους διαδρόμους. Καθώς οι διάδρομοι είναι ορισμένοι με προσανατολισμό ανα 10 μοίρες, αυτές οι αλλαγές δεν είναι και τόσο συχνές. Για παράδειγμα, αν ένας διάδρομος είναι στις 233 μοίρες, θα ονομάζεται 'Διάδρομος 23'. Αν ο μαγνητικός προσανατλισμός αλλάξει κατά 5 μοίρες, ο διάδρομος θα παραμείνει με το όνομα 'Διάδρομος 23'. Αντιθέτως, αν ο προσανατολισμός μεταβληθεί και φτάσει στις 224 μοίρες, τότε ο διάδρομος θα αλλάξει σε 'Διάδρομος 23'. Επειδή η μεταβολή του μαγνητικού προσανατολισμού είναι ιδιαίτερα αργή, αλλαγές σε ονόματα είναι ιδιαίτεα ασυνήθιστες και δεν είναι ιδιαίτερα ευπρόσδεκτες καθώς οι αεροναυτικοί χάρτες πρέπει να αλλάξουν. Όποτε κρίνονται απαραίτητες αυτές οι αλλαγές, όλες οι εργασίες γίνονται την νύχτα καθώς ο διάδρομος πρέπει να μείνει κλειστός. Τον Ιούλιο του2009, για παράδειγμα, το London Stansted Airport στο Ηνωμένο Βασίλειο άλλαξε τον διάδρομο 05/23 σε 04/22 κατά την δειάρκια της νύχτας.

Οι διάδρομοι έχοιν ποικοίλες διαστάσεις. Μπορεί να είναι μικροί με 245 μέτρα μήκος και 8 μέτρα πλάτος, μπορεί να είναι μεγάλοι με 5,500 μετρα μήκος και 80 μέτρα πλάτος και χρησιμοποιούνται στα μεγάλα διεθνή αεροδρόμια για τα μεγάλα τζέτ, ένώ υπάρχουν και οι τεράστιοι με 11,917 μέτρα μήκος και 274 μέτρα πλάτος, όπως ο 17/35 στην αεροπορική βάση Edwards Air Force Base στην Καλιφόρνια, που χρησιμοποιείται για την προσγείωση διαστημικών σταθμών και διαστημοπλοίων.

Τοποθέτηση και ομαδοποίηση

Δύο διάδρομοι που έχουν τον ίδιο προσανατολισμό είναι είτε διπλοί ή παράλληλοι, αναλόγως με την μεταξύ τους απόσταση. Σε κάποιες χώρες, οι κανονισμοί επιτρέπουν την λειτουργεία μόνο ενός από τους δύο παράλληλους διαδρόμους, όταν υπάρχουν ακραίες καταστάσεις (πχ. καταιγίδες, δυνατός άνεμος, κτλ). 

Καθιερωμένες αποστάσεις

TORA

Takeoff Run Available - Το μήκος του διαδρόμου που χρησιμοποιείται για την επεδάφια επιτάγχυνση (ground run) μέχρι το αεροσκάφος να απογειωθεί.

TODA

Takeoff Distance Available - Το μήκος του διαρόμου για την ευθυγράμιση και τη απογείωση.

(Ο χώρος που δίνεται για ευθυγράμιση είναι: TODA - TORA + 1.5 * TORA, σύμφωνα με την JAR.)

Accelerate-Stop Distance Available - Το μήκος του διαδρόμου όπου ο πιλότος επιταχύνει για την απογείωση μαζί με το τμήμα του διαδρόμου που χρησημοποιείται για να σταματήσει το αεροσκάφος, εφόσον αυτό υπάρχει.

LDA

Landing Distance Available - Το μήκος του διαδρόμου που είναι διαθέσιμο για την τελική ακινητοποίηση του αεροσκάφους, μετά την προσγείωση.

EDA

Emergency Distance Available - Το μήκος του LDA (ή TORA) με ένα επιπλέον διάστημα.

Τμήματα του διαδρόμου

• Η Runway Safety Area είναι καθαρή και επίπεδη περιοχή περιμετρικά από τον διάδρομο, που διατηρείται χωρίς εμπόδια τα οποία μπορούν να επιρεάσουν την κίνηση του αεροσκάφους.
• Ο Διάδρομος που είναι η επιφάνεια ανάμεσα στις δύο κάθετες γραμμές και συνήθως έχει αριθμούς και την κεντρική διακεκομμένη γραμμή, η οποία δεν υπερβαίνει το όριο των κάθετων γραμμών.
• Τα Blast pads είναι κατασκευασμένα πριν την αρχή του διαδρόμου ,όπου δημιουργούνται ισυρά ρεύματα αέρος από τα μεγάλα τζέτ, όταν αυτά ετοιμάζονται να απογειωθούν. Αυτά τα ρεύματα αέρος μπορούν να καταστρέψουν τον αεροδιάδρομο και να διαυρώσουν το έδαφος. Αυτές οι περιοχές κατασκευάζονται και στο τέλος του αεροδιαδρόμου, ως χώροι ανάγκης, για να σταματά τα αεροσκάφη όταν η προσγείωση δεν πάει καλά ή για να σταματήσουν το αεροσκάφος σε περίπτωση ακύρωσης της απογείωσης. Τα Blast pads δεν είναι τόσο ανθεκτικά όσο ο κύριος διάδρομος και για αυτό δεν επιτρέπεται στα αεροσκάφη να προσγειώνονται , να απογειώνονται ή να κινούνται στα blast pads, εκτός αν υπάρχει ανάγκη. Τα blast pads είναι μαρκαρισμένα με κίτρινα βελάκια που δείχνουν τον αεροδιάδρομο.

• Τα Displaced thresholds (Βέλη κατεύθυνσης) χρησιμοποιούνται για απογείωση, για κίνηση στο έδαφος και για φρενάρισμα μετά την προσγείωση, αλλά δεν χρησιμοποιούνται για την πρώτη επαφή του αεροσκάφους με το έδαφος (touchdown). Αυτό το τμήμα υπάρχει διότι η αντοχή του αεροδιαδρόμου είναι μικρότερη στα άκρα του και μπορεί να φθαρεί ο διάδρομος από την καθίζηση και τα ωστικά κύματα των μηχανών των αεροσκαφών. Το τμήμα αυτό είναι μαρκαρισμένο με λευκά βέλη που καταλήγουν στην αρχή του αεροδιαδρόμου.

Φωτισμός του διαδρόμου

Ιστορία

Ο πρώτος φωτισμένος διάδρομος εμφανίστηκε το 1930 στο Cleveland Municipal Airport στο Cleveland του Ohio, στις ΗΠΑ. Η γραμμή των φωτών σε ένα πεδίο προσεδάφισης για να καθοδηγεί τα αεροσκάφη να προσγειωθούν και να απογειωθούν, είναι γνωστή ως 'μονοπάτι με φώτα' (flare path).

Τεχνικές Προδιαγραφές

Ο φωτισμός στους διαδρόμους επιτρέπει τις νυχτερινές προσγειώσεις. Όταν τα φώτα φαίνονται από τον αέρα, σχηματίζουν το περίγραμμα του αεροδιαδρόμου. Συνήθως οι διάδρομοι έχουν τα εξής είδη φωτιστικών συστημάτων:

• Runway End Identification Lights (REIL) – ζεύγος από συγχρονισμένα φώτα που αναβοσβήνουν και είναι τοποθετημένα στα threshold του διαδρόμου, ένα σε κάθε μεριά.

• Runway end lights – δύο σετ των τεσσάρων φωτών τοποθετημένα και στις δύο πλευρές του διαδρόμου, τα οποία όταν τα βλέπει ο πιλότος στην προσγείωση φαίνονται πράσινα και όταν παρατηρούνται από τον διάδρομο φαίνονται κόκκινα.

• Runway edge lights – λευκά κλιμακούμενα φώτα που εκτείνονται καθόλο το μήκος του διαδρόμου και στις δύο πλευρές. Αυτά τα φώτα στα τελευταία 610 μέτρα του αεροδιαδρόμου γίνονται κίτρινα.

• Οι taxiways (διάδρομοι περιμετρικά του διαδρόμου όπου τα αεροσκάφη κινούνται από και προς τον διάδρομο) διαφοροποιούνται από τον διάδρομο καθώς είναι περιστοιχισμένοι από μπλε φώτα ή έχουν μια πράσινη γραμμή από φώτα στο κέντρο τους.

• Runway Centerline Lighting System (RCLS) – φώτα τα οποία είναι τοποθετημένα στο κέντρο του διαδόμου ανά 15 μέτρα, με τέτοιον τρόπο ώστε να μην εξέχουν από την άσφαλτο. Είναι λευκού χρώματος εκτός από τα τελευταία 915 μέτρα ,όπου στα πρώτα 610 μέτρα εναλλάσονται λευκά και κόκκινα, ενώ στα τελευταία 305 μέτρα είναι κόκκινα.

• Touchdown Zone Lights (TDZL) – σειρές από λευκές μπάρες με φώτα (τρία ανα σειρά) και στις δύο πλευρές της κεντρικής γραμμής του διαδρόμου, για τα πρώτα 914 μέτρα.

• Taxiway Centerline Lead-Off Lights – φώτα τοποθετημένα κατα μήκος των σημείων εξόδου των αεροπλάνων από τον διάδρομο, τα οποία εναλλάσονται από πράσινο σε κίτρινο. Ξεκινάν από πράσινο φως, που είναι περίπου στην κεντρική γραμμή του διαδρόμου και καταλήγουν στο σημείο όπου τα αεροσκάφη περιμένουν πριν την είσοδο στον διάδρομο (holding position), μετά τον taxiway.

• Land and Hold Short Lights – μια σειρά από λευκά φώτα εγκατεστημένα παράλληλα με τον διάδρομο, στις εξόδους-εισόδους των αεροσκαφών, για να υποδεικνύουν την θέση αναμονής.

• Approach Lighting System (ALS) – ένα σύστημα από φώτα που είναι τοποθετημένο πρίν τον διάδρομο, στην πλευρά από την οποία γίνονται οι προσγειώσεις. Αποτελείται από αρκετά φώτα τα οποία καταλήγουν στην αρχή του διαδρόμου.

Σύμφωνα με τους Καναδικούς κανονισμούς αεροδρομίων, τα  runway-edge lighting πρέπει να είναι ορατά από 3 χιλιόμετρα και πάνω. Επιπλέον, ένα νέο σύστημα κατηγορίας advisory lighting (συμβουλευτικός φωτισμός) , το Runway Status Lights, δοκιμάζεται τώρα στις ΗΠΑ.




Έλεγχος των φώτων
 

Κανονικά τα φώτα ελέγχονατι από τον πύργο ελέγχου ή κάποια άλλη αρμόδια αρχή. Κάποια αεροδρόμια (κυρίως τα ιδιωτικά) επιτρέπουν στον πιλότο να ενεργοποιεί τα φώτα που χρειάζεται. Έτσι δεν είναι απαραίτητο προσωπικό ή αυτόματα συστήματα που ελέγχουν τα φώτα. Επιπλέον, έτσι μειώνεται το κόστος καθώς τα φώτα δεν μένουν αναμένα για μεγάλες χρονικές περιόδους. Μικρά αεροδρόμια που δέχονται μικρά αεροσκάφη, δεν έχουν καν φώτα.

Σημάνσεις στον διάδρομο

Όλοι οι διάδρομοι έχουν σημάνσεις. Οι μεγάλοι διάδρομοι έχουν μαύρες ταμπέλες με άσπρα νούμερα, για να δείξουν πόσος διάδρομος υπολείπεται. Αυτή η ταμπέλα έχει έναν αρισθμο για να δείξει τις χιλιάδες πόδια που υπολείπονται. Έτσι το 7 υποδεικνύει 7,000 ft (2,134 m) να υπολείπονται.

Υπάρχουν τρείς τύποι από διαδρόμους:

• Οι visual Runways, οι οποίοι βρίσκονται σε μικρά αεροδρόμια και συνήθως ειναι απλώς μια λωρίδα χόρτου, ασφάλτου, χώματος ή τσιμέντου. Παρόλο που δεν συνηθίζεται η σήμανση σε αυτό το είδος αεροδιαδρόμων, είναι πιθανό να έχουν οριστεί thresholds, designators και κεντρική γραμμή. Επιπλέον, δεν υποστιρίζεται προσγείωση βασισμένη σε όργανα, καθώς η μόνη δυνατή τεχνική προσγείωσης είναι προσγείωση εξ' όψεος. Ακόμη, η ραδιοεπικοινωνία είναι εξίσου πιθανό να μην είναι διαθέσιμη.
• Οι non-precision instrument runways βρίσκονται σε μικρά ή μετρίου μεγέθους αεροδρόμια. Αυτοί οι διάδρομοι, αναλόγως του υλικού που είναι κατασκευασμένοι, μπορεί να έχουν thresholds, designators, κεντρική γραμμή και μερικές φορές ένα σημάδι στα 305 μέτρα (γνωστό και ως 'στόχος' ή 'aiming point'). Ακόμη, αυτοί οι διάδρομοι παρέχουν στους πιλότους καθοδήγηση για την οριζόντια θέση τους σε προσγειώσεις βασισμένες σε όργανα, VOR, και συντεταγμένες με το Global Positioning System, κ.ά.
• Οι precision instrument runways, οι οποίοι βρίσκονατι σε μέτρια και μεγάλα αεροδρόμια, αποτελούνται από το blast pad/stopway (προεραιτικό για την διαχείριση jet), threshold, designator, κεντρική γραμμή, 'στόχο', και στα 152 μέτρα, στα 305 μέτρα, στα 457 μέτρα, στα 610 μέτρα, στα 762 μέτρα και στα 914 μέτρα σημάδια για τις διαθέσιμες ζόνες προσγείωσης. Αυτοί οι διάδρομοι παρέχουν οριζόντια και κάθετη καθοδήγηση στους πιλότους, όταν επιχειρούν προσγείωση βασισμένη σε όργανα.

Εθνικές διαφοροποιήσεις

• Στην Αυστραλία, Καναδά, Ιαπωνία, Αγγλία, όπως και σε άλλες χώρες, οι παράλληλες προς την κεντρική γραμμή, που βρίσκονται στην touchdown zone, και αποτελούνται από 2 ή 3γραμμές ανά πλευρά έχουν αντικατασταθεί από μια γραμμή ανα πλευρά..
• Οι διάδρομοι στην Νορβηγία έχουν κίτρινη σημανση αντί για λευκή, έτσι ώστε να έχει καλύτερο κόντραστ με το χιόνι.

Ασφάλεια στον διάδρομο

Παραβίαση του διαδρόμου υπάρχει όταν ένα αεροσκάφος φεύγει ή εισέρχεται στον διάδρομο χωρίς άδεια ή μη χρησιμοποιώντας τις προκαθορισμένες εξόδους. Αυτό μπορεί να συμβεί από λάθος του πιλότου, βλάβη του αεροσκάφους, λόγω κακού καιρού ή σε κάποια κρίσιμη κατάσταση.



Υπέρβαση του διαδρόμου είναι το είδος της παράβασης που συμβαίνει όταν ένα αεροσκάφος δεν μπορεί να σταματήσει και υπερβαίει τα όρια του διαδρόμου. Παράδειγμα τέτοιου περιστατικού είναι η πτήση της Air France Flight 358 το 2005.


Η Εισβολή στον διάδρομο  ορίζεται από την Ομοσπονδιακή Διοίκηση για την Αεροπορία των ΗΠΑ (FAA) ως: "Οτιδήποτε συμβαίνει όταν υπάρχει κάποιο αεροσκάφος, όχημα ή άνθρωπος σε περιοχή που έχει οριστεί για να χρησιμοποιείται για προσγείωση ή απογείωση αεροσκαφών, χωρις να έχει πάρει άδεια από τον πύργο ελέγχου."


Σύγχυση διαδρόμου ονομάζεται το γεγονός που σημβαίνει όταν ένα αεροσκάφος ακολουθεί λάθος διαδρομή κατά την διάρκεια της οδήγησής του στο έδαφος ή όταν αυτό βρίσκεται σε λάθος διάδρομο.


Η κατάσταση του διαδρόμου είναι μια σημαντική παράμετρος που σχετίζεται με τον καιρό.

• Στεγνός: η επιφάνεια του διαδρόμου δεν έχει νερό, χιόνι ή πάγο.
• Με υγρασία: το χρώμα της επιφάνειας του διαδρόμου αλλάζει λόγω της υγρασίας.
• Υγρός: ο διάδρομος είναι εμποτισμένος με νερό αλλά δεν υπάρχουν εμφανείς κηλίδες.
• Με κοιλώτητες νερού: λάκοι με στάσιμο νερό είναι εμφανείς
• Πλημιρισμένος: πάνω από το μισό του διαδρόμου είναι ολοκληρωτικά καλυμένο με νερό.

Σύμφωνα με τους διεθνής κανονισμούς όταν υπάρχουν εμφανή σημάδια νερού στον διάδρομο αυτός θεωρείται "μολυσμένος" και αεροσκάφη παύουν να επιχειρούν.

Κατασκευή

Η επιλογή του υλικού από το οποίο θα κατασκευαστεί ο διάδρομος εξαρτάται από τις εκάστοτε τοπογραφικές συνθήκες. Στα μεγάλα αεροδρόμια, όπου το έδαφος το επιτρέπει, χρησιμοιποιείται τσιμέντο, αφού δεν χρειάζεται ιδιαίτερη συντήρηση. Παρόλο που αρκετά αεροδρόμια χρησιμοποιούν ενισχυμένο σκυρόδεμα στους διαδρόμους, αυτό συνήθως δεν χρειάζεται, εκτός από τα σημεία που ενώνονται οι τσιμεντένιες πλάκες κατά το μήκος του διαδρόμου. Όπου το έδαφος είναι ασταθές και συμβαίνουν τακτικά καθιζήσεις, προτιμάται η τοποθέτηση ασφάλτου πάνω στις τσιμεντένιες πλάκες, καθώς είναι πιο εύκολη η επαναρμολόγηση των πλακών με άσφαλτο.  Για διαδρόμους που δέχονται μικρά αεροσκάφη μπορεί να χρησιμοποιηθεί χλωροτάπητας.
Για τον σχεδιασμό του οδοστρόματος, γίνονται γεωτρήσεις για να προσδιοριστεί η κατάσταση του υπεδάφους και με βάση αυτήν καθορίζονται οι προδιαγραφές. Για μεγάλα εμπορικά αεροσκάφη, το πάχος του οδοστρόματος κυμένεται μεταξύ 250 cm με 1 m.
Τα οδοστρόματα των αεροδρομίων σχεδιάζωνται με αρκετές μεθόδους. Η πρώτη είναι η μέθοδος Westergaard, η οποία βασίζεται στην υπόθεση πως το οδόστρομα είναι μια ελαστική βάση, η οποία υποστηρίζεται από μια βάση από υγρό με ενιαίο συντελεστή αντίδρασης, γνωστός και ως συντελεστής Κ. Από την εμπειρία τους οι κατασκευαστές κατάλαβαν πως ο συντελεστής Κ, όπου πάνω του είχε αναπτυχθεί όλη η μέθοδος, δεν μπορεί να εφαρμωστεί στα νέα αεροδρόμια που δέχονται αεροσκάφη με μεγάλη πίεση στο αποτύπωμά τους. 
Η δεύτερη μέθοδος ονομάζεται California bearing ratio και αναπτύχθηκε στα τέλη του 1940. Είναι μια προέκταση του αρχικού αποτελέσματος των δοκιμών, που δεν μπορούσε να εφαρμοστεί στα σύγχρονα οδοστρόματα των αεροδρομίων. Ορισμένα σχέδια έγιναν από τιν μίξη των δύο θεωριών.
Μια πιο πρόσφατη μέθοδος είναι το αναλυτικό σύστημα, το οποίο έχει ως καινοτόμο ιδέα την εισαγωγή της ανταπόκρισης των οχημάτων ως σημαντικό κριτήριο στον σχεδιασμό. Ουσιαστικά, λαμβάνει υπ'όψην όλους τους παράγοντες, συμπεριλαμβανομένων των καιρικών φαινομένων, την συντήριση που θα χρειάζεται ο διάδρομος, τα υλικά που θα χρειαστούν στην κατασκευή και την ιδιαιτέρως σημαντική παράμετρο που είναι η αντίδραση των αεροσκαφών στη  περιοχή προσγείωσης.
Εξ'αιτίας του υψηλού κόστους κατασκευής, γίνονται προσπάθειες για την μείωση των δυνάμεων που ασκούνται στον διάδρομο από τα αεροσκάφη. Οι κατασκευαστές των μεγάλων τζέτ, έχουν σχεδιάσει συστήματα προσγείωσης που κατανέμουν το βάρος του αεροσκάφους καλύτερα, με την τοποθέτηση περισσότερων και μεγαλύτερων τροχών. Έμφαση δίνεται επίσης και στα χαρακτηριστικά του συστήματος προσγείωσης, για να μειωθούν οι αντιδράσεις των δυνάμεων στον διάδρομο. Μερικές φορές, προκειμένου να ενισχυθεί το οδόστρομα και να αντέχει περισσότερο βάρος, τοποθετούμε επιπλέον στρώσεις από ασφαλτικό σκυρόδεμα το οποίο ενώνεται με την αρχική επίστρωση.
Ένας νέος τύπος σκυροδέματος αναπτύσεται για την επιφάνεια του διαδρόμου, ο οποίος επιτρέπει την χρήση λεπτότερων οδοστρομάτων, τα οποία έχουν μεγαλύτερο προσδόκιμο ζωής σε σχέση με το απλό σκυρόδεμα. Λόγω της ευαισθησίας των λεπτών οδοστρομάτων στην ταλάντωση που προκαλείται στην προσγείωση όταν το οδόστρομα έχει παγώσει, ενδίκνυται η τοποθέτησή τους σε περιοχές που δεν υπάρχουν συνήθη φαινόμενα παγώματος.

Επιφάνεια οδοστρώματος

Η επιφάνεια του διαδρόμου είναι ειδικά σχεδιασμένη έτσι ώστε να αντέχει και να μεγιστοποιεί την τριβή στο φρενάρισμα. Για την ελαχιστοποίηση της υδρολίσθησης μετά από δυνατή βροχή, η επιθάνεια του οδοστρόματος έχει αυλάκια έτσι ώστε η υδάτινη επικάλυψη να ρέει ανάμεσα αιχμές μεταξύ των αυλακιών, διατηρώντας τις αιχμές στεγνές για την επαφή τους με τα ελαστικά των αεροσκαφών.

Κωδικά ονόματα επιφανειών

Στους αεροναυτικούς χάρτες, η επιφάνειες είναι γρμμένες συντομογραφικά με έναν τριψήφιο κωδικό.
Οι πιο συνηθισμένες σκληρές επιφάνειες είναι η άσφαλτος και το σκυρόδεμα, ενώ οι πιο μαλακές είναι το γρασίδι και το χαλίκι.

• ASP: άσφαλτος
• BIT: άσφαλτος με Tarmac
• BRI: Τούβλα (δεν χρησιμοιποιούνται σήμερα, αντικαταστάθηαν από άσφαλτο ή σκυρόδεμα)
• CLA: πηλός
• COM: μικτός 
• CON: τσιμέντο
• COP: σύνθετος
• GRS: γρασίδι ή χώμα που δεν έχει ισοπεδοθεί 
• COR: κοράλι (σε κατασκευές πάνω σε υφάλους)
• GRE: γρασίδι ή χώμα ισοπεδομένα 
• GVL: χαλίκι
• LAT: λατερίτης
• ICE: πάγος
• MAC: χαλικόστρωμα
• PEM: εν μέρει τσιμέντο, άσφαλτος ή χαλικόστρωμα
• PER: Σκληρή μόνιμη επιφάνεια, άγνωστες λεπτομέριες
• PSP: Marsden Matting (Προέρχεται από διάτρητο χάλυβα)
• SAN: άμμος
• SNO: χιόνι
• U: άγνωστη επιφάνεια

Οι διάδρομοι προσγείωσης στην θάλασσα δεν έχουν κωδικό, αφού δεν είναι οριοθετημένοι.

Ενεργός διάδρομος

Ο ενεργός διάδρομος είναι αυτός που χρησιμοποιείται για απογείωση και προσγείωση. Αφού οι προσγειώσεις και οι απογειώσεις γίνονται συνήθως όσο πιο 'κοντά στον άνεμο', ο ενεργός διάδρομος καθορίζεται από την κατεύθυνση του ανέμου.
Η επιλογή του ενεργού διαδρόμου επιρρεάζεται από κάποιους παράγοντες. Στα αεροδρόμια χωρίς πύργο ελέγχου, ο πιλότος επιλέγει τον διάδρομο που είναι πιο καλά ευθυγραμμισμένος με τον αέρα, αλλά δεν είναι υποχρεωμένος να χρησιμοποιήσει αυτόν τον διάδρομο.
Στα ελεγχόμενα αεροδρόμια, ενεργός χαρακτηρίζεται ένας διάδρομος από τον υπεύθυνο του πύργου. Παρ'όλα αυτά, επεμβάσεις στις αποφάσεις του πύργου εναέριας κυκλοφορίας γίνονται από τον διευθυντή του αεροδρομίου, ο οποίος μπορεί να ορίσει ως ενεργό οποιονδήποτε διάδρομο, ασχέτως με την κατεύθυνση του ανέμου.
Στα μεγάλα αεροδρόμια με πολλούς διαδρόμους, ως ενεργοί μπορούν να οριστούν περισσότεροι από ένας διάδρομοι.
Στα διεθνή αεροδρόμια, ενεργός ορίζεται ένας διάδρομος με βάση τις καιρικές συνθήκες (ορατότητα, άνεμος, κατάσταση διαδρόμου π.χ. παγωμένος, βρεγμένος), την αποδωτικότητα (ποιός διάδρομος μπορεί να προσγειώνει πιο πολλά αεροσκάφη σε λιγότερο χρόνο), τις απαιτήσεις από τους πιλότους για την καλύτερη ακολουθεία του σχεδείου πτήσης τους και από την ώρα (στο αεροδρόμιο ORD ο διάδρομος  9R/27L χρησιμοποιείται μόνο μετά τις 6 πμ., εξ'αιτίας του θορύβου σε κατοικημένη περιοχή).
Στο αεροδρόμιο Heathrow του Λονδίνου, στο Ηνωμένο Βασίλειο, υπάρχουν δύο παράλληλοι διάδρομοι 09L/27R και 09R/27L. Αυτοί χρησιμοποιούνται σε 'εναλακτική', που σημαίνει πως ο ένας χρησιμοποιείται μόνο για αφίξεις και ο άλλος μόνο για αναχωρήσεις. Η συγκεκριμένη μέθοδος ορίζει πως στον ένα διάδρομο, που θα χρησιμοποιείται για προσγειώσεις, θα επιχειρούν αεροσκάφη από τις 06:00 ως τις 15:00 και μετά οι αφίξεις θα μεταφέρονται στον άλλον διάδρομο, από τις 15:00 ως την τελευταία άφιξη, όπου μετά από αυτήν τα αεροσκάφη που θα θέλουν να προσγειωθούν (από τις 01:00 ως τις 06:00) θα χρησιμοποιούν τον άλλον διάδρομο. Εν αντιθέση, τις Κυριακές ο διάδρομος που χρησιμοποιούνταν για προσγειώσεις πριν τα μεσάνυχτα, συνεχίζει να χρησιμοποιείται ως τις 06:00.

Μήκος διαδρόμου

Ένας διάδρομος με μήκος τουλάχιστον 6,000 ft (1,800 m) είναι συνήθως επαρκής για όλα τα αεροσκάφη με βάρος κάτω των 200,000 lb (90,000 kg). Μεγαλύτερα αεροσκάφη συνήθως χρειάζονται τουλάχιστον 8,000 ft (2,400 m) στο επίπεδο της θάλασσας και κάτι περισσότερο όσο ανεβαίνει το υψόμετρο του αεροδρομίου. Διεθνής πτήσεις που έχουν σημαντικές ποσότητες καυσίμου και γι'αυτό που αυξάνουν το βάρος τους, έχουν απαιτήσεις προσγείωσεις τα 10,000 ft (3,000 m) ή και περισσότερο και απαιτήσεις απογείωσης τα 13,000 ft (4,000 m).

Στο επίπεδο της θάλασσας, τα 10,000 ft (3,000 m) θεωρούνται επαρκές μήκος για προσγείωση εξ όψης για όλα τα αεροσκάφη.
Ένα αεροσκάφος θα χρειαστεί μεγαλύτερο διάδρομο οσο ανεβαίνει το υψόμετρο καθώς η πυκνώτητα του αέρα μειώνεται, γεγονός που μειώνει την ώθηση των μηχανών. Ένα αεροσκάφος θέλει μεγαλύτερο διάδρομο και σε πιο ζεστά ή με περισσότερη υγρασία κλίματα. Σχεδόν όλα τα αεροσκάφη έχουν κάρτες που δείχνουν τις μετατροπές που απαιτούνται για κάθε θερμοκρασία.

Runway [ΕΝ]

 

Helsinki-Vantaa Airport, runway 33

A runway (RWY) is a strip of land at an airport on which aircraft can take off and land and forms part of the maneuvering area. Runways may be a man-made surface (often asphalt, concrete, or a mixture of both) or a natural surface (grass, dirt, gravel, ice, or salt).
By extension, the term has also come to mean any long, flat, straight area, such as that used in fashion shows.

Orientation and dimensions

Runways are named by a number between 01 and 36, which is generally one tenth of the magnetic azimuth of the runway's heading: a runway numbered 09 points east (90°), runway 18 is south (180°), runway 27 points west (270°) and runway 36 points to the north (360° rather than 0°). However, runways in North America that lie within the Northern Domestic Airspace are numbered relative to true north because proximity to the magnetic North Pole makes the magnetic declination large. A runway can normally be used in both directions, and is named for each direction separately: e.g., "runway 33" in one direction is "runway 15" when used in the other. The two numbers always differ by 18 (= 180°).

El Dorado International Airport, Runway 31R/13L

If there is more than one runway pointing in the same direction (parallel runways), each runway is identified by appending Left (L), Center (C) and Right (R) to the number — for example, Runways One Five Left (15L), One Five Center (15C), and One Five Right (15R). Runway Zero Three Left (03L) becomes Runway Two One Right (21R) when used in the opposite direction (derived from adding 18 to the original number for the 180 degrees when approaching from the opposite direction).
At large airports with more than three parallel runways (for example, at Los Angeles, Detroit Metropolitan Wayne County, Hartsfield-Jackson Atlanta, Denver, and Dallas-Fort Worth), some runway identifiers are shifted by 10 degrees to avoid the ambiguity that would result with more than three parallel runways. For example, in Los Angeles, this system results in Runways 6L, 6R, 7L, and 7R, even though all four runways are exactly parallel (approximately 69 degrees). At Dallas-Fort Worth, there are five parallel runways, named 17L, 17C, 17R, 18L, and 18R, all oriented at a heading of 175.4 degrees.
For clarity in radio communications, each digit in the runway name is pronounced individually: runway three six, runway one four, etc. A leading zero, for example in "runway zero six" or "runway zero one left", is included for International Civil Aviation Organization (ICAO) and some United States military airports (such as Edwards Air Force Base). However in the United States at most civil aviation airports, the leading zero is often dropped. This also includes some military airfields such as Cairns Army Airfield. This American anomaly may lead to inconsistencies in conversations between American pilots and controllers in other countries. It is very common in a country such as Canada for a controller to clear an incoming American aircraft to, for example, Runway 04, and the pilot read back the clearance as Runway 4. In flight simulation programs those of American origin might apply U.S. usage to airports around the world. For example Runway 05 at Halifax will appear on the program as the single digit 5 rather than 05.

Runway designations change over time because the magnetic poles slowly drift on the Earth's surface and the magnetic bearing will change. Depending on the airport location and how much drift takes place, it may be necessary over time to change the runway designation. As runways are designated with headings rounded to the nearest 10 degrees, this will affect some runways more than others. For example, if the magnetic heading of a runway is 233 degrees, it would be designated Runway 23. If the magnetic heading changed downwards by 5 degrees to 228, the Runway would still be Runway 23. If on the other hand the original magnetic heading was 226 (Runway 23), and the heading decreased by only 2 degrees to 224, the runway should become Runway 22. Because the drift itself is quite slow, runway designation changes are uncommon, and not welcomed, as they require an accompanying change in aeronautical charts and descriptive documents. When runway designations do change, especially at major airports, it is often changed overnight as taxiway signs need to be changed and the huge numbers at each end of the runway need to be repainted to the new runway designators. In July 2009 for example, London Stansted Airport in the United Kingdom changed its runway designations from 05/23 to 04/22 overnight.

For fixed-wing aircraft it is advantageous to perform take-offs and landings into the wind to reduce takeoff roll and reduce the ground speed needed to attain flying speed. Larger airports usually have several runways in different directions, so that one can be selected that is most nearly aligned with the wind. Airports with one runway are often constructed to be aligned with the prevailing wind.
Runway dimensions vary from as small as 245 m (804 ft) long and 8 m (26 ft) wide in smaller general aviation airports, to 5,500 m (18,045 ft) long and 80 m (262 ft) wide at large international airports built to accommodate the largest jets, to the huge 11,917 m (39,098 ft) x 274 m (899 ft) lake bed runway 17/35 at Edwards Air Force Base in California - a landing site for the Space Shuttle.

Placement and grouping

Two runways pointing in the same direction are classed as dual or parallel runways depending on the separation distance. In some countries, flight rules mandate that only one runway may be used at a time under certain conditions (usually adverse weather) if the parallel runways are too close to each other.

Declared distances

TORA

Takeoff Run Available - The length of runway declared available and suitable for the ground run of an airplane taking off.

TODA

Takeoff Distance Available - The length of the takeoff run available plus the length of the clearway, if clearway is provided.

(The clearway length allowed must lie within the aerodrome or airport boundary. According to the Federal Aviation Regulations and Joint Aviation Requirements (JAR) TODA is the lesser of TORA plus clearway or 1.5 times TORA).

ASDA

Accelerate-Stop Distance Available - The length of the takeoff run available plus the length of the stopway, if stopway is provided.

LDA

Landing Distance Available - The length of runway which is declared available and suitable for the ground run of an airplane landing.

EDA

Emergency Distance Available - LDA (or TORA) plus a stopway.

Sections of a runway

• The Runway Safety Area is the cleared, smoothed and graded area around the paved runway. It is kept free from any obstacles that might impede flight or ground roll of aircraft.
• The Runway is the surface from threshold to threshold, which typically features threshold markings, numbers, centerlines, but not overrun areas at both ends.
• Blast pads, also known as overrun areas or stopways, are often constructed just before the start of a runway where jet blast produced by large planes during the takeoff roll could otherwise erode the ground and eventually damage the runway. Overrun areas are also constructed at the end of runways as emergency space to slowly stop planes that overrun the runway on a landing gone wrong, or to slowly stop a plane on a rejected takeoff or a take-off gone wrong. Blast pads are often not as strong as the main paved surface of the runway and are marked with yellow chevrons. Planes are not allowed to taxi, take-off or land on blast pads, except in an emergency.

• Displaced thresholds may be used for taxiing, takeoff, and landing rollout, but not for touchdown. A displaced threshold often exists because obstacles just before the runway, runway strength, or noise restrictions may make the beginning section of runway unsuitable for landings. It is marked with white paint arrows that lead up to the beginning of the landing portion of the runway.

Runway lighting

History

The first runway lighting appeared in 1930 at Cleveland Municipal Airport (now known as Cleveland Hopkins International Airport) in Cleveland, Ohio. A line of lights on an airfield or elsewhere to guide aircraft in taking off or coming in to land or an illuminated runway is sometimes also known as a flare path.

Technical specifications

Runway lighting is used at airports which allow night landings. Seen from the air, runway lights form an outline of the runway. A particular runway may have some or all of the following.

• Runway End Identification Lights (REIL) – unidirectional (facing approach direction) or omnidirectional pair of synchronized flashing lights installed at the runway threshold, one on each side.

• Runway end lights – a pair of four lights on each side of the runway on precision instrument runways, these lights extend along the full width of the runway. These lights show green when viewed by approaching aircraft and red when seen from the runway.

• Runway edge lights – white elevated lights that run the length of the runway on either side. On precision instrument runways, the edge-lighting becomes yellow in the last 2,000 ft (610 m) of the runway. Taxiways are differentiated by being bordered by blue lights, or by having green centre lights, depending on the width of the taxiway, and the complexity of the taxi pattern.

• Runway Centerline Lighting System (RCLS) – lights embedded into the surface of the runway at 50 ft (15 m) intervals along the runway centerline on some precision instrument runways. White except the last 3,000 ft (914 m), alternate white and red for next 2,000 ft (610 m) and red for last 1,000 ft (305 m).

• Touchdown Zone Lights (TDZL) – rows of white light bars (with three in each row) on either side of the centerline over the first 3,000 ft (914 m) (or to the midpoint, whichever is less) of the runway.

• Taxiway Centerline Lead-Off Lights – installed along lead-off markings, alternate green and yellow lights embedded into the runway pavement. It starts with green light about runway centerline to the position of first centerline light beyond holding position on taxiway.

• Taxiway Centerline Lead-On Lights – installed the same way as taxiway centerline lead-off Lights.

• Land and Hold Short Lights – a row of white pulsating lights installed across the runway to indicate hold short position on some runways which are facilitating land and hold short operations (LAHSO).

• Approach Lighting System (ALS) – a lighting system installed on the approach end of an airport runway and consists of a series of lightbars, strobe lights, or a combination of the two that extends outward from the runway end.

According to Transport Canada's regulations, the runway-edge lighting must be visible for at least 2 mi (3 km). Additionally, a new system of advisory lighting, Runway Status Lights, is currently being tested in the United States.
The edge lights must be arranged such that:

• the minimum distance between lines is 75 ft (23 m), and maximum is 200 ft (61 m);
• the maximum distance between lights within each line is 200 ft (61 m);
• the minimum length of parallel lines is 1,400 ft (427 m);
• the minimum number of lights in the line is 8.

Control of Lighting System Typically the lights are controlled by a control tower, a Flight Service Station or another designated authority. Some airports/airfields (particularly uncontrolled ones) are equipped with Pilot Controlled Lighting, so that pilots can temporarily turn on the lights when the relevant authority is not available. This avoids the need for automatic systems or staff to turn the lights on at night or in other low visibility situations. This also avoids the cost of having the lighting system on for extended periods. Smaller airports may not have lighted runways or runway markings. Particularly at private airfields for light planes, there may be nothing more than a windsock beside a landing strip.

Runway markings

There are runway markings and signs on any runway. Larger runways have a distance remaining sign (black box with white numbers). This sign uses a single number to indicate the thousands of feet remaining, so 7 will indicate 7,000 ft (2,134 m) remaining. The runway threshold is marked by a line of green lights.

There are three types of runways:

• visual Runways are used at small airstrips and are usually just a strip of grass, gravel, asphalt or concrete. Although there are usually no markings on a visual runway, they may have threshold markings, designators, and centerlines. Additionally, they do not provide an instrument-based landing procedure; pilots must be able to see the runway to use it. Also, radio communication may not be available and pilots must be self-reliant.
• non-precision instrument runways are often used at small- to medium-size airports. These runways, depending on the surface, may be marked with threshold markings, designators, centerlines, and sometimes a 1,000 ft (305 m) mark (known as an aiming point, sometimes installed at 1,500 ft (457 m)). They provide horizontal position guidance to planes on instrument approach via Non-directional beacon (NDB), VHF omnidirectional range (VOR), Global Positioning System, etc.
• precision instrument runways, which are found at medium- and large-size airports, consist of a blast pad/stopway (optional, for airports handling jets), threshold, designator, centerline, aiming point, and 500 ft (152 m), 1,000 ft (305 m)/1,500 ft (457 m), 2,000 ft (610 m), 2,500 ft (762 m), and 3,000 ft (914 m) touchdown zone marks. Precision runways provide both horizontal and vertical guidance for instrument approaches.

National variants

• In Australia, Canada, Japan, the United Kingdom, as well as some other countries all 3-stripe and 2-stripe touchdown zones for precision runways are replaced with one-stripe touchdown zones.
• In Australia, precision runways consist of only an aiming point and one 1-stripe touchdown zone. Furthermore, many non-precision and visual runways lack an aiming point.
• In some Latin American countries like Colombia, Ecuador and Peru one 3-stripe is added and a 2-stripe is replaced with the aiming point .
• Some European countries replace the aiming point with a 3-stripe touchdown zone.
• Runways in Norway have yellow markings instead of the usual white ones. This also occurs on some airports in Japan. The yellow markings are used to ensure better contrast against snow.
• Runways may have different types on each end. To cut costs, many airports do not install precision guidance equipment on both ends. Runways with one precision end and any other type of end can install the full set of touchdown zones, even if some are past the midpoint. If a runway has precision markings on both ends, touchdown zones within 900 ft (274 m) of the midpoint are omitted, to avoid pilot confusion over which end the marking belongs to.

Runway safety

Runway excursion is an incident involving only a single aircraft where it makes an inappropriate exit from the runway. This can happen because of pilot error, poor weather, emergency, or a fault with the aircraft. Overrun is a type of excursion where the aircraft is unable to stop before the end of the runway. An example of such an event is Air France Flight 358 in 2005. Further examples can be found in the overruns category. Runway excursion is the most frequent type of landing accident, slightly ahead of runway incursion. For runway accidents recorded between 1995 and 2007, 96% were of the 'excursion' type.
Runway event is another term for a runway accident.
Runway incursion involves a first aircraft, as well as a second aircraft, vehicle, or person. It is defined by the U.S. Federal Aviation Administration (FAA) as: "Any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and take off of aircraft."
Runway confusion involves a single aircraft, and is used to describe the error when the aircraft makes "the unintentional use of the wrong runway, or a taxiway, for landing or take-off".
The U.S. FAA publishes an annual report on runway safety issues, available from the FAA website. New systems designed to improve runway safety, such as Airport Movement Area Safety System (AMASS) and Runway Awareness and Advisory System (RAAS), are discussed in the report. AMASS prevented the serious near-collision in the 2007 San Francisco International Airport runway incursion.
Runway condition is also an important parameter related to meteorological conditions and air safety.

• Dry: the surface of the runway is clear of water, snow or ice.
• Damp: change of color on the surface due to moisture.
• Wet: the surface of the runway is soaked but there is no significant patches of standing water.
• Water patches: patches of standing water are visible.
• Flooded: there is extensive standing water.

According to the JAR definition, a runway with water patches or that is flooded is considered to be contaminated.

Pavement

The choice of material used to construct the runway depends on the use and the local ground conditions. For a major airport, where the ground conditions permit, the most satisfactory type of pavement for long-term minimum maintenance is concrete. Although certain airports have used reinforcement in concrete pavements, this is generally found to be unnecessary, with the exception of expansion joints across the runway where a dowel assembly, which permits relative movement of the concrete slabs, is placed in the concrete. Where it can be anticipated that major settlements of the runway will occur over the years because of unstable ground conditions, it is preferable to install asphaltic concrete surface, as it is easier to patch on a periodic basis. For fields with very low traffic of light planes, it is possible to use a sod surface. Some runways also make use of salt flat runways.
For pavement designs, borings are taken to determine the subgrade condition, and based on the relative bearing capacity of the subgrade, the specifications are established. For heavy-duty commercial aircraft, the pavement thickness, no matter what the top surface, varies from 10 in (250 mm) to 4 ft (1 m), including subgrade.
Airport pavements have been designed by two methods. The first, Westergaard, is based on the assumption that the pavement is an elastic plate supported on a heavy fluid base with a uniform reaction coefficient known as the K value. Experience has shown that the K values on which the formula was developed are not applicable for newer aircraft with very large footprint pressures.
The second method is called the California bearing ratio and was developed in the late 1940s. It is an extrapolation of the original test results, which are not applicable to modern aircraft pavements or to modern aircraft landing gear. Some designs were made by a mixture of these two design theories.
A more recent method is an analytical system based on the introduction of vehicle response as an important design parameter. Essentially it takes into account all factors, including the traffic conditions, service life, materials used in the construction, and, especially important, the dynamic response of the vehicles using the landing area.
Because airport pavement construction is so expensive, every effort is made to minimize the stresses imparted to the pavement by aircraft. Manufacturers of the larger planes design landing gear so that the weight of the plane is supported on larger and more numerous tires. Attention is also paid to the characteristics of the landing gear itself, so that adverse effects on the pavement are minimized. Sometimes it is possible to reinforce a pavement for higher loading by applying an overlay of asphaltic concrete or portland cement concrete that is bonded to the original slab.
Post-tensioning concrete has been developed for the runway surface. This permits the use of thinner pavements and should result in longer concrete pavement life. Because of the susceptibility of thinner pavements to frost heave, this process is generally applicable only where there is no appreciable frost action.

Pavement surface

Runway pavement surface is prepared and maintained to maximize friction for wheel braking. To minimize hydroplaning following heavy rain, the pavement surface is usually grooved so that the surface water film flows into the grooves and the peaks between grooves will still be in contact with the aircraft tires. To maintain the macrotexturing built into the runway by the grooves, maintenance crews engage in airfield rubber removal or hydrocleaning in order to meet required FAA friction levels.

Surface Type Codes

In aviation charts, the surface type is usually abbreviated to a three-letter code.
The most common hard surface types are Asphalt and Concrete. The most common soft surface types are Grass and Gravel.

• ASP: Asphalt
• BIT: Bitumenous Asphalt or Tarmac
• BRI: Bricks (no longer in use, covered with Asphalt or Concrete now)
• CLA: Clay
• COM: Composite
• CON: Concrete
• COP: Composite
• GRS: Grass or earth not graded or rolled
• COR: Coral (Coral reef structures)
• GRE: Graded or rolled earth, Grass on graded earth
• GVL: Gravel
• LAT: Laterite
• ICE: Ice
• MAC: Macadam
• PEM: Partially Concrete, Asphalt or Bitumen-bound Macadam
• PER: Permanent Surface, Details unknown
• PSP: Marsden Matting (Derived from Pierced/Perforated Steel Planking)
• SAN: Sand
• SNO: Snow
• U: Unknown surface

Water runways do not have a type code as they dont have physical markings, and are thus not registered as specific runways.

Active runway

The active runway is the runway at an airport that is in use for takeoffs and landings. Since takeoffs and landings are usually done as close to "into the wind" as possible, wind direction generally determines the active runway (or just the active in aviation vernacular).
Selection of the active runway, however, depends on a number of factors. At a non-towered airport, pilots usually select the runway most nearly aligned with the wind, but they are not obliged to use that particular runway. For example, a pilot arriving from the east may elect to land straight in to an east-west runway despite a minor tailwind or significant crosswind, in order to expedite his arrival, although it is recommended to always fly a regular traffic pattern to more safely merge with other aircraft.
At controlled airports, the active is usually determined by a tower supervisor. However, there may be constraints, such as policy from the airport manager (calm wind runway selection, for example, or noise abatement guidelines) that dictate an active runway selection that is not the one most nearly aligned with the wind.
At major airports with multiple runways, the active could be any of a number of runways. For example, when O'Hare (ORD) is landing on 27L and 32L, departures use 28 and 32R, thus making four active runways. When they are landing on 14R and 22R, departures use 22L and 9R, and occasionally a third arrival runway, 14L, will be employed, bringing the active runway count to five.
At major airports, the active runway is based on weather conditions (visibility and ceiling, as well as wind, and runway conditions such as wet/dry or snow covered), efficiency (ORD can land more aircraft on 14R/32L than they can on 9R/27L), traffic demand (when a heavy departure rush is scheduled, a runway configuration that optimizes departures vs arrivals may be desirable), and time of day (ORD is obliged to use runway 9R/27L during the hours of roughly midnight to 6 a.m. due to noise abatement).
London Heathrow Airport in the United Kingdom has two runways which are parallel to each other, they are designated 09L/27R and 09R/27L. They are used in segregated alternate mode which means one runway is used only for arrivals and the other is only used for departures. The present pattern provides for one runway to be used by landing aircraft from 06:00 until 15:00 and then arrivals will switch to the other runway from 15:00 until after the last departure, after which landing aircraft use the first runway again until 06:00. However, on Sunday each week the runway used before midnight continues to be used for landings until 06:00. This means early morning arrivals before 06:00 use a different runway on successive weeks and that the runways used by landing aircraft before and after 15:00 also alternate on a weekly basis. This only applies to westerly operations as landing aircraft always use runway 09L.

Runway length

A runway of at least 6,000 ft (1,800 m) in length is usually adequate for aircraft weights below approximately 200,000 lb (90,000 kg). Larger aircraft including widebodies will usually require at least 8,000 ft (2,400 m) at sea level and somewhat more at higher altitude airports. International widebody flights, which carry substantial amounts of fuel and are therefore heavier, may also have landing requirements of 10,000 ft (3,000 m) or more and takeoff requirements of 13,000 ft (4,000 m).

At sea level, 10,000 ft (3,000 m) can be considered an adequate length to land virtually any aircraft. For example, at O'Hare International, when landing simultaneously on 22R and 28 or parallel 27L, it is routine for arrivals from the Far East which would normally be vectored for 22R (7,500 ft (2,286 m)) or 27L (7,967 ft (2,428 m)) to request 28 (13,001 ft (3,963 m)). It is always accommodated, although occasionally with a delay. Another example is that the Luleå Airport in Sweden was extended to 10,990 ft (3,350 m) to allow any fully loaded freight aircraft to take off.
An aircraft will need a longer runway at a higher altitude due to decreased density of air at higher altitudes, which reduces lift and engine power. An aircraft will also require a longer runway in hotter or more humid conditions. Most commercial aircraft carry manufacturer's tables showing the adjustments required for a given temperature.

Air safety [EN]

Navigation aids and instrument flight


One of the first navigation aids to be introduced (in the USA in the late 1920s) was airfield lighting to assist pilots to make landings in poor weather or after dark. The Precision Approach Path Indicator was developed from this in the 1930s, indicating to the pilot the angle of descent to the airfield. This later became adopted internationally through the standards of the International Civil Aviation Organization (ICAO).
In 1929 Jimmy Doolittle developed instrument flight.
With the spread of radio technology, several experimental radio based navigation aids were developed from the late 1920s onwards. These were most successfully used in conjunction with instruments in the cockpit in the form of Instrument landing systems (ILS), first used by a scheduled flight to make a landing in a snowstorm at Pittsburgh in 1938. A form of ILS was adopted by the ICAO for international use in 1949.
Following the development of radar in World War II, it was deployed as a landing aid for civil aviation in the form of Ground-controlled approach (GCA) systems, joined in 1948 by distance measuring equipment (DME), and in the 1950s by airport surveillance radar as an aid to air traffic control. VHF omnidirectional range (VOR) stations became the predominate means of route navigation during the 1960s, superseding the low frequency radio ranges and the Non-directional beacon (NDB). The ground based VOR stations were often co-located with DME transmitters and then labeled as VOR-DME stations on navigation charts. VORTAC stations, which combined VOR and TACAN features (military TACtical Air Navigation) — the latter including both a DME distance feature and a separate TACAN azimuth feature, which provides military pilots data similar to the civilian VOR, were also used in that new system. With the proper receiving equipment in the aircraft, pilots could know their radials in degrees to/from the VOR station, as well as the slant range distance to/from, if the station was co-located with DME or TACAN.
All of the ground-based navigation aids are being supplemented by satellite-based aids like Global Positioning System (GPS), which make it possible for aircrews to know their position with great precision anywhere in the world. With the arrival of Wide Area Augmentation System (WAAS), GPS navigation has become accurate enough for vertical (altitude) as well as horizontal use, and is being used increasingly for instrument approaches as well as en-route navigation. However, since the GPS constellation is a single point of failure that can be switched off by the U.S. military in time of crisis, onboard Inertial Navigation System (INS) or ground-based navigation aids are still required for backup.

Air safety topics

Misinformation and lack of information

Herzliya Airport (Israel) Runway location and airfield traffic pattern chart (left) was erroneously printed as a result of "black layer" 180° misplacement. The corrected chart is on the right.

A pilot might fly the plane in an accident-prone manner when misinformed by a printed document (manual, map etc.), by reacting to a faulty instrument or indicator (either in cockpit or on ground) or by following inaccurate instructions or information from flight or ground control. Lack of information by the control tower, or delayed instructions, are major factors contributing to accidents.

Lightning

Boeing studies have shown that airliners are struck by lightning on average of twice per year. While the "flash and bang" is startling to the passengers and crew, aircraft are able to withstand normal lightning strikes.
The dangers of more powerful positive lightning were not understood until the destruction of a glider in 1999. It has since been suggested that positive lightning may have caused the crash of Pan Am Flight 214 in 1963. At that time aircraft were not designed to withstand such strikes, since their existence was unknown at the time standards were set. The 1985 standard in force at the time of the glider crash, Advisory Circular AC 20-53A, was replaced by Advisory Circular AC 20-53B in 2006, however it is unclear whether adequate protection against positive lighting was incorporated.
The effects of normal lightning on traditional metal-covered aircraft are well understood and serious damage from a lightning strike on an airplane is rare. However, as more and more aircraft, like the upcoming Boeing 787, whose whole exterior is made of non-conducting composite materials take to the skies, additional design effort and testing must be made before certification authorities will permit these aircraft in commercial service.

Ice and snow

Snowy and icy conditions are frequent contributors to airline accidents. The December 8, 2005 accident where Southwest Airlines Flight 1248 slid off the end of the runway in heavy snow conditions is just one of many examples. Just as on a road, ice and snow buildup can make braking and steering difficult or impossible.
The icing of wings is another problem and measures have been developed to combat it. Even a small amount of ice or coarse frost can greatly decrease the ability of a wing to develop lift. This could prevent an aircraft from taking off. If ice builds up during flight the result can be catastrophic as evidenced by the crash of American Eagle Flight 4184 (an ATR 72 aircraft) near Roselawn, Indiana on October 31, 1994, killing 68, or Air Florida Flight 90.
Airlines and airports ensure that aircraft are properly de-iced before takeoff whenever the weather threatens to create icing conditions. Modern airliners are designed to prevent ice buildup on wings, engines, and tails (empennage) by either routing heated air from jet engines through the leading edges of the wing, tail, and inlets, or on slower aircraft, by use of inflatable rubber "boots" that expand and break off any accumulated ice.
Finally, airline dispatch offices keep watch on weather along the routes of their flights, helping the pilots avoid the worst of inflight icing conditions. Pilots can also be equipped with an ice detector in order to leave icy areas they have flown into.

Engine failure

Although aircraft are now designed to fly even after the failure of one or more aircraft engines, the failure of the second engine on one side for example is obviously serious. Losing all engine power is even more serious, as illustrated by the 1970 Dominicana DC-9 air disaster, when fuel contamination caused the failure of both engines. To have an emergency landing site is then very important.
In the 1983 Gimli Glider incident, an Air Canada flight suffered fuel exhaustion during cruise flight, forcing the pilot to glide the plane to an emergency deadstick landing. The automatic deployment of the ram air turbine maintained the necessary hydraulic pressure to the flight controls, so that the pilot was able to land with only a minimal amount of damage to the plane, and minor (evacuation) injuries to a few passengers.
The ultimate form of engine failure, physical separation, occurred in 1979 when a complete engine detached from American Airlines Flight 191, causing damage to the aircraft and loss of control.

Metal fatigue

Metal fatigue has caused failure either of the engine or of the aircraft body.
Examples:

• the January 8, 1989 Kegworth air disaster
• De Havilland Comets incidents in 1953 and 1954
• Aloha Airlines Flight 243 in 1988

Now that the subject is better understood, rigorous inspection and nondestructive testing procedures are in place.

Delamination

Composite materials consist of layers of fibers embedded in a resin matrix. In some cases, especially when subjected to cyclic stress, the fibers may tear off the matrix, the layers of the material then separate from each other - a process called delamination, and form a mica-like structure which then falls apart. As the failure develops inside the material, nothing is shown on the surface; instrument methods (often ultrasound-based) have to be used to detect such a material failure.
Aircraft have developed delamination problems, but most were discovered before they caused a catastrophic failure. Delamination risk is as old as composite material. Even in the 1940s, several Yakovlev Yak-9s experienced delamination of plywood in their construction.

Stalling

Stalling an aircraft (increasing the angle of attack to a point at which the wings fail to produce enough lift), can be dangerous and can result in a crash unless the pilot reacts in the proper manner. Upon entering a stall, the pilot will need an adequate altitude buffer to regain control, reduce the angle of attack to a point where the boundary layer reattaches to the wing, and airspeed is brought up to where level flight can resume. Stalls are most dangerous at low altitudes, which occur during takeoff and landing.
Devices have been developed to warn the pilot when the plane's speed is coming close to the stall speed. These include stall warning horns (now standard on virtually all powered aircraft), stick shakers and voice warnings. Most stalls are a result of the pilot allowing the plane to go too slow for the particular weight and configuration at the time. However, because flow separation (stall) is purely a function of angle of attack, most aircraft can be pushed hard enough to cause a stall even at high speeds (those that can't simply lack the control authority to change the angle of attack enough at speed to induce a stall).


Notable crashes, caused by a full stall of the airfoils:

• British European Airways Flight 548, June 18, 1972
• United Airlines Flight 553, December 8, 1972
• Aeroflot Flight 7425, July 10, 1985
• Arrow Air Flight 1285, December 12, 1985
• Northwest Airlines Flight 255, August 16, 1987
• Delta Air Lines Flight 1141, August 31, 1988
• The Paul Wellstone King Air Charter crash, October 25, 2002
• Colgan Air Flight 3407, February 12, 2009
• Turkish Airlines Flight 1951, February 25, 2009

Fire

Safety regulations control aircraft materials and the requirements for automated fire safety systems. Usually these requirements take the form of required tests. The tests measure flammability and the toxicity of smoke. When the tests fail, they fail on a prototype in an engineering laboratory, rather than in an aircraft.
Fire on board the aircraft, and more especially the toxic smoke generated, have been the cause of accidents. An electrical fire on Air Canada Flight 797 in 1983 caused the deaths of 23 of the 46 passengers, resulting in the introduction of floor level lighting to assist people to evacuate a smoke-filled aircraft. Two years later a fire on the runway caused the loss of 55 lives, 48 from the effects of incapacitating and subsequently lethal toxic gas and smoke, in the 1985 British Airtours Flight 28M. That accident raised serious concerns relating to survivability, something that prior to 1985 had not been studied in such detail. The swift incursion of the fire into the fuselage and the layout of the aircraft impaired passengers' ability to evacuate, with areas such as the forward galley area becoming a bottle-neck for escaping passengers, with some dying very close to the exits. A large amount of research into evacuation and cabin and seating layouts was carried at Cranfield Institute to try to measure what makes a good evacuation route, which led to the seat layout by Overwing exits being changed by mandate and the examination of evacuation requirements relating to the design of galley areas. The use of smoke hoods or misting systems were also examined although both were rejected.
The cargo holds of most airliners are equipped with "fire bottles" (essentially remote-controlled fire extinguishers) to combat a fire that might occur in the baggage holds, below the passenger cabin. In May 1996 ValuJet Airlines Flight 592 crashed into the Florida Everglades a few minutes after takeoff after a fire broke out in the forward cargo hold. All 110 aboard were killed.
At one time fire fighting foam paths were laid down before an emergency landing, but the practice was considered only marginally effective, and concerns about the depletion of fire fighting capability due to pre-foaming led the United States FAA to withdraw its recommendation in 1987.

Bird strike

Bird strike is an aviation term for a collision between a bird and an aircraft. It is a common threat to aircraft safety and has caused a number of fatal accidents. In 1988 an Ethiopian Airlines Boeing 737 sucked pigeons into both engines during take-off and then crashed in an attempt to return to the Bahir Dar airport; of the 104 people aboard, 35 died and 21 were injured. In another incident in 1995, a Dassault Falcon 20 crashed at a Paris airport during an emergency landing attempt after sucking lapwings into an engine, which caused an engine failure and a fire in the airplane fuselage; all 10 people on board were killed. Canada Geese were ingested into the engines of US Airways 1549 causing the engines to fail on the Airbus A320 that crash landed onto the Hudson River.
Modern jet engines have the capability of surviving an ingestion of a bird. Small fast planes, such as military jet fighters, are at higher risk than heavy multi-engine ones. This is due to the fact that the fan of a high-bypass turbofan engine, typical on transport aircraft, acts as a centrifugal separator to force ingested materials (birds, ice, etc.) to the outside of the fan's disc. As a result, such materials go through the relatively unobstructed bypass duct, rather than through the core of the engine, which contains the smaller and more delicate compressor blades. Military aircraft designed for high-speed flight typically have pure turbojet, or low-bypass turbofan engines, increasing the risk that ingested materials will get into the core of the engine to cause damage.
The highest risk of the bird strike is during the takeoff and landing, in low altitudes, which is in the vicinity of the airports. Some airports use active countermeasures, ranging from a person with a shotgun through recorded sounds of predators to employing falconers. Poisonous grass can be planted that is not palatable to birds, nor to insects that attract insectivorous birds. Passive countermeasures involve sensible land-use management, avoiding conditions attracting flocks of birds to the area (e.g. landfills). Another tactic found effective is to let the grass at the airfield grow taller (approximately 12 inches (30 centimetres)) as some species of birds won't land if they cannot see one another.
Bird strike can also break windshields and wound the pilot.

Ground damage

Aircraft are occasionally damaged by ground equipment at the airport. In the act of servicing the aircraft between flights a great deal of ground equipment must operate in close proximity to the fuselage and wings. Occasionally the aircraft gets bumped or worse.
Damage may be in the form of simple scratches in the paint or small dents in the skin. However, because aircraft structures (including the outer skin) play such a critical role in the safe operation of a flight, all damage is inspected, measured and possibly tested to ensure that any damage is within safe tolerances. A dent that may look no worse than common "parking lot damage" to an automobile can be serious enough to ground an airplane until a repair can be made.
An example of the seriousness of this problem was the December 26, 2005 depressurization incident on Alaska Airlines flight 536. During ground services a baggage handler hit the side of the aircraft with a tug towing a train of baggage carts. This damaged the metal skin of the aircraft. This damage was not reported and the plane departed. Climbing through 26,000 feet (7,900 metres) the damaged section of the skin gave way due to the growing difference in pressure between the inside of the aircraft and the outside air. The cabin depressurized with a bang, frightening all aboard and necessitating a rapid descent back to denser (breathable) air and an emergency landing. Post landing examination of the fuselage revealed a 12 in × 6 in (30 cm × 15 cm) hole between the middle and forward cargo doors on the right side of the airplane.
The three pieces of ground equipment that most frequently damage aircraft are the passenger boarding bridge, catering trucks, and cargo "beltloaders." However, any other equipment found on an airport ramp can damage an aircraft through careless use, high winds, mechanical failure, and so on.
The generic industry colloquial term for this damage is "ramp rash", or "hangar rash".

Volcanic ash

Plumes of volcanic ash near active volcanoes present a risk especially for night flights. The ash is hard and abrasive and can quickly cause significant wear on the propellers and turbocompressor blades, and scratch the cockpit windows, impairing visibility. It contaminates fuel and water systems, can jam gears, and can cause a flameout of the engines. Its particles have low melting point, so they melt in the combustion chamber and the ceramic mass then sticks on the turbine blades, fuel nozzles, and the combustors, which can lead to a total engine failure. It can get inside the cabin and contaminate everything there, and can damage the airplane electronics.
There are many instances of damage to jet aircraft from ash encounters. In one of them in 1982, British Airways Flight 9 flew through an ash cloud, lost all four engines, and descended from 36,000 ft (11,000 m) to only 12,000 ft (3,700 m) before the flight crew managed to restart the engines. A similar incident occurred on December 15, 1989 involving KLM Flight 867.
With the growing density of air traffic, encounters like this are becoming more common. In 1991 the aviation industry decided to set up Volcanic Ash Advisory Centers (VAACs), one for each of 9 regions of the world, acting as liaisons between meteorologists, volcanologists, and the aviation industry.
Prior to the European air travel disruption of April 2010, aircraft engine manufacturers had not defined specific particle levels above which engines were considered to be at risk. The general approach taken by airspace regulators was that if the ash concentration rose above zero, then the airspace was considered unsafe and was consequently closed.
The April 2010 eruptions of Eyjafjallajökull caused sufficient economic difficulties that aircraft manufacturers were forced to define specific limits on how much ash is considered acceptable for a jet engine to ingest without damage. In April, the CAA, in conjunction with engine manufacturers, set the safe upper limit of ash density to be 2 mg per cubic metre of air space.
From noon 18 May 2010, the CAA revised the safe limit upwards to 4 mg per cubic metre of air space.
In order to minimise the level of further disruption that this and other volcanic eruptions could cause, the CAA announced the creation of a new category of restricted airspace called a Time Limited Zone. Airspace categorised as TLZ is similar to airspace experiencing severe weather conditions in that the restrictions are expected to be of a short duration; however, the key difference with TLZ airspace is that airlines must produce certificates of compliance in order for their aircraft to enter these areas. Flybe was the first airline to conform to these regulations and their aircraft will be permitted to enter airspace in which the ash density is between 2 mg and 4 mg per cubic metre.
Any airspace in which the ash density exceeds 4 mg per cubic metre is categorised as a no fly zone.

Aviation risks of flight through downstream ash clouds

It is important to make a distinction between flight through (or in immediate vicinity of) the eruption plume and flight through so-called affected airspace. Volcanic ash in the immediate vicinity of the eruption plume is of an entirely different particle size range and density to that found in downwind dispersal clouds which contain only the finest grade of ash. The ash loading at which this process affects normal engine operation is not established beyond the awareness that relatively high ash densities must exist. Whether this silica-melt risk remains at the much lower ash densities characteristic of downstream ash clouds is currently unclear. This is therefore a serious safety hazard which invites preventive risk management strategies in line with other comparable aviation risks.

Human factors

Human factors including pilot error are another potential danger, and currently the most common factor of aviation crashes. Much progress in applying human factors to improving aviation safety was made around the time of World War II by people such as Paul Fitts and Alphonse Chapanis. However, there has been progress in safety throughout the history of aviation, such as the development of the pilot's checklist in 1937. Pilot error and improper communication are often factors in the collision of aircraft. This can take place in the air (1978 Pacific Southwest Airlines Flight 182) (TCAS) or on the ground (1977 Tenerife disaster) (RAAS). The ability of the flight crew to maintain situational awareness is a critical human factor in air safety. Human factors training is available to general aviation pilots and called single pilot resource management training.
Failure of the pilots to properly monitor the flight instruments resulted in the crash of Eastern Air Lines Flight 40 in 1972 (CFIT), and error during take-off and landing can have catastrophic consequences, for example cause the crash of Prinair Flight 191 on landing, also in 1972.
Rarely, flight crew members are arrested or subject to disciplinary action for being intoxicated on the job. In 1990, three Northwest Airlines crew members were sentenced to jail for flying from Fargo, North Dakota to Minneapolis-Saint Paul International Airport while drunk. In 2001, Northwest fired a pilot who failed a breathalyzer test after flying from San Antonio, Texas to Minneapolis-Saint Paul. In July 2002, two America West Airlines pilots were arrested just before they were scheduled to fly from Miami, Florida to Phoenix, Arizona because they had been drinking alcohol. The pilots have been fired from America West and the FAA revoked their pilot's licenses. As of 2005 they await trial in a Florida court. The incident created a public relations problem and America West has become the object of many jokes about drunk pilots. At least one fatal airliner accident involving drunk pilots has occurred when Aero Flight 311 crashed killing all 25 on board in 1961, which underscores the role that poor human choices can play in air accidents.
Human factors incidents are not limited to errors by the pilots. The failure to close a cargo door properly on Turkish Airlines Flight 981 in 1974 resulted in the loss of the aircraft - however the design of the cargo door latch was also a major factor in the incident. In the case of Japan Airlines Flight 123, improper maintenance resulted in the loss of the vertical stabilizer.

Controlled flight into terrain

Controlled flight into terrain is a class of accident in which an undamaged aircraft is flown, under control, into terrain or man-made structures. CFIT accidents typically are a result of pilot error or of navigational system error. Some pilots, convinced that advanced electronic navigation systems such as GPS and inertial guidance systems (inertial navigation system or INS) coupled with flight management system computers , or over-reliance on them, are partially responsible for these accidents, have called CFIT accidents "computerized flight into terrain". Failure to protect Instrument Landing System critical areas can also cause controlled flight into terrain. One of the most notable CFIT accidents was in December 1995 in which American Airlines flight 965 tracked off course while approaching Calí, Colombia and hit a mountainside after the speedbrakes were left deployed despite an aural terrain warning in the cockpit and an attempt to gain ample altitude in the nighttime contidions. Crew awareness and monitoring of navigational systems can prevent or eliminate CFIT accidents. Crew Resource Management is a modern method now widely used to improve the human factors of air safety. The Aviation Safety Reporting System, or ASRS is another.
Other technical aids can be used to help pilots maintain situational awareness. A ground proximity warning system is an on-board system that will alert a pilot if the aircraft is about to fly into the ground. Also, air traffic controllers constantly monitor flights from the ground and at airports.

Terrorism

Terrorism can also be considered a human factor. Crews are normally trained to handle hijack situations. Prior to the September 11, 2001 attacks, hijackings involved hostage negotiations. After the September 11, 2001 attacks, stricter airport security measures are in place to prevent terrorism using a Computer Assisted Passenger Prescreening System, Air Marshals, and precautionary policies. In addition, counter-terrorist organizations monitor potential terrorist activity.
Although most air crews are screened for psychological fitness, some may take suicidal actions. In the case of EgyptAir Flight 990, it appears that the first officer deliberately dived his aircraft into the Atlantic Ocean while the captain was away from his station, in 1999 off Nantucket, Massachusetts. Motivations are unclear, but recorded inputs from the black boxes showed no mechanical problem, no other aircraft in the area, and was corroborated by the cockpit voice recorder.
The use of certain electronic equipment is partially or entirely prohibited as it may interfere with aircraft operation, such as causing compass deviations. Use of personal electronic devices and calculators may be prohibited when an aircraft is below 10,000', taking off, or landing. The American Federal Communications Commission (FCC) prohibits the use of a cell phone on most flights, because in-flight usage creates problems with ground-based cells. There is also concern about possible interference with aircraft navigation systems, although that has never been proven to be a non-serious risk on airliners. A few flights now allow use of cell phones, where the aircraft have been specially wired and certified to meet both FAA and FCC regulations.

Attack by a hostile country

Aircraft, whether passenger planes or military aircraft, are sometimes attacked in both peacetime and war. Notable examples of this are:

• On February 21, 1973 Libyan Arab Airlines Flight 114 727-224 entered the then-Israeli-controlled airspace over the Sinai Peninsula, was intercepted by two Israeli F-4 Phantom IIs and shot down while trying to re-enter Egyptian airspace after failing to follow instructions issued by the Israeli pilots. Of the 113 people on board, there were 5 survivors, including the co-pilot.
• 1 September 1983 downing by the Soviet Union of Korean Air Lines Flight 007, carrying 269 people (including a sitting U.S. Congressman Larry McDonald),
• 3 July 1988 shoot-down by United States Navy of Iran Air Flight 655, carrying 290 people.
• 4 October 2001 shoot-down by Ukrainian Air Force of Russian flight 1812 (Tel-Aviv - Novosibirsk), carrying 78 people.

Airport design

Airport design and location can have a big impact on air safety, especially since some airports such as Chicago Midway International Airport were originally built for propeller planes and many airports are in congested areas where it is difficult to meet newer safety standards. For instance, the FAA issued rules in 1999 calling for a runway safety area, usually extending 500 feet (150 m) to each side and 1,000 feet (300 m) beyond the end of a runway. This is intended to cover ninety percent of the cases of an aircraft leaving the runway by providing a buffer space free of obstacles. Since this is a recent rule, many airports do not meet it. One method of substituting for the 1,000 feet (300 m) at the end of a runway for airports in congested areas is to install an Engineered materials arrestor system, or EMAS. These systems are usually made of a lightweight, crushable concrete that absorbs the energy of the aircraft to bring it to a rapid stop. They have stopped three aircraft (as of 2005) at JFK Airport.

Infection

On an airplane, people sit in a confined space for extended periods of time, which increases the risk of transmission of airborne infections. For this reason, airlines place restrictions on the travel of passengers with known airborne contagious diseases (e.g. tuberculosis). During the severe acute respiratory syndrome (SARS) epidemic of 2003, awareness of the possibility of acquisition of infection on a commercial aircraft reached its zenith when on one flight from Hong Kong to Beijing, 16 of 120 people on the flight developed proven SARS from a single index case.
There is very limited research done on contagious diseases on aircraft. The two most common respiratory pathogens to which air passengers are exposed are parainfluenza and influenza. In one study, the flight ban imposed following the attacks of September 11, 2001 was found to have restricted the global spread of seasonal influenza, resulting in a much milder influenza season that year, and the ability of influenza to spread on aircraft has been well documented. There is no data on the relative contributions of large droplets, small particles, close contact, surface contamination, and no data on the relative importance of any of these methods of transmission for specific diseases, and therefore very little information on how to control the risk of infection. There is no standardisation of air handling by aircraft, installation of HEPA filters or of hand washing by air crew, and no published information on the relative efficacy of any of these interventions in reducing the spread of infection.

Emergency airplane evacuations

According to a 2000 report by the National Transportation Safety Board, emergency airplane evacuations happen about once every 11 days in the U.S. While some situations are extremely dire, such as when the plane is on fire, in many cases the greatest challenge for passengers can be the use of the airplane slide. In a TIME article on the subject, Amanda Ripley reported that when a new supersized Airbus A380 underwent mandatory evacuation tests in 2006, 33 of the 873 evacuating volunteers got hurt. While the evacuation was generally considered a success, one volunteer suffered a broken leg, while the remaining 32 received slide burns. Such accidents are common. In her article, Ripley provides tips on how to make it down the airplane slide without injury.

Runway safety

Several terms fall under the flight safety topic of runway safety, including incursion, excursion, and confusion.
Runway excursion is an incident involving only a single aircraft, where it makes an inappropriate exit from the runway. This can happen because of pilot error, poor weather, or a fault with the aircraft. Overrun is a type of excursion where the aircraft is unable to stop before the end of the runway. A recent example of such an event is Air France Flight 358 in 2005. Further examples can be found in the overruns category.
Runway event is another term for a runway accident.
Runway incursion involves a first aircraft, as well as a second aircraft, vehicle, or person. It is defined by the U.S. FAA as: "Any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and take off of aircraft."
Runway confusion involves a single aircraft, and is used to describe the error when the aircraft makes "the unintentional use of the wrong runway, or a taxiway, for landing or take-off". An example of a runway confusion incident is Comair Flight 191.
Runway excursion is the most frequent type of landing accident, slightly ahead of runway incursion. For runway accidents recorded between 1995 and 2007, 96% were of the 'excursion' type.
The U.S. FAA publishes a lengthy annual report on runway safety issues, available from the FAA website here. New systems designed to improve runway safety, such as Airport Movement Area Safety System (AMASS) and Runway Awareness and Advisory System (RAAS), are discussed in the report. AMASS prevented the serious near-collision in the 2007 San Francisco International Airport runway incursion.

Safety Improvement Initiatives

The Safety Improvement Initiatives are aviation safety partnerships between regulators, manufacturers, operators and professional unions, research organisations, international organisations to further enhance safety. The major Safety initiatives worldwide are:

• Commercial Aviation Safety Team (CAST) in the US. The Commercial Aviation Safety Team (CAST) was founded in 1998 with a goal to reduce the commercial aviation fatality rate in the United States by 80 percent by 2007.
• European Strategic Safety Initiative (ESSI) . The European Strategic Safety Initiative (ESSI) is an aviation safety partnership between EASA, other regulators and the industry. The initiative objective is to further enhance safety for citizens in Europe and worldwide through safety analysis, implementation of cost effective action plans, and coordination with other safety initiatives worldwide.