Traffic collision avoidance system [EN]

A traffic collision avoidance system or traffic alert and collision avoidance system (both abbreviated as TCAS) is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of mid-air collision (MAC). It is a type of airborne collision avoidance system mandated by the International Civil Aviation Organization to be fitted to all aircraft with a maximum take-off mass (MTOM) of over 5700 kg (12,586 lbs) or authorized to carry more than 19 passengers.
Official definition from PANS-ATM (Nov 2007): ACAS / TCAS is an aircraft system based on secondary surveillance radar (SSR) transponder signals, which operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft that are equipped with SSR transponders.

TCAS and EHSI cockpit display

In modern glass cockpit aircraft, the TCAS display may be integrated in the Navigation Display (ND) or Electronic Horizontal Situation Indicator (EHSI); in older glass cockpit aircraft and those with mechanical instrumentation, such an integrated TCAS display may replace the mechanical Vertical Speed Indicator (which indicates the rate with which the aircraft is descending or climbing).

Impetus for a collision prevention system

Research into collision avoidance systems has been ongoing since at least the 1950s. ICAO and aviation authorities such as the Federal Aviation Administration were spurred into action after several major mid-air collisions involving great loss of life. Some of these mid-air accidents include:

• Grand Canyon midair collision in 1956;
• The New York air disaster in 1960;
• The Asheville midair collision in 1967;
• The Zagreb mid-air collision in 1976;
• PSA Flight 182, a Boeing 727 which collided with a Cessna 172 in 1978;
• The Ukraine Aeroflot mid-air collision, between two Tupolev Tu-134 in 1979;
• Aeroméxico Flight 498, a 1986 collision similar to PSA Flight 182, which finally spurred the US Congress and other regulatory bodies into action and led to mandatory collision avoidance equipment.
• Chakri Dadri midair collision over a town near New Delhi, India in 1996;

The implementation of TCAS added a safety barrier to help prevent mid-air collisions. However, further study, refinements, training and regulatory measures were still required, because the limitations and misuse of the system still resulted in other incidents and fatal accidents, which include:

• The Japan Airlines near-miss incident in 2001;
• The Überlingen mid-air collision, between a Boeing 757 and a Tupolev Tu-154 in 2002, where the Tupolev pilots declined to follow their TCAS resolution advisory (RA), instead following the directions of the air traffic controller, while the Boeing pilots followed their TCAS RA. having no ATC instruction. By the time the crews of the two planes actually saw each other, it was too late and the planes collided, killing 71;
• The Gol Flight 1907 collision with an Embraer Legacy 600 in 2006;

TCAS basics

System description

TCAS involves communication between all aircraft equipped with an appropriate transponder (provided the transponder is enabled and set up properly). Each TCAS-equipped aircraft interrogates all other aircraft in a determined range about their position (via the 1,030 MHz radio frequency), and all other craft reply to other interrogations (via 1,090 MHz). This interrogation-and-response cycle may occur several times per second.
The TCAS system builds a three dimensional map of aircraft in the airspace, incorporating their range (garnered from the interrogation and response round trip time), altitude (as reported by the interrogated aircraft), and bearing (by the directional antenna from the response). Then, by extrapolating current range and altitude difference to anticipated future values, it determines if a potential collision threat exists.
TCAS and its variants are only able to interact with aircraft that have a correctly operating mode C or mode S transponder. A unique 24-bit identifier is assigned to each aircraft that has a mode S transponder.
The next step beyond identifying potential collisions is automatically negotiating a mutual avoidance maneuver (currently, maneuvers are restricted to changes in altitude and modification of climb/sink rates) between the two (or more) conflicting aircraft. These avoidance maneuvers are communicated to the flight crew by a cockpit display and by synthesized voice instructions.
A protected volume of airspace surrounds each TCAS equipped aircraft. The size of the protected volume depends on the altitude, speed, and heading of the aircraft involved in the encounter. The illustration below gives an example of a typical TCAS protection volume.

System components

A TCAS installation consists of the following components:

TCAS computer unit

Performs airspace surveillance, intruder tracking, its own aircraft altitude tracking, threat detection, RA maneuver determination and selection, and generation of advisories. The TCAS Processor uses pressure altitude, radar altitude, and discrete aircraft status inputs from its own aircraft to control the collision avoidance logic parameters that determine the protection volume around the TCAS aircraft.

Antennas

The antennas used by TCAS II include a directional antenna that is mounted on the top of the aircraft and either an omnidirectional or a directional antenna mounted on the bottom of the aircraft. Most installations use the optional directional antenna on the bottom of the aircraft. In addition to the two TCAS antennas, two antennas are also required for the Mode S transponder. One antenna is mounted on the top of the aircraft while the other is mounted on the bottom. These antennas enable the Mode S transponder to receive interrogations at 1030 MHz and reply to the received interrogations at 1090 MHz.

Cockpit presentation

The TCAS interface with the pilots is provided by two displays: the traffic display and the RA display. These two displays can be implemented in a number of ways, including displays that incorporate both displays into a single, physical unit. Regardless of the implementation, the information displayed is identical. The standards for both the traffic display and the RA display are defined in DO-185A.

TCAS operation

The following section describes the TCAS operation based on TCAS II, since this is the version that has been adopted as an international standard (ACAS II) by ICAO and aviation authorities worldwide.

TCAS operation modes

TCAS II can be currently operated in the following modes:

Stand-by

Power is applied to the TCAS Processor and the mode S transponder, but TCAS does not issue any interrogations and the transponder will reply to only discrete interrogations.

Transponder

The mode S transponder is fully operational and will reply to all appropriate ground and TCAS interrogations. TCAS remains in stand-by.

Traffic advisories only

The mode S transponder is fully operational. TCAS will operate normally and issue the appropriate interrogations and perform all tracking functions. However, TCAS will only issue traffic advisories (TA), and the resolution advisories (RA) will be inhibited.

Automatic (traffic/resolution advisories)

The mode S transponder is fully operational. TCAS will operate normally and issue the appropriate interrogations and perform all tracking functions. TCAS will issue traffic advisories (TA) and resolution advisories (RA), when appropriate.

TCAS works in a coordinated manner, so when an RA is issued to conflicting aircraft, a required action (i.e., Climb. Climb.) has to be immediately performed by one of the aircraft, while the other one receives a similar RA in the opposite direction (i.e., Descend. Descend.).

TCAS alerts

TCAS II typical envelope

TCAS II types of RA

TCAS II issues the following types of aural annunciations:

• Traffic advisory (TA)
• Resolution advisory (RA)
• Clear of conflict

When a TA is issued, pilots are instructed to initiate a visual search for the traffic causing the TA. If the traffic is visually acquired, pilots are instructed to maintain visual separation from the traffic. The pilot training programs also indicate that no horizontal maneuvers are to be made based solely on information shown on the traffic display. Slight adjustments in vertical speed while climbing or descending, or slight adjustments in airspeed while still complying with the ATC clearance are acceptable.
When an RA is issued, pilots are expected to respond immediately to the RA unless doing so would jeopardize the safe operation of the flight. This means that aircraft will at times have to manoeuver contrary to ATC instructions or disregard ATC instructions. In these cases, the controller is no longer responsible for separation of the aircraft involved in the RA until the conflict is terminated.
On the other hand, ATC can potentially interfere with the pilot’s response to RAs. If a conflicting ATC instruction coincides with an RA, the pilot may assume that ATC is fully aware of the situation and is providing the better resolution. But in reality ATC is not aware of the RA until the RA is reported by the pilot. Once the RA is reported by the pilot, ATC is required not to attempt to modify the flight path of the aircraft involved in the encounter. Hence, the pilot is expected to “follow the RA” but in practice this does not yet always happen.
Some States have implemented “RA downlink” which provides air traffic controllers with information about RAs posted in the cockpit obtained via Mode S radars. Currently, there are no ICAO provisions concerning the use of RA downlink by air traffic controllers.
The following points receive emphasis during pilot training:

• Do not manoeuver in a direction opposite to that indicated by the RA because this may result in a collision.
• Inform the controller of the RA as soon as permitted by flight crew workload after responding to the RA. There is no requirement to make this notification prior to initiating the RA response.
• Be alert for the removal of RAs or the weakening of RAs so that deviations from a cleared altitude are minimized.
• If possible, comply with the controller’s clearance, e.g. turn to intercept an airway or localizer, at the same time as responding to an RA.
• When the RA event is completed, promptly return to the previous ATC clearance or instruction or comply with a revised ATC clearance or instruction.

 

Types of traffic and resolution advisories

Type	Text	Meaning	Required action
TA	Traffic; traffic.	Intruder near both horizontally and vertically.	Attempt visual contact, and be prepared to maneuver if an RA occurs.
RA	Climb; climb.	Intruder will pass below	Begin climbing at 1500–2000 ft/min
RA	Descend. Descend.	Intruder will pass above.	Begin descending at 1500–2000 ft/min
RA	Increase climb.	Intruder will pass just below	Climb at 2500 – 3000 ft/min.
RA	Increase descent.	Intruder will pass just above.	Descend at 2500 – 3000 ft/min.
RA	Reduce climb.	Intruder is probably well below.	Climb at a slower rate.
RA	Reduce descent.	Intruder is probably well above.	Descend at a slower rate.
RA	Climb; climb now.	Intruder that was passing above, will now pass below.	Change from a descent to a climb.
RA	Descend; descend now.	Intruder that was passing below, will now pass above.	Change from a climb to a descent.
RA	Maintain vertical speed; maintain.	Intruder will be avoided if vertical rate is maintained.	Maintain current vertical rate.
RA	Adjust vertical speed; adjust.	Intruder considerably away, or weakening of initial RA.	Begin to level off.
RA	Monitor vertical speed.	Intruder ahead in level flight, above or below.	Remain in level flight.
RA	Crossing.	Passing through the intruder's level. Usually added to any other RA.	Proceed according to the associated RA.
CC	Clear of conflict.	Intruder is no longer a threat.	Return promptly to previous ATC clearance.

 

Pilot/aircrew interaction during a TCAS event

TCAS event interaction

Aircrew	Controller
Traffic advisory (TA)
Shall not manoeuver their aircraft in response to traffic advisories (TAs) only	Remains responsible for ATC separation
Should prepare for appropriate action if an RA occurs; but as far as practicable, pilots should not request traffic information	If requested by the aircrew, shall give traffic information
Resolution advisory (RA)
Shall respond immediately and manoeuver as indicated, unless doing so would jeopardize the safety of the airplane	Shall not attempt to modify the flight path of an aircraft responding to an RA
Shall follow the RA even if there is a conflict between the RA and an Air Traffic Control (ATC) instruction to manoeuver	Shall not issue any clearance or instruction to the aircraft involved until the pilot reports returning to the terms of the assigned ATC clearance or instruction
Shall never manoeuver in the opposite sense to an RA, nor maintain a vertical rate in the opposite sense to an RA	Shall acknowledge the report by using the phrase "ROGER"
When deviating from an air traffic control instruction or clearance in response to any RA, shall: As soon as permitted by flight crew workload, notify the appropriate ATC unit of the deviation. Immediately inform ATC when they are unable to comply with a clearance or instruction that conflicts with an RA.	If requested by the aircrew, shall give traffic information
Shall promptly comply with any subsequent RAs issued by TCAS	Ceases to be responsible for providing separation between that aircraft and any other aircraft affected as a direct consequence of the manoeuver induced by the RA
Shall limit the alterations of the flight path to the minimum extent necessary to comply with the resolution advisories
Clear of conflict (CC)
Shall promptly return to the terms of the ATC instruction or clearance when the conflict is resolved	Shall resume responsibility for providing separation for all the affected aircraft when he acknowledges: A report from the pilot that the aircraft is resuming the assigned ATC clearance or instruction and issues an alternative clearance or instruction which is acknowledged by the pilot A report from the pilot that the aircraft has resumed the assigned ATC clearance or instruction
Shall notify ATC after initiating a return to or resuming the current clearance

 

Safety aspects of TCAS

Safety studies on TCAS estimate that the system improves safety in the airspace by a factor of between 3 and 5.
However, it is well understood that part of the remaining risk is that TCAS may induce midair collisions: "In particular, it is dependent on the accuracy of the threat aircraft’s reported altitude and on the expectation that the threat aircraft will not make an abrupt maneuver that defeats the TCAS Resolution Advisory (RA). The safety study also shows that TCAS II will induce some critical near midair collisions..." (See page 7 of Introduction to TCAS II Version 7 and 7.1 (PDF) in external links below).
One potential problem with TCAS II is the possibility that a recommended avoidance maneuver might direct the flight crew to descend toward terrain below a safe altitude. Recent requirements for incorporation of ground proximity mitigate this risk. Ground proximity warning alerts have priority in the cockpit over TCAS alerts.
Some pilots have been unsure how to act when their aircraft was requested to climb whilst flying at their maximum altitude. The accepted procedure is to follow the climb RA as best as possible, temporarily trading speed for height. The climb RA should quickly finish. In the event of a stall warning, the stall warning would take priority.
Both cases have been already addressed by Version 7.0 of TCAS II and are currently handled by a corrective RA together with a visual indication of a green arc in the IVSI display to indicate the safe range for the climb or descent rate. However, it has been found that in some cases these indications could lead to a dangerous situation for the involved aircraft. For example, if a TCAS event occurs when two aircraft are descending one over the other for landing, the aircraft at the lower altitude will first receive a "Descend, descend" RA, and when reaching an extreme low altitude, this will change to a "Adjust Vertical Speed, Adjust" RA, together with a green arc indication directing the pilot to level off the aircraft. This could place the aircraft dangerously into the path of the intruder above, who is descending to land. A change proposal has been issued to correct this problem.

Relationship to automatic dependent surveillance-broadcast (ADS-B)

Automatic dependent surveillance-broadcast (ADS-B) messages are transmitted from aircraft equipped with suitable transponders, containing information such as identity, location, and velocity. The signals are broadcast on the 1090 MHz radio frequency. ADS-B messages are also carried on a Universal Access Transceiver (UAT) in the 978 MHz band.
TCAS equipment which is capable of processing ADS-B messages may use this information to enhance the performance of TCAS, using techniques known as "hybrid surveillance". As currently implemented, hybrid surveillance uses reception of ADS-B messages from an aircraft to reduce the rate at which the TCAS equipment interrogates that aircraft. This reduction in interrogations reduces the use of the 1030/1090 MHz radio channel, and will over time extend the operationally useful life of TCAS technology. The ADS-B messages will also allow low cost (for aircraft) technology to provide real time traffic in the cockpit for small aircraft. Currently UAT based traffic uplinks are provided in Alaska and in regions of the East coast of the USA.
Hybrid surveillance does not include the use any of the aircraft flight information in the TCAS conflict detection algorithms; ADS-B is used only to identify aircraft that can safely be interrogated at a lower rate.
In the future, prediction capabilities may be improved by using the state vector information present in ADS-B messages. Also, since ADS-B messages can be received at greater range than TCAS normally operates, aircraft can be acquired earlier by the TCAS tracking algorithms.
The identity information present in ADS-B messages can be used to label other aircraft on the cockpit display (where present), painting a picture similar to what an air traffic controller would see and improving situational awareness.

Drawbacks to TCAS and ADS-B

The major demonstrated problem of the ADS-B protocol integration is this added verbosity of the extra information transmitted, which is considered unnecessary for collision avoidance purposes. The more data transmitted from one aircraft in accordance with the system design, the lesser the number of aircraft that can participate in the system, due to the fixed and limited channel data bandwidth (1 megabit/second with the 26/64 data bits to packet length bit capacity of the Mode S downlink data format packet). For every Mode S message of 64 bits, the overhead demands 8 for clock sync at the receiver and Mode S packet discovery, 6 for type of Mode S packet, 24 for who it came from. Since that leaves only 26 for information, multiple packets must be used to convey a single message. The ADS-B "fix" proposal is to go to a 128 bit packet, which is not an accepted international standard. Either approach increases channel traffic above the level sustainable for environments such as the Los Angeles Basin.

Versions of TCAS

Passive

Collision Avoidance systems which rely on transponder replies triggered by ground and airborne systems are considered passive. Ground and airborne interrogators query nearby transponders for mode C altitude information, which can be monitored by third-party systems for traffic information. Passive systems display traffic similar to TCAS, however generally have a range of less than 7 nautical miles (13 km).

TCAS I

TCAS I is the first generation of collision avoidance technology. It is cheaper but less capable than the modern TCAS II system, and is mainly intended for general aviation use. TCAS I systems are able to monitor the traffic situation around a plane (to a range of about 40 miles) and offer information on the approximate bearing and altitude of other aircraft. It can also generate collision warnings in the form of a "Traffic Advisory" (TA). The TA warns the pilot that another aircraft is in near vicinity, announcing "Traffic, traffic", but does not offer any suggested remedy; it is up to the pilot to decide what to do, usually with the assistance of Air Traffic Control. When a threat has passed, the system announces "Clear of conflict".

TCAS II

Change proposal CP112E graphical explanation

Change proposal CP115 graphical explanation

TCAS II is the second and current generation of instrument warning TCAS, used in the majority of commercial aviation aircraft (see table below). It offers all the benefits of TCAS I, but will also offer the pilot direct, vocalized instructions to avoid danger, known as a "Resolution Advisory" (RA). The suggestive action may be "corrective", suggesting the pilot change vertical speed by announcing, "Descend, descend", "Climb, climb" or "Adjust Vertical Speed Adjust" (meaning reduce vertical speed). By contrast a "preventive" RA may be issued which simply warns the pilots not to deviate from their present vertical speed, announcing, "Monitor vertical speed" or "Maintain vertical speed, Maintain". TCAS II systems coordinate their resolution advisories before issuing commands to the pilots, so that if one aircraft is instructed to descend, the other will typically be told to climb — maximising the separation between the two aircraft.
As of 2006, the only implementation that meets the ACAS II standards set by ICAO was Version 7.0 of TCAS II, produced by three avionics manufacturers: Rockwell Collins, Honeywell, and ACSS (Aviation Communication & Surveillance Systems; an L-3 Communications and Thales Avionics company).
After the Überlingen mid-air collision (July 1, 2002), studies have been made to improve TCAS II capabilities. Following extensive Eurocontrol input and pressure, a revised TCAS II Minimum Operational Performance Standards (MOPS) document has been jointly developed by RTCA (Special Committee SC-147) and EUROCAE. As a result, by 2008 the standards for Version 7.1 of TCAS II have been issued and published as RTCA DO-185B (June 2008) and EUROCAE ED-143 (September 2008).
TCAS II Version 7.1 will be able to issue RA reversals in coordinated encounters, in case one of the aircraft doesn't follow the original RA instructions (Change proposal CP112E). Other changes in this version are the replacement of the ambiguous "Adjust Vertical Speed, Adjust" RA with the "Level off, Level off" RA, to prevent improper response by the pilots (Change proposal CP115).; and the improved handling of corrective/preventive annunciation and removal of green arc display when a positive RA weakens solely due to an extreme low or high altitude condition (1000 feet AGL or below, or near the aircraft top ceiling) to prevent incorrect and possibly dangerous guidance to the pilot (Change proposal CP116).
Studies conducted for Eurocontrol, using recently recorded operational data, indicate that currently the probability of a mid-air collision in European airspace is 2.7 x 10⁻⁸ which equates to one in every 3 years. When TCAS II Version 7.1 is implemented, that probability will be reduced by a factor of 4.

TCAS III

Originally designated TCAS II Enhanced, TCAS III was envisioned as an expansion of the TCAS II concept to include horizontal resolution advisory capability. TCAS III was the "next generation" of collision avoidance technology which underwent development by aviation companies such as Honeywell. TCAS III incorporated technical upgrades to the TCAS II system, and had the capability to offer traffic advisories and resolve traffic conflicts using horizontal as well as vertical manouevring directives to pilots. For instance, in a head-on situation, one aircraft might be directed, "turn right, climb" while the other would be directed "turn right, descend." This would act to further increase the total separation between aircraft, in both horizontal and vertical aspects. Horizontal directives would be useful in a conflict between two aircraft close to the ground where there may be little if any vertical maneuvering space.
TCAS III attempts to use the TCAS directional antenna to assign a bearing to other aircraft, and thus be able to generate a horizontal maneuver (e.g. turn left or right). However, it was judged by the industry to be unfeasible due to limitations in the accuracy of the TCAS directional antennas. The directional antennas were judged not to be accurate enough to generate an accurate horizontal-plane position, and thus an accurate horizontal resolution. By 1995, years of testing and analysis determined that the concept was unworkable using available surveillance technology (due to the inadequacy of horizontal position information), and that horizontal RAs were unlikely to be invoked in most encounter geometries. Hence, all work on TCAS III was suspended and there are no plans for its implementation. The concept has later evolved and been replaced by TCAS IV.

TCAS IV

TCAS IV uses additional information encoded by the target aircraft in the Mode S transponder reply (i.e. target encodes its own position into the transponder signal) to generate a horizontal resolution to an RA. Obviously, this requires the target aircraft to have some data link capability at a minimum. In addition, some reliable source of position (such as Inertial Navigation System or GPS) is needed on the target aircraft in order for it to be encoded.
TCAS IV has replaced the TCAS III concept by the mid 1990s. One of the results of TCAS III experience has been that the directional antenna used by the TCAS processor to assign a bearing to a received transponder reply is not accurate enough to generate an accurate horizontal position, and thus a safe horizontal resolution. TCAS IV uses additional position information encoded on an air-to-air data link to generate the bearing information, so the accuracy of the directional antenna would not be a factor.
TCAS IV development continued for some years, but the appearance of new trends in data link such as Automatic Dependent Surveillance - Broadcast (ADS-B) have pointed out a need to re-evaluate whether a data link system dedicated to collision avoidance such as TCAS IV should be incorporated into a more generic system of air-to-air data link for additional applications. As a result of these issues, the TCAS IV concept was abandoned as ADS-B development started.

Current implementation

Although the system occasionally suffers from false alarms, pilots are now under strict instructions to regard all TCAS messages as genuine alerts demanding an immediate, high-priority response. Windshear Detection and GPWS alerts and warnings have higher priority than the TCAS. The FAA and most other countries' authorities' rules state that in the case of a conflict between TCAS RA and air traffic control (ATC) instructions, the TCAS RA always takes precedence (this is mainly because of the TCAS-RA inherently possessing a more current and comprehensive picture of the situation than air traffic controllers, whose radar/transponder updates usually happen at a much slower rate than the TCAS interrogations). If one aircraft follows a TCAS RA and the other follows conflicting ATC instructions, a collision can occur, such as the July 1, 2002 Überlingen disaster. In this mid-air collision, both airplanes were fitted with TCAS II Version 7.0 systems which functioned properly, but one obeyed the TCAS advisory while the other ignored the TCAS and obeyed the controller; both aircraft descended into a fatal collision.
This accident could have been prevented if TCAS was able to reverse the original RA for one of the aircraft when it detects that the crew of the other one is not following their original TCAS RA, but conflicting ATC instructions instead. This is one of the features that will be implemented within Version 7.1 of TCAS II.
Implementation of TCAS II Version 7.1 has been originally planned to start between 2009 and 2011 by retrofitting and forward fitting all the TCAS II equipped aircraft, with the goal that by 2014 the version 7.0 will be completely phased out and replaced by version 7.1. The FAA and EASA have already published the TCAS II Version 7.1 Technical Standard Order (TSO-C119c and ETSO-C119c, respectively) effective since 2009, based on the RTCA DO-185B and EUROCAE ED-143 standards. On 25 September 2009 FAA issued Advisory Circular AC 20-151A providing guidance for obtaining airworthiness approval for TCAS II systems, including the new version 7.1. On 5 October 2009 the Association of European Airlines (AEA) published a Position Paper showing the need to mandate TCAS II Version 7.1 on all aircraft as a matter of priority. On 25 March 2010 the European Aviation Safety Agency (EASA) published Notice of Proposed Amendment (NPA) No. 2010-03 pertaining to the introduction of ACAS II software version 7.1. On 14 September 2010 EASA published the Comment Response Document (CRD) to the above mentioned NPA. Separately, a proposal has been made to amend the ICAO standard to require TCAS II Version 7.1 for compliance with ACAS II SARPs.
ICAO has circulated an amendment for formal member state agreement which recommends TCAS II Change 7.1 adoption by 1 January 2014 for forward fit and 1 January 2017 for retrofit. Following the feedback and comments from airline operators, EASA has proposed the following dates for the TCAS II Version 7.1 mandate in European airspace: forward fit (for new aircraft) 1 March 2012, retrofit (for existing aircraft) 1 December 2015. These dates are proposed dates, subject to further regulatory processes, and are not final until the Implementing Rule has been published.
Among the system manufacturers, by February 2010 ACSS certified Change 7.1 for their TCAS 2000 and Legacy TCAS II systems, and is currently offering Change 7.1 upgrade for their customers. By June 2010 Honeywell published a white paper with their proposed solutions for TCAS II Version 7.1. Rockwell Collins currently announces that their TCAS-94, TCAS-4000 and TSS-4100 TCAS II compliant systems are software upgradeable to Change 7.1 when available.

 

Current TCAS Limitations

While the safety benefits of current TCAS implementations are self-evident, the full technical and operational potential of TCAS is not fully exploited due to limitations in current implementations (most of which will need to be addressed in order to further facilitate the design and implementation of Free flight):

• TCAS is limited to supporting only vertical separation advisories, more complex traffic conflict scenarios may however be more easily and efficiently remedied by also making use of lateral resolution maneuvers; this applies in particular to traffic conflicts with marginal terrain clearance, or conflict scenarios that are similarly restricted by vertical constraints (e.g. in busy RVSM airspace)
• ATC can be automatically informed about resolution advisories issued by TCAS only when the aircraft is within an area covered by a Mode S, or an ADS-B monitoring network. In other cases controllers may be unaware of TCAS-based resolution advisories or even issue conflicting instructions (unless ATC is explicitly informed by cockpit crew members about an issued RA during a high-workload situation), which may be a source of confusion for the affected crews while additionally also increasing pilot work load. In May 2009, Luxembourg, Hungary and the Czech Republic show downlinked RAs to controllers.
• In the above context, TCAS lacks automated facilities to enable pilots to easily report and acknowledge reception of a (mandatory) RA to ATC (and intention to comply with it), so that voice radio is currently the only option to do so, which however additionally increases pilot and ATC workload, as well as frequency congestion during critical situations.
• In the same context, situational awareness of ATC depends on exact information about aircraft maneuvering, especially during conflict scenarios that may possibly cause or contribute to new conflicts by deviating from planned routing, so automatically visualizing issued resolution advisories and recalculating the traffic situation within the affected sector would obviously help ATC in updating and maintaining situational awareness even during unplanned, ad hoc routing changes induced by separation conflicts.
• Today's TCAS displays do not provide information about resolution advisories issued to other (conflicting) aircraft, while resolution advisories issued to other aircraft may seem irrelevant to another aircraft, this information would enable and help crews to assess whether other aircraft (conflicting traffic) actually comply with RAs by comparing the actual rate of (altitude) change with the requested rate of change (which could be done automatically and visualized accordingly by modern avionics), thereby providing crucial realtime information for situational awareness during highly critical situations.
• TCAS displays today are often primarily range-based, as such they only show the traffic situation within a configurable range of miles/feet, however under certain circumstances a "time-based" representation (i.e. within the next xx minutes) might be more intuitive.
• Lack of terrain/ground and obstacle awareness (e.g. connection to TAWS, including MSA sector awareness), which might be critical for creating feasible (non-dangerous, in the context of terrain clearance) and useful resolution advisories (i.e. prevent extreme descent instructions if close to terrain), to ensure that TCAS RAs never facilitate CFIT (Controlled Flight into Terrain) scenarios.
• Aircraft performance in general and current performance capabilities in particular (due to active aircraft configuration) are not taken into account during the negotiation and creation of resolution advisories (as it is the case for differences between different types of aircraft, e.g. turboprop/jet vs. helicopters), so that it is theoretically possible that resolution advisories are issued that demand climb or sink rates outside the normal/safe flight envelope of an aircraft during a certain phase of flight (i.e. due to the aircraft's current configuration). Furthermore, as all traffic is being dealt with equally, there's no distinction taking place between different types of aircraft, neglecting the option of exploiting aircraft-specific (performance) information to issue customized and optimized instructions for any given traffic conflict (i.e. by issuing climb instructions to those aircraft that can provide the best climb rates, while issuing descend instructions to aircraft providing comparatively better sink rates, thereby hopefully maximizing altitude change per time unit, that is separation). As an example, TCAS can order an aircraft to climb when it is already at its service ceiling for its current configuration.
• TCAS is primarily extrapolation-oriented, as such it is using algorithms trying to approximate 4D trajectory prediction using the "flight path history", in order to assess and evaluate the current traffic situation within an aircraft's proximity, however the degree of data- reliability and usefulness could be significantly improved by enhancing said information with limited access to relevant flight plan information, as well as to relevant ATC instructions to get a more comprehensive picture of other traffic's (route) plans and intentions, so that flight path predictions would no longer be merely based on estimations but rather actual aircraft routing (FMS flight plan) and ATC instructions. If TCAS is modified to use data that is used by other systems, care will be required to ensure that the risks of common failure modes are sufficiently small.
• TCAS is not fitted to many smaller aircraft mainly due to the high costs involved (between $25,000 and $150,000). Many smaller personal business jets for example, are currently not legally required to have TCAS installed, even though they fly in the same airspace as larger aircraft that are required to have proper TCAS equipment on board. The TCAS system can only perform at its true operational potential once all aircraft in any given airspace have a properly working TCAS unit on board.

External links

• EUROCONTROL ACAS Website
• TCAS II Version 7.1
• Discussion of TCAS
• AIS-P/TailLight alternative to TCAS and ADS-B without the problems of TCAS and ADS-B
• Critical discussion of TCAS using hypothetical abuse/exploit scenarios of TCAS usage
• Introduction to TCAS II Version 7
• Introduction to TCAS II Version 7.1
• Decision criteria for regulatory measures on TCAS II version 7.1
• TCAS User Interface Awareness video toolkit on Skybrary
• Collision avoidance on the UKCS (TCAS II Trial) by Mark Prior (Bristow)
• Private Jet Safety

Airbus A380 [EN]

The Airbus A380 is a double-deck, wide-body, four-engine jet airliner manufactured by the European corporation Airbus, a subsidiary of EADS. It is the largest passenger airliner in the world. Designed to challenge Boeing's monopoly in the large-aircraft market, the A380 made its maiden flight on 27 April 2005 and entered commercial service in October 2007 with Singapore Airlines. The aircraft was known as the Airbus A3XX during much of its development, before receiving the A380 model number. The nickname Superjumbo has since become associated with it.The A380's upper deck extends along the entire length of the fuselage, and its width is equivalent to that of a widebody aircraft. This allows for an A380-800's cabin with 5,146 square feet (478.1 m²) of floor space; 49% more floor space than the current next-largest airliner, the Boeing 747-400 with 3,453 square feet (320.8 m²), and provides seating for 525 people in a typical three-class configuration or up to 853 people in all-economy class configurations. The A380-800 has a design range of 15,200 km (8,200 nmi; 9,400 mi), sufficient to fly from New York to Hong Kong for example, and a cruising speed of Mach 0.85 (about 900 km/h or 560 mph at cruising altitude).

As of July 2011^[update] there had been 236 firm orders for the A380, of which 53 had been delivered. The largest order, for 90 aircraft, was from Emirates

Development

 Background

In the summer of 1988, a group of Airbus engineers led by Jean Roeder began working in secret on the development of a ultra-high-capacity airliner (UHCA), both to complete its own range of products and to break the dominance that Boeing had enjoyed in this market segment since the early 1970s with its 747. McDonnell Douglas unsuccessfully offered its smaller, double-deck MD-12 concept for sale. Roeder was given approval for further evaluations of the UHCA after a formal presentation to the President and CEO in June 1990. The megaproject was announced at the 1990 Farnborough Air Show, with the stated goal of 15% lower operating costs than the 747-400. Airbus organised four teams of designers, one from each of its partners (Aérospatiale, Deutsche Aerospace AG, British Aerospace, CASA) to propose new technologies for its future aircraft designs. The designs would be presented in 1992 and the most competitive designs would be used.

In January 1993, Boeing and several companies in the Airbus consortium started a joint feasibility study of an aircraft known as the Very Large Commercial Transport (VLCT), aiming to form a partnership to share the limited market. This joint study was abandoned two years later, Boeing's interest having decreased because analysts thought that such a product would unlikely earn the $15-billion in development costs. Despite the fact that only two airlines had expressed public interest in purchasing such a plane, Airbus was already pursuing its own large plane project. Analysts suggested that Boeing instead would pursue stretching their 747 design, and that air travel was already moving away from the hub and spoke system that consolidated traffic into large planes, and toward more non-stop routes that could be served by smaller planes.

The first completed A380 at the "A380 Reveal"
event held in Toulouse, France, 18 January 2005

In June 1994, Airbus began developing its own very large airliner, designated the A3XX. Airbus considered several designs, including an odd side-by-side combination of two fuselages from the A340, which was Airbus’s largest jet at the time. The A3XX was pitted against the VLCT study and Boeing’s own New Large Aircraft successor to the 747. From 1997 to 2000, as the East Asian financial crisis darkened the market outlook, Airbus refined its design, targeting a 15 to 20% reduction in operating costs over the existing Boeing 747-400. The A3XX design converged on a double-decker layout that provided more passenger volume than a traditional single-deck design, in line with traditional hub-and-spoke theory as opposed to the point-to-point theory of the Boeing 777, after conducting an extensive market analysis with over 200 focus groups.



Design phase

On 19 December 2000, the supervisory board of newly restructured Airbus voted to launch a €8.8-billion programme to build the A3XX, re-christened as the A380, with 50 firm orders from six launch customers. The A380 designation was a break from previous Airbus families, which had progressed sequentially from A300 to A340. It was chosen because the number 8 resembles the double-deck cross section, and is a lucky number in some Asian countries where the aircraft was being marketed. The aircraft’s configuration was finalised in early 2001, and manufacturing of the first A380 wing box component started on 23 January 2002. The development cost of the A380 had grown to €11 billion when the first aircraft was completed.

Production

Geographical logistics sequence for the A380, with final assembly in Toulouse

Major structural sections of the A380 are built in France, Germany, Spain, and the United Kingdom. Due to their size, they are brought to the assembly hall (the Jean-Luc Lagardère Plant) in Toulouse in France by surface transportation, though some parts are moved by the A300-600ST Beluga aircraft used in the construction of other Airbus models. Components of the A380 are provided by suppliers from around the world; the five largest contributors, by value, are Rolls-Royce, Safran, United Technologies, General Electric and Goodrich.

Transporting A380 components from the port of Bordeaux.

For the surface movement of large A380 structural components, a complex route known as the Itinéraire à Grand Gabarit was developed. This involved the construction of a fleet of roll-on/roll-off (RORO) ships and barges, the construction of port facilities and the development of new and modified roads to accommodate oversized road convoys.

The front and rear sections of the fuselage are loaded onto one of three roll-on/roll-off (RORO) ships in Hamburg in northern Germany, from where they are shipped to the United Kingdom. The wings, which are manufactured at Filton in Bristol and Broughton in North Wales, are transported by barge to Mostyn docks, where the ship adds them to its cargo. In Saint-Nazaire in western France, the ship trades the fuselage sections from Hamburg for larger, assembled sections, some of which include the nose. The ship unloads in Bordeaux. Afterwards, the ship picks up the belly and tail sections by Construcciones Aeronáuticas SA in Cádiz in southern Spain, and delivers them to Bordeaux. From there, the A380 parts are transported by barge to Langon, and by oversize road convoys to the assembly hall in Toulouse.

After assembly, the aircraft are flown to Hamburg Finkenwerder Airport (XFW) to be furnished and painted. It takes 3,600 L (950 US gal) of paint to cover the 3,100 m² (33,000 sq ft) exterior of an A380. Airbus sized the production facilities and supply chain for a production rate of four A380s per month.

Testing

A380 MSN001 about to land after its maiden flight

Five A380s were built for testing and demonstration purposes. The first A380, serial number MSN001 and registration F-WWOW, was unveiled at a ceremony in Toulouse on 18 January 2005. Its maiden flight took place at 8:29 UTC (10:29 am local time) 27 April 2005. This plane, equipped with Trent 900 engines, flew from Toulouse Blagnac International Airport with a flight crew of six headed by chief test pilot Jacques Rosay. After successfully landing three hours and 54 minutes later, Rosay said flying the A380 had been “like handling a bicycle” .

On 1 December 2005 the A380 achieved its maximum design speed of Mach 0.96 (versus typical cruising speed of Mach 0.85), in a shallow dive, completing the opening of the flight envelope. In 2006, the A380 flew its first high altitude test at Bole International Airport, Addis Ababa. It conducted its second high altitude test at the same airport in 2009. It arrived in North America on 6 February 2006, landing in Iqaluit, Nunavut in Canada for cold-weather testing.

Flight test engineer's station on the lower deck of A380 F-WWOW

On 14 February 2006, during the destructive wing strength certification test on MSN5000, the test wing of the A380 failed at 145% of the limit load, short of the required 150% to meet the certification. Airbus announced modifications adding 30 kg to the wing to provide the required strength. On 26 March 2006 the A380 underwent evacuation certification in Hamburg. With 8 of the 16 exits blocked, 853 passengers and 20 crew left the aircraft in 78 seconds, less than the 90 seconds required by certification standards. Three days later, the A380 received European Aviation Safety Agency (EASA) and United States Federal Aviation Administration (FAA) approval to carry up to 853 passengers.

The maiden flight of the first A380 using GP7200 engines—serial number MSN009 and registration F-WWEA—took place on 25 August 2006. On 4 September 2006, the first full passenger-carrying flight test took place. The aircraft flew from Toulouse with 474 Airbus employees on board, in the first of a series of flights to test passenger facilities and comfort. In November 2006 a further series of route proving flights took place to demonstrate the aircraft's performance for 150 flight hours under typical airline operating conditions.

Airbus obtained type certificates for the A380-841 and A380-842 model from the EASA and FAA on 12 December 2006 in a joint ceremony at the company's French headquarters. The A380-861 model obtained the type certificate 14 December 2007.

Production and delivery delays

Initial production of the A380 was troubled by delays attributed to the 530 km (330 mi) of wiring in each aircraft. Airbus cited as underlying causes the complexity of the cabin wiring (100,000 wires and 40,300 connectors), its concurrent design and production, the high degree of customisation for each airline, and failures of configuration management and change control. Specifically, it would appear that German and Spanish Airbus facilities continued to use CATIA version 4, while British and French sites migrated to version 5. This caused overall configuration management problems, at least in part because wiring harnesses manufactured using aluminium rather than copper conductors necessitated special design rules including non-standard dimensions and bend radii; these were not easily transferred between versions of the software.

Airbus announced the first delay in June 2005 and notified airlines that deliveries would be delayed by six months. This reduced the total number of planned deliveries by the end of 2009 from about 120 to 90–100. On 13 June 2006, Airbus announced a second delay, with the delivery schedule undergoing an additional shift of six to seven months. Although the first delivery was still planned before the end of 2006, deliveries in 2007 would drop to only 9 aircraft, and deliveries by the end of 2009 would be cut to 70–80 aircraft. The announcement caused a 26% drop in the share price of Airbus's parent, EADS, and led to the departure of EADS CEO Noël Forgeard, Airbus CEO Gustav Humbert, and A380 programme manager Charles Champion. On 3 October 2006, upon completion of a review of the A380 program, the CEO of Airbus, Christian Streiff, announced a third delay, pushing the first delivery to October 2007, to be followed by 13 deliveries in 2008, 25 in 2009, and the full production rate of 45 aircraft per year in 2010. The delay also increased the earnings shortfall projected by Airbus through 2010 to €4.8 billion.

A380 in original Airbus livery

As Airbus prioritised the work on the A380-800 over the A380-800F, freighter orders were cancelled by FedEx and UPS, or converted to A380-800 by Emirates and ILFC. Airbus suspended work on the freighter version, but said it remained on offer, albeit without a service entry date. For the passenger version Airbus negotiated a revised delivery schedule and compensation with the 13 customers, all of which retained their orders with some placing subsequent orders, including Emirates, Singapore Airlines, Qantas, Air France, Qatar Airways, and Korean Air.

On 13 May 2008 Airbus announced reduced deliveries for the years 2008 (12) and 2009 (21). After further manufacturing setbacks, Airbus reduced plans to deliver 14 A380s in 2009, down from the previously revised target of 18. A total of 10 A380s were delivered in 2009. In 2010 Airbus delivered only 18 of the expected 20 A380s, due to Rolls-Royce engine availability problems. Airbus plans to deliver "between 20 and 25" A380s in 2011 before ramping up to three a month in 2012.

Entry into service

A Singapore Airlines A380 lines up for take-off at Zurich Airport.

The first aircraft delivered (MSN003, registered 9V-SKA) was handed over to Singapore Airlines on 15 October 2007 and entered into service on 25 October 2007 with an inaugural flight between Singapore and Sydney (flight number SQ380). Passengers bought seats in a charity online auction paying between $560 and $100,380. Two months later, Singapore Airlines CEO Chew Choong Seng said that the A380 was performing better than both the airline and Airbus had anticipated, burning 20% less fuel per passenger than the airline's existing 747-400 fleet. Emirates was the second airline to take delivery of the A380 on 28 July 2008 and started flights between Dubai and New York on 1 August 2008. Qantas followed on 19 September 2008, starting flights between Melbourne and Los Angeles on 20 October 2008. By the end of 2008, 890,000 passengers had flown on 2,200 A380 flights totalling 21,000 hours.

In February 2009 the millionth A380 passenger flying with Singapore Airlines was recorded. In May 2009 it was reported that the A380 had carried 1.5 million passengers during 41 thousand flight hours and 4200 flights. Air France received their first A380 on 30 October 2009, arriving at Charles de Gaulle Airport. Lufthansa received its first A380 on 19 May 2010. By July 2010 the 31 A380s then in service had flown 156,000 hours with passengers in 17,000 flights, transporting 6,000,000 passengers between 20 international destinations. On 2 June 2011 Korean Air became the sixth airline to add the aircraft to its fleet when it received its first aircraft which started service on the June 16, 2011.

Design

Overview

The A380 cabin cross section, showing economy class seating

The new Airbus was initially offered in two models. The A380-800 original configuration carried 555 passengers in a three-class configuration or 853 passengers (538 on the main deck and 315 on the upper deck) in a single-class economy configuration. In May 2007 Airbus began marketing a configuration with 30 fewer passengers, now 525 passengers in three classes, traded for 370 km (200 nmi) more range, to better reflect trends in premium class accommodation. The design range for the −800 model is 15,400 km (8,300 nmi); capable of flying for example from Hong Kong to New York, or from Sydney to Istanbul non-stop. The second model, the A380-800F freighter, would carry 150 tonnes of cargo 10,400 km (5,600 nmi). The −800F development was put on hold as Airbus prioritised the passenger version and all cargo orders were cancelled. Future variants may include an A380-900 stretch seating about 656 passengers (or up to 960 passengers in an all economy configuration) and an extended range version with the same passenger capacity as the A380-800.

“	The lack of engine noise – it's 50% quieter than a 747-400 on takeoff – was downright eerie. The A380 is so big it's difficult to sense its speed, and its upper deck is so far away from the engines the noise dissipates.	”
—TIME

The A380's wing is sized for a maximum take-off weight (MTOW) over 650 tonnes in order to accommodate these future versions, albeit with some strengthening required. The stronger wing (and structure) will be used on the A380-800F freighter. This common design approach sacrifices some fuel efficiency on the A380-800 passenger model, but Airbus estimates that the size of the aircraft, coupled with the advances in technology described below, will provide lower operating costs per passenger than the 747-400 and older 747 variants. The A380 also features wingtip fences similar to those found on the A310 and A320 to alleviate the effects of induced drag, increasing fuel efficiency and performance.

  

Flight deck

 

A380 flight deck

Airbus used similar cockpit layout, procedures and handling characteristics to those of other Airbus aircraft, to reduce crew training costs. Accordingly, the A380 features an improved glass cockpit, and fly-by-wire flight controls linked to side-sticks. The improved cockpit displays feature eight 15-by-20 cm (5.9-by-7.9 in) liquid crystal displays, all of which are physically identical and interchangeable; comprising two Primary Flight Displays, two navigation displays, one engine parameter display, one system display and two Multi-Function Displays. These MFDs are new with the A380, and provide an easy-to-use interface to the flight management system—replacing three multifunction control and display units. They include QWERTY keyboards and trackballs, interfacing with a graphical "point-and-click" display navigation system.

Engines

A Rolls-Royce Trent 900 engine on the wing of an Airbus A380

The A380 can be fitted with two types of engines: A380-841, −842 and −843F with Rolls-Royce Trent 900, and A380-861 and −863F with Engine Alliance GP7000 turbofans. The Trent 900 is a derivative of the Trent 800, and the GP7000 has roots from the GE90 and PW4000. The Trent 900 core is a scaled version of the Trent 500, but incorporates the swept fan technology of the stillborn Trent 8104. The GP7200 has a GE90-derived core and PW4090-derived fan and low-pressure turbo-machinery. Only two of the four engines are fitted with thrust reversers.

Noise reduction was an important requirement in the A380's design, and particularly affects engine design. Both engine types allow the aircraft to achieve QC/2 departure and QC/0.5 arrival noise limits under the Quota Count system set by London Heathrow Airport, which is a key destination for the A380.

The A380 was used to demonstrate the viability of a synthetic fuel comprising standard jet fuel with a natural-gas-derived component. On 1 February 2008, a three hour test flight operated between Britain and France, with one of the A380's four engines using a mix of 60% standard jet kerosene and 40% gas to liquids (GTL) fuel supplied by Shell. The aircraft needed no modification to use the GTL fuel, which was designed to be mixed with normal jet fuel. Sebastien Remy, head of Airbus SAS's alternative fuel programme, said the GTL used was no cleaner in CO₂ terms than standard fuel but it had local air quality benefits because it contains no sulphur.

A planform view of an Airbus A380 belonging to Singapore Airlines

Advanced materials

While most of the fuselage is aluminium, composite materials comprise more than 20% of the A380's airframe. Carbon-fibre reinforced plastic, glass-fibre reinforced plastic and quartz-fibre reinforced plastic are used extensively in wings, fuselage sections (such as the undercarriage and rear end of fuselage), tail surfaces, and doors. The A380 is the first commercial airliner to have a central wing box made of carbon fibre reinforced plastic. It is also the first to have a smoothly contoured wing cross section. The wings of other commercial airliners are partitioned span-wise into sections. This flowing, continuous cross section optimises aerodynamic efficiency. Thermoplastics are used in the leading edges of the slats. The new material GLARE (GLAss-REinforced fibre metal laminate) is used in the upper fuselage and on the stabilisers' leading edges. This aluminium-glass-fibre laminate is lighter and has better corrosion and impact resistance than conventional aluminium alloys used in aviation. Unlike earlier composite materials, it can be repaired using conventional aluminium repair techniques. Newer weldable aluminium alloys are also used. This enables the widespread use of laser beam welding manufacturing techniques — eliminating rows of rivets and resulting in a lighter, stronger structure.

Avionics architecture

Front fuselage view of A380

The A380 employs an Integrated Modular Avionics (IMA) architecture, first used in advanced military aircraft, such as the F-22 Raptor, F-35, and Dassault Rafale. The main IMA systems on the A380 were developed by Thales Group. Designed and developed by Airbus, Thales and Diehl Aerospace, the IMA suite is first used on the A380. The suite is a technological innovation, with networked computing modules to support different applications.

Together with IMA, the A380 avionics are highly networked. The data communication networks use Avionics Full-Duplex Switched Ethernet, following the ARINC 664 standard. The data networks are switched, full-duplex, star-topology and based on 100baseTX fast-Ethernet. This reduces the amount of wiring required and minimises latency.

The Network Systems Server (NSS) is the heart of A380 paperless cockpit. It eliminates the bulky manuals and charts traditionally carried by pilots; the NSS has enough inbuilt robustness to eliminate onboard backup paper documents. The A380's network and server system stores data and offers electronic documentation, providing a required equipment list, navigation charts, performance calculations, and an aircraft logbook. All are accessible to the pilot from two additional 27 cm (11 in) diagonal LCDs, each controlled by its own keyboard and cursor control device mounted in the foldable table in front of each pilot.

Systems

The A380-800 layout with 519 seats displayed

Power-by-wire flight control actuators are used for the first time in civil service to back up the primary hydraulic flight control actuators. During certain manoeuvres, they augment the primary actuators. They have self-contained hydraulic and electrical power supplies. They are used as electro-hydrostatic actuators (EHA) in the aileron and elevator, electric and hydraulic motors to drive the slats as well as electrical backup hydrostatic actuators (EBHA) for the rudder and some spoilers.

The aircraft's 350 bar (35 MPa or 5,000 psi) hydraulic system is an improvement over the typical 210 bar (21 MPa or 3,000 psi) system found in other commercial aircraft since the 1940s. First used in military aircraft, higher pressure hydraulics reduce the size of pipelines, actuators and other components for overall weight reduction. The 350 bar pressure is generated by eight de-clutchable hydraulic pumps. Pipelines are typically made from titanium and the system features both fuel and air-cooled heat exchangers. The hydraulics system architecture also differs significantly from other airliners. Self-contained electrically powered hydraulic power packs serve as backups for the primary systems, instead of a secondary hydraulic system, saving weight and reducing maintenance.

The A380 uses four 150 kVA variable-frequency electrical generators, eliminating constant speed drives and improving reliability. The A380 uses aluminium power cables instead of copper for weight reduction. The electrical power system is fully computerised and many contactors and breakers have been replaced by solid-state devices for better performance and increased reliability.

The A380 features a bulbless illumination system. LEDs are employed in the cabin, cockpit, cargo and other fuselage areas. The cabin lighting features programmable multi-spectral LEDs capable of creating a cabin ambience simulating daylight, night, or levels in between. On the outside of the aircraft, HID lighting is used for brighter, whiter illumination.

The A380 was initially planned without thrust reversers, as Airbus designed the aircraft with ample braking capacity to not require their use. However Airbus elected to fit the two inboard engines with thrust reversers in a late stage of development. The two outboard engines do not have reversers, reducing the amount of debris stirred up during landing. The A380 features electrically actuated thrust reversers, giving them better reliability than their pneumatic or hydraulic equivalents, in addition to saving weight.

Passenger provisions

Onboard features expected to reduce travel fatigue include a quieter interior and greater cabin air pressure than prior aircraft; the A380 produces 50% less cabin noise than the 747-400 and is pressurised to the equivalent of 1,520 m (5,000 ft) altitude versus 2,440 m (8,000 ft) on the 747-400. The A380 has 50% more cabin area and volume, larger windows, bigger overhead bins, and 60 cm (2.0 ft) extra headroom versus the 747-400. Seating options range from 4-abreast in first class up to 11-across in economy. In an industry where economy seats range from 41.5 cm (16.3 in) to 52.3 cm (20.6 in) in width, A380 economy seats are up to 48 cm (19 in) wide in a 10-abreast configuration on the main deck. The 10-abreast configuration on the 747-400 typically results in seats 44.5 cm (17.5 in) wide.

The A380's full-length upper and lower decks are connected by two stairways, fore and aft, wide enough to accommodate two passengers side-by-side; this cabin arrangement allows multiple seat configurations. The maximum certified carrying capacity is 853 passengers in an all-economy-class layout, and Airbus lists the typical three-class layout as accommodating 525 passengers, with 10 first, 76 business, and 439 economy class seats. Planned and announced configurations go from 407 passengers, for Korean Air, up to 840 passengers, for Air Austral.

Business class on the first Singapore Airlines A380

Airbus's initial publicity stressed the comfort and space of the A380's cabin, and advertised the installation of relaxation areas such as bars, beauty salons, duty-free shops, and restaurants. Proposed amenities resembled those installed on earlier airliners, particularly 1970s wide-body jets, which largely gave way to regular seats for more passenger capacity. Airbus later acknowledged that some publicised cabin proposals were unlikely to be installed, and noted that it was ultimately up to the airlines to configure the interior. Industry analysts suggested that the customisation options on the planes slowed down production speeds and raised costs. Due to delivery delays, Singapore Airlines and Air France debuted new seat designs on different aircraft before their installation on the A380.

Initial operators typically configured their A380s for three-class service, while adding extra features for passengers in premium cabins. Launch customer Singapore Airlines debuted partly-enclosed first class suites on its A380s in 2007, each featuring a leather seat with a separate bed; center suites could to be joined to create a double bed. A year later, Qantas debuted a new first class seat-bed and a sofa lounge at the front of the upper deck on its A380s. In late 2008, Emirates introduced "shower spas" in first class on its A380s, along with a bar lounge and seating area on the upper deck, and in 2009 Air France unveiled an upper deck electronic art gallery. In addition to lounge areas, some A380 operators have installed amenities consistent with other aircraft in their respective fleets, including self-serve snack bars, premium economy sections, and redesigned business class seating.

Integration with infrastructure and regulations

 

Ground operations

The A380's 20-wheel main landing gear

In the 1990s, aircraft manufacturers were planning to introduce larger planes than the Boeing 747. In a common effort of the International Civil Aviation Organization, ICAO, with manufacturers, airports and its member agencies, the "80-metre box" was created, the airport gates allowing planes up to 80 m (260 ft) wingspan and length to be accommodated. Airbus designed the A380 according to these guidelines, and to operate safely on Group V runways and taxiways, and while the U.S. FAA opposed this at an early stage, in July 2007, the FAA and EASA agreed to let the A380 operate on 45 m runways without restrictions. The A380-800 is approximately 30% larger in overall size than the 747-400, and can land or take off on any runway that can accommodate a 747. Runway lighting and signage may need changes to provide clearance to the wings and avoid blast damage from the engines and taxiway shoulders may be required to be stabilised to reduce the likelihood of foreign object damage caused to (or by) the outboard engines, which overhang more than 25 m (82 ft) from the centre line of the aircraft.

A380 being serviced by three separate jetways at Frankfurt Airport: two for the main deck and one for the upper deck.

Airbus measured pavement loads using a 540-tonne (595 short tons) ballasted test rig, designed to replicate the landing gear of the A380. The rig was towed over a section of pavement at Airbus' facilities that had been instrumented with embedded load sensors. It was determined that the pavement of most runways will not need to be reinforced despite the higher weight, as it is distributed on more wheels than in other passenger aircraft with a total of 22 wheels. The A380 landing gear is in a similar layout as the 747, except for four more wheels via the incorporation of six wheels on each main body gear.

The A380 requires service vehicles with lifts capable of reaching the upper deck, as well as tractors capable of handling the A380's maximum ramp weight. Using two jetway bridges the boarding time is 45 min, using an extra jetway to the upper deck it is reduced to 34 min. The A380 test aircraft have participated in a campaign of airport compatibility testing to verify the modifications already made at several large airports, visiting a number of airports around the world.

Takeoff and landing separation

In 2005, the ICAO recommended that provisional separation criteria for the A380 on takeoff and landing be substantially greater than for the 747 because preliminary flight test data suggested a stronger wake turbulence. These criteria were in effect while the ICAO's wake vortex steering group, with representatives from the JAA, Eurocontrol, the FAA, and Airbus, refined its 3-year study of the issue with additional flight testing. In September 2006, the working group presented its first conclusions to the ICAO.

In November 2006, the ICAO issued new interim recommendations. Replacing a blanket 10 nautical miles (19 km) separation for aircraft trailing an A380 during approach, the new distances were 6 nmi (11 km), 8 nmi (15 km) and 10 nmi (19 km) respectively for non-A380 "Heavy", "Medium", and "Light" ICAO aircraft categories. These compared with the 4 nmi (7.4 km), 5 nmi (9.3 km) and 6 nmi (11 km) spacing applicable to other "Heavy" aircraft. Another A380 following an A380 should maintain a separation of 4 nmi (7.4 km). On departure behind an A380, non-A380 "Heavy" aircraft are required to wait two minutes, and "Medium"/"Light" aircraft three minutes for time based operations. The ICAO also recommends that pilots append the term "Super" to the aircraft's callsign when initiating communication with air traffic control, in order to distinguish the A380 from "Heavy" aircraft.

In August 2008, the ICAO issued revised approach separations of 4 nmi (7.4 km) for Super (another A380), 6 nmi (11 km) for Heavy, 7 nmi (13 km) for medium/small, and 8 nmi (15 km) for light.

Future variants

Improved A380-800

Emirates, the largest A380 customer, has ordered a higher weight A380-800 variant.

From 2013, Airbus will offer, as an option, improved maximum take-off weight, thus providing a better payload/range performance. Maximum take-off weight is increased by 4 t (8,800 lb), to 573 t (1,260,000 lb) and an additional 190 km (100 nmi) in range. The increases are made possible by optimising the fly-by-wire control laws to reduce flight loads. British Airways and Emirates will be the first customers to receive this new option. Vietnam Airlines has shown interest in the higher-weight variant.

A380-900

In November 2007, Airbus top sales executive and chief operating officer John Leahy confirmed plans for an enlarged variant, the A380-900, which would be slightly longer than the A380-800 (79.4–73 m or 260–240 ft). This version would have a seating capacity of 650 passengers in standard configuration, and approximately 900 passengers in economy-only configuration. In May 2010, Airbus announced that A380-900 development was postponed, until production of the A380-800 has stabilised. Airlines that have expressed interest in the model include Emirates, Virgin Atlantic, Cathay Pacific, Air France-KLM, Lufthansa, Kingfisher Airlines, as well as the leasing company ILFC.

A380-800 freighter

Airbus originally accepted orders for the freighter version, offering the second largest payload capacity of any cargo aircraft, exceeded only by the Antonov An-225. However, production has been suspended until the A380 production lines have settled with no firm availability date.

 

Market

Prototype at the 2005 Paris Air Show

In 2006, industry analysts Philip Lawrence of the Aerospace Research Centre in Bristol and Richard Aboulafia of the consulting Teal Group in Fairfax anticipated 880 and 400 A380 sales respectively by 2025. According to Lawrence, parallel to the design of the A380, Airbus conducted the most extensive and thorough market analysis of commercial aviation ever undertaken, justifying its VLA (very large aircraft, those with more than 400 seats) plans, while according to Aboulafia, the rise of mid-size aircraft and market fragmentation reduced VLAs to niche market status, making such plans unjustified. The two analysts' market forecasts differed in the incorporation of spoke-hub and point-to-point models.

In 2007, Airbus estimated a demand for 1,283 passenger planes in the VLA category for the next 20 years if airport congestion remains at the current level. According to this estimate, demand could reach up to 1,771 VLAs if congestion increases. Most of this demand will be due to the urbanisation and rapid economic growth in Asia. The A380 will be used on relatively few routes, between the most saturated airports. Airbus also estimates a demand for 415 freighters in the category 120-tonne plus. Boeing, which offers the only competition in that class, the 747-8, estimates the demand for passenger VLAs at 590 and that for freighter VLAs at 370 for the period 2007–2026.

At one time the A380 was considered as a potential replacement for the existing Boeing VC-25 serving as Air Force One, but in January 2009 EADS declared that they were not going to bid for the contract, as assembling only three planes in the US would not make financial sense.

As of February 2011^[update] there were 244 orders for the A380-800. The break-even for the A380 was initially supposed to be reached at 270 units, but due to the delays and the falling exchange rate of the US dollar, it increased to 420 units. In 2010, EADS CFO Hans Peter Ring said that break-even (on the aircraft that are delivered) could be achieved as early as 2015, despite the delays; there should be around 200 deliveries by that time, on current projections. As of March 2010^[update] the average list price of an A380 was US$ 375.3 million (about €360 million or £229 million), depending on equipment installed.

Orders and deliveries

Airbus A380 firm net orders and deliveries (cumulative by year)

Eighteen customers have ordered the A380, including one VIP order by Airbus Executive and Private Aviation. Total orders for the A380 stand at 234 as of 31 May 2011. The biggest customer is Emirates, which in June 2010 increased its order by 32 aircraft to 90 total, or nearly 40% of all A380 orders at the time. A total of 27 orders originally placed for the freighter version, A380-800F, were either cancelled (20) or converted to A380-800 (7), following the production delay and the subsequent suspension of the freighter program.

Delivery takes place in Hamburg for customers from Europe and the Middle East and in Toulouse for customers from the rest of the world.

Commercial operators

Air France

Lufthansa Airbus A380 being towed to the hangar after testing, ready for its first scheduled flight on 6 June 2010 from Frankfurt to Johannesburg.

Korean Air takes delivery of its first Airbus A380 at Toulouse-Blagnac Airport, France, 25 May 2011.

The following table lists airlines whose A380 aircraft have commenced commercial passenger flights. It does not include operators that have ordered A380s or taken delivery of or announced details of inaugural flights but not yet commenced commercial passenger flights. Emirates is currently the largest operator of the A380 with 15 in service of its 90 on order, itself the largest amount of any carrier. The shortest route that the A380 flies regularly is from Dubai to Jeddah with Emirates for a flight time of only 3 hours, although Air France has also operated the A380 on the even shorter Paris to London route during summer 2010.

Airline	First commercial flight
Air France	2009112020 November 2009
Emirates	200808011 August 2008
Korean Air	2011061717 June 2011
Lufthansa	201006066 June 2011
Qantas	2008102020 October 2008
Singapore Airlines	2007102525 October 2007

 

Incidents and accidents

The A380 had been involved in one significant aviation incident as of 20 July 2011 (2011 -07-20)^[update].

• On 4 November 2010, Qantas Flight 32, en route from Singapore Changi Airport to Sydney Airport, suffered an uncontained engine failure, resulting in a series of related problems, and forcing the flight to return to Singapore. There were no injuries to the passengers, crew or people on the ground despite debris falling onto the Indonesian island of Batam. Qantas subsequently grounded all of its A380s that day subject to an internal investigation taken in conjunction with the engine manufacturer Rolls-Royce plc. Other operators of Rolls-Royce-powered A380s were also affected. Investigators later determined the cause of the explosion to be an oil leak in the Trent 900 engine.

Specifications

Measurement	A380-800	A380-800F
Cockpit crew	Two
Seating capacity	525 (3-class) 644 (2-class) 853 (1-class)	12 couriers
Length overall	72.73 m (238.6 ft)
Wingspan	79.75 m (261.6 ft)
Height	24.45 m (80.2 ft
Wheelbase	33.58 m (110.2 ft) wing landing gear 36.85 m (120.9 ft) body landing gear
Wheel track	12.46 m (40.9 ft)
Outside fuselage width	7.14 m (23.4 ft)
Outside fuselage height	8.41 m (27.6 ft)
Maximum cabin width	6.58 m (21.6 ft) Main deck 5.92 m (19.4 ft) Upper deck (floor level)
Cabin length	49.9 m (164 ft) Main deck 44.93 m (147.4 ft) Upper deck
Wing area	845 m2 (9,100 sq ft)
Aspect ratio	7.5
Wing sweep	33.5°
Maximum taxi/ramp weight	571,000 kg (1,260,000 lb)	592,000 kg (1,310,000 lb)
Maximum take-off weight	569,000 kg (1,250,000 lb)	590,000 kg (1,300,000 lb)
Maximum landing weight	391,000 kg (860,000 lb)	427,000 kg (940,000 lb)
Maximum zero fuel weight	366,000 kg (810,000 lb)	402,000 kg (890,000 lb)
Typical Operating empty weight	276,800 kg (610,000 lb)	252,200 kg (556,000 lb)
Maximum structural payload	89,200 kg (197,000 lb)	149,800 kg (330,000 lb)
Maximum cargo volume	176 m3 (6,200 cu ft	1,134 m3 (40,000 cu ft)
Maximum operating speed at cruise altitude	Mach 0.89 (945 km/h, 587 mph, 510 knots)
Maximum design speed in dive at cruise altitude	Mach 0.96 (at cruise altitude: 1020 km/h, 634 mph, 551 knots)
Take off run at MTOW/SL ISA	2,750 m (9,020 ft)	2,900 m (9,500 ft)
Range at design load	15,400 km (8,300 nmi, 9,500 mi)	10,400 km (5,600 nmi, 6,400 mi)
Service ceiling	13,115 m (43,028 ft)
Maximum fuel capacity	323,546 L (85,472 US gal)	310,000 L (81,893 US gal), 323,546 L (85,472 US gal) option
Engines (4 x)	GP7270 (A380-861) Trent 970/B (A380-841) Trent 972/B (A380-842)	GP7277 (A380-863F) Trent 977/B (A380-843F)
Thrust (4 x)	311 kN (70,000 lbf) – 355 kN (80,000 lbf)