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Traffic collision avoidance systemFrom Wikipedia, the free encyclopedia

A traffic collision avoidance system ortraffic alert and collision avoidance system (both

abbreviated as TCAS) is an aircraft collision avoidance system designed to reduce the incidence

ofmid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft

equipped with a corresponding active transponder, independent ofair traffic control, and warns

pilots of the presence of other transponder-equipped aircraft which may present a threat ofmid-aircollision (MAC). It is a type ofairborne 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 5,700 kg (13,000 lb) or authorized to carry more than 19 passengers.

ACAS / TCAS is based on secondary surveillance radar(SSR) transpondersignals, and operates

independently of ground-based equipment to provide advice to the pilot on potential conflicting

aircraft.

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).

Research into collision avoidance systems has been ongoing since at least the 1950s. ICAO and aviation authorities such as the FederalAviation Administration were spurred into action after several major mid-air collisions involving great loss of life.[1][2] Some of these mid-air

accidents include:

The Grand Canyon mid-air collision in 1956;

The New York air disasterin 1960;

TheAsheville midair collision in 1967;

The Zagreb mid-air collision in 1976;

The PSA Flight 182 collision with a Cessna 172 in 1978;

The Ukraine Aeroflot mid-air collision, between two Tupolev Tu-134, in 1979;

The Cerritos mid-air collision in 1986 (a case similar to PSA Flight 182), which finally spurred the US Congress and other regulatory bodies

into action and led to mandatory collision avoidance equipment;

The Charkhi Dadri mid-air collision over a town nearNew 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, whichinclude:

The Japan Airlines near-miss incident in 2001;

The berlingen 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

Traffic collision avoidance system

TCAS and IVSI cockpit display (monochrome)

TCAS and EHSI cockpit display (color)

Contents

1 Impetus for a collision prevention system

2 TCAS basics

2.1 System description

2.2 System components

3 TCAS operation

3.1 TCAS operation modes

3.2 TCAS alerts

3.3 Types of traffic and resolution advisories

3.4 Pilot/aircrew interaction during a TCAS event

4 Safety aspects of TCAS

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

6 Drawbacks to TCAS and ADS-B

7 Versions of TCAS

7.1 Passive7.2 TCAS I

7.3 TCAS II

7.4 TCAS III

7.5 TCAS IV

8 Current implementation

8.1 Current TCAS Limitations

8.2 Regulatory situation around the world

9 See also

10 References

11 External links

Impetus for a collision prevention system [edit]

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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;

For more examples, seeCategory:Mid-air collisions.

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 MHzradio

frequency), and all other aircraft reply to other interrogations (via 1,090 MHz). This interrogation -and-response cycle may occur several times per

second.[1][2]

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. [1][2]

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.

A TCAS installation consists of the following components:[1][2]

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.[3]

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.[1][2]

TCAS basics [edit]

System description [edit]

System components [edit]

TCAS operation[edit]

TCAS operation modes [edit]

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TCAS II can be currently operated in the following modes:[1][2]

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 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.[4]

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 controllers 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. [4]

TCAS alerts [edit]

TCAS II typical envelope

Types of traffic and resolution advisories [edit]

Type Text Meaning Required action[1][2][5]

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 15002000 ft/min

RA Descend. Descend. Intruder will pass above. Begin descending at 15002000 ft/min

RA Increase climb. Intruder will pass just below Climb at 25003000 ft/min.

RA Increase descent. Intruder will pass just above. Descend at 25003000 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.

RAMaintain vertical speed;

maintain.Intruder will be avoided if vertical rate is maintained. Maintain current vertical rate.

RAAdjust 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 fl ight.

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Safety studies on TCAS estimate that the system improves safety in the airspace by a factor of between 3 and 5.[6]

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 aircrafts 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). [1][2]

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

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 [edit]

TCAS event interaction[4]

Aircrew Controller

Traffic advisory (TA)

Shall not maneuver 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, as long

as the pilot reported the TCAS 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 [edit]

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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.[7]

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. [8]

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.[9][10]

The major demonstrated problem of theADS-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. [8] Either approach increases channel traffic above the level sustainable for environments

such as the Los Angeles Basin.

See also:Portable Collision Avoidance System

Collision Avoidance systems which rely on transponderreplies 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).[citation needed]

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 forgeneral 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".[11]

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.[1][2]

As of 2006, the only implementation that meets the ACAS II standards set by ICAO[12] was Version 7.0 of TCAS II,[1] produced by three

avionics manufacturers: Rockwell Collins, Honeywell, and ACSS (Aviation Communication & Surveillance Systems; an L-3 Communications and

Thales Avionics company).

After the berlingen 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[13]) and EUROCAE. As a result, by 2008 the standards for Version 7.1 of TCAS II have been issued [14] and

published as RTCA DO-185B[3] (June 2008) and EUROCAE ED-143 (September 2008).

TCAS II Version 7.1[2] 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).[15] 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).;[16] 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

Relationship to automatic dependent surveillance-broadcast (ADS-B) [edit]

Drawbacks to TCAS and ADS-B [edit]

Versions of TCAS [edit]

Passive [edit]

TCAS I [edit]

TCAS II [edit]

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proposal CP116).[7][17]

Studies conducted forEurocontrol, using recently recorded operational data, indicate that currently the probability of a mid-air collision in

European airspace is 2.7 x 108[vague] 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. [17]

Although ACAS III is mentioned as a future system in ICAO Annex 10, ACAS III is unlikely to materialize due to difficulties the current

surveillance systems have with horizontal tracking. Currently, research is being conducted to develop a future collision avoidance system (under

the working name of ACAS X) [18].

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 horizontalas well as vertical manouevring directives to pilots. For instance, in a head-on situation, one aircraft might bedirected, "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.[19]

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.[20][21]

TCAS IV uses additional information encoded by the target aircraft in the Mode S transponderreply (i.e. target encodes its own position into thetransponder signal) to generate a horizontal resolution to an RA. In addition, some reliable source of position (such as Inertial Navigation System

orGPS) 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 transponderreply 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 asADS-B development started.[21][22]

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/transponderupdates usually happen at a much slower rate than

the TCAS interrogations).[1][2] If one aircraft follows a TCAS RA and the other follows conflicting ATC instructions, a collision can occur, such as

the July 1, 2002 berlingen 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.[23]

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.[14][24][25]

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[26] and ETSO-C119c,[27] respectively) effective since

2009, based on the RTCA DO-185B[3] and EUROCAE ED-143 standards. On 25 September 2009 FAA issued Advisory Circular AC 20-151A[28]

providing guidance for obtaining airworthiness approval for TCAS II systems, including the new version 7.1. On 5 October 2009 theAssociation of

European Airlines (AEA) published a Position Paper[29] 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. [30] On 14 September 2010 EASA published the Comment Response Document (CRD) to the above

mentioned NPA.[31] 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.[17]

Among the system manufacturers, by February 2010 ACSS[32] certified Change 7.1 for their TCAS 2000 and Legacy TCAS II systems, [33] and

is currently offering Change 7.1 upgrade for their customers.[34] By June 2010 Honeywell published a white paper with their proposed solutions

for TCAS II Version 7.1.[35]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.[36]

TCAS III [edit]

TCAS IV [edit]

Current implementation [edit]

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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 ofFree 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 anADS-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 awarenessduring 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. [37]

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 ratheractualaircraft routing ( FMSflight 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.

TCAS requires that both conflicting aircraft have transponders. If one aircraft doesn't have a transponder, then it will not a lert TCAS as there

is no information being transmitted.The information TCAS receives isn't necessarily true. If a conflicting plane is transmitting a false altitude, TCAS will still treat the altitude as

correct and provide, or not provide, RA's based on that information.

To overcome some of these limitations, the FAA is developing a new collision avoidance logic based on dynamic programming.

In response to a series of midair collisions involving commercial airliners, Lincoln Laboratory was directed by the Federal Aviation Administration

in the 1970s to participate in the development of an onboard collision avoidance system. In its current manifestation, the Traffic Alert and

Collision Avoidance System is mandated worldwide on all large aircraft and has significantly improved the safety of air travel, but major changes

to the airspace planned over the coming years will require substantial modification to the system [38].

A set of new systems called ACAS X [39] will use this new logic:

ACAS Xa will be a direct replacement for TCAS II, using active surveillance

ACAS Xo will be collision avoidance tuned to work in some currently difficult operational situations, notably closely spaced parallel

approaches.

ACAS Xu will allow multiple sensor inputs and be optimised for unmanned airborne systems.ACAS Xp will be designed for aircraft with only passive surveillance (ADS-B).

The first FAA-scheduled industry was held in October 2011 in Washington DC, to brief avionics manufacturers on the development plans for

"ACAS X" - including flight demonstrations scheduled for fiscal 2013. The FAA says its work "will be foundational to the development of

minimum operational performance standards" for ACAS X by standards developer RTCA [40].

Current TCAS Limitations [edit]

This section does not cite any references or sources. Please help improve this section by adding

citations to reliable sources. Unsourced material may be challenged and removed. (January 2011)

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It is estimated that, if ACAS X will be further developed and certified, ACAS X will not be commercially available before mid 2020s. And it is said

to be unclear at this stage whether ACAS X would provide any horizontal resolutions [41].

Mid-air collision (MAC)

Gol Transportes Areos Flight 1907

1996 Charkhi Dadri mid-air collisionNovember 12, 1996

Bashkirian Airlines Flight 2937July 1, 2002

Bitching Betty

Ground Proximity Warning System

Portable Collision Avoidance System

1. ^ abcdefghijkIntroduction to TCAS II Version 7

2. ^ abcdefghijkIntroduction to TCAS II Version 7.1

3. ^ abcFAA DO-185 Materials and RTCA SC-147 Activities

4. ^ abcICAO Document 9863 - Chapter 6

5. ^Honeywell TCAS System User Manual

6. ^ACAS Programme Work Package 1

7. ^ abChange proposal CP116

8. ^ abADS-B System Description for the UAT

9. ^Potential cooperation between TCAS and ASAS

10. ^Terms of Reference - Future ADS-B / TCAS Relationships

11. ^FAA TCAS Home Page

12. ^ACAS II ICAO Provisions

13. ^SC-147 Terms of Reference - Revision 9

14. ^ abDecision criteria for regulatory measures on TCAS II version 7.1

15. ^Change proposal CP112E

16. ^Change proposal CP115

17. ^ abcEUROCONTROL - TCAS II Version 7.1

18. ^[1]

19. ^Project Report ATC-231

20. ^Skybrary ACAS

21. ^ abTCAS and Transponders

22. ^FAA Engineering Development Services Group - TCAS Support

23. ^BFU Investigation Report AX001-1-2/02

24. ^TCAS Safety Study - Collision r isk due to TCAS safety issues

25. ^TCAS Safety Study - Collision risk due to TCAS safety issues (Presentation)

26. ^FAA Technical Standard Order TSO-C119c

27. ^European Technical Standard Order ETSO-C119c

28. ^FAA Advisory Circular AC 20-151A - Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II), Versions 7.0 & 7.1 and

Associated Mode S Transponders

29. ^AEA Position Paper on TCAS Version 7.1 implementation

30. ^EASA Deviation Request #56

31. ^Comment Response Document (CRD) to NPA 2010-03

32. ^ACSS Change 7.1 for TCAS II

33. ^Press Release - ACSS Certifies Change 7.1 for TCAS 2000 and Legacy TCAS II

34. ^ACSS Change 7.1 for TCAS II flyer

Regulatory situation around the world [edit]

Jurisdiction (Agency) Classification of aircraft TCAS modeDate of

mandate

India(DGCA)Aeroplane having a maximum certified passenger seating configuration of

more than 30 seats or a maximum payload capacity of more than 3 tons[42]

TCAS II

31st

December,

1998

USA (FAA)All commercial turbine-powered transport aircraft with more than 30

passenger seats (or MTOW above 33,000 lb/15,000 kg)TCAS II 1 January 1993

Europe (EASA) All civil turbine-powered transport aircraft with more than 30 passenger

seats (or MTOW above 15,000 kg)[43]TCAS II 1 January 2000

Europe (EASA)All civil turbine powered transport aircraft with more than 19 passenger

seats (or MTOW above 5,700 kg)[43]ACAS II (Effectively

TCAS II Version 7.0)1 January 2005

Australia (CASA)All commercial turbine powered transport aircraft with more than 30

passenger seats (or MTOW above 15,000 kg)[44]TCAS II 1 January 2000

Hong Kong, China (Civil

Aviation Department)

All aircraft in Hong Kong with more than 9 passenger seats (or MTOW

greater than 5,700 kg)[45]TCAS II Version 7.0 1 January 2000

Brazil (National Civil

Aviation Agency)All transport category aircraft with more than 30 passenger seats TCAS II Version 7.0 1 January 2008

Peru (Direccin General

de Aeronutica Civil)

All civil turbine powered transport aircraft with more than 19 passenger

seats (or MTOW above 5,700 kg))[46][47]ACAS II (Effectively

TCAS II Version 7.0)1 January 2005

See also [edit]

References [edit]

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http://www.acss.com/Advertisements/Change%207-1%20Web%20page.pdfhttp://www.acss.com/SiteCollectionDocuments/Press%20Releases/Change%207-1%20TSO.pdfhttp://www.acss.com/change71https://easa.europa.eu/rulemaking/docs/crd/CRD%202010-03.pdfhttp://easa.europa.eu/certification/docs/deviation/ETSO%20DevP%2057.pdfhttp://hub.easa.europa.eu/crt/docs/viewcrdattachment/cid_41072/aid_460/fmd_3f25c67f0cd4b56f59cb31e18ad71a35http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2020-151A.pdfhttp://easa.europa.eu/ws_prod/g/doc/Agency_Mesures/Agency_Decisions/2009/cs_etso_5/Annex%20II%20-%20ETSO.pdfhttp://rgl.faa.gov/Regulatory_and_Guidance_Library/rgtso.nsf/0/95b393711426c9c78625759b006481ea/$FILE/TSO-C119c.pdfhttp://www.eurocontrol.int/msa/gallery/content/public/documents/acas/TCAS-SAF-T2-D08_v2.0.pdfhttp://www.eurocontrol.int/msa/gallery/content/public/documents/acas/TCAS-SAF-T2-D07_v1.2.pdfhttp://www.bfu-web.de/cln_003/nn_53140/EN/Publications/Investigation_20Report/2002/Report__02__AX001-1-2___C3_9Cberlingen__Report,templateId=raw,property=publicationFile.pdf/Report_02_AX001-1-2_%C3%9Cberlingen_Report.pdfhttp://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/nextgen/research_tech_dev/eng_dev_serv/tcas/http://yarchive.net/air/airliners/tcas.htmlhttp://www.skybrary.aero/index.php/ACAShttp://www.ll.mit.edu/mission/aviation/publications/publication-files/atc-reports/Burgess_1995_ATC-231_WW-15318.pdfhttp://www.eurocontrol.int/msa/public/standard_page/ACAS_Overview_Principles.html#typesacashttp://www.eurocontrol.int/msa/public/standard_page/ACAS_Upcoming_Changes.htmlhttp://adsb.tc.faa.gov/TCAS/CPs/CP115.pdfhttp://adsb.tc.faa.gov/TCAS/CPs/CP112E.pdfhttp://www.eurocontrol.int/msa/gallery/content/public/documents/SIRE+_WP7_69D_v1.2.pdfhttp://www.rtca.org/CMS_DOC/SC-147%20TOR%20Rev9%20-%20PMC%20Approved%20-%2006-10-2010.pdfhttp://www.eurocontrol.int/msa/public/standard_page/ACAS_ICAO_Provisions.htmlhttp://adsb.tc.faa.gov/TCAS.htmhttp://www.rtca.org/CMS_DOC/TOR%20-%20Initial%20-%20ADS-B%20-%20TCAS%20Relationship.pdfhttp://www.narcap.org/articles/hci_aero.pdfhttp://adsb.tc.faa.gov/WG5_Meetings/Meeting1/UAT-WP-1-09.pdfhttp://adsb.tc.faa.gov/TCAS/CPs/CP116.pdfhttp://www.eurocontrol.int/msa/gallery/content/public/documents/Safety/WP1.pdfhttp://www.sisadminov.net/tcas/docs/cas81_pilotguide.pdfhttp://www.eurocontrol.int/msa/gallery/content/public/documents/Doc9863_ACAS_Controller_Training_chp6_1.pdfhttp://adsb.tc.faa.gov/SC-147.htmhttp://www.faa.gov/documentLibrary/media/Advisory_Circular/TCAS%20II%20V7.1%20Intro%20booklet.pdfhttp://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/nextgen/research_tech_dev/eng_dev_serv/tcas/media/pdf/tcas.pdfhttp://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&action=edit&section=23http://en.wikipedia.org/wiki/Portable_Collision_Avoidance_Systemhttp://en.wikipedia.org/wiki/Ground_proximity_warning_systemhttp://en.wikipedia.org/wiki/Bitching_Bettyhttp://en.wikipedia.org/wiki/Bashkirian_Airlines_Flight_2937http://en.wikipedia.org/wiki/1996_Charkhi_Dadri_mid-air_collisionhttp://en.wikipedia.org/wiki/Gol_Transportes_A%C3%A9reos_Flight_1907http://en.wikipedia.org/wiki/Mid-air_collisionhttp://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&action=edit&section=22http://en.wikipedia.org/w/index.php?title=Directorate_General_of_Civil_Aviation_of_Peru&action=edit&redlink=1http://en.wikipedia.org/wiki/National_Civil_Aviation_Agency_of_Brazilhttp://en.wikipedia.org/wiki/Civil_Aviation_Department_(Hong_Kong)http://en.wikipedia.org/wiki/Civil_Aviation_Safety_Authorityhttp://en.wikipedia.org/wiki/European_Aviation_Safety_Agencyhttp://en.wikipedia.org/wiki/European_Aviation_Safety_Agencyhttp://en.wikipedia.org/wiki/FAAhttp://en.wikipedia.org/wiki/Directorate_General_of_Civil_Aviation_(India)http://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&action=edit&section=21

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35. ^Honeywell Solutions for TCAS II Change 7.1

36. ^Rockwell Collins Traffic surveillance products

37. ^http://www.airliners.net/aviation-forums/general_aviation/read.main/361350

38. ^ [www.ll.mit.edu/publications/journal/pdf/vol19_no1/19_1_1_Kochenderfer.pdf]

39. ^[2]

40. ^[3]

41. ^[4]

42. ^[5]

43. ^ abEuropean ACAS II Mandate

44. ^Explanatory Statement regarding TCAS for CASA(PDF)

45. ^Airworthiness Notice No. 24 (PDF)

46. ^DGAC Per - RAP 121 - Subpart K (PDF)

47. ^DGAC Per - RAP 135 - Subpart C (PDF)

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)

External links [edit]

Aircraft components and systemsVTE

Airframe structure

Cabane strutCanopyDopeCruciform tailEmpennageFairingFabric coveringFlying wiresFormerFuselageInterplane strutHardpoint

Horizontal stabilizerJury strutLeading edgeLift strutLongeronNacelleRear pressure bulkheadRibSparStabilizerStressed skin

TailplaneTrailing edgeT-tailTwin tailVertical stabilizerV-tailWingboxWing rootWing tip

Flight controls

AileronAirbrakeArtificial feelAutopilotCanardCentre stickDeceleronDive brakeElevatorElevonElectro-hydrostatic actuator

FlaperonFlight control modesFly-by-wireGust lockRudderServo tabSide-stickSpoilerSpoileronStabilatorStick pusherStick shaker

Trim tabYaw damperWing warpingYoke

Aerodynamic and high-liftdevices

Active Aeroelastic WingAdaptive Compliant WingBlown flapChannel wingDog-toothFlapGouge flapGurney flapKrueger flaps

Leading edge cuffLEXSlatsSlotStall stripsStrakeVariable-sweep wingVortex generatorVortilonWing fenceWinglet

Avionic and flightinstrumentsystems

ACASAir data computerAirspeed indicatorAltimeterAnnunciator panelAttitude indicatorCompassCourse deviation indicatorEFIS

EICASFlight data recorderFlight management systemGlass cockpitGPSHeading indicatorHorizontal situation indicatorINSTCAS

TransponderTurn and bank indicatorPitot-static systemRadar altimeterVertical Speed IndicatorYaw string

Propulsion controls,devices and fuel systems

AutothrottleDrop tankFADECFuel tankGascolatorInlet coneIntake rampNACA cowlingSelf-sealing fuel tankThrottleThrust lever

Thrust reversalTownend ringWetwing

Landing and arresting gear AutobrakeConventional landing gearArrestor hookDrogue parachuteLanding gear extenderOleo strutTricycle gearTundra tireUndercarriage

Escape systems Ejection seatEscape crew capsule

Other systemsAircraft lavatoryAuxiliary power unitBleed air systemDeicing bootEmergency oxygen systemEnvironmental Control System

Hydraulic systemIce protection systemLanding lightsNavigation lightPassenger service unitRam air turbineWeeping wing

Categories:

Lists relating to aviationVTE

GeneralAircraftmanufacturersAircraft enginesmanufacturersGlidersAirlinesdefunctAirportsCivil authoritiesMuseumsRegistration prefixes

RotorcraftmanufacturersTimeline

Military Air forcesWeaponsExperimentalMissilesUnmanned

Accidents/incidents Commercial airlinersby locationFatalitiesby death tollGeneral aviationMilitary

Records AirspeedAltitudeDistanceEnduranceFirstsLargeMost-produced aircraftMost-produced rotorcraft

Aircraft collision avoidance systems Aviation risks Avionics Warning systems

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http://www.rockwellcollins.com/Products_and_Systems/Radar_and_Surveillance/Traffic.aspxhttp://www.eurocontrol.int/msa/public/standard_page/ACAS_Equipage_Requirements.htmlhttp://www.mtc.gob.pe/portal/transportes/aereo/regulaciones/docs/rap_rev17/rap121/rap121_subparte_k_rev%2017.pdfhttp://www.mtc.gob.pe/portal/transportes/aereo/regulaciones/docs/rap_rev17/rap121/rap121_subparte_k_rev%2017.pdfhttp://www.mtc.gob.pe/portal/transportes/aereo/regulaciones/docs/rap_rev17/rap121/rap121_subparte_k_rev%2017.pdfhttp://www.mtc.gob.pe/portal/transportes/aereo/regulaciones/docs/rap_rev17/rap121/rap121_subparte_k_rev%2017.pdfhttp://www.mtc.gob.pe/portal/transportes/aereo/regulaciones/docs/rap_rev17/rap121/rap121_subparte_k_rev%2017.pdfhttp://www.mtc.gob.pe/portal/transportes/aereo/regulaciones/docs/rap_rev17/rap121/rap121_subparte_k_rev%2017.pdfhttp://en.wikipedia.org/w/index.php?title=Traffic_collision_avoidance_system&action=edit&section=24http://www.airsport-corp.com/adsb2.htmhttp://www.collisionavoidance.org/http://www.collisionavoidance.org/http://www.collisionavoidance.org/http://www.airsport-corp.com/adsb2.htmhttp://www.airsport-corp.com/adsb2.htmhttp://www.airsport-corp.com/adsb2.htmhttp://www.skybrary.aero/index.php/Solutions:TCAShttp://www.skybrary.aero/index.php/Solutions:TCAShttp://www.skybrary.aero/index.php/Solutions:TCAShttp://www.oilandgasuk.co.uk/downloadabledocs/284/c_Mark_%20Prior.pdfhttp://www.oilandgasuk.co.uk/downloadabledocs/284/c_Mark_%20Prior.pdfhttp://en.wikipedia.org/wiki/Horizontal_stabilizerhttp://en.wikipedia.org/wiki/Aircraft_canopyhttp://en.wikipedia.org/wiki/Aircraft_dopehttp://en.wikipedia.org/wiki/Cruciform_tailhttp://en.wikipedia.org/wiki/Cruciform_tailhttp://en.wikipedia.org/wiki/Empennagehttp://en.wikipedia.org/wiki/Horizontal_stabilizerhttp://en.wikipedia.org/wiki/Jury_struthttp://en.wikipedia.org/wiki/Jury_struthttp://en.wikipedia.org/wiki/Leading_edgehttp://en.wikipedia.org/wiki/Lift_struthttp://en.wikipedia.org/wiki/Longeronhttp://en.wikipedia.org/wiki/Nacellehttp://en.wikipedia.org/wiki/Nacellehttp://en.wikipedia.org/wiki/Rear_pressure_bulkheadhttp://en.wikipedia.org/wiki/Rib_(aircraft)http://en.wikipedia.org/wiki/Spar_(aviation)http://en.wikipedia.org/wiki/Spar_(aviation)http://en.wikipedia.org/wiki/Stabilizer_(aircraft)http://en.wikipedia.org/wiki/Stressed_skinhttp://en.wikipedia.org/wiki/Yaw_damperhttp://en.wikipedia.org/wiki/Wing_warpinghttp://en.wikipedia.org/wiki/Wing_warpinghttp://en.wikipedia.org/wiki/Yoke_(aircraft)http://en.wikipedia.org/wiki/Leading_edge_cuffhttp://en.wikipedia.org/wiki/Boeing_X-53_Active_Aeroelastic_Winghttp://en.wikipedia.org/wiki/Boeing_X-53_Active_Aeroelastic_Winghttp://en.wikipedia.org/wiki/Adaptive_Compliant_Winghttp://en.wikipedia.org/wiki/Rudderhttp://en.wikipedia.org/wiki/Servo_tabhttp://en.wikipedia.org/wiki/Side-stickhttp://en.wikipedia.org/wiki/Side-stickhttp://en.wikipedia.org/wiki/Side-stickhttp://en.wikipedia.org/wiki/Spoiler_(aeronautics)http://en.wikipedia.org/wiki/Spoileronhttp://en.wikipedia.org/wiki/Spoileronhttp://en.wikipedia.org/wiki/Spoileronhttp://en.wikipedia.org/wiki/Stabilatorhttp://en.wikipedia.org/wiki/Stabilatorhttp://en.wikipedia.org/wiki/Stabilatorhttp://en.wikipedia.org/wiki/Stick_pusherhttp://en.wikipedia.org/wiki/Stick_shakerhttp://en.wikipedia.org/wiki/Stick_shakerhttp://en.wikipedia.org/wiki/Blown_flaphttp://en.wikipedia.org/wiki/Channel_winghttp://en.wikipedia.org/wiki/Dog-toothhttp://en.wikipedia.org/wiki/Dog-toothhttp://en.wikipedia.org/wiki/Dog-toothhttp://en.wikipedia.org/wiki/Flap_(aircraft)http://en.wikipedia.org/wiki/Gouge_flaphttp://en.wikipedia.org/wiki/Gurney_flaphttp://en.wikipedia.org/wiki/Gurney_flaphttp://en.wikipedia.org/wiki/Gurney_flaphttp://en.wikipedia.org/wiki/Krueger_flapshttp://en.wikipedia.org/wiki/Krueger_flapshttp://en.wikipedia.org/wiki/Flight_instrumentshttp://en.wikipedia.org/wiki/Transponder_(aviation)http://en.wikipedia.org/wiki/Flight_data_recorderhttp://en.wikipedia.org/wiki/Flight_management_systemhttp://en.wikipedia.org/wiki/Annunciator_panelhttp://en.wikipedia.org/wiki/Attitude_indicatorhttp://en.wikipedia.org/wiki/Compasshttp://en.wikipedia.org/wiki/Course_deviation_indicatorhttp://en.wikipedia.org/wiki/Course_deviation_indicatorhttp://en.wikipedia.org/wiki/Course_deviation_indicatorhttp://en.wikipedia.org/wiki/Electronic_Flight_Instrument_Systemhttp://en.wikipedia.org/wiki/Pitot-static_systemhttp://en.wikipedia.org/wiki/Radar_altimeterhttp://en.wikipedia.org/wiki/Variometerhttp://en.wikipedia.org/wiki/Variometerhttp://en.wikipedia.org/wiki/Drop_tankhttp://en.wikipedia.org/wiki/FADEChttp://en.wikipedia.org/wiki/Fuel_tank#Aircrafthttp://en.wikipedia.org/wiki/Gascolatorhttp://en.wikipedia.org/wiki/Drogue_parachutehttp://en.wikipedia.org/wiki/Landing_gear_extenderhttp://en.wikipedia.org/wiki/Landing_gear_extenderhttp://en.wikipedia.org/wiki/Landing_gear_extenderhttp://en.wikipedia.org/wiki/Oleo_struthttp://en.wikipedia.org/wiki/Tricycle_gearhttp://en.wikipedia.org/wiki/Tundra_tireh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