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27 votes
Accepted

Are controllers aware of TCAS RA taking place?

ATC was and is still generally not aware of RAs before being informed by the pilot In general ATC is not aware of any RA occurring in aircraft, and is neither aware of the RA content. The crew informs ...
mins's user avatar
  • 74.4k
18 votes

What do the letters "h" and "i" next to TCAS ND symbols mean?

They mean the simulator or mockup is buggy and Wingdings 3 was missing / broken / not selected. There should be trend arrows there instead. First smoking gun: this appears to be a photo of either a ...
TypeIA's user avatar
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15 votes
Accepted

How is a conflict between aircraft with TCAS I and II resolved?

TCAS 1 will only give a Traffic Advisory (TA). The crew will lookout for the other aircraft and take evasive action if necessary. They also may contact ATC for instructions. They will follow ATC ...
DeltaLima's user avatar
  • 83.5k
15 votes
Accepted

Why is 5 seconds the time to respond to a TCAS RA?

If the pilot reacts at impact it is too late to avoid collision If the pilot reacts one second before impact it is too late to make any significant altitude change and to avoid collision. If the pilot ...
DeltaLima's user avatar
  • 83.5k
14 votes

How does a TCAS system avoid unnecessary (RAs) resolution advisories when aircraft are operating on separate closely spaced parallel runways?

The TCAS logic is adjusted when the aircraft is in the terminal area. It does this through the following inputs: Radio Altitude - Controls TCAS parameters when below 2350 feet AGL Landing Gear, Flaps,...
Gerry's user avatar
  • 19.9k
14 votes
Accepted

Was there a TCAS alert during the near miss at Austin TX, where a Boeing 737 was mistakenly cleared for takeoff in front of a 767?

Per the FAA booklet: Introduction to TCAS II, it does not alert against ground targets. The ground level estimate is then subtracted from the pressure altitude received from each Mode C equipped ...
BowlOfRed's user avatar
  • 5,611
13 votes
Accepted

What is the range of TCAS?

Short answer If a single range should be stated for ACAS II, it would be the reliable range of 14 NM, even if targets can displayed by current TCAS II up to 30/40 NM. Reliable means here: a track ...
mins's user avatar
  • 74.4k
13 votes

Why are both ATC and TCAS tasked to prevent collisions although TCAS takes precedence anyway?

While ATC's primary goal is to prevent collisions, it is also responsible for the efficient movement of aircraft through the airspace. That requires a strategic approach to managing air traffic to get ...
Gerry's user avatar
  • 19.9k
13 votes

Can a drone be seen on TCAS?

No, a drone will normally not be visible on an aircraft TCAS. The TCAS system is based entirely on direct communication between aircraft transponders, so both parties (aircraft and drone) must have a ...
60levelchange's user avatar
13 votes
Accepted

On an ADS-B In display, do the pilots see the squawk code or call sign for other aircraft?

ADS-B is part of a system that compromises a number of different things. ADS-B (In) means that your aircraft is capable of receiving the ADS-B data, FIS-B and TIS-B as well. FIS-B broadcasts ...
Ron Beyer's user avatar
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11 votes
Accepted

What action should the pilot take when a TCAS RA (Resolution Advisory) provides opposite guidance to ATC instructions?

In the 2002 Ɯberlingen mid-air collision, one crew followed the ATC instruction to descend instead of the TCAS Resolution Advisary to climb. This caused the deaths of 71 people. Equipment and ...
Mike Sowsun's user avatar
  • 37.8k
11 votes

How does the TCAS decide which aircraft to climb and which to descend

The threads linked in the comments provide an answer, but only when read in conjunction with each other. In isolation, for a level intruder, TCAS will produce a descent - which would tell the other ...
Ralph J's user avatar
  • 51.8k
10 votes

Can you have TCAS RA if your other traffic only have TCAS TA?

If both aircraft in an encounter are equipped with TCAS and are operating in TA/RA mode, then both will receive a coordinated RA. That is the RA will be coordinated between them using the Mode S ...
Gerry's user avatar
  • 19.9k
10 votes
Accepted

Can TCAS be used to confirm "traffic in sight"?

No, "in sight" or "visual contact" means seeing the actual traffic visually, with your eyes. When you report "traffic in sight," then the controllers are allowed to issue a clearance such as "maintain ...
Ralph J's user avatar
  • 51.8k
10 votes

If all aircraft were TCAS-equipped, how would this change ATC routines?

Think of the ATC system as the road network, traffic lights, road signs, and police. TCAS is a standalone device in your car that warns you the guy coming at right angles to the intersection in front ...
John K's user avatar
  • 132k
9 votes
Accepted

Does the RA (resolution Advisory) from TCAS II take into account the stall margin required?

Yes, but not directly. The TCAS is a generic box that doesn't really know anything about the aircraft performance. What it does have is a number of input discretes that allow other aircraft systems to ...
Gerry's user avatar
  • 19.9k
8 votes

Would TCAS ever issue a "climb, climb!" RA that would stall a jet with a low airspeed?

There is no more risk of stalling an aircraft from a TCAS alert than from being instructed verbally by ATC to climb to a higher altitude for traffic avoidance. Or, (in the case of slow flight at ...
Michael Hall's user avatar
  • 26.4k
8 votes
Accepted

Why does TCAS not issue turning commands as Resolution Advisory?

TCAS gets fairly accurate altitude information from the same source as the transponder. Thus any extrapolation from this information can yield a fairly accurate prediction of whether two aircraft may ...
fooot's user avatar
  • 73.4k
8 votes
Accepted

Why are both ATC and TCAS tasked to prevent collisions although TCAS takes precedence anyway?

TCAS is sort of a fallback, last-resort system used in case all else fails. TCAS works within the scope of what happens within the next minute or so, and will require the involved aircraft to perform ...
60levelchange's user avatar
8 votes
Accepted

In what scenario would a "climb, crossing climb" or "descend, crossing descend" be issued by a TCAS system?

When a TCAS RA is issued, the system first selects the sense (up or down) and then the required strength. During the sense decision, an altitude crossing is avoided if the required vertical separation ...
Bianfable's user avatar
  • 55.9k
7 votes

Is transponder required to turn off in formation flying?

See also: In a part 91 formation flight within a mode C veil, are all the aircraft required to have their transponders on? Yes, the transponder should be off/standby. From AIM 4-1-20-a-4-c (c) When ...
BowlOfRed's user avatar
  • 5,611
6 votes

Can a TCAS be alerted when the intruder aircraft has a transponder in stand-by mode?

No. If the intruder's transponder is in standby it will not respond to interrogations and will be invisible to the TCAS. TCAS can't act on targets it can't interrogate.
Gerry's user avatar
  • 19.9k
6 votes
Accepted

Do aircraft have radar or other forms of traffic sensing?

By far, most civil aircraft lack radar to display conflicting traffic, and certainly to enhance traffic situational awareness. TCAS and the use of ADS-B are the most effective tools for traffic ...
mongo's user avatar
  • 17.8k
6 votes

Could TCAS be used as a backup source for position, attitude or air data?

Can TCAS assist in dead reckoning? First, understand that TCAS runs off secondary (transponder) radar data. Essentially your aircraft with TCAS is like ATC radar, interrogating other transponders, ...
mongo's user avatar
  • 17.8k
6 votes

How is a conflict between aircraft with TCAS I and II resolved?

According to AC 120-55C, the TCAS II aircraft will issue a TA (Traffic Advisory) and an RA (Resolution Advisory) if necessary and the pilot should follow any RA immediately and safely. The TCAS I ...
RealAnswersNotAI's user avatar
6 votes
Accepted

Why does TCAS need 2 antennas?

Two antennas As @Ron mentioned the fuselage is an opaque obstacle for waves, and two antennas are required to cover the whole space around the aircraft. The choice is to have one antenna at the bottom ...
mins's user avatar
  • 74.4k
5 votes

What is the climb/descent rate that triggers the TCAS up/down arrow?

The Minimum Operational Performance Specifications (MOPS) for TCAS II (RTCA DO185B / EUROCAE ED143) specify the requirements for TCAS II. It states that the arrow must appear when the vertical speed ...
DeltaLima's user avatar
  • 83.5k
5 votes
Accepted

Is Auto Pilot capable of performing TCAS resolution advisory?

I know that there are certified TCAS/autopilot/FD systems (380 comes to mind), but the normal modality that I am familiar with is where TCAS alerts are provided to the pilot, who then decides what ...
mongo's user avatar
  • 17.8k
5 votes

Is Auto Pilot capable of performing TCAS resolution advisory?

Short answer is no. First of all it is resolution advisory as you said. Its purpose, is to make the Pilots aware of an imminent danger/conflict. As with 'Terrain, Terrain', 'Pull up!, Pull up!', it ...
Tas's user avatar
  • 336

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