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 ...
- 71k
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 ...
- 14.2k
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 ...
- 82.9k
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 ...
- 82.9k
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,...
- 19.4k
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 ...
- 5,551
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 ...
- 71k
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 ...
- 19.4k
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 ...
- 36.2k
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 ...
- 36k
12
votes
When receiving a TCAS RA, DESCEND DESCEND, and starting the descent, if a pilot received GPWS warning, TERRAIN, what would they do?
TCAS (II) does not give the descend RA below 1200 ft AGL while climbing or below 1000 ft AGL while descending.
Image from FAA Advisory Circular 20-151A Table 2
In case such an unlikely event happens ...
- 100k
11
votes
Accepted
What action should the pilot take when a TCAS RA (Resolution Advisory) provides opposite guidance to ATC instructions?
In the 2002 Überlingen 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 ...
- 37.5k
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 ...
- 19.4k
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 ...
- 49.8k
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 ...
- 126k
10
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 ...
- 49.8k
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 ...
- 19.4k
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 ...
- 71.8k
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 ...
- 24.9k
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 ...
- 36.2k
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 ...
- 54.3k
7
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.
- 19.4k
7
votes
When receiving a TCAS RA, DESCEND DESCEND, and starting the descent, if a pilot received GPWS warning, TERRAIN, what would they do?
I would pull up and once in a stable climbs I would turn in either direction in this situation. If I get a warning to descend it is to prevent a conflict with another aircraft, whereas a terrain ...
- 52.9k
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 ...
- 5,551
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 ...
- 6,725
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, ...
- 17.7k
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 ...
- 71k
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 ...
- 82.9k
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 ...
- 17.7k
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