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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 ATC using a phraseology described in ICAO Doc 4444 PANS-ATM, Chapter 12, Para 12.3.1.2:
When the RA occurs, and the crew must deviate from ATC instructions, ...
21
TCAS works by sending interrogations to other aircraft's transponders. The transponder will reply to the interrogation in a similar way it responds to radar. From the time difference between the interrogation and the reply, the distance to the other aircraft is calculated. The reply itself contains the altitude of the other aircraft.
The explanation below ...
19
First I'd just like to comment that "near miss" is a bad term (as falstro also noticed). It seems to say that the planes "nearly missed", implying they didn't miss. The FAA uses the terms "Near Midair Collision" (NMAC) for serious incidences, and "loss of separation" for less serious ones. As such, terms like "near miss", "close call", and "narrowly escaped ...
19
The FAA publishes Advisory Circular 20-151A, which says in section 2-17(a):
Because TCAS II can only accept a limited number of inputs related to
airplane performance, it’s not possible to automatically inhibit CLIMB
and INCREASE CLIMB RAs in all cases where it may be appropriate to
inhibit such RAs. In these cases, TCAS II may command maneuvers ...
17
TCAS can deal with conflicts with multiple aircraft, a so called Multiple Threat Encounter. It will attempt to resolve the conflict but it will be limited in its options.
Examples of a MTE are rare, one case I can point to is this incident involving an aircraft turning into the approach stream between two aircraft instead of following the last in line.
...
15
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 instructions unless they see that the instructions will bring them into the path of the other aircraft.
TCAS II will give a traffic advisory first, then a ...
14
The correct procedure for the interceptee would to follow the TCAS Resolution Advisory as they have generally no idea that they are being intercepted.
The interceptor must ensure that no TCAS RA is generated by switching his transponder to the appropriate mode. This has been standard procedure since the introduction of TCAS.
TCAS works by interrogating ...
13
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 transponder in order for TCAS to work. Normal drones do not have transponders, so they will not be visible on TCAS.
If a pilot reports a drone near the ...
13
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 information such as weather. TIS-B is a traffic broadcast system.
ADS-B includes a number of messages (about 27 different messages), including:
Aircraft Identification
...
12
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 (and is not an equipment malfunction), the best possible maneuver is to climb away from the incoming aircraft i.e. turn and climb to the side of the previous ...
12
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 can be established with a probability of at least 90 per cent for aircraft within the surveillance range. The reliable range of 14 NM is achievable with a ground ...
12
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 aircraft from point A to point B safely and in a timely manner. The primary tool ATC uses is the flight clearance.
If air crews follow their clearances ...
11
Well, #2 is actually surprisingly easy. At the top middle of the NTSB website, under "Other ways to Contact NTSB" there is an innocuous-looking link that says "Submit a TCAS Notification" (which has you send an email to tcas@ntsb.gov). Personally I'd follow that up with a phone call to the appropriate regional NTSB office as well, just to be sure you've ...
11
The TCAS responded to the other aircraft not following the flight profile that was observed earlier. If you watch closely, you will see that the other aircraft started to descend as well after the first resolution advisory is given.
The onboard TCAS responds by issuing the counter-movement to climb immediately.
The only thing that we do not know is what ...
10
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 visual separation" or "follow that traffic, cleared visual approach...". They can't issue those clearances when you only see the traffic on TCAS. In fact, ...
10
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 procedures have improved since then. Pilots should always follow TCAS Advisory and there is a FAA rule that deals with this. 91.123 Compliance with ATC clearances and ...
10
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 of you is going to run the light and T-bone you. Whether you have such a device or not, it doesn't change how the traffic control system work.
TCAS has ...
9
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 datalink.
If both aircraft in an encounter are equipped with TCAS and one is operating in TA/RA mode and the other in TA Only mode, the one operating in TA/RA ...
9
See below for a description of how the TCAS (Traffic Collision Avoidance System) display is showing another aircraft approaching in each frame:
900 feet below and climbing
800 feet below and climbing
The traffic advisory (TA) gives the pilots the chance to avoid or at least anticipate conflict
500 feet below and still climbing
The resolution advisory (RA)...
9
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 indicate that the aircraft climb performance is limited. Other discretes code the altitude above which the aircraft cannot perform an RA climb. What drives ...
8
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 approach speeds) to execute a go-around from an approach to land.
An aircraft can only be stalled if the critical angle of attack is exceeded. A TCAS alert to ...
8
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 collide, and provide more certainty that changes in altitude will avert any conflict.
Range information is obtained by measuring the round trip time of the ...
7
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 warning is to prevent impact with the ground. The ground is much bigger than another airplane, so the lower risk is collision with an aircraft. In other words, if I ...
7
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.
7
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 fairly extreme maneuvers to avoid a collision. TCAS has one single purpose: to ensure that two (or more) aircraft that have already gotten much too close will ...
6
I found a very interesting paper from 2007 that analyzed TCAS performance. They analyzed recorded data to come up with 1 RA per 116 flight hours.
Over this time period, monitoring took place for approximately 190
days, and roughly 200,000 Mode S flight hours were observed within the
sensor’s 60 nmi coverage area. We observed a total of 1725 RA events,
...
6
The TCAS standard uses the standard transponder, having the interrogator on board in addition to the transponder itself.
The aircraft periodically broadcasts the interrogation signal. The power is less than from the ground radar, but sufficient to trigger response from aircraft that may be less than a minute of flight.
The distance to the other aircraft is ...
6
The numbers aren't random, though at first glance the rationale may not be obvious.
Weight
5700 kilograms is (roughly) 12,500 pounds - This aligns with the FAA definition of a "large aircraft" (an aircraft with a maximum certificated takeoff weight of more than 12,500 pounds).
Large aircraft tend to be "working airplanes" in passenger or ...
6
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, getting their pressure altitude and getting their bearing from your aircraft. That data combined is processed to create threat advisories.
If displayed on a ...
5
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 conflict and situational awareness information.
Lidar is not presently utilized on civil aircraft for traffic avoidance.
Keep in mind that TCAS essentially uses ...
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