Questions tagged [transponder]

A radar transponder is a radio beacon on an aircraft that replies to a radar interrogation. The transponder encodes information into the reply, allowing air traffic control to know the aircraft's altitude and identity.

Filter by
Sorted by
Tagged with
4 votes
0 answers
70 views

How to reduce the volume of the GTN750 traffic warning beep?

We've got a GTN 750 with ADS-B IN and OUT. When we encounter traffic it emits a high pitched pulsing beep. It cannot be muted by any means - say you are on final and there's an aircraft holding short ...
user avatar
3 votes
1 answer
187 views

Would the "Calibrated Altitude" figure on FlightRadar24 better be labelled "Pressure Altitude"?

On FlightRadar24, when a user clicks on an airplane icon, the data panel shown above is displayed. Note the figure labelled "calibrated altitude". For an airplane flying below the "...
user avatar
  • 17.1k
0 votes
0 answers
40 views

Quality indicators ADS-B out & Ground Station receiver

I have a question about quality indicators parameters: I discussed with a pilot about quality indicators . We talked about NIC and NACp parameters I received his quality indicators in my ADS-B Ground ...
user avatar
4 votes
1 answer
292 views

Is a Mode S address changed when an aircraft is sold to another country?

The 24 bit Mode S address is issued by the national CAA where the aircraft is registered. If it is sold to another country, with another CAA, is the Mode S address maintained or is a new one assigned?
user avatar
7 votes
1 answer
1k views

Does ADS-B use its own antenna?

In the aircraft we have: ADS-B out/in using 1090ES A/C or Mode S transponder for SSR grounding interrogation. Does the ADS-B out use the same antenna as Mode S or does it use its own antenna?
user avatar
4 votes
1 answer
736 views

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

With TCAS, the time to respond to an RA is 5 seconds (2.5 seconds for a reversal RA). The FCOM states that the TAU (estimated time) before the aircraft intruder reaches the "Closest Point of ...
user avatar
  • 311
6 votes
2 answers
714 views

Why should you never squawk 0000 in the USA?

FAA Order 7110.66E says Code "0000" should never be assigned or used. and Code 0000 must never be assigned However, NASA recommends that crews set 0000 after landing to help detect when ...
user avatar
  • 22.3k
4 votes
1 answer
159 views

Does the ATC not receiving Mode C and intermittently other transponder information imply that the Mode S transponder itself has an issue?

I had ATC report to me inflight today that they were not receiving my Mode C (altitude data). Intermittently, they also reported they were not seeing any other transponder information. My transponder ...
user avatar
2 votes
1 answer
101 views

Can a formation flight operate in class B if only the lead aircraft is equipped with a transponder?

We all know that you can't fly in Class B airspace without a transponder. But, when doing a formation flight, only the lead plane has their transponder turned on. Does that mean that it's possible for ...
user avatar
4 votes
2 answers
321 views

Why is a Mode S transponder required to be installed and working for TCAS II to be operational?

I am wondering why a Mode S transponder is required to be installed and working for TCAS II to be operational? I read such phrase in Eurocontrol ACAS II guide and I don't understand why mode A/C is ...
user avatar
  • 1,691
2 votes
1 answer
402 views

Does TCAS II work and give RA with Mode C or Mode A transponders?

What's the minimum requirement for TCAS II RAs to be generated? Will we get RA if we have mode C transponder and the other aircraft also has mode C? Will mode A work as well?
user avatar
6 votes
1 answer
397 views

Why does TCAS need 2 antennas?

Can someone explain why TCAS needs 2 antennas (one on the top of the fuselage and one on the bottom)? And why is the top one directional and the bottom one can be either omnidirectional or directional?...
user avatar
  • 1,691
0 votes
1 answer
371 views

Can single engine/smaller aircraft turn off ADS-B?

I was just looking at the adsbexchange website, and was wondering if it was possible for smaller, private aircraft to turn off their ADS-B? I was wondering this because id figure that maybe not ...
user avatar
1 vote
1 answer
292 views

Is transponder required to turn off in formation flying?

When planes are flying in formation, TCAS will undoubtedly alert the crew. As a result, in this instance, the transponder must be turned off. The pilot must, however, rely on eyesight rather than ...
user avatar
  • 1,475
11 votes
2 answers
456 views

Why are gliders oftentimes not equipped with a transponder?

Oftentimes gliders are not equipped with transponders (at least in Europe). Even if they are, they do not necessarily operate it at all times. This is allowed by SERA.13001: (a) When an aircraft ...
user avatar
  • 1,053
1 vote
1 answer
673 views

What does prevent installing an ADS-B transponder on a vehicle?

FlightRadar24 indicates they also track ground vehicles: Ground vehicles visible on Flightradar24 are generally those that are most active in the movement areas of an airport, like airport rescue and ...
user avatar
5 votes
2 answers
3k views

How far can a plane squawking 7700 be heard and how quickly will the news spread?

This is just an idle question I have after watching Non-Stop (2014), but suppose a plane (let's assume a Boeing 767-400) is over the Atlantic and sets its transponder to indicate it's in an emergency. ...
user avatar
1 vote
0 answers
125 views

Why does the A320 transponder's CLR button do two different things, depending on how many digits were entered?

I have to admit I've only flown in simulators but everyone of them implements the "CLR" button of the transponder in an A320 (maybe also others) the following way: It removes the fourth ...
user avatar
  • 111
6 votes
1 answer
191 views

Why bits are mixed up (interleaved) during ATC transponder mode A and mode C reply format?

In the image above from radartutorial.eu, we can see that the sequence of bits are c1 a1 c2 a2 c4 a4 during the reply of ATC transponder mode A. Why are the bits not transmitted like c1 c2 c4 then a1 ...
user avatar
-3 votes
1 answer
127 views

What information does Mode S provide?

What information about own aircraft does TCAS Mode s( all call) send in the interrogation? What information does Mode S transponder(intruder)replay to TCAS interrogation?
user avatar
1 vote
0 answers
49 views

Is a Mode S transponder required as part of TCAS I?

Is a Mode S transponder required as part of TCAS I?
user avatar
1 vote
1 answer
614 views

What is the difference between SSR and ADS-B?

Can someone explain what is the difference between SSR transponder and ADS-B. From what I know ADS-B is a capability that can be incorporated into a transponder, but I do not understand the difference ...
user avatar
  • 1,691
0 votes
1 answer
91 views

How can I know if the Garmin GTX 345 transponder supports modes A and C?

How can I know if the GTX 345 supports mode A/C? I did not find a mention in the installation manual the capability of mode A/C.
user avatar
1 vote
3 answers
174 views

Are mode C altitude returns valid for aircraft separation?

According to FAA JO 7110.65 5-12-8 'Validation of MODE C READOUT', Mode C is valid if there is less than 300 feet deviation from the pilot reported altitude. If ATC instruct 'A' aircraft to maintain 5,...
user avatar
  • 611
1 vote
1 answer
184 views

Why does CFR §91.215 part (b) list specific areas for transponder operations?

Why does part (b) list individual sections where transponder operations are required when part (c) states that transponder operation is required in all controlled airspace? All sections listed in part ...
user avatar
7 votes
1 answer
365 views

How are both squawk and altitude transmited when operating a Transponder in Mode C?

I know that in Mode $3$ (which includes Mode A and Mode C) the aircraft transmits $12$ information pulses. That corresponds to $2^{12}=4096$ squawk combinations in Mode A which are sent to ATC to ...
user avatar
  • 1,090
4 votes
3 answers
3k views

Is it legal to fly without a transponder?

Everything is legal / airworthy. Except: Transponder is installed. It does work. It has NOT been inspected in any time frame that would show it is properly maintained. Flight is Golf, Echo, Delta &...
user avatar
  • 191
34 votes
2 answers
5k views

Should I contact ATC if I don't have a transponder?

The flight school I usually rent from is under the shelf of class C airspace. If you're going out to a practice area, the standard procedure is to contact approach control and get a squawk code, so ...
user avatar
0 votes
2 answers
215 views

Is it possible for squawk to change automatically in emergency situations?

It might be a silly question, but is it possible for an airliner to automatically switch the squawk code to emergency (7700) during a flight? (For example in case of losing all engines) Thank You In ...
user avatar
0 votes
1 answer
137 views

Does the FAA construe FAR 91.225 to prohibit aircraft w/o electrical systems w/o ADS-B-out from flying above 10,000' MSL unless below 2500' AGL?

Does the FAA construe FAR 91.225 as imposing a general prohibition on flight above 10,000' MSL (excluding airspace below 2500' AGL) in aircraft without ADS-B-out, even for aircraft without engine-...
user avatar
  • 17.1k
2 votes
1 answer
134 views

Are there any situations where it's beneficial to disable altitude reporting in TCAS?

Having altitude reporting enabled persistently seems like a pretty common-sense thing to do -- it enables RA in addition to TA, the benefits of which are fairly obvious. That said, most of the common ...
user avatar
  • 965
6 votes
3 answers
320 views

Would FAR 91.227, or any other regulation, forbid use of ADS-B-out in an unregistered ultralight?

In the US, would FAR 91.227, or any other regulation or law, forbid use of ADS-B-out in an unregistered ultralight? Could the N-number field simply be left blank, without violating any regulation or ...
user avatar
  • 17.1k
1 vote
1 answer
1k views

Why do I never see fighter jets on sites like FlighRadar24 and ADBSExchange.com [duplicate]

On ADS-B Exchange they even have a filter option for military aircraft, and it will show all kinds of transport, mid-air refuelers, helicopters, and even training aircraft like the Texan, but I don't ...
user avatar
  • 11
2 votes
2 answers
2k views

Is a Mode C or S Transponder a type of Mode 3 Transponder?

Mode A transponders are sometimes referred to as Mode 3/A transponders. According to NATO STANAG 4193 (not publicly available, summary from Wikipedia), the "3" in that description refers to the mode ...
user avatar
  • 1,735
3 votes
1 answer
103 views

Why is Mode C helpful for ASDE-X systems?

Airports that operate an ASDE-X system require aircraft to operate transponders in mode C while moving on the surface. While I understand the general purpose of operating the transponder to ...
user avatar
0 votes
1 answer
307 views

Are Transponder Mode A and C still in use?

Are the ATC transponder Mode A and Mode C still in use (according to ICAO or FAA rules)?
user avatar
1 vote
1 answer
415 views

FAR 91.215 (b)(3)(ii) -- transponders-- does the "or below 10,000' MSL" clause have any practical significance?

Here are some of the airspaces where FAR 91.215 requires aircraft to have transponders-- (b) ... (2) All aircraft. In all airspace within 30 nautical miles of an airport listed in appendix D,...
user avatar
  • 17.1k
0 votes
1 answer
341 views

FAR 91.215-- may an aircraft with no electrical system and no transponder overfly Wheeler AAF at 9500' MSL?

Here are some of the airspaces where FAR 91.215 requires aircraft to have transponders-- (b) ... (2) All aircraft. In all airspace within 30 nautical miles of an airport listed in appendix D,...
user avatar
  • 17.1k
0 votes
1 answer
241 views

What additional airspace will be off-limits to an a/c w/ no elect. system or xponder under 91.225 (ADS-B) compared to under 91.215?

Under FAR 91.225 (requirement for ADS-B-out), what additional airspace over the 48 contiguous states in the U.S. will be off-limits to an aircraft w/ no electrical system or transponder, compared to ...
user avatar
  • 17.1k
1 vote
2 answers
451 views

How feasible digital radio communications would be? [closed]

Its been over 100 years since we first flew and we still use analog radio with parasites and "radio effect" which changes your sound. Why don't we ditch the old system and make a mandate a new law ...
user avatar
16 votes
7 answers
4k views

Why do (or did, until very recently) aircraft transponders wait to be interrogated before broadcasting beacon signals?

An aircraft’s transponder transmits signals that announce (at the very least) the aircraft’s identity, altitude, and direction of motion (plus, for most newer aircraft, a whole slew of other useful ...
user avatar
  • 26.2k
2 votes
1 answer
340 views

Why does setting the Legacy 600's transponder to standby mode also deactivate its TCAS?

In 2006, a 737 operating as Gol Transportes Aéreos Flight 1907 crashed following a collision with a Legacy 600 business jet; the Legacy's transponder proved to have been in standby mode1 at the time ...
user avatar
  • 26.2k
0 votes
3 answers
212 views

What does the future of the weather radars look like?

Planes had weather radars for a long time (Dassault Falcon and Learjet35A) which was useful since you either had to ask ATC, listen the ATIS frequency or ask the flight advisory before flight planning ...
user avatar
9 votes
3 answers
17k views

What is the purpose of squawking 7777?

Aircraft use transponders to communicate to ATC their position and status. Some squawk codes are reserved, such as 7700 (emergency), 7600 (communication failure), 7500 (hijacking), 1202 (glider), 1200 ...
user avatar
  • 387
10 votes
2 answers
1k views

What do you squawk when multiple conditions apply?

There are three standard transponder codes for exceptional situations: 7500 (hijacking), 7600 (radio failure), and 7700 (general emergency). Which code do you use if multiple situations apply? For ...
user avatar
  • 4,684
5 votes
3 answers
3k views

Is a mode C transponder required underneath Class C airspace?

FAR 91.215 states that a mode C transponder is required for... all aircraft in all airspace above the ceiling and within the lateral boundaries of a Class B or Class C airspace area designated ...
user avatar
22 votes
2 answers
4k views

Should I switch the transponder to STBY or not while changing codes?

I´m now reading Bob Gardner’s book “Say again, please” and there is this instruction on page 54: Do not turn the transponder function switch to STBY while changing codes. What is the reason for ...
user avatar
  • 495
11 votes
3 answers
1k views

In a part 91 formation flight within a mode C veil, are all the aircraft required to have their transponders on?

Two aircraft are planning on conducting a standard formation flight (aircraft remaining within 1 mile of each other) as follows in the U.S.: Maintaining VFR below 10,000 MSL; Remaining outside/clear ...
user avatar
  • 17.7k
2 votes
1 answer
501 views

How to keep a Garmin GTX330 turned off when powering on avionics?

There seems to be an option in the GTX 330 settings that keeps to unit from powering on when receiveing power from the power system. I flew in two different airplanes and one immediately powered on ...
user avatar
  • 325
0 votes
1 answer
706 views

If a pilot has the wrong altimeter setting, will his transponder mode C altitude be off too? [duplicate]

Just wondering if the transponder mode C reported altitude will be off if the pilot accidentally has the wrong altimeter setting.
user avatar
  • 4,133