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.

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2
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1answer
334 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 ...
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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 ...
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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. ...
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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?
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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 &...
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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 ...
6
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1answer
135 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 ...
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34 views

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

Is a Mode S transponder required as part of TCAS I?
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82 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 ...
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1answer
63 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.
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3answers
118 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,...
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1answer
362 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,...
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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 ...
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When may I change my transponder code to 1200 when being handled by ATC?

When am I allowed to change my transponder code to 1200? Is it after clearing the boundary of regulatory airspace (ie. airspace requiring radio contact and an operating transponder)?
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1answer
398 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 ...
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537 views

Do interceptor squawk codes suppress TCAS RAs?

Some parts of the world reserve a discrete squawk code for use by military interceptor operations (in the NBCAP, code 7777 is used for this). Does this squawk code, or some equivalent value, suppress ...
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1answer
77 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 ...
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1answer
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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 ...
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2answers
14k views

Why are there so many 7700 squawks?

I installed an app some months ago, which gives a push message when an aircraft squawks 7700. The first time it happened, I thought the plane was about to crash, ...
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3answers
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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 ...
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2answers
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Which source to use when reporting the current altitude to ATC?

While flying from KSNA to KVCB VFR at night, Norcal Approach asked for my current altitude. I was somewhere between 12.0 and 12.5 depending on which reading I was going to use. ATC had me confirm. ...
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Does ATC use mode S addresses to identify planes?

By design, Mode S surveillance radar equipment uses global 24-bit airframe addresses to keep track of the aircraft it is tracking. Are these addresses also used by higher levels of the ATC system, ...
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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 ...
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1answer
92 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-...
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3answers
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How does the modulation of the transponder work?

The transponder works in PCM (pulse code modulation): how does it work in the transponder? I can find explanation of what PCM is, but not if the signal sent from the transponder antenna is digital or ...
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1answer
95 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 ...
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9answers
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Can a military pilot make his airplane invisible for the ATCs?

I'm writing a story about the pilot of the Austrian Air Force, who uses his Eurofighter Typhoon aircraft for unintended purposes. I've read stories in the internets that civil pilots allegedly can ...
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1answer
546 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 ...
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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 ...
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2answers
1k 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 ...
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1answer
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What is Mode B on the transponder?

Mode A selected on the transponder provides identification of the aircraft to the secondary radar; Mode C will add an automatic height read-out of an aircraft. Mode S is a selective addressing. But ...
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1answer
4k views

Which antenna on an commercial airline airplane is used for the transponder (SSR)?

On the 767-200 image I see no SSR antenna, but since that TCAS uses the transponder I guess that are sharing the same antenna. Am I right ?]1
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6answers
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Why is the range of transponder digits 0 to 7 rather than 0 to 9?

As a controller on IVAO I sometimes assign codes like 0168 and find out later that the code isn’t valid. For me, the range 0-9 seems more logical. Why do we have to use octal numbers and not decimal?
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1answer
2k views

After purchasing an aircraft, how do I put the transponder in my name?

I just purchased an aircraft and the prior owner said that I need to put the transponder to my name. What is the procedure to do that?
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7answers
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 ...
3
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1answer
87 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 ...
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2answers
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 ...
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1answer
238 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)?
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1answer
272 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,...
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2answers
9k views

Are transponder codes 7701 - 7777 ever used?

I understand that blocks of transponder codes are assigned to different area controls. I am curious if the block 7701 to 7777 is in use anywhere? Maybe the emergency code 7700 needs some extra ...
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1answer
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Is it recommended to have an ADS-B transponder in ALT mode on the ground? [duplicate]

Early on in training I was told that unless the airport specifically noted it on the chart, that the transponder was turned to ALT (altitude) mode just prior to taking the runway for take-off (lights, ...
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9answers
171k views

What are the advantages of squawking 7700?

I was reading this question about how do pilots send distress signals in emergency scenarios, and that got me thinking... In voretaq7's answer, he states that there are three ways to send distress ...
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1answer
189 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 ...
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321 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 ...
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1answer
247 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 ...
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3answers
190 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 ...
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2answers
950 views

What happens to the transponder, FDR and CVR in case of an explosion?

Will the above mentioned equipment still work and transmit data/location information if an explosion occurs inside the aircraft?
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2answers
13k 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 ...
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3answers
4k views

What could cause an inadvertent squawking of 7700?

I get alerts whenever a plane squawks 7700, using a popular flight tracker application. It happens quite frequently that the aircraft, reported to squawk ...
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2answers
3k 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 ...