Talk:Transponder (aviation)

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On March 15, 2007, Germany will use 7000 for VFR flights, just as the rest of Europe does, instead of 0021 and 0022. See http://www.skycontrol.net/service-providers/change-of-german-vfr-transponder-codes-ac-7000-replaces-ac-0021-and-ac-0022/ - we need to change the article accordingly 86.80.211.229 12:20, 19 February 2007 (UTC) Wouter

Contents 1 changing squawk codes 2 Adding a note for future reference 3 MODE A AND MODE C 4 Deletion of Mnemonics 5 Proposed Merger of Transponder (aviation) with Secondary surveillance radar 6 Unreferenced Text 7 Transponder codes 8 Selection of standby to change codes 9 FINDING REFERENCES

[edit] changing squawk codes

Australian procedure is to select STBY first, then select the new code, then reselect ALT, to avoid inadvertently selecting an emergency code, or another code already in use. This is from the AIPs —The preceding unsigned comment was added by Cabdude (talk • contribs) 11:23, 1 May 2007 (UTC).

Canadians are specifically warned not to do this, so as to not lose the protection afforded by TCAS during the code switch. —Preceding unsigned comment added by 12.24.137.66 (talk) 14:34, 8 October 2007 (UTC)

I saw lately in ICAO 4444 Pans OPS à certain phraséology guideline to avoid this kind of confusion, if the controller estimates that the pilot could pass over an emergency squawk, he will use the term: RECYCLE ( put transponder on stby, the tune new code then react transponder) else he should use the term : Squawk XXX ; however with the new technology on comercial planes this is less and less a factor due to the fact that transponders are digital and no more manual inputs. —Preceding unsigned comment added by Luckyglider (talk • contribs) 11:47, 12 May 2008 (UTC)

[edit] Adding a note for future reference

The confusion about the issue of whether TCAS II needs mode S to work or not results from the following:

In order for TCAS II to work in an aircraft, that aircraft must be equipped with at least 1 functioning Mode S transponder.

Once an aircraft is equipped, the TCAS can generate various advisories against any intruder that is equipped with an ICAO compliant transponder. In all cases, traffic advisories (TAs) can be generated. When the intruder is altitude reporting (be it Mode S or Mode C) then a Resolution Advisory (RA) is issued when necessary. When the intruder is TCAS equipped, the RAs generated are coordinated, by datalinking via the mode S transponders, to ensure that the avoiding manoeuvres are coordinated (e.g. to make sure one aircraft pitches up, and the other down, rather than both up!).

I.E. *You* have to have mode S for your TCAS to work. The intruder doesn't.

The other area of confusion about this issue is what is meant by a Mode C transponder versus a Mode A transponder.

Mode A is an interrogation sequence that prompts the transponder to reply by encoding its identifying 4096 code.

Mode C is an interrogation sequence that prompts the transponder to reply by encoding its altitude.

Hence, most people (and most textbooks) take the view that when an aircraft is not equipped with altitude encoding it is equipped with a Mode A rather than a Mode C transponder. This is incorrect.

ALL non mode S transponders reply to both Mode A and Mode C interrogations. ATC radars send out both a Mode A and a Mode C interrogation. When the aircraft it not equipped with Altitude reporting, the transponder still replies to the mode C call, but with a pulse frame only, and the encoded section of the reply is omitted.

I.E. What is popularly referred to as a 'Mode A' transponder is in fact a 'Mode A and C without Altitude Reporting transponder'.

What is popularly referred to as a 'Mode C' transponder is in fact a 'Mode A and C with Altitude Reporting Transponder'.

This incorrect designation even goes as far as many transponder controllers, where the mode selecting knob is labelled something like 'Off', 'STBY', 'A', 'A+C', when it should be 'Off', 'STBY','On', 'On+Alt'.

Nevertheless, I accept that this is a fine distinction that does not really affect a typical line pilot. However, if you want to understand how TCAS works, then it becomes an issue......

Because practically every nuance of how TCAS and Mode S function is driven by the engineering need to avoid any unnecessary transmissions in the secondary radar bands. Whereas pre-TCAS, the only transmissions were from ground radar heads to aircraft, now every aircraft is also keeping track of every other aircraft within the vicinity (something like 40 NM). Therefore, without care, the entire secondary radar bands would be swamped!

Mode S includes a lot of tricks to achieve this, but I don't propose to talk about it in this post but will expand if you wish. As far as other transponders go, appreciate that TCAS doesn't care what 4096 ident code the intruder is wearing. It only cares about the range to the intruder, and the intruders altitude.

To find the the range, a time delay versus speed of light calculation is required. This simply needs the intruders transponder to reply, and this could be achieved by either a mode A or a Mode C interrogation.

To find the altitude, obviously a Mode C interrogation is required.

From this we can see that if TCAS sends a Mode C interrogation, it can achieve both objectives, both range and Altitude. Therefore there is no need for TCAS to send a Mode A interrogation, so to avoid garbling the secondary radar frequencies it doesn't.

I.E. TCAS only sends mode C, and not mode A, interrogations for dealing with non mode S intruders,

So, technically, TCAS will only see Mode C and Mode S transponders.

So, technically, TCAS will not see Mode A transponders, and you will not get any advisories.

However, what people think are Mode A transponders are in fact Mode A and C transponders, just without altitude encoding.

CPB TCAS instructor

[1]

--Natasha2006 18:21, 14 June 2007 (UTC)

[edit] MODE A AND MODE C

THE STRAIGHT SCOOP ON HOW IT WORKS by Darryl Phillips [2] [3]

--Natasha2006 18:29, 14 June 2007 (UTC)

[edit] Deletion of Mnemonics

212.76.61.206: I have for a second time reverted the inclusion of mnemonics for people learning how to memorize transponder codes as part of pilot ground school. As is made very clear in Wikipedia Policy Wikipedia is not a how to manual and this information does not belong here.

As for the personal attack that went with the reversion of my edit, this is also not permitted under Wikipedia policy Wikipedia:No_personal_attacks. If you would like to discuss the issue civilly then this talk page is the forum to do that.

- Ahunt 22:14, 1 November 2007 (UTC)

[edit] Proposed Merger of Transponder (aviation) with Secondary surveillance radar

This article was tagged for consideration for merger on 11 December 2007 by PEHowland. The tag was incorrectly constructed and led to the wrong talk page, so that may have slowed down comment on this issue!

I will start off the debate by indicating that I am against merging these two articles. I don't see that they are one subject. - Ahunt (talk) 23:21, 1 January 2008 (UTC)

Against merger - the transponder is an avionics system fitted to an aircraft, SSR is a ground based radar system. Just because the SSR interogates the transponder is not motive for one article. MilborneOne (talk) 13:08, 2 January 2008 (UTC)

This matter has been up for discussion for 5 weeks now and not one editor has come out in favour of merging the two articles. I think this puts the matter to rest and so I will remove the proposed merger tags from both articles. - Ahunt (talk) 19:00, 5 January 2008 (UTC)

[edit] Unreferenced Text

I have removed some unsourced information from this article on the apparent history of the term "squawk and "parrot check". Parts of this paragraph have been tagged as unreferenced for five months. The information seem doubtful or apocryphal at best and my attempts to finds refs for it have not been successful. Since no one else has found any refs for it in five months I have removed it. The response from an IP address 137.240.136.86 and 137.240.136.80 (same person) has been to edit war over it, including uncivil remarks and attempts to bully over this issue with such statements as "no one elected you sherrif (sic), move along".

The policies on this sort of issue are very clear:

"If a claim is doubtful but not harmful to the whole article or to Wikipedia, use the {{Fact}} tag, but remember to go back and remove the claim if no source is produced within a reasonable time."

I think five months is reasonable time.

If any one has a reference for this removed para then by all means please re-instate it. If you don't have a ref then it will remain out of the article.

For anyone who doesn't think it is important for Wikipedia to be scrupulously referenced, I suggest that you read this CBC article. A lack of references can cause real damage in some cases. - Ahunt (talk) 18:58, 13 March 2008 (UTC)

[edit] Transponder codes

This article should be about the item of equipment called the Transponder the large section on codes and how they are used should be deleted/moved to Secondary Surveillance Radar or similar. Any comments? MilborneOne (talk) 20:28, 7 May 2008 (UTC)

[edit] Selection of standby to change codes

An IP editor has now twice removed the word "not" from this sentence in the article:

"Pilots are instructed not to place the transponder in "standby mode" while changing the codes as it causes the loss of target information on the ATC radar screen, but instead to carefully change codes to avoid inadvertently selecting an emergency code."

The Transport Canada ref cited says: "Do not select “STANDBY” while changing codes as this will cause the target to be lost on the ATC radar screen."

Does anyone have any other information on this subject? Many years ago it was the practice to select "stby" when changing codes, but with radar modernization in the 1980s this was changed.

Besides that the removal of the one word makes the sentence non-sensible. Ahunt (talk) 20:56, 7 May 2008 (UTC)

[edit] FINDING REFERENCES

hI

just some problems to find some references , i have added two SSr 3/A codes allocation but unfortunately I haven't got the latest official Icao/Nato MODE 3 allocation table however if someone could give me a hand on this this could be nice but for french paradrop I am certain of the squawks used by FR FIC also for Belgians I have no doubt over them .

have a nice day —Preceding unsigned comment added by Luckyglider (talk • contribs) 11:41, 12 May 2008 (UTC)