Why code 2000 at LHR
 

Supposed to select 2000 at LHR prior to setting the transponder to standby. What is the reason for this and is it common throughout Europe?

Thanks.

From aviation.stackexchange.com:

Selecting code 2000 before shutdown prevents the aircraft squawking a conflicting code when it the transponder is turned on again. Squawk codes are in short supply so they get reused pretty quickly.

This is not specific to LHR, it is (and has been for as long as I can remember) a requirement at all UK airfields. It is in the UK AIP and listed as an ICAO difference in AERAD/LIDO/JEPP documents.

From LIDO CRAR "Set Mode A Code 2000:
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When entering United Kingdom airspace from an adjacent region where the operation of transponders has not been required.
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By Mode S transponder equipped aircraft on the aerodrome surface when under tow, or parked and prior to selecting OFF or STANDBY - unless otherwise instructed by ATC."

" It has been reported that operators are failing to adhere to requirements for Mode S transponder equipped aircraft to select Mode A Code 2000 when under tow or parked (prior to selecting OFF or STDBY). As a result, ground systems are incorrectly pairing Mode S transmissions, which is resulting in unnecessary delays in procedures and potentially overloading critical ground systems."

https://www.caa.co.uk/docs/33/SafetyNotice201107.pdf

Thanks for the info.

So to be clear, please confirm that it is a UK only procedure and applicable to all UK operations or only applicable to aircraft with Mode S capability?

Also, what if 2000 is selected after going to standby. Will it still cause a problem?

Is there anything that can be done if it is discovered that the transponder is in Standby but still has the squawk code used on the previous flight?

2000 is basically 'no transponder code assigned'

Transponder Modes and Codes


2000 — Oceanic

[ICAO Doc 8168, Vol I, §III-3-1-1, ¶1.1.2] Except in case of emergency, communication failure or unlawful interference (see 1.4, 1.5 and 1.6), the pilot shall:

a) operate the transponder and select Mode A codes as directed by the ATC unit with which contact is being made; or

b) operate the transponder on Mode A codes as prescribed on the basis of regional air navigation agreements; or

c) in the absence of any ATC directions or regional air navigation agreements, operate the transponder on Mode A Code 2000.

[ICAO Doc 7030, §AFI, ¶5.1.1.2.] Africa-Indian Ocean Regional Supplementary Procedures. Unless otherwise directed by air traffic control, the last assigned SSR (Mode A) code shall be retained. If no SSR code has been assigned, Mode A code 2000 shall be selected and retained.

[NAT Doc 007, ¶6.8.1] All aircraft operating as IFR flights in the NAT Region shall be equipped with a pressure- altitude reporting SSR transponder. Unless otherwise directed by ATC, pilots flying in the NAT FIRs will operate transponders continuously in Mode A/C Code 2000, except that the last assigned code will be retained for a period of 30 min after entry into NAT airspace or after leaving a radar service area. Pilots should note that it is important to change from the last assigned domestic code to the Mode A/C Code 2000 since the original domestic code may not be recognised by the subsequent Domestic Radar Service on exit from the oceanic airspace.

[AC 91-70A ¶5-5.b.] In airspace controlled by Oakland Center or Honolulu Center, accomplish normal VHF communication. In airspace controlled by Oakland Oceanic (KZAK), CPDLC or HF voice backup accomplishes ATC communication (including en route requests) and position reporting. You can also use HF as primary communication for the aircraft not equipped with data link. When reaching oceanic airspace, squawk 2000 and monitor VHF 121.5 and the pacific air-to-air frequency 123.45.

[AC 91-70A ¶8-16.b.] In South America, there are no alternate instructions in the AIP. Therefore, use code 2000 when beyond radar coverage if there is no specification for another code.

[AC 91-70A ¶13-9.b.] Special Requirements For Flights Transiting Iceland. Pilots will operate SSR transponders continuously on Mode A, Code 2000, except that departing aircraft will retain the last assigned code for 30 minutes after entry into NAT oceanic airspace unless otherwise instructed by ATC.

[AC 91-70A ¶14-2.d.] On polar routes beyond areas of radar coverage, squawk 2000.

[AC 91-70A Appendix 2, ¶2.g.] Thirty minutes after oceanic entry, crews should Squawk 2000, if applicable. There may be regional differences such as Squawking 2100 in Bermuda’s airspace or maintaining last assigned Squawk in the West Atlantic Route System (WATRS). Crews transiting Reykjavik’s airspace must maintain last assigned Squawk.

In general you are going to squawk 2000 when oceanic, waiting 30 minutes after the entry waypoint is required over the North Atlantic and doesn't hurt elsewhere. There are exceptions so make sure you view the regional pages before entry.

I understood that selecting 2000 at LHR removes the aircraft from the LHR ATC system as the code is processed out of the controller's computer display. I'm afraid I don't have a reference though.

Our company, which flies Europe-wide, seems to have an un-written policy of setting 0000 instead of 2000 on arrival, wherever we are, and the resetting of the squawk from the specific allocation before selecting standby is not mentioned/encouraged. Is this something we are getting majorly wrong?

In the UK 0000 is used when level information is unreliable. When I was trained it was called "alpha midnight", I've never seen it used live.

However, yes I think using 0000 when you're shutting down is wrong.

I'm actually not sure how 0000 is treated by the radar system but in theory I could see it overriding ATC level filters (as it's supposed to use for traffic with unreliable level reporting) so if that is the case then setting it before parking could in theory cause your target to appear on area displays. I have no idea though if that is how a 0000 code would be treated or not.

Perhaps someone with more area and technical experience could add in some more info.

Thanks Crazy Voyager.

The requirement to select 2000 prior to standby in the UK is found in AIP ENR Section 1.6 para 2.2.1(e)

My original airline used to have the same, 0000. The policy was put in place as a best practice based on ATC request during the implenetation of A-SMGCS; home base was one of Europe's first three to go operational with it. Whether it is still the case, that in A-SMGCS environment 0000 has some special significance, I do not know. At the same time, we had been asked to put sqawk on AUTO before calling for pushback - seemed very reasonable.

regards,
FD.

Setting transponder to 2000 is part of our parking flow, too, regardless of the airport (and we don't fly to the UK). Sometimes that gets forgotten. Even by me. Once. Okay, twice.

Dubai as well is using the same procedure

2000 is the IFR conspicuity code in the same way as 7000 is the VFR conspicuity code. (For the Americans it is used this side of the pond the way you guys and gals use 1200.)

The nearest thing to legislation I can find a link for:
https://www.caa.co.uk/docs/33/SafetyNotice201107.pdf

Special Purpose Mode A Codes
Some Mode A codes are reserved internationally for special purposes and should be selected as follows:
Code 7700. To indicate an emergency condition, this code should be selected as soon as is practicable after declaring an emergency situation, and having due regard for the over-riding importance of controlling aircraft and containing the emergency. However, if the aircraft is already transmitting a discrete code and receiving an air traffic service, that code may be retained at the discretion of either the pilot or the controller;
Code 7600. To indicate a radio failure;
Code 7500. To indicate unlawful interference with the planned operation of a flight, unless circumstances warrant the use of Code 7700;
Code 1000. To indicate an aircraft conducting IFR flight as GAT, where the downlinked aircraft identification is validated as matching the aircraft identification entered in the flight plan;
Code 2000. When entering United Kingdom airspace from an adjacent region where the operation of transponders has not been required;
Code 7007. This code is allocated to aircraft engaged on airborne observation flights under the terms of the Treaty on Open Skies. Flight Priority Category B status has been granted for such flights and details will be published by NOTAM.
Note: Mode C should be operated with all of the above codes.

Wow!
 

I learn a great deal while reading this forum, though I must say very few topics are totally and completely foreign. In this case, the multiple uses of transponder code 2000 was as foreign as I've ever seen. OK, I don't fly international of x-pond routes, but still... Wow. Thanks guys!

Slightly off topic (apologies to the OP) but I found another interesting page with about 20 "special" codes from various corners of the world.

Transponder (aviation) explained

Lots of good info but...still don't know why 2000 must be selected prior to standby and if standby is selected first, does it cause a problem and if so, can anything be subsequently done about that problem.

Set 2000, then set standby, then shut down. When everything gets fired up for he next flight, 2000 is guaranteed and ATC is happy because there is no errant transponder code showing. New code assigned and ATC remain happy. Simples.

It's not so much for the next flight, as transponders are filtered out from being displayed on the ground radar when the target is on stand. It's so that we see the aircraft registration on the radar if the aircraft is towed from one stand to another. Ground handling procedures say that the towing crew must tow with the transponder on.