Two aircraft are planning on conducting a standard formation flight (aircraft remaining within 1 mile of each other) as follows in the U.S.:

  1. Maintaining VFR below 10,000 MSL;
  2. Remaining outside/clear of Class B/C/D airspace;
  3. The route will be totally within the 30 mile mode-C veil of an airport listed in appendix D to Part 91, for example - Houston or Atlanta; (FAR 91.215)
  4. FAR 91.111 will be complied with: see below:

§91.111 Operating near other aircraft.

(a) No person may operate an aircraft so close to another aircraft as to create a collision hazard.

(b) No person may operate an aircraft in formation flight except by arrangement with the pilot in command of each aircraft in the formation.

(c) No person may operate an aircraft, carrying passengers for hire, in formation flight.

  1. No flight plan will be filed;
  2. No communication with ATC will be established. (takeoff/landing will be at non-towered, uncontrolled airports in Class G airspace);
  3. Both aircraft will be equipped with a properly certified operable (4096 3/A, w/Mode C) transponder in accordance with FAR 91.215;

Question: Is it legal for only the agreed upon formation leader to have his/her transponder on with the other aircraft's tansponder set to "standby?" Or do both airplanes have to have their transponders on?

  • 1
    $\begingroup$ Your question is a bit confusing. On the one hand you state you will remain clear or Class B, C or D airspace. But on the other hand you state you will fly within the mode C veil of an airport, but you reference FAR 91.215, which is about flying in Class D airspace. $\endgroup$ Oct 27 '18 at 22:13
  • 1
    $\begingroup$ @JuanJimenez - 91.215 is this: " ATC transponder and altitude reporting equipment and use" (it's not about flying in Class D airspace. $\endgroup$
    – 757toga
    Oct 27 '18 at 22:48
  • $\begingroup$ For some reason I picked up the wrong FAR when I did the search. You are correct. :) $\endgroup$ Oct 27 '18 at 22:57
  • $\begingroup$ aircraft remaining within 1 mile of each other is NOT a formation<g>. A formation is measured in feet, not in miles! $\endgroup$
    – RAC
    Oct 29 '18 at 9:30
  • 2
    $\begingroup$ @RAC - Here is the definition of a formation flight from the AIM Pilot Controller Glossary (it's the same in the Controller's Handbook): "A standard formation is one in which a proximity of no more than 1 mile laterally or longitudinally and within 100 feet vertically from the flight leader is maintained by each wingman." By the way, ATC separation standards are based on all aircraft remaining within one mile of each other unless the formation becomes non-standard, in which case the separation is increased. $\endgroup$
    – 757toga
    Oct 29 '18 at 14:46

The way 91.215 is written, you must operate your mode C transponder in rule airspace unless ATC tells you not to.

The reason ATC tells you not to squawk in the case of a formation flight is to avoid triggering a constant stream of Collision Alerts between members of the formation, which is useless, annoying and may distract them from an actual problem elsewhere.

However, the CA is suppressed if all the aircraft involved are squawking 1200 (VFR) because there's no point warning the controller about a possible collision between multiple aircraft they're not talking to.

  • $\begingroup$ This answer makes sense. Additionally, the Mode C requirement is to allow controllers to separate their aircraft from any other aircraft within the Mode C veil. If you were talking to ATC @757toga, they would know you're a formation flight and would be able to separate based on that knowledge even if your wingman squawks standby. If you aren't in contact with ATC, they might not know about your wingman unless their transponder was on as well. $\endgroup$
    – randomhead
    Feb 17 at 1:13

Yes, it is legal. The FAA's guidance document for formation flight (short document, easy read) mentions standard formations, and it states:

c. After join-up, aircraft beacon code assignment will be determined by formation type.

  1. For a standard formation only the aircraft acting as the lead will squawk an ATC assigned beacon code. Ensure all other aircraft squawk standby.

There is also FAA Order JO 7610.4 regarding special operations, on which the guidance is based, but that document is only available internally from within the FAA network.

If you intend to fly within Class C airspace or within 30 nm of any airport in 91.215 Appendix D, you have to contact ATC (as you would to ask for flight following) to deviate from the requirement that all pilots squawk VFR. Arbitrarily deviating from the transponder rule without getting permission from ATC would likely be judged in violation of rule.

  • $\begingroup$ The FAA guidance document you refer to applies to Air Traffic Controllers and how they will handle formation flights. My question is in reference to flights within the 30 mile "mode C veil" of a Part 91, appendix D airport, but clear of Class B, where the formation flight does not have to contact ATC, but must comply with the transponder requirements of far 91.215 $\endgroup$
    – 757toga
    Oct 27 '18 at 22:52
  • $\begingroup$ I have edited my answer to address your specific circumstances. $\endgroup$ Oct 27 '18 at 22:56
  • $\begingroup$ I think you are confusing Class C airspace with this question. This question only applies to operations within the 30 mile Mode C veil of an airport listed in FAR Part 91, appendix D - clear of Class B/C/D airspace. When you are flying in the 30 mile mode c veil, clear of Class B airspace, you are in Class E airspace (or perhaps when below 1200 or 700 feet) you may be in Class G airspace (not Class C) $\endgroup$
    – 757toga
    Oct 27 '18 at 23:01
  • 2
    $\begingroup$ IMO, 91.215 makes no such distinction. If you are within 30 nm of any of the airports in Appendix D, all pilots are required to operate their transponder with Mode C enabled. If you want to deviate, you have to contact ATC. $\endgroup$ Oct 27 '18 at 23:07
  • 2
    $\begingroup$ It’s just slang for “set your transponder to standby” $\endgroup$
    – MikeY
    May 27 '19 at 13:03

IMHO, I offer the following, the current FAR requires an operable transponder to enter any Mode C veil, regardless of your flight circumstances...(VFR/IFR/formation/flight plan or not/flight following or not). On January 1, 2020 the new requirement for all aircraft to enter any Mode C veil is an operable transponder with AD-SB Out capability. If you are leading a formation flight or part of a formation flight, each Aircraft PIC is required to comply with the current FAR. Any deviation requires approval from ATC. Supposedly, "on frequency" requests and approval in regards to the AD-SB out requirement is not going to be allowed. All aircraft in formation entering the "rule" airspace should be equipped with AD-SB Out in the event that the formation breaks up. If an aircraft loses the formation or breaks away and is not equipped while inside "rule" airspace, there is a good possibility of a violation occurring, unless an emergency is declared. Using the 24 hour written pre-approval process, the formation flight could occur as described with proper planning and ATC approval. Without any coordination or approval from ATC, I would be careful not to enter any "rule" airspace, including penetrating any Mode C veil around Class B airports unless your aircraft is properly equipped.


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