There is a general reluctance to declare an emergency by pilots who believe it is either "less than manly" or will lead to a mountain of paperwork and unforeseen costs. Well I've declared an emergency 18 times in the last 34 years and have yet to receive a bill and the only paperwork I've ever had to fill out was a request for a few paragraphs, in my own words, in accordance with 14 CFR 91.3.
While I was flying Boeing 707's for the Air Force in Hawaii we had a pilot land at Honolulu International with a flap failure. The pilot considered but did not declare an emergency. At the last minute, the tower required he land short of an intersection — this was years before LAHSO was invented — or go around for what was sure to be 30 minutes of vectoring. He elected to land and cooked the brakes to the point all eight main gear wheels exploded and they nearly lost the airplane. They had to evacuate on the parallel taxiway, snarling airline traffic for hours. Had he declared an emergency none of that would have happened.
If you think the safety of your airplane is in danger unless you are guaranteed everything you need from the rest of the world, you need to declare an emergency. And do so using that word: "I am declaring an emergency." Air traffic control should understand. If they don't, try this: "If you do not approve this, people will die." Yes, you need to be blunt. See the case of Avianca 52 for a case where the pilots did everything except use that magic word. 73 people died who would have lived had the pilots been more forceful.
What about the term "minimum fuel?" It doesn't carry much weight but it is a tool at your disposal.
What about your passengers? Every time my airplane was met with the fire trucks and even the times we had to evacuate the aircraft on the runway, the passengers thanked me for taking care of them. I've had this experience with the CEOs of two major companies. Your passengers will thank you.
You get ample opportunity to practice this in a simulator and you ought to have the flow of the declaration down pat. Why? Because in a real situation having this articulation down will save you time, communicate your needs, and will improve the support you get. In other words, it gets you onto the ground sooner and safer. So here's mine: "MAY DAY, MAY DAY, MAY DAY, [CALL SIGN], declaring an emergency, [a brief statement of the problem and your immediate request], [___ souls on board, ____ hours fuel], we will get back with you with details, keep an eye on us." For example: "November 7700 declaring an emergency, left engine on fire, request vectors around the airport for an immediate landing, 10 souls on board, 4 hours fuel, we will get back to you with details, keep an eye on us."
Once you've declared an emergency, remember you are the most important aircraft flying and the priority shown you should reflect that. Unnecessary questions, frequency changes, or improper runway assignments should be avoided. There are other considerations.
What follows comes from the references shown below with my comments in blue.
The following applies outside the United States. As of 2016 these terms carry no meaning in the U.S. but I suspect that will change.
[ICAO Annex 2, App 1, ¶1.1] The following signals, used either together or separately, mean that grave and imminent danger threatens, and immediate assistance is requested:
The spoken word "Emergency" may or may not have the intended effect when outside the United States. If you want to be sure, "May Day" is what you need to say.
[ICAO Annex 2, App 1, ¶1.2.2] The following signals, used either together or separately, mean that an aircraft has a very urgent message to transmit concerning the safety of a ship, aircraft or other vehicle, or of some person on board or within sight:
The term "Pan, Pan" is equivalent to saying "Everyone else be quiet, I need the frequency because I've got a problem." There is no equivalent in the United States other than to say something like, "Break, break, I have an urgent message."
The point here is to communicate your identity to the air traffic controller as efficiently as possible. This isn't as easy as it may seem.
No matter where you are, the bottom line is you want to communicate your identity instantly, avoiding the "say again" routine when you are in a time critical situation.
In the United States, the controller expects the word "Emergency" and the phrase "May Day" is not officially recognized. This confusion has caused serious problems before, see: Mishaps / Avianca 52. The U.S. system has become more sensitive to this issue:
[Air Traffic Organization Policy, ¶5-1-1.
NOTE − A pilot who encounters a DISTRESS condition may declare an emergency by beginning the initial communication with the word MAYDAY, preferably repeated three times. For an URGENCY condition, the word PAN-PAN may be used in the same manner.
This policy is aimed at air traffic control but gives the pilot insight on the total thought process that you may need to know. For example, I've heard of a crew that reported a flap problem but said no when asked if they wished to declare an emergency. The ATC controller declared an emergency on their behalf, out of an abundance of caution, and the aircraft was met with fire trucks. Now this in itself is not a problem. But now the crew should make a written record of the event, per 14 CFR 91.3, below. Furthermore, the crew was then compelled to seek documented maintenance to resolve the situation.
As long as you have the microphone keyed, give the controller a very brief description of the problem and what you need at the moment. If you get this out of the way now, you will avoid repeated requests from the controller who is trying to check three items off from the very top of his or her task list:
[FAA Order J7110.65V, §2, ¶10-2-1.a.1.] Start assistance as soon as enough information has been obtained upon which to act. Information requirements will vary, depending on the existing situation. Minimum required information for inflight emergencies is:
This gives the controller an idea of what needs to happen next. "We've got an engine on fire" tells the controller you are dealing with a problem, don't have time to chat, and perhaps he or she should prepare the pattern for your return if the weather is acceptable or start searching for alternates if not. "We've got a bird strike on our left engine, we have it shut down," telegraphs a different message and perhaps there will be time to burn fuel off.
This doesn't have to be your complete game plan, it could be something as simple as "Request a ten minute box pattern around the pattern so we can sort this out."
The list of things the controller wants to know is pretty long but only two items beyond those already covered are really important: souls and fuel on board. The crash rescue teams wants the first item; the controller needs to know how much fuel you have in terms of time. Don't bother with pounds or kilograms, they don't matter because the controller doesn't know your burn rate. Here is the complete list of additional information, but don't worry about it:
[FAA Order J7110.65V, §2, ¶10-2-1.b.] After initiating action, obtain the following items or any other pertinent information from the pilot or aircraft operator, as necessary:
You have just given the controller what could become a "career defining moment" and he or she will feel a bit powerless to help. The controllers want to do something and quite often that will be to bug you with questions. "We will get back to you," tells the controller you have other priorities at the moment. "Keep an eye on us," tells the controller that you are not going to be paying as much attention when it comes to avoiding obstacles, other aircraft, and airspace because you are busy. This gives the controller a way to help you.
[FAA Order J7110.65V, §2, ¶10-2-2] Although 121.5 MHz and 243.0 MHz are emergency frequencies, it might be best to keep the aircraft on the initial contact frequency. Change frequencies only when there is a valid reason.
It may be in your best interest to switch to the same frequency in use by other traffic but it may also be important to minimize the changes. If you have smoke and fumes in the cockpit, for example, changing frequencies may not be an option. It may be a simple matter of minimizing your workload, but no matter the reason, "Request single frequency for approach and landing" may give you the extra help you need. In the case of El Al 1862, for example, several frequency changes needlessly burdened the crew of a Boeing 747 with two engines on the same side failed.
[FAA Order J7110.65V, §2, ¶10-2-15.a.] Consider the following factors when recommending an emergency airport:
NOTE−Depending on the nature of the emergency, certain weather phenomena may deserve weighted consideration when recommending an airport; e.g., a pilot may elect to fly farther to land at an airport with VFR instead of IFR conditions.
If you have the time, let Air Traffic Control know about your plans to evacuate the aircraft. Specifically, where you intend to send the passengers. The best place would normally be upwind (so as not to be overwhelmed with any smoke and fumes), on the grass (so as not to be run over by rescue vehicles), on a diagonal forward or aft of the airplane (in case the wheels explode). In the case of Asiana Flight 214, a passenger was runover by a fire rescue vehicle.
While the regulations are the least of your concerns during an emergency, knowing them may help you better understand the pilot-to-controller interface.
[Aeronautical Information Manual, ¶ 5-5-15]
EXAMPLE−Salt Lake Approach, United 621, “minimum fuel.”
[Aeronautical Information Manual, ¶ 6-1-1] Pilot Responsibility and Authority
[Aeronautical Information Manual, ¶ 6-1-2] Emergency Condition- Request Assistance Immediately
[Air Traffic Organization Policy, ¶5-2-14.]
NOTE − Use of the term "minimum fuel" indicates recognition by a pilot that the fuel supply has reached a state whereupon reaching destination, any undue delay cannot be accepted. This is not an emergency situation but merely an advisory that indicates an emergency situation is possible should any undue delay occur. A minimum fuel advisory does not imply a need for traffic priority. Common sense and good judgment will determine the extent of assistance to be given in minimum fuel situations. If, at any time, the remaining usable fuel supply suggests the need for traffic priority to ensure a safe landing, the pilot should declare an emergency and report fuel remaining in minutes.
We used to think of declaring "min fuel" akin to saying, "I dare you to give me another vector, because if you do, I am going to declare an emergency and that will really muck up your system, won't it!" The term used to carry no weight at all. Over the years, it seems, U.S. ATC controllers have become more empathetic with their counterparts in the air. You certainly see that when asking for weather deviations and I think also with your fuel state. But the bottom line on running out of gas is it is your hide not theirs. The only thing they can ask of you if you declare an emergency for fuel is to make a written report of how you got in that situation. You can answer that you had the legally required amount when you took off and the winds and a number of altitude, airspeed, or heading assignments ate up your reserves. That's much better than seeing your engine gauges wind down short of the chocks, isn't it?
Portions of this page can be found in the book Flight Lessons 3: Experience, Chapter 11.
14 CFR 91, Title 14: Aeronautics and Space, General Operating and Flight Rules, Federal Aviation Administration, Department of Transportation
Air Traffic Organization Policy Order JO 7110.10X, April 3, 2014, U.S. Department of Transportation
FAA Order JO 7110.65V, Air Traffic Control, April 3, 2014, Department of Transportation
FAA Order JO 7340.2F, Contractions, October 15, 2015, U.S. Department of Transportation
FAA Pilot/Controller Glossary, 8/22/13
ICAO Annex 2 - Rules of the Air, International Standards, Annex 2 to the Convention on International Civil Aviation, July 2005