3rd October 2005

Minimum Fuel Situation

Jeanne McElhatton -- Source: PIA Air Safety Publication

Few inflight problems are guaranteed to raise the concern of pilots and controllers alike as much as the prospect of an aircraft running out of fuel. In the period following the Avianca accident in January of 1989 (where Avianca Flight 52 crashed short of its destination after running out of fuel), the ASRS has seen a rise in the number of reports that concern "low-fuel" conditions. Reports may detail the confusion and communications breakdown among flight crews and controllers about what is meant by a "minimum fuel" situation. In more than a few situations, conscientious and understandably vigilant controllers have elevated to emergency status what the flight crew intended only as an advisory.

" While holding we decided to divert to LGA [La Guardia] and were asked of our fuel status. We told NY [New York] ARTCC it was fifty-five minutes, which would take us to our reserve fuel. But, apparently, this was interpreted as a minimum fuel situation. We never mentioned 'minimum fuel','critical fuel', or emergency of any sort. Only on downwind to LGA, approximately thirty minutes later, did I become aware that something was out of the ordinary when we were told that the final was twenty miles long, and if we needed less to please let them know. We said that would be okay, but wondered why they even asked us that. Upon landing, we noticed that the emergency equipment was standing by."

Given ATC's reaction to what they may perceive as a critical fuel condition in this incident report, it's not surprising that pilots might hesitate to use the term "minimum fuel". Flight crews tend to feel that a controller response such as the one illustrated above will create mounds of paperwork, and they certainly wish to avoid that. This flight crew never even used the phrase "minimum fuel", but their flight was handled as an emergency because they had mentioned their limited fuel status.

Sometimes, however, the scene plays the other way and the message does not get through even though stated clearly. The flight crew must then declare minimum fuel and request priority.

" Shortly after reaching cruising altitude of FL 330, we were given a long delaying vector 90 degrees to our route of flight, followed by several more vectors. At this point we asked if the vectors would continue, because we were burning most of our contingency fuel. We were promised this would be the last vector and [were] handed over to ZAU [Chicago ARTCC]. ZAU immediately initiated more delaying vectors, [which] caused us to declare minimum fuel and ask for priority handling into ORD [Chicago-O'Hare].... If priority handling was not asked for, I am certain we would have burned considerably more fuel and possibly had a more serious fuel situation."

This flight crew stated their developing fuel condition; however, this information may not have been relayed to the next controller. Both controllers and pilots have a mixed perception of, and perhaps response to, the term "minimum fuel".

The Pilots's Perspective

Pilot expectation of the use of the term "minimum fuel" is most often Air Traffic Control (ATC) assistance by way of direct routing, minimal or no holding, and no off-course vectors, but this expectation is not always operationally feasible. Minimum fuel does not mean priority handling to all pilots; it most certainly does not of itself indicate emergency.

Some pilots are very disturbed because they do not receive expected assistance when stating minimum fuel. Others are disturbed because a controller appears to unilaterally declare an emergency and give priority handling.

One pilot suggests that controllers do not really understand the term "minimum fuel". He might well have included pilots in that statement.

" ... When it became apparent that I was going to have to go into my reserve fuel, I informed the Controller that we were 'minimum fuel'. He asked if I was declaring an emergency, and I told him no. He then asked for my fuel status in minutes and I told [him] forty-five minutes. Later in the approach I heard another airliner being given a vector to make room for a priority fuel. I believe that ATC unilaterally declared an emergency for me without informing me, giving rise to my belief that they do not understand the minimum fuel statement as outlined in the AIM."

Interpretation and semantics appear to be a major part of the great expectations mix-up. Terminology played a roll for this flight crew:

" Approaching the VOR we were told to slow and expect a hold. The Captain decided, wisely, that we would be fuel critical if we held the thirty minutes and then proceeded ... we were turning inbound second turn in holding. [The] Captain informed Center we needed to divert. [The] Center informed us we were now cleared direct if we wanted it. We took that routing. On switch over to Chicago Approach, Approach asked if we were declaring an emergency; [we] told them no. An interesting conversation took place regarding our fuel. The expression 'fuel critical' was used. Finally, Approach informed us [the term] fuel critical was an emergency, and they were declaring an emergency [on our behalf]. If fuel critical means you have an emergency; we were not fuel critical. I think minimum fuel would have been more appropriate in our situation."

Note the reporter's belated assessment of his choice of terminology. His final thoughts are correct; this would have been precisely the proper use of a minimum fuel declaration.

Controller Perceptions

What is the controller perception and/or expectation when "minimum fuel" is used? One Controller's response was "Minimum fuel doesn't mean a thing to me". Another, and opposite response, is "Understand you are declaring an emergency". Controllers are also prone to ask if assistance or emergency equipment is needed. They most often try to offer assistance, and may even declare an emergency - much to the flight crew's dismay.

"... The Captain stated he would be unable to accept the continued delay vectors as we were approaching 'minimum fuel'. The ATC Approach Controller gave us direct LGA and squawk 7700. At that time the Captain stated we were not declaring an emergency. The ATC Controller stated that he was declaring the emergency, and again gave us direct LGA and squawk 7700...."

Conflict

Controllers declare emergencies -- pilots resist the declaration, but expect priority handling. There is an obvious misconception in the use of the term "minimum fuel". The phrase does not require, order, or demand priority handling; however, many pilots have come to use the term as if that is what it does mean - the "Great Expectation". A pilot writes:

"... A second problem is that ATC did not give
priority handling when we advised them of minimum fuel."

Just as pilot and controller expectations may be quite varied, you can see their that responses are equally so. When information is passed from controller to controller, some information may get lost or misinterpreted. Each party, controller and pilot, has a specific job to accomplish. Those jobs can be accomplished with understanding, cooperation, and professionalism.

" After several attempts to acquire an EFC [expect further clearance] time or an indication of what delays were in effect, and with no definite reply, the Captain explained that fuel might be a problem. The Controller asked if [our] flight was declaring a 'minimum fuel state'. The Captain [then] declared 'minimum fuel'. Shortly thereafter, [the] flight received clearance to its planned FL330 and was given clearance enroute. With the subsequent helpful assistance from ATC, the flight proceeded to BOS [Boston] with no further problem."

Take AIM

Let's review what the Airmen's Information Manual (AIM) states regarding minimum fuel.

5-85 Minimum Fuel Advisory

a. Pilot

1. Advise ATC of your minimum fuel status when your fuel supply has reached a state where, upon reaching destination, you cannot accept any undue delay.

2. Be aware this is not an emergency situation, but merely an advisory that indicates an emergency situation is possible should any undue delay occur.

3. Be aware a minimum fuel advisory does not imply a need for traffic priority.

4. If the remaining usable fuel supply suggests the need for traffic priority to ensure a safe landing you should declare an emergency account low fuel and report fuel remaining in minutes. (Reference - Pilot/Controller Glossary, Fuel Remaining).

Note that this portion, referencing pilots specifically, states this advisory does not imply a need for traffic priority. What to do if the need for traffic priority develops? The message is clear - declare an emergency.

Let's carry on with part (b) of the 5-85. Minimum Fuel Advisory, and see what is recommended for the controller.

b. Controller

1. When an aircraft declares a state of minimum fuel, relay this information to the facility to whom control jurisdiction is transferred.

2. Be alert for any occurrence which might delay the aircraft.

Note that the minimum fuel declaration is an advisory only, it is not a specific request for priority handling. It should be considered a "yellow caution flag" indicating future problems may develop if undue delays occur.

Air Traffic Procedures Handbook

Air traffic controllers may not refer to the AIM on a regular basis, but ATP 7110.65 references minimum fuel:

MINIMUM FUEL - Indicates that an aircraft's fuel supply has reached a state where, upon reaching the destination, it can accept little or no delay. This is not an emergency situation but merely indicates an emergency situation is possible should any undue delay occur.

Advice for Pilots

What can you do if minimum fuel gets you?

1. Monitor fuel consumption and have an alternate plan if things don't look as if they will turn out as planned.

2. If you decide that a minimum fuel situation exists, or is likely to exist at some point down the line, determine the point beyond which you will not continue in accordance with the original flight plan and what your alternate plan of action will be.

3. Communicate! Tell ATC exactly what your situation is, and make sure they understand it. Inform the controller how long you can continue on their original clearance or route before a diversion becomes necessary, restate the situation to the new controller on a handoff, or otherwise clarify the situation if appropriate. Consider advising ATC on each successive frequency that a minimum fuel situation exists. Note the following communication that kept ATC aware of the minimum fuel situation.

4. Plan ahead - don't wait until fuel is critical and the situation really does become an emergency.

5. Finally, remember the declaration of an emergency does not put you on trial. It may require a report to the company, or a "letter" to the FAA Administrator (only if requested), or it may not require a thing.

Advice For Controllers

What can you do to reduce both risk and frustration?

1. Be aware of the nuances of a minimum fuel statement. What is the flight crew really saying? You may need to question the flight crew until the situation is mutually understood.

2. Remember to relay to the next controller the "minimum fuel" status of any aircraft.

3. Keep your expectations within the limitations of the advisory on minimum fuel.

So, take a fresh look at the term "minimum fuel". Do you and the AIM interpret it the same way?

Final Thoughts

One ASRS reporter presented an interesting suggestion that would keep everyone informed of an unusual or abnormal fuel state:

" ... [I] believe that an aircraft that is in a situation other than [a] completely normal fuel state should be assigned a specific transponder squawk that is clearly and universally defined to both pilots and controllers, [which] ... [indicates the low fuel] situation to all."

Excellent food for thought. This suggestion would keep communications to a minimum, would be passed along on the data block from sector to sector, or to another facility. The pilot could be asked to state specifics of the situation, which would hopefully clarify the situation for all parties. An interesting proposal to consider.

It has also been suggested that the FAA develop an ATC computer enhancement that keeps track of flying time remaining - as stated by the pilot during minimum fuel situations. At an appropriate time before fuel exhaustion, the aircraft's computer data block would flash intermittently to remind the controller of the flight's fuel status before it reaches the critical stage.