Pilot Counsel

IFR fuel requirements

April 1, 2007

AOPA's legal counselor John S. Yodice owns a Cessna 310, which he uses for business and pleasure.

Last year in this column I reviewed in some detail the regulation that specifies the minimum fuel required for flight in IFR conditions (see " Pilot Counsel: IFR Fuel Requirements," June 2006 Pilot). This was part of a continuing review, from time to time, of the operating and flight rules for general aviation pilots and owners.

Since the June column, a very helpful AOPA member pressed the FAA for an interpretation of the fuel computation required for the instrument approaches that are inevitably part of the IFR flight. The interpretation is not so obvious from a reading of the regulation, and it is not one that is commonly understood by instrument pilots.

The question is, if an alternate airport is required, must there be sufficient fuel carried on board to make approaches at both the destination airport and the flight's final landing at the alternate? The FAA now answers yes. This interpretation, along with my earlier column, provides a more comprehensive review of this important flight rule.

Here are the specifics of the rule. FAR 91.167(a), "Fuel requirements for flight in IFR conditions," provides, "No person may operate a civil aircraft in IFR conditions unless it carries enough fuel (considering weather reports and forecasts and weather conditions) to (1) Complete the flight to the first airport of intended landing; (2) Except as provided in paragraph (b) of this section, fly from that airport to the alternate airport; and (3) Fly after that for 45 minutes at normal cruising speed or, for helicopters, fly after that for 30 minutes at normal cruising speed."

The paragraph (b) exception allows a pilot to eliminate from his or her computation the fuel necessary to fly from the first airport to the alternate if the first airport is expecting generally good weather and if it has an instrument approach. In that case the basic rule is simply that enough fuel must be carried to land at the destination airport plus a 45-minute reserve (30 minutes for helicopters). The precise conditions that must be met to eliminate the leg to the alternate are: The first airport must have a standard instrument approach procedure (or a special instrument procedure issued to the aircraft operator); and, for at least one hour before and one hour after the estimated time of arrival, the relevant weather reports/forecasts must indicate that the ceiling will be at least 2,000 feet above the airport elevation and visibility will be at least three statute miles (the familiar memory device of "1-2-3"). For helicopters, at the estimated time of arrival and for one hour after that, the ceiling must be expected to be at least 1,000 feet above the airport elevation, or at least 400 feet above the lowest applicable approach minimums, whichever is higher, and the visibility must be expected to be at least two statute miles.

Now to the newly minted interpretation. Notice that nowhere in paragraph (a) of the rule, quoted above, do the words "instrument approach" appear. But the words that do appear, "complete the flight to the first airport of intended landing; (2) Except as provided in paragraph (b) of this section, fly from that airport to the alternate airport," certainly imply the possibility of an instrument approach or two. Obviously, the flight will not land at both airports.

So, one realistic interpretation has been that the wording of the regulation allows for a pilot to plan fuel for an approach and landing at either the destination or the alternate (in addition to fuel required to arrive at the destination, fly to the alternate, and then hold for 45 minutes).

But the FAA in its interpretation takes a more cautious stance. According to the FAA, sufficient fuel to "complete the flight to the first airport of intended landing" under (a)(1) includes fuel for approach and landing (or missed approach). If a landing is not made, "the missed approach fuel used in attempting to land at the destination airport equals, for the purposes of this rule, the fuel to land the airplane."

"To promote aviation safety, the FAA's rule assumes the pilot will attempt to land at the destination airport and then fly to the alternate for the ultimate conclusion of the safe flight. This reasonable scenario includes an approach at both the destination airport and the flight's final landing at the alternate. The FAA believes marginal weather conditions change rapidly. A pilot may start an approach to the destination airport with adequate minimum weather, but the weather may change and force a missed approach. Accordingly, the FAA rules require fuel for approaches at both the destination and alternate airports [my emphasis]."

It is probably worth stating a few related reminders from my earlier column reviewing the whole rule. Remember that in calculating the fuel requirement a pilot must assume "normal cruising speed" taking into account weather reports and forecasts and weather conditions.

Based on a past interpretation, the FAA would likely consider it "normal," and in compliance with the regulation, to use the same cruise speed (and hence the same cruise configuration) for computing the required fuel reserve as that you use for the flight itself. The FAA would likely not consider it "normal" to select the most fuel-efficient cruise configuration in figuring the required reserve if that is not the cruise configuration used for planning the rest of the flight.

I also noted in the earlier column that in past enforcement cases the FAA and the NTSB were critical of a pilot's reliance on "eyeballing" the fuel quantity in the tanks of a rented aircraft, and were also critical of the pilot's relying on the fuel gauges of that aircraft. They said that when a fuel tank is not full, or up to a calibrated tab, the best way to establish the amount of fuel on board is with a calibrated dipstick. So, if a pilot experiences a fuel shortage, the "eyeballing" or fuel-gauge explanation may not carry the day.

On the other hand, I also observed that merely landing with insufficient fuel, by itself, does not constitute a violation of FAR 91.167. In a past case, the NTSB made clear: "Inasmuch as the [FAA] did not establish that the [pilot's] planned flight time was invalid or unreasonable, it is of no consequence, for purposes of determining whether the [pilot] began the flight with the fuel reserves required by FAR section 91.167, that the flight took longer than was anticipated and, as a result, the aircraft landed with less fuel than had been estimated."

Happy landings.

John S. Yodice