Required reserves and 'normal cruising speed'
Let's review the rules. Federal Aviation Regulation (FAR) 91.151 specifies the fuel requirements for an airplane flight in VFR conditions:
No person may begin a flight in an airplane under VFR conditions unless (considering wind and forecast weather conditions) there is enough fuel to fly to the first point of intended landing, and assuming normal cruising speed
- During the day, to fly after that for at least 30 minutes;
or - At night, to fly after that for at least 45 minutes.
In a rotorcraft, there must be enough fuel on board to fly to the first point of intended landing and for 20 minutes thereafter, day or night.
By regulation, then, weather and wind must be considered in estimating the duration of the intended flight. And, the normal cruising speed of the aircraft must be assumed in calculating the reserve. A pilot may not consider some lesser, more fuel-efficient speed in calculating the fuel reserve required.
FAR 91.167 specifies the fuel requirements for IFR conditions:
No person may operate a civil aircraft in IFR conditions unless it carries enough fuel (considering weather reports and forecasts and weather conditions) to
- Complete the flight to the first airport of intended landing;
- Fly from that airport to the alternate airport; and
- Fly after that for 45 minutes at normal cruising speed or, for helicopters, fly after that for 30 minutes at normal cruising speed.
Again, the regulation requires that weather and normal cruising speed be considered. The regulation also provides some relief from this minimum fuel requirement under limited circumstances. If certain good weather conditions are expected at the destination airport, and if the destination airport has a standard instrument approach procedure, then the pilot does not have to include the flight to the alternate airport in fuel calculations. The weather reports or forecasts for the destination airport, for at least one hour before and one hour after the estimated time of arrival, 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. This is sometimes remembered as, simply, "1, 2, 3."
Suppose a pilot consults the appropriate aeronautical charts, the manufacturer's performance charts, and the weather reports; determines how much fuel should be on board the aircraft before departure; and then puts exactly that amount in the aircraft's tanks. What happens if the pilot completes the flight but lands with less than the reserve required? In other words, what happens if the aircraft burned more fuel than planned? This could occur as a result of some unexpected event that prolonged the duration of the flight.
A few years ago, the FAA attempted to argue that the amount of fuel remaining on board on aircraft after it landed may be used to establish that the minimum fuel requirements had not been met. However, the NTSB declined to accept the FAA's argument, finding that it was incumbent on the FAA to show that the planned flight time was invalid or unreasonable--not that the flight, in fact, took longer and used more fuel than reasonably anticipated. So, it seems that a pilot's reasonable estimates will be what determines a violation of FARs 91.151 or 91.167.
Be sure to calculate your minimum fuel requirements according to the rules--identify the flight route and distances, apply normal cruise power settings for the particular aircraft, and consider timely weather reports--and make sure that at least the calculated minimum amount of fuel is in the tanks when you depart. Always remember that the fuel that you left back at the airport does you no good, regardless of what it costs these days.
Kathy Yodice is an attorney with Yodice Associates in Washington, D.C., which provides legal counsel to AOPA and administers AOPA's legal services plan. She is an instrument-rated private pilot.
Related Articles
