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FAA Glossaries

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Fuel for VFR and IFR Flight

14 CFR §91.151 Fuel requirements for flight in VFR conditions.

  • (a) 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—
    • (1) During the day, to fly after that for at least 30 minutes; or
    • (2) At night, to fly after that for at least 45 minutes.
  • (b) No person may begin a flight in a rotorcraft 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, to fly after that for at least 20 minutes.

14 FR §91.167 Fuel requirements for flight in IFR conditions.

  • (a) 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.
  • (b) Paragraph (a)(2) of this section does not apply if:
    • (1) Part 97 of this chapter prescribes a standard instrument approach procedure to, or a special instrument approach procedure has been issued by the Administrator to the operator for, the first airport of intended landing; and
    • (2) Appropriate weather reports or weather forecasts, or a combination of them, indicate the following:
      • (i) For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the estimated time of arrival, the ceiling will be at least 2,000 feet above the airport elevation and the visibility will be at least 3 statute miles.
      • (ii) For helicopters. At the estimated time of arrival and for 1 hour after the estimated time of arrival, the ceiling will be at least 1,000 feet above the airport elevation, or at least 400 feet above the lowest applicable approach minima, whichever is higher, and the visibility will be at least 2 statute miles.

Summary

You may not begin a VFR flight in an airplane unless you have enough fuel to arrive at the first point of intended landing (your destination) and then fly at normal speed for 30 minutes during the day and 45 minutes at night. The regulation covers the planning of the flight. If weather or winds change en-route you do not have to land if you do not have the required reserves.

No person may operate an airplane in IFR conditions—this is not the same as under an IFR flight plan—unless they have enough fuel to arrive at the first point of intended landing (your destination), then fly to the alternate airport, and fly after that for 45 minutes at normal cruising speed. The 1-2-3 rule determines whether an alternate is required. For 1 hour before or after the ETA the ceiling is forecast to be at least 2,000′, and visibility is at least 3 statute miles.

Notice the subtle differences between the two rules. VFR flight may not begin unless the required minimums are met. IFR flight may not continue unless the required minimum reserves are maintained. Both VFR and IFR operations require checking the wind and weather forecasts. IFR operations must consider actual weather conditions, and if conditions change such that the reserves will not be met, the pilot has an obligation to land. The FAR doesn’t explicitly say this and gives no guidance as to how the pilot should make the decisions as to where to land. The NTSB reports are full of accidents that occurred because the pilot did not adhere to this rule.

Real World Reserves

Mike Busch
Mike Busch, who runs his T310 Lean of Peak, does a lot of cross-country flying. He describes his fuel reserve strategy in conjunction with his leaning approach. If my objective is to go far, then I lean so that my GPS-coupled fuel totalizer system shows forecast fuel remaining at my destination to be not less than my target minimum fuel reserve (which for me is one hour of fuel at cruise fuel-flow). If the totalizer forecasts that I will arrive at my destination with less fuel than this, then I lean further until the totalizer does show enough reserve fuel. If I find that I cannot lean enough to achieve the necessary fuel-reserve figure without experiencing engine roughness, then I know I’ll need to make a fuel stop. Note that he continually assesses his reserves using the fuel totalizer and GPS and lands if he finds that he does not have a 1 hour reserve.

John Deakin
My personal absolute minimum fuel remaining with excellent weather, lots of airports very close to my destination, and when I’m feeling frisky, is 10 gallons, in my own airplane. I know how much fuel each tank holds to the tenth of a gallon, exactly where it is during flight, and how much I’m burning, with several cross references to back that up. That meets the regulatory requirement, and it meets mine, but you can bet I’m paying attention during that last hour or two! Link His Bonanza V35 burns around 12.7 gph in cruise, which is about 47 minutes.

The FARs require a minimum of 45 minutes fuel remaining at night, 30 minutes in the daytime, and 20 minutes for helicopters. I think most of us can agree those are NOT conservative figures! Only under very unusual circumstances will I approach those limits deliberately.Link

Anonymous ASR Report

I was able to determine that we had more than a gal of fuel after landing at INS AFB. … Climbing to altitude and maintaining altitude must have taken more fuel. The engine was leaned and checked regularly. To keep this from happening again to me, I will always carry 2 hours of fuel extra… Link

Bo Henriksson

Bo relates an experience that we can learn from. I’ve also revised my personal fuel reserves, realizing that the FAA-mandated ones are just that — minimums. I don’t plan to ever land with less than an hour in the tanks, irrespective of the circumstances. Worse weather mandates more padding and this has done wonders for my ulcer.

NBAA Reserves

NBAA reserves show up in flying magazines all the time when the specs for business aircraft are presented.

The NBAA IFR Reserves is defined as the route of flight in the profile that begins at the “K–L” leg and goes through to the end of the flight profile. This is where the aircraft begins its missed approach to divert to an alternate.

The “K-L leg” of the profile is a 200 NM distance that is done at an optimum rate of climb to 5,000′ after missed approach, holding for 5 minutes at loiter power for clearance, optimum rate of climb enroute to optimum cruise altitude, economy cruise to alternate, and then a descent enroute to Sea Level at 3,000 feet per minute max and land. Upon landing, fuel reserve should meet IFR minimums as appropriate for loitering at 5,000 feet.

Basically, this is a way to compare the endurance of different aircraft on a consistent basis and doesn’t really have anything to do with legal reserves.

Bingo Fuel

This is a military term that first I ran across while researching this article. The same day I read a Flying Magazine article referencing the term when a pilot decided to fly to the alternate rather than attempt a landing in deteriorating weather. We’re at bingo fuel right now, so I guess we’ll mosey over to Orlando. (Flying – Oct 2008, Dick Karl). Bingo Fuel is the fuel required to return to base on a mission, or alternatively to fly to the divert field. Here is a story of someone who got painted into a corner and went below bingo fuel. Here is another.

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