Dick’s Follies #7 — Usable Fuel

Once set into the design, unless changed through the addition of extra fuel tanks, the “fuel hand” you’ve been dealt is the one you will live with — unless you’re Dick.

DICK REALLY DOESN’T CARE ABOUT AIRCRAFT LIMITATIONS. For some reason, limitations just aren’t in his nature to follow, which must be how he came to challenge the absolute limits of his airplane’s endurance. He managed to live through this one, but not by much.

DICK WAS GOING WEST. He had a nice ski trip planned, and had his high performance single directed to Colorado. He had planned a fuel stop on the way there, but his fuel stop was right on the ragged edge of the plane’s endurance. Actually, if Dick had looked closely, he would have discovered that his plans violated the minimum fuel requirements as stated in FAR 91.151:

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.

IN HIS OWN WORDS. Here is how Dick told his story: “I was flying west, and wanted to make it in only one fuel stop, instead of two. I planned to stop at an airport just short of Colorado to fuel up for the push for the final leg.

Once I got airborne, I programmed my LORAN, and followed the course to my destination. The flight was uneventful, and I landed on the first try. I was surprised when the lineman told me that he had to put 70 gallons of fuel into my tanks to fill them up.” (The usable fuel on Dick’s plane is 74 gallons.)

Did Dick bust 91.151? Lets see:

VFR Flight — Check
Night VFR Flight — Check
Fuel Burn during cruise of 13 gallons per hour — Check
Divide fuel burn rate by four gallons usable fuel on board on landing –18 minutes endurance — CHECK


  • A lineman fuels your tanks. Unless you observe the fill and provide direction, what he thinks full is will be how much fuel you get in your tanks. That could leave you light by two additional gallons or more in some cases.
  • Ever see a deer or obstruction on the runway on final? If Dick had, he would have been in trouble. When he went to full power for the go-around, his fuel burn would have jumped to 22 gallons per hour as he climbed back into the pattern. Doing the math, his fuel endurance just dropped 40% to around eleven minutes.
  • What if the destination airport had been socked in by fog, or the runway was closed because of an accident? Dick would have been hard pressed to make it anywhere else on a mere 4 gallons of fuel.
  • How good is your fuel flow meter? Are you willing to bet your life on its reading?
  • The survival rate of a loss of engine power due to fuel exhaustion at night is not exactly good — in fact, it’s pretty darn poor. Even in the west, there are lots of ground obstructions just waiting for your low approach.

DICK GOT LUCKY — AGAIN! REMEMBER, THE FARS EXIST TO KEEP US FLYING, AND NOT BECOMING STATISTICS. In this case, Dick should have had at least one hour of fuel on board. If he had done his flight planning correctly, this would have been a non-issue, but Dick seems to enjoy living on the burning edge.

DON’T BE LIKE DICK. Follow the FARs when it comes to planning your trips. Those FAR-mandated fuel reserves take into account a good amount of uncertainty in winds, fuel flow, tank filling, and safety. By using this approach, and properly planning your fuel use during trips, you will have safe and uneventful flights that will leave your adrenal gland in idle, where it belongs while you are flying.