Aviation Safety Letter 3/2004

COPA LogoCOPA Corner — How Much Gas Is Enough?

by Adam Hunt, Canadian Owners and Pilots Association (COPA)

Back in the 1970s, I used to rent a club aircraft that had a sticker on its instrument panel. In orange letters it said, "It is Dumb to Run Out of Gas." There must have been a good reason for the club to have put that sticker there.

Every year, at least a few pilots fail to make it to their planned destination because they simply run out of fuel. Some of these aircraft make precautionary landings at other aerodromes, which is a good choice, while others end up in the trees, sometimes only a few miles short of destination.

Very few of these accidents seem to involve IFR aircraft, and almost none involve helicopters. Most of the accidents in this category involve VFR airplanes.

The rules for VFR airplanes are pretty straightforward. Canadian Aviation Regulation (CAR) 602.88 requires the pilot to start the flight with a fuel reserve of at least 30 minutes at normal cruise in the daytime, and 45 minutes if landing after dark. It also says that you can't change destinations in flight, unless you can still make that requirement. That CAR also says that you need to account for "taxiing and foreseeable delays prior to take-off," "meteorological conditions" (including winds), "foreseeable air traffic routings and traffic delays" and "any other foreseeable conditions that could delay the landing of the aircraft." Despite the rules covering just about every possible reason for doing so, they do not prevent people from running out of gas.

There seem to be many reasons for running out of fuel, but there are some consistent traps that can be avoided. One of these is that many light aircraft fuel gauges are famous for not being accurate enough to be relied upon. Quite simply, if you use light airplane fuel gauges alone to tell you whether you will make it to destination, you will run out of gas sooner or later.

One of the reasons that ultralights seem to be involved in very few fuel exhaustion accidents is that many of them have transparent fuel tanks that allow the pilot to see how much gas they have left while in flight.

Few certified aircraft offer that ability to actually see the amount of gas that is left. That means that the quantity has to be verified, usually by dipstick, before flight and then the clock used as the best indication of how much fuel is left.

Perhaps interpreting the rules themselves brings some pilots to grief. Most pilots will tell you that the CARs require "Fuel for destination plus 30 minutes by day." Actually, the CARs require you to carry fuel to get to destination, account for all possible changes in wind, weather, air traffic control (ATC) clearances and "any other foreseeable conditions that could delay the landing of the aircraft" and then "plus 30 minutes" of fuel in daytime. Just carrying "destination plus 30 minutes" is not enough fuel to be safe every time.

Many prudent light airplane pilots add an automatic reserve of at least one hour. That means with five hours of gas on board (and verified by dipstick), the trip, including possible winds and other delays, cannot add up to more than four hours. If it does, you need an intermediate stop.

By always physically verifying the amount of fuel on board ("dipping the tanks"), and never planning to use the last hour of gas on board, many fuel exhaustion accidents can be avoided.

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