Recurrent Training

Fuel Exhaustion

The perils of mismanagement

It seems incredible that pilots run out of fuel. After all, we're trained from day one to carefully plan, calculate, and manage our fuel supply. The task is not unduly demanding. Yet, as surely as the sun rises and sets, engines fail because of fuel exhaustion, sending pilots on a desperate search for a good off-field landing site.

Proper fuel management begins with preflight preparations: obtaining weather information, selecting a route, and using the aircraft performance data to calculate the required fuel. To this, we must add a fuel reserve that will enable us to deal with the unexpected or contingency situations. During preflight, we must ensure we actually have the required fuel.

Once in flight, we must operate the engine controls properly so our craft will indeed meet the planned performance numbers. And proper management of fuel quantities using the fuel selectors and transfer/boost pumps is critical to this goal.

We must also monitor the flight to see that we are making the planned progress, and that our reserve fuel is not being depleted because our flight is taking longer than planned for whatever reason. If it is, we must make a new plan in a timely manner.

All of these actions represent links in a chain that secures our safety. Failure on our part in any of these steps in the fuel management process can violate the integrity of the chain.

Faulty Fuel Indications

On our very first lesson, instructors show us how to strain, drain, and visually ascertain our fuel supply, and they provide numerous warnings and anecdotes designed to teach us never to trust our fuel gauges. But beware, visually checking fuel quantity is not always as simple as it appears.

The pilot of a Piper PA-24-250 Comanche used a dip stick to check the fuel quantity. But since the aircraft was parked tail-low on an incline, the reading was inaccurate. The pilot ultimately made a wheels-up landing approximately two miles short of the destination airport.

Lesson learned: Read the pilot's operating handbook and all placards to make sure you know how to fill the tanks and how to visually check the quantity.

Inadequate Reserves

Perhaps one aspect of the fuel exhaustion syndrome lies in the Federal Aviation Regulations (FARs) themselves, which may lull us into a false sense of security when determining fuel reserves for a flight.

FAR 91.151, Fuel Requirements: VFR Flight, says we cannot fly an airplane unless we have enough fuel to reach our intended destination, and then fly at normal cruise speed for "at least 30 minutes" during the day or "at least 45 minutes" at night. The instrument fuel reserves are a bit stricter. FAR 91.167 says we must have enough fuel to: "(1) Complete the flight to the first airport of intended landing; (2) Fly from that airport to the alternate airport; and (3) Fly after that for 45 minutes at normal cruising speed...."

These FAR fuel reserves are not "target" fuel reserves that should be used for planning purposes. They are the bare minimums allowed only in the best of conditions and situations. Weather is unpredictable, technology cannot be blindly trusted, and humans are not infallible. As the following cases illustrate, 30-minute, 45-minute, or even an hour fuel reserves may not be adequate.

The pilot of a Piper PA-22-108 Colt stated that he had adequate fuel to reach his destination, but during the arrival, he had to circle in the vicinity of the airport while he attempted to activate the pilot-controlled runway lighting. While circling, the aircraft lost power due to fuel exhaustion and crashed into the trees during a forced landing attempt. Although a test of the aircraft lighting system revealed no problems, the pilot said he had been having problems with his radios.

Lesson learned: Don't let distractions interfere with monitoring of critical systems such as fuel. When troubleshooting, keep track of the time.

Inattention

Inattention — complacency — is another factor in fuel mismanagement. In the following case, the aircraft burned fuel at almost precisely the advertised rate. Unfortunately, the pilot did not see a developing situation in time to enact a new plan, and the aircraft flew longer than the full fuel capacity would allow.

The pilot of a Beech BE-76 Duchess was on the return leg of a round trip flight, and headwinds added an hour to the trip. The pilot became aware of the headwind late in the flight and decided to divert to an alternate. The Duchess lost power due to fuel exhaustion about a half-mile from the runway's threshold.

In examining the wreckage, inspectors found approximately 2 gallons of fuel. The Duchess has a total capacity of 103 gallons, of which 100 are usable. Calculations of fuel consumption for the flight showed that the aircraft should have burned 98.8 gallons from the time of departure to the engine failures.

Lesson learned: Keep track of progress according to your flight plan. If you see a problem developing, act early in the game to develop a new course of action.

External Pressures

It's easy for a pilot to succumb to outside pressures, such as a demanding, impatient passenger or approaching bad weather. These pressures can lead pilots to depart without proper preparations. The pilot-in-command (PIC) must in all cases be responsible for the safe operation of the aircraft and must exercise his or her authority - even if it means bucking the system.

The pilot decided not to refuel his Cessna 150 prior to departure due to an approaching thunderstorm. The pilot had to navigate around three more thunderstorms during the flight. Since his fuel was running low, the pilot decided to divert to an alternate, but the engine quit on final.

Lesson learned: Don't be pressured into an uncomfortable situation. Especially when weather looks marginal, carry extra fuel.

Mismanagement

Even when planned fuel reserves are adequate, pilots must still read the charts and operate the aircraft systems correctly. In these final cases, such mismanagement may have been the weak link which caused the chain to fail.

The pilot had just completed a 2.9-hour, two-leg cross-country flight and was on downwind when the Cessna 150 experienced a complete loss of power due to fuel exhaustion. An investigation revealed that the aircraft had been flown .7 hours prior to this trip and had not been refueled following the first leg of the cross-country. The PIC may have transposed the numbers for the fuel burn and based the flight planning on a fuel burn of 4.6 gallons per hour rather than the correct figure of 6.4.

Lesson learned: Double-check your calculations with a sanity check by asking, "Does this make sense?" Always leave a healthy margin for error.

The pilot performed fuel consumption calculations for the flight and determined that, according to the performance charts, the Piper PA-28-181 Archer had a 5-hour, 42-minute endurance. He took off with full tanks; 4 hours, 32 minutes later, approximately six miles from his destination, the engine quit due to fuel exhaustion.

The pilot said the Archer's clock was slow, and that the fuel gauges were inaccurate. He also explained that his procedure for adjusting the mixture is to lean it until the engine begins to run roughly, then richen it until the engine runs smoothly. The aircraft performance charts specify the use of an EGT (exhaust gas temperature) gauge as a reference. The aircraft had an installed EGT.

Lesson learned: Read the fine print, and know what performance data is based on.

The pilot said he departed with 65 gallons of fuel; he didn't elaborate on how the fuel quantity was determined. The Cessna 182E, which has 60 gallons of usable fuel, will fly approximately 5.4 hours at 60 percent power at 10,000 feet mean sea level (MSL). The pilot had been airborne for 3 hours, 10 minutes and was 22 miles from his destination when the engine quit. Examination of the aircraft following the forced landing revealed that the fuel selector was between the "Both" and "Left" tank positions.

Lesson learned: Know your systems and the correct operating procedure. Know and follow the emergency procedures when needed.

The Bottom Line

Fuel exhaustion continues to be the No. 1 cause of engine failure. It often results in serious aircraft damage, personal injury, or fatalities. Fuel exhaustion is also one of the most easily preventable causes of accidents. For whatever reason, pilots too often leave the ground with insufficient fuel. Perhaps it's time to rethink our fuel strategies, plan for more problems aloft, and make sure we have the fuel to deal with them.

Bob Rossier holds a single- and multi-engine land ATP certificate, commercial single-engine seaplane certificate, and instrument and multi-engine instructor certificates. He's an active flight instructor and an FAA accident prevention counselor.