We’ve all been there. All of a sudden the fuel gauge is the most important instrument in the plane. Our eyes start fixating on it every few minutes trying to find comfort in a remaining fuel supply that is now in question. Then comes that anxious feeling in the pit of our stomach when we realize that we are in a race. We may be doing 200 miles an hour, but that ever so slow moving needle is trying to beat us to the finish line.
I investigate about 4 for 5 fuel exhaustion events every year and there is a certain sameness to these events. Most of these accidents occur during the day, under good weather conditions, and within a mile or two of the airport that the pilot originally intended to land at (close only counting in horseshoes). Sometimes the pilot planned only to make a quick hop that turned out to be shorter than expected because of “air contamination” in the tanks. Usually the aircraft is a total loss.
All too many of these accidents have occurred because the pilot guessed, rather than knew, the exact amount of fuel on board prior to departure. Yes, you can look into that dark filler neck, but the information is seldom meaningful unless you can see that the level is full or at a specific quantity point as identified in the POH. You wouldn’t think that a fuel level being just an inch low is a big deal, but in the Cessna P210 I fly, if the fuel fill is only an inch low in each tank, I’ve short-changed myself 20 gallons which is about an hour closer to empty. The best procedure to verify fuel quantity is to use a calibrated dipstick or siphon tube.
Most of our E6B’s start collecting dust soon after we pass that first check ride. We become familiar with the machines we fly and start using mental shortcuts for fuel planning: “Let’s see, my Cessna 152 burns around 6 gph @ 100 mph so I can easily go 2 hrs or 200 miles with 24 gallons on board.”
A lot of the comfort factor we think we have in our quick calculations can easily be eroded by ATC delays, headwinds, or deviating for weather. How about if the destination airport is suddenly unavailable because the airplane ahead of you just had a gear-up landing and the runway is now closed. Can you make it to an alternate? Some alternates are few and far between.
Pilots often fail to take into account the extra fuel burned during time on the ground with the engine running or the significantly higher fuel flow at take-off and climb power. In my Cessna P210, as an example, the average cruise burn is about 17 gallons per hour, but at take-off and climb power the engine is respectively chugging 30 and 23 gallons per hour. Flights that involve multiple take-offs and landings and/or climbs to high altitudes will consume much more fuel than you are accustomed to.
Well we do have fuel gauges don’t we? Yes, but even the most accurate gauges, along with their electronic fuel totalizer brethren are only reference devices. They often work just fine and are good to the last drop of fuel, but they are not flight planning devices and usually don’t cause fuel exhaustion accidents. Consider that even jet airliners with state-of-the-art equipment and highly trained crews have run out of gas. Here are four tips to keep you out of the woods:
- Start with knowing exactly how much fuel you have before you get in the plane.
- Plan your fuel stops before the flight. Once underway, pilots are usually more tempted to “press on” rather than make an unscheduled pit stop.
- Always land with at least an hour of fuel remaining. For example, if you calculate a four-hour endurance to start with then you should be on the ground in no more than three hours. The clock is always the best fuel gauge.
- Have your fuel quantity gauges calibrated and treat anything less than ¼ tanks as a warning to land as soon as possible.
If the worst happens and you are coming up short, declare a “minimum fuel advisory” or “emergency” with ATC for expeditious handling or vectors to the nearest airport. If fuel exhaustion appears imminent, try to find a spot to make an off-airport landing. Better to do so while you still have some power remaining. If the engine does quit, maintain a level flight attitude, put the boost pump on and switch tanks. You might be able to get a little more juice.
In flying, when things start to go wrong they often to do so in a slow and subtle manner. It gives us an opportunity to recognize a deteriorating situation and apply a corrective action. In fuel exhaustion accidents you are given the greatest lead-time of all: the time it takes for the fuel needle to go from one end of the scale to the other.
Remember the old saying, “In flying, you can’t have too much fuel unless you are on fire.”
Editor’s Note: This article was written by Ken Steiner prior to his retirement from the United States Aircraft Insurance Group as a Vice-President and Claims Manager. During his career, Ken investigated thousands of aircraft accidents involving small planes, crop dusters, helicopters, corporate aircraft, and airliners. He has been on-site at over 100 fatal aircraft accident investigations. He is currently an Aviation Investigative Consultant and is also a Pilot and Tactical Flight Officer for the San Mateo County Sheriff’s Air Support Unit. He owns a Cessna 182 based at San Carlos and holds ATP and CFI certificates with over 5000 flying hours.