Unknown Fuel System Problem Leads to Unfortunate Ending

If you don’t know where it went, is it really gone?

Low on fuel without a good place to put down leaves a pilot with few options. Jose Mizrahi/Unsplash

A Cessna 210L left Bozeman, Montana, with five men aboard and full tanks for a 700-nautical-mile flight to San Carlos, California.

Four hours and 48 minutes later, the airplane crashed near Lodi, California, 60 nm short of its destination. The 1,200-hour pilot, 60 years old, died two weeks later of his injuries; the four passengers, also seriously injured, survived. One of them told the National Transportation Safety Board (NTSB) accident investigators that they were about 30 minutes short of the destination when the pilot said that they were getting low on fuel, and he was going to turn around and land at an airport they had just passed. Shortly thereafter, he announced that they needed to find a road to land on. The engine then quit. The pilot switched tanks and tried to restart it but failed.

As the pilot turned back, hoping to reach the airport, the gliding airplane “lost momentum,” in the words of a passenger. It dropped, collided with trees and crashed in a dry riverbed.

The numbers appear difficult to reconcile. Seven hundred nautical miles is well within the range of a 210. Handbook performance gives a fuel consumption of around 14 gallons an hour at 160 ktas. A trip of 700 nm, with allowance for taxi and climb, ought to require around 65 gallons of fuel. The 210L’s tanks have a capacity of 90 gallons; 87 gallons are usable in all flight conditions and probably 89 or more in level flight. What happened to the remainder?

From the fact that the airplane covered 640 nm in 4.8 hours, for an average groundspeed of 133 knots, we can infer that either the pilot used a very low power setting—which seems incompatible with fuel exhaustion—or there was an average headwind of 20 knots. The NTSB report is silent on the subject of en route winds.

Teardown of the engine revealed no mechanical failure, but a seal on the fuel-pump drive shaft was found to be damaged by rust and leaked at the remarkable rate of 3 to 4 gallons an hour. This fuel would have gone to an overboard drain, and this would roughly account for the difference between the theoretical fuel requirement for the trip and the amount actually used.

It is unusual for a crashed airplane to burn if there is no fuel in it. Nevertheless, the fuselage and the inboard portion of the left wing were consumed by fire. The passengers, despite their injuries, had helped extricate one another from the wreckage.

The pilot was not the owner of the airplane. It’s possible that the rate of leakage from the fuel pump suddenly increased just before the final flight. It’s also possible that the owner had been making short flights and had not fully appreciated the catastrophic rate of leakage. Perhaps the owner warned the pilot that the airplane had been using a lot of fuel lately and that he should keep an eye on the gauges. Equally plausible is that the pilot did not have a clear idea of how severe the fuel leakage actually was. At any rate, the accident report says nothing about the pilot’s knowledge, or ignorance, of a preexisting fuel leak.

There are several ways to judge fuel consumption in flight. The manufacturer’s information manual contains tables of fuel flow for various combinations of manifold pressure and rpm at a specified mixture, but obviously cannot consider fuel-system anomalies or variations in leaning technique. The basic fuel-flow gauge actually measures pressure in the fuel-distribution manifold—the little round “spider” on top of the engine—and is inherently imprecise. A digital meter and totalizer keep track of fuel consumption much more precisely, but know nothing of leaks upstream.

The only direct way to know how much fuel is in the tanks is from visual inspection before takeoff and, once airborne, from the fuel gauges. If the gauges do not agree with expected fuel flow, and you do not have positive knowledge they are faulty, you have to believe the gauges.

The pilot found himself in a perplexing position. According to the gauges, the airplane had used a great deal more fuel than it should have. Presumably, he had leaned the mixture; he would have run out of fuel even sooner if he hadn’t. The fuel-flow gauge—the NTSB report does not say what type the airplane had—showed the expected rate of consumption. The engine was running normally, and yet, 60 nm from the destination, both fuel gauges were reading near empty.

It seems that, rather than the normal “both” setting, the pilot had at some point selected the right tank. He probably thought that he would run it dry and then hope to have enough fuel remaining in the left tank to reach an airport. When the right tank ran dry, he switched to the left and tried to restart but failed. Most likely, there was some fuel in the left tank, as suggested by the post-crash fire, but it’s not unusual for an engine to be slow to restart after it has swallowed a lot of air.

From the passenger’s description, it sounds as if the airplane must have been quite low at this point and stalled or mushed in—possibly because the pilot’s attention was divided between flying the airplane and trying to start the engine.

The NTSB’s “probable cause” made no mention of the pilot’s in-flight decision-making. It blamed the accident on “fuel exhaustion due to a leaking engine-driven fuel-pump nose seal, which increased the engine-fuel-consumption rate above the published performance-chart values.”

The implication of the NTSB’s finding is that a pilot would plan a flight based on “performance-chart values” and, after that, have no information about the fuel state. But that is obviously not the case, unless the fuel gauges in the airplane are not working at all. That was evidently not true here because the pilot knew, and stated at a certain point, that the fuel level was dangerously low, and moments later, the airplane ran out of fuel. Apparently, the gauges were working just fine.

So, turn back the clock. Two and a half hours or so into the flight, the gauges would have been indicating half. Something had to be wrong. But what was it? Everything else seemed normal. Were the gauges faulty? Possibly. But an hour and 15 minutes later, they would be indicating one quarter. It was not difficult to extrapolate that, at this rate, the airplane could not possibly reach San Marcos without the gauges hitting rock bottom. That is not a place you want them to be.

Most pilots who run out of fuel do so near their destination. Wishful thinking operates powerfully on our minds, obscuring evidence and distorting reason, so obvious decisions elude us. When fuel appears to be in short supply, there is only one rational thing to do: land and get more of it. But that is not always what pilots do. Instead, they try to make the most of what they’ve got, sometimes with tragic results.

This story appeared in the June/July 2020 issue of Flying Magazine

Peter Garrison taught himself to use a slide rule and tin snips, built an airplane in his backyard, and flew it to Japan. He began contributing to FLYING in 1968, and he continues to share his columns, "Technicalities" and "Aftermath," with FLYING readers.
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