Why the fire in a perfectly healthy jet engine can die.

Air & Space Magazine

In the early afternoon of May 24, 1988, TACA Flight 110, a Salvadoran Boeing 737 arriving from Belize, was picking its way among thunderstorms ringing New Orleans when the unthinkable happened: Both of the airliner’s jet engines quit. Frantically, the crew members tried to restart them. At first they thought they had succeeded: Okay, one crew member radioed to controllers as the craft descended through 4,000 feet, we’ve got both engines back now. But relief evaporated less than a minute later. The engines would not accelerate from idle speed, and dangerously rising tailpipe temperatures forced the crew to shut them down again.
I don’t think that I will make it, I don’t have any power on the engines here sir, so I guess we having to go down, we have to go down, we declare emergency....

TACA 110, there is the interstate highway directly ahead of you....

I don’t believe we gonna be able to make it there sir, we’re at 2,000 and we’re losing altitude.... The only thing I do right now is make a 360 and I’ll land over the water sir.

TACA 110, I show your altitude now 700 feet.

Seven minutes later another airplane, at the request of the air traffic controller, flew over the area where the 737’s radar target had disappeared. The pilot caught sight of the airliner incongruously parked on the embankment of a levee beside Lake Borgne, its escape chutes deployed. With remarkable airmanship, Captain Carlos Dardano had dead-sticked the 737 onto a mile-long patch of rain-soaked earth. The airplane and its passengers were unharmed.

What happened to TACA 110 is called a flameout. The term is casually used for any failure in a turbine engine, but its technical meaning is more narrow: power loss not associated with a mechanical failure. A flameout of one kind or another is thought to occur once in every 100,000 non-military flights.

Three things are needed to keep a jet engine going: fuel, air, and the heat to make them burn. Removing any of the three can cause a flameout. In the case of TACA 110, what was taken away was the “activation energy”—the heat. The engines had been throttled back for descent, and their supply of internal heat was minimal; heavy rain and hail simply doused the fire. The event was not unique. Nine months earlier, an Air Europe 737 descending through rain and hail over Thessaloniki, Greece, had suffered a double flameout. In that case, the crew managed to restart the engines and land without trouble. In 2002, a Garuda Indonesia 737, also descending among thunderstorms, suffered a double flameout over Java. Its crew ditched the airplane in a river; one person died, and there were a dozen serious injuries.

Water and ice aren’t the only things that can turn off the fire in a jet engine. Unexpectedly, so can fuel. Obviously, running out of fuel is a good way to stop an engine, but too much fuel can have the same effect, if it comes from the wrong place.
Walt Larimer, a retired U.S. Air Force navigator, remembers an incident from the late 1950s in Morocco. An F-100 pilot, a novice at aerial refueling, couldn’t get hooked up to Larimer’s KB-50J tanker. It took many attempts, but the pilot finally managed to engage the refueling drogue, only to fracture the coupling at the end of the fueling hose a moment later. Jet fuel began to stream out. The fighter, whose engine air intake is in its nose, dropped back and inadvertently slurped up some JP-4. A muffled explosion could be heard from inside the F-100, and flames emerged from its front and rear ends simultaneously. The fighter, its engine spooling down, dropped from sight while a fellow pilot who had been waiting for his turn at the hose shouted restart instructions.

Larimer later learned that the hapless pilot of the stricken jet failed to restart the engine. But he managed to glide back to his base and make a successful dead stick landing on the runway—a semi-miraculous accomplishment in an F-100.

Only a military pilot during a refueling operation is likely to encounter stray JP-4. For the rest of us, the atmosphere can contain even more insidious antagonists. Since 1980, the year Mount St. Helens in Washington state erupted, there have been at least 100 instances of airliners encountering clouds of volcanic ash, often hundreds of miles from the source; the clouds have done more than $250 million in damage to airplanes that unwittingly entered them. In two cases, passenger-carrying Boeing 747s have lost all power in all four engines. The first, a 1982 British Airways flight, glided from 37,000 to 14,000 feet in darkness over the south Pacific Ocean before its crew managed to restart the engines. The second, involving a KLM airplane in 1989, took place in Alaska; there too the pilots managed to restore partial power and land safely.

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