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In his last three years at Portland Air Base, Ed Pennell received the highest marks for "problem solving" and "work skills" on his annual performance evaluations.

Photo by Tanisha Wallace-Porath

King-56's four engines lost power and flamed out 86 minutes into its flight from Portland to San Diego.

King-56 had plenty of fuel, according to Air Force investigators. But they say all four engines mysteriously stopped receiving fuel.

Follow Up: Wrong Again?

Critics cite another flaw in the Air Force investigation of the King-56 crash.

By Bob Young, byoung@wweek.com

Two aviation experts say military investigators made another major error in their findings on the cause of last year's crash of a Portland-based Air Force plane known as King-56.

In their April 24 accident report, investigators concluded that King-56's engines quit because of "fuel starvation"--although they couldn't determine what caused the problem.

But it's possible--and two sources say likely--that the King-56 crash was caused by air starvation, not an absence of fuel.

"I would go before any court and say that's exactly what happened," says Ed Pennell, who capped a 30-year career as an Air Force mechanic by serving as the Portland Air Base's top maintenance superintendent in 1990.

Pennell's air-starvation theory is supported by a former high-ranking Air Force safety official who did not want to be named.

If the two are correct, it marks the second significant error that investigators made in reaching their conclusions about the accident that killed 10 of 11 Air Force reservists aboard the C-130 transport plane ("Why Did These 10 Men Die?" WW, June 18, 1997).

The first was dismissing the testimony of a pilot, Major Walt Mulder, who suggested that King-56 was brought down by an electrical glitch known as "four engine rollback."

Air Force investigators insisted that four engine rollback couldn't cause the plane's four engines to flame out, or quit, but they were contradicted by an Air Force safety bulletin issued the day after the King-56 accident report was released. The safety memo clearly warns that four engine rollback, or power loss, can lead to flameout.

The air-starvation scenario--outlined by Pennell and the former Air Force safety official--is consistent with Mulder's testimony and goes like this:

A voltage drop in the plane's electrical system causes a malfunction in a computerlike device called the synchrophaser, which controls the plane's propellers.

Thinking the propellers are over-speeding, the malfunctioning synchrophaser sends a signal to the propellers telling them to decrease their revolutions-per-minute.

When RPM decreases to a certain point, the engines' "bleed valves" open, depriving the engines of compressed air, which in turn causes them to flame out.

"Any time you bleed air off from a combustion engine, you're taking power away," Pennell explains. "If you bleed air off, you can pump all the fuel you want, but eventually the engine is going to shut down."

Col. Rick Davis, commander of the Portland-based 939th Rescue Wing, disagrees with the air-starvation theory. Davis argues that the evidence provided by the flight data recorder in effect rules out air starvation.

"I'm surprised he even said that to you," Pennell says. "He should know better."

Pennell and the unnamed source counter that the flight data recorder shows precisely the right indications for air starvation.

Davis admits he's not an expert on the C-130. The Portland base commander is a helicopter pilot by training. Because of his lack of expertise, Davis gathered three instructor pilots with more than 20,000 total hours flying C-130s. Those pilots echoed his views, saying that the air-starvation scenario, as outlined, was not plausible because that's not the way the synchrophaser works.

"The point," Davis concludes, "is that no one knows why [the plane crashed]. To say you do know is dogmatic."

Two other developments in the King-56 story surfaced last week.

First, Pennell says he read about the synchrophaser problem in 1986--six years before Mulder said he saw a safety alert on the problem. That means the Air Force has failed to fix a problem it has known about now for 11 years.

Second, Air Force safety documents obtained by WW support Pennell's assertion. The documents list all synchrophaser and engine rollback accident reports for C-130s since 1986. The reports detail 22 cases of engine rollback caused by synchrophaser malfunctions. (The documents reveal another 18 cases of engine rollback in which a cause was undetermined.)

Most cases of engine rollback were corrected when the crews threw the circuit breakers on the synchrophasers as Mulder described in his testimony.

It's not clear if the King-56 crew executed that procedure. Lone crash survivor Sgt. Bobby Vogel told investigators he thought the crew threw the circuit breakers, but he couldn't be sure.

But even if the crew had thrown the circuit breakers, there's no guarantee that would have ended the problem.

In one 1990 case, the Air Force documents say, a pilot had to direct his flight engineer to actually "remove the synchrophaser from the equipment rack to ensure that the synchrophaser was disconnected from the aircraft's electrical system."

Only then, the Air Force reported, did the engine problems cease.

In its recent safety bulletin, issued after the King-56 investigation, the Air Force added a new final step to its emergency procedures, telling C-130 crews to "remove the synchrophaser from its mount and stow it away" to make sure it did not continue to malfunction--even after it had been disconnected from its power supply.

Pennell is astonished that the Air Force has not taken more decisive steps after clearly identifying the synchrophaser's tendency to malfunction. "If something is such a continued problem and can kill you," he says, "you'd think they'd fix the damn thing."