Engine Part Possible Clue in Jet Crash

A detached thrust reverser from an engine has been found amid the wreckage of a chartered jetliner, providing another possible clue as to why the plane, loaded with American soldiers going home for Christmas, crashed shortly after takeoff here last week, killing all 256 aboard.

Peter Boag, chief investigator for the Canadian Aviation Safety Board, confirmed Tuesday that the thrust reverser had separated from a hinge connecting it to the engine frame but downplayed the significance of the discovery.

At a news conference, he said there is “still no evidence” that the reverser on the right outer engine, a deceleration device that helps to slow the plane on landing, had shifted into operating position during takeoff or during the brief moments of flight before the Arrow Air DC-8 jetliner crashed.

“It is still too early to attach any significance to this observation,” he said.

The jetliner was carrying eight crew members and 248 U.S. soldiers, members of the 101st Airborne Division returning to Ft. Campbell, Ky., after six months of peacekeeping duty in Egypt’s Sinai Peninsula, when it crashed after a refueling stop at Gander International Airport in the province of Newfoundland.

Boag, who responded to a report in the New York Times that investigators were focusing on the thrust reverser as the cause of the crash, confined his remarks to the condition of the reversers on each of the plane’s four engines after the crash.

The outer right reverser had separated from its hinge, he said, but he declined to comment on whether such separation meant that the reverser actually “deployed”--or went into operation.

He said that of the three other reversers, one was found in its normal retracted position and the two others were so severely damaged that investigators could not determine their position.

Clamshell-Like Device

The reverser, a clamshell-like device, closes directly behind the engine, deflecting its normally rearward, propulsive thrust in the opposite direction and producing a braking effect.

Boag declined to rule out the possibility that the thrust reverser was deployed, and one aviation safety expert, John Galipault, said such a deployment could explain the airplane’s flight path after it took off.

Safety Board officials, while revealing few details about their findings, have reported that the ill-fated jetliner made a 20-degree turn to the right and reached only the relatively low airspeed of 165 knots before losing altitude and crashing into a lakefront forest half a mile beyond the runway.

Galipault, president of the independent Air Safety Institute in Columbus, Ohio, said deployment of a thrust reverser could account for the turn, the low air speed and the subsequent crash.

‘A Lot of Drag’

“When it deploys, it produces a lot of drag,” Galipault said. “Not only does it cause a degradation in air speed, it throws the plane out of line . . . (and) the deployment of a reverser on the right would pull the nose around to the right. . . .

“With all of that happening at a low altitude, right after takeoff, it would be awfully tough to fly out of it,” he added.

Galipault said that while a reverser could have been deployed by the impact of the crash, he “doubted it,” because “the wing would have had to hit the ground in just the right way for that to happen.”

Most probably, Galipault said, “it would be some sort of malfunction--electrical or hydraulic--within the control system. That sort of thing has happened before.”

In Washington, a high government safety expert said that if the thrust reverser was fully applied, “it would put the airplane in a serious situation.”

‘Slamming on the Brake’

At the same time, he said, it is “almost physically impossible” for pilots to engage the thrust reversers inadvertently. To engage them, the pilot has to pull the power levers back to idle and then use the reverse thrust levers. “It would be like going down the highway at 60 m.p.h. and taking your foot off the accelerator and slamming on the brake,” he said.

He said he considered it unlikely that the thruster on the DC-8 could have deployed on takeoff because the plane then would have gone down the runway sideways. He did not rule out some mechanical failure, saying “a series of failures would have to occur” to cause a thruster to deploy on its own.

And, even if the thrust reverser fell off the plane, he said, it is unlikely that such a separation could cause such a catastrophic failure.

Other Possibilities Cited

This safety specialist said other possibilities should not be ruled out as the cause of the crash, including an accumulation of ice on the wings that could seriously impair the plane’s ability to gain lift. Canadian officials have said the DC-8 pilot did not have the wings of the craft de-iced before takeoff; of the other pilots taking off at the same time from Gander, some chose to de-ice, some did not.

Another aviation safety expert who has followed the details of the accident in Gander said he believes that there was a glaze of ice on the wings and probably on the tail of the plane. He said that because the plane had been flying at a high altitude on its overseas flight to Gander, its exterior already was cold, making it even easier for freezing rain or ice to adhere to the plane’s surface. He speculated that if there was ice on the plane, the crew may not have checked the plane carefully, perhaps didn’t see a thin film of ice in the early morning light, or didn’t recognize what it was.

1 Accidental Deployment

Only one accidental deployment of a thrust reverser on a Pratt & Whitney JT3D engine--the model used on the Arrow Air DC-8--has been reported in the last five years, according to damage reports filed by airlines with the Federal Aviation Administration.

In that incident, on Oct. 12, 1983, the No. 2 engine of a Boeing 707 went into reverse thrust while the plane was at cruising altitude. The pilot shut the engine down and the plane landed safely. Mechanics later blamed the failure on a bad latch.

Partly deployed thrust reversers were cited in at least two other FAA damage reports filed between Jan., 1980, and last July.

Reversers were also cited in a handful of other incidents, ranging from uncontrolled engine surges to a rightward yaw during one landing, but accidental deployments were not involved in those cases.

Boag emphasized that there would be no further commentary from Gander and that any additional inquiries should be directed to the board’s headquarters in Ottawa. Board personnel in Ottawa declined to amplify on Boag’s remarks and indicated that no additional information was expected in the immediate future.

Times staff writers Penny Pagano and Michael Wines in Washington also contributed to this story.