Dual Engine Failure Could Be the Cause

One of the Concorde’s four engines may have burst under the strain of takeoff, taking out a second engine and precipitating a low-altitude stall from which the delta-winged jetliner could not easily recover, said two aviation experts who were studying Tuesday’s crash near Paris.

“The failure of a single engine wouldn’t cause loss of control, but the failure of two could,” said Barry Schiff, a retired TWA pilot and aviation safety consultant. “The delta wing on that plane is very unforgiving at takeoff speeds.”

“Theoretically, the plane would still have been able to fly,” said Glen Shoop, a retired Concorde pilot. “But in that situation, it would have been very difficult to control.”

Schiff and Shoop said their theories about the crash of Air France Flight 4590 are speculation--based largely on their experience, the reports of a professional pilot who watched the crash, and a photograph showing flames trailing from at least one of the Concorde’s engines.

The official determination of the cause--based on the study of radar data, debris, witness reports, maintenance records and on-board recordings that officials have recovered from the wreckage--probably won’t be made for a year or more.

The Concorde’s four Rolls-Royce engines, each developing about 38,000 pounds of thrust, were at full power as the sleek supersonic jet lifted off from Paris’ Charles de Gaulle airport shortly after 4:30 p.m. Tuesday.

Engineers said it is at just such a moment, when jet engines are producing maximum thrust, that they are most likely to break down.

Witnesses on the ground, backed up by a dramatic color photograph taken by a tourist, described a 100-foot plume of fire streaming back from the engine area on the left wing as the jetliner struggled into the air.

“In almost every case, it’s the worst possible time and the worst possible set of circumstances for an airline crew to deal with,” said David Thomas, a former head of accident investigation for the Federal Aviation Administration.

Schiff said that the Concorde has pairs of engines on each side of the fuselage, “and the engines in each pair are very close to each other, side by side. If a turbine burst on one of those engines, it could take out the other one.”

“When one of those engines comes apart, it can throw pieces everywhere,” Shoop said.

Witnesses--among them a Federal Express pilot--said the plane appeared to stall, pitching up steeply into a nose-high attitude before falling off to one side and crashing into a hotel in the town of Gonesse, about nine miles northeast of Paris.

“The pilot’s report that the plane pitched up, rolled and pitched down sounds like the classic stall scenario for a delta-wing airplane,” Schiff said.

A stall occurs when the smooth flow of air over a wing is interrupted, depriving the wing of lift.

Schiff said the plane’s delta-shaped wing design--unique to the Concorde among the world’s commercial jetliners--makes supersonic flight possible, but it also makes recovery from a low-altitude, low-speed stall especially difficult.

Rudder Problems

Although Tuesday’s crash was the first involving the Concorde, the planes have suffered mechanical problems in the past. Since 1989, three of the supersonic transports, or SSTs, have lost large sections of their tail rudders in flight, but the structural integrity of the planes was not affected, and all three landed without incident.

The Concorde traces its origins to 1956, when British and French engineers first began drawing up plans for a commercial jetliner that could dramatically reduce the flight time between New York and London by more than half. Under a joint development program adopted in 1962, it was agreed that the British Aircraft Corp. and France’s Aerospatiale would build the plane. Development costs would end up topping $2.8 billion.

Aircraft engineers in the United States toyed with the idea of an SST before abandoning the plan in 1971 as unworkable and overly expensive. The Soviets developed their own SST--the Tupelov 144, which many thought looked suspiciously like a blueprint copy of the Concorde--but that effort came to a quick and tragic end when one of them crashed at the Paris Air Show in 1973.

By the time the Concorde began commercial flights in 1976, enthusiasm for SSTs was on the wane.

The plane carries only 100 to 110 passengers, while the Boeing 747, developed during the same period, can handle 400. Despite carrying only one-fourth of the 747’s payload, the Concorde burns the same amount of fuel crossing the Atlantic. Concordes must undergo 22 hours of maintenance for every hour of flight, while 747s undergo about seven.

Concern About Ozone

Then there are the ecological drawbacks. Cruising at 55,000 to 60,000 feet, the Concorde spews pollutants at altitudes where ozone concentrations are of special concern. And its cruising speed of 1,350 mph--roughly Mach 2--creates sonic booms that can crack plaster and shatter glass on the ground.

The United States refused to let the Concorde fly across this country at supersonic speeds.

Braniff airlines opted for a subsonic Concorde leg from New York to Dallas, but the effort ended within a few months. Shoop, who flew that Concorde leg, was a Braniff pilot until the airline folded. Other airlines, including American, Lufthansa and Air Canada--dropped their purchase options, and of 70 Concordes originally slated for production, only 16 were built. After Tuesday’s crash, only 12 remain in service.

In the end, only Air France and British Airways continue to fly the planes. And for the fortunate few--Madonna, David Frost, Margaret Thatcher and Joan Collins among them--willing to pay about $5,000 apiece for one-way, 3 1/2-hour hops from New York to London or Paris, the journey apparently is worth it.

The seats are leather, the champagne is vintage, and the food is outstanding.

Pilots love the Concorde.

“It’s complex, but once you learn to fly it, it flies real good,” said Ken Larson, another former Braniff pilot. “It’s one hell of an airplane.”

“I think it’s the finest plane ever built,” Shoop said Tuesday night. “What happened today is just breaking our hearts.”