MD-11 Airliner Is Two Tons Over Planned Weight

The MD-11 passenger jetliner, which McDonnell Douglas began flight testing earlier this month, is at least 4,000 pounds over its target weight, triggering an aggressive effort by the firm to slim down the aircraft.

Although 4,000 pounds of weight growth is far from a calamity for the program, it is significant and would result in the plane having somewhat lower fuel efficiency, lower payload or shorter range, according to aeronautical experts and MD-11 customers.

McDonnell Douglas Vice President Louis Harrington, who disclosed the weight growth in an interview, asserted that the company is not in violation of any contract specifications with airline customers for the MD-11’s range or payload.

“It is a challenge more than it is a problem,” a Douglas marketing executive said Monday. “It is not a disaster, but it is something you wish didn’t happen. The fact that Singapore Airlines just bought this aircraft means they are convinced the problem is under control.”

But a number of customer representatives at the firm’s Douglas Aircraft plant in Long Beach were not quite as sanguine, saying they are concerned about the weight and about delays in the MD-11 program. Douglas is about six months behind schedule and has begun negotiations with at least one customer who is seeking penalties for anticipated late deliveries.

Moreover, the 4,000 pounds of excess weight may turn out to be a low estimate. Some aerospace analysts for securities firms say they have been told by Douglas that the excess weight is closer to 7,000 pounds, and one source at Douglas cited a 6,000-pound figure.

Douglas began development of the MD-11 jetliner, a stretched and updated version of its DC-10, in late 1986 and has spent an estimated $500 million to $700 million to design, develop and build tooling for the program.

The aircraft was flown for the first time Jan. 10 and the flight tests reportedly have gone well. Douglas hopes to have the aircraft certified by the Federal Aviation Administration by this fall and to begin deliveries then.

Harrington said the aircraft has an empty weight target of 290,000 pounds, which does not include payload or fuel. That would suggest that the aircraft actually weighs 294,000 pounds.

A technical data sheet distributed by Douglas earlier this month, however, lists an empty weight of 277,500 pounds. Douglas officials were not available to clarify the discrepancy.

A company spokeswoman said the weight growth resulted from increased structural load requirements imposed by the FAA. Efforts to cut the weight are having some success, since the plane was 5,000 pounds overweight at one point, she said. Aerospace analysts think the weight gain may still be more than 4,000, however.

“I heard it is 7,000 pounds overweight,” said Patricia Trent, aerospace analyst at Seidler Amdec Securities in Los Angeles, adding that she is concerned that the effort to reduce the weight will lead to higher costs.

The aircraft would be 1.4% over its target empty weight, assuming that the 4,000-pound excess would bring it to 294,000 pounds. While 1.4% is not a huge weight overrun, experts say it would result in a drop in the aircraft’s fuel efficiency, a major selling point of the MD-11.

Prof. Richard Kaplan, a University of Southern California vice provost and an aeronautics expert, said that, as a rule of thumb, a 1% increase in an aircraft’s empty weight requires a 1.5% increase in engine thrust to compensate and a resulting 1.5% increase in fuel consumption.

To deal with such a problem, an aircraft’s maximum payload can be reduced by the same amount as the increase in structural weight or the plane can carry less fuel, in either case diminishing the profitability of a jetliner, Kaplan noted. For example, 4,000 pounds is roughly equivalent to the weight of as many as 20 paying passengers, along with their luggage and food.

As a practical matter, however, the MD-11 probably would not ever have to carry its maximum payload or fly its maximum range. Rather, the additional 4,000 pounds would have the effect of reducing fuel efficiency over the life of the aircraft, because it would be like an additional 4,000 pounds of non-paying ballast.

In interviews, representatives of three MD-11 customers at Douglas said they are concerned about the weight issue, although they praised the firm’s efforts to trim the fat.

“They are within tolerance (under the sales contract), but they are still trying to reduce it,” said a representative of one major airline who asked not to be identified. “It is a concern because it reflects additional fuel we will burn over the life of the aircraft.”

Another airline representative said that if Douglas is not successful in cutting the 4,000 pounds, it would represent a problem. “It would cut down the payload or range of the aircraft,” he said. It is quite likely that Douglas will be able to eliminate the excess weight, but it will cost money to do so. Douglas overshot its target weight on its Air Force C-17 transport aircraft by 8.2% or roughly 20,000 pounds. The C-17 is still in development.

The effort to cut the C-17’s weight cost millions of dollars because new engineering drawings had to be produced, subcontracts modified and tools altered in some cases. It also caused a delay in the program.

The Douglas spokeswoman said the company is dealing with the MD-11 weight problem by reducing aerodynamic drag, “improving” the engines and by “manipulation of weight factors,” an apparent reference to lighter-weight materials.

Kaplan noted that aircraft programs often run overweight because engineering departments simply run out of time to reduce weight during the design process. The MD-11 is already six months behind schedule.

Managing the weight of new aircraft is one of the most tricky aspects of new aircraft programs. Most aircraft manufacturers have a weight department and a separate structures department; the two groups often battle each other ferociously. The structures department sets a goal to build a strong and durable craft, while the weight department struggles to keep the craft within targets that will allow it to be profitably operated.

“Many aircraft have failed in history because they were overweight,” Kaplan noted. “Profit margins for airlines are rather slim.”