MU-2 Twin Turboprop Suffers Spate of Recent Accidents

Air Safety Week, May 24, 2004

The fatal May 14 crash of a Mitsubishi Heavy Industries MU-2 on approach to Baltimore Washington International Airport (BWI) casts new doubt on the safety record of this high-speed twin turboprop airplane.

The airplane was carrying a load of cancelled checks, one of the typical missions of this aircraft. Its low acquisition cost - about $200,000 for a used MU-2 - has made the airplane popular among cargo carriers hauling parts, mail, cancelled checks and other small, high-value cargoes. The 34-year old pilot was killed.

The BWI crash marked the 184th MU-2 accident in the United States over the last 38 years. The latest crash brought the number of fatal accidents to 77, in which 246 pilots and passengers have been killed, according to the National Transportation Safety Board (NTSB) accident database.

The BWI crash followed hard on the heels of three MU-2 accidents in March, two of which were fatal. The NTSB now has four ongoing accident investigations into this one aircraft type.

"The MU-2 has a horrendous accident record," declared Ladd Sanger, a Dallas, Texas-based aviation lawyer who has been involved in at least three lawsuits against Mitsubishi emanating from crashes.

Sanger compared the accident rate of the MU-2 to the Beech Super King Air 200, another twin-turboprop of comparable size, in terms of accidents per 100,000 hours flown. By this measure, the MU-2 accident rate over a 38 year period, 1964-2002, is nearly five times higher than the King Air, and about seven times higher in terms of fatal accidents.

Robert Breiling, a Florida-based expert who prepares a yearly accident analysis for corporate aviation, said in a telephone interview with ASW that the MU-2's accident rate exceeds that of the turboprop aircraft fleet overall, but that the Swearingen Merlin accident rate is higher, as measured per 100,000 hours over the last five years, 1999-2003. It should be noted that the MU-2 accident rate cited by lawyer Sanger is slightly higher than the Merlin over the longer period of time on which he bases his statistics.

In any event, the accident rate for the MU-2 and other turboprop aircraft is substantially higher than the accident rate per 100,000 hours for transportcategory aircraft in scheduled passenger service. The NTSB shows for 2003 an accident rate for these Part 121 operators of 0.313 per 100,000 hours, and a fatal accident rate of 0.012. That overall rate for the airlines is about five times lower generally, and more than 40 times lower for fatal accidents, than for the turboprop fleet rates cited by Breiling.

The MU-2 is not exceptional, in terms of the raw number of accidents in the NTSB database involving other medium-size twin turboprops. The accidents are spread among businessmen/owners, air taxi operators, overnight cargo operations, and general aviation. That spread includes part-time non-professionals walking the edge of the weather cliff (notably icing) and making typical inexperiencetype errors (landing gear up, fuel mismanagement, inability to cope with instrument approaches in marginal weather). The biggest risk factor may be the workload in single-pilot IFR (instrument flight rules) operations, although the MU-2 can be unforgiving in high altitude icing conditions, for which additional pilot training has been mandated.

Focusing on the MU-2, what explains its accident history? Of 703 MU-2s built in various models, fully 25 percent have been involved in accidents and 10 percent in fatal accidents, according to Breiling. As of the end of 2003, 488 surviving MU-2s were active worldwide. The airplane is no longer in production. It was built in various models, which might be grouped into two categories. A short-fuselage version and a longer-fuselage version sporting more powerful engines, four-bladed propellers and other improvements.

Sanger, who is a pilot as well as a lawyer, said, "It's a hot airplane and pilots can get in over their heads." As an example, the MU-2 has a faster cruise speed than most airplanes in its class.

That speed comes with a price, declared Donald Kennedy. A retired professor of aerospace engineering who taught aircraft design for some 30 years at the University of Colorado, Kennedy said the airplane is "very squirrelly."

"It needs exceptional skill to fly," he said in a telephone interview. "I don't think it meets the controllability standards for an average pilot." Kennedy was referring to one of the basic requirements for an aircraft to be certified - that its flying characteristics must be such that the airplane can be safely flown by an average pilot.

In a recent paper prepared pursuant to his role as an expert witness in a lawsuit surrounding a January 2000 MU-2 fatal crash on takeoff at San Antonio International Airport, Kennedy argued that the MU-2 has "marginal controllability on one engine at low airspeed and low altitude." His paper argues that the relatively small wings on the MU-2, which minimize drag and help the airplane to achieve its high cruise speed, are not compensated with an increase in engine power (even though later models of the MU-2 featured more powerful engines turning four-blade propellers). These design features, Kennedy maintains, have contributed to the MU-2's loss-of-control accident history.