The crash of an Air Midwest twin-turboprop has pushed the cumulative toll of those killed from maintenance errors to more than 3,040 over the last three decades, raising new questions about maintenance oversight as well as concerns about passenger and baggage weights used in determining takeoff weight.
The Jan. 8 crash of the Beech 1900D twin-turboprop during takeoff at Charlotte, N.C., already has spurred the Federal Aviation Administration (FAA) to issue an emergency airworthiness directive on elevator rigging and to order operators of aircraft carrying up to 19 passengers to validate passenger and baggage weights by March 13. The case is under investigation by the National Transportation Safety Board (NTSB).
Maintenance work was performed on the airplane’s elevator control system two days before the crash. Investigators have recovered the cables, control rods, bell cranks and such from the crash site. According to a Jan. 27 NTSB situation report:
“Examination of the elevator control cables revealed that the turnbuckle on the ‘down’ elevator cable was offset to nearly full extension and the turnbuckle on the ‘up’ elevator cable was near the fully retracted position, a difference of 1.8 inches. The turnbuckles are used to set cable tension and are typically adjusted to about the same length.”
Unconfirmed reports indicate that the contract technician who performed the work was doing so for the first time, and for the first time on this particular model of airplane. The crash occurred on the ninth flight two days later. The preliminary evidence suggests that the cables might have been routed such that there was tension in the “take up” direction (i.e., back-stick or rearward movement of the control column), but possibly a lack of tension in the “stick forward” direction. For reasons of passenger comfort, pilots achieve descent attitudes airborne by reducing power (nose drops naturally) and nose-down trimming; full stick forward is only checked on the ground (i.e., not under air loads).
In the case of this particular aircraft, the rigging was such that the pitch control position sensor showed a 10� nose-down shift. In other words, a yoke or stick forward control input would have hit the stops sooner. This likely would not have been noticed during the flights between the maintenance action and the accident when the airplane was more lightly loaded.
Because the aircraft was heavily laden for the accident flight, it is likely that the pilot would have needed – or would have required – full back column for rotation. It is possible that at full up elevator deflection a cable may have come off a pulley and jammed, leaving the elevator itself in the near full nose-up position.
At a press conference NTSB member John Goglia expressed his “personal opinion” that the yoke likely was “stuck” at the near full back position on rotation.
A pulley-jumped cable-jam would have caused the yoke to seize in the rearward position and the aircraft would continue to pitch up, which it did to the point of stall at about 52� above the horizontal.
The FAA issued an emergency airworthiness directive Jan. 27 requiring Beech 1900, 1900C and 1900D operators to conduct control column sweeps and other rigging checks by Jan. 31 (AD No. 2003-03-18):
“If maintenance procedures are not properly followed … it may appear to the crew that they have full elevator control column movement,” the AD said. It went on to caution, “However, the elevator may not have full travel. Such restricted travel may remain undetected until the airplane is operated in a loading condition that requires full elevator authority to control the pitch.” (Emphasis added) Regarding the weight issue, preliminary accounts indicate that the airplane was within 100 pounds of its 17,000- lb. maximum takeoff weight and within one percent of its rearward center of gravity. However, the weight is based on average weights applied to passengers and baggage.
On the same day the emergency AD was issued, the FAA ordered operators to conduct spot checks for purposes of validating average passenger and bag weights used in determining payload weight in 10-19 seat passenger aircraft.
Meanwhile, as the investigation grinds forward, the crash has all the earmarks of maintenance error as the precipitating event. If so, the 21 killed in the crash bring to 3,048 the number of people killed in maintenance-related airliner crashes. That is the toll amassed since 1974, when incomplete application of a service bulletin caused the cargo door to blow open on a Turkish DC-10, resulting in the deaths of all 346 aboard, according to a compilation by this publication (see ASW, Aug. 12, 2002).
Already litigation is in the air. A lawyer formerly with the FAA declared his intent to file suit soon on behalf of bereaved families.
The Air Midwest crash features a number of similarities to the crash of an Emery Worldwide Airlines DC-8 freighter three years ago. That airplane, too, crashed on takeoff due to an improperly rigged horizontal stabilizer control.
Weight Validation
FAA Notice N8400.40, Jan. 27, 2003 (extracts)
To maintain confidence in the average weights contained in the Weight and Balance Control Program, operators of 10 to 19 passenger seat aircraft must sample passenger weights, carry-on baggage weights, and checked baggage weights over a three consecutive day period that consists of a Sunday, Monday and Tuesday. The validations will be accomplished by sampling 15% of the operator’s flights and distributed evenly throughout the day, from 30% of their city pairs … distributed equally across its geographic route structure.
The passenger weights may be obtained by weighing each passenger or asking each passenger their weight and adding 10 pounds.
If sample weights are greater than the weights contained in the approved Weight and Balance Program, the operator must use the new average weights.
A report outlining the results of the average weight validation and the cargo compartment … restraint system inspection shall be [submitted within] 45 days of [publication] of this notice.
Police the Problem or Get Sued
Statement of Michael Pangia, Esq.
I am a trial attorney specializing in aviation cases. I am representing family members relating to deaths in the Air Midwest accident. I have both an airline transport pilot certificate and aircraft and powerplant mechanic’s certificate, and I was formerly the head trial lawyer for the FAA and U.S. Justice Department, Aviation Trial Unit.
It is too soon to conclude that this accident was due to a mechanical problem or to an overweight or weight distribution problem. Nevertheless, this accident points to long- standing and dangerous practices loading smaller aircraft. With a heavier generation of people, the volume of luggage checked in and an increase in the quantity and weight and, more importantly, where that weight is located, determining takeoff weight has become a matter of guesswork rather than careful calculation.
It took this accident and the loss of life to prompt the FAA to direct its inspectors to conduct a survey by having carriers weigh passengers and baggage over a three day period on 15% of the carriers flights distributed over the day, cities and routes. The impact will go into modifying, if necessary, the carrier’s Weight and Balance Control Program contained in the approved operating specifications. The survey is also supposed to determine whether baggage is stowed and secured properly.
What is a major concern is a tendency of many aircraft such as the Beech 1900 to be loaded too tail heavy. If a problem occurs such as loss of power, loss of airspeed or some unforeseen mechanical problem that affects the controls, the tail heaviness can become the initiating cause of a crash.
While the FAA may be subject to criticism for not policing this problem sooner, the responsibility for maintenance, operation, and proper loading of these aircraft falls directly on the airline. Regulations may technically allow weight estimations rather than actual weight, but it is not enough that minimum regulations are met when safety may require doing a lot more. Expediency does not excuse that duty.
>> Pangia, e-mail [email protected] <<