These wires connected the horizontal stabilizer’s control electronics to the captain’s pitch trim switch and autopilot/trim disconnect button on the Embraer E175. After chafed wires were found on the incident airplane, Republic Airlines voluntarily inspected the rest of its fleet and found nine other aircraft with chafed wiring.
The second example we offer of an unexpected pitch trim system failure involved a Cessna 550 Citation II light twinjet that departed from Milwaukee Mitchell International Airport (KMKE) to Willow Run Airport (KYIP) near Ypsilanti, Michigan, on June 4, 2007. The flight, an air ambulance mission under contract to the University of Michigan Health System, was returning to KYIP with four members of a medical transplant team for an organ transplant at the university medical center.
Immediately after takeoff, the captain, who was the pilot flying (PF) stated, “Why am I fighting the controls here?” Within 30 sec. of beginning the takeoff the captain made a third mention of a flight control problem stating: “What the (expletive) is going on? I’m fighting the controls.”
The first officer (FO) responded by asking: “How’s your trim set? Is that the way you want it?” The captain clarified that the aircraft wanted to turn hard left, and the FO again asked: “How’s your trim down here?” The captain said: “Something is wrong with the trim … the rudder trim.”
Shortly thereafter the FO replied: “How’s that, any better?” The captain responded by saying, “Huh, no, we got a trim problem, tell ‘em we got to come back and land.” Seconds later he yelled: “She’s rolling on me. Help me, help me,” to which the FO responded, “I am!” The captain asked the FO to pull the autopilot circuit breaker, and the FO responded, “Where is it?”
During this struggle for aircraft control the captain said: “You hold it, I’m gonna try to pull circuit breakers.” Nine seconds later the jet impacted Lake Michigan at 243 kts in a steep (42 degrees nose down) left-wing-low attitude. The two pilots and four passengers were fatally injured.
The NTSB found that the accident sequence resulted from a control problem that was related to either an inadvertent autopilot activation or a pitch trim anomaly, the effects of which were compounded by aileron and/or rudder trim inputs. The board’s official causal statement determined that the pilots’ mismanagement of the abnormal flight control situation through improper actions, including failing to control airspeed and to prioritize control of the aircraft, and lack of crew coordination caused the accident.
One important lesson that is especially pertinent when discussing the forces on an aircraft is the reduction in forces when the airspeed is slower. The NTSB determined that if the pilots had simply maintained a reduced airspeed while they responded to the situation, the aerodynamic forces on the airplane would not have increased significantly. At reduced airspeeds, the pilots should have been able to maintain control of the jet long enough to either successfully troubleshoot and resolve the problem or return safely to the airport.
The NTSB investigation determined that pilots would benefit from training and readily accessible guidance indicating that, when confronted with abnormal flight control forces, they should prioritize airplane control (airspeed, attitude, and configuration) before attempting to identify and eliminate the cause of the flight control problem.
The investigation also highlighted the importance of equipping critical circuit breakers with identification collars to enable pilots to more readily identify and activate during an abnormal or emergency situation.
Did Pilot Experience Contribute To Accident?
One of the key questions in an accident investigation is whether the flight crew was adequately trained and experienced. This investigation revealed troubling documentation on the backgrounds and training of the pilots.
The captain of the air ambulance flight had 14,000 total flight hours, with about 12,000 hr. as a professional pilot in a variety of aircraft including the Learjet, Citation, Mitsubishi MU-2, DC-8, DC-9 and Airbus 320, with about 300 hr. in the Citation 500/550 series. His type rating ride for the Citation 500 was initially denied on June 12, 2001 for running off the runway while demonstrating a crosswind takeoff.
On June 8, 2004, the captain of the accident flight was unable to successfully complete the weight and balance portion of the practical test oral exam for a DC-9 type rating. He failed a 14 CFR 135 proficiency check ride on March 29, 2006, after he deployed the thrust reversers prematurely during landing, causing the aircraft to become airborne again after touchdown. The FAA inspector noted that the captain did not have the knowledge of the aircraft’s systems needed for a check airman and did not demonstrate an acceptable understanding of IFR operations and requirements.
Several of his pilot colleagues testified to the NTSB that the captain lacked in-depth aircraft system knowledge and did not always adhere to company procedures or comply with regulations. The board’s review of company records for the most recent training flights conducted by the captain discovered significant discrepancies in the flight time denoted by the captain versus the aircraft’s hour-recording meters that could not be explained by the company or by FAA personnel.
Depending on the cause of unexpected aircraft motion, the correct control inputs must be made immediately, as illustrated by the Boeing 737 Max crashes, in Part 3 of this article.
How To Prepare For Pitch Trim Failures, Part 1: https://aviationweek.com/business-aviation/safety-ops-regulation/how-pr…
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