PA34 pilot reports runaway electric trim at 6000 ft. Control of aircraft is lost until trim motor ci...

Attributes
ACN	820449
Time
Date	200810
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzzz.airport
State Reference	FO
Altitude	msl single value : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzzz.artcc tower : zzz.tower
Operator	general aviation : personal
Make Model Name	PA-34-200 Seneca I
Operating Under FAR Part	Part 91
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : atp pilot : multi engine pilot : instrument pilot : commercial pilot : cfi
Experience	flight time last 90 days : 90 flight time total : 8550 flight time type : 700
ASRS Report	820449
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : regained aircraft control flight crew : landed as precaution flight crew : declared emergency
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

The aircraft departed IFR; in VMC; on a ferry flight. The autopilot was unserviceable; but electric elevator trim worked. The aircraft was maintaining 6000 ft; as cleared; then recleared to 11000 ft. The electric trim was used to pitch up; but the aircraft started descending; so continuous nose-up trim was selected; to try to correct this. Very quickly; the aircraft was descending at more than 1000 FPM; and required all the pilot's strength to pull the control column back; to avoid pitching down. ATC was advised that it was not possible to climb; due to control problems. The elevator trim wheel appeared jammed in the forward position; and would not move. Greater force was used; the trim wheel was freed; and was set to a position that allowed the aircraft to continue under normal control. The electric trim circuit breaker had popped. ATC was told of the control problem; and that the aircraft was returning to the departure airport. After landing and closing down; the control problem was investigated; and found to be a defective switch on the left-hand control column. If moved forward; the trim wheel motored forward. If moved back; the trim wheel still motored forward. The flight continued the next day; with the electric trim circuit breaker pulled. Comments: the pilot was an experienced CFI; meii; with over 1500 hours of multi time; of which about half was in senecas. It was extremely fortunate that the incident occurred at 6000 ft. If it had happened on takeoff; in IMC; it would have probably caused a crash. This was a very serious (and probably very rare) failure mode of the trim switch. It could have been responsible for unexplained accidents in the past; and I believe it is essential to notify the NTSB of this incident. I suggest a controlled experiment is conducted to replicate the handling characteristics of full forward trim; when using climb power.

Original NASA ASRS Text

Title: PA34 pilot reports runaway electric trim at 6000 ft. Control of aircraft is lost until trim motor circuit breaker trips.

Narrative: The aircraft departed IFR; in VMC; on a ferry flight. The autopilot was unserviceable; but electric elevator trim worked. The aircraft was maintaining 6000 ft; as cleared; then recleared to 11000 ft. The electric trim was used to pitch up; but the aircraft started descending; so continuous nose-up trim was selected; to try to correct this. Very quickly; the aircraft was descending at more than 1000 FPM; and required all the pilot's strength to pull the control column back; to avoid pitching down. ATC was advised that it was not possible to climb; due to control problems. The elevator trim wheel appeared jammed in the forward position; and would not move. Greater force was used; the trim wheel was freed; and was set to a position that allowed the aircraft to continue under normal control. The electric trim circuit breaker had popped. ATC was told of the control problem; and that the aircraft was returning to the departure airport. After landing and closing down; the control problem was investigated; and found to be a defective switch on the left-hand control column. If moved forward; the trim wheel motored forward. If moved back; the trim wheel still motored forward. The flight continued the next day; with the electric trim CB pulled. Comments: The pilot was an experienced CFI; MEII; with over 1500 hours of multi time; of which about half was in Senecas. It was extremely fortunate that the incident occurred at 6000 ft. If it had happened on takeoff; in IMC; it would have probably caused a crash. This was a very serious (and probably very rare) failure mode of the trim switch. It could have been responsible for unexplained accidents in the past; and I believe it is essential to notify the NTSB of this incident. I suggest a controlled experiment is conducted to replicate the handling characteristics of full forward trim; when using climb power.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.