Light transport has altitude deviation as told to reduce speed.

Attributes
ACN	198440
Time
Date	199201
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : cle
State Reference	OH
Altitude	msl bound lower : 6750 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : cle
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : cfi
Experience	flight time last 90 days : 275 flight time total : 2750 flight time type : 1250
ASRS Report	198440
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence other
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While at 7000 ft with autoplt engaged, approach told us to reduce speed to 170 KTS. As the throttles were reduced, the aircraft pitched down to a rate of 1200-1500 FPM. I attempted to disconnect autoplt but it took 3 attempts to regain control of aircraft. The autoplt was in heading and altitude hold modes and therefore should hold the altitude of 7000 ft and trim aft as throttles are reduced to maintain speed of 170 KTS. After control was regained our altitude was 6750 ft. I immediately regained altitude back to 7000 ft. My captain is fairly new on the aircraft and may have inadvertently pushed the electrical trim switch forward, resulting in rapid pitch down, while he was attempting to acknowledge ATC to reduce speed to 170 KTS. However, we were uncertain of this and we wrote up the autoplt. I believe that the close proximity of the trim switch to the push to talk switch on the light transport control yoke may have contributed to this occurrence.

Original NASA ASRS Text

Title: LTT HAS ALTDEV AS TOLD TO REDUCE SPD.

Narrative: WHILE AT 7000 FT WITH AUTOPLT ENGAGED, APCH TOLD US TO REDUCE SPD TO 170 KTS. AS THE THROTTLES WERE REDUCED, THE ACFT PITCHED DOWN TO A RATE OF 1200-1500 FPM. I ATTEMPTED TO DISCONNECT AUTOPLT BUT IT TOOK 3 ATTEMPTS TO REGAIN CTL OF ACFT. THE AUTOPLT WAS IN HDG AND ALT HOLD MODES AND THEREFORE SHOULD HOLD THE ALT OF 7000 FT AND TRIM AFT AS THROTTLES ARE REDUCED TO MAINTAIN SPD OF 170 KTS. AFTER CTL WAS REGAINED OUR ALT WAS 6750 FT. I IMMEDIATELY REGAINED ALT BACK TO 7000 FT. MY CAPT IS FAIRLY NEW ON THE ACFT AND MAY HAVE INADVERTENTLY PUSHED THE ELECTRICAL TRIM SWITCH FORWARD, RESULTING IN RAPID PITCH DOWN, WHILE HE WAS ATTEMPTING TO ACKNOWLEDGE ATC TO REDUCE SPD TO 170 KTS. HOWEVER, WE WERE UNCERTAIN OF THIS AND WE WROTE UP THE AUTOPLT. I BELIEVE THAT THE CLOSE PROX OF THE TRIM SWITCH TO THE PUSH TO TALK SWITCH ON THE LTT CTL YOKE MAY HAVE CONTRIBUTED TO THIS OCCURRENCE.

Data retrieved from NASA's ASRS site as of July 2007 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.