<< >> NASA ASRS Report 471340, April 2000

A lear 24 in cruise at FL270 with autoplt engaged experienced a hard over pitch and loss of 400 ft caused by the left stall warning system.

Attributes
ACN	471340
Time
Date	200004
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : orl.airport
State Reference	FL
Altitude	msl single value : 27000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zma.artcc
Operator	common carrier : air carrier
Operating Under FAR Part	Part 135
Navigation In Use	other vortac
Flight Phase	cruise : level
Route In Use	enroute airway : j53.airway
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : instrument pilot : multi engine pilot : atp
Experience	flight time last 90 days : 200 flight time total : 10000 flight time type : 150
ASRS Report	471340
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : commercial
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly
Independent Detector	aircraft equipment other aircraft equipment : altimeter other flight crewa other flight crewb
Resolutory Action	flight crew : landed as precaution
Consequence	other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

The first officer was hand flying the aircraft when he experienced a 'hard over.' we lost approximately 400 ft (26600 ft) before the stall warnings could be turned off. When the stall warnings were disconnected we climbed approximately 800 ft (approximately 27400 ft) before we were able to get the aircraft back to FL270. We opted to land at daytona beach, fl, to research the problem. We had no further problems. Callback conversation with reporter revealed the following information: the reporter stated the cause of the pitch hard over was the left stall warning system sensing a stall. The reporter said the autoplt reacted to the stall and pitch the aircraft over. The reporter said maintenance replaced the left stall warning sensor.

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Original NASA ASRS Text

Title: A LEAR 24 IN CRUISE AT FL270 WITH AUTOPLT ENGAGED EXPERIENCED A HARD OVER PITCH AND LOSS OF 400 FT CAUSED BY THE L STALL WARNING SYS.

Narrative: THE FO WAS HAND FLYING THE ACFT WHEN HE EXPERIENCED A 'HARD OVER.' WE LOST APPROX 400 FT (26600 FT) BEFORE THE STALL WARNINGS COULD BE TURNED OFF. WHEN THE STALL WARNINGS WERE DISCONNECTED WE CLBED APPROX 800 FT (APPROX 27400 FT) BEFORE WE WERE ABLE TO GET THE ACFT BACK TO FL270. WE OPTED TO LAND AT DAYTONA BEACH, FL, TO RESEARCH THE PROB. WE HAD NO FURTHER PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE PITCH HARD OVER WAS THE L STALL WARNING SYS SENSING A STALL. THE RPTR SAID THE AUTOPLT REACTED TO THE STALL AND PITCH THE ACFT OVER. THE RPTR SAID MAINT REPLACED THE L STALL WARNING SENSOR.

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.