Cpr light transport experiences altitude excursion on autoplt when #1 vertical gyro fails.

Attributes
ACN	135251
Time
Date	199001
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : c4m
State Reference	MO
Altitude	msl bound lower : 32100 msl bound upper : 33000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zkc
Operator	general aviation : corporate
Make Model Name	Light Transport
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 75 flight time total : 14000 flight time type : 3400
ASRS Report	135251
Person 2
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : overcame equipment problem flight crew : regained aircraft control
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 6000 vertical : 1100
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

We were cruising at FL330 in autoflt mode. At approximately XX52 hours CST, we had an equipment failure which caused the airplane to enter a hard nose down attitude. Recovery was made as rapidly as was possible without over stressing the airplane. The descent was stopped at approximately FL321 and the airplane was returned to the assigned altitude of FL330. During the recovery ZKC advised that we were to maintain FL330. I advised ZKC that we had experienced a gyro failure and the airplane was being returned to FL330. At this time we were climbing through FL325. As I advised ZKC, it was initially believed that the #1 vertical gyro had failed. After return to level flight at FL330 the #2 flight system was placed on line and in-flight troubleshooting was done to determine the extent of the failure. During this action it was determined that in fact the point of failure was the #1 flight director. Upon landing I called ZKC and advised the manager of the problem.

Original NASA ASRS Text

Title: CPR LTT EXPERIENCES ALT EXCURSION ON AUTOPLT WHEN #1 VERTICAL GYRO FAILS.

Narrative: WE WERE CRUISING AT FL330 IN AUTOFLT MODE. AT APPROX XX52 HRS CST, WE HAD AN EQUIPMENT FAILURE WHICH CAUSED THE AIRPLANE TO ENTER A HARD NOSE DOWN ATTITUDE. RECOVERY WAS MADE AS RAPIDLY AS WAS POSSIBLE WITHOUT OVER STRESSING THE AIRPLANE. THE DSCNT WAS STOPPED AT APPROX FL321 AND THE AIRPLANE WAS RETURNED TO THE ASSIGNED ALT OF FL330. DURING THE RECOVERY ZKC ADVISED THAT WE WERE TO MAINTAIN FL330. I ADVISED ZKC THAT WE HAD EXPERIENCED A GYRO FAILURE AND THE AIRPLANE WAS BEING RETURNED TO FL330. AT THIS TIME WE WERE CLIMBING THROUGH FL325. AS I ADVISED ZKC, IT WAS INITIALLY BELIEVED THAT THE #1 VERTICAL GYRO HAD FAILED. AFTER RETURN TO LEVEL FLT AT FL330 THE #2 FLT SYSTEM WAS PLACED ON LINE AND INFLT TROUBLESHOOTING WAS DONE TO DETERMINE THE EXTENT OF THE FAILURE. DURING THIS ACTION IT WAS DETERMINED THAT IN FACT THE POINT OF FAILURE WAS THE #1 FLT DIRECTOR. UPON LNDG I CALLED ZKC AND ADVISED THE MGR OF THE PROBLEM.

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.