C750 crew had an uncommanded aircraft pitch up and climb while using the aircraft flight guidance sy...

Attributes
ACN	535003
Time
Date	200201
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : ric.vortac
State Reference	VA
Altitude	msl single value : 29000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc.artcc
Operator	general aviation : personal
Make Model Name	Citation X
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 26000 flight time type : 600
ASRS Report	535003
Person 2
Affiliation	other
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude other anomaly other anomaly other
Independent Detector	other flight crewa other flight crewb other other : 3
Resolutory Action	aircraft : automation overrode flight crew flight crew : returned to original clearance flight crew : regained aircraft control flight crew : overrode automation none taken : detected after the fact
Consequence	other
Supplementary
Problem Areas	Aircraft FAA
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft in stable flight at FL290 after descent from fl 410. Autoplt engage with navigation and altitude hold modes captured, speed approximately mach 0.89/340 KTS. ATC issued descent to FL270. Descent initiated using autoplt with vertical speed mode engaged and down wheel selecting 1000 FPM descent, aircraft pitched up and climbed before complete control was regained at approximately FL293. Descent to FL270 completed. There was no communication with ATC regarding altitude, nor any warnings or conflicts. Maybe and should be end of story. But I reported this occurrence to my manager. His response was interesting at best. In that this has 'happened repeatedly' with this type aircraft. 'That installed software (revision 7?) that causes pitch up unpredictably!' 'that new software (revision 8?) is forthcoming and in the mean time nothing to do but be careful.' callback conversation with reporter revealed the following information: the reporter stated at FL290 speed .89 mach. 340 IAS with autoplt engaged to altitude hold, ATC then issued descent to FL270. The reporter said vertical speed mode was engaged and 1000 ft per minute was selected and started to descend when the airplane pitched up and control was regained at FL293. The reporter stated when the incident was reported to the chief pilot the response was 'this happens repeatedly' explaining the problem was in the software. The reporter said neither the company nor the manufacturer has issued any bulletins or information to the crews operating this aircraft. The reporter said no software modifications had been made to date.

Original NASA ASRS Text

Title: C750 CREW HAD AN UNCOMMANDED ACFT PITCH UP AND CLIMB WHILE USING THE ACFT FLT GUIDANCE SYSTEM.

Narrative: ACFT IN STABLE FLT AT FL290 AFTER DESCENT FROM FL 410. AUTOPLT ENGAGE WITH NAV AND ALT HOLD MODES CAPTURED, SPEED APPROX MACH 0.89/340 KTS. ATC ISSUED DESCENT TO FL270. DESCENT INITIATED USING AUTOPLT WITH VERTICAL SPEED MODE ENGAGED AND DOWN WHEEL SELECTING 1000 FPM DESCENT, ACFT PITCHED UP AND CLIMBED BEFORE COMPLETE CTL WAS REGAINED AT APPROX FL293. DESCENT TO FL270 COMPLETED. THERE WAS NO COM WITH ATC REGARDING ALT, NOR ANY WARNINGS OR CONFLICTS. MAYBE AND SHOULD BE END OF STORY. BUT I RPTED THIS OCCURRENCE TO MY MANAGER. HIS RESPONSE WAS INTERESTING AT BEST. IN THAT THIS HAS 'HAPPENED REPEATEDLY' WITH THIS TYPE ACFT. 'THAT INSTALLED SOFTWARE (REVISION 7?) THAT CAUSES PITCH UP UNPREDICTABLY!' 'THAT NEW SOFTWARE (REVISION 8?) IS FORTHCOMING AND IN THE MEAN TIME NOTHING TO DO BUT BE CAREFUL.' CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED AT FL290 SPEED .89 MACH. 340 IAS WITH AUTOPLT ENGAGED TO ALT HOLD, ATC THEN ISSUED DSCNT TO FL270. THE RPTR SAID VERTICAL SPEED MODE WAS ENGAGED AND 1000 FT PER MINUTE WAS SELECTED AND STARTED TO DSND WHEN THE AIRPLANE PITCHED UP AND CONTROL WAS REGAINED AT FL293. THE RPTR STATED WHEN THE INCIDENT WAS RPTED TO THE CHIEF PLT THE RESPONSE WAS 'THIS HAPPENS REPEATEDLY' EXPLAINING THE PROB WAS IN THE SOFTWARE. THE RPTR SAID NEITHER THE COMPANY NOR THE MANUFACTURER HAS ISSUED ANY BULLETINS OR INFO TO THE CREWS OPERATING THIS ACFT. THE RPTR SAID NO SOFTWARE MODIFICATIONS HAD BEEN MADE TO DATE.

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.

C750 crew had an uncommanded aircraft pitch up and climb while using the aircraft flight guidance system.