Gulfstream giv has an altitude deviation during test flight in rvsm airspace.

Attributes
ACN	732509
Time
Date	200703
Place
Locale Reference	atc facility : zla.artcc
State Reference	CA
Altitude	msl single value : 41000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla.artcc tower : zzz.tower
Operator	general aviation : corporate
Make Model Name	Gulfstream IV
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : cfi pilot : atp pilot : commercial
Experience	flight time total : 11100 flight time type : 580
ASRS Report	732509
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

After maintenance work problems; I took the giv for a test flight to 41000 ft where we experienced a pressure and autoplt malfunction. The aircraft started a 2000 ft vertical descent. I disconnected the autoplt and corrected back to assigned altitude then reengaged the autoplt. At this time ZLA had cleared us to FL370. We started down to 37000 ft. The autoplt would not capture so I disconnected autoplt again and returned to 37000 ft but the ZLA center controller had cleared us lower to 35000 ft.

Original NASA ASRS Text

Title: GULFSTREAM GIV HAS AN ALT DEV DURING TEST FLT IN RVSM AIRSPACE.

Narrative: AFTER MAINT WORK PROBS; I TOOK THE GIV FOR A TEST FLT TO 41000 FT WHERE WE EXPERIENCED A PRESSURE AND AUTOPLT MALFUNCTION. THE ACFT STARTED A 2000 FT VERTICAL DESCENT. I DISCONNECTED THE AUTOPLT AND CORRECTED BACK TO ASSIGNED ALT THEN REENGAGED THE AUTOPLT. AT THIS TIME ZLA HAD CLEARED US TO FL370. WE STARTED DOWN TO 37000 FT. THE AUTOPLT WOULD NOT CAPTURE SO I DISCONNECTED AUTOPLT AGAIN AND RETURNED TO 37000 FT BUT THE ZLA CTR CTLR HAD CLRED US LOWER TO 35000 FT.

Data retrieved from NASA's ASRS site as of January 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.