G450 flight crew reports anomalous captain pfd indicating airspeed increase with pitch up which the ...

Attributes
ACN	779973
Time
Date	200803
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zzz.artcc
State Reference	US
Altitude	msl single value : 40000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	general aviation : corporate
Make Model Name	Gulfstream IV
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 75 flight time total : 10100 flight time type : 200
ASRS Report	779973
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude
Independent Detector	other flight crewa
Resolutory Action	flight crew : diverted to another airport flight crew : overcame equipment problem
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

I was flying as sic on a part 91 trip from our home base in a gulfstream 450 with no passenger on board. While at cruise in level flight at FL400; the l-hand primary flight display suddenly showed a climb. Concurrently it also indicated a speed increase. We noticed the secondary flight display showed level flight and also the third attitude indicator showed level flight. Briefly the autoplt tried to follow the primary flight display and tried to descend to the altitude selector set altitude. At approximately FL399; the autoplt was manually disconnected. We reported to cleveland ATC 'unable rvsm due to equipment failure.' we climbed 100 ft to FL400 and as per the checklist; deselected the faulty air data computer which was feeding faulty information to the primary flight display. Also; as per the checklist; we selected a third air data source to the primary flight display and told ATC we were once again able to resume rvsm. Since ATC received information from the faulty primary flight display; ATC thought we were at a higher altitude than FL400. We diverted to a gulfstream service center. It was determined to be a faulty angle of attack probe on the primary flight side of the aircraft.

Original NASA ASRS Text

Title: G450 FLT CREW REPORTS ANOMALOUS CAPT PFD INDICATING AIRSPEED INCREASE WITH PITCH UP WHICH THE AUTOPILOT ATTEMPTS TO CORRECT BY PITCHING DOWN. ACFT IS MANUALLY RETURNED TO LEVEL FLIGHT.

Narrative: I WAS FLYING AS SIC ON A PART 91 TRIP FROM OUR HOME BASE IN A GULFSTREAM 450 WITH NO PAX ON BOARD. WHILE AT CRUISE IN LEVEL FLT AT FL400; THE L-HAND PRIMARY FLT DISPLAY SUDDENLY SHOWED A CLB. CONCURRENTLY IT ALSO INDICATED A SPD INCREASE. WE NOTICED THE SECONDARY FLT DISPLAY SHOWED LEVEL FLT AND ALSO THE THIRD ATTITUDE INDICATOR SHOWED LEVEL FLT. BRIEFLY THE AUTOPLT TRIED TO FOLLOW THE PRIMARY FLT DISPLAY AND TRIED TO DSND TO THE ALT SELECTOR SET ALT. AT APPROX FL399; THE AUTOPLT WAS MANUALLY DISCONNECTED. WE RPTED TO CLEVELAND ATC 'UNABLE RVSM DUE TO EQUIP FAILURE.' WE CLBED 100 FT TO FL400 AND AS PER THE CHKLIST; DESELECTED THE FAULTY ADC WHICH WAS FEEDING FAULTY INFO TO THE PRIMARY FLT DISPLAY. ALSO; AS PER THE CHKLIST; WE SELECTED A THIRD AIR DATA SOURCE TO THE PRIMARY FLT DISPLAY AND TOLD ATC WE WERE ONCE AGAIN ABLE TO RESUME RVSM. SINCE ATC RECEIVED INFO FROM THE FAULTY PRIMARY FLT DISPLAY; ATC THOUGHT WE WERE AT A HIGHER ALT THAN FL400. WE DIVERTED TO A GULFSTREAM SVC CTR. IT WAS DETERMINED TO BE A FAULTY ANGLE OF ATTACK PROBE ON THE PRIMARY FLT SIDE OF THE ACFT.

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

G450 flight crew reports anomalous captain pfd indicating airspeed increase with pitch up which the autopilot attempts to correct by pitching down. Aircraft is manually returned to level flight.