Alleged altitude deviation in ZME airspace.

Attributes
ACN	468563
Time
Date	200003
Day	Thu
Local Time Of Day	0601 To 1200
Place
State Reference	KY
Altitude	msl bound lower : 28500 msl bound upper : 28000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme.artcc
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : enroute altitude change cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument
Experience	flight time last 90 days : 60 flight time total : 14000 flight time type : 1500
ASRS Report	468563
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine pilot : cfi
Experience	flight time last 90 days : 60 flight time total : 1600 flight time type : 50
ASRS Report	468570
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot other anomaly other
Independent Detector	other controllera other flight crewa other flight crewb
Resolutory Action	other
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Aircraft ATC Facility ATC Human Performance
Primary Problem	Aircraft

Narrative:

Had been in cruise at FL330, descended as cleared to FL290, level there for approximately 10 mins. Center asked us to verify altitude, which we did. Asked us to check altimeter settings, which were at 29.92. We had an overhauled air data computer installed 2 flts earlier. I suspected a problem with the air data computer and asked the controller about his questions concerning altitude. He stated his equipment showed us 500 ft low. We have watched and have had ATC monitor our altitude mode C and have shown absolutely no more problems. Suspect center's equipment. The controller may have been busy, but a better explanation on his part would have helped us troubleshoot -- if indeed we had an equipment problem.

Original NASA ASRS Text

Title: ALLEGED ALTDEV IN ZME AIRSPACE.

Narrative: HAD BEEN IN CRUISE AT FL330, DSNDED AS CLRED TO FL290, LEVEL THERE FOR APPROX 10 MINS. CTR ASKED US TO VERIFY ALT, WHICH WE DID. ASKED US TO CHK ALTIMETER SETTINGS, WHICH WERE AT 29.92. WE HAD AN OVERHAULED AIR DATA COMPUTER INSTALLED 2 FLTS EARLIER. I SUSPECTED A PROB WITH THE AIR DATA COMPUTER AND ASKED THE CTLR ABOUT HIS QUESTIONS CONCERNING ALT. HE STATED HIS EQUIP SHOWED US 500 FT LOW. WE HAVE WATCHED AND HAVE HAD ATC MONITOR OUR ALT MODE C AND HAVE SHOWN ABSOLUTELY NO MORE PROBS. SUSPECT CTR'S EQUIP. THE CTLR MAY HAVE BEEN BUSY, BUT A BETTER EXPLANATION ON HIS PART WOULD HAVE HELPED US TROUBLESHOOT -- IF INDEED WE HAD AN EQUIP PROB.

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.