A CL65 return land after exhibiting an altimetry problem, thus overshooting its altitude in climb.

Attributes
ACN	403286
Time
Date	199805
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : atl
State Reference	GA
Altitude	msl bound lower : 10000 msl bound upper : 10400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : atl
Operator	common carrier : air carrier
Make Model Name	Challenger CL604
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude landing other other
Route In Use	departure other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 190 flight time total : 3600 flight time type : 170
ASRS Report	403286
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi pilot : instrument
Experience	flight time last 90 days : 260 flight time total : 18000 flight time type : 270
ASRS Report	403873
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

After departing runway 27R at atl to panama city, fl, was cleared to 10000 ft. On the taxi out to runway 27R, we had an amber caution message illuminate that stated 'EFIS comp mon.' this light indicated that both our heading and altitude information was incorrect and must be dealt with. We completed the required items on the checklist and there was nothing further. Upon climb out and near 10000 ft, the same amber 'EFIS comp mon' light illuminated. The autoplt disengaged and we climbed to 10100 ft, which was indicated on our altimeter. Departure stated that they were indicating 10400 ft. We reiterated we were at 10100 ft. I don't believe there was a traffic conflict. We were unable to rectify the amber light and we returned to atl.

Original NASA ASRS Text

Title: A CL65 RETURN LAND AFTER EXHIBITING AN ALTIMETRY PROB, THUS OVERSHOOTING ITS ALT IN CLB.

Narrative: AFTER DEPARTING RWY 27R AT ATL TO PANAMA CITY, FL, WAS CLRED TO 10000 FT. ON THE TAXI OUT TO RWY 27R, WE HAD AN AMBER CAUTION MESSAGE ILLUMINATE THAT STATED 'EFIS COMP MON.' THIS LIGHT INDICATED THAT BOTH OUR HDG AND ALT INFO WAS INCORRECT AND MUST BE DEALT WITH. WE COMPLETED THE REQUIRED ITEMS ON THE CHKLIST AND THERE WAS NOTHING FURTHER. UPON CLBOUT AND NEAR 10000 FT, THE SAME AMBER 'EFIS COMP MON' LIGHT ILLUMINATED. THE AUTOPLT DISENGAGED AND WE CLBED TO 10100 FT, WHICH WAS INDICATED ON OUR ALTIMETER. DEP STATED THAT THEY WERE INDICATING 10400 FT. WE REITERATED WE WERE AT 10100 FT. I DON'T BELIEVE THERE WAS A TFC CONFLICT. WE WERE UNABLE TO RECTIFY THE AMBER LIGHT AND WE RETURNED TO ATL.

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.