<< >> NASA ASRS Report 292522, December 1994

Fmp locked up. Autoplt, autothrottle would not respond to inputs for altitude select, level change, speed select, heading select, and vertical speed.

Attributes
ACN	292522
Time
Date	199412
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : atl
State Reference	GA
Altitude	msl bound lower : 8000 msl bound upper : 8000
Aircraft 1
Controlling Facilities	tracon : atl
Operator	common carrier : air carrier
Make Model Name	Fokker 100
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	292522
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other other : unspecified cockpit
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Arriving atl level at 8000 ft and 180 KTS with autoplt and autothrottle engaged the fmp locked up and would not respond to any inputs including atl select, level change, speed select, heading select, and vertical speed. The flight director switches were cycled with no change. The autoplt was disconnected as we had been given a descent clearance. The fmp still did not respond. The flight director switches were once again cycled and the fmp came back to life. I wrote this up in the E-6. Within a day I encountered 2 other F100 capts who had the same problem on other F100's. They confirmed the only fix is to disengage the autoplt and cycle the flight director switches. I have not yet found a reference to this problem in the aircraft manuals. If it is that common of a problem it needs to be addressed.

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Original NASA ASRS Text

Title: FMP LOCKED UP. AUTOPLT, AUTOTHROTTLE WOULD NOT RESPOND TO INPUTS FOR ALT SELECT, LEVEL CHANGE, SPD SELECT, HDG SELECT, AND VERT SPD.

Narrative: ARRIVING ATL LEVEL AT 8000 FT AND 180 KTS WITH AUTOPLT AND AUTOTHROTTLE ENGAGED THE FMP LOCKED UP AND WOULD NOT RESPOND TO ANY INPUTS INCLUDING ATL SELECT, LEVEL CHANGE, SPD SELECT, HDG SELECT, AND VERT SPD. THE FLT DIRECTOR SWITCHES WERE CYCLED WITH NO CHANGE. THE AUTOPLT WAS DISCONNECTED AS WE HAD BEEN GIVEN A DSCNT CLRNC. THE FMP STILL DID NOT RESPOND. THE FLT DIRECTOR SWITCHES WERE ONCE AGAIN CYCLED AND THE FMP CAME BACK TO LIFE. I WROTE THIS UP IN THE E-6. WITHIN A DAY I ENCOUNTERED 2 OTHER F100 CAPTS WHO HAD THE SAME PROB ON OTHER F100'S. THEY CONFIRMED THE ONLY FIX IS TO DISENGAGE THE AUTOPLT AND CYCLE THE FLT DIRECTOR SWITCHES. I HAVE NOT YET FOUND A REF TO THIS PROB IN THE ACFT MANUALS. IF IT IS THAT COMMON OF A PROB IT NEEDS TO BE ADDRESSED.

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.