Air carrier medium large transport aircraft navigation computer system failed causing flight crew to...

Attributes
ACN	218120
Time
Date	199208
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mxe
State Reference	PA
Altitude	msl bound lower : 35000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Controlling Facilities	artcc : zny
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 8000 flight time type : 1000
ASRS Report	218120
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

During cruise flight in medium large transport aircraft #2 platform and ahrs failed as indicated by a loss of attitude and navigation displays on first officer's side. This was verified by FMS maintenance status readout (ahrs 1 and platform 1 failed). A few mins later, the autoplt disconnected and flight director information was lost and autothrottles disconnected. Maintenance status display indicated platform #2 failed. By selecting EFIS to both on, both captain and first officer maintained attitude and navigation displays. Fortunately, destination WX was good, otherwise this could have been a real problem. This event demonstrates that dual failures still occur and demonstrates the need for proficiency in raw data navigation which is often lost in crews flying glass cockpit aircraft. This event would have limited us to a basic jet mins raw data hand flown approach. Had we been destined for an area of wide WX with marginal fuel this could be a real emergency. (Mins would be 4000 and 3/4).

Original NASA ASRS Text

Title: ACR MLG ACFT NAV COMPUTER SYS FAILED CAUSING FLC TO RELY ON 'RAW DATA.'

Narrative: DURING CRUISE FLT IN MLG ACFT #2 PLATFORM AND AHRS FAILED AS INDICATED BY A LOSS OF ATTITUDE AND NAV DISPLAYS ON FO'S SIDE. THIS WAS VERIFIED BY FMS MAINT STATUS READOUT (AHRS 1 AND PLATFORM 1 FAILED). A FEW MINS LATER, THE AUTOPLT DISCONNECTED AND FLT DIRECTOR INFO WAS LOST AND AUTOTHROTTLES DISCONNECTED. MAINT STATUS DISPLAY INDICATED PLATFORM #2 FAILED. BY SELECTING EFIS TO BOTH ON, BOTH CAPT AND FO MAINTAINED ATTITUDE AND NAV DISPLAYS. FORTUNATELY, DEST WX WAS GOOD, OTHERWISE THIS COULD HAVE BEEN A REAL PROBLEM. THIS EVENT DEMONSTRATES THAT DUAL FAILURES STILL OCCUR AND DEMONSTRATES THE NEED FOR PROFICIENCY IN RAW DATA NAV WHICH IS OFTEN LOST IN CREWS FLYING GLASS COCKPIT ACFT. THIS EVENT WOULD HAVE LIMITED US TO A BASIC JET MINS RAW DATA HAND FLOWN APCH. HAD WE BEEN DESTINED FOR AN AREA OF WIDE WX WITH MARGINAL FUEL THIS COULD BE A REAL EMER. (MINS WOULD BE 4000 AND 3/4).

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.

Air carrier medium large transport aircraft navigation computer system failed causing flight crew to rely on 'raw data.'