<< >> NASA ASRS Report 211418, May 1992

Flight crew of medium large transport aircraft made a map after the aircraft navigation computers did not provide the correct distant information.

Attributes
ACN	211418
Time
Date	199205
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : clt
State Reference	NC
Altitude	msl bound lower : 2700 msl bound upper : 2700
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : clt
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 240 flight time total : 7000 flight time type : 2500
ASRS Report	211418
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Turned onto localizer backcourse approach using company procedures with both pilots tuned to localizer. FMC showed us approximately 16 mi out from runway and established on localizer. FMC distance data incorrect due to bypass inserted in route automatically. Flew down localizer and did not descend at final approach fix because FMC said we had not reached it yet. Missed approached over runway. This approach is not possible to fly using company procedures because a third navigation radio is required for DME data off clt VOR. FMC data is unreliable due to automatic insertion of bypass when passing the clt airport on downwind.

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Original NASA ASRS Text

Title: FLC OF MLG ACFT MADE A MAP AFTER THE ACFT NAV COMPUTERS DID NOT PROVIDE THE CORRECT DISTANT INFO.

Narrative: TURNED ONTO LOC BACKCOURSE APCH USING COMPANY PROCS WITH BOTH PLTS TUNED TO LOC. FMC SHOWED US APPROX 16 MI OUT FROM RWY AND ESTABLISHED ON LOC. FMC DISTANCE DATA INCORRECT DUE TO BYPASS INSERTED IN RTE AUTOMATICALLY. FLEW DOWN LOC AND DID NOT DSND AT FINAL APCH FIX BECAUSE FMC SAID WE HAD NOT REACHED IT YET. MISSED APCHED OVER RWY. THIS APCH IS NOT POSSIBLE TO FLY USING COMPANY PROCS BECAUSE A THIRD NAV RADIO IS REQUIRED FOR DME DATA OFF CLT VOR. FMC DATA IS UNRELIABLE DUE TO AUTOMATIC INSERTION OF BYPASS WHEN PASSING THE CLT ARPT ON DOWNWIND.

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.