<< >> NASA ASRS Report 768366, December 2007

Captain reports that transition between andes STAR and the ILS 17L approach at scel is misaligned and results in FMC 'back up.'

Attributes
ACN	768366
Time
Date	200712
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : scel.airport
State Reference	FO
Altitude	msl single value : 37000
Aircraft 1
Controlling Facilities	tracon : scel.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	arrival star : andes
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	768366
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment other aircraft equipment : fmc nav display
Resolutory Action	flight crew : overcame equipment problem
Supplementary
Problem Areas	Chart Or Publication Navigational Facility Aircraft
Primary Problem	Ambiguous

Narrative:

Scel/scl santiago; chile: commercial chart; andes 2 arrival to runway 17L lists AMB22 and CF17L as different points; but are one and the same. When coupled with ILS runway 17L route 'back-ups;' points are not a perfect overlap having slightly different coordinates. Callback conversation with reporter revealed the following information: the reporter advised that the FMC 'back up' he referred to was a lightning bolt shaped zigzag course from CF17L back to AND22 and then inbound on the ILS. The event resulted in no track deviation because the FMC was programmed to intercept the ILS course vice following the course 'track' at the point the anomaly occurred. He stated that on a subsequent flight the anomaly did not repeat itself and he feels the problem was likely resolved through an intervening software revision.

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Original NASA ASRS Text

Title: CAPTAIN REPORTS THAT TRANSITION BETWEEN ANDES STAR AND THE ILS 17L APCH AT SCEL IS MISALIGNED AND RESULTS IN FMC 'BACK UP.'

Narrative: SCEL/SCL SANTIAGO; CHILE: COMMERCIAL CHART; ANDES 2 ARR TO RWY 17L LISTS AMB22 AND CF17L AS DIFFERENT POINTS; BUT ARE ONE AND THE SAME. WHEN COUPLED WITH ILS RWY 17L RTE 'BACK-UPS;' POINTS ARE NOT A PERFECT OVERLAP HAVING SLIGHTLY DIFFERENT COORDINATES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER ADVISED THAT THE FMC 'BACK UP' HE REFERRED TO WAS A LIGHTNING BOLT SHAPED ZIGZAG COURSE FROM CF17L BACK TO AND22 AND THEN INBOUND ON THE ILS. THE EVENT RESULTED IN NO TRACK DEVIATION BECAUSE THE FMC WAS PROGRAMMED TO INTERCEPT THE ILS COURSE VICE FOLLOWING THE COURSE 'TRACK' AT THE POINT THE ANOMALY OCCURRED. HE STATED THAT ON A SUBSEQUENT FLIGHT THE ANOMALY DID NOT REPEAT ITSELF AND HE FEELS THE PROBLEM WAS LIKELY RESOLVED THROUGH AN INTERVENING SOFTWARE REVISION.

Data retrieved from NASA's ASRS site as of January 2009 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.