<< >> NASA ASRS Report 567523, December 2002

Flying a VNAV descent on the lga, ny, localizer runway 13 approach, B767 crew finds themselves 400 ft below the required altitude at the FAF.

Attributes
ACN	567523
Time
Date	200212
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : n90.tracon
State Reference	NY
Altitude	msl bound lower : 1100 msl bound upper : 1200
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : n90.tracon
Operator	common carrier : air carrier
Make Model Name	B767-200
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 31 other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 105 flight time total : 6200 flight time type : 2400
ASRS Report	567523
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot altitude deviation : crossing restriction not met non adherence : published procedure non adherence : far non adherence : clearance other spatial deviation
Independent Detector	atc equipment : msaw other controllerb other flight crewa
Resolutory Action	flight crew : returned to original clearance flight crew : overrode automation flight crew : became reoriented none taken : detected after the fact
Supplementary
Problem Areas	Aircraft ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

We were cleared for localizer runway 31 approach into lga approximately 10 mi at approximately 2000 ft MSL. Procedures were accomplished in accordance with the operations manual for the B767 for a VNAV descent to runway 31. VNAV was selected and 'VNAV path' was captured on the ADI with the autoplt and autothrottles engaged. The aircraft began a descent, and reduced power to follow the VNAV path horizontal bar on the ADI. At fabry FAF, the air crew noted the aircraft was at approximately 1200 ft (400 ft lower than the 1600 FAF altitude) and that the aircraft was 10 KTS slower than the selected MCP airspeed window (approximately 142 KTS). As first officer flying, I disconnected the autoplt and autothrottles and proceeded to fly the aircraft manually to the proper glide path and airspeed. Just after or as I took control of the aircraft, lga approach control gave us a low altitude alert and told us to check our barometric altimeter settings. The aircraft landed uneventfully and without further incident. Note: the B767-200 model is notorious for having a difficult time following VNAV path profiles and keeping proper airspeed on arrival profiles.

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Original NASA ASRS Text

Title: FLYING A VNAV DSCNT ON THE LGA, NY, LOC RWY 13 APCH, B767 CREW FINDS THEMSELVES 400 FT BELOW THE REQUIRED ALT AT THE FAF.

Narrative: WE WERE CLRED FOR LOC RWY 31 APCH INTO LGA APPROX 10 MI AT APPROX 2000 FT MSL. PROCS WERE ACCOMPLISHED IN ACCORDANCE WITH THE OPS MANUAL FOR THE B767 FOR A VNAV DSCNT TO RWY 31. VNAV WAS SELECTED AND 'VNAV PATH' WAS CAPTURED ON THE ADI WITH THE AUTOPLT AND AUTOTHROTTLES ENGAGED. THE ACFT BEGAN A DSCNT, AND REDUCED PWR TO FOLLOW THE VNAV PATH HORIZ BAR ON THE ADI. AT FABRY FAF, THE AIR CREW NOTED THE ACFT WAS AT APPROX 1200 FT (400 FT LOWER THAN THE 1600 FAF ALT) AND THAT THE ACFT WAS 10 KTS SLOWER THAN THE SELECTED MCP AIRSPD WINDOW (APPROX 142 KTS). AS FO FLYING, I DISCONNECTED THE AUTOPLT AND AUTOTHROTTLES AND PROCEEDED TO FLY THE ACFT MANUALLY TO THE PROPER GLIDE PATH AND AIRSPD. JUST AFTER OR AS I TOOK CTL OF THE ACFT, LGA APCH CTL GAVE US A LOW ALT ALERT AND TOLD US TO CHK OUR BAROMETRIC ALTIMETER SETTINGS. THE ACFT LANDED UNEVENTFULLY AND WITHOUT FURTHER INCIDENT. NOTE: THE B767-200 MODEL IS NOTORIOUS FOR HAVING A DIFFICULT TIME FOLLOWING VNAV PATH PROFILES AND KEEPING PROPER AIRSPD ON ARR PROFILES.

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.