 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Altitude deviation altitude undershot. Altitude crossing restriction not met. Non adherence to ATC clearance instruction.
| Attributes | |
| ACN | 238399 |
| Time | |
| Date | 199303 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : gnv |
| State Reference | FL |
| Altitude | msl bound lower : 27000 msl bound upper : 27600 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zjx artcc : zdc |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : instrument pilot : cfi pilot : atp pilot : flight engineer |
| Experience | flight time last 90 days : 150 flight time total : 16000 flight time type : 2000 |
| ASRS Report | 238399 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 6000 flight time type : 1000 |
| ASRS Report | 237589 |
| Events | |
| Anomaly | altitude deviation : undershoot altitude deviation : crossing restriction not met non adherence : clearance |
| Independent Detector | other flight crewa |
| Resolutory Action | none taken : insufficient time |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Given a descent to cross gnv at FL270. First officer flying, I (captain, PNF) entered FL270 in FMC for gnv. I knew we should start down but, wanting to let the first officer fly his own descent, I allowed him to stay in VNAV. I felt we could still get down by using speed brake if needed. FMC computed top of descent and said drag required. First officer extended the speed brake and all was going fine until we captured the altitude (which happened earlier than normal due to our higher than normal descent rate). Once 'altitude capture' has occurred VNAV makes a level off without regard to the crossing altitude restriction. As a result, we crossed gnv at 27600 ft. If aircraft had been hand flown aggressively from start of descent we could have made the restriction. Glass, moving map, FMC, VNAV, and autoplt are nice tools but we as pilots must know where we are and where we are going. We must not rely on our tools to do the job, especially when descent restrictions are given late.
Original NASA ASRS Text
Title: ALTDEV ALT UNDERSHOT. ALT XING RESTRICTION NOT MET. NON ADHERENCE TO ATC CLRNC INSTRUCTION.
Narrative: GIVEN A DSCNT TO CROSS GNV AT FL270. FO FLYING, I (CAPT, PNF) ENTERED FL270 IN FMC FOR GNV. I KNEW WE SHOULD START DOWN BUT, WANTING TO LET THE FO FLY HIS OWN DSCNT, I ALLOWED HIM TO STAY IN VNAV. I FELT WE COULD STILL GET DOWN BY USING SPD BRAKE IF NEEDED. FMC COMPUTED TOP OF DSCNT AND SAID DRAG REQUIRED. FO EXTENDED THE SPD BRAKE AND ALL WAS GOING FINE UNTIL WE CAPTURED THE ALT (WHICH HAPPENED EARLIER THAN NORMAL DUE TO OUR HIGHER THAN NORMAL DSCNT RATE). ONCE 'ALT CAPTURE' HAS OCCURRED VNAV MAKES A LEVEL OFF WITHOUT REGARD TO THE XING ALT RESTRICTION. AS A RESULT, WE CROSSED GNV AT 27600 FT. IF ACFT HAD BEEN HAND FLOWN AGGRESSIVELY FROM START OF DSCNT WE COULD HAVE MADE THE RESTRICTION. GLASS, MOVING MAP, FMC, VNAV, AND AUTOPLT ARE NICE TOOLS BUT WE AS PLTS MUST KNOW WHERE WE ARE AND WHERE WE ARE GOING. WE MUST NOT RELY ON OUR TOOLS TO DO THE JOB, ESPECIALLY WHEN DSCNT RESTRICTIONS ARE GIVEN LATE.
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.