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Flight crew of a MD88 overshot descent altitude due to misprogramming the autoplt altitude capture mode. They recognized their mistake and disconnected the autoplt and returned to assigned altitude.
| Attributes | |
| ACN | 354140 |
| Time | |
| Date | 199611 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : jfk |
| State Reference | NY |
| Altitude | msl bound lower : 22600 msl bound upper : 23000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zny |
| Operator | common carrier : air carrier |
| Make Model Name | MD-88 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : flight engineer pilot : commercial pilot : atp pilot : instrument pilot : private |
| Experience | flight time last 90 days : 170 flight time total : 7000 flight time type : 2000 |
| ASRS Report | 354140 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | altitude deviation : overshoot non adherence : clearance |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : became reoriented flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
During en route descent passing through FL255 with clearance to FL240, ZNY cleared us to continue descent to FL220 and to slow from 330 KIAS to 250 KIAS. Passing FL233, center revised clearance and told us to maintain FL230. I (PNF) gave the readback, then placed 230 in the autoplt altitude capture window. At the same time verbalizing to the captain to level off at FL230. During the revised clearance until now the captain was adjusting the aircraft's speed in IAS pitch mode and didn't realize we were less than 300 ft from revised leveloff, with a descent rate of approximately 1500 FPM. Since I had placed FL230 in the altitude capture window, I was expecting an immediate altitude capture by the autoplt. That did not happen because the captain was moving the IAS-vertical speed thumb wheel and we were now in vertical speed. At FL230 I again stated 'level off at FL230, stop here' and pushed the altitude hold button on the autoplt. Since the captain was still working the thumb wheel the altitude capture was lost. Passing approximately FL228 the captain realized we were descending through FL230 and disconnected the autoplt and returned the aircraft to FL230. We stopped our descent approximately 400 ft low.
Original NASA ASRS Text
Title: FLC OF A MD88 OVERSHOT DSCNT ALT DUE TO MISPROGRAMMING THE AUTOPLT ALT CAPTURE MODE. THEY RECOGNIZED THEIR MISTAKE AND DISCONNECTED THE AUTOPLT AND RETURNED TO ASSIGNED ALT.
Narrative: DURING ENRTE DSCNT PASSING THROUGH FL255 WITH CLRNC TO FL240, ZNY CLRED US TO CONTINUE DSCNT TO FL220 AND TO SLOW FROM 330 KIAS TO 250 KIAS. PASSING FL233, CTR REVISED CLRNC AND TOLD US TO MAINTAIN FL230. I (PNF) GAVE THE READBACK, THEN PLACED 230 IN THE AUTOPLT ALT CAPTURE WINDOW. AT THE SAME TIME VERBALIZING TO THE CAPT TO LEVEL OFF AT FL230. DURING THE REVISED CLRNC UNTIL NOW THE CAPT WAS ADJUSTING THE ACFT'S SPD IN IAS PITCH MODE AND DIDN'T REALIZE WE WERE LESS THAN 300 FT FROM REVISED LEVELOFF, WITH A DSCNT RATE OF APPROX 1500 FPM. SINCE I HAD PLACED FL230 IN THE ALT CAPTURE WINDOW, I WAS EXPECTING AN IMMEDIATE ALT CAPTURE BY THE AUTOPLT. THAT DID NOT HAPPEN BECAUSE THE CAPT WAS MOVING THE IAS-VERT SPD THUMB WHEEL AND WE WERE NOW IN VERT SPD. AT FL230 I AGAIN STATED 'LEVEL OFF AT FL230, STOP HERE' AND PUSHED THE ALT HOLD BUTTON ON THE AUTOPLT. SINCE THE CAPT WAS STILL WORKING THE THUMB WHEEL THE ALT CAPTURE WAS LOST. PASSING APPROX FL228 THE CAPT REALIZED WE WERE DSNDING THROUGH FL230 AND DISCONNECTED THE AUTOPLT AND RETURNED THE ACFT TO FL230. WE STOPPED OUR DSCNT APPROX 400 FT LOW.
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.