|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||0601 To 1200|
|Locale Reference||airport : bur|
|Altitude||msl bound lower : 3500|
msl bound upper : 3500
|Controlling Facilities||tracon : bur|
|Operator||general aviation : personal|
|Make Model Name||Small Transport, Low Wing, 2 Recip Eng|
|Flight Phase||descent : approach|
|Function||flight crew : single pilot|
|Qualification||pilot : commercial|
pilot : instrument
|Experience||flight time last 90 days : 40|
flight time total : 1500
|Affiliation||government : faa|
|Function||controller : approach|
|Qualification||controller : radar|
|Anomaly||altitude deviation : excursion from assigned altitude|
|Independent Detector||other flight crewa|
|Air Traffic Incident||other|
I was outside the OM at 3500', was cleared for the runway 7 ILS approach and asked to maintain 160 KTS and 3500' to OM. Aircraft was being flown by autoplt. I selected 'navigation' on autoplt head to intercept localizer and 'altitude' altitude hold was on already. However aircraft started rapid descent. I retrimmed the autoplt to regain altitude, autoplt went into very steep climb, aircraft lost speed to 120 KTS. I disconnected the autoplt at this point, the aircraft was totally out of trim. I manually retrimmed the aircraft as soon as possible and manually flew the approach. Bur approach became very upset about the speed deviation and asked if I could maintain 120 KTS. I explained that my autoplt system had in a split second almost put the aircraft into an unusual altitude and that speed and altitude was lost during recovery.
Original NASA ASRS Text
Title: ASSIGNED TO MAINTAIN 160 IAS TO OUTER MARKER. AUTOPLT MALFUNCTION CAUSES RAPID CLIMB AND SPEED DECREASE TO 120 IAS.
Narrative: I WAS OUTSIDE THE OM AT 3500', WAS CLRED FOR THE RWY 7 ILS APCH AND ASKED TO MAINTAIN 160 KTS AND 3500' TO OM. ACFT WAS BEING FLOWN BY AUTOPLT. I SELECTED 'NAV' ON AUTOPLT HEAD TO INTERCEPT LOC AND 'ALT' ALT HOLD WAS ON ALREADY. HOWEVER ACFT STARTED RAPID DSCNT. I RETRIMMED THE AUTOPLT TO REGAIN ALT, AUTOPLT WENT INTO VERY STEEP CLB, ACFT LOST SPD TO 120 KTS. I DISCONNECTED THE AUTOPLT AT THIS POINT, THE ACFT WAS TOTALLY OUT OF TRIM. I MANUALLY RETRIMMED THE ACFT ASAP AND MANUALLY FLEW THE APCH. BUR APCH BECAME VERY UPSET ABOUT THE SPD DEV AND ASKED IF I COULD MAINTAIN 120 KTS. I EXPLAINED THAT MY AUTOPLT SYS HAD IN A SPLIT SEC ALMOST PUT THE ACFT INTO AN UNUSUAL ALT AND THAT SPD AND ALT WAS LOST DURING RECOVERY.
Data retrieved from NASA's ASRS site as of August 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.