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Lear 25 autoplt disconnects during approach at 8000 ft. There was no 'chime' warning of that disconnect. Reporter says it is 'an ongoing problem' on the LR20 series he has flown.
| Attributes | |
| ACN | 381364 |
| Time | |
| Date | 199709 |
| Day | Tue |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : apa |
| State Reference | CO |
| Altitude | msl bound lower : 8000 msl bound upper : 8500 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : apa |
| Operator | common carrier : air taxi |
| Make Model Name | Learjet 25 |
| Operating Under FAR Part | Part 135 |
| Flight Phase | descent : approach |
| Route In Use | approach : straight in arrival other enroute other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air taxi |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : instrument |
| Experience | flight time last 90 days : 70 flight time total : 3100 flight time type : 1100 |
| ASRS Report | 381364 |
| Person 2 | |
| Affiliation | company : air taxi |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : regained aircraft control flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation other |
Narrative:
First officer was flying an ILS to apa. We were level at 8000 ft inbound to casse with the autoplt engaged. The autoplt then disconnected without a disconnect tone. The aircraft pitched up briskly and at about 8500 ft we were able to descend back to 8000 ft. The disconnect and abruptness seemed to be indicative of an inadvertent stick puller. Our speed was approximately 170 KIAS. During the preceding several flts the puller had activated at altitude at speeds of .72 to .80 mach (this should not occur until greater than .82 mach). This seems to be an ongoing problem with all 20 series learjets that I have flown (about 10 different aircraft). No mention was made to us by the tower of our altitude but other aircraft would have been on approach frequency. In my time flying lears I have experienced probably nearly 100 climbs, dscnts, or rolls up to 45 degrees that were uncommanded. A great many of these have occurred without a disconnect chime.
Original NASA ASRS Text
Title: LEAR 25 AUTOPLT DISCONNECTS DURING APCH AT 8000 FT. THERE WAS NO 'CHIME' WARNING OF THAT DISCONNECT. RPTR SAYS IT IS 'AN ONGOING PROB' ON THE LR20 SERIES HE HAS FLOWN.
Narrative: FO WAS FLYING AN ILS TO APA. WE WERE LEVEL AT 8000 FT INBOUND TO CASSE WITH THE AUTOPLT ENGAGED. THE AUTOPLT THEN DISCONNECTED WITHOUT A DISCONNECT TONE. THE ACFT PITCHED UP BRISKLY AND AT ABOUT 8500 FT WE WERE ABLE TO DSND BACK TO 8000 FT. THE DISCONNECT AND ABRUPTNESS SEEMED TO BE INDICATIVE OF AN INADVERTENT STICK PULLER. OUR SPD WAS APPROX 170 KIAS. DURING THE PRECEDING SEVERAL FLTS THE PULLER HAD ACTIVATED AT ALT AT SPDS OF .72 TO .80 MACH (THIS SHOULD NOT OCCUR UNTIL GREATER THAN .82 MACH). THIS SEEMS TO BE AN ONGOING PROB WITH ALL 20 SERIES LEARJETS THAT I HAVE FLOWN (ABOUT 10 DIFFERENT ACFT). NO MENTION WAS MADE TO US BY THE TWR OF OUR ALT BUT OTHER ACFT WOULD HAVE BEEN ON APCH FREQ. IN MY TIME FLYING LEARS I HAVE EXPERIENCED PROBABLY NEARLY 100 CLBS, DSCNTS, OR ROLLS UP TO 45 DEGS THAT WERE UNCOMMANDED. A GREAT MANY OF THESE HAVE OCCURRED WITHOUT A DISCONNECT CHIME.
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.