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Pilot of a fairchild merlin IIIB, SW2 descended below assigned altitude due to inadvertent autoplt disconnect resulting in ATC intervention and a change in clearance. Subsequently, the autoplt did not hold the new sector heading assignment causing ATC to quickly turn the reporter again to avoid other traffic. He finally was able to disconnect the autoplt and continue uneventfully.
| Attributes | |
| ACN | 362251 |
| Time | |
| Date | 199703 |
| Day | Mon |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : lax |
| State Reference | CA |
| Altitude | msl bound lower : 2250 msl bound upper : 2500 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : lax |
| Operator | general aviation : corporate |
| Make Model Name | Merlin III |
| Operating Under FAR Part | Part 91 |
| Flight Phase | descent : approach |
| Route In Use | approach : visual enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : single pilot |
| Qualification | other other : other pilot : atp pilot : cfi |
| Experience | flight time last 90 days : 75 flight time total : 8779 flight time type : 799 |
| ASRS Report | 362251 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Qualification | controller : radar |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other other spatial deviation |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa |
| Resolutory Action | controller : issued new clearance other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
On approach to lax (IFR in VFR conditions) I was being vectored for the visual approach for runway 25L. While level at 2500 ft approach called out traffic at 3 O'clock (not sure of distance). I believe I was on a 280 degree heading. I started scanning for traffic, just then approach asked if I had the airport in sight which I said I did not. Approach advised I could not get the visual approach unless I had either the traffic or airport in sight. I diverted my attention to the traffic, momentarily scanned my instruments and found I had descended to 2250 ft. I pitched up with autoplt trim (it was on altitude hold). A few seconds later approach said assigned altitude was 2500 ft. Approach then said since I did not see the traffic or airport turn left to 70 degrees and climb to 3500 ft. In the turn, traffic was called 11 O'clock (distance I don't remember). While looking for the traffic, climbing and turning (with autoplt) I scanned back inside to find the autoplt turning through 70 degrees and continuing to turn. I tried to turn off the autoplt with manual trim without effect. At this point approach called and asked if I had the traffic and what my heading was. I don't remember what I reported for a heading but replied negative on the traffic. Approach then ordered an immediate left turn to 180 degrees. During the turn I finally got the autoplt turned off with the autoplt circuit breaker. Callback conversation with reporter revealed the following information: reporter stated that this autoplt has been in for repairs many times, but nothing conclusive can be found wrong. It will not act in an erratic manner when tested, therefore, it is still being checked again during the upcoming 100 hour inspection. Reporter further stated that other merlin owners had not had similar problems.
Original NASA ASRS Text
Title: PLT OF A FAIRCHILD MERLIN IIIB, SW2 DSNDED BELOW ASSIGNED ALT DUE TO INADVERTENT AUTOPLT DISCONNECT RESULTING IN ATC INTERVENTION AND A CHANGE IN CLRNC. SUBSEQUENTLY, THE AUTOPLT DID NOT HOLD THE NEW SECTOR HEADING ASSIGNMENT CAUSING ATC TO QUICKLY TURN THE RPTR AGAIN TO AVOID OTHER TFC. HE FINALLY WAS ABLE TO DISCONNECT THE AUTOPLT AND CONTINUE UNEVENTFULLY.
Narrative: ON APCH TO LAX (IFR IN VFR CONDITIONS) I WAS BEING VECTORED FOR THE VISUAL APCH FOR RWY 25L. WHILE LEVEL AT 2500 FT APCH CALLED OUT TFC AT 3 O'CLOCK (NOT SURE OF DISTANCE). I BELIEVE I WAS ON A 280 DEG HDG. I STARTED SCANNING FOR TFC, JUST THEN APCH ASKED IF I HAD THE ARPT IN SIGHT WHICH I SAID I DID NOT. APCH ADVISED I COULD NOT GET THE VISUAL APCH UNLESS I HAD EITHER THE TFC OR ARPT IN SIGHT. I DIVERTED MY ATTN TO THE TFC, MOMENTARILY SCANNED MY INSTS AND FOUND I HAD DSNDED TO 2250 FT. I PITCHED UP WITH AUTOPLT TRIM (IT WAS ON ALT HOLD). A FEW SECONDS LATER APCH SAID ASSIGNED ALT WAS 2500 FT. APCH THEN SAID SINCE I DID NOT SEE THE TFC OR ARPT TURN L TO 70 DEGS AND CLB TO 3500 FT. IN THE TURN, TFC WAS CALLED 11 O'CLOCK (DISTANCE I DON'T REMEMBER). WHILE LOOKING FOR THE TFC, CLBING AND TURNING (WITH AUTOPLT) I SCANNED BACK INSIDE TO FIND THE AUTOPLT TURNING THROUGH 70 DEGS AND CONTINUING TO TURN. I TRIED TO TURN OFF THE AUTOPLT WITH MANUAL TRIM WITHOUT EFFECT. AT THIS POINT APCH CALLED AND ASKED IF I HAD THE TFC AND WHAT MY HEADING WAS. I DON'T REMEMBER WHAT I RPTED FOR A HEADING BUT REPLIED NEGATIVE ON THE TFC. APCH THEN ORDERED AN IMMEDIATE L TURN TO 180 DEGS. DURING THE TURN I FINALLY GOT THE AUTOPLT TURNED OFF WITH THE AUTOPLT CIRCUIT BREAKER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THIS AUTOPLT HAS BEEN IN FOR REPAIRS MANY TIMES, BUT NOTHING CONCLUSIVE CAN BE FOUND WRONG. IT WILL NOT ACT IN AN ERRATIC MANNER WHEN TESTED, THEREFORE, IT IS STILL BEING CHKED AGAIN DURING THE UPCOMING 100 HR INSPECTION. RPTR FURTHER STATED THAT OTHER MERLIN OWNERS HAD NOT HAD SIMILAR PROBS.
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.