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Pilot of small aircraft sel aircraft failed to maintain a 'lean engine fuel mixture' during descent into a high altitude airport resulting in a rough running engine and declaring an emergency. Non tower airport.
| Attributes | |
| ACN | 232324 |
| Time | |
| Date | 199301 |
| Day | Sat |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : l58 |
| State Reference | CA |
| Altitude | msl bound lower : 8500 msl bound upper : 8500 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | general aviation : personal |
| Make Model Name | Small Aircraft, Low Wing, 1 Eng, Retractable Gear |
| Flight Phase | descent : approach landing other other |
| Route In Use | approach : visual |
| Flight Plan | VFR |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : single pilot |
| Qualification | pilot : private |
| Experience | flight time last 90 days : 5 flight time total : 250 flight time type : 31 |
| ASRS Report | 232324 |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : declared emergency flight crew : overcame equipment problem |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | other |
Narrative:
Flight from march AFB in aeronautical club aircraft to big bear airport (L58) approximately 30 NM away. Big bear airport is at 6750 ft. March AFB (riv) 1538 ft. Big bear is situated in mountainous area with tops of mountains from 8400 to 11500 ft. Climbed aircraft to 10500 ft to overfly tops. During descent to enter traffic pattern called for landing advisory on unicom and was told right traffic for runway 7. While descending to enter on 45 an small transport called base for runway 7. I observed this small transport on base for runway 25 and called a warning on the runway direction. Small transport responded that they were going around. The small transport then flew down the runway centerline, did a 180 degree turn approximately 1 1/2 mi past the threshold of runway 7, and then made straight-in approach. As small transport was on 1/4 mi final, I was on downwind just about to turn base. At that time my engine backfired and began to run very rough. I switched tanks, fuel pump on and then made a radio call declaring an emergency and asking the small transport to go around. He complied. While turning final during my before landing check I recognized I had the mixture full forward. When I pulled it back the engine smoothed out. I believe my preoccupation with keeping an eye out for the small transport and other traffic resulted in my automatic entering the pattern procedure, i.e., mixture full rich, propeller full forward, lower gear, 10 degrees flaps. I was so preoccupied I forgot to leave the mixture lean for the density altitude. Although I landed successfully it was a very tense (real scary) time.
Original NASA ASRS Text
Title: PLT OF SMA SEL ACFT FAILED TO MAINTAIN A 'LEAN ENG FUEL MIXTURE' DURING DSCNT INTO A HIGH ALT ARPT RESULTING IN A ROUGH RUNNING ENG AND DECLARING AN EMER. NON TWR ARPT.
Narrative: FLT FROM MARCH AFB IN AERO CLUB ACFT TO BIG BEAR ARPT (L58) APPROX 30 NM AWAY. BIG BEAR ARPT IS AT 6750 FT. MARCH AFB (RIV) 1538 FT. BIG BEAR IS SITUATED IN MOUNTAINOUS AREA WITH TOPS OF MOUNTAINS FROM 8400 TO 11500 FT. CLBED ACFT TO 10500 FT TO OVERFLY TOPS. DURING DSCNT TO ENTER TFC PATTERN CALLED FOR LNDG ADVISORY ON UNICOM AND WAS TOLD R TFC FOR RWY 7. WHILE DSNDING TO ENTER ON 45 AN SMT CALLED BASE FOR RWY 7. I OBSERVED THIS SMT ON BASE FOR RWY 25 AND CALLED A WARNING ON THE RWY DIRECTION. SMT RESPONDED THAT THEY WERE GOING AROUND. THE SMT THEN FLEW DOWN THE RWY CTRLINE, DID A 180 DEG TURN APPROX 1 1/2 MI PAST THE THRESHOLD OF RWY 7, AND THEN MADE STRAIGHT-IN APCH. AS SMT WAS ON 1/4 MI FINAL, I WAS ON DOWNWIND JUST ABOUT TO TURN BASE. AT THAT TIME MY ENG BACKFIRED AND BEGAN TO RUN VERY ROUGH. I SWITCHED TANKS, FUEL PUMP ON AND THEN MADE A RADIO CALL DECLARING AN EMER AND ASKING THE SMT TO GAR. HE COMPLIED. WHILE TURNING FINAL DURING MY BEFORE LNDG CHK I RECOGNIZED I HAD THE MIXTURE FULL FORWARD. WHEN I PULLED IT BACK THE ENG SMOOTHED OUT. I BELIEVE MY PREOCCUPATION WITH KEEPING AN EYE OUT FOR THE SMT AND OTHER TFC RESULTED IN MY AUTOMATIC ENTERING THE PATTERN PROC, I.E., MIXTURE FULL RICH, PROP FULL FORWARD, LOWER GEAR, 10 DEGS FLAPS. I WAS SO PREOCCUPIED I FORGOT TO LEAVE THE MIXTURE LEAN FOR THE DENSITY ALT. ALTHOUGH I LANDED SUCCESSFULLY IT WAS A VERY TENSE (REAL SCARY) TIME.
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.