N790DM

ATA 8520

WHEN REMOVING RT ENGINE NR 4 CYLINDER DUE TO A CRACK, NR 4 PISTON SKIRT FOUND BROKE OFF AT THE 4TH RING LAND. ENGINE THEN REMOVED FROM ACFT FOR TEAR-DOWN INSPECTION. I HAVE FOUND BROKEN PISTON SKIRTS ON THIS PARTICULAR ACFT ON 3 DIFFERENT ENGINES.

ATA 7120

LEFT AND RIGHT ENGINE, BOTH FRONT MOUNT UPPER HALVES COMPRESSED EXCESSIVELY. THE LT FRONT MOUNT ON THE LT AND RT ENGINE WERE EXPOSING .2500" OF INNER BARREL. SUBSEQUENTLY, THE LT ENGINE NR 6 CYLINDER HEADER TUBE RUBBED THE ENGINE BEAM EXTENSION. IT HAS NOT BEEN UNCOMMON TO FIND THIS CONDITION ON THE LT FRONT MOUNT AFTER 100 HOURS TIS.

ATA 8530

THE LT ENGINE WAS EXHIBITING LOW OIL PRESSURE. THE OIL FILTER WAS PULLED, CUT OPEN, AND INSPECTED. A SIGNIFICANT AMOUNT OF METAL WAS FOUND. THE ENGINE WAS THEN TORN DOWN FOR FURTHER INSPECTION. CHUNKS OF PISTON SKIRTING WAS FOUND IN THE OIL PAN, NR 2 PISTON HAD COME APART AT THE SKIRTING AROUND THE BOTTOM RING-LAND BELOW THE PISTON PIN, AND THE NR 1 PISTON WAS FOUND THE BE CRACKED IN THE SAME AREA THAT THE NR 2 PISTON WAS BROKEN. NR 2 PISTON TAKEN FOR METALLURGICAL TESTING. A POSSIBLE CONTRIBUTING FACTOR MAY HAVE BEEN THE START OF THE ENGINE AT A TEMPERATURE NEAR 0 DEGREES (F). (K)

ATA 5280

COTTER PIN CAME OUT OF CLEVIS PIN ITEM NR 5 OR CLEVIS PIN FAILED ATTACHING NOSE GEAR DOOR PUSH PULL TUBE TO THE EYE BOLT ON THE LT NOSE GEAR DOOR. ON TAKE OFF THE LT GEAR DOOR BLEW SHUT. WHEN GEAR WAS RETRACTED THE NOSE GEAR JAMMED HALF WAY UP, BREAKING BELLCRANK UNDER PILOTS FEET. NOSE GEAR WOULD NOT COME DOWN. NUMEROUS HIGH G MANEUVERS WERE PERFORMED IN AN ATTEMPT TO GET GEAR TO DROP, WOULD NOT. AIRCRAFT WAS LANDED ON THE MAINS, ENGINES WERE FEATHERED AN AIRCRAFT CAME TO STOP ON NOSE AFTER SLIDING NOSE APP 200 FT. NOSE WAS LIFTED, NOSE WHEEL WAS EXTENDED AND LOCKED AND AIRCRAFT WAS PULLED TO HANGER. (K)