Narrative:

The 'a' axis cap came off the auxiliary gearbox in-flight resulting in engine seizure (right after takeoff). 2 days prior I participated in an 'east' check of the r-hand engine. One of the task cards was to check the first stage compressor blades and the only way to do that is to remove the cap from the 'a' axis of the auxiliary gearbox, and to turn the shaft of the gearbox to see all of the blades. What may have happened is the cap may not have been installed properly. All that holds it in place is a snap ring. Or another possibility earlier today the plane was down for a bird strike and the strike was on the r-side of the radome. This happened in xyz, us. The mechanic that signed off the bird strike inspection said he inspected the r-hand engine. It's possible he removed the auxiliary gearbox axis 'a' cap to turn the first stage compressor blades (first stage) and incorrectly installed the cover. The point I am making is that the plane made 13 flts since the 'east' check with no incident. Then after the bird strike inspection comes the in-flight failure, resulting in an engine change. I think they should design a better way to install the axis cap on the auxiliary gearbox, possibly bolts or screws instead of a snap ring. And I believe it is a mistake to have an outstation mechanic perform this task. The mechanic isn't trained in bird strike inspections or in the ge-CT7. So he really didn't know what he was doing. And the 'east' check card for first stage compressors is vague. It tells you to look at them but it doesn't tell you how. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was a saab 340B pwred with ge-CT7 engines. The reporter said he removed the 'a' axis cap on the auxiliary gearbox so the first stage compressor could be inspected. The reporter said the cap and 'O' ring seal is secured with a snap ring. The reporter stated the maintenance manual makes note of the requirement to remove the cap to turn the compressor and turbine, but makes no mention of reinstalling the cap, 'O' ring and snap ring or inspection after close up. The reporter said he is certain the cap was installed and secured at the end of the compressor inspection. The reporter said 8 flight hours and 13 flts after the inspection, a first stage inspection was again required for a bird strike at an off line station by a contract FBO mechanic. The reporter stated the FBO mechanic was given verbal instructions by a maintenance controller on the phone on how to remove the cap to turn the compressor for blade inspection. The reporter said the first flight after the off line inspection the engine seized on takeoff due to loss of oil. The reporter stated the cap, 'O' ring seal and snap ring is subjected to 50 psi of oil pressure. The reporter stated the inspection of the failed engine revealed the cap was the cause of the oil loss and suspected the snap ring was installed incorrectly. The reporter stated the maintenance manual was updated immediately to change procedures and inspection to avoid this type of incident.

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Original NASA ASRS Text

Title: A SAAB 340B ON TKOF HAD #2 ENG SEIZE DUE TO LOSS OF OIL FROM AN IMPROPERLY INSTALLED AUX GEARBOX CAP.

Narrative: THE 'A' AXIS CAP CAME OFF THE AUX GEARBOX INFLT RESULTING IN ENG SEIZURE (RIGHT AFTER TKOF). 2 DAYS PRIOR I PARTICIPATED IN AN 'E' CHK OF THE R-HAND ENG. ONE OF THE TASK CARDS WAS TO CHK THE FIRST STAGE COMPRESSOR BLADES AND THE ONLY WAY TO DO THAT IS TO REMOVE THE CAP FROM THE 'A' AXIS OF THE AUX GEARBOX, AND TO TURN THE SHAFT OF THE GEARBOX TO SEE ALL OF THE BLADES. WHAT MAY HAVE HAPPENED IS THE CAP MAY NOT HAVE BEEN INSTALLED PROPERLY. ALL THAT HOLDS IT IN PLACE IS A SNAP RING. OR ANOTHER POSSIBILITY EARLIER TODAY THE PLANE WAS DOWN FOR A BIRD STRIKE AND THE STRIKE WAS ON THE R-SIDE OF THE RADOME. THIS HAPPENED IN XYZ, US. THE MECH THAT SIGNED OFF THE BIRD STRIKE INSPECTION SAID HE INSPECTED THE R-HAND ENG. IT'S POSSIBLE HE REMOVED THE AUX GEARBOX AXIS 'A' CAP TO TURN THE FIRST STAGE COMPRESSOR BLADES (FIRST STAGE) AND INCORRECTLY INSTALLED THE COVER. THE POINT I AM MAKING IS THAT THE PLANE MADE 13 FLTS SINCE THE 'E' CHK WITH NO INCIDENT. THEN AFTER THE BIRD STRIKE INSPECTION COMES THE INFLT FAILURE, RESULTING IN AN ENG CHANGE. I THINK THEY SHOULD DESIGN A BETTER WAY TO INSTALL THE AXIS CAP ON THE AUX GEARBOX, POSSIBLY BOLTS OR SCREWS INSTEAD OF A SNAP RING. AND I BELIEVE IT IS A MISTAKE TO HAVE AN OUTSTATION MECH PERFORM THIS TASK. THE MECH ISN'T TRAINED IN BIRD STRIKE INSPECTIONS OR IN THE GE-CT7. SO HE REALLY DIDN'T KNOW WHAT HE WAS DOING. AND THE 'E' CHK CARD FOR FIRST STAGE COMPRESSORS IS VAGUE. IT TELLS YOU TO LOOK AT THEM BUT IT DOESN'T TELL YOU HOW. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A SAAB 340B PWRED WITH GE-CT7 ENGS. THE RPTR SAID HE REMOVED THE 'A' AXIS CAP ON THE AUX GEARBOX SO THE FIRST STAGE COMPRESSOR COULD BE INSPECTED. THE RPTR SAID THE CAP AND 'O' RING SEAL IS SECURED WITH A SNAP RING. THE RPTR STATED THE MAINT MANUAL MAKES NOTE OF THE REQUIREMENT TO REMOVE THE CAP TO TURN THE COMPRESSOR AND TURBINE, BUT MAKES NO MENTION OF REINSTALLING THE CAP, 'O' RING AND SNAP RING OR INSPECTION AFTER CLOSE UP. THE RPTR SAID HE IS CERTAIN THE CAP WAS INSTALLED AND SECURED AT THE END OF THE COMPRESSOR INSPECTION. THE RPTR SAID 8 FLT HRS AND 13 FLTS AFTER THE INSPECTION, A FIRST STAGE INSPECTION WAS AGAIN REQUIRED FOR A BIRD STRIKE AT AN OFF LINE STATION BY A CONTRACT FBO MECH. THE RPTR STATED THE FBO MECH WAS GIVEN VERBAL INSTRUCTIONS BY A MAINT CTLR ON THE PHONE ON HOW TO REMOVE THE CAP TO TURN THE COMPRESSOR FOR BLADE INSPECTION. THE RPTR SAID THE FIRST FLT AFTER THE OFF LINE INSPECTION THE ENG SEIZED ON TKOF DUE TO LOSS OF OIL. THE RPTR STATED THE CAP, 'O' RING SEAL AND SNAP RING IS SUBJECTED TO 50 PSI OF OIL PRESSURE. THE RPTR STATED THE INSPECTION OF THE FAILED ENG REVEALED THE CAP WAS THE CAUSE OF THE OIL LOSS AND SUSPECTED THE SNAP RING WAS INSTALLED INCORRECTLY. THE RPTR STATED THE MAINT MANUAL WAS UPDATED IMMEDIATELY TO CHANGE PROCS AND INSPECTION TO AVOID THIS TYPE OF INCIDENT.

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.