Another FE stood in and assisted the PC with the preflight. Fortunately, our unit worked well together and all FEs were familiar with the eight aircraft assigned to us, including the problems with each aircraft. The PC completed his preflight and the "stand-in" FE locked down all the cowlings, panels and tunnel covers. He then reinstalled all covers and tie-downs in preparation for leaving the aircraft outside for the night.
When I arrived the next morning, I grabbed my gear, logbook and fuel sampling equipment and made my way out to the flightline. When I left the hangar the night before, I could see five aircraft tied down on the flightline. On the aircraft we were taking this morning, I noticed the combining transmission (C-box) cover missing. I stopped for a moment, but then reminded myself that one of the eight aircraft had a missing C-box cover for some time now.
As I approached the aircraft, I assumed this was the aircraft with the missing cover. I continued to get ready for the mission, performing my fuel sample and removing the tie-downs and covers. I double-checked all the latches, panels and tunnel covers for security. Completing a final review of the logbook, I got ready for the mission. This was my second mistake, since I didn't check the logbook for any notation of a missing C-box cover, which would have been required to order a new one.
The rest of the crew arrived and the aircraft was ready to go. About 45 minutes into the flight, my crew chief and I were conducting a ramp and cabin check. I was performing checks upfront while she was in the back of the aircraft checking the maintenance panel and various other areas. She turned to me and asked if I smelled something burning. I checked and the only odor I smelled was hydraulic fluid, which is usual on the ramp of a CH-47D. We double-checked all the levels, temperatures and pressures. There was no indication of any problems, so we monitored the area.
We reached our destination with no incident or hint of odor. After we shut down, we performed a postflight inspection, in which I went straight to the C-box area and found the missing cover. After a quick inspection, I saw an entangled mess -- the C-box cover was located in the No. 7 driveshaft and the C-box forward adapter.
Fortunately, the cover had spun with the driveshaft and didn't lodge or cut into the shaft. The only sign of damage was some slightly worn paint from the shaft. What we had smelled was probably the C-box cover heating up as it rubbed against the shaft. We cleaned up the area, found all five metal hooks and removed all canvas bits. Then, after further inspection, we received clearance from maintenance and were able to complete our mission and return home.
Lessons Learned
There were many lessons learned that could have prevented this incident from happening. Fortunately, this did not turn into a catastrophic incident and we were able to return home safely. I thought I knew this aircraft well. However, when I noticed the cover missing during the beginning of the mission, I had already talked myself into believing this was the aircraft with the missing cover. In fact, that particular aircraft was in the hangar. I reviewed the logbook, but I never noticed the cover written up or the part placed on order. I should have caught the write-up because I knew accountability for the cover was important. My assumption could have caused a disastrous accident.
One other lesson learned … in airframes that require a crew of three or more, an FE or CE really should be present to conduct the preflight with the pilots. Someone should have accounted for the cover. Then, of course, a proper recon of the logbook would have prevented the incident.
Additionally, the FE who performed the preflight should have never placed the cover down on the airframe in the driveshaft area. After we reported this incident to the facility, we conducted a safety meeting to prevent these types of maintenance errors. When questioned about his mistake, the FE who performed the preflight was adamant he had not left the cover in the C-box area. In aviation, it is very important to admit when you are wrong. This maintains that level of integrity and lets others know we are really looking out for the best interest of others and the mission. When incidents like this happen, it is far more forgiving if one can admit the mistake, learn from it and share the lessons learned.
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