1988 at Aberdeen doing what was then called an "instrument base check" in an S61N and performing an ILS to runway 16. The wind was appr. 40 kts from the west causing violent turbulence particularly below 500' agl, so the training captain told ATC before commencing down the slope that he would assess how bad it was and make a late call either for a go around, or to land and taxi back to base if it was too rough.
I struggled to keep in limits and he elected to call it a day. We taxied back and shut down, followed by me going back to the briefing room while he went to the line office to sign the tech. log.
About 10 minutes later he came running wide-eyed up the stairs and told me to come to the aircraft with him. There were several engineers standing looking at the aircraft's tail which was covered in oil and one engineer was just removing the cover from the intermediate gearbox, which was still smoking.
The normally silver-coloured gearbox was blue around the top bearing area, with brown marks presumably from overheated oil. On removal and inspection 'handfuls' of metal were extracted from the gearbox, having flaked off disintegrating gear teeth. Apparently the gearbox top oil seal hadn't been installed correctly in the factory and it came out, allowing oil pumped to the top bearing to flow through it and escape.
The finding was that the gearbox was a couple of minutes from seizing, which would have happened during the climb if we had gone around from that ILS. Thank goodness that I wasn't able to fly more accurately during the turbulence. For once a poor performance was a good thing !
(In the early 1970s I was a passenger in a helicopter which suffered tail rotor control failure in the hover and crashed on its side due to the pilot's reluctance to lower the collective. But that's a different story.)
Last edited by Colibri49; 15th Sep 2010 at 19:45.