not seeing Picture 3 Picture 4 Picture 5 Guess what Picture 5 shows. No, it’s not
a petri dish full of the latest horror bug, though it does rather look as if it might be. The debris was found in a fuel funnel filter’ after a recent re-fuel. The fuel system would have been compromised had this muck found its way into the tank. After finding the debris the pilot decided to check-out where it came from and, after a bit of detective work, he established that it was the remains of the glue from duct tape used to connect an extension to his fuel delivery pipe. The oil filters in Picture (6) show a ‘good’ one (on the right) and a ‘bad’ one (left). The Jabiru J400 it came from became covered with oil during a post-maintenance ground run because the filter wasn’t sealing correctly. Initially it was thought that the threads had been cut at an incorrect angle and the filter wasn’t seating as it should but, on further inspection, it was discovered that the flange which connects the base to the bowl was faulty.
Picture 6 It’s not just seeing that can alert you
to issues, hearing plays its part too. The tailplane of an MCR 01 Banbi was removed to investigate why it sounded ‘rattly’ while manoeuvring it in the hangar. The close-up (Picture 7) shows a failed
port tailplane attachment bracket. Not only was the security of the tailplane attachment compromised, there was also a strong possibility that if the aircraft had been flown the tailplane could have fluttered at normal airspeeds, potentially leading to the loss of the tailplane. Another carburettor issue featured
on this Tecnam P92 Echo, powered by a Jabiru 2200, which suffered a failure of the attachment rubber. A hole in the rubber like this (Picture 8) is very difficult to spot without removing the rubber itself. Because of the reduced manifold pressure at this point in the induction system, fresh air can enter the manifold through the hole, weakening the mixture and causing loss of power and, under some
Picture 7
circumstances, higher than normal running temperatures.
Had this been on a two-stroke engine
it would probably have caused an engine seizure. A tell-tale symptom for this kind of problem that’s worth remembering is an increased idle rpm. So next time you’re checking things out,
perhaps it’s worth thinking, ‘am I really seeing (and hearing) what I’m looking at’?
Thanks to Malcolm McBride, Airworthiness Engineer for the LAA, for his help with producing this article.
Summer 2018 CLUED UP 31 Picture 7
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