COMANCHE TECH TALK

WHEN A STEEL CABLE MEETS AN ALUMINUM TUBE

As told to Omri Talmon by Michael Gutstadt

Michael's aircraft, a PA-39-131, registration 4X-CCG, was brought in for a routine 100 hours inspection.  Following completion of the inspection Michael took the aircraft for a test flight. After landing he scented fuel odor, notified the FBO and it was convened that the matter will be checked shortly. A couple of days latter Michael came to look at the aircraft and noticed a large stain underneath it, slightly to the left.  He looked into the left main (the fuel selectors were left on MAIN) and could see only the rubber bottom. Not a drop of fuel.

Back to the FBO.  Some fuel was poured into the left main and shortly thereafter fuel started to drip out of the panel aft of the fuel selector panel.  The selectors, as well as all fuel tank connections, seemed to be in perfect order.  Apparently the fuel was coming underneath the floor, on the left side of the fuselage. This called for the removal of the left front floor panel and to the great astonishment of all – there was the culprit.

It was the fuel line which runs from the electric boost pump to the engine. En route is crosses a steel cable galore (All cables which operate the control surfaces).  For an unknown reason the aluminum tube got in touch with one of the cables which started sawing it until the slot became deep enough and fuel started to run out.  There are also marks produced by other cables.  It is possible that during a former (1000 hours) inspection, when the floor was removed, the tube was somehow pushed down.

The damaged tube was replaced and the new one positioned at a respectable distance from the cables.

The moral of the story is: Whenever the left front floor is removed examine the fuel line as well as its distance from the cables, and care should be taken not to bend the tubing and get it too close to the cables.  Further – always be on the alert for fuel leaks.

The following pictures tell the story