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Fuel pressure sensor and vibration

Handclutch

Well Known Member
When I first bought the aircraft fuel pressure indications were advisory at best - highly variable and fairly frequent high-pressure alarms (but never low-pressure).

In early 2018 we did the five year hose replacement and I opted for the Aircraft Specialty Teflon fuel hose kit. Since then fuel pressure has been quite stable with just a very occasional high-pressure alarm, perhaps once every six months.

Recently, I installed the upgraded Kavlico sensor. It isn't required by the Dynon SB but I had planned to do it anyway. Fuel pressure readings went back to how they used to be, only worse. During one descent I got both a low-pressure and high-pressure warning in the space of 30 seconds.

It had me stumped. I couldn't figure out what had changed apart from the sensor, and couldn't see how it could be the cause unless it was faulty which I deemed unlikely. Finally, the penny dropped. The old sensor had always sat at a bit of an angle in the grommet but this time I went to the trouble of making sure it was perfectly vertical. That was a mistake as it turns out because it allows slight horizontal movement within the grommet and therefore vibration.

Angling the sensor so that it is more firmly held has solved the problem. Two flights now and the indication is quite solid with no alarms. It seems you need the sweet spot of holding the sensor firmly enough so that it can't move but still have it insulated from engine/airframe vibration.

Aways something to learn!


Jack
 
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