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#1
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Fuel Guage Error
A brief story some who operate early Skymasters with mechanical fuel senders might find valuable as it points to a safety of flight issue. Search function, while bringing up numerous issues did not seem to illustrate the point. Last week while traveling down to SnF’ and back I noticed the fuel guage for the port side aux. tank which had heretofore been operating accurately, now seemed to be reading erroneously. After 30 minutes of burn time it was still indicating full and after 55 minutes of burn time it was reading 6 gallons. While contemplating what the problem might be and how much longer I was going to burn it ATC called with the third rerouting of the trip. This distraction took my attention away from fuel management just long enough for the front engine to suck air and extinguish the fire. After switching tanks and, with the help of the boost pump, restarting the motor, I said to myself “Self, lets switch tanks at 6 gallons indicated for the rest of this trip.” On returning home I began to investigate what might be the problem. Checked all wire connections at the sender and guage for security with nothing found. Checked the sender for binding or deformity of the float arm with nothing found. Removed the sender from the tank so as to operate the float arm manually. Now the guage reads perfectly, zero fuel at the bottom stop, full fuel at the upper stop and a linear progression between the two. Well, that’s interesting. Used an abrasive pad to brighten the sender ground strap and attach point and reinstalled the sender in the tank. Voila’, works beautifully. So, the first lesson learned is that these senders fail unsafe or to a full indication if they lose ground connectivity rather than fail safe or to an empty indication. Second lesson, if you think your gauges are reading high, check for a good ground. Third lesson, which of course we all know already, use fuel gauges with a high level of suspicion.
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#2
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Not particularly relevant, but on the subject of using the aux tanks I found out several years ago that it's a good idea to stay in balanced flight when near the end of the aux tank feed. I was finishing up a bird survey and nearing the end of the hour on the rear aux tank (had already switched the front back to the main-I stagger them by 5 mins) when the scientist with me asked if I could "do that forward slip thing" so she could take some pics out of the left hand photo port.
As soon as I rolled the plane and fed in opposite rudder, the rear engine let me know it wasn't happy...and neither was my scientist observer! Joe |
#3
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Aux fuel tanks, LEVEL FLIGHT ONLY
__________________
Herb R Harney 1968 337C Flying the same Skymaster for 47 years |
#4
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You mean you can't make any turns while on aux tanks? :-)
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#5
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climb,climb,climb
as an interesting note, and you can try this out for yourself up at a safe altitude....if your aux tanks are low (not sure at which point exactly, but let's say half or less in them) and you are in descent, they will 'unport' and its as if you've run out of gas. But you can climb on low aux tanks all you like.
don't ask me how I know all this for sure, but just know it will be an uncomfortable moment if you are in descent for landing and suddenly your engine shuts off because you forgot to switch back to mains as part of the landing checklist....especially if it happens to you more than once |