Interesting topic…
If the lever operates the valve directly then there must obviously be something very seriously wrong with the valve. I have seen the one (well, the fuel selector) in the TB20, and there is nothing to go wrong, so if it is not sealing properly it means something is shredded and you can expect bits of “stuff” in the the next thing downstream which I think is the large metal-mesh fuel filter (gets checked at every Annual; a pointless mandatory replacement under EASA every 2 years or so, and very expensive) and after that you have the fuel totaliser turbine at which point things would be “very interesting”.
But if the lever operates via a linkage, then presumably that is the most likely problem. Does this stuff get eyeballed at the Annual? I mean to make sure that the extremes of the lever position actually produce extremes at the valve position? Just like one does with the throttle, prop and mixture levers, which normally operate via cables.
Michael – you could use a somewhat different tone, perhaps??
Incidentally, the AAIB report for the Barton crash
Many years ago I checked the fuel selector on some of the aircraft I flew (all single engine). I never saw a selector unable to cut off fuel, and so I have never thought of that as a problem to be aware of. My interest was mainly to see how long it took the engine to stop (longer than I expected) and how long before it restarted after opening the fuel valve again (for engines with fuel injection, even longer).
On one occasion, after reported engine irregularities, I test flew an old PA-28-140 with a fuel selector without detents, to see if there was any position between “left” and “right” that would cut off (or even limit) the fuel. There wasn’t. But I also found that the selector would have to be turned all the way to the “off” position to turn off the fuel. Turning it almost to the “off” position allowed the engine to keep running at cruise power at least.
Balliol wrote:
Could you put fuel pump on and then observe what the drop in fuel pressure is like with the valves operation giving an indication of whether it is partially closing or not at all?
I s’pose, but isn’t the engine beginning to stop a better and more direct measurement of what you want to know?
Peter wrote:
If the lever operates the valve directly then there must obviously be something very seriously wrong with the valve.
In each of the cases I am reporting, it was failure of the rubber seals. I have no more detail than that. We replaced a lot of valves.
I don’t think the fact that they were cable operated made any difference.
Timothy wrote:
On the aircraft I am talking about they are stopcocks which cut off the fuel.
Mind letting us know which aircraft types you’re referencing ?
(Never seen 10 stopcocks and zero fuel valves on ANY aircraft type, but there’s always a 1st … or not.)
(deleted)
posts purely intended to annoy one or more people are all examples of things which don’t meet these objectives and are likely to be deleted.
huv wrote:
Many years ago I checked the fuel selector on some of the aircraft I flew (all single engine).
As mentioned, this problem, mis-alignment of fuel selector valves, is much more prevalent in twins since the fuel valves are generally placed in the wings which requires either cables or rods and bellcranks that tend to wear out.
