You irish even put beer in your avgas 
Peter wrote:
One view is that it takes some hours for the liquid water to settle on the bottom of the tank, so there is no point in checking if the plane has just been moved around. I think that must be right.
It’s much quicker than that. Conventional wisdom has it that it takes round 15 mins or so in a Cessna. As @Graham points out, you can check for yourself by purposely adding water to the freshly drained 100LL in the tester.
Airborne_Again wrote:
You’ve been lucky.
How do you suppose it got there? I have never seen anything like that. One or two drops at most, and that very rarely.
For an aircraft that lives in a hangar and is always left with a full tank, I prefer to leave the drains alone lest they refuse to close properly. In my (admittedly limited) flying experience, I’ve seen far more leaking drains than I’ve seen water in fuel.
Actually in the last hour I’ve just assisted someone in replacing a drain that had refused to close properly. It can be done without spilling too much avgas, but be prepared for a bit.
Graham wrote:
How do you suppose it got there?
I know exactly how it got there. The aircraft was parked outside in heavy rain. That’s happened to me twice, in different aircraft.
I have got water in a hangared aircraft, too, but not nearly as much. Leaving the aircraft with full tanks is a luxury you can’t afford with a club aircraft as you never know what payload-related fuel restrictions the next pilot will have. Defuelling is a hassle you really want to avoid.
Actually in the last hour I’ve just assisted someone in replacing a drain that had refused to close properly.
Thank you Graham :)
Airborne_Again wrote:
I know exactly how it got there. The aircraft was parked outside in heavy rain. That’s happened to me twice, in different aircraft.
I would suggest that an aircraft where the tanks allow the ingress of rainwater whilst parked, presumably via the filler cap seals, is in urgent need of rectification work.
Graham wrote:
I would suggest that an aircraft where the tanks allow the ingress of rainwater whilst parked, presumably via the filler cap seals, is in urgent need of rectification work.
I wouldn’t disagree with that at all. But shouldn’t the same be said for an aircraft where the drain valves don’t close properly rather than simply skipping checking for water?
Water can get into fuel via condensation in the air the tank. If not drained, it can build over time.
I’d not fly in an aircraft where the tanks were routinely not checked for water.
dublinpilot wrote:
But shouldn’t the same be said for an aircraft where the drain valves don’t close properly rather than simply skipping checking for water?
Indeed. However I didn’t say I don’t use them because they don’t close properly, I said I tend to leave them alone because of the risk that they won’t close properly, unless I perceive a particular risk of contamination.
Particular risks might include a knowledge or suspicion that the filler cap seals aren’t rainproof, or the aircraft having sat for a long time with not much fuel in the tanks. Probably the biggest risk is an aircraft on a cold morning that has sat outside overnight after a warm humid day, and particularly one that has been subject to many such cycles without being flown.
Normally when a fuel drain refuses to close it’s because it’s got some crud between the o-ring and the sealing face. It usually just needs removing, cleaning and screwing back in, but this is a pain if you’re alone because having removed the drain valve you need to keep your finger over the hole in the tank while you try to compress the spring and remove the crud with the fingers of your other hand. All assuming of course that you have a spanner and some sealant or PTFE tape to hand.
Thus it isn’t a straightforward case of “faulty drain, must replace” like it is with the filler cap seals. It’s more a case of could randomly get some crud in it and not close properly on any random occasion. And as I’ve said, I’ve seen much more of this than I have water in fuel.
An aircraft flown regularly will get a very small amount of water in the tanks each time it sits, which the engine will quickly devour next time you start it up. The amount of water required to stop an engine is really quite significant, and it needs to get a whole load of it all at once. For this to be a practical risk on takeoff, the water also needs to have (for some reason) not found its way to the engine during warm-up, taxi and power checks.
Graham wrote:
I would suggest that an aircraft where the tanks allow the ingress of rainwater whilst parked, presumably via the filler cap seals, is in urgent need of rectification work.
The particular aircraft in the photo was provided to me for a Voluntary Air Corps exercise. The leaky fuel cap wasn’t the only thing wrong with it. At one point I had a taxiway excursion (fortunately without damage, but it was very close) when the nose wheel steering suddenly disengaged in a turn. I think I wrote four log book entries, each about serious issues. That kind of proves the point repeatedly made by Peter that having an aircraft under CAMO doesn’t mean much as to its actual status.
Airborne_Again wrote:
That kind of proves the point repeatedly made by Peter that having an aircraft under CAMO doesn’t mean much as to its actual status.
Indeed. In general terms I would be far more suspicious of an aircraft under CAMO, particularly a club or school aircraft, than I would be of one where the owner conducts their own maintenance sourcing in specialist expertise where necessary.
Pencil-whipping is very common when you have the ‘cheapest possible compliance’ motive on one side and the desire to be paid for doing very little on the other side. Regulation and especially the CAMO structure offers almost no protection against this. CAAs are reluctant to hassle the companies that pay them the fees so they just pretend it isn’t happening. It is proof beyond measure that the real regulatory interest is in having the paperwork in order rather than the aircraft.
