Ice in fuel tank?
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Ice in fuel tank?
I was the first to fly our club TB9 on Saturday morning, so did the usual 'A' check. Sampled all three fuel drains - had a good sniff of each sample - definitely looked and smelled like Avgas, no sign of water contamination.
Uneventful flight, but the instructor who took the aircraft out immediately after me also sampled the fuel, and spent 5 minutes draining water from the RH tank. The a/c hadn't been re-fuelled after my 45 min flight.
As well as feeling that luck was on my side that day, I've been beating myself up trying to figure out how I missed so much water.
The aircraft had been parked out overnight (as usual) with tanks full to the brim. The temperature overnight had dropped to below freezing, but by the time I did my 'A' check all signs of frost on the ground and on the aircraft had gone, but it was still pretty cold.
So - my question is this - is it possible that the water in the tank had frozen overnight and there was a big lump of ice at the bottom of the tank? Could it be that the water was sitting elsewhere and only moved to the drain after I'd sampled?
Any thoughts appreciated, as realising that I'd flown with so much water in a tank was a bit of a shock. How can I make sure this doesn't happen again?
Uneventful flight, but the instructor who took the aircraft out immediately after me also sampled the fuel, and spent 5 minutes draining water from the RH tank. The a/c hadn't been re-fuelled after my 45 min flight.
As well as feeling that luck was on my side that day, I've been beating myself up trying to figure out how I missed so much water.
The aircraft had been parked out overnight (as usual) with tanks full to the brim. The temperature overnight had dropped to below freezing, but by the time I did my 'A' check all signs of frost on the ground and on the aircraft had gone, but it was still pretty cold.
So - my question is this - is it possible that the water in the tank had frozen overnight and there was a big lump of ice at the bottom of the tank? Could it be that the water was sitting elsewhere and only moved to the drain after I'd sampled?
Any thoughts appreciated, as realising that I'd flown with so much water in a tank was a bit of a shock. How can I make sure this doesn't happen again?
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Other than ice, which sounds very plausible, does the TB9 by any chance have rubber fuel bladders like Cessna?
These are known to wrinkle and trap water in the wrinkles. Rocking the wings before sampling will at least alert you to the presence of water.
But I'd be interested in a failsafe way of detecting water in freezing conditions in any case.
These are known to wrinkle and trap water in the wrinkles. Rocking the wings before sampling will at least alert you to the presence of water.
But I'd be interested in a failsafe way of detecting water in freezing conditions in any case.
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Sure, water freezes in the tanks...part of the reason you need to sump and test the fuel each time you fuel...even when you fuel it up to leave overnight.
Chances are that if the water was coming out after your flight, it wasn't just thawing. Simply walking up to the airplane and sumping the tanks is inadequate. You need to actively rock the wings and in many cases raise and lower the tail. Work that water down to the low points, because up until then, it could be anywhere.
One more good reason to thoroughly warm your airplane before flight.
Chances are that if the water was coming out after your flight, it wasn't just thawing. Simply walking up to the airplane and sumping the tanks is inadequate. You need to actively rock the wings and in many cases raise and lower the tail. Work that water down to the low points, because up until then, it could be anywhere.
One more good reason to thoroughly warm your airplane before flight.
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How long will it take, if I rock the wings, for all the water to settle at the lowest point where it can be drained? i.e. if I rock the wings at the start of the A check, will I be able to get all the water out at the end of it (for example)?
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I did actually rock the wings at the start of my 'A' check, although the reason for doing so was more to check for failure of the main spar. I was taught to do this by one of my instructors, although personally I would have expected any such major failure to have been pretty obvious, but I still do it.
I guess there would have been a delay of a few minutes after rocking the wings to taking the samples.
I guess there would have been a delay of a few minutes after rocking the wings to taking the samples.
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Unfortunately you cannot usefully rock the wings of anything much larger than a C150.
I am also not sure whether rocking the wings is a good idea because it might redistribute water that has collected nicely around the drain hole, just as it should.
Ice accumulation is a possibility but it tends to happen in climates where you get constant sub-zero temps; this is very rare in the UK. There have been airliners which were constantly operating in sub-zero and were found to be carrying massive lumps of ice weighing several tons.
I am also not sure whether rocking the wings is a good idea because it might redistribute water that has collected nicely around the drain hole, just as it should.
Ice accumulation is a possibility but it tends to happen in climates where you get constant sub-zero temps; this is very rare in the UK. There have been airliners which were constantly operating in sub-zero and were found to be carrying massive lumps of ice weighing several tons.
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definately looked and smelled like Avgas,
Try spitting into the sample, if the spittle sinks, its avgas; if it floats, you have avgas-flavoured water.
The alternative test is to use a lighter.......
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A C210 I fly had water delivered into the tanks during a fuelling one time. It took the mechanics about 3 weeks of jacking the aeroplane up first on one side then on the other to move the water around sufficiently to finally get rid of all of it. That was quite an eye opener for me. I've experienced large amounts of water draining from a Lance after it sat out all day in the rain, and assumed I'd got all the water after 3 or 4 cups emptied out. I guess every plane and every situation is different.
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Try spitting into the sample, if the spittle sinks, its avgas
How level is the location where the TB9 was parked?
If the parking location has a bit of a slope, then it would not be a surprise if water appeared when it was placed upon a level area.
Yes, water could freeze overnight, but I suspect it would take a significant warming over the freezing point and time to reliquify it.
It's usually colder aloft but inversions are more common in the winter.
If the parking location has a bit of a slope, then it would not be a surprise if water appeared when it was placed upon a level area.
Yes, water could freeze overnight, but I suspect it would take a significant warming over the freezing point and time to reliquify it.
It's usually colder aloft but inversions are more common in the winter.
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I fly a TB20 and have never heard of any problem whatsoever with water retention, which cannot be simply drained via the three drain points. The TB is a properly designed aircraft without any "funny business".
Have you asked at the Socata TB owners owners group www.socata.org ?
Have you asked at the Socata TB owners owners group www.socata.org ?
I would hope any water would collect at the drain points.
Did you see the water the instructor drew off?
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If there was a layer of frozen water in the tanks, does this mean the temperature of the FUEL drawn off would by definition be very near to or lower than zero certigrade?
If so . . . . if on a cold morning the temp of the drawn fuel is taken with a basic thermometer AND it is at or below zero - BEWARE - ice could be present in the tank?
Comments from someone more scientifically literate most welcome!!
If so . . . . if on a cold morning the temp of the drawn fuel is taken with a basic thermometer AND it is at or below zero - BEWARE - ice could be present in the tank?
Comments from someone more scientifically literate most welcome!!
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Did you see the water the instructor drew off?
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You could get water in the tanks from flying through rain/showers etc with old and perished fuel cap seals.
IMHO, the vast majority of water found in GA tanks gets in through perished fuel cap seals. So I guess the answer is YES it could happen in flight.
I once drained out five beakers full of water from a trainer - appalling maintenance by a company with an AOC for public transport.
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You can move the wings around and rock the airplane in all sizes. I do it in the Learjet...and that's a little bigger than a 152. Simply towing the airplane or moving it a little way can help move water to the lowest point. No, you're not worried about splashing the water out of the low point. In fact, you'll find that around the sump opening there's still a place for material to collect that doesn't go down the drain. What you're looking to do is move water from behind baffles and other locations which may trap the water.
You may be aware that a few years ago Cessna moved from a single drain in each wing to multiple drains in each wing. This occured to address water trapped behind baffles, and in tanks with bladders, in wrinkles in the bladders. Cessna has warned about it for years, but surprisingly many instructors today don't teach their students to rock the wings and raise and lower the tail or shake the airplane as part of the preflight.
The largest share of moisture introduced to fuel is through the fueling itself. If you didn't have moisture before and you did after the tanks were filled...guess where it came from? In times past fuel cap leakage has occasionally been problematic, but seldom is this the case. The lions share of fuel contamination comes from what's pumped on board. Entrained water and other contaminants come all too often with the fuel purchase. If you fuel and then go fly, that water will be settling out as you fly, and when you land you may find you have more water on board It didn't just suddenly condense, it didn't filter in there during the course of the flight. It was put there when you filled up.
I've seen gallons and gallons of water turn up in some fuel systems. I sampled a truck I suspected once and got three different colors of fuel out of it from the hose, from the top of the fuel in the tanks, and from half way into tanks (mid depth), as well as water, leaves, and a dead mouse. I found the differential pressure was too high on the filter, indicating a blocked filter, and no record of routine sampling. I found nearly eight inches of rust in the bottom of the tanks. I condemned the load, and ultimately cost the fixed based operator about ten thousand gallons of fuel. Unfortunately, not before he sold a load to a transint light airplane that got away before anyone warned the pilot.
Contaminated fuel is a big issue. It may not show up right away. You may have to work to get it out of your aircraft system, including just getting it to the low point in the tanks. Don't worry about moving water away from the low points. Worry about getting it to them in the first place. Entrained water may take a half-hour to settle out of the fuel; sumping right after you fuel may not accomplish anything. Let it settle, move or shake the airplane to get the fuel to the sump points, sump again. Sump as part of your post flight, too.
You may be aware that a few years ago Cessna moved from a single drain in each wing to multiple drains in each wing. This occured to address water trapped behind baffles, and in tanks with bladders, in wrinkles in the bladders. Cessna has warned about it for years, but surprisingly many instructors today don't teach their students to rock the wings and raise and lower the tail or shake the airplane as part of the preflight.
The largest share of moisture introduced to fuel is through the fueling itself. If you didn't have moisture before and you did after the tanks were filled...guess where it came from? In times past fuel cap leakage has occasionally been problematic, but seldom is this the case. The lions share of fuel contamination comes from what's pumped on board. Entrained water and other contaminants come all too often with the fuel purchase. If you fuel and then go fly, that water will be settling out as you fly, and when you land you may find you have more water on board It didn't just suddenly condense, it didn't filter in there during the course of the flight. It was put there when you filled up.
I've seen gallons and gallons of water turn up in some fuel systems. I sampled a truck I suspected once and got three different colors of fuel out of it from the hose, from the top of the fuel in the tanks, and from half way into tanks (mid depth), as well as water, leaves, and a dead mouse. I found the differential pressure was too high on the filter, indicating a blocked filter, and no record of routine sampling. I found nearly eight inches of rust in the bottom of the tanks. I condemned the load, and ultimately cost the fixed based operator about ten thousand gallons of fuel. Unfortunately, not before he sold a load to a transint light airplane that got away before anyone warned the pilot.
Contaminated fuel is a big issue. It may not show up right away. You may have to work to get it out of your aircraft system, including just getting it to the low point in the tanks. Don't worry about moving water away from the low points. Worry about getting it to them in the first place. Entrained water may take a half-hour to settle out of the fuel; sumping right after you fuel may not accomplish anything. Let it settle, move or shake the airplane to get the fuel to the sump points, sump again. Sump as part of your post flight, too.