Fuel straining in larger aircraft

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Engine

Pre-takeoff checklist
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Engine
I’ve been noticing that non of the pilots that fly larger airplanes (such as TBM850) never strain their fuel. Any idea why not?
We do it all the time in GA aircraft in order to inspect fuel contamination, logically I can’t think of a reason why the fuel in a larger aircraft can not get contaminated the same way.


Thanks in advance
 
Typically turbine engines don't sump their fuel. I think it has to do with water will go through a burn can and not put out the fire. Plus, every turbine I've flown has the pumps at the lowest point in the system. So if there is water it would settle there.
 
Inverted said:
Jet engines will burn anything. I have never sumped a turbine.
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I have on turbine helicopters and small GA type twins (King Airs, etc) but on large turbo props and transport jets, no.

On the transport jets and large turbo props it's a maintenance function to sump tanks on an inspection interval.
 
Look up the specs for a Pratt & Whitney JT9D, such as those used on the first-generation Boeing 747. Those were designed to intentionally inject water at takeoff, to control the temperature and mass density of the exhaust. And it was massive too, something like 5,000 lbs over a few minutes, divided among the four engines.

I'd hazard a guess that water ingestion by a jet engine isn't a factor....
 
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Water does not separate from jet fuel like it does from avgas so it would be a waste of time. Just run your hot hydraulic lines through the fuel tanks so it doesn't freeze because that's all you have to worry about.
 
Silvaire said:
Water does not separate from jet fuel like it does from avgas so it would be a waste of time. Just run your hot hydraulic lines through the fuel tanks so it doesn't freeze because that's all you have to worry about.
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Most large jets cool the engine oil with the incoming fuel using a fuel/oil heat exchanger. There still are temperature limits for operation because as the fuel reaches the freeze point, waxes in the fuel start solidifying. In long range jets, this becomes an operational factor.
 
Sumping the tanks is on the preflight check list for all King Airs. Pilots don't do it for a number of stated reasons as well as some that are unstated--such as not liking to do it.

I don't sump because the engines have never seemed to care and the risk of developing a leak. Tank bladders in the area of the sump and the sump hardware itself are somewhat problematic, and sump drains that are tighter than a frog's ass can develop leaks due to FOD (miniscule rock particles/chips, balls or chunks of sealant and other stuff) that are are seemingly impossible to stop.

Any drip or leak, especially on a FBO ramp or other public spot (parking areas) is a major cause for concern of the ramp operator and can result in all sorts of barriers and containment devices being deployed around your airplane. It's not something you want to be famous for at the line shack.
 
MAKG1 said:
Look up the specs for a Pratt & Whitney JT9D, such as those used on the first-generation Boeing 747. Those were designed to intentionally inject water at takeoff, to control the temperature and mass density of the exhaust. And it was massive too, something like 5,000 lbs over a few minutes, divided among the four engines.

I'd hazard a guess that water ingestion by a jet engine isn't a factor....
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Geesh that's a lot of water! Where do they get it all? Do they have water tanks that are topped off before flight...?
 
jonnyjetprop said:
Most large jets cool the engine oil with the incoming fuel using a fuel/oil heat exchanger. There still are temperature limits for operation because as the fuel reaches the freeze point, waxes in the fuel start solidifying. In long range jets, this becomes an operational factor.
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All heat exchangers are an attempt to economize. The oil needs to be cooled and the fuel needs to be heated. Both have an excess of what they don't need so a trade is in order.
 
When I first started flying a King Air, I would sump the fuel. I quickly learned my lesson.

Sumping fuel on a KA is a maintenance item. It is too easy to get a sump leaking or actually stuck wide open. This makes a BIG mess and ruins your leisure suit.
 
The military still sumps fuel, and we have had cap gaskets fail and pulled literally gallons out of a tank.

On the civilian side I still pull fuel, just not as often.
 
MAKG1 said:
Look up the specs for a Pratt & Whitney JT9D, such as those used on the first-generation Boeing 747. Those were designed to intentionally inject water at takeoff, to control the temperature and mass density of the exhaust. And it was massive too, something like 5,000 lbs over a few minutes, divided among the four engines.

I'd hazard a guess that water ingestion by a jet engine isn't a factor....
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But the water is not injected into the burner cans like water in fuel would be. It is injected into the front of the compressor where it evaporates thereby cooling the incoming air which of course allows the engines to produce more power. Used to fly Metroliners that had it and it was very noticeable when we shut off the water. You would lose quite a bit of power.
 
jpower said:
Geesh that's a lot of water! Where do they get it all? Do they have water tanks that are topped off before flight...?
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The B-52G had a 10,000 pound water tank (about 1200 gallons) forward of the wing for water injected takeoffs. Four pumps (one for each engine pod) were turned on once initial thrust was set. The difference was very noticible. The water would last for 110 seconds and usually ran out about halfway through flap retraction requiring the throttles to be shoved forward.
 
There has been no mention about algae growth in jet fuel, which I would see as the primary purpose for sumping oil burners. That stuff will quickly stop up the works.

I guess with the preventatives in todays fuel it doesnt need to be checked any more?
 
Nothing like a wet takeoff in a Metroliner :D



Busflyer said:
But the water is not injected into the burner cans like water in fuel would be. It is injected into the front of the compressor where it evaporates thereby cooling the incoming air which of course allows the engines to produce more power. Used to fly Metroliners that had it and it was very noticeable when we shut off the water. You would lose quite a bit of power.
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RotorAndWing said:
I have on turbine helicopters and small GA type twins (King Airs, etc) but on large turbo props and transport jets, no.

On the transport jets and large turbo props it's a maintenance function to sump tanks on an inspection interval.
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Interesting. I was taught, and practiced never draining the King Air or Beech 99. Of course on the Lear it is laughable.
 
Busflyer said:
But the water is not injected into the burner cans like water in fuel would be. It is injected into the front of the compressor where it evaporates thereby cooling the incoming air which of course allows the engines to produce more power. Used to fly Metroliners that had it and it was very noticeable when we shut off the water. You would lose quite a bit of power.
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ADI in the Metro is so freaking necessary lol. It is very limiting without it actually.
 
We use pre-mix.

bluerooster said:
There has been no mention about algae growth in jet fuel, which I would see as the primary purpose for sumping oil burners. That stuff will quickly stop up the works.

I guess with the preventatives in todays fuel it doesnt need to be checked any more?
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He was talking about feeding water through the engine via the air intake, not the fuel system AFaIK. But aside from any negative impact on the pumps and valves that should have the same effect on combustion as both sources (fuel and air) come together in the burner.
 
Thank you guys! Very informative.

Another question has since come about; why aren't big avgas airplanes sumped? At my job we have an aviation museum which has a DC-3, B-17, PBY Catalina, etc and I have never seen them once sump the tanks. We've also gotten things like a DC-7 and a TBM Avenger which I've personally fueled and seen the pilot get in and go. Either this is just lazy piloting or I am missing something.

As for the SA227, are all of them fitted with water injection? A friend has a Metro III and I've flown a couple of repositioning flights with him yet in the year that he has owned it they haven't used the AWI once. Nor did he mention it on any of our flights. Granted we always had plenty of room 5000+ ft almost always at sea level. I've never even seen it be filled with the stuff.
 
Engine said:
As for the SA227, are all of them fitted with water injection?
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It was an option.

Engine said:
A friend has a Metro III and I've flown a couple of repositioning flights with him yet in the year that he has owned it they haven't used the AWI once. Nor did he mention it on any of our flights. Granted we always had plenty of room 5000+ ft almost always at sea level. I've never even seen it be filled with the stuff.
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If the airplane is light there is no need for a wet takeoff.
 
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