Forum: Civil and General Aviation

The other day I was catching a flight out of Juneau in a 737-400 (Alaska Airlines Make-A-Wish 737). We went through a rough patch that had a lot of rain. Sitting by the forward part of the wing I could see the water going into the CFM-56. What I am wondering is how much rainwater can go in before there is a problem? Also, does a small amount of rainwater act like a water injection system to cool the combustion chamber?

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You should see how much soapy water out of a firehose we would spray into an A-10's TF-34 while running it to remove the gunsmoke residue from the fan. No problems (lots of suds) for High-bypass Turbofans like that.

Occamsrasr wrote:

What I am wondering is how much rainwater can go in before there is a problem?

A WHOLE lot! Shocked

"Worse than a typhoon" is what engines are tested against.

This video shows a GE90-115B being tested against 1100 gallons per minute (4.5 Tons/Min) then being accelerated to take-off power! Cool

Watch Here @ 1:12+:http://www.youtube.com/watch?v=5xlObdXF8VE
Now the 737's CFM-56 isn't near as large as the GE90-115B, but you get the idea...

Occamsrasr wrote:

does a small amount of rainwater act like a water injection system to cool the combustion chamber?

Anything that affects the density or mass flow of the engine will affect it's performance. As for cooling the combustion chamber, yes, the engine will cool somewhat, but to what extend is dependent on the amount of water. Water injection of jet engines will lower Specific Fuel Consumption (SFC), NOx emissions, and lower all hot-section temperatures while maintaining thrust.

Keep 'em flyin' Thumb

TEG
(EDIT - Forgot the link Doh

)

Forum Veteran Joined: Dec 15, 2006 - 12:28 AM Posts: 760

As long as it’s not too much water some water (water injection) can actually increase the efficiency of combustion ( power and fuel economy) of an engine whether it be a jet engine or reciprocating.

On some older military aircraft there was a throttle position for takeoff and for war emergency that included a few minutes of water injection.

There are certification test for water ingestion that far exceed the typical rainstorm. Though there is a chance probably less than winning a lottery that you could flameout from ingesting water at altitude.

While there is never any guarantee that there will not be a flameout the engines are thoroughly tested and certified to resist flameout from water ingestion.

Please note @ 1 minute that during this manufacturers test at 4.5 tons of water per minute the engine runs fine but there is one heck of a rooster tail.

E90-115B Gas Turbine Jet Engine Testing & Evaluation
http://www.youtube.com/watch?v=5xlObdXF8VE

ATFS_Crash wrote:

...some water (water injection) can actually increase the efficiency of combustion ( power and fuel economy) of an engine whether it be a jet engine or reciprocating.

On some older military aircraft there was a throttle position for takeoff and for war emergency that included a few minutes of water injection.

Engines with the injection feature had specs for "dry" and "wet" thrust (when the water was added). SAC's early 135s with the J-57 engines are a classic example. According to some sources, the water allowed a second set of fuel injectors to activate for extra t.o. power without melting critical engine components. But don't hold me to that 'cause I ain't an engine guy. Unbelievable amount of smoke and steam on takeoff.

A high school friend of mine works at the GE test site in Peebles and says whenever they do the FOD or water tests, there's always a crowd that watches from a distance. Never know what'll happen. Wink

wow. I knew they could take some water, but DAMN. you couldn't get any more in there if you tried, short of submerging the thing in a big ole swimming pool

There have been several commercial aircraft flameout incidents due to rain or rain and hail. Here are a couple of examples.

http://en.wikipedia.org/wiki/TACA_Flight_110

http://en.wikipedia.org/wiki/Southern_A ... Flight_242

Forum Veteran Joined: Dec 15, 2006 - 12:28 AM Posts: 760

johnwill wrote:

There have been several commercial aircraft flameout incidents due to rain or rain and hail.

IIRC. TACA Flight 110 wasn't quite a full-fledged flameout. I think the heavy rain forced the engine into a limp in idle mode and for some reason it wouldn't throttle back up. I'm not sure if they were still in heavy rain when the pilot tried to advance the throttles. Since the engines wouldn't throttle up I think the pilot elected to shut the engines down and do a dead stick landing. Miraculously he landed the aircraft safely on a levy with little or no damage to the aircraft and they were able to latter fly it out. I think it's the only time a major airliner made an emergency landing safely other than an airport.

Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

ATFS_Crash wrote:

I think it's the only time a major airliner made an emergency landing safely other than an airport.

Well, until US Airways 1549 anyways. Very Happy

While not exactly "emergency landings safely other than an airport", here are some examples of brief encounters with terra firma away from an airport.

http://www.airliners.net/aviation-artic ... .main?id=5

The brief landing outside of Nairobi was interesting, as I was acquainted with one of the passengers on-board that night, Porter Randall of Fort Worth. He told me the passengers did not know they had touched down, thinking it was only a little turbulence, followed by unusually load engine noises.

Forum: Civil and General Aviation

Water in engine