Jet Engines in the Rain?

I think there is plenty of stuff indicating that small amounts of water injected into an Piston engine (petrol) air intake improves the performance slightly.

Maybe same for jets... ?

This must have been just after takeoff, just before landing, or in a very short flight! At cruising altitude all water is ice, even over the equator (High altitude clouds are just very tiny ice particles).

In any event, if water weren't so heavy, they would be doing that all the time intentionally! Once that water gets to the combustion area, the droplets have all been bounced back and forth between many sets of compressor blades and broken up into a mist or finer.
The heat of combustion will evaporate the water, causing lots of expansion(which is what the burning fuel was doing anyway), which pushes on the turbine blades even more, and gives the engine additional power.

Most Jet Engines today are high bypass which means 90 percent of the air that goes in the intake gets push out the side and only 10 percent goes into the combustion chamber . Also know as a Fan Jet. When rain hits this type of jet engine it thrown by out the side some still goes through the engine but behaves as the last reader that posted before me said, A lot of rain has to go through and engine to kill it. On the ground in an emergency the fire crew can stop the jet with a fire hose though it has to be a pretty big hose to drown the motor but foam added will help. fire hoses put out between 100 to 250 gallons a minute which is far more than the jet will encounter with rain.

I read once that the cockpit crew switches on the electronic ignition when running through rain (it is normally switched off when the engine is running and warmed up after takeoff...) as a safety precaution.

All such engines are designed to swallow vast amounts of water and still keep running.....

But the rain will cause some fan blade erosion, which could cause a reduction in TBO (time between overhaul) of the turbine engine. One more reason for the wide variety of inspections and checks done periodicly in the hangers.

Check this video out http://www.youtube.com/watch?v=faDWFwDy8-U

on a modern, high bypass engine most of the water won't get near the combustor.

From Rolls Royce website:

"The equivalent of 33,000 gallons of water an hour is sprayed through a civil aerospace Trent engine. For the engine to be given certification this test must not result in any loss of rated thrust."

Thats not a jet engine, its a high speed water pump!!!!

Only joking!!!

A couple older, low bypass, jet engine military aircraft utilized water injection on takeoff to increase thrust. The water was purified to keep mineral deposits from damaging the compressor blades.

That sure brings back memories...sitting on the line watching 15 B52s taking off 'on water' with a 3 second MITO. Always a good rush.

G model buffs (and I think the D did also) used a J57 turbojet with water injection that greatly increased density for greater thrust. H model went to turbofan.

Remember the films of Richard Noble's team running a hole into the engine of one of the Thrust land speed record cars to get the power back? Apparently the thing wasn't living up to it's name due to airborne crud at ground level. The things like clean air for some reason.

'The things like clean air for some reason.'

Good point....any one know where we can get some?

I work for a company commissioning gas turbine power plants, we inject demin water direct into the gas path at a rate of 1,300 gpm helps reduce nox gas out put and increases thrust out put. We also have what we call Mefog witch is a fog of high pressure water sprayed into the in take at a rate of 800 gpm witch cools intake air and adds mass to the intake air improving engine thrust out put

Sort of an Ultra Modern steam engine/turbine!!!

I've never flown a jet myself, but I have flown piston aircraft.

Cold dense air is good for performance of the engine typically, though you need to keep the carborator clear of ice with some regular carb heat in high humidity.

I've done my fair share of hangar flying and have never heard of an engine failing because of flight through rain.

When I was a lineman we often filled ADI tanks with water and alcohol for injection into the engine cylinders for added power at take off. It has been a long while since I did that, but I seem to remember that the Boeing 707 engines used water at take off, along with Convairs and DC 4s & 6s, though it may have been only the Convairs that had a regular demand for ADI.

Of course pure water would be best to use up completely before you got to altitudes that turned it into a rock and lowering the freezing temperature is therefore desirable.

Typically it is not a good idea to fly in bad weather more because of microbursts, wind shear, and other forces and aspects like icing, than engine performance.

Switchman. The older versions of the KC-135 used J-57's with water assist too. Growing up on a base with buffs and tankers, I can also remember the roar produced by the mighty birds.

Well, hail is a different animal. In the late 70s I think, a Southern Airways DC-9 crashed in Georgia in the good ole USA after rain flamed out both engines AND hail broke the windshield during a severe thunderstorm. The pilot then attempted to land on a road but didn't make it.

Do 'they' know that it was rain that 'flamed out' the engines?

Hail large enough to break the windshield might be more of a problem than the rain...

The guest thread was initiated by a passenger observing "buckets of rainwater" going into the engine they could see.

Hail is right different from rain, though if you have ever handled a turbine blade, they are obviously right strong.

The DC 9 engine placement is one I can see as vulnerable to a flameout in combination with large hail and rain since hail bouncing off the wings could well throw an incredible amount of ice into the engines at certain angles of attack.

Ice and a rock feel the same when they hit my skin and I can see ice jamming a jet engine up, though it really does take a lot to make a jet engine fail from what I've seen.

If the angle of attack was into the wind and the DC 9 was climbing then at the right angle of attack the engines would be shelded some by the wings. If it was climbing in a tailwind or decending it would make a difference.

And of course the size of the hail would be important.

The fact is that flying in bad weather is dangerous no matter what sort of plane you are in. There is not a machine made by man that can overcome every weather all the time.

I read somewhere that the ignition (whatever that is on a jet engine) should be switched on permanently when flying through rain, maybe the pilot of the DC7(?) forgot?