How much water can they eat?

[floatsarmed]

Having flown through what I would call HEAVY rain on occasions, it has been niggling me as to how much rain can a turbine injest before it quits?

I have heard tales of North Sea aircraft doing the big double engine flameout :eek::mad:due to water injestion only to be re started and flown away....respect.:D

I guess it depends on the inlet / engine arrangement somewhat?

Is there a test during certification that a helicopter has to pass?

So, how much water can they eat?

Cheers
Floats':ok:

[MacBoero]

Quite a lot:
YouTube - Rolls-Royce Engine Water Ingestion Test (http://uk.youtube.com/watch?v=faDWFwDy8-U)

This video of the GE90 states 4.5 tons of water per minute!
YouTube - GE90-115B Gas Turbine Jet Engine Testing & Evaluation (http://uk.youtube.com/watch?v=5xlObdXF8VE&feature=related)

[Phil77]

EDIT: MacBoero beat me to it... :{

I know you are not asking for high-bypass turbofans, but I find this video pretty spectacular:

YouTube - GE90-115B Gas Turbine Jet Engine Testing & Evaluation (http://www.youtube.com/watch?v=5xlObdXF8VE)

Given the 4.5 ton/minute total water ingestion they've tested, one could use the 9:1 bypass ratio and the turbine stages still ingest 400 liters (106 gallons) of water per minute!
I'm sure you cannot compare that to your turboshaft engine, but it gives you an idea.

[Fareastdriver]

I did an experiment on a Whirlwind with some Westland people in Singapore researching as to why we were having engine stalls. Water ingestation was suspected so we ran a Whirlwind with the intake door off and a fire engine's water cannon going full blast into the intake. It stopped eventually but it was one hell of a fight. It certainly proved that mere rain wasn't going to stop it.

[heliduck]

Fareastdriver - Now that's what I call a compressor wash!!!

[BlenderPilot]

I heard of an accident somewhere I think it was Turkey, there is a fountain just like the big on on Geneva, any way, a Puma helicopter flew thru it or at least the water that was coming down and had a dual engine failure.

Also here in Mexico we had a 212 accident where the helicopter hit a wire, and it eventually crashed into a ditch, on of the PT6 engines kept running, even after the firemen came and got their high pressure water hose directly pointed at the engine, they put almost 5 minutes of high pressure water into the wildly spinning turbine before it quit, no one is sure if it was due to the water though.

[Jim Dean]

A wasp or scout pilot in europe somewhere back in the 70's is reputed to have hovered next to a large irrigation sprayer in order to wash the aircraft and had a flameout!! I'm not sure as to the veracity but it sounds good anyway:ok:

[Brian Abraham]

Something I've often wondered about. Always considered the 212/412 OK with the inertial separators but wondered about the 76 at times when driving through heavy rain. Has happened to fixed wing and in particular remember it being the official finding of the crash of a Metro. There was also the famous incident where a 737 had both flame out in rain and dead sticked on a levee near New Orleans (without damage).

Edited to add: You may find the following paper of interest - 32Mb download.
http://ftp.rta.nato.int/public//PubFullText/AGARD/AR/AGARD-AR-332/AGARDAR332.pdf

[floatsarmed]

Thanks for the replies guys. :ok:

Those big high bypass plank engines are impressive bits of kit.

However, I also wonder about the S76 at times with the inlet being so open and no bypass like the big jets.

I can appreciate that they do perform well as it's not something you hear about too often.

Hope all is well in Sale Brian.

Cheers
Floats'

[unstable load]

Any of the high time S61 and Puma guys got anything to contribute from the North Sea or Tropics? Those intakes are direct to atmosphere unlike the 76 with a bit of a dogleg in it.

[Shawn Coyle]

Not strictly on topic, but sort of relevant...

Don't get any water in the fuel. Investigated an Alouette accident in Romania many years ago where the helicopter was parked on a nose down slope of about 5-6°. Fuel sample taken in the morning showed no water, but failed to consider that the drain wasn't at the bottom anymore with the pitch attitude.
Helicopter lifted off (nose down with 7 people on board, very forward CG), accelerated (nose down), climbed (nose down) cruised (nose down) and then when they started to descend and decelerate (nose up), the water moved to the back of the tank where the fuel intake to the engine was, and poof - out went the fire.
Estimated it took less than a half cup of water to put out the fire. And the fixed shaft engine didn't have an automatic relight and would have taken several thousand feet to get started normally.

[griffothefog]

Wow, you can get 7 people in an Allouette??? Genuine surprise by the way Shawn :ok:

[FH1100 Pilot]

Uhh...here? (http://www.airpic.net/2007/REPORTAGES/faq_photo/Les%20bases%20de%20la%20photographie%20d'aviation_files/img_06.jpg)

[DennisK]

Yes ... 'tis important that we can use this forum to promulgate previous experience. Off topic again but forgive me ... go back to 1973 when I tasked a pilot to deliver a humble Enstrom 28A from Shoreham to its new owner. (G-BBPO no less!)

PIC ran into weather and sensibly elected to land at a convenient hotel but on a sharp right to left down slope. Overnight heavy and continuous rain ... strong winds.

Early morning pilot was seen to drain all three drain points. Climbing out the engine failed at 100 feet with the heli suffering skid and T/R damage in the resultant auto landing, albeit remaining upright.

The Enstrom was a newish type to the UK in the early 1970s so the AIB (as it was then) got involved. Engine removed but ran normally.

As I was involved in getting the CAA PT certification I needed to do some research so I rigged up the fuel tank for some testing. First we discovered a damaged filler cap seal on the accident helicopter. Also discovered that at an 8 degree slope, the depression that surrounds the filler cap will collect water, but which doesn't quite reach the fuel filler neck. But we also discovered that with an airflow across the filler, water could get blown/possibly sucked into the tank. Probably one drop a minute. But a constant water supply and twelve hours later !

Next we learned that at the same 8 degree side slope, the centrally located fuel pick up point in the tank allowed a bare half an inch of space to inboard where displaced water could settle clear of the fuel pick up point.

Then similar to Shawn Coyle's incident, start up and run up engine was normal, lift off with left skid low still normal until the heli levelled at which point water moves inboard and enters the pick up point and engine supply pipe.

The Enstrom fibre glass tank was promptly factory modified, but I relate this yarn just to highlight how many nasty little items await we flyers. The circulation of knowledge and experience counts for everything in safety, hence the success of Gary Spender's 'informal safety evenings'.

A horrid personal example. Had I known in 2000 that the Hughes 269c type had a history of part no 234 pylon cluster cracking failures, (eight in all) ... I would not have purchased the type for my school OR if I had, I would have carried out the factory approved cluster replacement. As it was I knew nothing of the previous failures and as many of you will know my son lost his life as a result following a mid-air break up.

See many of you at Redhill Nov 26th.

Regards to all,

Dennis Kenyon.

f

[Fareastdriver]

There is no such thing as heavy rain in the North Sea compared with the tropics. Sometimes I have been unable to avoid walls of water in China but there has been no reaction from the engines and the chip baskets would break it up anyway. I believe, but unable to confirm, that a Bristow 330J had an engine failure in heavy rain in Brunei and they replaced the the snow dams as a precaution. During my time in Belize with the 330C Puma with open intakes the biggest hazard was rain stripping off the tape on the rotor blade leading edge.

[ShyTorque]

The story about the British AAC heli pilot flaming out his aircraft's engine by flying under an irrigation spray is true. I remember reading the accident report. Might have been a Gazelle though.

There was some concern with the open intakes of the RAF Pumas suffering from a sudden ingestion of a slug of accumulated snow/slush. Falling or blown snow used to build up on the front engine moulded cowling, between the two engine intake ducts from where it could then slip off sideways and down an engine.

Pre Polyvalent Intake Protection System, (PIPS) equipped airframes were given a reduced clearance in falling or blowing snow conditions (400 metres IIRC). An interim mod before PIPS were fitted was to fit wide angle rear view mirrors, externally above and forward of each pilot's position so we could check for snow accumulation in flight. Great idea. We used to arrange them so the whole side of the airframe could also be seen. Very useful, especially to confirm for possible signs of fire or leaks etc. However, once the PIPS came along the silly sods removed the mirrors despite our mere aircrew protests, a retrograde step if ever there was one.

There was concern about heavy rain in Belize during my times there in the late 70s to mid 80s. No-one could say how much water it would take to flame out an engine. The problem came to a head following an incident where a design fault (a single diode failure) on the starter panel could cause BOTH engines to be switched off by resetting a single start switch! So we were banned from attempting an in-flight restart in the event of an engine failure. As Fareastdriver will no doubt confirm, single engine flight was "interesting" in Belize at heavy MAUW. Having said that, I never heard of an actual engine failure on an RAF's Turmo 3C4 until someone who will remain nameless ran out of fuel in Portugal. Industrial engines, very solid pieces of engineering. :)

[Shawn Coyle]

There were also many variations of the MD500 which did not have a snow deflector 'approved' for several years.
Snow would accumulate on the roof (even with the rotors turning), and after liftoff, would slide back and into the engine intake and put out the fire. Good reason to have auto-relight available and switched to the auto-relight position.
Wet snow is a very good fire extinguisher in sufficient quantity.

[John Eacott]

Before the Sea King HAS1 grew its barn doors, the intake was prone to all sorts of inputs, include heaps of salt build up on the IGV's.

Prolonged hovering in low winds overwater would tend to reduce vis with salt on the screens, so I arranged for a bucket of fresh water to clean the windows during hot turnrounds on Ark. Worked fine for a week, until one enthusiastic lad flung the water right over the screens, and straight into the No 1 engine intake: 15 litres was enough to put the flame out but leave the windscreen untouched :ooh:

I was advised to put up with dirty screens for the rest of the exercise :p

[OffshoreHeli]

yes I believe it was a Gazelle had the flame out. He was trying to wash the mud from the aicraft after being in the field for a week or so. Doh!

[SASless]

During Vietnam years we were to wash our Chinook engines at the end of every flying day so as to keep the "Bleed Bands" clean. The procedure was to pull up to the water bowser, crew chief or gunner would fill a bucket, then with great care and caution....(think door gunner here)....fling ladle fulls of the clean water into the engine intake as we used the Emergency engine trim system to pull the N1 into the range where the bleed bands would open.

In time...after long days of flying....ten plus hours....the procedure was reduced to chucking near bucketfuls into the intake. The engines bogged down a bit but never died on the spot. Perhaps hours later while in flight maybe...but not on the hard stand.

The alternative method during rainy season morphed into finding a pouring down column of rain, enter autorotation, pull the N1's down into the correct range....repeat three times while in descent...then carry on with the day's business.

[nodrama]

Might not answer your question exactly because there are alot of variables, but I can give you an example to gauge an estimate on:

Our operation water rinses it's engines, 'hot', on a light twin helicopter. The procedure involves delivering about 8 ltrs of water directly into the compressor, over 2 minutes, so at a rate of 0.07 ltrs/ sec. This is the recommended delivery rate to avoid flame-outs during the rinses. Assume the people that came up with that figure are being cautious, so it could most probably manage 0.1 ltr per second. That's 6 ltrs a minute, which is alot of rain.

[heliduck]

I need some help from the Sydney boys here as I'm "Google" eyed with no results. Quite a few years ago a Police or Rescue AS365(I think) was hovering over a rocky ledge near Sydney. A wave came in & as it crashed into the rocks the resultant spray caused a flameout in one engine. I believe the pilot kept it upright & settled onto a rock ledge. Can anyone help with the details or a link?

[John Eacott]

Many military airfields these days have bird baths for washing aircraft after flight, mostly to rinse off salt deposits:

http://www.eacott.com.au/gallery/d/2406-1/wash2.jpg

Operating from NAS Nowra on bushfires, the tower were good enough to turn on their birdbath for us after a day in the smoke and embers: the view from inside the BK117:

http://www.eacott.com.au/gallery/d/2410-1/Bird+bath+Nowra.jpg


Certainly effective, and it didn't put out the engines ;)