Water Injection

[ramsrc]

I have a couple of questions that I hope someone will be able to answer regarding water injection systems as used on Engines such as the Rolls Royce Spey and P+W JT3

I understand this is in order to increase thrust for take off and is achieved by injecting water into the compressor inlet.

I am curious as to how much water is required to produce a significant increase in thrust. For example, is an increase in thrust noticeable simply when flying through cloud which presumably would have a similar effect.

Secondly is this technique still used? and finally is it necessary to take any precautions to prevent the water in the injection system from freezing?

[411A]

Water injection used on the B707-100 series powered with JT3C-6 engines used 400 gallons of de-mineralized water in 2.5 minutes at takeoff power, which ran the tank dry...so no problem with freezing at altitude. This water injection supplied an extra 2000 pounds of thrust per engine, as I recall...been a long time ago. These aeroplanes (some anyway) were later fitted with JT3D-3B engines (fan) which eliminated the need for water. Also MUCH quieter...for the airport neighbors anyway.

[Slick]

RR Spey used demineralized water and this was injected directly into the combustion chamber by a separate tube but part of the fuel spray nozzle 10 each eng -512-14DW. DW = developed wet.

On the 500 series Bac 1-11 a rear water tank could hold about 500 kg of water. Freezing was a problem and you had tables to use if you wanted to tank water, time in cruise temp at altitude, water temp on loading were considered. Water was a bit of a pain to load downroute so tanking was prefered. If you could not tank then you had to load barrels of water into the hold and pump it into the tank downroute with a portable pump/motor also located in the hold. This pump was stored in a box, and you would drag the thing out and plug the hose into the rear of the aircraft. The plug for the pump was inserted into a socket in the rear freight hold.

As far as perf went you also needed to use tables to determine the amount of water you needed to enable you to climb to 400ft (min flap retract). Again based on temps, airfield alt, and aircraft weight.

Best Rgds

[pigboat]

The water used in the Dart was actually a mix of water and methanol alcohol, typically 60% - 40% water to meth. It was used to either restore power - as with the Dart 529, or boost power - as with the Dart 532.
The F-27 had two forty US gallon tanks, one in each aft nacelle, and the FH-227 had one tank, in the left nacelle. Depending on the ASC, the G1 had either two wing tanks, one outboard of each fuel tank, or one tank located in each wing fillet.

[Checkboard]

You will find more informaiton on this topic on the Water Injection (http://www.pprune.org/cgibin/ultimatebb.cgi?ubb=get_topic&f=3&t=001340&p=) thread.

[ramsrc]

Many thanks everyone.

[Pengineer]

I remember sitting in on engine ground runs on the BAC1-11 many years ago, when the water injection went in the effect was quite dramatic. The A/C lunged as if it were trying to jump the chocks.
http://www.stopstart.fsnet.co.uk/Gif/FSFred1.gif
Pengineer

[nobby478]

As an engineering base for some of the few remaining 1-11's in the UK i found the comments above very interesting. one of the offshoots from the "demin water" era is that through my carreer with bcal, BIA, Dan Air BWA we must have provided the whole of europe , half of africa and a good deal of russia with a free supply of empty demin barrels. I would be interested to hear if any of these pop up in any unusual places. I will re-visit with interest

[GotTheTshirt]

The BAC 1-11 dumped the unused water after T/O to avoid the freezing problem :) ;)

[ 09 November 2001: Message edited by: GotTheTshirt ]

[Willit Run]

Well, on the DC-6, we had water injection on the R-2800's, which gave us an added 450 HP per engine, by de-riching the fuel mixture,and enableing us to use 59 1/2 inches of manifold pressure to give us a mixture that produced more power. Worked good, but the pucker factor on take off was quite something about all those pistons trying to escape from the cowling!! and sometimes they did!!!!!

Water injection? what the hell is that?

[pigboat]

Yeh Peter, the Convair 340's and Martin 404's had the same thing. Called it ADI. Stood for Anti Detonation Injection, I think. Didja hear the one about "double clutch that mother******" Martin 404 in GSO? :D

[Gary Halliday]

When using water meth as an ADI system, usually 60/40, this used to have 1% fish oil added as a lubricant - was this also present in the 45/55 mixes used in the RR turboprop engines?.

Gaz

[411A]

Yeh Peter, 59.5 inches MP and 243 BMEP...those were the days. The water regulator "usually" worked OK...
Most operators today use dry takeoffs due to 100LL fuel, I believe.

And...no oil added to the water methanol for Dart powered aeroplanes.

[big pistons forever]

CONAIR still uses ADI for all loaded takeoffs on its DC6's. The extra power allows about 6000 lb higher gross weight. Watching the water pressure lights on TO is of conciderable importance as even one full power TO with out water will severely damage the engine. Still and all the late model R2800 CB3 and CB16 engines are marvelous pieces of machinery. Nothing beats the growl of 4 of them at full song :)

[18-Wheeler]

BIK_116.80 - Out of having no choice on one trip, I managed to get six take-offs out of the water/meth tanks. Suffice to say I turned it off pretty quickly after each take-off ... ;)

[moggie]

The Hawker (BAe) Harrier also uses de-mineralised water injection, onto the turbine, to gain extra thrust for take-off and vertical landing. Very effective, too, although the GR3 only had 90 seconds worth available per flight.

It cooled the turbine, allowing higher RPM and fuel flow (and therefore more power) for the same stress on the back end of the engine.

[18-Wheeler]

Crickey! You know me? :)
Nah, it's too long a story to tell properly, but it's pretty funny so I might knock it up off line and post it here for a laugh later.
No, he wasn't arrested, but then again he was never a problem after that. :)

[Gspot]

From what I remember the water on the BAC 1-11 only served to allow you to make even more noise and give you a warm fuzzy feeling that you were actually developing more brute power. Oh God I remember those water takoffs from Sicily with 114 pax with their buckets and spades trying to get to Luton, scraping by FL 200 by about Pisa.

Tell the kids of today that and they'll never believe ya. :D :D

[Willit Run]

I had no idea there were that many piston pounding propheads out there in cyberspace who remembered what fish oil and water pressure lights were all about. Boy, haven't we come a long way! Hey, is that a double shorted secondary???? shut it down!

[big pistons forever]

Peter Ball

I agree. There are still plenty of folks out there who appreciate airplanes built when men were men and engines were round ! My airline frend thought I was nuts driving a greasy six when I could be flying some glass cockpit wonderplane. But I have glass cockpit time said I ... I have spent many hours peering at the engine analyser trying to figure out what the squigly lines meant :D :D

[Elliot Moose]

The darts on the 748 use about 5gal/side/takeoff (of the water/meth) if it is used "conservatively". That is run "wet" until you clear the trees and then pull the power back to about 14500rpm to cut out the system. This leaves "wet" power still available if a fan quits.
Each engine has a tank in the aft wing root (a rubber tank which is a b!tch to change)which will hold about 30gal. Thus you only get 5 takeoffs max out of a fill-up (10 gal is min for dispatch). The water burns the hell out of the engines (high TGT's and torque) and costs a fortune, so many "bush" operators don't actually start burning it until well after the book says to. ;)
It's really only used for well loaded takeoffs anyways.
On a side note there was the case of a 748 that got a full load of water/meth just before departing Churchill Man. quite a few years ago. The crew switched the water on to demonstrate the performance boost to a jumpseater or somesuch and blasted off. They got a huge boost and unbelievable performance. Through a couple hundred feet altitude both engines flamed out and they managed to safely land on the (fortunately) frozen river. It later turned out that an old water/meth drum had been filled with a witch's brew of waste oil/thinners/fuel, and the contents of that drum ended up in the tanks. :eek:
What a ride! They ended up towing the plane back up onto the airport on its own wheels and I believe it's still flying today.

[xbxex]

Some extra info on AWI from the SA227-BC ( Metro III) AFM.
Engine: Garrett TPE331-12UA

ENGINE OPERATION WITH CONTINUOUS ALCOHOL-WATER INJECTION (CAWI)

The CAWI system may not be operated if the AWI fluid has been exposed to ambient temperatures below -24'C within the preceding one hour.

Minimum OAT for AWI operation......-6'C

Mixture Composition % of volume:
Methanol 40%, Water 60%

The approximate freezing point of the AWI fluid is -31'C (-24'F).

[pigboat]

The same thing happened to a 748 on Anticosti Island, on a dirt strip at a hunting camp. Loaded both W/M tanks with JP4. They never even got airborne before the right engine cooked. Everybody got out ok, but the whisperliner was a writeoff.
The US military, the Navy I think, used to operate the G1. One aircraft had been operating wet most every takeoff all summer long. Their procedure was to call for the water off right after the gear came up. On one dry takeoff that autumn, the F/O selected gear up and hit the W/M at 15,000 RPM. They got the aircraft around and back on the ground, but they had to change everything from the firewalls forward.
Something similar happened to a Martin 404 in GSO. A famous singer bought one offa Southern Airways, and he had his own pilots on it. They were getting about 20 hours on their engines and maintenance couldn't figure out why. One day they were in GSO on a layover and a Piedmont flight was there, so they asked the Captain to give them some airwork. They were motoring down the runway with the power set, when the Captain looked over at the F/O and told him to "double clutch that mother******." The F/O reached up and hit the ADI switches. Solved the premature removal problem right there.

[ 13 November 2001: Message edited by: pigboat ]

[PAXboy]

I understand that the BAe Jetsream 41 has a water/meth facility. If memory serves, they use the Garrett.

The pilot who explained about this process said that the bean counters don't like them to use it unless they REALLY have to. But then, the same bean counters also asked f/c to try and turn off the wing tip 'conspics' lights as soon as poosible after departure ... as the bulbs are expensive!! Not sure how many of these bulbs you have to save before you equal the cost of a J41 involved in a mid-air because it wasn't visible?

[ 13 November 2001: Message edited by: PAXboy ]

[ramsrc]

Elliot Moose

The HS-748 was a great aircraft. I remember flying into and out of Bern-Belp, Switzerland on a Dan-Air 748.

I am not sure if Water Injection on the take-offs, but in those days the runway was comparitively short and compared to other airports it seemed to be real seat-of-the-pants stuff.

I have not been back for years so I expect it has changed a great deal since then. Maybe even the "terminal" shed has gone!

[Elliot Moose]

ramsrc
Whaddaya mean WAS!? There's still a whole pile of them flying here in the great white north. Most have been well modified. Almost all have some form of supplemental heat (designed for Britain where it's not too hot and not too cold--we get both extremes), but some have a lot more. Many are carrying freight, and as such have a lot of the familiar furnishings removed--including pressurization (those superchargers are heavy) windows, baggage doors, and in a few cases a 9ft hole has been cut in the side of an unpressurized beast and a roller floor installed to accomodate pallets and large reight. The most modded one I flew was a fuel tanker conversion. It had been depressurized, had all but the forward freight door removed, windows sheeted over and all but the centre floorboards removed. The cockpit was sealed up pretty well and double insulated. 200V AC heat was installed as well as a bleed air heat system. A King silver crown stack (much like a Cessna caravan or King Air) was installed in the main panel and all the engine instruments squished over to accomodate it. They also installed a 10h.p. honda engine as an APU which had a hydraulic pump and generator installed as accessories. The hydraulics were used to operate fuel pumps down in the belly. Ten 250gal tanks (US army surplus from a C5 Galaxy installation)are installed in the main fuselage and the outboard 15ft or so of wing tank is partitioned off and plumbed into the payload system. This allowed the aircraft to be landing weight limited instead of ZFW on short hauls. Loading and unloading was done by means of single point refuelling points located on the left lower fuselage forward and aft of the wing.
We were able to take a total load of 9250L of unleaded fuel on a short leg VFR(less red diesel or Jet B since they weigh more), which meant it was just a big flying fuel-air bomb. :eek:
Standard SAR procedure would be to find the biggest forest fire and work upwind until you find the crater. ;) It was hard dirty work, but the pay was great! :D
http://216.122.208.89/gallery/pictures/9.jpg

Here's an actual picture of the beast taking off with a load on about 4yrs ago in northern Ontario.

[ 14 November 2001: Message edited by: Elliot Moose ]

[ramsrc]

Elliot Moose
I stand corrected. The HS-748 is a great aircraft.

Unfortunately, Apart from the occasional Andover, it has been a while since I have seen one around here.

[FL310]

And there was this German BAC 1-11 with Jet Fuel in the tanks...it took off and the crew managed an emergency landing on a mototway near Hamburg....the female copilot of this flight died later unfortunately on a crash in bad weather hitting an antenna mast on short final operating a Citation.