Internal Fire Museum of Power

Many years ago when producing cockpit emergency manuals for Dan-Air, I noticed that part of the section referred to stoping the injection of water into the engines.

At the time I asked one of the pilots who flew the planes what the injection of water was for. He may have told me about it back then, but, I cannot remember now.

There must be among the brilliant minds on I.F. those who know the reason for this!

I cannot remember which of the aircraft this concerned.

Any thoughts?

John

I recall seeing retired Dan-Air planes at Lasham c1967 - Lasham was or had been their maintainance base I think. Those I remember were Yorks with perhaps the odd Tudor and DC3. Do any of those sound familiar or is that too early?

regards
Roland

No, they were jets, possible HS146 or BAC111

I think was used for reducing air temp and therefore increasing flow to boost power on take off.

P

Quite correct.

There is a (completely erroneous) old wives tale about the water cracking into hydrogen and oxygen, but the truth is; the water injection cools the induction air making it denser so that more can be crammed in.

You might be interested to know that until a fortnight ago, when our glorious leaders scrapped them, the RR Pegasus in the Harrier did exactly the same thing. In the case of the Harrier, however, the water injection (50 gallons of de-min) is used to spray over the turbine blades to cool them, so that the engine can be over-temp'ed to produce more power. In the case of the GR7/9, up to 107%, at which point the turbine blades would melt and disappear out of the exhaust if it wasn't for the water!

Martin

Water injection was an option on the Saab 99 Turbo S and is still around as a specialist aftermarket add-on for those guys who tune their engines within a degree of their lives. Anyone with a hopper cooled engine knows that vapourising takes a lot of heat, (compare the size of radiator needed for a Lister D instead of a hopper). It's also thought that if you can get the water mist into the cylinder, that the cylinder will run cooler and you're effectively using flash steam to get extra pressure/power. (expansion of water to steam is much greater than warm air to hot air).

I've been very tempted to turn my turbo D into a partial steam engine!

John

My father flew BAC111, he's away at the moment, I'll ask him when he's back. Water spray is also used on turbo charged cars, in particular the Subaru Impreza STI, a mist of water is sprayed over the intercooler to further bring down the intake temp, it's controlled by the ECU.

Chris

I have a full manual for the BAC 1 Eleven in the office

P

I have a Lister M with factory fitted water injection.

Martin P

Of course, and my FMZ has it too... I'd quite forgotten about that!

Martin.

At one time, Triple C and no doubt other mags advertised Water Injection kits for (boy) racers which were basically modified windscreen washer pumps and bottles! Basically to provide charge cooling, as Paul said, but I seem to recall they also promised to steam-clean carbon deposits from the combustion chamber.

The instructions for the prewar air-cooled Wisconsin engines contain instructions for water de-coking. It works too.

ttfn
Roland