Radiator/cowling flaps

[horseback]

I believe that in most cases, the main limiting factor for water injection for the R-2800 was the water available in the water tank. Whether the tank's volume was determined by space or the amount of abuse the engine could safely take in a single flight, I cannot say, but I do know that if you went to water injection/War Emergency Power, you were supposed to inform the aircraft's crew chief, who had to make several checks and tests before clearing the aircraft for its next flight (and often would say unflattering things about you if your reasons for the extra work seemed insufficient).

cheers

horseback

[bladeracer]

Originally Posted by horseback

I believe that in most cases, the main limiting factor for water injection for the R-2800 was the water available in the water tank. Whether the tank's volume was determined by space or the amount of abuse the engine could safely take in a single flight, I cannot say, but I do know that if you went to water injection/War Emergency Power, you were supposed to inform the aircraft's crew chief, who had to make several checks and tests before clearing the aircraft for its next flight (and often would say unflattering things about you if your reasons for the extra work seemed insufficient).

cheers

horseback

That's one reason I asked, some aircraft carry enough boost additive to exceed the specified usage limit so conceivably could use it several times without exceeding the limit in any single episode.
I think generally there were tells built in so the crew would know immediately whether WEP had been used, though not necessarily for how long.
In First Light, Geoffrey Wellum didn't seem particularly worried about WEP usage at all.

[horseback]

In First Light, Geoffrey Wellum didn't seem particularly worried about WEP usage at all.

As I recall, First Light was about the Battle of Britain and the early part of the war; I don't think that water injection -type boost was available in Allied fighters until mid-war. Water injection for the R-2800 in P-47s, Corsairs and Hellcats was introduced in combat around the winter of 43/44. I'm not aware that it was ever available for Allison or early single staged Merlin powered fighters.

In the early part of the war, I believe that War Emergency Power was simply that last little bit of throttle where the engine was asked for its maximum output where damaging it was much more likely. Taking a high powered engine to its full limits increases wear & tear tremendously, and one of the big factors in that wear & tear was the increased heat and friction, which could cause the engine to fail sooner (or right away, if it was just about due for overhaul). Water or methanol injection cooled the engine that critical extra bit and allowed you to pull that extra few horsepower when you needed them.

cheers

horseback

[bladeracer]

Originally Posted by horseback

As I recall, First Light was about the Battle of Britain and the early part of the war; I don't think that water injection -type boost was available in Allied fighters until mid-war. Water injection for the R-2800 in P-47s, Corsairs and Hellcats was introduced in combat around the winter of 43/44. I'm not aware that it was ever available for Allison or early single staged Merlin powered fighters.

In the early part of the war, I believe that War Emergency Power was simply that last little bit of throttle where the engine was asked for its maximum output where damaging it was much more likely. Taking a high powered engine to its full limits increases wear & tear tremendously, and one of the big factors in that wear & tear was the increased heat and friction, which could cause the engine to fail sooner (or right away, if it was just about due for overhaul). Water or methanol injection cooled the engine that critical extra bit and allowed you to pull that extra few horsepower when you needed them.

cheers

horseback

Yes, First Light is mainly BoB and Malta. Yes, WEP was merely "War Emergency Power" setting of the throttle. I never suggested additive boost was available for WEP during the early war.

I race motorcycles so I am aware of the significant increase in wear and fatigue from even slight increases in power settings.

[horseback]

I race motorcycles so I am aware of the significant increase in wear and fatigue from even slight increases in power settings.

Then you must have used a few tricks to get more power from the engine, possibly replacing the stock throttle system with one that lets you use more of the engine's potential power. Most cars and bikes rated for street use do not use the full throttle capacity of their engines, because the engineers know that the engine will wear out sooner (and the normal user will never need to accelerate at the full throttle rate, much less travel at the speeds it would allow) and use much more fuel. And of course there's that liability thing here in the States.

Of course, we have a much better understanding of metallurgy, coolants and lubricants today than we did in 1939-45.

Similarly, the high performance engines that powered WWII aircraft were limited by the engineers in various ways; how much they were limited depended upon the quality of the fuel and lubricants, the expected atmospheric conditions, including the quality of the cooling systems (as I recall, most early war Soviet fighters lacked glycol cooling, which severely limited both the power of their inline engines and their time between overhaul).

All of this is the long way of saying that the limits on WEP use were very specific to a given engine and aircraft, and in some cases changed with better manufacturing techniques as the wartime workforce learned on the job. Consult your real life aircraft's manual for general guidance, and experiment a little on your own to see if the Il-2 '46 FM matches it (many aircraft do).

cheers

horseback

[bladeracer]

Originally Posted by horseback

Then you must have used a few tricks to get more power from the engine, possibly replacing the stock throttle system with one that lets you use more of the engine's potential power. Most cars and bikes rated for street use do not use the full throttle capacity of their engines, because the engineers know that the engine will wear out sooner (and the normal user will never need to accelerate at the full throttle rate, much less travel at the speeds it would allow) and use much more fuel. And of course there's that liability thing here in the States.

Of course, we have a much better understanding of metallurgy, coolants and lubricants today than we did in 1939-45.

Similarly, the high performance engines that powered WWII aircraft were limited by the engineers in various ways; how much they were limited depended upon the quality of the fuel and lubricants, the expected atmospheric conditions, including the quality of the cooling systems (as I recall, most early war Soviet fighters lacked glycol cooling, which severely limited both the power of their inline engines and their time between overhaul).

All of this is the long way of saying that the limits on WEP use were very specific to a given engine and aircraft, and in some cases changed with better manufacturing techniques as the wartime workforce learned on the job. Consult your real life aircraft's manual for general guidance, and experiment a little on your own to see if the Il-2 '46 FM matches it (many aircraft do).

cheers

horseback

Yes, I know what WEP means (I'm sure most people playing these games do), my question was _how are the limits specified_, which I don't ever recall seeing mentioned in the aircraft manuals. Where it states a usage limit of "five minutes maximum" it doesn't generally state that "you must not use it again until after the engine has been inspected", for example.
Yes, I could indeed experiment in the game. but this still doesn't answer my question since I'm specifically asking about real world limitations, and specifically, how those limitations are measured. "Five minutes" is meaningless unless it relates to a longer term, such as "five minutes maximum until engine is inspected, regardless of whether it is five minutes continuous or accrued time", or "five minutes maximum until the cylinder head temperature has been reduced to below 100C for a minimum of twenty minutes". I don't see how I can ask it any more clearly than this.