GregP
Major
Right, we have discussed this before. It's interesting and important. I make the distinction between WEP vs overboost, because WEP settings are usually approved as 'safe' for the engine, based on testing. Of course, that doesn't mean it was 100% safe. Engines broke or even caught fire blew up fairly routinely in military service. They were basically racing engines, very veyr powerful ones at the limits of the technology of the day, and were as temperamental as the engines on a racetrack.
Overboost means the pilot took the boost setting past what was recommended / allowed emergency maximum. You are right that a 1944 WEP setting was not the 1942 official setting. The 1944 setting came from the overboosting routinely being done by P-40 pilots in the Pacific and the Mediterranean. Not sure if it was also done by P-39 pilots, (I assume it was), and I know the P-38 had specific and unique issues. As we know via the famous Allison memo, Allison and the War Department and the units basically worked out what was the 'best practice', though of course if the pilot was fighting, or running, for his life, guidelines may likely go right out the window.
The original maximum boost settings from the early manuals was too low, given the speed and performance of enemy aircraft, and people who stuck to those guidelines often paid with their life. They appear to have gone right past it within weeks or even days of combat in many cases. Pilots from the Australian 75th Sqn in New Guinea described boosting at 70" in their very first air battles with Zeros. In the MTO Theater, also Australian and then some British and South African units were doing this with their P-40D Kittyhawks after about 5-6 weeks.
I believe over time, the maximum boost settings (WEP) were used routinely while the overboost (beyond WEP) ratings were used less often (only in true life or death emergencies), except in cases like with the British recon Mustangs where the unit had carefully worked out how far they could push things in specific conditions.
The big scorch mark and often leaking oil also gave this away I think
And at a bit higher altitude when coming out of a dive, apparently
Seeing as takeoff power was routinely used ... for takeoff, especially when carrying bombs and / or external fuel tanks, I would think the wire would be set at least for 51" or whatever takeoff power was. Otherwise you aren't going to know much about "overboost" / WEP because the wire is already going to be broken before the plane is 100' off the ground.
Engines did NOT break or catch fire frequently. They were and ARE VERY reliable.
I worked the Planes of Fame airshow for 10 years and we flew an average of 50 sorties per day for three days at each airshow. That's 1,500 sorties over 10 years with an average of about 30 WWII aircraft per show. In all that time we had 5 takeoff aborts after engine start. 1 was a flat tire, 1 was a Corsair that couldn't get a wing to unfold (hydraulic valve), 1 was a rough-running R-2800 that was traced to several fouled spark plugs and he aborted at about 50 knots (flew later, after changing the plugs), 1 was an R-1820 that backfired on short final approach and blew out a case gasket (it still taxied in and parked ... pilot error with the mixture), and one was aircraft-related and not a danger to flight ot aircraft, but safe is better than sorry in an airshow warbird.
That's two engine-related failures in 1,500 sorties some 55 - 65 years after these were active military engines. That's 0.13% engine-related issues that happened over 50 years after these were out of service. I'm not saying the military had that performance during wartime, but the engines were VERY reliable. The TBOs were NOT set due to engines that were running badly; they were set so that over 99.5% of all engines being sent it for overhaul could be overhauled and not replaced. That is, the TBO was set so the engine cases could be reused successfully when it came time for overhaul, not for operational issues.
We had zero engine fires. The military had a few, but not many. That's why there are guys with fire extinguishers around every radial at startup. Usually a so-called fire is oil that caught fire due to hot exhaust and it burns out rapidly, usually 3 - 5 seconds, before anyone can even get the extinguisher ready for use. Not always, mind you, but most of the time. I am not working on being around flying warbirds up and close for 18+ years in a row, and I have yet to encounter an engine fire. Not to say they don't happen, just not very often.
