Originally posted by K West
http://www.p47advocates.com/messages/531.html
Mr Brodys' book has more details and perhaps Widewing could shed some light on the details he knows about. AFAIK nothing major was done to the airframe or "drive train" - except just about all in theatre P-47's having or being retrofitted with later model props. It was just re-aligning, tweaking and adjusting what was already installed to perform far above factory/USAF specs, recommendations and limits.
Westy
Generally speaking, it was common for American mechanics to "tune" powerplants to obtaim greater than rated power. Back in the 1940s, America was a nation of mechanics. Nearly every male over 18 owned an automobile, and most did their own repairs. There was no such thing as a warranty back then. Furthermore, many of these young men were tuners and into "hotrod" building. By the mid 1930s, performance shops were becoming more common throughout the nation. This provided for a highly skilled mechanic base for the military.
Col. Cass Hough was responsible for 8th AF Aircraft maintenance. He understood that his mechanics would not settle for "stock" engine performance. So, in effect, he turned a blind eye to unauthorized field modifications. Likewise, factory tech reps from the various aircraft and engine manufacturers introduced modifications to enhance performance. However, the modifications were never authorized by the AAF, yet were generally done with the knowledge of the Hough's office, but never spoken of in any "official" manner. Typical of this was Republic's modified wastegate for the R-2800 engine. Standard wastegate springs were replaced by newly fabricated examples with a much higher spring rate. This kept the wastegates closed until much greater boost pressures could be obtained. Early efforts had some problems as the springs were not properly stress relieved and would sack out, actually causing a loss of power. Eventually, mechanics would take their arbor wound springs to the cooks, who baked then in their ovens at 450 degrees F for one hour. This relieved the stress and the springs maintained their rate and force. Indeed, it was an engineer in Col. Hough's office who suggested this. Hough estimated horsepower on the better tuned engines to approach 3,000 hp with water injection.
Other modifications included using auto body filler to fill gaps in the surface of the aircraft. Then, they were waxed to a high gloss.
many P-47s had their HF antenna posts removed or shortened. Many were fitted with fabricated whip antennas, of lower drag. Remember, speed wasn't the only goal. Increasing range was also a consideration, and Hough justified much of the unauthorized mods as fuel economy measures. No one in the 8th AF command interfered as long as results were positive.
When the P-47M arrived at the 56th, it suffered through much of the teething woes experienced with the early Jugs. Most pilots were content to fly their older aircraft because, in reality, they were just about as fast anyway.
My regards,
Widewing
