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drose01
04-21-2007, 07:20 PM
Are there any acceleration benchmarks for WW2 aircraft in level flight?

Otherwise, is rate of climb a decent approximation of aircraft acceleration performance?

drose01
04-21-2007, 07:20 PM
Are there any acceleration benchmarks for WW2 aircraft in level flight?

Otherwise, is rate of climb a decent approximation of aircraft acceleration performance?

JG14_Josf
04-21-2007, 07:53 PM
Rate of climb is an excellent measure of performance under climbing conditions and the plane with the higher rate of climb will have the higher acceleration in level flight at that speed.

What is not true is to assume that rate of climb is a universal measure of acceleration at all speeds and all flying conditions such as unloaded dive acceleration or unloaded vertical zoom climb deceleration.

Acceleration performance didn't become a standard documented measure of fighter performance until the development of John Boyd's energy theory where acceleration capability is measured as excess power or Ps.

Some very good information on excess power has been posted on some current thread in this forum. Viper posted a good link to a well done presentation on excess power. I can repost it if you like.

I don't think you will find much WWII documentation on absolute acceleration performance (benchmark?) for any WWII aircraft. What is available however is side by side test results whereby WWII pilots tested relative acceleration performance. I can post many examples of this kind of relative measure of acceleration performance.

We can also fill this thread with personal attacks. Who will add the first one?

Kettenhude has recently developed another angle of view which also identifies specific measures of acceleration performance according to specific flight conditions. This must be understood in my opinion. There is only one way to know how well an aircraft will accelerate during a specific condition of flight where the power available is determined by that specific flight condition and the power required is determined by that specific flight condition. In other words there isn't an accurate way of quantifying acceleration according to some simple measure such as: climb rate.

Example:

One plane such as the Spitfire with 25 pounds boost will have a very light (relatively speaking) airframe, a large wing area, and a very good power to weight ratio compared to a P-47; therefore – the Spitfire has all the necessary physical properties to out climb the P-47. On the other hand the Spitfire cannot go as fast in level flight and therefore the advantage of acceleration cannot continue to speeds where the P-47 is faster. The most obvious flight condition whereby the advantage in climb is not an acceleration advantage is during ballistic flight such as a vertical dive (or zoom climb) where, in the case of the P-47 versus Spitfire, there is no contest. The P-47 can out dive (accelerate straight down) at a faster rate than the Spitfire.

If the idea is to measure ONLY the level flight acceleration performance between two aircraft or to benchmark ONLY the level flight acceleration performance, then, there are modern methods to accomplish that task accurately. I can link how that is done too. The WWII era may have had similar methods; however – that fact remains unknown to me. I think the factories didn't measure it and the combat pilots didn't seem to care about benchmarks so much as how well their planes stacked up against the planes they were trying to shoot down.

I can offer a classic example of one such TEST done by Helmut Lipfert in his book. If anyone else can find Benchmarks for acceleration on WWII fighter planes then I'm also interested in that information.