To climb or not to climb

[Thorlifter]

The way my little pee brain works is all aircraft should be able to climb at their best ROC at low altitudes where the air is more dense and that ROC will taper off as the altitude increases and the air gets thinner.

So, just as an example, why do some planes do their best climbing between 10k-and 20k feet?

 

[wuzak]

It also depends on engine power, and many WW2 aircraft had their peak power figures in that altitude range.

Below what the British would call the Full Throttle Height (Americans the Critical Altitude) the engine intake is throttled so the maximum power will not be produced.

In theory turbocharged aircraft should have the maximum climb at sea level. For the most part the P-47 and P-38 seem to, but there are one or two reports on WWII Aircraft Performance which don't agree.

 

[wuzak]

And that may be related to the propeller.

A couple of P-38 performance curves.

http://www.wwiiaircraftperformance.org/p-38/P-38F-chart-1400.jpg

http://www.wwiiaircraftperformance.org/p-38/P-38F-G_chart_Report-2338-1400.jpg

P-47:
http://www.wwiiaircraftperformance.org/p-47/p-47n-republic-wep.jpg

http://www.wwiiaircraftperformance.org/p-47/p-47d-75035-fig2.jpg