Throwing some light on rates of turn

[Crumpp]

All the data tables and graphs refere to merlin XX equipped aircraft.

The RAE's use of a single chart given the absence of any differientiation between power levels makes perfect sense with the Merlin XX predictions.

The Merlin XX was predicted to maintain similar power from sea level to 20,000 feet.

1020 Hp at Sea Level and 1075HP at 20000 feet:

http://www.enginehistory.org/members...a/Table-04.jpg

http://www.enginehistory.org/members...lysisR-R.shtml

[Holtzauge]

Originally Posted by Crumpp

The RAE's use of a single chart given the absence of any differientiation between power levels makes perfect sense with the Merlin XX predictions.

The Merlin XX was predicted to maintain similar power from sea level to 20,000 feet.

1020 Hp at Sea Level and 1075HP at 20000 feet:

http://www.enginehistory.org/members...a/Table-04.jpg

http://www.enginehistory.org/members...lysisR-R.shtml

So how does the Merlin XX data you posted above support your 21 s claim?

The Merlin XX is what the RAE refer to in their report R&M 2349 as well. So you both use the same engine data but come to different conclusions.

Why do you agree on the low level results but come to different conclusions for 20,000 ft performance?

Remember the RAE result is that the Spitfire will sustain a loadfactor of n=1.57 (bank angle 51 degress) and turn time 31s at 20,000ft. You get sustainable loadfactor n=2.70 (bank angle 68 degress) and turn time 21s at 20,000ft. Both results refer to the same engine so please explain.

BTW: I note that while you are quick to question other peoples competence and credentials you have not provided anything of substance yourself to back up your claims and it's faily obvious you have nothing to show so I wont press you any more on that.

[MiG-3U]

Originally Posted by Crumpp

The RAE's use of a single chart given the absence of any differientiation between power levels makes perfect sense with the Merlin XX predictions.

The Merlin XX was predicted to maintain similar power from sea level to 20,000 feet.

1020 Hp at Sea Level and 1075HP at 20000 feet:

http://www.enginehistory.org/members...a/Table-04.jpg

http://www.enginehistory.org/members...lysisR-R.shtml

1. The Merlin XX had a two speed supercharger. The first page you refer gives power at high altitude gear at sealevel due to analysis. See the appendix A at bottom of the second page for power at low altitude gear at sealevel.

2. Even at constant KEAS speed and constant power, the resulting force, thrust, decreases when the altitude increases because force is power divided with true speed. To maintain given angle of bank at given KEAS, power must increase with altitude.

[MiG-3U]

IvanK,
Could you please post parts of the report on turning performance at 20k?

TIA

[IvanK]

This is I think the only relevant bit that includes Sustained turn boundaries for 20,000',25,000',30,000', and 35,000'. "Angle of straight Climb" is Ps=0

[MiG-3U]

Thanks IvanK,

So power is higher, 1100hp at 20k, than 1050hp at 12k. Time to turn 360deg is about 30s at 20k, while it was 18.6s at 12k.