Question for the Motor Heads

[Blakduk]

Dutch- He makes me feel like i'm a 12yr old playing games while he's a grown-up doing things for real (which is all very accurate, except i'm well past 12).
I'll humiliate myself and ask him, i can handle his disdain.

Back a few years ago i met a guy called Alec Henshaw. He was a test pilot for Spitfires during WW2 and flew hundreds of them- now he would have been the one to ask!

[winny]

Originally Posted by Blakduk

Dutch- He makes me feel like i'm a 12yr old playing games while he's a grown-up doing things for real (which is all very accurate, except i'm well past 12).
I'll humiliate myself and ask him, i can handle his disdain.

Back a few years ago i met a guy called Alec Henshaw. He was a test pilot for Spitfires during WW2 and flew hundreds of them- now he would have been the one to ask!

Just for you.. Alex Henshaw in action over Castle Bromwich 1941
The 1st Min of the video is him.

http://www.youtube.com/watch?v=nCmzYccyBYM

[Blakduk]

Winny- I've been googling Alex Henshaw this evening. I didn't realise he was such a celebrity!
I basically just said 'G'day' to him as he was surrounded by other pilots & engineers- he was having afternoon tea in the hangar my brother was working in (i was helping by shifting boxes of gear in a ute, filling the esky with beer and getting food etc). They were working on Spitfire that was in bits- it was owned by a New Zealander and i think it ended up at Wanaka. They were pointing at bits and nodding knowingly at each other- about the only thing i contributed to was a discussion about the bolts being made of magnesium. I commented they would react with the aluminium and disintegrate over time- i got an approving nod and went to get a beer (it was after 4pm after all and i thought i better quite while i was ahead). I do recall him saying the Spitfire was 'only a 1000 hour airframe, so it's a wonder any are still flying today'.

[winny]

Originally Posted by Blakduk

Winny- I've been googling Alex Henshaw this evening. I didn't realise he was such a celebrity!

I thought you didn't really realise who he actually was

He's a bit of a legend Spitfire wise, you were lucky to meet him.


Anyway I don't want to interrupt the thread too much.

Now what is it again? More throttle to go faster, less to go slower, ignore gagues - repeat till engine explodes?

[Blakduk]

Back on topic, a slight reframe of the query:
- throttle steady, maintain altitude (and therefore air pressure is same)
- change pitch to coarse, increasing load on engine, dropping prop & engine RPM
- drop in engine RPM drops RPM of supercharger impeller, decreasing amount of air/fuel forced into inlet manifold
- drop in engine RPM decreases amount of air/fuel being sucked into cylinders.

Question- is the decrease in air/fuel negative pressure at inlet to cylinders more or less than the decrease in the positive pressure of air being forced into the inlet manifold by the supercharger?
If the decrease at the cylinder end of the manifold is more, the boost gauge will read higher as the boost gauge measures increased air pressure in the inlet manifold as there is a backup of air/fuel.

[ARM505]

I'll ask my question another way.

I'm comparing two different models (FSX vs CLOD), both of a Spit MkII with a constant speed propeller:

1) The A2A simulations Spit Mk II running in FSX. In this model, whilst flying at a constant altitude, constant airspeed, constant throttle setting, the indicated boost will DECREASE when you move the prop control lever to DECREASE RPM - the A2A docs mention that since the supercharger is now being driven at a lower RPM, the indicated boost will decrease. The decrease is however very slight.

http://shockwaveproductions.com/

2) The CLOD model, which (under the same conditions), will show an INCREASE in indicated boost when the RPM is commanded to a lower value via the propeller control lever, ie the opposite of the A2A model in FSX.

Since they display the opposite behaviour, one is therefore correct, and the other incorrect. My question is thus which is most true to life. The A2A Spit is widely recognised as a very well modelled aircraft in FSX terms. I have in the past accepted it's behaviour (with the exception of the rapid wear issues) as well modelled. I would like to find out if this is true in this respect.