SPIT MK I/II and over boost

[ACE-OF-ACES]

Originally Posted by JtD

As an example of WW2 climb tests, look at table I in this Spitfire IX test, you can see a constant IAS up to FTH and a constant TAS above FTH. Il-2 compare will always give you constant TAS, which will give you the somewhat higher climb performance below FTH, about 100 fpm in this case. Less than 5% obviously, and all I wanted to say.

Ah good so both you and that report agree with what I allready said, i.e.

Originally Posted by ACE-OF-ACES

Some if not most planes ROC performance required the BCS to be adjusted as altitude increased

S!

[VO101_Tom]

Originally Posted by CaptainDoggles

Got data to back that statement up?

Sadly, any real-life pilot can confirm it. The MsFS is very excellent on-board systems, avionics and instrument flight simulation. But the flight model is a large pile of xxxx...

[klem]

Originally Posted by klem

The A2A Spifire is sweet to fly and similar in handling to the CoD although to me it 'feels' nicer. The IIa seemed to me to have better acceleration but I haven't done any comparative tests. The A2A Spit Ia only comes with the fixed 20' pitch wooden prop or the DH5-20 2 position three bladed prop (like the DH5-20 in CoD). It does not come with a CSP. It is more sophisticated that CoD in that the engine is more prone to lasting damage through mishandling, e.g. overheating is not only hard to overcome but with Accusim modelling it causes lasting damage to the engine which stays with you on the next flight unless you put right 'in the hangar'. If looked after properly it is just fine.

I'll try to find time to compare level speeds and climb to height in the two DH5-20 versions.

I've done the A2A FSX Spitfire MkIa with the DH 2 pitch prop and will post results soon but the CoD DH5-20 isn't modelled properly. It should be possible to obtain variable pitch in the mid-range of the prop control (which should be a plunger btw not a lever) making it effectively a variable pitch prop although not intended to be be. In fact using the variable capability became an official recommendation and it could deliver almost the same performance as the Rotol in expert hands with the pilot being the 'constant prop speed' governor.

Bottom line is I'll have to use the Rotol set to 2600 rpm which is the prop speed I manually maintained in the A2A FSX model. As the 2 pitch props were capable of being converted to CSPs in the field I am assuming they used the same blades.

[Crumpp]

Historical performance data for climb typically comes with a climb speed information. This climb speed hardly ever is constant.

Climb speed will never be constant with altitude. Any pilot or first year aeronautical science students knows this....

Climb rate without speed is useless information. All aircraft performance occurs at a specific point on Power required curve and is fixed by the design of the aircraft.

If speed is held constant, the aircraft is not maintaining the best performance point on the Pr curve.

http://home.pcisys.net/~aghorash/Why...h_Altitude.pdf

http://aerosrv.cls.calpoly.edu/dbiez...20and%20Vy.pdf

http://www.pprune.org/tech-log/343259-vx-vy.html

http://williams.best.vwh.net/smxgigpdf/mfly2.pdf

[JtD]

Originally Posted by Crumpp

Climb speed will never be constant with altitude. Any pilot or first year aeronautical science students knows this....

Yes, and in second year they learn that there always are exceptions to the rule, and thus it's "hardly ever" and not "never". An example for an exception has already been given in this topic, so feel free to educate yourself.

[Crumpp]

Yes, and in second year they learn that there always are exceptions to the rule, and thus it's "hardly ever" and not "never". An example for an exception has already been given in this topic, so feel free to educate yourself.

Baloney. To achieve Vx or Vy, velocity must change with altitude. There are no exceptions to that no matter how much you tap dance.

[camber]

Gentlemen!

So many of these arguments seem to based on interpreting an slightly ambiguous statement to make it wrong.

Originally Posted by JtD

As an example of WW2 climb tests, look at table I in this Spitfire IX test, you can see a constant IAS up to FTH and a constant TAS above FTH. Il-2 compare will always give you constant TAS, which will give you the somewhat higher climb performance below FTH, about 100 fpm in this case. Less than 5% obviously, and all I wanted to say.

Well this is pretty clear and supported by the reference. the Spittie pilots doing that test climbed at constant IAS mostly and recorded climb rate.

Originally Posted by Crumpp

Climb speed will never be constant with altitude. Any pilot or first year aeronautical science students knows this....

Obviously the pilot can choose to climb at constant IAS if aircraft capability permits. I take it, this statement should be:

Vx (IAS for best climb angle) and Vy (IAS for best rate of climb) will never be constant with altitude."

This is true enough but I know a flight instructor that had it a bit confused . So climb tests at constant IAS (such as that Spittie one) may not be capturing optimum rate of climb at each altitude? Interesting.

Originally Posted by JtD

Yes, and in second year they learn that there always are exceptions to the rule, and thus it's "hardly ever" and not "never". An example for an exception has already been given in this topic, so feel free to educate yourself.

There seems no real disagreement at this point, just an imaginary one

Originally Posted by Crumpp

Baloney. To achieve Vx or Vy, velocity must change with altitude. There are no exceptions to that no matter how much you tap dance.

A clearer statement now it is expanded from just "climb speed".

It is quite hard to write unambiguously in technical detail, and anyone's forum posts are likely to fall down on this now and again regardless of their aviation knowledge. But instead of jumping on it as evidence of moron, why not have a lovely big glass of wine? Of course that is what I am doing AND writing this post, so maybe you can do both if you really want to

2007 Reisling, camber

[JtD]

Oh, an educated voice of reason with good manners, what a refreshing sight. I sure hope to see you around for a long time!

[ACE-OF-ACES]

Originally Posted by camber

Obviously the pilot can choose to climb at constant IAS if aircraft capability permits.

The funny part is Crumpp is saying the same thing

He just appears to be a little confused with regards to 'vector math' (what he called correct physics).

That being the resultant (single) vector that is the equivalent of a set (more than one) of vectors. Where is is possible to have a resultant vector with constant magnitude as it changes direction.

In this case the 'resultant' vector is IAS, that is the equivalent of the Vx and Vy set of vectors

From the spitfire test data we can see it maintained a constant IAS for most of the climb, but at the same time the ROC changed as the spitfire climbed.

Mathematically speaking, the resultant vector (IAS) 'direction' changed to maintain the resultant vector (IAS) 'constant magnitude'.

In the case of the spitfire ROC test the 'climb angle' changes which in turn changes the direction of the resultant vector (IAS). Which in turn changes the magnitude of Vy and Vx.

Note in this case Vy is equal to the ROC, the vertical component and Vx is equal to the horizontal component (i.e. earth frame of reference aka coordinate system)

At this point I think it would help those having trouble with vector math to check out the following link..

Comparing Two Vectors

Paying special attention to Example #2, vectors with same magnitude but different directions, i.e.



And just to be crystal, allow me to say this again, the 'constant' climb speed statement was more of a test pilot term.. It did not mean they kept it constant down to three decimal places, that is just humanly impossible. What it meant was 'when' you change the IAS during the climb as required, the change should be made as smoothly as possible such that the change in acceleration was kept as small as possible.

[41Sqn_Banks]

Originally Posted by camber

Well this is pretty clear and supported by the reference. the Spittie pilots doing that test climbed at constant IAS mostly and recorded climb rate.

Obviously the pilot can choose to climb at constant IAS if aircraft capability permits. I take it, this statement should be:

Vx (IAS for best climb angle) and Vy (IAS for best rate of climb) will never be constant with altitude."

This is true enough but I know a flight instructor that had it a bit confused . So climb tests at constant IAS (such as that Spittie one) may not be capturing optimum rate of climb at each altitude? Interesting.

Spitfire I Pilot's Notes state:

CLIMBING

9. For maximum rate of climb the following speeds are recommended: -

Ground level to 12,000 feet 185 m.p.h. A.S.I.R.

12,000 feet to 15,000 feet 180 " "

15,000 " 20,000 " 170 " "

20,000 " 15,000 " 160 " "

Hurricane I Pilot's Notes state:

Optimum climbing speeds (A.S.I. reading)

For aeroplanes fitted with 2-bladed wood airscrews to Drg. No. Z. 3895 and with kidney type exhaust manifolds, the optimum full throttle indicated climbing speed at sea level and up to 10,000 ft. is constant at 157 m.p.h., A.S.I. reading with a reduction of 1 m.p.h. for each additional 1,000 ft. of altitude.

Note. - The all-up weidght of the aeroplane during the tests upon which the above climbing speeds are based was 6,000 lb.