Constant speed on Mk1

[severniae]

Hi All,

I was just wondering if it is possible to have the constant speed propeller on the Mk1 Spitfire? Reading the manual it states that all 3 props are available for the mark 1, however unless I've missed something it appears that you can't select the constant speed unit for the Mk1.

Is there any way to change this or was it a design decision?

Secondly, whilst on the Mark 1 - I have a question regarding the two position prop. I've been flying it recently trying to use the two position prop as a variable pitch and trying to adjust the pitch to suit the power I'm applying. Sometimes this has good results but often it feels wrong, feels like I'm applying too much power for too little gain, and as such tend to cook myself in the process!. Could someone with a little more experience please explain to me how I should fly using this method? I've spent a lot of time flying with the CSU, and a fair bit on fixed but this one is new to me!

Many thanks,

Sev

[r4y30n]

I believe it was a historical design decision on A2A's part. While the Merlin III in the Mk Ia could mount a constant speed prop, the Rotol CSU did not even exist until the Mk II came about and was only ever fitted to the Mk I for testing purposes (http://en.wikipedia.org/wiki/Supermarin ... _variants)). It wasn't really until the Mk V that constant speeds (de Havilland or Rotol) became commonplace on Spitfires, with the heavier de Havilland being the most common since Rotol production was limited and the de Havilland 2-pitch props already on the planes were easily converted to CSUs.

I have heard the de Havilland CSU will be an option on the upcoming Mk V.

[Killratio]

I believe it was a historical design decision on A2A's part. While the Merlin III in the Mk Ia could mount a constant speed prop, the Rotol CSU did not even exist until the Mk II came about and was only ever fitted to the Mk I for testing purposes (http://en.wikipedia.org/wiki/Supermarin ... _variants)). It wasn't really until the Mk V that constant speeds (de Havilland or Rotol) became commonplace on Spitfires, with the heavier de Havilland being the most common since Rotol production was limited and the de Havilland 2-pitch props already on the planes were easily converted to CSUs.

I have heard the de Havilland CSU will be an option on the upcoming Mk V.

Correct, the main reason that the ROTOLs did not go to the Mk I was that they were in limited supply and the Hurricane needed the performance boost more than the Spitfire. Thus the Hurricane got the ROTOLs in preference and DeH were asked if they could do a conversion...leading to the famous quote by a DeH employee along the lines of "We shall probably never be paid for this" to which he received the reply "and if we don't do it, there will likely be nobody left to pay us" ..... I believe that as late as 1944 DeH weree STILL trying to get the last of this money out of the A.M.!!

D

[r4y30n]

I hadn't heard about the lack of funding, just of their techs driving out in vans with the conversion kits to teach RAF mechanics how to install them...

[severniae]

Ah thanks guys for the responses to the reasons as to why the CSU wasn't put into the Mk1 - still a great plane to fly either way, finding learning the variable prop quite an interesting challenge! By the way can anyone help out on the second question?

Many thanks,

Sev

[r4y30n]

Not sure what you mean about too much power for too little gain, are you having similar issues with the Mk II? The Mk I has a higher power-to-weight ratio so I've often found temps more manageable in the Mk I than the Mk II, despite the 100% glycol coolant.

Really you just have to follow similar RPM to that recommended for the constant speed in all phases of flight except start up/shut down (the Mk I tends to like a little less RPM and boost, however). It just happens to be more work because every time you change throttle, speed or altitude you will need to adjust the prop to maintain RPM. Everything is in the manual starting on page 59.

The only other note for the 2-pitch is that it has shorter stops than the Rotol, meaning it cannot go as fine as the constant speed nor as coarse.

[Killratio]

A little bit of competition between two ideas.

First... pitch up then power up, or power down then pitch down.

Second...set boost required then adjust prop.

Now with the DeH this is a balancing act as the rpm "available" can affect the boost available.

Here is how I do it:

After take off, reduce throttle to climbing boost (+4, say) then coarse the prop to climbing rpm (2600). The Boost may move slightly, so reset that to +4 then adjust the rpm again to 2600...this balance should then be maintained during climb....YOU are the CSU.

You have to remember that the prop is designed to be used two speed...full fine for takeoff and full coarse for everything else. Using it as a variable takes finesse and you can have the situation you describe, particularly when you set very low boost and finer pitch for cruise. Far better to have HIGH boost and low RPM. A typical high speed cruise might be +4 and 2600rpm. Most people assume exactly the opposite and I see people cruising around at -2 and 2400, for instance "to save the engine".

In general (and I know I KEEP saying it):

"Low revs high boost, will bring you safely home to roost"


Darryl

[severniae]

Thanks for the replies chaps. Darryl, I'll give your method a try and hopefully have better results! I never cease to be impressed by your wealth of spitfire knowledge!

As a side question, if performing an aerobatic display in the mk1, how would you personally go about it?

Many thanks,
James.

[Killratio]

James,

Thanks and glad to help.


Aerobatics.

"Display" means low level. That means extra care, of course. I'll start by saying that I don't have a low level endorsment, just a couple of hours at 1,500ft and in the Extra 300, not a Spitfire.

1. The hardest thing in aerobatics, as with all things in aviation, is the ground. Be instinctively and VERY aware of where it is, how far away it is and how fast you are travelling towards it.

2. (courtesy of Dudley) A little nose DOWN trim will give you that extra 1/2 second if you lose SA inverted at low level.

3. The Mk I presents a challenge in managing rpm. As I have bundles of hours aeros in FP aircraft, this doesn't worry me..but if you are a CSU pilot, it takes some adjustment. There are two ways, of which I use the second, (b) exclusively.

___a) Set throttle and then manage rpm via pitch control (ie, YOU become the CSU)

___ b) Set rpm at fast cruise speed and then manage throttle to avoid "redline".

The second helps with cooling, always an issue in the Spit.

4. To set up for aeros, I set 2600rpm at +6 Boost in level flight and normal or +1 radiator, depending on OAT. +4 Boost is easier to manage temps with but I prefer the extra power and have ways around the heat problem...more on that later.

5. Aeros must be flown pretty much 100% accuratly and smoothly to maintain safety AND to look good. Many people think that aeros are a thrilling, no holds barred, death ride....not only is that fairly easy to do, crude and uncomfortable but it also looks like SHoneT from the ground.

6. Watch entry speeds closely. Many manoeuvres can be done in the Spitfire and will return you to your starting altitude or a little higher..always nice at low level...IF they are flown at correct speeds and performed accurately......start practice at 3,000ft and work lower as you gain skill/confidence. Remember at 3,000ft that ANY time you get even slightly below this, you just died in low level aeros and maybe took some spectators with you!!!!

7. Aileron Rolls at Hangar Height are possible (and faithfully recreated in the A2A Spit) if started at 160mph and done "just right".

8. I don't do pure Barrel Rolls low down..I don't like the amount of time spent with nose below the horizon. I tend to do these off a Half Cuban, so they start at 2,000ft or so.

9. Flick manoeuvres..crude, pointless, hard on the airframe and dangerous. Any idiot can flick an aircraft (some can even land afterwards), only modern, unlimited class aerobatic aircraft are truly built to do it in style. As an example, the Extra will flick repeatedly and marvellously. A C152 WILL flick but there is only about a 5 knot grace between possible, safe and dangerous. Not my kind of odds.

10. Cuban Eights and Half Cubans are not only my personal favourite in sim and IRL but the Spitfire was, quite simply, built for them. Try ground level to 3,000ft and return, using loop entry speeds. Half Cubans are helpful for gaining height and for re-acquiring the "display line" at each end.

11. I don't like stall turns low down, as the Spit has too much controllability right down to the stall and the potential for overcontrol on the rudder and inadvertant spin entry is too great IMHO.

12. I don't do Split S manoeuvres at low level. Some people will try to tell you a Split S is just the last half of a loop....it is not..the forces, speeds and atitudes are VERY different. They are a good way to become a Lawn Dart.

13. Whenever you are above 180mph leave your feet off the rudders...let her fly as she was intended to fly..rudder is not very helpful in most circumstances and is counter productive in some. Low Aileron Rolls are the only time I use them.

14. Break Turns at low level look great and help you re-acquire the display line from each end.

15. G management. The Spit will take more than you will! But try very hard to keep between Positive 1/2 and Positive 4G. NO negative G at all. Of course with no G meter, you have to "feel" this. (or turn on Shift z) Be highly aware of accellerated stalls...always have it burned into your brain that stall is a function of "angle of attack" NOT of speed. I am a big believer in the "Stall Stick Position" it will vary slightly with condition of flight but not that much. Learn WHERE it is on your controller and stay inside it.

16. Cooling . Start up and get off within limits. Climb to 5,000ft-8,000ft. Set a cruise at +4 and 2400rpm, radiator "normal", for 5-10 minutes at 5000-8,000ft depending on OAT until temps return to normal cruise level. Then turn back to start display.
I use long dives at lower throttle and high speed (remember managing the rpm to keep it at around 2600 by use of throttle alone) but watch "prop driving engine"... stay at -1 boost or above for your 2600prm setting. +0 is safer. Usually I am doing this off a Half Cuban. Plan your routine so that at known high temp times, you have a couple of Half Cubans and dives for cooling.

Hope that helps a bit. I do enjoy the Spit I for aeros more than the Spit II. The CSU is just boring


Darryl

[severniae]

All I can say is wow! I'll give it all a go, thanks Darryl for the amazing advice as usual!

[Killratio]

No problem at all James,

Good luck with it and feel free to ask any questions.

Darryl

[InPursuit]

The MK1 represents how the original spitfire was designed to fly and (at least in the A2A version) it is a dream. I can fully appreciate the novice pilots point of view. What I really appreciate with the A2A Spitfire is that you are given the chance to step through the evolution of the spitfire (and thus of other aircraft). The propeller simulation is a case in point. I was expecting, like the original post, to be able to choose a constant speed (Rotol?) propeller for the MK I. My understanding was that C.S. propellers were fitted to all front line MK1's prior to the BoB and that 100 Octane fuel was the norm.

http://www.spitfireperformance.com/spitfire-I.html

Have I got something wrong?

Thanks

P.S. Another nice touch would be if a Tilley orifice could be fitted to the carburettor by Miss Shilling (March 1941?).

[Lewis - A2A]

Hello,

if you are not a high realism Accu-sim user then please get the fix here for non Accu-sim relaxed realism flyers;
http://a2asimulations.com/public/update ... t_dats.zip

thanks,
Lewis

[InPursuit]

Thanks a lot for pulling out all the stops to get me the conversion kit Lewis. Ah, the nice familar cockpit with the manual landing gear. I am using Accu-Sim, although I have often got the engine damage switched off at take off. If I understand correctly the conversion shows the Rotol/MKI setup, but it is actually running the DeH 3 blade propeller simulation. For the 100% Rotol simulation I need to upgrade to the MK IIa.

[Lewis - A2A]

Hello,

If you are a Spitfire Accu-sim user you can change the prop and canopy in the maintenance hanger by clicking on the images of either. We have different props and the early and later canopy available so you can go real early MKI with the flat canopy and toe blade prop.

Thanks,
Lewis


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