can "we" have 1 more Spitfire/109 variant?

[Bronk]

Originally posted by Kurfürst
Yup Kurfurst I agree the XVI at 25lbs boost would be a perfect match for the G14, unfortuneately a 5700fpm climb @25lbs from 0-5000ft has people peeing their pants.

These results are for a plane with half the fuel load that had it's radiators wired shut for the tests for less drag. It wasn't the standard way of measurement. There was no way to manually shut the radiators on the MkIX once it began to open as temperature rose - that started already 10 celsius over normal pressure.
Apply the same standards to other planes, and you will get similiarly hyper-inflated results for quite a few latewar planes.

The last I checked under comparable conditions (full load, radiators open) it did around 5080 fpm, which is nice, between 0-500(five hundred) feet altitude, which is less impressive.

Where does kev mention MK IX. He clearly talking about the MK XVI . I know you can read . I asume that you are trying to deflect attention from his point .


Bronk

[Kev367th]

Actually Bronk the LF IX and XVI motor were identical, just manufactured in two different places.
IX was RR Merlin 66
IVI was a Merlin 66 built in the U.S. , designated Merlin 266.

Performance should be identical 'clean'.

Re: Wired shut radiator flaps - looking at some docs that 'may' suggest this was not needed to obtain the 5700fpm @ 0-5000ft. Although even the RR tech guy I spoke to suggested that figure seemed high, maybe obtained with a 'cold' engine at the start.

WIERD.

Yup I have seen climb rates closer to your 5080fpm 0-5000ft.

[Bronk]

Were the MK IX and XVI airframes also identical ? Also  thank you for the engine info.
Sory for snap judgment about kurfy post but well ya know.
Also didn't the MK VIII have retractable tail wheel and the  MKXVI not. Or am again misinformed.

Bronk

[Karnak]

LF.Mk .IX and LF.Mk XVI are functionally identical.  Using the two mark numbers in AH just gives an easy method to add the earlier F.Mk IX and the later LF.Mk IX/LF.Mk XVI.

The Mk VIII did have a retractable tail wheel as well as reduced length ailerons.  The MK XIV was based off the Mk VIII airframe and shares all the Mk VIII features such as wing fuel, retractable tail wheel, reduced length ailerons and stiffened wings.

[Angus]

Hey Kuffie:
"Maybe yes, maybe not. Was their any difference between the MkVIII and MKIX ailerons control ? Any details, testing etc?"

Yes there was. It was the hinges I belive. Will did it up and post later.

As for the ammunition, - I hadn't noticed!

As for the fuel ,well, 50% internal makes quite a difference in AH

[Pongo]

They really missed out not putting in a bubble canopy on the XVI.

[Karnak]

Originally posted by Pongo
They really missed out not putting in a bubble canopy on the XVI.

It was too late to be representative and it would have been more work for SUPERFLY.  Bubble canopy Spits didn't enter service until March, 1945.  The LF.Mk XVI may need to be used from mid-1943 on to the end of the war, depending on if we get a Mk VIII or not.  The bubble canopy would have limited it to only the extreme end of the war.

[Nashwan]

These results are for a plane with half the fuel load that had it's radiators wired shut for the tests for less drag. It wasn't the standard way of measurement. There was no way to manually shut the radiators on the MkIX once it began to open as temperature rose - that started already 10 celsius over normal pressure.

Isegrim, you'll be pleased to hear Neil has got hold of the cooling figures for the Spitfire at 25 lbs on climb.

What they show is that the radiators do not have to be wired shut, under normal conditions they will be shut throughout the climb, as temperatures will not reach the level at which the radiators open.



This test was done at a sea level temperature of 8c (standard sea level temperature drops 4c with an altitude increase of 2,000ft)

As you can see, with the radiators shut, the coolant temperature climbs to a maximum of 106 centigrade.

The Spitfire radiators open when the coolant temperature reaches 115 centigrade.

So, at 8c, the radiators will not open even after a maximum power climb from 2,000 ft to 32,000 ft. In fact, it doesn't even come close to opening the radiators.

This chart also answers another question, Isegrim. The "standard summer temperatures" used in calculating the radiator suitability. The temperate summer temperature assumed in the standard is 27c at sea level, and the tropical summer temperature standard is 41c. Pretty high, but then the usual RAF practice of wiring the radiators open for climb tests shows they were interested in finding worse case numbers, not artifically inflating results.

Re: Wired shut radiator flaps - looking at some docs that 'may' suggest this was not needed to obtain the 5700fpm @ 0-5000ft.

No, looking at the cooling results, under normal conditions they would remain closed of their own accord.

These results were at 8c. Perhaps someone better at maths can work out likely results at higher temps?

The formula used in the tests was:



The value of Tn was 125c for full power and 115c for cruise.

Although even the RR tech guy I spoke to suggested that figure seemed high, maybe obtained with a 'cold' engine at the start.

I don't think they'd have run a full power test with a cold engine, or even taken off with one, for safety reasons. But you can see here that the coolant temp at 2,000ft at the start of the test was 78c. The report says that high speed radiator suitability figures are the temperatures reached after 5 minutes at full power in level flight.

Radiator suitability 1.36 = 125 - 21 / (coolant temp - 2)

coolant temp =  78c

(radiator suitability 1.36 at 3,000 ft level flight radiator closed, 125c max permissable coolant temp, 21c standard summer temp at 3,000ft, -2c observed temp at 3,000ft)

So 78c is the temperature reached after 5 minutes flat out with the radiators closed at 3,000ft. The climb test started at 2,000ft, but the start temp of 78c should still be very close to maximum in level flight at that altitude.

Yup I have seen climb rates closer to your 5080fpm 0-5000ft.

I suspect that's with radiator flaps wired open. The RAF usually tested with flaps forced open, to get a worst case figure. Of course, in real like the flaps didn't open until the temperature reached 115c, and cooling was pretty good even with the radiator flaps "shut" (shut on the Spitfire was about half the exit area of open, the flaps couldn't close completely)

Edit: This assumes my maths is right, and that's a dangerous assumption at this time in the morning

[Krusty]

So the super uber 5700fpm was the WORST CASE???

No way this baby's getting the high boost y'all want, in that case. As-is it'll be enough of a monster

[Kurfürst]

Originally posted by Krusty
So the super uber 5700fpm was the WORST CASE???

No way this baby's getting the high boost y'all want, in that case. As-is it'll be enough of a monster [/QUOTE

Not quite. Hop's cooling table is for operation in the second s/c speed - FS gear, with wired shut radiators.

With FS gear and closed rads, +25 lbs, the Spit IX climbed 4720 fpm at SL, not 5700 :

(Image removed from quote.)

The table is very interesting, and it finally tells the details of that spit cooling test. It was done at  4 degree celsius temperature, pretty cold, ie. automn/winter conditions, the best case for a cool engine. The coolant temperature at the start of the climb was well below the normal coolant temperature for the Spitfire (95 degrees), ie. 78 degrees. And as run in FS gear, the engine was developing quite less power at low altitude. The fact that the coolants can be shut at even high altitudes is pretty normal for all planes, since they loose power/boost quickly above FTH - and the FTH of SpiIX/+25 is very low, around 11 000 feet or around 3500m, above that the engine develops less power - and heat.

That explains the results very well.

BTW, Hop is wrong in that the radiators would open only at 115 celsius - they would be full open at that time, they began to open at 105 celsius, 10 degree above the normal operating temperature, ie. 95 degrees.

Hop chart show the temperature will rise 12 celsius in the climb from 2000 feet when it reaches 10 000 feet, ie. after climbing 8000 feet - this means, with 4700 fpm climb rate, that the radiators began to open after about 1.5 mins of operating at +25lbs boost, if starting at a normal operating temperature, not with a cold engine. As the rad flaps open, they cause more drag and the climb rate fells from 4700ish to 4200fpm when they are fully open. This assumes operation in FS gear, the temperature in MS gear would rise much more quickly, there's more power and more heat to deal with. Frankly this is nothing extraordinary compared to other cooling tests I have.

[Nashwan]

It was done at 4 degree celsius temperature, pretty cold, ie. automn/winter conditions, the best case for a cool engine.

8c actually, it was 4c at 2,000ft. Standard atmosphere is 15c, dropping about 2c per 1,000ft at low level.

The coolant temperature at the start of the climb was well below the normal coolant temperature for the Spitfire (95 degrees), ie. 78 degrees.

What is "normal coolant temperature"?

78c was the temperature after 5 minutes at maximum power in level flight. Cruise temperature was somewhat lower.

BTW, Hop is wrong in that the radiators would open only at 115 celsius - they would be full open at that time, they began to open at 105 celsius

Not according to the Spitfire manual, which states:

"On all aircraft the coolant flaps are fully automatic and are designed to open at a coolant temperature of 115 C"

10 degree above the normal operating temperature, ie. 95 degrees.

Where does this "normal operating temperature" come from?

Cruise at 3,000ft at a sea level temp of 8 C resulted in a coolant temperature of 73C, and that was the stabilised value.

Hop chart show the temperature will rise 12 celsius in the climb from 2000 feet when it reaches 10 000 feet, ie. after climbing 8000 feet - this means, with 4700 fpm climb rate, that the radiators began to open after about 1.5 mins of operating at +25lbs boost,

If you start the climb with coolant temperature of 103C. Considering the temperature after 5 minutes at maximum power was 78C, that's a rather high temp to be starting the climb.

So the super uber 5700fpm was the WORST CASE???

No, 5,700 ft/min would be pretty much best case. The sort of figures Isegrim is quoting are pretty much impossible case, though (ASSuming 103 C coolant in level flight at low level, for example)

But the point is, under normal conditions the Spitfire would climb with radiator flaps shut. The RAF tested to ensure the aircraft met cooling standards at sea level temperatures of up to 41 C, which is why they usually tested with radiator flaps wired open.

[Pongo]

Originally posted by Karnak
It was too late to be representative and it would have been more work for SUPERFLY.  Bubble canopy Spits didn't enter service until March, 1945.  The LF.Mk XVI may need to be used from mid-1943 on to the end of the war, depending on if we get a Mk VIII or not.  The bubble canopy would have limited it to only the extreme end of the war.

who cares about "the war"
Its not about scenarios its about experiancing the aircraft in the MA.
Say it was too much work if you like but admit thats the case, the plane they have added could have been represented with a clipped wing spit IX. With the XVI they had a chance to have a truely different plane and they passed on it.

[Karnak]

The IX could just as easily have been a bubble top.

In any case I think they are making the aircraft for the MA and ToD, not scenarios primarily.  For the MA either will do, though the bubble top may have been more interesting.  For ToD though the only one that would be useful is the high backed Mk XVI.

[Squire]

The Spit XVI still has the armored headrest? wether its bubble top or not. I dont see it being that big a deal, at all.

Compare the P-51B and P-51D, somebody will have to show me what the huge vis diff is.

As for clipped wings and a Merlin 66, that actually has a difference on its manuerverbility, speed and climb.

In addition it has 3 pylons and the 50 calibers.

It is significantly different than a F.IX. They didnt pass on anything

[Krusty]

The 5700fpm was made with radiators wired open. Thus inducing drag. So if you say that was just for testing purposes, and that normally the same spit would have had them closed if they were on "auto", then it would surely be about 6000fpm (far less drag in the climb with the radiators not wired open).

That's absurd, for AH's purposes.