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I've been looking at similar lightweight interceptors. The Demon with 850 hp, 314 mph: Shoki I, 1250 hp, 363 mph; Shoki II, 1440 hp, 378 mph; FFVS J22, 1050 hp, 357 mph. So maybe the Venom would have 20 mph knocked off its top speed fully armed and would need a Bristol Mercury just to recover that lost speed. However, we do need a fighter in the Far East, preferably of local construction, 2 HMG, 4 LMG.and the trouble when you start with "Small, cheap," is it seldom works out to be "adequate, ideal"
312mph may have been plausible for an unarmed prototype. there is argument about that. You still, for plane to be used after the summer of 1940, need to add armor and self sealing tanks for a western nation.
We do have this quote from "The British Fighter Since 1912" by Francis Mason.
"Constant trouble with the Aquila engine and its ancillary systems prevented it from undergoing full service trial, although Fg Off Jefferey Kindersley Quill, who had recently joined Vickers, continued to perform manufacturers trials for some months."
The plane is supposed to have weighed 4165lb all up.
AS Tomo has pointed out and supplied an engine chart for for, the rated altitude for the engine is nowhere near the altitude at which the 312mph is claimed. Now perhaps the Venom had a different engine than the chart is for? But getting anywhere near 600hp at 14-16000ft is going to be impossible for such an engine. The Aquila was a 15.6liter engine, the French 14 cylinder engine used in the two planes pictured above was 19 liter engine and it ran at 3030rpm, So engine that is almost 22% bigger in displacement running at the same rpm has trouble doing what is claimed or implied for the Aquila?
You could try sticking the Mercury in it, it is only 200lbs heavier, 5.5in bigger in diameter (3 more square feet of frontal area) and will need a bigger prop.
I would also note that the Ki 27 prototypes used two different engines while the production aircraft got a 3rd. This is where we have to be really careful in comparing engine powers.
This is an old book and could be wrong so here it goes,
Nakajima PE had a Nakajima Ha-1-Ko engine rated at 710hp for take-off and 650hp at 6,560ft (2000 meters) it also had a 176.5 sq ft wing.
The 1st Nakajima Ki 27 prototype had a slightly bigger wing of 189.4 sq ft and the 2nd prototype got a 199.8sq ft wing. The bigger wing knocked 4mph of the top speed.
After some 10 or so pre-production examples were built they went for the production Ki 27-Ko which was fitted with the Ha-1-Otsu engine which was rated at 710hp for take-off but 780hp at 9,515 ft (2900 meters). so the 290mph is being done with 780hp. 25% more than the Aquila if the Aquila, by some miracle actually made 625hp at
Same take off power and perhaps the cruise wasn't far off but the difference between this engine and Mercury at 3-5000 meters is not going to be that great. At least not anywhere near what the original engine was.
As a comment I would note that the Gloster F9/37 got a very strange set of Taurus radials that allowed to go 360mph at 15,000ft which seem to have disappeared after a landing accident
and it took years (if ever) for a Taurus to develop that kind of power at that altitude again. A Taurus III was supposed to have been used in Australian Beauforts that made 1060hp at 14,500ft at 3300rpm. How many go this engine I don't know as the Taurus VI was also used in Australian Beauforts before they switched to P&Ws. The VI was low altitude engine that maxed out at 3100rpm.
The Taurus used the same bore as the Aquila but used another 6mm (1/4in) of stroke. How close the cylinder barrel finning and heads were to each other I don't know.
A few comments on fuel. Higher octane fuel will not usually increase the FTH of the engine. That should be the height at which the throttle is fully open and the supercharger is delivering all the air it can at the full rated speed (rpm) of the engine. If you over speed the engine the supercharger of course turns faster and can deliver more air/higher boost.
If the engine is having cooling problems and running into temperature limits causing detonation with low octane fuel switching to higher octane may allow higher boost and/or higher rpm, at least for short periods of time. In general high octane fuel allows for substantial increases in power at lower altitudes where this is excess supercharger capacity (throttle not fully open). At Altitude if you over rev the engine by 10% you will get a lot more air through the supercharger. But we seem to be at odds with flights using somewhat experimental or development engines vs service engines, Taurus engines in service were known for overheating at low altitudes running at lower rpm/power settings than we are taking about here.
as the guns and weights. It was no uncommon to ballast a plane to represent the weight of the guns and ammo and often they tried to place the weights close to where they would be. that is weights are placed in the wings in an appropriate location to simulate the weight of guns/ammo when rolling the plane or maneuvering vs just sticking a bunch of lead right on the CG in the fuselage.
I am guessing the plane was ballasted for the guns/ammo but was not suffering from the drag of access hatches or ejection slots. Muzzles were usually taped over in tests anyway and in normal flight.
Does anyone know if any record exists of the Venom's testing at A &AEE? -
Hey, what's a little skin wrinkling
I would be a little careful comparing to the Curtiss CW-21 Demon. the 850HP is the max continuous rating.The Demon with 850 hp
According to Tim Mason (British Flight Testing) no report was written because it was returned to Vickers early in the testing - when the wing skin started "wrinkling".
Which doesn't sound good....
Hard to believe all that time did not produce any documentation at all?
Would you recommend it? I've got his Hikoki title "The Secret Years" and that is excellent.