Armstrong Siddeley Cheetapard

[Schneiderman]

Has anyone information on an Armstrong Siddeley engine project from the late 1940s called Cheetapard? The name is obviously a mixture of Cheetah and Leopard.

 

[Apophenia]

According to Jean-Louis Bleneau - in Miles ou Handley Page (Reading), le Marathon - the Cheetapard was a 550 hp radial (mentioned in the context of a March 1944 Miles M.54 variant, the M.59 with two Cheetapards). I've also seen 585 hp listed for the Cheetapard.

The name suggests a two-row radial based on Cheetah components. If so, the quoted Cheetapard output seems low for a 14-cylinder 'Twin Cheetah'!

 

[Schneiderman]

Odd, isn't it? The only references to the engine I can find are the same as yours, comments on the Miles projects and one other. I agree that the quoted output appears too low for a 14 cylinder based on the Cheetah, so perhaps it was similar to the relationship between the Bristol Aquila and Taurus, the first a 9 cylinder and the second two rows of 7 using the Aquila's cylinder as a basis. So maybe two rows of 5 cylinders?

 

[DWG]

Given the Miles M.58 specified a 500hp inline that simply didn't exist, and George Miles apparently got quite insistent about using it and only it, no matter what MAP said https://www.secretprojects.co.uk/threads/miles-m58-and-martin-baker-mb5-help-please.5032/post-40098 , is it possible this isn't an AS design, but a purely Miles concept - 'well, a Leopard with Cheetah cylinders would probably be about right, call it the Cheetapard for now and I'll talk to AS and the Ministry when I get a chance'.

 

[Hood]

Peter Amos in his Miles book (vol.3) does not mention mentions the Cheetahpard in relation to the original civil M.59, rating 585hp. The naval transport M.59A having the Leonides and the civil M.59B the Cheetah X.
Discussing the 1944 work that led to the M.60 Marathon, the 22/06/1944 design is stated to have two 850hp Armstrong Siddeley Cougar engines, which were then under development.
I wonder therefore if Cheetahpard was an early name for the Cougar?

Edited to reflect missed information and in view of robunos' response below.

 

[robunos]

I found this, from Putnam's 'Handley-Page', page 531, the Leonides Herald chapter :-

"...having just received details of Canadair's proposed high-wing feederliner, to be powered by two 1450hp Pratt & Whitney or Wright piston engines. Sir Frederick and [designer E.W.] Grey both preferred the four engine formula, and were therefore compelled to rely on the only available engine of 800hp, the Alvis Leonides Major, a fourteen-cylinder two-row version of the nine-cylinder Leonides already flown in the H.P.R.2 trainer; the equivalent Armstrong Siddeley engine, provisionally called Cheetah-pard, existed only on paper."

So it does indeed seem that 550-580hp is too low for the Cheetapard, and that the true rating is 800hp.

@Hood; according to Wiki, the Cougar was a single-row, nine-cylinder engine, bore and stroke 5.5 x 5.5", giving 850hp for take-off, 500hp cruising:-

Armstrong Siddeley Cougar - Wikipedia

en.wikipedia.org

Also, the Cougar was under development in 1944-45, whereas the Cheetapard was still 'on paper' in 1952, ref. as above, page 530.

cheers,
Robin.

 

[Hood]

Sorry, my post was in error!! Indeed on the page before Peter Amos describes the original M.59 proposal and mentions the 585hp Cheetahpards but gives no details on the engine other than fuel consumption.

Eyeballing the illustrations the depth of the cowlings seem similar to the Leonides on the M.59A but its hard to be conclusive on that simply by rule of thumb.

1944 to 52 is a long development time, it seems no serious takers were ever found. Perhaps the low power was a sticking point for customers, the Cougar seems a more likely Leonides competitor. Of course later Cheetahpard offerings might of had more power.

 

[Schneiderman]

In his article on Armstrong Whitworth's unbuit projects (Air Enthusiast 43) Ray Williams gives a power rating of 620hp for the Cheetapard, installed in a tailless airliner concept in 1944