What was the Short Stirling Mk II ?

[brewerjerry]

Hi
curiosity anyone know what the strling Mk II was, presumably it existed as a project, ( otherwise theMkIII would have been a MkII )
cheers
Jerry

 

[Jemiba]

Cannot check other sources in the moment and I'm not sure if this is correct :
(from http://www.airpages.ru/eng/uk/stirling.shtml )
"Short Stirling II: Proposed Canadian production version to be built at St Hubert, PQ, by Canadian Associated Aircraft,
with 1,600 hp Wright R-2600-A5B Cyclone engines. Three Mk I airframes completed as Mk II prototypes in UK, with first
flight at Rochester August 1941. Planned production of 140 in Canada cancelled, as also was proposed Mk II production
at new shadow factory operated by Shorts at South Marston, near Swindon. One Mk II later converted to Mk III prototype. "

 

[CostasTT]

And a picture:

 

[DWG]

Shorts Aircraft Since 1900 says 140 Stirling Mk II contracted from Canada with Wright Cyclone R2600-A5Bs (1,600hp) and "one version of the Stirling II was to have twin cannon* dorsal and ventral turrets amidships, with a faired nose and pointed tail; the turrets would have been Boulton-Paul Type H (upper) and Type O (lower).' N3657 and N3711 converted as prototypes at Rochester, flown August and December 1941, but then the Canadian production was cancelled in favour of Lancasters and production at South Marston also cancelled. As far as I can tell (i.e. I'm inferring from other notes I have lying around that don't mention specific Marks), this means the Canadian production was planned to be at Canadian Associated Aircraft, which was a consortium of 3 Ontario-based companies and 3 Quebec-based (one being Fairchild) who were already building the Hampden.

On further googling I've found a reference which confirms the Canadian order was to Canadian Associated Aircraft: http://books.google.co.uk/books?id=ZpiZo5fJrCsC&pg=PA9&lpg=PA9&dq=Canadian+Associated+Aircraft&source=bl&ots=LH5ltqgx0g&sig=8U_T5GpBtomgoLhke2_1B7V5XKQ&hl=en&sa=X&ei=naEAU-GWGIPH7Aa_loC4Aw&ved=0CFEQ6AEwBg#v=onepage&q=Canadian%20Associated%20Aircraft&f=false though it doesn't say much more on Stirling, it does say they were badly behind on Hampden, which may explain why the replacement Lancaster order went to National Steel Car (later Victory Aircraft) rather than CAA.


* 20mm. There are some details of the history of the Type H and O turrets here: http://forum.axishistory.com/viewtopic.php?f=114&t=20042&start=15

 

[Bill Walker]

Molson's and Taylor's "Canadian Aircraft Since 1909" confirms that Canadian Associated Aircraft was intended to assemble the Canadian Stirlings. Production was to follow the Hampden model, with established firms supplying major components to the two CAA assembly facilities. Following the disbandment of CAA (due to the Hampden issues and the cancellation of the Stirlings) the Malton CAA plant became part of Victory Aircraft, and the St. Hubert plant passed first to Canadian Vickers for Canso assembly and then to Fairchild for Helldiver production.

Canadian aircraft production at that time was a little confusing. CAA was part owned by National Steel Car, who annoyed the government by pursuing contract work outside of government channels (B-26 and Lancaster licences were obtained without the government being fully aware, and some company money was spent on preparing for production of Stirling parts before this was signed deal), while basically screwing up government contracts for Lysander production and several smaller jobs assembling and modifying American and UK aircraft for the BCATP. The government finally had enough, and nationalized the aircraft parts of National Steel Car in November 1942, forming Victory Aircraft from the remains of this and part of CAA. The management team from Canada Car that had had great success with the Hurricane program was brought in to run the Lancaster program, again with great success.

I suspect that part of the reason for cancelling the Stirling program was National Steel Car's heavy involvement, at a time when their senior management was not trusted by the government.

 

[DWG]

Fascinating stuff. I knew about the Canadian Stirling production being cancelled in favour of the Lancaster, but had always assumed that was simply the same process of Stirling falling out of favour that happened in general. The reality is much more revealing WRT Canadian production.

 

[Stargazer]

Very, very interesting stuff, Bill Walker. Thanks for sharing this little-known side of Canadian aviation development!

 

[Bill Walker]

As I said, all this "drama" may have been part of the reason. I think by 1942 everybody realized the Lancaster was a better aircraft than the Stirling.

Engine choice was also a factor in Canadian decisions at this time. A joint UK/US board in Washington assigned North American war time production, and Canada generally came up last - the Anson Mk. II is proof of this. I wonder if US built Merlins were more available than US built Wright R2600s in 1942?

 

[JFC Fuller]

I found an original copy of the attached photo of the Boulton Paul Type O turret on a Stirling II model in the UK National Archives. It was a manned turret with the gunner lying prone, the large lump protruding downwards was a retractable knee well for the gunner that would automatically retract when the gunner left the turret.

The drag when turned to beam was an issue* but the biggest headache seems to have been the torque on the barrels causing bending as the turret trained resulting in unacceptable dispersion during firing. Bolton Paul were working on faired, floating barrel sleeves to try and overcome the problem but the ultimate solution seems to have been the shorter barrelled Hispano Mk.V as used in the Bristol B.17 turret installed on the Lincoln and Shackleton.

An armament option that came much closer to fruition was the FN.33 quad .303" mid-upper turret for the Lancaster and Stirling but that required considerable modification in the former and never went anywhere either.

*There is a note in either BSP or another book about the Boulton Paul P.92 turret fighter being expected to experience a sudden increase in drag when it's four Hispano turret was trained to beam as well

 

[Hood]

Interesting info.
The Type O looks fairly aerodynamic but I'm sure it would be pretty draggy when trained to either beam.

 

[SlickDriver]

Northrop P-61A and B Blackwidow had a similar problem with their four .50 cal machine gun turrets. They were removed from later models.

 

[Colonial-Marine]

Supposedly a common fix on those early P-61s that had turrets (many didn't) was to simply lock the turret in the forward position. Later on the problems were corrected it would seem.