Short Stirling

[ThomasP]

Found some more bits of data in my notes. I have these aircraft listed as operating out of 42 Base. Unfortunately I do not remember where I got this info, but I am pretty sure most of it was from online sources.

Halifax Mk V LL130 operating as target marker / bomber
27 August 43 Night Operation against Nuremberg
bomb load: 1x4000 HC + 3x1000 MC + 5x250 TI

Halifax Mk II JB863 operating as target marker / bomber
30 August 1943 Night Operation against Munchen Gladbach
bomb load: 1x4000 HC + 6x1000 MC + 4x250 TI

Halifax Mk II JB781 operating as target marker / bomber
6 September 1943 Night Operation against Munich
bomb load: 1x4000 HC + 2x1000 MC + 4x250 TI

Found this in my notes, re Halifax being the first to use a 8000 lb HC:

Halifax Mk II R9487 operating as bomber
10 April 1942 Night Operation against Essen (~440 miles)
bomb load: 1x8000 HC + 8xFlare
Note: First Operational Test of 'Two by Four' (codename for the 8000 lb HC) Aircraft flew from RAF Middleton to target with bomb bay doors open, bombed from 15,000 ft, closed doors and returned to RAF Docking due to shrapnel damage. Total distance flown was ~750 miles and mission time was 4 hr 15 min.

 

[Shortround6]

A few random notes.

The Whole Idea of flying boats was that you had unlimited length runways.
Obviously there limits but compared with land airfields that existed in the 1930s there were opportunities that existed for engine power/weight combinations that did not exist for land planes.

The Stirling might have been membered more fondly if it reached squadron squadron status earlier.
BOTH production lines were damaged by German raids that set production back by months.

I am not sure about aircraft but the British government was rather fond of putting artificial size/cost restrictions on ships for many years and in 1930s on tanks.
Numbers mattered to most some politicians and not the actual capabilities of the weapons.

 

[33k in the air]

Found some more bits of data in my notes. I have these aircraft listed as operating out of 42 Base. Unfortunately I do not remember where I got this info, but I am pretty sure most of it was from online sources.

Halifax Mk V LL130 operating as target marker / bomber
27 August 43 Night Operation against Nuremberg
bomb load: 1x4000 HC + 3x1000 MC + 5x250 TI

Halifax Mk II JB863 operating as target marker / bomber
30 August 1943 Night Operation against Munchen Gladbach
bomb load: 1x4000 HC + 6x1000 MC + 4x250 TI

Halifax Mk II JB781 operating as target marker / bomber
6 September 1943 Night Operation against Munich
bomb load: 1x4000 HC + 2x1000 MC + 4x250 TI

I'll check out those dates for the three squadrons, although the mention of target marker makes me wonder if the heavier bombs were used by PFF squadrons operating the Halifax rather than regular squadrons.

 

[33k in the air]

One quite interesting thing I've noted in the 77 Squadron ORBs is that the route is listed for each mission. That allows for the calculation of actual flight distance to be flown, as opposed to the nominal straight-line distance from the base to target.

I did this for two missions out of curiosity.

3/4 March 1943 to Hamburg: the straight-line round trip distance would be 896 miles, but the round trip flight route distance was 968 miles, or 8% greater.
9/10 March 1943 to Munich: the straight-line round trip distance would be 1,348 miles, but the round trip flight route distance was 1,561 miles, or nearly 16% greater.

The aircraft for both was the Halifax II, with the Hamburg mission carrying a nominal bomb load of 6,200 lbs, while the Munich mission load was 4,480 lbs.


ETA: The ORBs for 10 Squadron also show the route to be flown. Anyone know of any others that list the route path?

 

[33k in the air]

Found some more bits of data in my notes. I have these aircraft listed as operating out of 42 Base. Unfortunately I do not remember where I got this info, but I am pretty sure most of it was from online sources.

Halifax Mk V LL130 operating as target marker / bomber
27 August 43 Night Operation against Nuremberg
bomb load: 1x4000 HC + 3x1000 MC + 5x250 TI

According to the serial number look-up at RAF Commands, that aircraft was operated by 77 Squadron. But the ORB for 77 Squadron does not list LL130 as being dispatched on that mission.

Halifax Mk II JB863 operating as target marker / bomber
30 August 1943 Night Operation against Munchen Gladbach
bomb load: 1x4000 HC + 6x1000 MC + 4x250 TI

According to the serial number look-up at RAF Commands, that aircraft was operated by 77 Squadron but crashed on 19 June 1943. The squadron ORB bears this out — the aircraft was destroyed in the crash.


I'm really beginning to doubt that the Halifax ever lugged a bomb heavier than 2,000 lbs and that there's a mistake in the record keeping saying that it did.

 

[ThomasP]

Hey 33k in the air,

Did some more searching online re Halifax Mk II R9487 the 8000 lb HC and found this:

At the very top of the image I think it says that R9487 was operating with 76 Squadron at the time of the mission.

Also took a look at the various Halifax aircraft data sheets. The sheets from the Mk II on show that the 4000 lb and 8000 lb were considered to be a possible load. Here is the sheet for the Mk II Srs 1A and Mk V, see under the Maximum Alternative Bomb Loads section halfway down in the left column:

(from the excellent WWIIaircraftperformance website - obviously)

 

[ThomasP]

Hey 33k in the air,

Found the website where I got the info on LL130, JB863, and JB781:

"Sorties Aug/Sep 43"

It looks like it has been updated since I originally noted the info. It now has an entry that JB863 had crashed earlier in the year, but they have not changed the SN for the aircraft flown on that mission. I assume they have no way of finding out which aircraft it actually was.

 

[33k in the air]

Hey 33k in the air,

Did some more searching online re Halifax Mk II R9487 the 8000 lb HC and found this:

View attachment 652756

At the very top of the image I think it says that R9487 was operating with 76 Squadron at the time of the mission.

Oh, I'm not seriously doubting it did, but I would like to find a Halifax squadron whose ORBs do list the bomb loads carried which did use the heavier bombs so I have something to compare to in terms of frequency to squadrons operating the Lancaster.

76 Squadron ORBs unfortunately do not list the bomb loads carried. If there's an alternative, I'd be happy to hear it!

Certainly the Lancaster II carried the 8,000-lb HC, as 115, 408, 426, and 514 Squadrons all did when operating that model. And of course the Lancaster I/III did as well (115 Squadron even lugged the 12,000-lb HC bomb on a few missions.)

 

[Greyman]

Judging by the numbers in post#60 I think you're in for a needle/haystack level search with the Halifax + 8000 lb bomb ...

 

[Geoffrey Sinclair]

Moved my response about the RN aviation to the Carrier aircraft doctrine topic.

Raids data from Air 22/203
December 1943, first Stirling IV production
22/23 Nov 1943 last bombing raid by Stirlings on a target in Germany, Berlin
11 Aug 1944, last sea mining operation by Stirlings, La Pallice.
August 1944, first Stirling V production (prototype had been produced in April)
8 Sep 1944, last bomb raid by Stirlings, Le Havre, day raid, by this stage there was only a half squadron operational, it had Stirlings until 13 September.
100 group had a Stirling squadron from 3 May 1944, fully operational from 6 June 1944, half operational from 17 February 1945, Stirlings removed on 16 March 1945.
October 1944, last Stirling III built. August 1945 last Stirling IV built, December 1945 last Stirling V built.

Pointblank and Beyond by Lionel Lacey-Johnson, appendix 8 quoting AIR 24/269.
The Lancaster fuel load in gallons was track miles divided by 0.95 plus a 200 gallon reserve.
Halifax II fuel load in gallons was track miles divided by 0.83 plus a 200 gallon reserve.
Halifax III fuel load in gallons was track miles divided by 0.80 plus a 200 gallon reserve.
Stirling fuel load in gallons was track miles divided by 0.75 plus a 300 gallon reserve.

Weights available for bombs and window, in pounds
800 track miles, Lancaster 17,200, Halifax II 11,800, Halifax III 13,360, Stirling 10,475
1,200 track miles, Lancaster 14,150, Halifax II 8,320, Halifax III 9,260, Stirling 6,625
1,400 track miles (last Stirling entry), Lancaster 12,620, Halifax II 6,600, Halifax III 7,480, Stirling 4,695
1,500 track miles (last Halifax II entry), Lancaster 11,880, Halifax II 5,470, Halifax III 6,560

10/11 March 1941 first raid by Halifax
30/31 March 1941, first 4,000 pound bombs dropped, 2 by Wellingtons on Emden

10/11 Apr 1942 first 8,000 pound bomb dropped, on Essen, by a Halifax
For the war Halifax aircraft with Bomber Command dropped 1x8,000 pound HC (in 1942) and 476x4,000 pound HC (40 in 1941 and 427 in 1942) (Air 22/203)
Halifax 4,000 pound bombs dropped from Air 14/928 and 929

3 on 15/16 Jun 41
1 on 17/18 Jun 41
1 on 23/24 Jun 41
4 on 14/15 Jul 41
3 on 19/20 Jul 41
1 on 21/22 Jul 41
1 on 25/26 Jul 41
4 on 30/31 Jul 41
4 on 5/6 Aug 41
5 on 7/8 Aug 41
2 on 16/17 Aug 41
2 on 24/25 Aug 41
1 on 28/29 Aug 41
2 on 29/30 Aug 41
3 on 31 Aug/1 Sep 41
2 on 15/16 Sep 41
1 on 30 Nov/1 Dec 41

2 on 10/11 Jan 42
2 on 26/27 Feb 42
6 on 3/4 Mar 42
10 on 8/9 Mar 42
5 on 30/31 Mar 42
10 on 8/9 Apr 42
11 on 12/13 Apr 42, interesting as only 10 aircraft credited with attacking
8 on 14/15 Apr 42
10 on 27/28 Apr 42, "includes special fillings"
9 on 28/29 Apr 42, "includes special fillings"
10 on 3/4 May 42
2 on 6/7 May 42
4 on 8/89 May 42
21 on 19/20 May 42
32 on 29/30 May 42, 16 aircraft credited with attacking.
30 on 8/9 Jul 42
21 on 13/14 Jul 42
37 on 21/22 Jul 42, 36 aircraft credited with attacking.
37 on 23/24 Jul 42, 36 aircraft credited with attacking.
24 on 25/26 Jul 42
20 on 26/27 Jul 42
28 on 39/30 Jul 42
53 on 31 Jul/1 Aug 42
22 on 6/7 Aug 42
2 on 1/2 Sep 42
7 on 5/6 Oct 42
4 on 15/16 Oct 42

RAF Squadrons by Jefford, in terms of their Halifax equipment order it was 35, 77, 10, 102, 78, 405, 158, 408 squadrons

10 Squadron received Halifax in December 1941
35 Squadron received Halifax in November 1940, first operation 10 March 1941
76 Squadron formed and received Halifax in May 1941
78 Squadron received Halifax in March 1942
102 Squadron received Halifax in December 1941
158 Squadron received Halifax in June 1942
405 Squadron received Halifax in April 1942
408 squadron received Halifax in September 1942

Changes in operational Halifax squadrons,

1 Halifax squadron operational as of 31 March 1941, 1.5 as of 30 June, 2 as of 30 July, 3 as of 31 December, back to 2 operational squadrons as of 31 January 1942, 3 squadrons as of 31 March, 4 as of 30 April, 5 as of 31 May, back to 4 as of 30 June, back to 5 as of 31 July, 6 as of 31 August, 8 as of 30 September, back to 7 as of 31 October, still 7 as of 19 December, but as of 31 December of 11 Halifax squadrons on establishment, 10 were operational, the 3 extra Halifax squadrons being 51, 77 and 419

Lancaster R5574 was used and lost by 106 squadron.

The Ted Church Web Site.

77 Squadron was main force, it did not drop Target Indicators. Looking at AIR 14/930 the bomb loads given on the blog mentioning 4,000 pound bombs are for Lancaster Pathfinders. Any loads with TI are for pathfinder, not main force.

 

[MikeMeech]

Hi

The first 8000 lb 'Super Cookie' being dropped by a Halifax of No. 76 Sqn., Pilot Officer M Renault, on Essen 10/11 April 1942 is mentioned in:
'The Bomber Command War Diaries' by Middlebrook and Everitt, page 255.
'Bombs Gone, The development and use of British air-dropped weapons from 1912 to the present' by MacBean and Hogben, page 79.
'From Hull, Hell and Halifax, An illustrated history of No. 4 Group 1937-1948' by Blanchett. pages 70-71. This also mention a Sergeant Harwood also dropping one, and that because the bomb doors could not be fully closed: "A canvas strip was used to cover one end of the open bomb bay to reduce drag."
Blanchett also mentions No. 76 Sqn. using 4000 lb HC against the Tirpitz on the 27/28 April 1942 mission. The two other Halifax squadrons, Nos. 10 and 35 carried four 1000 lb spherical mines each (also see pages 256-257 in 'Bombs Gone'). For fuller details of this raid see 'Tirpitz, The Halifax Raids' by Nigel Smith.

Mike

 

[33k in the air]

Pointblank and Beyond by Lionel Lacey-Johnson, appendix 8 quoting AIR 24/269.
The Lancaster fuel load in gallons was track miles divided by 0.95 plus a 200 gallon reserve.
Halifax II fuel load in gallons was track miles divided by 0.83 plus a 200 gallon reserve.
Halifax III fuel load in gallons was track miles divided by 0.80 plus a 200 gallon reserve.
Stirling fuel load in gallons was track miles divided by 0.75 plus a 300 gallon reserve.

Weights available for bombs and window, in pounds
800 track miles, Lancaster 17,200, Halifax II 11,800, Halifax III 13,360, Stirling 10,475
1,200 track miles, Lancaster 14,150, Halifax II 8,320, Halifax III 9,260, Stirling 6,625
1,400 track miles (last Stirling entry), Lancaster 12,620, Halifax II 6,600, Halifax III 7,480, Stirling 4,695
1,500 track miles (last Halifax II entry), Lancaster 11,880, Halifax II 5,470, Halifax III 6,560

That is very interesting information. Thanks for posting that!

10/11 Apr 1942 first 8,000 pound bomb dropped, on Essen, by a Halifax
For the war Halifax aircraft with Bomber Command dropped 1x8,000 pound HC (in 1942) and 476x4,000 pound HC (40 in 1941 and 427 in 1942) (Air 22/203)

Ah, that explains why I'm not coming across it. The 8,000-lb was evidently only ever dropped once by a Halifax.

Halifax 4,000 pound bombs dropped from Air 14/928 and 929

3 on 15/16 Jun 41
1 on 17/18 Jun 41
1 on 23/24 Jun 41
4 on 14/15 Jul 41
3 on 19/20 Jul 41
1 on 21/22 Jul 41
1 on 25/26 Jul 41
4 on 30/31 Jul 41
4 on 5/6 Aug 41
5 on 7/8 Aug 41
2 on 16/17 Aug 41
2 on 24/25 Aug 41
1 on 28/29 Aug 41
2 on 29/30 Aug 41
3 on 31 Aug/1 Sep 41
2 on 15/16 Sep 41
1 on 30 Nov/1 Dec 41

2 on 10/11 Jan 42
2 on 26/27 Feb 42
6 on 3/4 Mar 42
10 on 8/9 Mar 42
5 on 30/31 Mar 42
10 on 8/9 Apr 42
11 on 12/13 Apr 42, interesting as only 10 aircraft credited with attacking
8 on 14/15 Apr 42
10 on 27/28 Apr 42, "includes special fillings"
9 on 28/29 Apr 42, "includes special fillings"
10 on 3/4 May 42
2 on 6/7 May 42
4 on 8/89 May 42
21 on 19/20 May 42
32 on 29/30 May 42, 16 aircraft credited with attacking.
30 on 8/9 Jul 42
21 on 13/14 Jul 42
37 on 21/22 Jul 42, 36 aircraft credited with attacking.
37 on 23/24 Jul 42, 36 aircraft credited with attacking.
24 on 25/26 Jul 42
20 on 26/27 Jul 42
28 on 39/30 Jul 42
53 on 31 Jul/1 Aug 42
22 on 6/7 Aug 42
2 on 1/2 Sep 42
7 on 5/6 Oct 42
4 on 15/16 Oct 42

And that explains why I've not come across the 4,000-lb from a Halifax — it dropped nearly all of them prior to the time period I'm looking at.

RAF Squadrons by Jefford, in terms of their Halifax equipment order it was 35, 77, 10, 102, 78, 405, 158, 408 squadrons

10 Squadron received Halifax in December 1941
35 Squadron received Halifax in November 1940, first operation 10 March 1941
76 Squadron formed and received Halifax in May 1941
78 Squadron received Halifax in March 1942
102 Squadron received Halifax in December 1941
158 Squadron received Halifax in June 1942
405 Squadron received Halifax in April 1942
408 squadron received Halifax in September 1942

35 Squadron ORBs start listing bomb loads in Aug. 1942; 10 Squadron, in Sept. 1942. Neither 76, 78, nor 102 Squadron ORBs list bomb loads from Aug. through Dec. 1942; I haven't checked prior to Aug. 1942, but it is unlikely they recorded the data before then if they aren't recording it afterward. 158 Squadron has bomb loads listed from Feb. 1942 onward. 405 Squadron has partial or full information from Feb. 1942.

408 Squadron might have started receiving the Halifax in Sept. 1942, but it didn't fly its first operation with them until 1943. It flew its last mission with the Hampden on 14/15 Sept. 1942, and didn't fly into combat again until 9/10 Jan. 1943, its first operation with the Halifax (a gardening mission).

 

[MikeMeech]

One quite interesting thing I've noted in the 77 Squadron ORBs is that the route is listed for each mission. That allows for the calculation of actual flight distance to be flown, as opposed to the nominal straight-line distance from the base to target.

I did this for two missions out of curiosity.

3/4 March 1943 to Hamburg: the straight-line round trip distance would be 896 miles, but the round trip flight route distance was 968 miles, or 8% greater.
9/10 March 1943 to Munich: the straight-line round trip distance would be 1,348 miles, but the round trip flight route distance was 1,561 miles, or nearly 16% greater.

The aircraft for both was the Halifax II, with the Hamburg mission carrying a nominal bomb load of 6,200 lbs, while the Munich mission load was 4,480 lbs.


ETA: The ORBs for 10 Squadron also show the route to be flown. Anyone know of any others that list the route path?

Hi
The book 'By Day & By Night, The Bomber War in Europe 1939-45' by Ken Merrick, contains some general raid route maps, for example Leipzig on 19/20 February 1944:

Compare with the reproduction of a 4 Group route map in the book 'From Hull, Hell and Halifax':

Also from Merrick a raid route map for the Chemnitz 14/15 February 1945, when there was more 'friendly' territory to fly over:

Mike

 

[33k in the air]

158 Squadron ORB
(note that the quality is not great so the serial numbers and aircraft letter may be wrong)

13 July 1942 — Duisburg
Halifax, "B" W1164, bomb load "2 x 4,000 lb"
Halifax, "S" W1173, bomb load "2 x 4,000 lb"

21 July 1942 — Duisburg
Halifax, "C" W1215, bomb load "2 x 4,000 lb" (returned early)
Halifax, "H" W7766, bomb load "2 x 4,000 lb"
Halifax, "M" W7750, bomb load "2 x 4,000 lb"
Halifax, "K" W7745, bomb load "2 x 4,000 lb"

23 July 1942 — Duisburg
Halifax, "K" W7745, bomb load "2 x 4,000 lb"
Halifax, "E" W1108, bomb load "2 x 4,000 lb"
Halifax, "P" W7753, bomb load "2 x 4,000 lb"

25 July 1942 — Duisburg
Halifax, "K" W7745, bomb load "2 x 4,000 lb"
Halifax, "V" BB208, bomb load "2 x 4,000 lb"
Halifax, "C" W1215, bomb load "2 x 4,000 lb" (returned early)

31 July 1942 — Dusseldorf
Halifax, "H" W7766, bomb load "2 x 4,000"


405 Squadron ORB
(note that the aircraft serial numbers were not listed)

8/9 July 1942 — Wilhelmshaven
Halifax II, aircraft "R", "O", "E" and "B", bomb load "2 x 4,000"

21/22 July 1942 — Duisburg
Halifax II, aircraft "S", "B", "D" and "E", bomb load "2 x 4,000"

25/26 July 1942 — Duisburg
Halifax II, aircraft "E", "A", "S", "P", and "G", bomb load "2 x 4,000"

26/27 July 1942 — Hamburg
Halifax II, aircraft "P" and "S", bomb load "2 x 4,000"

31 July/1 Aug. 1942 — Dusseldorf
Halifax II, aircraft "M", "J", "L", "R", "T", "H", and "E", bomb load "2 x 4,000"


Looks like the reason more 4,000-lb bombs were dropped than aircraft were dispatched was because some of the them were carrying TWO 4,000-lb bombs each.


ETA: I wonder why the 4,000-lb stopped being dropped by the Halifax. I presume it was either because there was some sort of drawback to them carrying that weapon, or because the Lancaster was becoming available in greater numbers and was a better platform for delivering that particular ordnance.

 

[33k in the air]

Hi
The book 'By Day & By Night, The Bomber War in Europe 1939-45' by Ken Merrick, contains some general raid route maps, for example Leipzig on 19/20 February 1944:

Compare with the reproduction of a 4 Group route map in the book 'From Hull, Hell and Halifax':

Also from Merrick a raid route map for the Chemnitz 14/15 February 1945, when there was more 'friendly' territory to fly over:

Mike

Thanks for that. Always good to have even more reference sources!

 

[Admiral Beez]

I would like to talk about the Short Stirling,. On wikipedia I read, that it was required to have a narrow wingspan to fit into exisitng hangars back then, compromising its performance. So far so good, but then I come across this image, also on wikipedia:
View attachment 651867
I can't help but notice that the Stirling has only 89 centimeters less wingspan than the Lancaster and actually 8 cm more than the Halifax. So I am confused by the previous statement. Did they mean that the Stirling should have had an even larger wing than the others? It look bigger on the sideview.

Two other points, I read that the ceiling of the aircraft was abysmal, for example unable to fly over the alps, instead having to fly through them. On the other hand, I also read that it was surprisingly maneuverable, able to outturn heavier fighters, I assume like Ju-88 long-range-fighter variants? Are these stories true?

Looking at these pics it seems like the Stirling should have had a B-29's wingspan. Now that would have been a super high altitude platform for 1939-40. Pressurization may be necessary.

 

[Acheron]

So, the Stirling was too big for its wings(pan)?

Wasn't it also used as a transport? How did it do in that role? Given its size, it better did well, or I have to really question if it was an even decent design.

 

[MikeMeech]

So, the Stirling was too big for its wings(pan)?

Wasn't it also used as a transport? How did it do in that role? Given its size, it better did well, or I have to really question if it was an even decent design.

Hi
The Stirling gradually superseded the AW Albemarle for glider towing and parachute troop dropping for the British armed forces. For parachute operations it could carry 22 troops plus 12 containers with a range between 1,500 and 2,000 miles and a radius of action between 700 and 800 miles, which was reduced to 525 miles when towing a fully laden Horsa.
The Halifax was also used by the airborne, however, it was regarded as an 'uneconomical' when carrying troops (10 in early marks and 16 in later ones) but it was the only type that was avail;able to tow the large Hamilcar gliders with a radius of action of 400 miles and with a Horsa it was 600 miles. The Halifax could also drop Jeeps and 6 pdr guns.

The Transport Command ORBAT for D-Day is below, there were more squadrons equipped with both Stirling and Halifax aircraft by 1945:

The best books for detailed information on British airborne operations and equipment were official publications from 1951, both of which have been reprinted; the army's 'Airborne Forces' by Lt-Col. T B H Otway (IWM reprint 1990) and the RAF's AP 3231 'Airborne Forces' (Naval & Military Press reprint).

Mike

 

[YakMan]

I've often wondered why they didn't retrofit a fillet at the outer wing joint or extended outer wingtips or something just to help out, if fitting into hangars really was a problem they could have made them manually fold down easily! I have read many times in contemporary books how the Stirling climb ability and bombing altitude were badly compromised by lack of wing area.

The Stirling by the way has always been my favourite heavy bomber - such an elegant nose and that impossibly tall undercarriage - fantastic!

 

[EwenS]

Starting in the 1930's, the RAF had hangars with openings well over 100 feet, like the "C", "J" and "K" types.

It would be refreshing if publications didn't use wiki as a source of info and actually did some research.

Picking up on the issue of RAF hangar design, the largest hangars for landplanes in WW1 were designed in 1917/18 with a span of either 80 or 100 feet.

The Type A Aeroplane Shed was designed in 1924 and was erected on permanent RAF stations, mostly through to the mid-1930s when RAF expansion began. A couple were built to a slightly modified design in 1940 at maintenance bases. It had a span of 122 ft. These airfields received between 1 and 6. But of course the number of active RAF stations was much reduced in this period.

The B Aeroplane Shed had a span of 160ft but only 3 were built in total in 1927-33, on 2 airfields, plus another in 1940.

The Type C was developed as part of the RAF Expansion Scheme in 1934 for installation at the new airfields then being built. Various modifications to the design were made through to 1939, but all had a span of 150ft. Many of these Expansion Scheme airfields were meant to support the expansion of Bomber Command in the east of England.

RAF Maintenance Command built and used a number of hangar types for Aircraft Storage Units between 1936 and 1940. These were not front line airfields. There were Type D Aircraft Sheds (150ft) as well as the Type J & K (167ft) as well as various arch shaped hangars with doors not wide enough for heavy bombers.

When it comes to flying boats most of the stations had Admiralty Seaplane Sheds dating back to WW1. These were 180-200ft long with a 100ft span but importantly opened along the side facing the water rather than having an end opening.

So, if whoever drafted the B.12/36 spec dated 15 July 1936, which resulted in the Stirling, had an eye to hangar size it was either with a view to operations from airfields with the old WW1 hangars which were expected to come back into use (not sure how many), or he had no idea that the new Expansion Scheme airfields would have larger hangars. Or there is another reason, like simply not wanting the aircraft to become too large.

The more I look at this the last of these seems the most likely reason for the wing span limit, arbitrary though it may seem.