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Notes

 

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FFVS B24 Havssula ASW (AS7) and sub-variants

The story which didn't happen ... outside Atlantic Air Combat
 

By end of the Korean War, it had became clear for Sweden that more trouble was looming up in Europe, especially with the USSR going ahead with their plans to build up a fleet of aircraft carriers.  While the Baltic is not exactly a place to safely operate a carrier, it does offer additional air capabilities to reach out at sea and protect the mainland

But in addition of offering addtional assets on their Eastern flank, Sweden saw the potential danger also coming from the North with Soviet troops coming through neighbouring Finland or even Norway.  Also, an increasingly strong and potent Soviet Navy was a clear threat to Sweden's shipping lanes in the Artic and North Seas (Norway, Scotland, Iceland) and accross the Atlantic (Canada, United States).  So, while the debate had been going on for some time

regarding whether or not to scrap, maintain or develop their "blue water" navy (re: the three Sverige class, and the two Tre Kronor class cruisers), Sweden eventually decided early 1956 to strengthen their navy, and acquire aircraft carriers with the main purpose to enhance their anti-shipping capabilities in the Artic, and, to a lesser extent, provide a platform for anti-submarines aircrafts.  This decision lead to the A2 HMS Gotland and A3 HMS Lappland, the story of which is covered elsewhere in these ... fantasy Notes.

ASW - Anti-Submarine Warfare and AEW - Airborne Early Warning
Contrary to the trend emerging in the second half of the 1950s, the Swedish Navy was reluctant to rely on helicopters to perform ASW missions.   They weren't ruled out, but somehone it was felt helicopters were too slow to rapidly deploy in a given area, especially as the intended ASW assets were to be used both from carriers and from shore bases..  On the other hand ASW helicopters like the HSS-1 Seabat (or its British equivalent the Westland Wessex HAS-1) or the HSS-2 Seaking under development, were able to drop a sonar in the water while an aircraft had to rely on sonobuoys dropped in a given area to try to identify and locate submarines.  Considering the development of helicopters to come, one could say the Swedes might have been better inspired to acquire Westland Wessex and, later, Whirlwind, but they sticked to the aircraft idea.  Then size is a problem on a diminutive carrier, either on the flight deck or in the hangar.  With the exception of WWII vintage aircrafts, the Navy looked at all available options, at least those readily available as it was never considered to rely on a national solution and developp a new aircraft to tackle this specific issue or only as a licence contractor of an existing design.

Technically, the American S-2A Tracker was probably the best option and it is no accident if in time the Dutch, Canadian and Australian Navies opted for this particular plane.   With both an AEW (E-1B Tracer) and a COD (C-1A) version offering outstanding performances in terms of detection range (AEW), ferry range, loiter time or transport capacity, the American aircraft was tempting and had many a supporter.   However, while the S-2A was available, the same could not be said for the two other sub-types.   Not that the US was reluctant to make the AEW technology available to Sweden, but they hardly had enough airframes for their own needs, so giving up the quantites Sweden was looking for was plain impossible, and it would be several years before Grumman could squeeze in yet another foreign order.  Canada was producing the S-2A under licence and could cope with an additional order, but the nor the E-1B Tracer nor the
C-1A Trader were scheduled for production with them (although a cargo version of the S-2A was proposed).  Then, two other factors played a role against the Grumman product : 

the aircraft was propelled by piston engines, imposing hasardous volatile high octane fuel on board the carriers - ideally speaking they would need to be re-engined with turbine engines

the foot print of the Grumman aircraft was judged excessive; basically a single S-2A Tracker would use the space of two Fairey Gannets, which could be stored side by side in the hangar while the S-2A was almost occupying the full width available.   Retrospectively, this view could be seen as over pessimistic, as Argentina, Australia, Brazil, Canada and the Netherlands did happily operate Tracker from their own Colossus/Majestic carriers, although without a fighter/attack wing on board.

 

 

These consideration sort of shortlisted the Fairey Gannett against the French Alizé, as no AEW version had been developped for the latter.   The particular crew arrangement preventing proper pilot training, a trainer version would also needed to be acquired, thus copying what the Admiralty had done themselves.

It is worth noting that at the same time, the FAA was relinquishing their own ASW aircrafts in favour of helicopters..  However, having been scrapped almost immediately not enough airframes remained available.  The AEW3 was still in production, although a very different aircraft under many aspects and COD4 airframes were too few in number for any to be handed over to anyone.  With Westland, who had taken over the Fairey company, only looking forward the end of the production line, their enthusiasm for re-opening one for yet another batch of the AS version was rather limited and nearly begged the Swedes to take over a licence production as a favour.   Saab being defintely too busy with their own products, and  Kungliga Flygförvaltningens Flygverkstad i Stockholm (FFVS) being essentially through with the developpment of the J23, they were assigned the challenge, with STAL to look after the production of the AS Double Mamba engine.  

A couple of AS4 airframes were acquired but the FAA could only loan an AEW3 version for a little time as they were all pressed hard in operations.   The same applied to the trainer and the COD versions, with such types only making a brief visit to Sweden for inspection.   However, all the neccessary drawings and what remained as production tools, together with a couple of old airframes were handed over to FFVS, in particular WN345 which had been used to test the installation of the last iteration of the Double Mamba engine, and WE488 which was the third prototype of the AS1 version dating from the late fourties.

FFVS had been astounded by the huge discrepencies between the Gannett airframes : wings, fuselage, landing gear...   With as close as free hand given by Westland to tinker with the Gannett design, the Swedes took up the matter seriously in order to explore if a common airframe could cope with various missions.

Powerplant
With the ancient versions of the Double Mamba engine being out of production, the Swedish aircrafts would have to standardize on the latest version of the engine.  Not a bad thing in itself, and STAL was even more pleased to discover that Armstrong Siddelley had been working on yet another version, although not proceeded with by lack of funding by the Fleet Air Arm.   Not essentially different, it did save a little on weight, and offered a sligtly reduce power compared to the 3875hp ASMD.4 version.  But with this last iteration AS had now reach a SFC close to the Rolls Royce Dart which was quite an achievement from the former figures.  And since it could run on a large variety of fuel, including diesel from the ship's main tank, it did offer a great advantage.  In effect, STAL entered the production of what AS would designate as the ASMD.5, rated at 3825shp.

Airframe(s)
The AEW3, thus still in production in UK, differed from the original AS variant in many aspects, with a slightly different pair of wings incorporating pylons for 100gal (454l) drop tanks, a taller landing gear, a higher tail and a very different fuselage with totally different crew accommodations.

One aspect which didn't match the Swedish requirements at all was the lack of ejection seats which was considered as totally unacceptable.   This called for some significant redesign work, which lead FFVS away from simply licence production/assembly of an existing design.  The Gannett having been initally designed for a crew of two before a change in requirement lead to the Gr17 version accommodating four.  That was back in 1949 but the requirement of ejection seats preventing the installation of the two radar operators tucked down in a narrow cabin, this ancient layout was revived, with either the ASW or AEW team located in the "back office", each crew under individual canopies.  This freed the second cockpit behind, although this co-pilot position was nevertheless equipped with repeaters and thus a second set of flight controls.   Flying hours were long in the Gannett, and while the FAA seemed to have been content with single pilot operations, the Swedish Navy thought otherwise and didn't miss the opportunity offered by the new setup.  This allowed for either the pilot or the system operators workload to be shared and also made each airframe available for training purposes, rendering a specific type unnecessary.

While some of the construction jigs were delivered, most had to be reconstructed and FFVS having had the opportunity to look at all airframes, managed to create jigs wich could be adapted in order to produce different fuselage sections.  It would take weeks to change from one set of specs to another, but at least it was possible.  Although the jigs handed over by Westland regarding the wings were those of the AS4 rather than a copy of the AEW3 version, it was adapted to cater for the higher landing gear typical of the AEW version.  The same applied to the taller fin developped for the AEW3.  In the end, only the lower part of the fuselage would visually distinguish the two new types of airframe.   Ironically, the original access door to the back AEW crew compartment was retained, just to avoid redesigning the area.  If not for crew, it did gave maintenance personnel an easy access to cockpit instruments and equipment !
 

ASW - Anti-Submarine Warfare - B24 Havssula AS7
Besides a much more powerful engine and the new crew arrangement, the B24 Havssula, known with Westland UK as the Gannett AS7, was essentially similar to the Gannett AS4.   Weapons load only differed slightly as the new engine allowed the aircraft to take off with a full internal and external weapons load rather than being restricted by maximum take off weight.   The two wing pylons were stressed for military loads of up to 1000lbs.  It that was the only change made, but one with dividend as it now allowed the carrying of 140gal (454L) fuel tanks rather than the original 100gal tanks.

But these pylons were adapted for the carrying of various military loads, including bombs, torpedos, heavy depth charges, gun or rocket pods and even a pair of AIM-9B Sidewinder missiles for self-defense.

Additionally, the wings could carry up to 16 HVAR.   While the Swedish Navy was already working with the heavier Bofors 135mm, the Swedish manufacturer acquired rights to produce the Brithish 76mm RP3 and the 2" FFAR rockets and their associated 32 rocket pods for either the Havssula or other carrier attack fighters.

Image - FD scale - ARMAMENT

AEW - Airborne Early Warning - S24 Havssula AEW8
With thus a revised crew arrangement, the S24 Havssula (Gannett AEW8 in Westland terminology) was a copy of the British made AEW3, with the same US radar dating from the Douglas Skyraider.  The Swedes didn't try to re-invent the wheel and although not the most up-to-date equipment, they made themselves happy with it relying on Ericsson to fine tune a new ECCM suite in due course.

The S24 version was thus unarmed.   But as it shared exactly the same wing as the AS7 version, theoretically it could carry the same loads.   In practice however, besides 140gal auxilliary fuel tanks, the Havssula would only carry AIM-9B self-defense missiles but the option was rarely used

COD - Carrier Onboard Delivery - Tp24 Havssula COD9
With the carriers intended to mainly operate in the Artic Sea, the Sea of Barents and the North tip of the North Sea, carrier onboard delivery was thought to be a necessity rather than an extravagance.   While both Norway and Finland, secretely agreed to have unarmed Swedish planes crossing their respective airspace, significant range/endurance was necessary to at least reach the Spitzberg landing strip, either for a stop over or for diversions.  Depending on the point of departure, either the Frösön Air Force Base in the South,
Frösön AFB in the West or Kiruna airport in the North, it meant a 630nm (1170km) to 780nm (1450km) flight.   Add an hour loiter/diversion flight time and it actually meant the COD airplane the Swedish Navy needed should have something like a 850nm (1574km) range.  There was no obvious solution.   Like the E-1B Tracer, the US Navy couldn't make C-1A Trader available to foreign customer.  The loan of a couple of aircraft wasn't a problem but Sweden was looking toward something like two dozen airplanes or by the end of the fifties, the US Navy themselves wished they had that kind of number for their own use !

Conscious of the Swedish wish to avoid any petrol on their carrier, DeHaviland of Canada did suggest to adapt the Rolls Royce Dart engine to a cargo version of the Tracker.  Actually, it would be stripped down version of the S-2A rather than a specially designed aircraft, but at least the plane would have the required range which a simple COD version of the Ganned would barely have.  With the S-2A airframe being a little shorter than later version and C-1A Trader, it would be compatible with the size of the carrier elevators (hence a similar choice by the Canadian Navy) and the solution found many advocates within Swedish Naval circles and up to the Government - a realy lobby would be a fairer assessment.

At FFVS no one would pretend this to be a nonsense as the type offered the requested performance, but the Navy initial reaction to FFVS suggesting a dedicated COD version rather than a makeshift arrangement of the Havssula was a bit strange, as they were told the Navy could not see an AEW airframe turned into a proper transport aircraft, and they referred to the less than satisfactory British COD4 aircrafts (based ... on a ASW airframe !) to justify their refusal.   As FFVS never suggested a particular airframe base for the exercise, it seemed a bit odd that Naval officials would rule out a prospect on the ground of a bias they formulated themselves...

Anyway, as the subject was lingering with a decision being reached, FFVS took advantage of the production interruption to allow a switch from the ASW to the AEW airframes and adapted fuselage jigs to produce two slightly different airframes.   This was done almost secretely to avoid upsetting an unwilling client.   The new fuselage was somewhat wider after of the second cockpit, only getting narrower as it closes the tail.

A new vertical twin tail was designed, essentially to ensure the fatter if not wider fuselage would not induce lateral instability.   A shorter landing gear was adopted to allow a loading ramp of a reasonable size to be installed in the back of the aircraft.   The ASW fuselage cross sections were thus used, but with the weapons bay totally enclosed.   Actually, the volume occupied by the fuselage main fuel tank being needed for cargo, the weapons bay was turned into a huge fuel tank, making the total internal fuel capacity jump to 700 gallons.

In the end the new airframe offered a sizeable albeit narrow cargo hold.  With both the loading ramp and cabin floor  equipped with rollers, loads could easily be handled - a far cry from the US-2A Cargo Tracker side door !.   Range being a critical issue, the combination of increased fuel capacity, both internal and external, and the much better fuel consumption of the ASMD5 engine, finally addressed that particular aspect.  Depending on where the flight would start, the Tp24 could reach : 

North
Kiruna
West
Frösön

South
Såtenäs

Torshavn (Faroe)
Lerwick (Shetlands)
Lamjmljlj (Spitzberg)
North Point (USAF base in North Greenland)
Keflavic (Iceland) 
Several locations in Ireland itself

FFVS then worked on the various ways this volume could be used and soon rails were added on the floor to fix passengers seats.   Unlike the real C-1A Trader but similar to the Canadian proposal, the narrowness of the fuselage didn't allow for two seats abreast naturally, but against the end wall on the "E" section where two seats would face rear.   However cramped in a 31in pitch, the setup did allow for up to 7 passengers to be transported - again a better fit than the Canadian proposed fix on the S-2A.

To allow a mix of cargo and passengers to be transported at the same time, FFVS devised a dismoutable shock resistant bulkhead to be fixed on the "D" frame thus enclosing any cargo before adding seats, even if a door provided access to that area - an ideal solution when the cargo is essentially made of post bags..  Cargo was then limited to a single US type 45x35.5 pallett or a couple of 900x700mm pallets (whenever pallets were used) but with the bulkhead being installed or removed in less than 20 minutes, this mixed arrangement was considered as a bonus.  Access to the cabin was exclusively through the loading ramp although FFVS did find a use to the original AEW3 access doors on port and starboard as they were made into jettisonable emergency exits.

As such, this bulkhead created a separate compartment and with the Swedish Admiralty trying to lobby the Government into procuring Dart propelled Canadian made Cargo-Tracker someone at FFVS suggested to turn the area into a lavatory with a cassette type equiment to tease Admirals into reconsidering their position.   It only had been a humourous remark made by one of the workers but could indeed a VIP version of the Havssula tease reluctant Admirals away from their Canadian connections ?  A local caravan manufacturer was approached to give the area a proper look and soon a modular assembly was moulded and fitted to the second prototype.   Again, care had been taken to allow this alternative setup to be a dismountable one, and at least in factory surroundings, it only took about an hour to install.  Covering floor pannels, sliding into the seat rails adding to the simple but neat looking fuselage insulating pannels, the arrangement did give the then four passengers cabin a very different appearance indeed !

In less than three weeks, what started as a private joke turned the second prototype into a pocket airliner.   But the assembly of two additional airframes at the cost of FFVS did not remained unnoticed for long, and soon naval officials came over to patronize FFVS management about loosing time and money on unwanted products.   They didn't even want to have a look at it.   Well not before ex-Fairey engineers, especially H.E. Chaplin the original designer, travelled from Britain to have a look for themselves.   They couldn't believe the rumor nor could refrain from seeing it with their own eyes.   This unscheduled - but very welcome - publicity somehow forced both the Navy and the Government to review the design, albeit reluctantly.   But admittedly this FFVS private exercise was all but a joke.  All right, the fuselage was narrow and ceiling low but it could nevertheless absorb 4 US type pallets.  And it naturally offered type commonality with other variants of the Gannet with all its associated advantages.  So after all, FFVS hadn't waisted neither time nor money, and what they had arrived at could be compared to the US-2A Cargo Tracker
Comparative

Engine

-

Crew

Length

Span

Height

Weight

Freight

Pass

Speed

Fuel

Range

Ceiling

Specifications

Type
Power

SFC
lb/HpHr

 

 

    -    
Folded

 

Empty
Max

Max

Pass
Cargo

Cuise
Max

-

Std

-

C1A Trader

WR1820
1525hp

  x2  
0.600

3

42'02"

69'08"
27'00"

16'04"

18750lb
24624lb

    -    
3500lb

    8    
-

142kts
220kts

518gal
---

1130nm

24800ft

US2A Tracker

D6-510
1576hp

  x2  
0.581

3

42'02"

69'08"
27'00"

16'04"

18794lb
24624lb

    -    
3500lb

    5    
-

142kts
220kts

518gal
---

1167nm

24800ft

Gannet COD9

ASMD5
3825hp

  x1  
0.590

2

44'

54'04"
13'09"

15'07"

13512lb
26000lb

    -    
4368lb

    7    
2628lb

217kts
260kts

700gal
+380gal

948nml
1103nm

25000ft

Optional.layout

-

-

-

-

-

-

-

-

    4    
3468lb

-

-

-

-

So questions soon fused : could the aircraft be turned into an air ambulance ?   Could the Tp24 drop paratroopers ?   Yes, it could do both, although the installation of stretchers would require a awful lot of bracing, and should the Tp24 be ordered, the two protypes would be offered right the way to the Navy as FFVS had no need for a company aircraft and they would be busy assembling the AEW8 before they could switch to the production of that variant.  The Ministry of Defense thus reckoned their mistake, accepted the gift and ordered three dozens of Tp24 with their various kits, excluding the VIP version though.  But since one did exist...   While they might not desserve the privilege, considering their initial misgivings, humourous Admirals thought they could nevertheless indulge into it ! 

Image below to be replace by loading animation














Specifications

Real

Real

Real

Real

Real

Real

Real

Real

Real

AAC

AAC

AAC

Variants

Q

Gr17

AS1

T2

AEW3

AS4

COD4

T5

ECM6

ASW7

AEW8

COD9

First flight

1949

1949

1953

1954

1958

1958

??

1957

??

1960

1960

1961

Crew

2

4

3

3

3

3

2

3

3

4

4

2

Passengers

-

-

-

-

-

-

1

-

-

-

-

7

Wing.span

54'04"

54'04"

54'04"

54'04"

54'07"

54'04"

54'04"

54'04"

54'04"

54'04"

54'04"

54'04"

Length

43'

43'

43'

43'

44'

43'

43'

43'

43'

44'

44'

44'

Height

13'9"

13'9"

13'9"

13'9"

16'9"

13'9"

13'9"

13'9"

13'9"

16'9"

16'9"

16'9"

Engine

ASMD1
2950hp

ASMD1
2950hp

ASMD1
2950hp

ASMD1
2950hp

ASMD4
3875hp

ASMD3
3035hp

ASMD3
3035hp

ASMD3
3035hp

ASMD3
3035hp

ASMD5
3825hp

ASMD5
3825hp

ASMD5
3825hp

Speed.max.sea.level

269kn

269kn

269kn

269kn

267kn

260kn

260kn

260kn

260kn

270kn

267kn

270kn

Ceiling

25000ft

25000ft

25000ft

25000ft

25000ft

25000ft

25000ft

25000ft

25000ft

25000ft

25000ft

25000ft

Range

600nm

600nm

600nm

600nm

700nm

575nm

575nm

575nm

575nm

1003nm

1003nm

1103nm

Weight.empty

15069lb

15069lb

15069lb

15069lb

?

14528lb

14528lb

14528lb

14528lb

14528lb

??

13512lb

Weight.crew

800lb

1600lb

1200lb

1200lb

1200lb

1200lb

1200lb

1200lb

1200lb

1600lb

1600lb

800lb

Weight.fuel.main

4560lb

4560lb

4560lb

4560lb

4560lb

4560lb

4560lb

4560lb

4560lb

4560lb

4560lb

5320lb

Freight.Max

-

-

-

-

-

-

3158lb

-

-

-

-

4368lb

Armament.Internal

-

-

2000lb

2000lb

-

2000lb

-

2000lb

-

2000lb

-

-

Armament.HVAR

-

-

16xRP3
82lb

=1312lb

-

=1312lb

-

=1312lb

-

=1312lb

-

-

Armament.Pylon

-

-

-

-

2x100gal
1720lb

-

-

-

-

2x140gal
2000lb

2x140gal
2000lb

2x140gal
2000lb

Weight.Total?

20429lb

21229lb

24141lb

24141lb

?

23600lb

23446lb

23600lb

20288lb

26000lb

?

26000lb

Weight.Max

19600lb

19600lb

19600lb

19600lb

26000lb

23446lb

23446lb

23446lb

23446lb

26000lb

26000lb

26000lb

Load option

 

 

 

 

 

 

 

 

 

 

 

 

4 passengers

 

 

 

 

 

 

 

 

 

 

 

900lb

Freight

 

 

 

 

 

 

 

 

 

 

 

 3468lb














Production

3

1

181

38

45

75

6

11

9

104

30

36














 
 

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