What if all three Canadian Services bought Sikorsky S-61 in 1963?

[riggerrob]

OTL in 1963, the Royal Canadian Navy received their first Sikorsky CH-124 Sea King Helicopters. They flew from Canadian ships for more than 50 years. I greased and refuelled Sea Kings on the flight decks of HMCS Athabaskan and HMCS Iroquois. I also washed innumerable GE-T58-8F engines.
Meanwhile both the Royal Canadian Air Force and Canadian Army bought Boeing/Vertol/Piaseki CH-46 helicopters powered by the same GE-T58-8F engines.
CA Voyageurs hauled troops and trash until replaced by CH-47 Chinook, heavy-lift helicopters during the 1970s. Then Voyageurs were converted to the RCAF Labrador search-and-rescue configuration.

What If all three Canadian services bought the same basic S-61 airframe in 1963?
RCAF could operate near-stock Sea Kings for SAR, but the Army would want S-61R variants with rear ramps.
Would a common airframe simplify logistics, maintenance and training?

How would a common airframe affect Chinook purchases, Cormorant purchases or S-92 (Sea King replacement) purchases?​

 

[_Del_]

Why not just use Phrogs for all three services? Couldn't be too hard to stuff ASW gear into a Phrog. Basically anything you could stuff in a Sea King should be able to fit in the Phrog. And has better lift power/lower disc loading for replenishment or army-lift requirements.
Then you can replace them all with S-70 variants on the other end of the timeline.

I don't know that it would affect the Chinook buy. The Chinook is a much heavier, more capable helicopter. Might help familiarization and standardized training between the two tandem-rotor designs.

 

[riggerrob]

Dear Del,
What is a Phrog?

 

[jstar]

Dear Del,
What is a Phrog?

CH-46 Sea Knight, CH-113 in Canadian service

 

[apparition13]

Why not just use Phrogs for all three services? Couldn't be too hard to stuff ASW gear into a Phrog. Basically anything you could stuff in a Sea King should be able to fit in the Phrog. And has better lift power/lower disc loading for replenishment or army-lift requirements.
Then you can replace them all with S-70 variants on the other end of the timeline.

I don't know that it would affect the Chinook buy. The Chinook is a much heavier, more capable helicopter. Might help familiarization and standardized training between the two tandem-rotor designs.

You'd need an ASW version, while there was eventually a cargo/utility Sea King (the Commando). But even if there was, would it fit in the Sea King hangars? Or have space to land on the flight deck with two rotors?

Now for extra points, the S-67 Blackhawk attack helicopter is a Sea King with a narrow fuselage. More commonality.

 

[_Del_]

I just looked it up and the Swedes bought an ASW version.

Boeing-Vertol hkp4b

Operators, Versions and serials of the Boeing Vertol hkp4b helicopter

www.helis.com

So, not impossible.

Hangar space at sea might indeed be an issue. Doubt the Canadians go for the Blackhawk without an American buy, but that's a fun what-if, too.

 

[Apophenia]

In the full spirit of what-if ... below is a Canadian Sikorsky CH-124B Labrador of 408 Tactical Helicopter Squadron. As the white markings show, this Labrador was deployed for Operation KINETIC (NATO's Op JOINT GUARDIAN). Six 408 TacHel Labradors arrived in Kosovo in July 1999. Note that this helicopter has full 'combat' kit fitted - nose-mounted Wescam 16 E/O turret, 'Aircraft Survivability Equipment' (sensors, chaff dispensers, etc.), and a window-mounted C6 GPMG (portside, not visible here).

The CH-124 fleet was divided between four distinct types. The CH-124A and CH-124C Sea Kings were Sikorsky S-61s assembled in Toronto by DHC for the RCN and Canadian Coast Guard, respectively. The CH-124B and CSR-124 (later redesignated CH-124S) Labradors were Sikorsky S-61R variants assembled in Fort Erie by Fleet Aerospace. The CH-124B was a medium utility helicopter for the Canadian Army. The CSR-124/CH-124S was the Canadian Forces' aerial search-and-rescue aircraft.

Deliveries of CH-124A and CSR-124 variants to the Navy and RCAF SAR flights commenced in 1963. The CH-123B for the Army and CH-124C for newly-formed CCG began arriving in late 1964.

 

[Pioneer]

In the full spirit of what-if ... below is a Canadian Sikorsky CH-124B Labrador of 408 Tactical Helicopter Squadron. As the white markings show, this Labrador was deployed for Operation KINETIC (NATO's Op JOINT GUARDIAN). Six 408 TacHel Labradors arrived in Kosovo in July 1999. Note that this helicopter has full 'combat' kit fitted - nose-mounted Wescam 16 E/O turret, 'Aircraft Survivability Equipment' (sensors, chaff dispensers, etc.), and a window-mounted C6 GPMG (portside, not visible here).

The CH-124 fleet was divided between four distinct types. The CH-124A and CH-124C Sea Kings were Sikorsky S-61s assembled in Toronto by DHC for the RCN and Canadian Coast Guard, respectively. The CH-124B and CSR-124 (later redesignated CH-124S) Labradors were Sikorsky S-61R variants assembled in Fort Erie by Fleet Aerospace. The CH-124B was a medium utility helicopter for the Canadian Army. The CSR-124/CH-124S was the Canadian Forces' aerial search-and-rescue aircraft.

Deliveries of CH-124A and CSR-124 variants to the Navy and RCAF SAR flights commenced in 1963. The CH-123B for the Army and CH-124C for newly-formed CCG began arriving in late 1964.

Yes, I like the notion of derivatives of the Sikorsky S-61R being used for SAR, ASW and transport.
Is/was the S-61R more stable in water when compared to the S-61/SH-3? Surely the S-61R fuselage offers more usable space?
Time frame when did the S-61R enter production, when compared to the S-61/SH-3?

Regards
Pioneer

 

[Apophenia]

The prototype S-61R flew in June 1963 but the USAF had already placed orders (IOC for the CH-3C was sometime in 1964). Of course, speed of production in Canada would depend upon whether this represented simple assembly of Sikorsky-supplied components or a full license deal. If the latter, I envision the work being broken up by region.

If, as given in my backstory, the S-61 was assembled by DHC and the S-61R by Fleet, ... who supplies the parts? Doubtless, much of it would come from Connecticut. But, under the Defence Production Sharing Programme, at least some of the components could be licensed by Canadian firms - the usual pattern was the major portion going to Canadair in Montréal, QC. My bet would be additional work going to Fairey since they had plants in both Dartmouth, NS and Sidney, BC.

Stability on the water: You see photos of AMI Agusta-built AS-61Rs in the water. However, since the S-61R lacks the Sea King's outrigger floats, I'd guess that the 'R would be less stable on the water.

I'm not sure about comparative usable interior space. Having a rear ramp has certainly proved useful for the SAR CH-149s and would have to speed battlefield egress for troops.

I should mention that, for my little backstory, I jumped ahead to post-Unification designations. In reality, early designations would likely have been CHSS-2 (RCN), S-61R (CCG), CUH-3 (CA), and CSR-124 (RCAF SAR).

Going back to riggerbob's original questions ...

Would a common airframe simplify logistics, maintenance and training? Definitely. But the full benefits of commonality probably wouldn't be realized until after Unification. Of course, the GoC would have had the option of setting up some form of 'joint' helicopter procurement, support, and maintenance organization ahead of time to reap those benefits from the outset.

How would a common airframe affect Chinook purchases, Cormorant purchases or S-92 (Sea King replacement) purchases? I think that would depend upon the nature of the original procurement. If Canada took on a full license - for potential development as well as construction - there would be the option of resumed production.

In OTL, the Sea King Replacement project stalled because there really wasn't anything to replace the CH-124 with ... other than newer Sea Kings. But what if Canada was in a position to simply restart production with Westland-style upgrades? That would've been the path of least resistance for the SKR project in 1977. So, let's say that contracts for SKR are signed in 1983 with deliveries of replacement airframes in 1985-1988. Likewise, for OTL's 1994 Maritime Helicopter Project, the earliest new-build S-61s would still be less than a decade old.

What would the effects be? OTL's 1985 New Shipboard Aircraft requirement would be being satisfied before it was ever formulated. So, no combined New Shipboard Aircraft Project/New SAR Helicopter Project would ever have happened either. Obviously the S-61/S-61R format eventually becomes dated but a range of upgrades and updates were possible. For example, as T58 supplies dried up, switch to the more powerful, British-made version - the 1,660 shp Rolls-Royce Gnome H.1400-2 (and maybe Westland's 6-bladed tail rotor?). Further on, more modern engines would have been feasible ... and maybe even with Canadian content.

Note that Canada's current large helicopter fleet has no engine commonality with the fixed-wing fleet. For example, the new FWSAR aircraft could have been a GE-powered CASA CN235 for some commonality with the CT-7s of the co-based CH-149 fleet. Instead, DND went with PW127-powered C295s for FWSAR. Meanwhile, PWC has never managed to develop a turboshaft derivative from its PW12x family. Now imagine an MLU for the 1980s-vintage S-61/S-61R fleet with new 'PW127TS' engines, composite rotor blades, 'glass' cockpits, etc. ...

 

[riggerrob]

Good points dear apophenia,

The first Vertol 107 (Voyager) flew in 1958.
The first S-61 Sea King flew in 1959.
The first S-61R flew in 1963.

I suspect that even when folded (USMC pattern), Vertol 107/CH-46 was too big for RCN Destroyer Escorts (DDE). A folded Vertol 107 is 45 feet long by 15 feet wide.
Sorry that I do not know the folded dimensions of Sea Kings, but know that the 64 rotor diameter exceeds the beam of DDH 280 class destroyers. Even when folded, a pair of Sea Kings require a hangar the full width of the ship. Those hangars are also quite tall and catch a lot of wind. The large side surface and high centre of gravity contribute to rolls as much as 45 degrees! I have experienced 40 degree rolls aboard HMCS Iroquois that quickly exhausted sailors.

I am not sure about the stability of S-61R on the water.

On the subject of stability on the water. It may not be clear from photographs, but Sea King aluminum sponsons contain huge wheel wells, which halve the amount of floatation. Ergo, most Sea Kings were fitted with emergency floatation bladders on the outboard side of the aluminum sponsons. These inflated to roughly the same size as the aluminum sponsons, doubling roll stability.
Civilian S-61Ls had double-sized aluminum sponsons.
Many British naval helicopters had emergency flotation bolted to the outboard ends of main wheel axles.
Also note that Canadian Labrador and Swedish CH-46 had huge fuel tanks bolted to their stub-wing sponsons.
I suspect that RCAF SAR S-61R would receive similar, double-sized sponsons/fuel tanks.

A Canadian Sea King navigator told me an amusing anecdote, in 1984. He and some other Canadian aircrew had recently visited the Sikorsky factory to review the new S-60 Sea Hawk. They admired its simplified maintenance and improved performance but grumbled about how its tiny cabin was unsuitable for the "admiral's barge" ... er .... cross-decking the padre on Sunday mornings .... er .... long range SAR role ... er ... cross-decking cargo role. Yes, that is it: cross-decking cargo. When a Canadian suggested building a SH-60FH (Fat Hawk), Sikorsky engineers politely chuckled!
A few years later, Sikorsky announced that they were developing the S-92 which is essentially an S-61R fuselage hung under SH-60 rotors. S-92 incorporates a cargo ramp under the aft fuselage and was adopted as the Sea King Replacement.

Yes, I mentioned a long-range SAR role for embarked Canadian Sea KIngs. On a few occasions, Canadian ships were the closest to civilian ships in distress and rescued passengers with their personnel hoists. All RCN Sea Kings had personnel hoists permanently fitted above cargo doors.

As for upgrades - like Westland's six-bladed tail rotors - .... After the supply of original - American-made - tail rotor blades dried up, Canadian Sea Kings got five Westland tail rotor blades bolted to the their stock tail rotor hubs. I watched them doing hover trials at CFB Shearwater. New Westland-built blades looked the same to maintainers.

OTL all RCN Sea Kings were assembled at United Technology's factory near Montreal. They just bolted together parts made by Sikorsky. They hoped to assemble more S-61s for civilians, but those contracts never came.
ATL I can forecast Sikorsky sub-contracting for simple, sheet metal components, but keeping drive train production in house. That would see Canadian Sea King sheet metal production farmed out to Canadair, Fleet, Bristol, etc. ... whichever federal riding needed to buy a few more votes. That would allow politicians photo opportunities beside, big, shiny, impressive pieces of aluminum airframes. Though it makes sense to only use 1.5 sets of jigs to build all the fuselages. Stock forward and mid fuselages would be build on one set of jigs with the two different aft fuselages built on separate jigs and only riveted on late in production.

Sea King and Commando side doors are too high above the deck for heavily-laden infantry to climb aboard without extra, external ladders.

 

[apparition13]

I just looked it up and the Swedes bought an ASW version.

Boeing-Vertol hkp4b

Operators, Versions and serials of the Boeing Vertol hkp4b helicopter

www.helis.com

So, not impossible.

Hangar space at sea might indeed be an issue. Doubt the Canadians go for the Blackhawk without an American buy, but that's a fun what-if, too.

I checked the dimensions. Assuming folding rotors, it should fit, at least in terms of height and length. Width - I don't know. I still have doubts about whether there is enough clearance to get the rear gear on the deck without hitting the hangar with the front rotor.

If Canada took on a full license - for potential development as well as construction - there would be the option of resumed production.

In OTL, the Sea King Replacement project stalled because there really wasn't anything to replace the CH-124 with ... other than newer Sea Kings. But what if Canada was in a position to simply restart production with Westland-style upgrades? That would've been the path of least resistance for the SKR project in 1977. So, let's say that contracts for SKR are signed in 1983 with deliveries of replacement airframes in 1985-1988. Likewise, for OTL's 1994 Maritime Helicopter Project, the earliest new-build S-61s would still be less than a decade old.

What would the effects be? OTL's 1985 New Shipboard Aircraft requirement would be being satisfied before it was ever formulated. So, no combined New Shipboard Aircraft Project/New SAR Helicopter Project would ever have happened either. Obviously the S-61/S-61R format eventually becomes dated but a range of upgrades and updates were possible. For example, as T58 supplies dried up, switch to the more powerful, British-made version - the 1,660 shp Rolls-Royce Gnome H.1400-2 (and maybe Westland's 6-bladed tail rotor?). Further on, more modern engines would have been feasible ... and maybe even with Canadian content.

Are you sure about the dated part? The Mi8/17/24 are still in production, and still capable aircraft. As are UH1/AH1. Barring an FVL revolution, they will likely continue to be for the near term. Which is 40-50 years beyond the mid-80s.

 

[riggerrob]

Length would definitely be a problem on Canadian destroyer flight decks. Sea Kings are 55 feet long and even with the tail rotor hanging over the aft end of the flight deck, those main rotor tips still got uncomfortably close to hangar doors.
OTOH, CH-46 is 83 feet long. That would require a new flight deck over hanging the Limbo mortar well. Have you ever wondered what happens when you fire a mortar UP into a steel deck?

 

[_Del_]

I still have doubts about whether there is enough clearance to get the rear gear on the deck without hitting the hangar with the front rotor.

Devil's always in the details.

OTOH, CH-46 is 83 feet long

OTOOH, CH-46 rotors are only 52 feet wide, where as the Sea King's is 62 foot. How big is our flight deck?
Maybe we land it sideways and three-point turn it into the hangar

 

[Apophenia]

... Are you sure about the dated part? The Mi8/17/24 are still in production, and still capable aircraft. As are UH1/AH1. Barring an FVL revolution, they will likely continue to be for the near term. Which is 40-50 years beyond the mid-80s.

Good point. Instead of 'dated', perhaps I should have said there was 'room for improvement'.

 

[Stovepipe]

Good points dear apophenia,

The first Vertol 107 (Voyager) flew in 1958.
The first S-61 Sea King flew in 1959.
The first S-61R flew in 1963.

I suspect that even when folded (USMC pattern), Vertol 107/CH-46 was too big for RCN Destroyer Escorts (DDE). A folded Vertol 107 is 45 feet long by 15 feet wide.
Sorry that I do not know the folded dimensions of Sea Kings, but know that the 64 rotor diameter exceeds the beam of DDH 280 class destroyers. Even when folded, a pair of Sea Kings require a hangar the full width of the ship. Those hangars are also quite tall and catch a lot of wind. The large side surface and high centre of gravity contribute to rolls as much as 45 degrees! I have experienced 40 degree rolls aboard HMCS Iroquois that quickly exhausted sailors.

I am not sure about the stability of S-61R on the water.

On the subject of stability on the water. It may not be clear from photographs, but Sea King aluminum sponsons contain huge wheel wells, which halve the amount of floatation. Ergo, most Sea Kings were fitted with emergency floatation bladders on the outboard side of the aluminum sponsons. These inflated to roughly the same size as the aluminum sponsons, doubling roll stability.
Civilian S-61Ls had double-sized aluminum sponsons.
Many British naval helicopters had emergency flotation bolted to the outboard ends of main wheel axles.
Also note that Canadian Labrador and Swedish CH-46 had huge fuel tanks bolted to their stub-wing sponsons.
I suspect that RCAF SAR S-61R would receive similar, double-sized sponsons/fuel tanks.

A Canadian Sea King navigator told me an amusing anecdote, in 1984. He and some other Canadian aircrew had recently visited the Sikorsky factory to review the new S-60 Sea Hawk. They admired its simplified maintenance and improved performance but grumbled about how its tiny cabin was unsuitable for the "admiral's barge" ... er .... cross-decking the padre on Sunday mornings .... er .... long range SAR role ... er ... cross-decking cargo role. Yes, that is it: cross-decking cargo. When a Canadian suggested building a SH-60FH (Fat Hawk), Sikorsky engineers politely chuckled!
A few years later, Sikorsky announced that they were developing the S-92 which is essentially an S-61R fuselage hung under SH-60 rotors. S-92 incorporates a cargo ramp under the aft fuselage and was adopted as the Sea King Replacement.

Yes, I mentioned a long-range SAR role for embarked Canadian Sea KIngs. On a few occasions, Canadian ships were the closest to civilian ships in distress and rescued passengers with their personnel hoists. All RCN Sea Kings had personnel hoists permanently fitted above cargo doors.

As for upgrades - like Westland's six-bladed tail rotors - .... After the supply of original - American-made - tail rotor blades dried up, Canadian Sea Kings got five Westland tail rotor blades bolted to the their stock tail rotor hubs. I watched them doing hover trials at CFB Shearwater. New Westland-built blades looked the same to maintainers.

OTL all RCN Sea Kings were assembled at United Technology's factory near Montreal. They just bolted together parts made by Sikorsky. They hoped to assemble more S-61s for civilians, but those contracts never came.
ATL I can forecast Sikorsky sub-contracting for simple, sheet metal components, but keeping drive train production in house. That would see Canadian Sea King sheet metal production farmed out to Canadair, Fleet, Bristol, etc. ... whichever federal riding needed to buy a few more votes. That would allow politicians photo opportunities beside, big, shiny, impressive pieces of aluminum airframes. Though it makes sense to only use 1.5 sets of jigs to build all the fuselages. Stock forward and mid fuselages would be build on one set of jigs with the two different aft fuselages built on separate jigs and only riveted on late in production.

Sea King and Commando side doors are too high above the deck for heavily-laden infantry to climb aboard without extra, external ladders.

Im surprised you were allowed to do that Westland rotor swap. Heli companies are notorious for not allowing licensed parts to be fitted to other aircraft. Bell and Agusta being a case in point. Aerospatiale wouldnt allow Allouette users to fit license built parts on French origin Alouettes, evn if they were absolutely identical.

 

[riggerrob]

Good points dear apophenia,

The first Vertol 107 (Voyager) flew in 1958.
The first S-61 Sea King flew in 1959.
The first S-61R flew in 1963.

I suspect that even when folded (USMC pattern), Vertol 107/CH-46 was too big for RCN Destroyer Escorts (DDE). A folded Vertol 107 is 45 feet long by 15 feet wide.
Sorry that I do not know the folded dimensions of Sea Kings, but know that the 64 rotor diameter exceeds the beam of DDH 280 class destroyers. Even when folded, a pair of Sea Kings require a hangar the full width of the ship. Those hangars are also quite tall and catch a lot of wind. The large side surface and high centre of gravity contribute to rolls as much as 45 degrees! I have experienced 40 degree rolls aboard HMCS Iroquois that quickly exhausted sailors.

I am not sure about the stability of S-61R on the water.

On the subject of stability on the water. It may not be clear from photographs, but Sea King aluminum sponsons contain huge wheel wells, which halve the amount of floatation. Ergo, most Sea Kings were fitted with emergency floatation bladders on the outboard side of the aluminum sponsons. These inflated to roughly the same size as the aluminum sponsons, doubling roll stability.
Civilian S-61Ls had double-sized aluminum sponsons.
Many British naval helicopters had emergency flotation bolted to the outboard ends of main wheel axles.
Also note that Canadian Labrador and Swedish CH-46 had huge fuel tanks bolted to their stub-wing sponsons.
I suspect that RCAF SAR S-61R would receive similar, double-sized sponsons/fuel tanks.

A Canadian Sea King navigator told me an amusing anecdote, in 1984. He and some other Canadian aircrew had recently visited the Sikorsky factory to review the new S-60 Sea Hawk. They admired its simplified maintenance and improved performance but grumbled about how its tiny cabin was unsuitable for the "admiral's barge" ... er .... cross-decking the padre on Sunday mornings .... er .... long range SAR role ... er ... cross-decking cargo role. Yes, that is it: cross-decking cargo. When a Canadian suggested building a SH-60FH (Fat Hawk), Sikorsky engineers politely chuckled!
A few years later, Sikorsky announced that they were developing the S-92 which is essentially an S-61R fuselage hung under SH-60 rotors. S-92 incorporates a cargo ramp under the aft fuselage and was adopted as the Sea King Replacement.

Yes, I mentioned a long-range SAR role for embarked Canadian Sea KIngs. On a few occasions, Canadian ships were the closest to civilian ships in distress and rescued passengers with their personnel hoists. All RCN Sea Kings had personnel hoists permanently fitted above cargo doors.

As for upgrades - like Westland's six-bladed tail rotors - .... After the supply of original - American-made - tail rotor blades dried up, Canadian Sea Kings got five Westland tail rotor blades bolted to the their stock tail rotor hubs. I watched them doing hover trials at CFB Shearwater. New Westland-built blades looked the same to maintainers.

OTL all RCN Sea Kings were assembled at United Technology's factory near Montreal. They just bolted together parts made by Sikorsky. They hoped to assemble more S-61s for civilians, but those contracts never came.
ATL I can forecast Sikorsky sub-contracting for simple, sheet metal components, but keeping drive train production in house. That would see Canadian Sea King sheet metal production farmed out to Canadair, Fleet, Bristol, etc. ... whichever federal riding needed to buy a few more votes. That would allow politicians photo opportunities beside, big, shiny, impressive pieces of aluminum airframes. Though it makes sense to only use 1.5 sets of jigs to build all the fuselages. Stock forward and mid fuselages would be build on one set of jigs with the two different aft fuselages built on separate jigs and only riveted on late in production.

Sea King and Commando side doors are too high above the deck for heavily-laden infantry to climb aboard without extra, external ladders.

Im surprised you were allowed to do that Westland rotor swap. Heli companies are notorious for not allowing licensed parts to be fitted to other aircraft. Bell and Agusta being a case in point. Aerospatiale wouldnt allow Allouette users to fit license built parts on French origin Alouettes, evn if they were absolutely identical.

Sikorsky quit building S-61s several years before the Canadian Armed Forces exhausted their supply of tail rotor blades. It would have been silly for Sikorsky to discourage the Canadian Armed Forces from using after-market parts when Sikorsky was no longer making S-61 blades. I also suspected that US Navy warehouses had been emptied of all airworthy tail rotor blades, so the next sources were Westland or Augusta/Bell.

 

[Stovepipe]

Good points dear apophenia,

The first Vertol 107 (Voyager) flew in 1958.
The first S-61 Sea King flew in 1959.
The first S-61R flew in 1963.

I suspect that even when folded (USMC pattern), Vertol 107/CH-46 was too big for RCN Destroyer Escorts (DDE). A folded Vertol 107 is 45 feet long by 15 feet wide.
Sorry that I do not know the folded dimensions of Sea Kings, but know that the 64 rotor diameter exceeds the beam of DDH 280 class destroyers. Even when folded, a pair of Sea Kings require a hangar the full width of the ship. Those hangars are also quite tall and catch a lot of wind. The large side surface and high centre of gravity contribute to rolls as much as 45 degrees! I have experienced 40 degree rolls aboard HMCS Iroquois that quickly exhausted sailors.

I am not sure about the stability of S-61R on the water.

On the subject of stability on the water. It may not be clear from photographs, but Sea King aluminum sponsons contain huge wheel wells, which halve the amount of floatation. Ergo, most Sea Kings were fitted with emergency floatation bladders on the outboard side of the aluminum sponsons. These inflated to roughly the same size as the aluminum sponsons, doubling roll stability.
Civilian S-61Ls had double-sized aluminum sponsons.
Many British naval helicopters had emergency flotation bolted to the outboard ends of main wheel axles.
Also note that Canadian Labrador and Swedish CH-46 had huge fuel tanks bolted to their stub-wing sponsons.
I suspect that RCAF SAR S-61R would receive similar, double-sized sponsons/fuel tanks.

A Canadian Sea King navigator told me an amusing anecdote, in 1984. He and some other Canadian aircrew had recently visited the Sikorsky factory to review the new S-60 Sea Hawk. They admired its simplified maintenance and improved performance but grumbled about how its tiny cabin was unsuitable for the "admiral's barge" ... er .... cross-decking the padre on Sunday mornings .... er .... long range SAR role ... er ... cross-decking cargo role. Yes, that is it: cross-decking cargo. When a Canadian suggested building a SH-60FH (Fat Hawk), Sikorsky engineers politely chuckled!
A few years later, Sikorsky announced that they were developing the S-92 which is essentially an S-61R fuselage hung under SH-60 rotors. S-92 incorporates a cargo ramp under the aft fuselage and was adopted as the Sea King Replacement.

Yes, I mentioned a long-range SAR role for embarked Canadian Sea KIngs. On a few occasions, Canadian ships were the closest to civilian ships in distress and rescued passengers with their personnel hoists. All RCN Sea Kings had personnel hoists permanently fitted above cargo doors.

As for upgrades - like Westland's six-bladed tail rotors - .... After the supply of original - American-made - tail rotor blades dried up, Canadian Sea Kings got five Westland tail rotor blades bolted to the their stock tail rotor hubs. I watched them doing hover trials at CFB Shearwater. New Westland-built blades looked the same to maintainers.

OTL all RCN Sea Kings were assembled at United Technology's factory near Montreal. They just bolted together parts made by Sikorsky. They hoped to assemble more S-61s for civilians, but those contracts never came.
ATL I can forecast Sikorsky sub-contracting for simple, sheet metal components, but keeping drive train production in house. That would see Canadian Sea King sheet metal production farmed out to Canadair, Fleet, Bristol, etc. ... whichever federal riding needed to buy a few more votes. That would allow politicians photo opportunities beside, big, shiny, impressive pieces of aluminum airframes. Though it makes sense to only use 1.5 sets of jigs to build all the fuselages. Stock forward and mid fuselages would be build on one set of jigs with the two different aft fuselages built on separate jigs and only riveted on late in production.

Sea King and Commando side doors are too high above the deck for heavily-laden infantry to climb aboard without extra, external ladders.

Im surprised you were allowed to do that Westland rotor swap. Heli companies are notorious for not allowing licensed parts to be fitted to other aircraft. Bell and Agusta being a case in point. Aerospatiale wouldnt allow Allouette users to fit license built parts on French origin Alouettes, evn if they were absolutely identical.

Sikorsky quit building S-61s several years before the Canadian Armed Forces exhausted their supply of tail rotor blades. It would have been silly for Sikorsky to discourage the Canadian Armed Forces from using after-market parts when Sikorsky was no longer making S-61 blades. I also suspected that US Navy warehouses had been emptied of all airworthy tail rotor blades, so the next sources were Westland or Augusta/Bell.

Folded aluminium. Rotor blades. Assembled by the lowest paid.

 

[1635yankee]

The prototype S-61R flew in June 1963 but the USAF had already placed orders (IOC for the CH-3C was sometime in 1964). Of course, speed of production in Canada would depend upon whether this represented simple assembly of Sikorsky-supplied components or a full license deal. If the latter, I envision the work being broken up by region.

If, as given in my backstory, the S-61 was assembled by DHC and the S-61R by Fleet, ... who supplies the parts? Doubtless, much of it would come from Connecticut. But, under the Defence Production Sharing Programme, at least some of the components could be licensed by Canadian firms - the usual pattern was the major portion going to Canadair in Montréal, QC. My bet would be additional work going to Fairey since they had plants in both Dartmouth, NS and Sidney, BC.

Stability on the water: You see photos of AMI Agusta-built AS-61Rs in the water. However, since the S-61R lacks the Sea King's outrigger floats, I'd guess that the 'R would be less stable on the water.

I'm not sure about comparative usable interior space. Having a rear ramp has certainly proved useful for the SAR CH-149s and would have to speed battlefield egress for troops.

I should mention that, for my little backstory, I jumped ahead to post-Unification designations. In reality, early designations would likely have been CHSS-2 (RCN), S-61R (CCG), CUH-3 (CA), and CSR-124 (RCAF SAR).

Going back to riggerbob's original questions ...

Would a common airframe simplify logistics, maintenance and training? Definitely. But the full benefits of commonality probably wouldn't be realized until after Unification. Of course, the GoC would have had the option of setting up some form of 'joint' helicopter procurement, support, and maintenance organization ahead of time to reap those benefits from the outset.

How would a common airframe affect Chinook purchases, Cormorant purchases or S-92 (Sea King replacement) purchases? I think that would depend upon the nature of the original procurement. If Canada took on a full license - for potential development as well as construction - there would be the option of resumed production.

In OTL, the Sea King Replacement project stalled because there really wasn't anything to replace the CH-124 with ... other than newer Sea Kings. But what if Canada was in a position to simply restart production with Westland-style upgrades? That would've been the path of least resistance for the SKR project in 1977. So, let's say that contracts for SKR are signed in 1983 with deliveries of replacement airframes in 1985-1988. Likewise, for OTL's 1994 Maritime Helicopter Project, the earliest new-build S-61s would still be less than a decade old.

What would the effects be? OTL's 1985 New Shipboard Aircraft requirement would be being satisfied before it was ever formulated. So, no combined New Shipboard Aircraft Project/New SAR Helicopter Project would ever have happened either. Obviously the S-61/S-61R format eventually becomes dated but a range of upgrades and updates were possible. For example, as T58 supplies dried up, switch to the more powerful, British-made version - the 1,660 shp Rolls-Royce Gnome H.1400-2 (and maybe Westland's 6-bladed tail rotor?). Further on, more modern engines would have been feasible ... and maybe even with Canadian content.

Note that Canada's current large helicopter fleet has no engine commonality with the fixed-wing fleet. For example, the new FWSAR aircraft could have been a GE-powered CASA CN235 for some commonality with the CT-7s of the co-based CH-149 fleet. Instead, DND went with PW127-powered C295s for FWSAR. Meanwhile, PWC has never managed to develop a turboshaft derivative from its PW12x family. Now imagine an MLU for the 1980s-vintage S-61/S-61R fleet with new 'PW127TS' engines, composite rotor blades, 'glass' cockpits, etc. ...

Back when I worked for Sikorsky (I left in 1984), many of the engineers (including those in management positions) felt that Sikorsky's decision to cease production of the S-61 was a mistake of a fairly high order.

 

[jcf]

One minor point, the S-61L airliner was not amphibious, it had a fixed landing gear without floats
and the bottom of the forward fuselage on the port side was flat, it was the luggage compartment.
The S-61N was amphibious with large floats and boat hull.
Many of the S-61s, civil and ex-military, converted for logging and crane use are fitted with L-type
landing gear as there is no need for amphibious capability and it weighs less.

 

[1635yankee]

One minor point, the S-61L airliner was not amphibious, it had a fixed landing gear without floats
and the bottom of the forward fuselage on the port side was flat, it was the luggage compartment.
The S-61N was amphibious with large floats and boat hull.
Many of the S-61s, civil and ex-military, converted for logging and crane use are fitted with L-type
landing gear as there is no need for amphibious capability and it weighs less.

When I was working in aerospace (I left close to 30 years ago), I remember hearing that one of the operators (I can't recall which one, but I think it was Okanagon or Evergreen) had an S-61 that was so stripped that it had to be trucked between sites.

 

[riggerrob]

One minor point, the S-61L airliner was not amphibious, it had a fixed landing gear without floats
and the bottom of the forward fuselage on the port side was flat, it was the luggage compartment.
The S-61N was amphibious with large floats and boat hull.
Many of the S-61s, civil and ex-military, converted for logging and crane use are fitted with L-type
landing gear as there is no need for amphibious capability and it weighs less.

When I was working in aerospace (I left close to 30 years ago), I remember hearing that one of the operators (I can't recall which one, but I think it was Okanagon or Evergreen) had an S-61 that was so stripped that it had to be trucked between sites.

I suspect that they were just trying to save the little time remaining on expensive life-limited components like rotors and engines.

 

[NOMISYRRUC]

For what they're worth these are the dimensions of the HSS-2 Sea King according to the Standard Aircraft Characteristics of 30th July 1960 and the CH-46D Sea Knight from its Standard Aircraft Characteristics of August 1985.

​

Source: http://www.alternatewars.com/SAC/SAC.htm

Note: Some dimensions have been rounded up to the nearest inch.

*HSS-2 actually 56ft 9½in and CH-46D was actually 45ft 7½in.​

†HSS-2 actually 16ft 8½in​

§ HSS-2 didn't have a Height with Blades Rotating so I assumed it was the same as the Height with Blades Folded. CH-46D was actually 16ft 11½in.​

The salient details are:

​

The folded length and span of a Sea Knight are both about a foot less than a Sea King. Its height with the blades folded is half an inch less. So it will fit into the hangars of the Canadian warships and auxiliaries that operated the Sea King.

The Sea Knight with its blades rotating is 8 feet 7 inches longer than a Sea King. That shouldn't be a problem for operating from Bonaventure and the tankers, but it might be too long for the flight decks of the destroyers and frigates that operated the Sea King.

Also the RCN/Maritime Command "has previous" when it comes to twin-rotor helicopters. That is it operated Piasecki HUP-3 Retrievers from 1954 to 1964 and intended to buy some Bristol Belvederes.