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Air Hockey Propellers

Folding helicopter blades

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It's a general topic but hopefully we can create a sort of database on which helicopters have and don't have folding blade mechanisms.

 

As for myself, I am building an Airfix HH-53C Jolly Green Giant. I've read that the Navy version of the H-53 had folding blades (implying that the USAF versions did not?), I've read here from someone who said he had never seen USAF verions with folded blades, but I'm still doubtful as the aftermarket part that allows for folded blades indicates that it's meant for the HH-53C (USAF) version, too.

 

Same question for the USAF HH-3 I'll build next except I have even less information.

 

Anything you know with or without absolute certainty is welcome, thanks! 

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See the link below to the Sikorsky web page, which has excellent photos, description, and history of all of their rotary wing aircraft. Hope this will help a little. Not that it means anything, but I don't recall ever seeing a USAF example with the rotor blades folded, with the exception of when one was being airlifted. I have seen written reference to the Navy and Marine examples having power folding for the rotor blades, but not the AF ones. Very useful aboard ship, to be sure.

Mike

 

https://www.sikorskyarchives.com/index.php

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Check out DF Helo stuff. They make rotor fold parts in 1/72. They are good, I have used them on 2 Seakings and a CH-53.

 

regards Toby

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On 1/29/2020 at 3:49 PM, 72modeler said:

See the link below to the Sikorsky web page, which has excellent photos, description, and history of all of their rotary wing aircraft. Hope this will help a little. Not that it means anything, but I don't recall ever seeing a USAF example with the rotor blades folded, with the exception of when one was being airlifted. I have seen written reference to the Navy and Marine examples having power folding for the rotor blades, but not the AF ones. Very useful aboard ship, to be sure.

Mike

 

https://www.sikorskyarchives.com/index.php

I can't offer definite information on the H-53 family, but the two flavours of British Merlin (until the RN took the HC3s and 3As) illustrate a type where one variant has blade fold and another doesn't. Bear in mind that the blade fold has several significant drawbacks which can hinder a land-based unit. The RAF had a lot of trouble over the years with the blade fold on Sea Kings, and not much benefit, but it was always going to be just that little bit too difficult to remove. 

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With regard to the H-53, see my response to the question over in the other thread:

 

 

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3 hours ago, Robertone139 said:

The new Merlins for the RAF  have folding main rotor and tail pylons.

The RAF does not have any Merlins, they all went to the Royal Navy’s Fleet Air Arm. 

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I a sure that I have read that the HH-3Es in Vietnam did not have folding rotors.  I will see if  I can track down where I read it.

 

George

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3 hours ago, Dervish said:

The RAF does not have any Merlins, they all went to the Royal Navy’s Fleet Air Arm. 

Good thing.

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26 minutes ago, Robertone139 said:

Good thing.

Good thing for the Navy! Except of course the small numbers.......

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The USAF's helicopters did not have folding blades.  No need for the extra complexity (as if helicopters aren't complex enough already!) and weight.

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On 2/1/2020 at 10:26 PM, boffin said:

I a sure that I have read that the HH-3Es in Vietnam did not have folding rotors.  I will see if  I can track down where I read it.

 

George

Good to know it's documented somewhere.

18 hours ago, NorthBayKid said:

The USAF's helicopters did not have folding blades.  No need for the extra complexity (as if helicopters aren't complex enough already!) and weight.

That makes sense indeed. 

 

...So those aftermarket parts for folded blades on USAF helis are surely compatible but inaccurate. 

 

And I guess it's pretty much safe to assume that all helicopters with more than two blades (including Pedro) intended to land on war ships or belong to the Navy, or Marines have folding blades. 

 

And although for the army, the Chinook seems to have foldable blades from model A.

 

 

 

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The Chinook’s blades are foldable because Army aircraft are designed to be air transportable.  The USAF’s aircraft tend to be permanently based abroad, so if they are air transported, they simply remove the blades and reinstall them when they get to where they’re going.  

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47 minutes ago, Air Hockey Propellers said:

And I guess it's pretty much safe to assume that all helicopters with more than two blades (including Pedro) intended to land on war ships or belong to the Navy, or Marines have folding blades. 

 

And although for the army, the Chinook seems to have foldable blades from model A.

 

 

 

...although it's not uncommon to see helicopters without folding blades operating from ships - Chinook and Apache in British use alone. Some Chinook variants may have had provision for folding blades, but the vast majority don't, and I don't recall ever seeing a picture of a Chinook at sea with the blades folded. 

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1 hour ago, torqueofthedevil said:

...although it's not uncommon to see helicopters without folding blades operating from ships - Chinook and Apache in British use alone. Some Chinook variants may have had provision for folding blades, but the vast majority don't, and I don't recall ever seeing a picture of a Chinook at sea with the blades folded. 

 

Chinook blades can be folded, but it is manually and a pain the whatsitsname to do (plus takes a long time), so is not done.

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Pictures of manual blade folding on Chinook here.

http://www.chinook-helicopter.com/Folded_Blades/Folded_Blades.html

 

But why bother? It needs to be stripped down with rotor heads removed to be air transportable even in a C-5 or C-17.

 

Given the intention to use them regularly off the QE class carriers powered blade folding for at some of the RAF fleet would seem a good idea. All the deck/hangar photos I’ve seen the blades are left unfolded. Interesting fact - if the blades folded a Chinook’s deck footprint would match that of a folded Merlin.

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The answer to your question really depends on what you mean by folding blades - do you mean the type that are folded manually by a crew physically disconnecting the blades and moving them into to folded position or do you mean helicopters with an automatic blade fold system, e.g. Sea King? 

As others have said, helicopters operated by navies and marine corps are more likely to have an automatic blade fold while army and Air Force cabs tend to have fixed or manually folding blades - an exception would be the RAF rescue Sea King HAR3/3A, but even these rarely used the blade fold system (at least in my experience). Also, I never witnessed or heard of an example of the blades of RAF Pumas being folded - the blades were simply removed if needed.

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Rickoshea52 raises several valid points.  Power folding tends to be heavy and expensive - so is only fitted where there is likely to be a very good operational need.  Whether it is then used tends to depend on the actual use.  The main reason RAF Sea Kings had issues with powered blade fold was that it was not used all the time, unlike the RN aircraft.  The result was leaking hydraulics and malfunctioning microswitches.  Non-powered blade fold may be designed in, but can also depends on whether the head geometry allows blades to rotate about one pin (with pitch change rods disconnected as required) .  An examples is the Gazelle - I think that if you take one pin out, the blade can rotate about the remaining pin.  Park one blade over the tail, and the others can be manually folded in to give a much smaller footprint.  The more blades, and the larger, the harder either approach becomes.  I think I remember counting 28 sequence valves needed to make sure that a V-22's blades fold and unfold correctly...

 

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1 hour ago, Rickoshea52 said:

As others have said, helicopters operated by navies and marine corps are more likely to have an automatic blade fold while army and Air Force cabs tend to have fixed or manually folding blades - an exception would be the RAF rescue Sea King HAR3/3A, but even these rarely used the blade fold system (at least in my experience).

Another was the MH-53J; when the USAF added folding blades for shipboard compatability as part of the Pave Low III SLEP upgrades, the process was simplified by the fact that the Navy and Marine versions already had the system - the Air Force machines just had to be retro-fitted with the wiring, plumbing etc.. that was originally 'left out'...

 

One of the few RAF Sea Kings to be pictured with blades folded - XZ589 at RAF Finningley, 1981 (note the yellow hoist):

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And again, at RNAS Culdrose three years later:

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I've also got a couple showing Grey Whales with folded blades, XZ591 while 'down south', and XZ592 in the UK, complete with yellow blade down the starboard side...

....as also seen here on XZ598 at a soggy RAF St Mawgan:

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Here's Grey Whale ZA105 at the last RIAT to be held at Greenham Common, in 1983:

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Edited by andyf117

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20 minutes ago, andyf117 said:

Another was the MH-53J; when the USAF added folding blades for shipboard compatability as part of the Pave Low III SLEP upgrades, the process was simplified by the fact that the Navy and Marine versions already had the system - the Air Force machines just had to be retro-fitted with the wiring, plumbing etc.. that was originally 'left out'...

 

One of the few RAF Sea Kings to be pictured with blades folded - XZ589 at RAF Finningley, 1981 (note the yellow hoist):

 

And again, at RNAS Culdrose three years later:

 

I've also got a couple showing Grey Whales with folded blades, XZ591 while 'down south', and XZ592 in the UK, complete with yellow blade down the starbaord side...

The only time I ever saw folded blades on a HAR3 was during functional checks after a rotorhead/MRGB change or on the rare occasions that the OOPS code for the routine operation of the system was performed; I forget the frequency for this. A cause of much mirth among the heavy trades was when the DF’s misaligned the set up of the slip rings only to discover their error when the blades positioned over the front when operated. 

As you can imagine having the blades folded on a SAR cab at 15 minute readiness is just not sensible.

 

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4 minutes ago, Rickoshea52 said:

As you can imagine having the blades folded on a SAR cab at 15 minute readiness is just not sensible.

Indeed - you'll have noted that the above pics are all at air shows...

....the one taken in the Falklands obviously wasn't though - all folded up and tied down, but plugged in...

Captioned at Jetphotos as taken at Navy Point:

https://www.jetphotos.com/photo/8769822

Whereas the same pic at Airliners.net says Port Stanley:

https://www.airliners.net/photo/UK-Air-Force/Westland-WS-61-Sea-King-HAR3/559085/L?qsp=eJwtjEEKwkAMRe%2BStZsiCnZXL6ALLxCSjy1WZ8gE7Fh6d%2BPg7vEevJUkvRyL32oG9VTAJiPtKLPxs1C/0gP1nUyDafkcTl3EkszPNYSyYxBBdujfX0xhv4Qi7XOPbxcAuzam/TG8TiXP3B5wnmbati8C2C4s

 

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RN SAR cabs also kept their blades spread when on alert, for the same obvious reasons.  The HAR3 had blade fold because the Sea King is a Naval design and thus had it built in from the very start; as someone above has already observed, to take it out of the design would have been hugely costly and not really conveyed any great advantage.  
 

RN Sea Kings used the blade fold pretty much every sortie (HU5s on dedicated SAR stand-by being the exception, as above), and on the whole it was a reliable and robust system - very occasionally you’d get a sticky microswitch which required someone to climb up onto the head and give it a wee tap, but like many aircraft systems if you used it regularly it tended to work.  The Air Force wouldn’t need to fold so often, which would explain why they had more trouble with it.

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17 hours ago, Ex-FAAWAFU said:

 

RN Sea Kings used the blade fold pretty much every sortie

Yes, I remember the HC4’s of the RN det at Aldergrove doing this before being hangared. 

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On 2/2/2020 at 11:44 PM, NorthBayKid said:

The Chinook’s blades are foldable because Army aircraft are designed to be air transportable.  The USAF’s aircraft tend to be permanently based abroad, so if they are air transported, they simply remove the blades and reinstall them when they get to where they’re going.  

Thank you very much. Very interesting insight and it does make sense. 

 

On 2/2/2020 at 11:58 PM, torqueofthedevil said:

...although it's not uncommon to see helicopters without folding blades operating from ships - Chinook and Apache in British use alone. Some Chinook variants may have had provision for folding blades, but the vast majority don't, and I don't recall ever seeing a picture of a Chinook at sea with the blades folded. 

Wow, an Apache on shipboard use? Those blades don't fold in any way. But those Apaches are obviously not Navy so I guess they're not stored on board. I did see the article of the Chinook being stowed in HMS Queen Elizabeth but that was a one time thing I guess. And there seem to be rumors that the US wants the Marines to adopt the Chinook instead of the 53s at the detriment of the Marine's lift capacity... Also, I now understand that the Chinook blades fold but manually.

 

On 2/3/2020 at 4:15 AM, Rickoshea52 said:

The answer to your question really depends on what you mean by folding blades - do you mean the type that are folded manually by a crew physically disconnecting the blades and moving them into to folded position or do you mean helicopters with an automatic blade fold system, e.g. Sea King? 

As others have said, helicopters operated by navies and marine corps are more likely to have an automatic blade fold while army and Air Force cabs tend to have fixed or manually folding blades - an exception would be the RAF rescue Sea King HAR3/3A, but even these rarely used the blade fold system (at least in my experience). Also, I never witnessed or heard of an example of the blades of RAF Pumas being folded - the blades were simply removed if needed.

Given that it's a new subject for me, I wasn't sure that a manual folding option existed. I do know that there are automatic folding mechanisms back when I was studying the Sea Knight. I was actually quite amazed that they can confidently do that in such thin rotor blade supports.

 

On 2/3/2020 at 5:36 AM, TimB said:

The main reason RAF Sea Kings had issues with powered blade fold was that it was not used all the time, unlike the RN aircraft.  The result was leaking hydraulics and malfunctioning microswitches.  

 

Indeed, if you don't use them they can break down. Yet another reason why you wouldn't want automatic folding blades for land based operations.

 

 

All in all I can see that although the aftermarket kits for folded blades (automatic or manual) say they can be used on helicopters with land based markings, that was probably not the case in rel life. Personally, I have serious space constraints so I'll do the sacrilege of building my USAF HH-3 and CH-53 without the rotor blades, as if they were being prepared for transport... I just don't have the space or the delicacy for the full setup. Anyhow, it's certainly more realistic than folding the blades, for sure.

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