RAF Piasecki H-21

[chrisonord]

In my stash for sale pile is a 2000 release Italeri  H-21C gunship, which  after looking at it  gave me an idea  for replacing the  terrible  Airfix Bristol Belvedere  that nearly went in the bin.
What if the RAF  needed a heavy  lift helicopter  in the mid 50's  and the Belvedere hadn't been  conceived  as yet. I am thinking of  1950's  RAF transport command  markings  and the white  over  bear metal  finish  with the thin blue  line, much like the  Belvedere sported. I am thinking minimal  modification  to the kit? Colour scheme and  decals  as without  opening the kit  up i am not  sure if I  could  upgrade the engines on it as the real ones are  piston ones?. Unless I say they are either a  British built radial engine or  a license built one.  I am  thinking  having it in service  until the  Belvedere  came into service.  Both  helicopters are a little known  quantity to me as I  don't have books on them  and I  can never remember what I read on line. Another idea  for  it would utilize the  hard points on the fuselage, by putting  large ferry tanks on it and putting it in the royal navy during the  1950's.
Cheers
Chris

[PR19_Kit]

The H-21 only has one engine, a socking great Wright radial that sits where the 'bend' of the fuselage is.

Swapping it for a turbine would make a lot of sense................

[ChernayaAkula]

Brit H-21 is a great idea! 

<...> Swapping it for a turbine would make a lot of sense................

H-34 --> Wessex
H-21 -->

[PR19_Kit]

Winchester?
Worcester?
Wantage?
Warton?

[chrisonord]

Putting an air intake and a  jet exhaust  shouldn't be too much of a problem, as  I said  it is still shrink wrapped, so not  looked at the thing  yet. Something  1950's  era will be the head scracher though, as everything would  still  be pretty  big in those days wouldn't it.
Chris

[PR19_Kit]

It'd need 1400 bhp or so to equal the Wright, which oddly is about what the Gazelle used in the Belvedere had, and it had TWO of them!

The Gazelle's not all that big, 70" long x 33" dia, and it first ran in 1955 so it may well suit your time scale as well.

[chrisonord]

It'd need 1400 bhp or so to equal the Wright, which oddly is about what the Gazelle used in the Belvedere had, and it had TWO of them!

The Gazelle's not all that big, 70" long x 33" dia, and it first ran in 1955 so it may well suit your time scale as well.

Marvellous, I  will have a look  at those, there is two big holes in the rear lower fuselage where  the exhausts  can exit too. I have opened the kit now,and  had a look at the  size of the thing.  Only difficulty I  think I will have  is painting the  thin blue line between the  white and silver, plus I don't think I have that blue  either.  I will  look and see if I have some  long  blue  decals, and I could attempt those if they are suitable.
Chris

[chrisonord]

Would it be better  with two or just  the one Napier Gazelle engine  as they are powerful enough  singularly  aren't they.
Chris

[PR19_Kit]

If the payload would be the same as the USS Army version it should be fine, yes. But the RAF were tending toward twin engines at the time, viz the various Wessex Marks.

The Belvedere was a bit heavier than the H-21 but only carried the same number of troops, so with twice the engines it had much more specific excess power. Never a bad thing with a helicopter. 

[chrisonord]

If the payload would be the same as the USS Army version it should be fine, yes. But the RAF were tending toward twin engines at the time, viz the various Wessex Marks.

The Belvedere was a bit heavier than the H-21 but only carried the same number of troops, so with twice the engines it had much more specific excess power. Never a bad thing with a helicopter. 

I think  after having a good  look at the  engine  bay part of the kit a couple of  Gazelle engines could  squeeze  into the  gap left by the Wright  radial engine, it could  have one of the later 1800 hp versions  of the Gazelle  and only need one, but two is always  better than one 
Chris

[jcf]

Two H-21 converted as turbine test-beds: 57-2610 two T53; 57-2611 two T58 (aka DH Gnome).

Also an unbuilt French project using three Turbomecha Turmo III.

[chrisonord]

Thanks for the info Jon, two turbine engines are  pretty plausible  then really.  I  thought  that they would still be quite big and there not  be enough room  for more than one.  I  will look for those .

[jcf]

The French project, note how the engines were to be installed.

[PR19_Kit]

Phew, with three Turmo IIIs that would have had some serious grunt!

[Weaver]

This is a great idea.

Don't worry about large power steps: this often happened when piston-engined helos were converted to gas-turbines. Another thing that's often done is to replace one engine with two which are each nearly as powerful, but then de-rate them for normal use. That way, if one engine fails, the other can go to full emergency power and still have enough power to keep the machine flying, helicopters being notoriously poor gliders...

For instance, the Sikorsky S-58 had a 1525 shp radial. The Wessex developed from it initially had one 1650 shp Gazelle turboshaft, but then went to a pair of Gnomes. Each Gnome was rated at 1350 shp, but in normal use, the pair were limited to a combined output of 1550 shp (presumably limited by the original S-58 gearbox). However if one of them failed, the other one could go to full throttle and still give 87% of the aircraft's normal max power.

Modelling-wise, bear in mind that each Gazelle had two small jetpipes instead of the one you'd expect (you can see these paired pipes on the Belvedere model)

I am thinking of  1950's  RAF transport command  markings  and the white  over  bear metal  finish

A mental image which provokes the question, "do bears shine in the woods?"