Why wasn't CH-37 Mojave upgraded to turbine engines?

[Dan]

Why wasn't CH-37 Mojave upgraded to turbine engines? It was an
interesting, if odd design, that might have had a longer life had they
upgraded to turbine engines. I know the U.S. Army went to CH-54 Tarhe,
AKA "skycrane", to do the heavy lift CH-37 was doing, but there has got
to be more to it than that.

CH-37 could carry men. CH-54 required the box to do it.

Dan, U.S. Air Force, retired

[Daryl]

From what I can see, here might be the reasons.

The Ch-37 wasn't really that large. By piston standards, it was
a real workhorse but lacked the altitude, speed and lifting
power. Yes, I know, new engines would cure 2 out of the 3
shortcomings but it was still too small.

The CH-54 could pod under it. The version that could do troops
and heavy lifting at the same time were not purchased.

Both were pretty well replaced by the CH-47 which could do it all
without pods. While a few of the CH-37s lasted until mid Vietnam
for Down Aircraft retrieval, the CH-47 was being introduced.

Two of the heavy workhorses were just replaced by a better system.

>
> Dan, U.S. Air Force, retired

--
http://tvmoviesforfree.com
for free movies and Nostalgic TV. Tons of Military shows and
programs.

[frank]

I always wondered that as well. However, I don't entirely agree
with why they were not converted. After all, the H-19 & H-34 were
converted to turbines in various forms altho not for the USA.

> --http://tvmoviesforfree.com

[Eunometic]

On Jan 8, 1:35 am, frank <famvb...@gmail.com> wrote:
> I always wondered that as well. However, I don't entirely agree
> with why they were not converted. After all, the H-19 & H-34 were
> converted to turbines in various forms altho not for the USA.
>

Turbine conversions of existing piston engined airframes seem to have
been motivated by
commercial cost pressures, for instance the S-58T, in which the
turbine version would
have represented a significant lowering of maintanance costs,
increased lift and greater
smoothness. However most commercial opperators would have little
interest in outsize
aircraft such as the CH-37; the market isn't big enough. If a
commercial opperator
were to use a CH-37 it would be mainly as a skycrane or to deliver
outsize loads. This would
be irregular work for which a conversions could not be justified. A
smaller helicopter such as
the S-58T would ply a trade in provisioning oil rigs and minning
opperations.

The Westland Wessex would be one of the few military conversions and I
think motivated by Britains odd situation.


In addition the Mojave was sized for 2 x 2100 PW R-2800 whereas the
Skycrane ended up with 2.5 times that in turbine power.

Finally the Sikorsky S-60, which was the skycrane protoptype, was PW
R-2800 powered. However it appears to have been a better canditate
for conversion to turbine power than the CH-37

[frank]

The S-60 wasn't 'the skycrane prototype', it was a development
of the Mojave using its engines & rotor, etc., so, had the S-60 been
truly a better candidate for conversion power, then it only makes
sense that so would the Mojave. Agreed, the demand vs. cost of those
conversions is certainly a factor.

[Keith W]

Eunometic wrote:
> On Jan 8, 1:35 am, frank <famvb...@gmail.com> wrote:
>> I always wondered that as well. However, I don't entirely agree
>> with why they were not converted. After all, the H-19 & H-34 were
>> converted to turbines in various forms altho not for the USA.
>>
>
> Turbine conversions of existing piston engined airframes seem to have
> been motivated by
> commercial cost pressures, for instance the S-58T, in which the
> turbine version would
> have represented a significant lowering of maintanance costs,
> increased lift and greater
> smoothness. However most commercial opperators would have little
> interest in outsize
> aircraft such as the CH-37; the market isn't big enough. If a
> commercial opperator
> were to use a CH-37 it would be mainly as a skycrane or to deliver
> outsize loads. This would
> be irregular work for which a conversions could not be justified. A
> smaller helicopter such as
> the S-58T would ply a trade in provisioning oil rigs and minning
> opperations.
>
> The Westland Wessex would be one of the few military conversions and I
> think motivated by Britains odd situation.
>

The Wessex while based on the CH-34 was intended to have a
turbine engine from the start and was not the only turbine variant.
The Sikorsky S-58T was a turbine version of the same CH-34
that the Wessex was based on

>
> In addition the Mojave was sized for 2 x 2100 PW R-2800 whereas the
> Skycrane ended up with 2.5 times that in turbine power.
>
> Finally the Sikorsky S-60, which was the skycrane protoptype, was PW
> R-2800 powered. However it appears to have been a better canditate
> for conversion to turbine power than the CH-37

The S-60 was basically just a cut down CH-37 which used the
the transmission, rotor system and piston engines from the CH-37

The real problem was that helicopters were evolving fast and what the
US military needed was lots of them. Only 154 CH-37's were built
and they were in heavy use so it made more sense to concentrate on
producing newer types such as the CH-54 for the skycrane role and
the CH-47 for the general purpose missions.

Keith

[Paul Saccani]

On Sat, 07 Jan 2012 01:09:18 -0600, Dan <B24...@aol.com> wrote:

> Why wasn't CH-37 Mojave upgraded to turbine engines?

The design was, to some extent, in the licensed S60 production of the
Westland Westminster, the S60 being the flying crane prototype of the
S56/CH37.

Cheers,

Paul Saccani,
Perth,
Western Australia

[Paul Saccani]

On Sat, 7 Jan 2012 20:25:13 -0000, "Keith W"
<keithnosp...@demon.co.uk> wrote:

>> Finally the Sikorsky S-60, which was the skycrane protoptype, was PW
>> R-2800 powered. However it appears to have been a better canditate
>> for conversion to turbine power than the CH-37
>
>The S-60 was basically just a cut down CH-37 which used the

>the transmission, rotor system and piston engines from the CH-37.

Don't forget, Westland licensed the S60 and produced two turbine
powered Westminsters on that basis.

[Eunometic]

On Jan 8, 7:23 am, frank <famvb...@gmail.com> wrote:
>       The S-60 wasn't 'the skycrane prototype', it was a development
> of the Mojave using its engines & rotor, etc., so, had the S-60 been
> truly a better candidate for conversion power, then it only makes
> sense that so would the Mojave. Agreed, the demand vs. cost of those
> conversions is certainly a factor.
>

Its fairly obvious, in terms of layout, that Sikorsky evolutionary
development was
CH-37 Mojave -> S-60-> Sikorsky CH-54 Tarhe(civil designation S-64
Skycrane).

And certainly I would regard the S-60 as a test bed for skycrane if
not an actual prototype' apart from the bulky piston engines the
layout is the same.

The CH37's performance was greatly inadaquet for expected USAAF needs
and so required much greater power, which means a new transmission
optimised for the new gas turbines was needed, so I would argue that
the CH37/S-60 had met its development limmit and a new design based
around the old concept was the way forward.

[Keith W]

Yes but the type never really gelled. The idea was to build two variants
one a flying crane and the other a 40 seater transport. What was built
was quite different from the S-60 in having a space frame structure
which was later covered in fabric. By the time the fitted two turboshaft
engines and a Sikorsky S-64 rotorhead there really wasn't much of the
original design left. When Westland acquired the rights to the Fairey
Rotodyne and the Bristol Belvedere the project was closed down.

Keith
Keith

[Paul Saccani]

The project was closed before Fairy merged with Westland. This was at
the direction of the MAP. You are misplacing cause and effect.

[Peter Stickney]

On Sat, 07 Jan 2012 01:09:18 -0600, Dan wrote:

> Why wasn't CH-37 Mojave upgraded to turbine engines? It was an
> interesting, if odd design, that might have had a longer life had they
> upgraded to turbine engines. I know the U.S. Army went to CH-54 Tarhe,
> AKA "skycrane", to do the heavy lift CH-37 was doing, but there has got
> to be more to it than that.

The Army went to the CH-54, but they weren't the major CH-37 users.
The Big user was the USMC.
Nobody was really that thrilled with the CH-37. It was complicated,
cranky, a maintenance hog, and late. (The USMC was originally going
to equip practically all their helicopter transport squadrons with
HR2S/H-37s, but they took a long time to get into service.)
So - just at the time that they were rethinking the heavy lift helicopter
concept, the tuboshafts came out, and changed everything.
Since the turboshafts were smaller and lighter, and had lower cooling
air requirements, you could mount them above the fuselage, without the
pods, (Which cut down on hovering performance) and with direct inputs
into the transmission, without the extension shafts and right-angle gearing.
(Which costs power - rule of thumb is 2% per gear mesh)
The nose door was kinda neat, but a tail door and ramp is a lot better, so the
rotor boom gets thinned down and the integral door/ramp goes in.
Since the cockpit no longer had to be elevated to allow the nose door and ramp
to work, it can be put in the nose of the aircraft. Since we've now
got a big box-like fuselage, it's onlya short jump to make it a boat hull,
with sponsons for stability and carrying fuel.
At this point the CH-37 has morphed into the CH-53.

The Army went with a somewhat different tack. Most cargo/people
moving in the CH-37's load range was done by the CH-47.
The CH-54 was used for really outsized lifts, until the '90s,
when the late model CH-47s started to equal it in sling lift.

>
> CH-37 could carry men. CH-54 required the box to do it.

And the CH-53 and CH-47 did the job really well.
(Except when the CH-47 would mysteriously quit flying)

--
Pete Stickney
Failure is not an option
It comes bundled with the system