Re: Slow Helos in Iraq

Paul wrote:

> "Guy Alcala" <g_alcala@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message

<snip>

> > Haul it, sure, but it can't take off or land with that load at that
> > height,
> > unless it's operating HIGE. Fine for putting troops in a valley, but
> > generally
> > not an option for pinnacle landings on a peak or narrow ridge. A
> > 3,000-3,500
> > lb. useful load seems more in the ballpark. If you want more at that
> > height,
> > its CH-47s or CH-53Es. And it will be interesting to see how the UH-1Y
> > does.
> >
>
> WIth the 4 bladed head, and a ton of power from the twin T700's, the UH-1Y
> should have very good high / hot capability (So should the AH-1Z).

OTOH they've both gotten a lot heavier, so it may well just balance out. They
still benefit from improved speed, range, survivability etc.

> As was the UH-1N, they are both drivetrain limited, aren't they?

> The engines make much more power than can be delivered to the transmission,
> which gives reliable power in reduced performance areas of operation.
> Of course single engine flight is another matter.
>
> The original UH-1N made 1800 SHP with the 2 - T400's, the transmission was
> limited to 1280 shp. So in high / hot conditions, the engines still
> produced 100%
> power needed.

Bell's UH-1Y link says that the MRGB can handle 2,625 shp., which would be
distributed between main and tail rotor as well as accesories. Twin engine
Intermediate (30 minute) rating is 1,695 shp (SL ISA) per engine, so there's a
fair amount of excess to deal with altitude and heat. OTOH, the spec mission
temps and altitudes seem to be the same as for the MV-22, i.e. 40 deg. C/SL T/O
and 3,000ft./33 deg. C five minute HOGE mid-mission, inserting 8 Marines by fast
rope (crew of four, 120 chaff/flare cartridges, internal fuel only). I've been
unable to find a HOGE ceiling chart, although the max. HOGE weight (ISA, not
sure if it's SL or else 3,000 ft. PA) is credited as 17,236 lb. (vs. the 18,500
MGW).

<snip>

> Many Army and Guard aviation units still go out and train at HAATS. More so
> now
> than before we went into Afghanistan. (High Altitude Aviation Training
> Site).
> CH-47's in Afghanistan routinely make flights over 14.000 ft mountains, and
> landings
> at 10,000 to 12,000 sites.

Which reminds me, are the CH-47s in Afghanistan carrying supplemental O2 for the
pax? I assume the MH-47s would have this capability built in, but figure that
the vanilla model would have to use a kit of some kind.

Guy


.

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