Re: Slow Helos in Iraq


"Guy Alcala" <g_alcala@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:43192C3B.9031BAB4@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> 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
>
>

Yes it is a kit.

For flight up to 10,000 feet - no oxygen needed.
12,000 feet for up to 30 minutes, no oxygen needed.
Above 12,000 feet. crew and pax must have oxygen.





.

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