Of Helicopters and Hellfires

[Kirkhill]

http://www.defense-aerospace.com/cgi-bin/client/modele.pl?session=dae.4308111.1089903978.QPadasOa9dUAAESlMZk&modele=jdc_34

This article about US helicopter intentions also describes modifications to the Hellfire programme which could have implications for the MMEV program up here.

Emphasis is on improving what already exists, as in the case of existing helos and the Hellfire, improvinge serviceability and survivability. There is also an expressed intention to buy more Kiowas or similar ASAP.

The only really new programme is the 25 ton Heavy Lift helo.

 

[Wizard of OZ]

Seems nice but most of those mods will not effect the CF besides aren't you happy with the Griffion.

 

[Infanteer]

besides aren't you happy with the Griffion.

You're kidding, right?

 

[Wizard of OZ]

Would not most armies in the world be happy with a civilian helicopter with a green coat of paint.  This is the wave of the future man.

Yes of course i am kidding.

 

[Bograt]

Hey, as a possible future griffon driver I believe I can speak as an expert on the issue. I like the colour green. 

 

[Gunnerlove]

I was under the impression that the Griffin is a Bell 412 which is a twin Huey with a quad rotor. So a military helicopter based on a military helicopter.

They are what they are light utility helicopters, don't hate them for being what they are.

 

[Kirkhill]

Maybe Inch could jump in but I think the difference is in the power pack.  If I understand correctly the Griffon uses a Pratt and Whitney Canada TwinPac which generates about half the shaft-horsepower of the General Electric? pack that the USMC is installing as an upgrade on its UH-1N Hueys.

 

[Zoomie]

I was under the impression that the Griffin is a Bell 412 which is a twin Huey with a quad rotor.

The Bell 412 is nothing like the good old Twin Huey.  The huey had lots of power and her former pilots still sing accolades to this day.

The Griffon is an underpowered, civilian helicopter painted green - the veritable LSVW of the sky.

 

[Kirkhill]

This anything like the way you understand it Zoomie?

The Upgraded Huey with 2x GE T700-GE-401 for 2x 1723 shp

http://www.flug-revue.rotor.com/FRTypen/FRUH-1Y.htm  

The Bell 412 EP with 1x PWC PT6T-3D for 1x 1800 shp

http://www.flug-revue.rotor.com/FRTypen/FRB412EP.htm  

The Griffon with PWC PT6T-3D

http://www.army.forces.gc.ca/lf/English/2_0_45_1.asp?uSubSection=45&uSection=1

To be fair, the UH-1Y configuration will generate 100% more power than the predecessor which would put the predecessor into the same range of available power as the Griffon.

By the same token, it seems to leave open the intriguing possibility of re-engining the Griffons.

The UH-1Y supposedly can carry 4 crew and 8 troops on a 203 km radius mission with 30 mins on station and 20 mins reserves or about 1900 kg with a full load of 1400 kg of fuel.

On the other hand I do seem to recall NDHQ and Bell info saying the Griffon would be able to carry 14 persons.

Cheers.

 

[George Wallace]

Those 14 would have to be anorexic...

GW

 

[Kirkhill]

And a very short trip.

 

[Inch]

Actually guys, most helicopters are torque limited, not power limited. Even the mighty Sea King is torque limited, the engines are de-rated to 1500 shp from about 2200 shp. The Griffon is no different, PT6 engines are capable of putting out 1800 shp or more, I don't know off hand what the exact number is, maybe Laps can jump in here and fill us in. In any case, I have a feeling that the twin engined Griffon makes fairly close to the same power that the Sea King does, except that our all up weight is 20,500 lbs while there's is just under 12,000 lbs

My understanding is that the transmission and rotor mast (the vertical "drive shaft" that connects the rotor head to the transmission) are the problems. If you pull too much torque, you in effect, twist the rotor right off the helo, break the mast in flight or disintegrate the gearbox. The Griffon mast is fairly skinny, I'd say it couldn't be more than 3 inches in diameter. Whereas the Sea King mast is about 6 or 7 inches in diameter. My buddies have told me that over-torquing is a major concern while flying the Griffon, we really don't pay it much attention in the Sea King.

So to sum up, if you wanted to upgrade the Griffon, I'd start with the transmission and mast, then if you find it underpowered, upgrade the engines too. Keep in mind that a bigger stronger gearbox is also heavier, so there's a limit to how big and strong you can go. Otherwise you'll just be adding power so the helo can lift itself and that's not what you guys are looking for.

 

[Ex-Dragoon]

BTW Inch congrats on your 1000th post....kind of fitting its about aircraft .

 

[Kirkhill]

Thanks Inch,  figured you would have the answers.  Your explanation also explains the addition of that large triangular sail on top of the UH-1Y.


I dug this information out from an old edition of Janes' last night

CH118 (UH-1H) The original single engined Huey

Empty Weight  (EW) 2116 kg
Max Take Off Weight (MTOW) 4309 kg
Lift Delta (LD) ~2200 kg

Twin Blade
Lycoming T53-L-13 at 1400 shp.

CH135 (UH-1N) The Twin Huey purchased by the CF - also known as the Bell 212

EW 2753 kg
MTOW  5080 kg
LD ~2350 kg

Twin Blade
Pratt and Whitney Canada PWC PT6T-3 at 1290 shp

CH146 (Bell 412 EP)

EW 3146 kg
MTOW 5398 kg
LD ~ 2250 kg

4-Blade
Pratt and Whitney Canada PWC PT6T-3D at 1800 shp

UH-1Y

EW 5025 kg
MTOW 8390 kg
LD ~ 3350 kg

4-Blade
2x General Electric T700-GE- 401 at 2x 1723 shp = 3446 shp.

So at first blush, if the CH146 doesn't handle like the CH135 the problem isn't in the powerplant.  Any other thoughts?

And like Ex-Dragoon said Inch, congrats on you 1000th post.

Cheers.

 

[Inch]

Thanks guys, not only was my 1000th post about aircraft, but about my one true love, helicopters.  ;D

Kirkhill, just a point of clarity for the aircraft you listed, they're all twin engined except the single Huey. So the Griffon can actually put out about the same power or more than the UH-1Y but the Griffon engines are probably de-rated to a lower output so that they don't over torque the transmission.

 

[Kirkhill]

So to be clear Inch

the CH135 will actually generate 2x 1290 or 2580 shp while the Griffon (theoretical max) can generate 2x  1800 or 3600 shp?

Is that about right or am I still misunderstanding the situation?

Thanks.

 

[Inch]

Yep, you got it, if the engines were allowed to put out as much power as they could possibly make, that's what would be going into the gearbox. Again, I don't know the numbers for the Griffon's PT6's, but according to Pratt & Whitney's website, the PT6T-3D that's in the Griffon is capable of putting out 1800 shp, not too far off in my estimation eh?

http://www.pwc.ca/en/3_0/3_0_4/3_0_4_4_2.asp

Click on the drop down menu and select PT6T-3D and it'll give you the shp.

So yes, in theory, the Griffon is capable of putting 3600 shp to the gearbox. See what I mean? It's not the engines, those engines put out more than enough power. In fact they put out just as much power as the ones that were in the Twin Huey, which were de-rated to 1290 according to the Jane's you referenced. It's the gearbox and rotor system that are the problem. The engines in the Griffon are without a doubt de-rated down to something more manageable by the gearbox.

 

[Infanteer]

Ahh...it's like the difference between Engine Horsepower and Rear-Wheel Horsepower.  Too much engine horsepower and the tranny and/or rear differential goes "snap" and you're in trouble (even more so in a whirly-bird).

 

[Inch]

Well put Infanteer, that sums it up nicely.

 

[Kirkhill]

I don't like to here fast moving metal objects go "snap". It causes me to have palpitations.  What's it like at 5000 feet?

Would the 4-Blade rotor generate more torque than the old 2-blade design?