Helicopter payloads

[PR19_Kit]

Yes, I know it's a bit of a 'fringe subject', but it's part and parcel of my first RAF 100 GB build.

Going through lots of Wiki pages about Western heavy lift helicopters, not those MONSTER Mils from the Eastern Block, there appears to be very variable levels of payload which don't stack up with the disc loading figures. See my table below :-

Skycrane payload        = 20000 lbs    4.91 lbs/sq ft

Sea Stalion payload     = 10000 lbs    8.95 lbs/sq ft

Super Stallion payload  = 36000 lbs    7.34 lbs/sq ft

Chinook payload          = 24000 lbs    4.28 lbs/sq ft

Rotodyne payload        = 11000 lbs    6.14 lbs/sq ft

Merlin payload             =  9000 lbs    3.00 lbs/sq ft

Now the question is, does the disc loading, the second column in the table, take any account of the no. of blades? Does it mean the area of the rotor disc itself, or is it the area of all the blades taken together?

I might say I'm surprised that the Skycrane has twice the payload of the Sea Stallion, when I thought it had the same engine-rotor system, but only half the disc loading?

[kerick]

Then of course, there is the payload vs range issue. Skycranes can lift a lot but don't expect them to carry it very far IIRC. Not sure if that is a part of your question.

[AS.12]

Disc / disk-area is just the area of swept air.  Disk-loading is not particularly useful when designing a helicopter since it's not a 'metal' physical value but it does give an idea of the general efficiency of the rotor and how well it will autorotate.  Actual design is based on the blade-area, which determines the amount of rotor thrust.

Payload per airfoil area is blade-loading.  A lower blade-loading means that the advancing blade stalls at a higher speed, or conversely you can trade-off that extra lift margin for a lower RPM ( hence human-powered helicopters have very low blade-loadings ).  Unfortunately I've never seen blade-loading specified in general sources.


Re: disk-area vs payload, the payload weights stated online are often only half the story.  An S-65A Sea Stallion could lift 19,000lb at overload weight which is in line with the S-64 Skycrane and reduced slightly due to the fuselage blocking some downdraught. An EH.101 can sling 5 tonnes which is about 11,000lb.

[PR19_Kit]

Very handy AS.12, thanks.

Your explanation stacks up with what I figured about the blade v disc area. As you say it's madness that blade loading never seems to get mentioned in these circumstances, whereas wing loading for fixed wing aircraft is very common.

I'll have to measure the sizes of the blades on all my umpteen large helicopter kits, but my money's on the Chinook, it's blades have twice the chord of most of the others.

[sandiego89]

My Janes lists the main rotors as:

Diameter/Chord/disc area

CH-47: 18.9m (60 feet), .81m (2feet 8 inch), 525.3m2 (5,655 square feet both blades combined)
CH/MH-53E: 24.08m (79 feet) .76m (2feet 6 inch), 455.38m2 (4,901 square feet)

As for lifting oomph, in the western fleet it is hard to beat the 53E.  The King Stallion is even more impressive.  I have the pleasure of having H-60s and MH-53s over my house on a regular basis and the Super Stallions absolutely rock and rattle the house.     

[PR19_Kit]

Hm, that's very interesting. 

It would seem that even though the Chinook has a greater overall blade area, which is just what it looks like on the models, that the Super Stallion can lift more. Or maybe they allow it to lift more?

What's a King Stallion anyway? I don't think I know that version.

[kitnut617]

What's a King Stallion anyway? I don't think I know that version.

Do a google on CH-53K Kit  And no -- it's not for the RAF 

[PR19_Kit]

What's a King Stallion anyway? I don't think I know that version.

Do a google on CH-53K Kit  And no -- it's not for the RAF 

Thanks Robert, that's certainly one big, fat machine. It looks like a Super Stallion that's been pumped up to a couple of hundred psi.

I'll be expecting an Italeri kit of it before the year is out. 

[jcf]

The area of the fuselage below the rotor disc is also a factor.

Shortening the Sikorsky S-61L/N airliners by taking out the fwd fuselage extension increased
the slung load rating by 1,000lbs.

I worked on the shortening project at Helipro, and two of us could easily carry the removed
section, so the weight removed was negligible in terms of the payload jump, which of course
meant a bigger load of logs each time.

Speaking of $hithooks, check out the big Boeing drawing here:
https://drawingdatabase.com/boeing-ch-47-chinook/

[PR19_Kit]

That's something I've not heard of before, thanks JCF. 

Amazing that removing such a small part of the airframe could have such an advantageous effect. That explains why the Skycrane has such a narrow fuselage backbone, and makes me wonder on the logic of making the King Stallion so much wider. Mind you, the latter seems to be predicated on getting a Humvee INSIDE the fuselage.

Perhaps I should think about narrowing the Rotocrane's fuselage? Nah, that part's done now. 

[Rheged]

I was once told by a former FAA pilot that the maximum safe load for an early Whirlwind was a SHORT verbal message!

[Old Wombat]

I was once told by a former FAA pilot that the maximum safe load for an early Whirlwind was a SHORT verbal message!

He was a fixed-wing pilot, wasn't he!?

[Rheged]

I was once told by a former FAA pilot that the maximum safe load for an early Whirlwind was a SHORT verbal message!

He was a fixed-wing pilot, wasn't he!?

Nope!!  He actually flew Whirlwinds off Ark Royal.

[Old Wombat]

With the Whirlwind he's probably on the money.

I suggested fixed-wing because I know a few RAN Tracker & Skyhawk pilots who refused to fly in our helo's for pretty much the reason stated.

[PR19_Kit]

While talking to an ex-FAA Wasp pilot at Old Sarum recently, he mentioned that the early Wasps could carry one torpedo and the observer or two torpedoes and just the pilot. He said they were very grateful when they fitted the uprated engines.........