How Heavy Is My Helicopter

[bugdevheli]

When weighing a helicopter should i deduct the weight of the main rotor and
hub, or include it in the total weight? The question arose because say a
Robinson22 is given as 850lbs empty (or thereabouts) and given that the
blades and hub weigh around 70lbs,would it be reasonable to assume that
once the machine leaves the ground, the blades and hub no longer form
part of the total weight as they are self supporting.

Thanks Bug

[imabell]

oh me oh my, where do we go from here???:ugh: :{

[ShyTorque]

My dear chap, you saw it first - after you! ;)

[Teefor Gage]

oh me oh my, where do we go from here???

The old nutmeg of carrying a load of caged birds comes to mind. If you ensure that all the birds are flying inside their cages, you don't need to include their weight when it comes to load and balance.........

Next question could be-
"When weighing my helicopter, how much pitch should be applied to compensate for the weight of the rotor system?"

[MBJ]

I'm quite strong - I can easily lift 100kg. So, I got hold of my ankles and lifted hard. I left the ground and floated for whole minutes. I weigh nothing for a while! Damn, then I woke up!

I think you may be confused!

[Ascend Charlie]

Don't forget to allow for the increase in mass as you approach the speed of light.

And because time slows down, your fuel will last longer.

But because your aircraft shrinks at warp speed, the cg calculations become more important.:eek:

[bugdevheli]

WHAT !! Me confused. Never. MBJ NO you have to get somebody to hold your head. T4 Let me have the weight of your particular rotor system and blade details and i will tell you the pitch required to overcome rotor system weight

[victor two]

Valid question really. The same as a 747 weighing 250 tonnes less as soon as it takes off because the wings and fuel inside the wings are self supporting in flight ......

[slowrotor]

What is the basis for your question?


For airplanes, the designer can deduct the weight of the wings in calculations of flight loads. In fact, the wing weight actually reduces the load on the main spar.
For a helicopter, I think most designers would not bother to deduct the blade weight as it is rather insignificant.

[SASless]

Blade weight is insignificant?
Ever picked up a Chinook blade....or a CH-53 blade?
At what point do you quit weighing the rotor system? At the blade root, blade root plus damper, blade including damper and head, or from the non-rotating swashplate up.....or from the output end of the hydraulic jacks in the control system?

Does condition of flight enter into the equation....very high rate of climb add weight, autorotation reduce weight?

[slowrotor]

SASless,
From "Principles of helicopter engineering" by Jacob Shipiro, the author discusses the gravity force on the blade elements. He states, "Numerically, the weight component is insignificant except in a stationary rotor or at a very low r.p.m."

I just read the stuff, don't always understand the dynamics.

This may not even apply to Bugs question.

[NickLappos]

bugdevheli

This sometimes comes up, and shows how little we teach people about limits. The test helicopter that measured the forces on each component, and did the autorotations and slopes and all the other stuff had a rotor head, and was weighed the same way you are supposed to weigh your helo. In that case, the limits apply to that configuration.

Remember, when you fly, you mimic the tested configuration in every way, and the weight you achieve is compared to the weight the manufacturer tested at.

How about you remove the tail cone to save weight? Of course, all turns on the next flight have to be to the right.

slowrotor, what that quote refers to is that the blades forces come from many places, especially centrifugal force, rotor lifting loads and blade weight. Of the three, the weight is insignificant as a structural load on the blade itself, except when the head is not spinning (where the CF is not there to help stiffen the blade).

[SASless]

Would not the "gravity force" be the same in all phases of flight in that "gravity" is a constant. The "bending" moment on slowly turning or stationary blades would be much greater due to the lack of centrifical force (or is it centrifugal /centripedal force).
Nick...did you and Lu ever figure out what to call that "force"?
"Air Pockets" usually describes the contents of a helicopter pilot's pockets.

[NickLappos]

SAS a whirling beam derives almost 1000 times more stiffness from the CF as from the gravity forces.

And the force is actually a centripital force, even Lu would agree (sort of..)

[IFMU]

When weighing a helicopter should i deduct the weight of the main rotor and
hub, or include it in the total weight? The question arose because say a
Robinson22 is given as 850lbs empty (or thereabouts) and given that the
blades and hub weigh around 70lbs,would it be reasonable to assume that
once the machine leaves the ground, the blades and hub no longer form
part of the total weight as they are self supporting.
Thanks Bug
Bug,
If you replaced the R22 rotor with a solid cast iron one that weighed 700 lbs, would it no longer take anything to lift it once the machine left the ground? Nope, weight is still weight, something has to lift it.
For airplanes, the designer can deduct the weight of the wings in calculations of flight loads. In fact, the wing weight actually reduces the load on the main spar.
What is going on here, as you put stuff on the wings like engines or fuel, is the maximum bending at the root of the wing is reduced compared to if all the fuel/engines was in the fuselage. You pull G's, the wings flex up and bend near the fuselage. If you have tip tanks, said g's pull the wings back down and relieve that bending moment at the wing root. But you still have to carry the weight.
-- IFMU

[Hidden Agenda]

Are we talking actual weight or “corrected” weight?

[Johe02]

Ahh. . . now I see why JAA changed the subject of Weight & Balance to Mass & Balance. .:8

[Farmer 1]

Bug,

Let's be serious for one minute. Oh, all right, half a minute.

What is the point of introducing an extra sum when calculating the weight of the machine? Should you ever be flying and the machine and rotor system part company, then I agree, it might be a tad quicker to work out the aicraft's actual weight, but I cannot imagine any other occasion when it would be useful to know the weight minus the rotor system.

Being practical, sorry.