Max All Up Weight

[Tuckunder]

Hypothetical question.

If we fitted new (heavier) blades to our Cab, would it effect the MAUW of the aircraft. In flight, the blades are flying so I reckon the MAUW should increase by the increase in blade weight. I am sure Nick could put us right.

[The Nr Fairy]

Not an engineer, so this may be complete bolleaux. Is not the MAUW a certification limit ? Therefore to increase it requires re-certification ?

All you're achieving, it would seem, is a reduction in payload.

[Gaseous]

I seem to remember this one doing the rounds before.
(I think I may have asked it). The answer then was more or less this.

The blades have to lift their own weight as well as the rest of the machine. Any weight you add comes off the payload unless you get an increase in maximum gross weight certified. (which you almost certainly wont). The weight and balance schedule will need to be amended.

The same applies if you add avionics, soundproofing, fluffy dice etc.

Phil

[NickLappos]

Tuckunder,

That is a question that is best answered by the designer, or a qualified engineer who becomes familiar with the design. My first guess is that the extra blade weight might actually subtract weight from the MAUM, since the stresses for the greater centrifugal forces will impact the rotor head, and could make the head have less structural margin.

If the head is grown in size and strength with the blades, your logic could very well be correct, however, as long as the rotor blades do not add big changes in the bending stresses they impart on the mast and transmission. If the head is a teetering, "semi-rigid" head, the bending is the same, if the head is articulated, the bending can go up a bunch.

[Arm out the window]

It would depend on what was the limit for the MAUW - for example, for the B206 the max all up for internal loads is the skid loading on the ground (recently been upped with an AD), so putting heavy blades on would definitely reduce your payload.