Good explanation here of the different types of rotor heads -
http://www.transglobal-aerospace.co.uk/1-504/Ch3.htmAlthough I would disagree with what they say is a semi rigid rotor head, I was taught that was a 'Teeter mast' eg the classic Huey.
The Lynx has a semi rigid head and bears no resemblance or shares the traits they say comprise a semi rigid head.
Poss difference in US vs European thinking/definitions?
This is what I was taught -
1st quick explanation - Blades have can have 3 planes of movement-
1) lead/lag - The blade can move fwds and backwards slightly from its central spanwise position.
2) Flap - The blade can rise and fall to allow equalisation of lift.
3) The usual rotation to change the angle of attack (pitch change).
a) Teeter Mast - i.e. the UH-1, all blades pivot around a central point and are in effect one solid mass. i.e. you pull one blade down, the other will rise, but you can have them with 4 blades.
b) Rigid - All movement is allowed for by flexing/twisting areas of the main rotor head. (rare)
c) semi-rigid - i.e. Lynx - Lead/lag and flap are allowed for by areas of the main head to flexing rather than have hinges. Pitch change is allowed for by actaul bearings.
d) fully articulated - Lead/lag and flap use physical hinges, pitch change uses bearings.
One thing I can tell you, the Lynx fitted with the composite main rotor blades (ones with the paddle on the end) was a ***** to do initial tracking on, more unstable than 'normal' blades in the hover but a hell of a lot of fun to fly around in on flight tests.
Grippen - Thats a semi-rigid head.
Inverted as in loops, rolls is not theoretical, Lynx rolls extremely well.
One of my favourite Lynx airshow stunts they do
i) Climb upwards and rearwards increasing speed as it went.
ii) At max rear speed haul the cyclic all the way back and pull max collective.
ii) The aircraft went rearwards over onto its back then into a dive.
Quite spectacular.
