PPRuNe Forums - View Single Post - 2 blade rigid rotor
View Single Post
Old 12th Sep 2018, 18:51
  #2 (permalink)  
Ascend Charlie
 
Join Date: Sep 2002
Location: Great South East, tired and retired
Posts: 4,382
Received 211 Likes on 96 Posts
Feathering will always have to be there, to allow us to change collective pitch, and to get differential cyclic pitch to move the aircraft in the chosen direction. I believe there were a couple of attempts to remove feathering bearings, and just twist the blades to get it, but apparently that was not successful.

2-blade teetering systems exist because they are simple and CHEAP. The CHEAP side of it makes them the accepted starting point for most low-time people, and they are generally the ones to have problems with it.

Next step up is 3-bladed articulated systems, allowing the blades to shuffle around the plane with the lead-lag forces. Then add more blades as desired. Articulated hinges can be replaced with rubber/ plastics as in the AS350 series.

The most rigid is the head of the BO-105 and BK-117, no flapping or lead-lag hinges at all. Flapping is allowed by the flexible blades, not by hinges.

Early experiments with rigid systems caused crashes - the experimenters couldn't see why their models would fly but the real things wouldn't. Then they saw that the models used bamboo blades which allowed flapping - so they devised the teetering head to allow flapping, and away they went.
Ascend Charlie is offline