Originally Posted by
John Farley
Graviman
If you have any specific questions that you feel are not answered in my lecture on the site you quoted then send me a PM and I will do my best to help.
I see you dabble with the R22. Take my word for it if you can hover one of those then (from a stick and rudder point of view) you would find the Harrier a doddle to hold steady in a hover.
...
John,
It is fair to comment that i dabble with the R22, since i can't afford to play! Once again i am grateful that PPRuNe allows me to discuss aircraft design with test pilots of your calibre.
Having read your lecture and some other resources, i do have a query regarding the stability of the Harrier in takeoff/landing hover. In particular how longitudinal and lateral dihedral remain effective in hover. This is something that puzzles me after the comment about the stability augmentation system being considered unnecessary for good pilot control. After the front landing gear adverse yaw problem i imagine a large vertical stabiliser helps, but the anhedral wing required for such a large amount of wing sweepback must counter lateral dihedral.
This really comes from my realisation that all helicopters have built in static stability, due to the rotor flapback (it becomes reduced and cross coupled in rigid rotors - thanks Nick). In theory if the cyclic was frictioned into position a teetering helicopter would remain still - i have no intention of trying this! The pilot is really there to provide dynamic stability, to damp down movements for the intended flight direction. Larger machines have SAS as part of AFCS to provide much the same service.
Which stability augmentation systems has the Harrier settled on? I will order the appropriate paper from I.Mech.E or SAE to understand in more detail, so just want an initial guide.
Thanks in advance.
Mart