Tilt Rotor questions.

[AdamFrisch]

Hi. I'm curious about a few things on these.

1. As I understand the BA609 has no rudder at all - that's done by differentiating the pitch on each prop in flying mode. Fine, got that. But how is this actually achieved in reality? I'm assuming that differential pitch/collective when the nacelles are upright and in heli mode is the equivalent to moving the cyclic sideways. Obviously, when the nacelles are in flight mode, this should be roll on the stick, but do they still effect the pitch of the blades and control the yaw then?

2. How about when the nacelles are at 60 degrees and the aircraft is going for a rolling landing?

3. The rear T-tail pitch stab - is that coupled with the cyclic control so that it performs alongside the nacelles?

4. Are the proprotors fully articulated as on a heli, or are they just collectively controlled? Because as far as I can understand there is no real need for complete cyclic control of the proprotors, if:

Differential colletive on each proprotor results in roll.
Counter tilting nacelles creates yaw.
Tilting nacelles in unison back and forth creates pitch.

Is this assumption correct?

Appreciate all your answers.

[Shawn Coyle]

I don't believe there is any significant ability to tilt the nacelles differentially.

[mckpave]

While my background is V-22 I did recently read a technical article on the 609 flight control system and think I can give you a few answers.

1. The 609 proprotor only has longitudinal cyclic movement, lateral control is provided by differential collective. This greatly simplifies the rotor system and allows for a 3000 psi hydraulic system.

2. Don't know exactly about the flight control laws vs. nacelle setting for the 609 but the V-22 "feeds in" RW/FW flight controls depending on the nacelle setting. This is accomplished by the flight control computers and at sometimes you have a little of both happening. With your example, at 60 nacelle the aircraft uses pure RW control laws, I can only assume the 609 is similar.

3. Ya got me on this one, don't know how the t-tail works but it's a much better configuration than the V-22's twin tails, gets the control surfaces out of the dirty air from the proprotors.

4. I think my answers in #1 give you your answer here. In a nutshell, diff collective gives you roll in helicopter mode, diff thrust gives you yaw in airplane mode. You definitelly don't want the nacelles operating independently, in the V-22 they are kept within 1.5 degrees of each other or the flight control computers will stop movement.

Hope this helps.

[Dave_Jackson]

This site give a good pictorial view of the flight controls for the V-22.
Go to V-22 Osprey (http://www.globalsecurity.org/military/systems/aircraft/v-22-flt-cntrl.htm) and then in the right hand column click on 'V-22 Flight Control'

This site has an open view of the Eagle Eye's proprotor head
Go to http://epic.org/privacy/surveillance/spotlight/0805/eagle.pdf and then go down the left hand column to 'DRIVE SYSTEM - Proprotors'

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Edit: To add BA609 specific info.

DESIGN & DEVELOPMENT OF THE BA 609 CIVIL TILTROTOR
HYDRAULIC SYSTEM ARCHITECTURE (http://www.vtol.org/pdf/61PropulsionII.pdf)