Nord 501

[63cpe]

Would it need any sort of 'tail' if the fans rotated in opposite directions?

MM, good question. I suppose not.  But me thinks the pilot wants some sort of control over the plane when  airspeed is low. Just like the puffers in a Harrier.

David aka 63CPE

[63cpe]

I've ordered two ducted fans from a local RC aircraft shop.
 

Good thing! looking forward to you plans.

David aka 63CPE

[zenrat]

I've ordered two ducted fans from a local RC aircraft shop.
 

Good thing! looking forward to you plans.

David aka 63CPE

I need the fans in my hands to really fire up the muse.
But I have thoughts regarding a Skyvan or a Sea Stallion...

[jcf]

The system on the N.500 doesn't have "ducted fans", it uses shrouded 5-bladed variable pitch
propellers mounted towards the rear of the shroud. The propeller gearbox is in a teardrop
shaped body in the centre of the shroud supported by the fixed struts in the fwd. part of the
shroud. The props were cross-shafted so that an engine could be shut down in flight if so desired.
The engines were mounted in the short boom to the rear of the wing, the sections of wing
between the shrouds and fuselage rotated with the shrouds. Four control vanes, essentially
"elevators", were mounted on the aft end of the shroud in a diamond pattern. Control in vertical
and horizontal flight - yaw, pitch and roll - was accomplished by varying propeller pitch and
speed, control vane and shroud position. The fixed fin and tailplane were simply there to increase
stability in yaw and pitch. With that version of the Nord system there is no need for movable
control surfaces at the rear of the fuselage or a NOTAR type system.
The proposed N-500 Militaire, the gunship, and the 501 transport designs, had different types
of shrouded propeller system. On the 500 M it was reduced to basically a pair of closely set
concentric rings around the propeller - resembling a two part Townend ring and no control vanes.
Based on the model photos it appears that just propeller speed, pitch and shroud position would
be used for control.
The system on the 501 transport has two larger truly concentric rings spaced apart and a section of
wing bisecting the shroud that appears to include moving control surfaces.
The 500 Militaire and 501 transport designs both have a fin and rudder.
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I have CG questions. 

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The N.500 "Cadet" engine, transmission, propeller drive and mechanical control system.
Needs more rods. An N.501 drawing as well.
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[63cpe]

Thank you JCF for sharing this extensive information. It's very good indepth information on the controlsystems in the Nord 500 and 501. I have the book on French secret concepts. In it is the Nord VTOL concepts.

I'm concerned about the CG of the Nord 500 Militaire too. That's why I left the tailboom as is, moving CG to the rear.
I have to make the diamond shaped control vanes and install them below the ducts.
Maybe there is no logical need for the NOTAR system anymore as control is sufficient via the controlvanes although i'm still concerned about its CG and the NOTAR could help by balancing CG out.

David aka 63CPE

[Rick Lowe]

Oo, a use for the Matchbox Hueycobra that I've replaced with the Special Hobby one - and a project I've been thinking of myself; all good ideas, thanks David!  

[jcf]

A fixed tailplane and rudders on the vertical control surfaces would
probably be the best combination.
The control vanes would handle
pitch control without difficulty, no
elevator would be required. The
vertical fins with rudders would
improve stability in yaw and, most
likely, improve control in the lateral plane rather than just changing
the pitch and speed of a propeller
to create differential thrust. That
works but achieving fine control
would be difficult. The propeller
pitch/speed change concept would
work well at low speeds, but not as
well as the speed increases. Making
it so that the outer segments of the vanes could function like ailerons,
when needed, would also improve
controllability in the lateral plane
due the fact that it's actually the
ailerons that do most of the work in turning an aircraft.