Stationary Equipment Mounted on Rotor Heads

[Sparweb]

Our company has been asked to develop a means to install an antenna on the rotor head of a Bell Medium helicopter. This appears feasible to us because the mast is a hollow tube, and with a system of bearings that hold a tube fixed down the center, a rigid and non-rotating mount for the antenna would become available.

This has already been done on other helicopters, notably the OH-58's in US Army service, though the antenna that we propose is much smaller.

If any members of the forum have experience with these ships and their mast-mounted equipment, their comments would be appreciated.


Steven Fahey, CET

 

[MikeHalloran]

Note that the antenna may have to project considerably above the plane of the rotor blades, because they flex (and in the case of Sikorskys, flap) up under load.

Note also that the rotor axis is usually tilted relative to the earth when the rotorcraft is in motion, and the tilt changes with translational velocity.

I.e., if the antenna needs to 'see' the horizon all around, and not see the rotor blades, it will need to be taller than you might first assume.





Mike Halloran
Pembroke Pines, FL, USA

 

[Sparweb]

It only needs to see the sky: GPS.

Thanks, Mike

Steven Fahey, CET

 

[HANDCALC]

Sparweb,

No experience with the OH-58 mast-mounts, but on our Bell 205, we mounted a GPS antenna onto a bracket attached to the tail rotor gear box. This put the GPS antenna outside the rotor disk for better reception; however our aircraft maintenance personnel keep a watchful eye on it - due to the proximity to the tail rotor.

If this is of any value, let me know.

Ed Pinnell

 

[Sparweb]

Ed,

Funny you should mention that. There's a chance that the bracket you installed is the one I designed for this customer earlier this year.
Unfortunately, this solution isn't good enough for them. The 25 foot difference between the cargo hook and the tail introduces errors into the position data for the equipment they drop.

Thanks, keep 'em coming.

Steven Fahey, CET