Beta Technologies' ALIA-250 electric aircraft

[redpoint5]

Originally Posted by Piotrsko

Helicopters have an issue above 200 mph where the retreating blade wont generate any lift and it generally turns into a corkscrew flight. The reason some experimental choppers have two blades counter rotating, but the drag bucket is phenomenal.

This hybrid has a top speed of 170, so I still don’t see how it’s better than an electric helicopter.

This design is neat, but it could have been done with oil burning engines (sorta) instead of electric, so why hadn’t it been developed already? I’m not seeing the added value over helicopter.

[freebeard]

Helicopters are noisy. I lived next to a field where CH-54s would drop down and snatch a double-wide mobile home into the air.

Hughes 500s were better. These little multirotors would probably be best.

[redpoint5]

Are 4 motors quieter than 1?

My experience with quads and helicopters so far has been that they are at least as noisy, perhaps moreso. I can hear my quads well before I can visually spot them.

[Piotrsko]

Well if they are typical quads the prop tips are supersonic.

The CH54 have blades that reflects the wide open unmuffled engine exhaust every time they pass over the fuselage while the hughes HAD a downward exhaust but AFAIK, it is still away from the rotor by a couple foot below the boom

The hughes NOTAR was really quiet because they used exhaust for the tail rotor and it wasn't under the rotor.

[freebeard]

Does anyone 3D print their own stealth rotors?

https://www.youtube.com/watch?v=2t3uCDJhce8

[cRiPpLe_rOoStEr]

Originally Posted by Piotrsko

The hughes NOTAR was really quiet because they used exhaust for the tail rotor and it wasn't under the rotor.

Makes me wonder how the NOTAR would interfere with an autorotation, assuming there would be no exhaust flow to redirect.

[Piotrsko]

Autorotate like a UH1 missing a tail rotor: keep the forward airspeed up above some number. In the UH1 it was 80 mph. You really don't need rudder to prevent torque turns autorotating, but it is used for direction control.
AFAIK, the NOTAR only lost rudder control if the turbine stopped solid. If it was still spinning you had some airflow

Pitcairn autogyros only had enough rudder to stop puller engine torque

[cRiPpLe_rOoStEr]

Originally Posted by Piotrsko

AFAIK, the NOTAR only lost rudder control if the turbine stopped solid. If it was still spinning you had some airflow

Turboprop engines usually feature what is known as a "free turbine" driven only by exhaust gases.

[redpoint5]

Wouldn't the main prop in this design be more efficient if enclosed in a shroud? Why don't prop planes have shrouds?

[samwichse]

Originally Posted by redpoint5

Wouldn't the main prop in this design be more efficient if enclosed in a shroud? Why don't prop planes have shrouds?

A venturi shroud can double the static thrust of a propeller, but the faster it travels the less the effect and the more drag from the shroud. Basically the advantage negates itself once it's moving fast enough through the air, but VTOL craft (like quadcopters) need lots of static thrust so shrouds can help.