Imagine if ....

okikuma

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Imagine if a modern day tractor gyroplane was built based on the de Havilland C-24.

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The original DH C-24 used conventional aircraft control surfaces as the Cierva C19. The modern version would use full rotor control. A Hughes 269/300 rotor head or an Air & Space 18A rotor head with 18A sized rotor blades could be used (non-Light Sport compliant). For simplicity, a secondary small motor mounted under the rotor head would be used for pre-rotation (no jump capability). The fuselage would be welded 4130 tube and fabric. The engine, a simple Lycoming 150/160 hp O-320 or 180 hp O-360 if one desires more horse power. The wings would be retained to hold fuel externally from the fuselage and keep the 1930s design appearance. The original DH C-24 empty weight was 1,280 lb with a gross weight of 1,800 lb. With lighter materials, the empty weight could reasonably be kept in the 1,000 lb range. Performance would be close to a Piper Super Cub. Operational cost nearly identical. As an experimental amateur built, the aircraft would simply be a novelty but very much an "eye catcher" at any airfield and airshow.

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Comments?

Wayne
 
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okikuma

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Location
Santa Clarita, CA
After searching for more information on the de Havilland C-24, I came across an interesting description on the de Havilland museum website. One comment was the fuselage came from a de Havilland Puss Moth. I find that hard to believe considering the obvious difference in the height, length and width of the C-24 fuselage as compared to the Puss Moth. There is really not much in common between the two and I doubt the Puss Moth fuselage assembly jib was used for the C-24 prototype since the Puss Moth was in continuous production from 1929 - 1933. The Puss Moth would perform better on 120 hp than the C-24 because the lift to drag ratio from the wings would be less than the lift to drag ratio of the rotor.

To quote Ken Brock, "Gyroplanes are draggy machines; very draggy."

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The second comment was about the twisted slab propeller. From various photos and the following video, the prop still looks the same to me, especially when the engine is being propped to start.


The comment of lack of adequate performance is understandable. A 1,800 lb gross weight with 120 hp gives a dismal 15 lb/hr weight to power ratio. And with a 34' diameter rotor, the disk load is 1.98 lb/sq ft. Predictable. Add one foot to each rotor blade and the disk load drops to a maximum of 1.77 lb/sq ft. Use the same 37' diameter rotor as the Cierva/Avro C.30, and the disk load drops to 1.67 lb/sq ft. Increase the horse power to 180 hp and the weight to power ratio will drop to 10 lb/hp.

Let us compare:

Pitcarin PCA-2
3,000 lb gross weight, 330 hp, and 45' diameter rotor
1.87 lb/sq ft disk load, and 9.09 lb/hp weight to power ratio

Cierva/Avro C.30
1,600 lb gross weight, 140 hp, and 37' diameter rotor
1.49 lb/sq ft disk load and 11.4 lb/hp weight to power ratio

Air & Space 18A.
1,800 lb gross weight, 180 hp, and 35' diameter rotor.
1.87 lb/sq ft disk load and 10 lb/hp weight to power ratio

McCulloch J2
1,600 lb gross weight, 180 hp, and 26' diameter rotor
3.02 lb/sq ft disk load and 10 lb/hp weight to power ratio

Wayne
 
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