Rotorcraft Ltd. was reconstituted as the Cierva Rotorcraft Ltd, subsidiary of The Cierva Autogyro Co, and work commenced on the new "Grasshopper" Mk.III which was based on the dynamic systems of the earlier aircraft, but with a new four-seat fuselage incorporating a slim tailboom with a fin and rudder and powered by two 135hp Rolls-Royce Continental O-300 piston engines. This was designated CR.LTH-1 (otherwise known as the CR-Twin) and the first aircraft, G-AWRP, first flew in 1969 followed by G-AXFM (GB-2) later that year, and a third pre-production machine, G-AZAU (GB-3) in mid-1971. This latter aircraft was fitted with 210hp Continental IO-360-D engines, and the production variants were to be the CR.420 with 210hp Continental TSIO-360-A engines and the CR.640 with 320hp Continental Tiara T6-320 engines. Development was eventually abandoned in 1975 due to lack of further financial backing.
R.Simpson "Airlife's Helicopter and Rotorcraft", 1998
Technical data for Cierva CR.LTH-1 "Grasshopper"
Rotor diameter: 10.06m,
fuselage length: 8.58m,
max take-off weight: 1564kg,
max speed: 222km/h,
cruising speed: 193km/h
|Prof Reg Austin, regaustin=btinternet.com, 19.08.2013|
Re the question of co-axial rotors, the ML Aviation Sprite unmanned helicopter had co-ax rotors and was very successful, flying in several countries of the world by day and by night, off land and off ships.
It demonstrated, to many people's amazement, how impervious it was to wind conditions which grounded other aircraft.
It also showed the better performance of the co-axial rotor system compared with other configurations.
|Dr Peter Holmes, peter=peterholmes.info, 07.06.2013|
I too worked on this project at Finchley Road and Redhill aerodrome. I was looking after the instrumentation, and evaluating the data, as well as approving flight plans. I took this over after Dick Parker left the firm. He had previously been chief development engineer and left to start his own company. I was involved with testing with the two rotors running on a bare airframe. The basic problem with the aircraft at that time lay in the closeness of the blades which, being very flexible, could deflect enough to hit each other and the mechanism between the two swash plates at that time, was unable to prevent this. I was acting as flight engineer on two occasions when the blades came into contact with each other. The second of these was a pretty dramatic event!
Following a later incident on a tethered test, I grounded one of the rotors but I was over-ruled and it was put onto an aircraft. That's when I left.
Is there anybody working on a technology update and production? I know investors who are interesting in an investments in co-axial helicopter. Thanks. Joni
|Neil Corbett, neilcorbett10=yahoo.co.uk, 07.12.2011|
Dear Michael,I have featured your late father on my test pilot tribute website, however, i would like to add more information and also pictures of him 'in cockpit' or with the helicopters he tested. If you can help in any way, i would be most greatful.
Hope to hear from you,
All the best from Scotland
|Mike Reed, michealread=btinternet.com, 08.09.2011|
My late father was KEN REED,the TEST PILOT on the Grasshopper.I have various photos plus all his reports on flights.
|john k.cartwright, peggyhunt61=yahoo.com, 28.07.2011|
i john k. cartwright,was the prelemanary design engineer on this helicopter in 1965.
|soccer, goodeday=gmail.com, 12.06.2011|
Tony Higgins and myself running the bare platform with blades on one of the two co-axial rotors only.
|Don Hillberg, donhillberg1=hotmail.com, 23.06.2010|
The Sikorsky X2 is a Ridgid system No drag henges,No flap henges only feathering.Doesn't need flyby wire,I like the Grasshopper,looks nice,all but one Coaxle rotor A/C have a problem in autorotation,control reversal in yaw,the QH 50 solved this little thing,just a note:
|Ron Segall, ron.segall=btinternet.com, 07.05.2009|
I also worked on the CR Twin with Dr Opatowski and would love to contact him, but an e-mail to his address comes back as unrecognised.
Do you have any further contact details?
|Dr. T Opatowski, topabook=bezeqint.net.il, 27.03.2008|
In reply to Pierre Terrail: I left the project soon after the stage shown in the photograph when Mr. Shapiro wanted me to join his office (Servotec) in an unsatisfactory position rather than work as a consultant from my own firm of Technical Investigations Ltd. I should also point out that the MK 2 version had its engines in the rear rather than the previous front location. As far as the rotor system is concerned it was very close coupled and the rotors were (theoretically) held apart by a rigid conta-rotating structure patented by Mr. Shapiro. If thay are far apart, as per the Russians, it is not very efficient. My analysis of the system concluded that it would not work safely unless there was a very sophisticated higher harmonic blade pitch control system though something could be done with an appropriate delta 3 hinge. I think that the Sikorsky high speed helicopter under development, which has close coupled contra-rotating rotors, has individual blade pitch control.
|Pierre Terrail, pierreterrail=hotmail.com, 16.10.2007|
Dear Dr. Opatowski, may we have an evaluation of this coax helo: vibrations? performances? why there is no follow up? Why this is not a success? Why aren't we seeing more coax in the sky???
|Dr. T. Opatowski, topabook=bezeqint. net.il, 26.07.2007|
I carried out some of the early development work on this aircraft at Redhill (on a consultancy basis) and have a photograph of the engineer Mr. Tony Higgins and myself running the bare platform with blades on one of the two co-axial rotors only.
Do you have any comments concerning this aircraft ?