Engineering Analysis of the 1907 Cornu Helicopter

[Rotor Rooter]

Engineering Analysis of the 1907 Cornu Helicopter (http://helicopter-history.org/Cornu/Cornu_LJpaper.pdf)

Linked to from The American Helicopter Society's Current News; 2007: Centennial of the Helicopter? (http://helicopter-history.org/)

[Sita]

Hello Dave,

Yes ,there has been some discussion about wether or not Corny made the first free helicopter flight.
We also could ask if the Wright brothers where the first to achieve manned motorized flight in a plane.
It only shows that a lot of history is written based on what others have written:hail:
Some books even call Sikorsky the "father of the helicopter" !!!
His VS-300 was a joke compared with what Flettner and Focke had done at that time !!

Gilbert

[Bruno]

Hello Dave,

Yes ,there has been some discussion about wether or not Corny made the first free helicopter flight.
We also could ask if the Wright brothers where the first to achieve manned motorized flight in a plane.
It only shows that a lot of history is written based on what others have written:hail:
Some books even call Sikorsky the "father of the helicopter" !!!
His VS-300 was a joke compared with what Flettner and Focke had done at that time !!

Gilbert

Fascinating stuff, Gilbert. Keep it coming!

Cita, how far have you progressed with your backpack helicopter? From what I can see, you have progressed the farthest of them all. Any news you can share with us?

[Rotor Rooter]

Cita,

Dr. J. Gordon Leishman is a professor of Engineering (rotorcraft) at the University of Maryland. IMHO, he is a person who is concerned with technical accuracy.

I believe that Igor's strength was Marketing, not Engineering.
The following will do little to change your opinion of Igor. :lie:

A few of Igor Sikorsky's claims as Firsts (http://www.pprune.org/forums/showthread.php?t=269323#14)

Dave

[Sita]

Hello Dave,

Sikorsky is without any doubt the one who succeeded in bringing the helicopter in to "the dayli life".
He was a very knowledgeable and skillful engineer but perhaps not as innovative as some want us to believe.
I could be VERY wrong in this but I don't think he ever invented something regarding the helicopter,he was a master in refining idea's !!
He played a significant role in the develoment of the "modern" helicopter however and should be honored for that.
Most of the features of the helicopter were invented/patented in the late 19 th,early 20th century (collective-cyclic pitch,one main-one tailrotor,lead-lag-flapping hinge etc....) so nobody could be credited as a single person to have "invented the helicopter".

Cita

[Arnie Madsen]

The first helicopter "that could really fly" is more and more being attributed to Jacob Ellehammer of Denmark who flew his machine from 1912 to 1916.
It was a co-axial and used servo flaps on the rotor actuated by cyclic controls. He was a clock and watchmaker by trade , built motorcycles and built his own engines which were an early type of radial engine for aircraft. There are even some claims a photograph dated as early as 1908 shows his machine flying in Copenhagen .
He was not looking for a lot of publicity and most of his experiments were conducted on an Island away from the public thus history overlooked his acomplishments.
Previous to the helicopter he was flying fixed wing aircraft, almost in parallel with the Wright brothers and was the second man to fly an aeroplane in Europe. There are also claims he may have flown before the Wright Bros. Like Cita said above ..."it depends who wrote the history"

Several years ago I was in contact with Ellehammer's great grandaughter in Denmark and encouraged her to gather all the history she could find and dedicate a webpage to him.

Arnie Madsen
Bell 47 G2

[JPHarrison]

I think that Sikorsky was shooting in the dark quite a few times during his development of the helicopter. Some examples:

1. Incorrect design of cyclic pitch mechanism.

The advance angle/phase lag of a rotor blade to a cyclic input was well understood by the time Sikorsky commenced his development of the VS-300. This technology had been developed over several years on the Autogiro. Why was the VS-300 cyclic control system designed with zero advance angle? This inevitably resulted in a significant out-of-whack rotor tilt to a cyclic pitch input, rendering the helicopter uncontrollable.

2. Dampers on the flapping hinges.

Why install dampers on the flapping hinges when flapping motion is aerodynamically damped? Rotor blade flapping behaviour was well understood by this time, again by virtue of its development on the Autogiro.

3. No dampers on the drag hinges.

Lack of aerodynamic damping on blade drag motion leads to ground and/or air resonance unless the drag hinges are significantly outboard of the axis of rotation. The VS-300 did not have such an arrangement thus was subject to self-excited resonance. Sikorsky's quip about forward flight being a minor engineering problem yet to be solved was due to air resonance occurring when forward flight was attempted in the VS-300. Again, blade drag motion, and the necessity for mechanical damping, was understood through Autogiro development, though still not as completely as the first two phenenoma noted above. The first rigorous analysis of ground resonance was conducted by Kellett engineer Robert Wagner in response to continuing problems with the KD-1 series.

The multitude of tail rotors was installed on the VS-300 when the rotor cyclic pitch control was removed to provide pitch and roll control of the helicopter through variations in thrust of those rotors.

During the late 1930s/early 1940s, a standard helicopter configuration had not emerged. Contenders included the following:

1. Sikorsky main/tail rotor.

2. Flettner intermeshing rotors.

3. Focke-Wulf lateral rotors.

4. Breguet co-axial rotors.

5. Bennett/Cierva main rotor/propulsive anti-torque propeller.

The US Army decided to fund rotorcraft development through resources provided by the Dorsey Bill:

XR-1: a Platt-LePage design based on the Focke Fa-61 lateral rotors layout; started as a private venture in 1939; HR-8143-funded as of July 1940; first prototype flew in May 1941; a second in December 1943; program canceled in 1946; no production.

XR-2: modified Kellett YG-1B with jump-takeoff capability; HR-8143-funded in July 1940; destroyed during ground testing; funds diverted to the XR-3 project.

XR-3: second Kellett YG-1B with improved rotor-head cyclic/collective pitch control system. After several years of inconclusive testing, Kellett switched to helicopters; XR-3 program formally terminated in early 1946.

XR-4: Sikorsky contracted in December 1940; first flight in January 1942; produced from 1942 to 1945; served with USAAF as RA with the U.S. Navy and Coast Guard as HNS-1 and the RAF as the Hoverfly Mk. 1; production canceled in late1945.

XR-5 and beyond were funded during WW II and included the XR-5 (Sikorsky), XR-6 (Sikorsky), XR-7 (Sikorsky), XR-8 (Kellett), XR-9 (Pitcairn, later bought out by Firestone) and the XR-10 (Kellett). The only helicopter to survive WW II was the XR-5, which became the H-5 and the civil S-51; all others were canceled shortly after the end of the War.

Sikorky's success in establishing the now standard rotorcraft configuration came about as follows:

"On July 24, five days after signing the contract with the Platt-LePage company, Army rotary-wing project officer Capt. Gregory traveled to the Sikorsky plant in Stratford, Connecticut, to meet Igor Sikorsky and review the status of the prototype VS-300 helicopter. Sikorsky obliged with a brief demonstration flight in the helicopter, and then he invited Capt. Gregory to test-fly the helicopter himself! After two test flights, Gregory realized that the Sikorsky machine might be a winner, and back at Wright Field, he strongly recommended that a backup contract be awarded to Sikorsky, despite the technically unproven concept of the single-rotor configuration.

After much digging, some $50,000 was found, and a contract was signed on December 17, 1940. Sikorsky knew that it would never cover the cost of the helicopter, but he felt that it was worth the risk. The new helicopter's designation was "XR-4." Later, stories circulated about a "plot" by Gregory and Sikorsky to destroy the autogiro industry, but the simple truth was that the Army wanted and needed the helicopter for its ability to hover. Had there been any truth to the rumors of a "plot," why was the lion's share of Dorsey funds awarded to the Platt-LePage proposal and not to the Sikorsky design?

One year later, just as the XR-4 was ready for its first test flights, the attack on Pearl Harbor plunged the United States into WW II, and suddenly, money flowed into helicopter programs."


Gregory basically told Sikorsky to stop messing about and license rotor control technology from the Autogiro Company of America to get rid of the cumbersome multiple tail rotor arrangement. XR-4s, developed from the VS-300, bore a plaque listing the patent numbers pertaining to Autogiro technology that they included..

Some of this material excerpted from

"The Dorsey Controversy" by Sergei Sikorsky
http://findarticles.com/p/articles/mi_qa3897/is_200304/ai_n9221889/pg_1

"Viewport: No Runway Required"
http://www.airspacemag.com/issues/2006/april-may/viewport-may06.php

[Rotor Rooter]

In the late 1930's and early 1940's the Europeans were working on twin-rotor configurations, whereas the Americans were primarily pursuing the main & tail rotor configuration. The Europeans lost the war, economically, and the two large single-rotor helicopter companies to emerge were Sikorsky And Bell.


For Sikorsky; two reasons given by William E. Hunt, of Sikorsky Advanced Design Staff, are;

"Not one successful single-main-rotor helicopter existed anywhere. It was just the type of challenge that Igor Sikorsky needed ...."

"The entirely unexpected and unfortunate delays suffered by the prime contractor, Platt-Le Page with its XR-1 ...... suddenly thrust the Sikorsky XR-4, YR-4, R-4 into the entirely unplanned limelight." These delays were, in part, due to the deteriorating cooperation between Nazi Germany and America.


For Bell; the reason might be the combination of a statement and a rumor. The statement comes from Kevin's third link in the thread 'Wilford Gyroplane Rotor System'. It contains the following sentence. "1938:-- [Young] Impressed by Igor Sikorsky's film, he concentrates on main rotor/antitorque tail rotor configurations.. The [perhaps incorrect] rumor has to do with the VS300 and a slow-motion film of the pilot's cyclic control movements.

Disclaimer; The use of a slow-motion camera is nothing more than a rumor and it cannot be supported by any fact whatsoever, to my knowledge.