I am not sure I subscribe to the idea that Hamilton Standard led the way with variable pitch propellers.
The Hele-Shaw - Beacham constant speed propeller was patented in , first flew in , Gloster got onboard in and they were tested by the RAF in .
The NACA paper TM-459 published in April described the operation of the propeller, and no doubt that information would have found its way to Hamilton Standard.
Hele-Shaw and Beacham were inventors with nothing behind them. Signing a deal with Gloster got the idea from paper to flight, however it appears to have stalled at that point. There was not much money being injected into the industry in the UK at that time, and it would have been a huge financial risk to start a propeller factory from scratch with a feeble market.
What Hamilton Standard did achieve was to develop and commercialise the concept, and at that time the market was ripe with the airlines seeing the benefit of CS propellers.
There were several different mechanisms for operating the pitch change mechanism and we can argue about who patented what and when. Hamilton Standard was able to put the basic idea into production and develop it through several steps. Perhaps because the the American Airlines and airplane makers embraced the concept (along with the US military) and gave them a profitable market. At some point in the late 30s the Hamilton Standard propeller (in one or another of it's versions) was Licenced in 16 (?) countries.
HS was part of United Aircraft (P & W, Vought and others) and the Wright Corporation, their rivals, came up with the Curtiss or Curtiss Electric propellers so they wouldn't have use their rivals product.
As a practical matter HS did lead the way, if not with the basic concept, then with a practical, easy to operate and maintain device.
From a Article in Flight magazine
"The outstanding opinion of the majority taking part in the discussion appeared to be that the gains were so small as not to warrant any considerable increase in weight. "
This discussion was in .
"It emerged from the discussion that item (1), i.e., greater thrust at take-off, was considered the principal advantage and that the extent of this was at the maximum the percentage of engine h.p. lost by the drop in revolutions which the fixed pitch airscrew involved, and that this was likely to be of the order of 10 per cent. Moreover, in the case of the supercharged engine, the advent of which was originally the chief reason for the renewed interest in V. P. airscrews, the advantage was offset by the fact that this type of engine could be made to give a temporary increase of power at take-off by increasing the boost pressure."
Later "Although the original Hamilton Hydraulic Airscrew patent (which was for a two-position airscrew) was applied for on May 25th, , that is 4 1/2 years after the Hele-Shaw Beacham patent, such was the energy applied by our American cousins that this airscrew was actually in production before the Hele-Shaw-Beacham and subsequent tests definitely established the advantage of the V.P. airscrew for take-off on modern aircraft."
and " the reason that the American two-position airscrew was first in production was mainly due to the fact that for a period the Americans were ahead in commercial aircraft design and certain types of aircraft existed in the States for which V.P. airscrews were a paramount necessity before that condition arrived in this country."
Trying to use variable pitch or constant speed airscrews on fixed landing gear bi-planes was not going to show a large increase in performance or fuel economy in cruise.
Unfortunately for the British that meeting of the Royal Aeronautical Society seemed to "seal the deal" on British use of constant speed or variable pitch propellers for almost 10 more years. Despite efforts by DH and Rotol (ROlls-brisTOL) the officials didn't want to use variable pitch propellers and indeed, they 'cheaped out" and used 2 pitch props (the simplest, least effective form of variable pitch propeller) instead of the infinitely variable (within limits) constant speed prop that Hele-Shaw/Beacham had patented and test flown all those years ago.
I found some interesting information in Fedden book.
From "Fedden - the life of Sir Roy Fedden" Bill Gunston RRHT / p196-201
One important area where Fedden was not his own master was in the propellers his engines drove. From the First World War onwards he had carried on a missionary campaign for variable-pitch propellers, and he fretted at the woefully slow progress Gloster Aircraft was making with the only promising British v-p propeller, the Hele-Shaw Beacham. One of these had performed well in flight trials in on a Gamecock, but Fedden then kept badgering Harry Folland, Gloster chief designer, because nothing more seemed to be happening. Bristol themselves then picked around the edges of the problem. The Engine Department made simple propellers with fixed-pitch blades of magnesium and, from , of "densified" wood, with multiple laminations bonded under heat and high pressure to form an extremely strong blade much tougher than the traditional wooden type. Unfortunately, Fedden had no resources to spare for the complex engineering of a new v-p mechanism.
In September , on one of his visits to the Bliss company at Brooklyn, he paid a call on the Hamilton Standard Propeller Co. This firm had patented and perfected a simple v-p hub with two or three blades balanced by bracket-type counterweights at the roots and capable of operating either in a fine pitch, for take-off and landing, or in a fully coarse pitch for cruising. This was the only v-p propeller that had ever been fully approved, or put into production. Fedden thought the Hamilton terms a bit steep, as regards both licence fee and royalty, but he decided to take out an option for the British market to break the stumbling block that was hurting both his engines and, increasingly, British aircraft.
The Bristol Board turned the idea down flat - partly, Fedden was convinced, because they considered their employee had no business to keep involving himself in such peripheral affairs. Fedden became exasperated trying to persuade them of the size of the market, and of the way in which fixed-pitch propellers were rapidly becoming outmoded everywhere that the Hamilton had penetrated. Fedden, with Frank Nixon, interested de Havilland in the American propeller, and dropped his own option. He then unburdened himself to the sympathetic Dowding. The air marshal welcomed the introduction to Britain of the proven Hamilton propeller, but he also expressed his faith in the Hele-Shaw Beacham design and asked Fedden if he would supply the Air Ministry with two propellers to this design. Fedden agreed at once, because he too believed in the British hub and was impatient at the way it was hanging fire. Gloster Aircraft were not in the least offended at Fedden taking the order, and Hugh Burroughes and Folland collaborated with him in setting up a propeller design office at Bristol and in tracking down the original Hele-Shaw designer, Milner. Though Fedden could not have set up a team to develop a propeller from scratch, he welcomed the chance to perfect this existing design.
His new propeller group quickly discovered that the faulty operation of the British hub had been due to distortion of the casing, which allowed oil to leak and reduced the pressure available to swivel the blades. The obvious answer was a stiffer hub, and within weeks a casing had been machined from a solid forging like the banjo of a truck back-axle. There followed a most successful ground test, the first ever with a British v-p propeller, and then a 100-hour flight programme with a Mercury-powered Gauntlet fighter. But by this time, in , de Havilland Aircraft had followed Fedden's advice, picked up the Hamilton licence, and was tooling-up for quantity production. From the summer of Fedden had added an oil control valve for the Hamilton propeller to all his latest production Mercury and Pegasus engines, and in fact roughly nine out of every ten of these engines sold throughout Europe up to were fitted with Hamilton three-blade propellers (to the chagrin of the Bristol Board). Another propeller rival was Rolls-Royce, which had also been given an order for two HeleShaw propellers by Dowding and had been developing it along different lines. Bristol's hub used a cylinder with radial pins sliding inside the forged steel hub, while the Rolls design used a fixed inner piston carrying an external sliding cylinder driving the blades by push-pull rods. Fedden was not anxious to see two versions of the Hele-Shaw; his passion was for mass-production of the best standardised article. And what really depressed him beyond measure was that the Bristol Board still wanted to have nothing to do with propellers. This time the main excuse was that such a venture would not be worth the candle as de Havilland was taking all the business with the Hamilton propeller!
Fedden once again decided to do something he called "rather unconstitutional". He invited two of the top Rolls men, Arthur (later Sir Arthur) Sidgreaves and E W (later Lord) Hives, to lunch at the Royal Thames Yacht Club in London - Fedden's favourite club, and suitable neutral territory for a chat with his greatest rivals. He expressed his concern at the failure of the Bristol Board to authorise production of his propeller, and emphasised that the development problems were solved. He stressed that "In the national interest we must set up a unified modern propeller production programme for Britain". He suggested the two great rivals should get together on propellers, produce an agreed design and set up a jointly-owned company to make it. Before they got up from lunch the broad agreement had been reached. There now only remained the hesitant Bristol Board, but to Fedden's delight they accepted the idea. Fedden picked one of his original Fishponds team, Bill Stammers, to be general manager of the new company, and Stammers coined its name, Rotol, by merging the names of its two parents. Sidgreaves was appointed chairman, Sir Stanley White deputy chairman, and Fedden and Hives were made directors. To get things going, an office and small factory were rented at Llanthony Road, Gloucester, where the design was completed and small-scale production started in the winter of -7. Meanwhile Fedden searched with Haldenby of Rolls-Royce for a permanent site, nearly finding one at Shrewsbury, and finally went with Whitehead and Stammers to see a site midway between Gloucester and Cheltenham. It was perfect, and they straight away pegged out the grass from the plan of the great factory they had prepared. By mid- the Rotol works was taking shape, and production began by the end of that year.
In late William E Prytherch, of the National Physical Laboratory, was invited by Fedden to a meeting at the Air Ministry. He recalls, "I was astonished that such a boyish man should wield so much influence. The gist of the gloomy meeting was Fedden's insistence that the forthcoming British monoplane fighters would be too slow to catch the new Messerschmitt, and said that an extra 12 mph would be needed. He said the Merlin engine gave adequate power, but that the Watts or Jablo fixed-pitch wooden propellers could not translate this power into thrust at maximum speed. He turned to me and asked 'Can you make large forgings in magnesium alloy?' I replied that I saw no reason why this should not be possible.
"On leaving the meeting a hand fell on my shoulder. It belonged to W C Devereux of High Duty Alloys, who astonished me by saying not only that the whole of his organisation was at my disposal but that he would give me £250 if I produced a satisfactory forging. I was not used to doing things for money, and to avoid difficulties I joined HOA. Fedden was unbelievably exacting. Making small test forgings that met his specifications was one thing, but achieving all his figures, in every part of a large forging, tested in every direction, took 18 months of often heartbreaking slogging.
"At last we produced forgings that met Fedden's requirements. The Ministry ordered 27 of them, to be made into three-blade propellers. Three of these propellers were fitted to specially prepared Vickers Wellesley bombers. The advertised objective was to break the world long-distance record, but the real and secret objective was to test the endurance of the magnesium-alloy blades." As described later, the long range flight also tested Pegasus engines in a new cowling, running on 100-octane fuel. The new Rotol propellers performed flawlessly.
Prytherch continues, "Following this, the Ministry ordered HOA magnesium-alloy blades by the thousand. When they were fitted to Spitfires and Hurricanes the maximum speed was increased by 20 to 27 mph, coupled with better take-off and faster diving speeds. I doubt if this would have been achieved in time for the Battle of Britain without Fedden's drive and determination, so in my view he made a big contribution to our victory in that battle."
Rotol Airscrews Ltd had two strings to its bow. The main product was the all-British hydraulic propeller, which at first had blades of magnesium alloy but by was switching to densified wood. The second product was an American propeller of completely different form, the Curtiss Electric. This had been designed as a fully variable answer to the newly developed constant-speed version of the Hamilton, and as it was completely developed and qualified Rotol bought the licence as an insurance. Both propellers went into mass production. After the hydraulic type was continued alone, and it remains in production to this day in much refined forms, together with many other products, in what became Dowty Rotol, and is now Dowty Aerospace.
Sorry about the italics - I can't work out how to make a readable quote box.