After a number of pilots were lost without means of evacuation during the Korean War, the US Navy wanted a Helicopter that could be dropped behind enemy lines, and be reassembled and flown out by a downed pilot.

It needed to be light, easy to assemble and simple to fly. Gyrodyne, a company experienced in the making of helicopters – albeit with freaky designs – offered the Xron a solution to the Navy’s request.

The XRON was a tiny chopper with counter rotating propellers, designed to be as lightweight and basic as possible. This did mean the pilot lacked any form of wind shielding, and had to sit directly under the spinning rotors.

Contents

• Background
• Development by Gyrodyne
• XRON Design
• Testing
• QH-50 Drone
• Cancellation

Background

After the Second World War, aviation technology experienced significant advancements. Jet propulsion, rocketry, and helicopter development saw considerable investment, leading to breakthroughs in speed, altitude, and VTOL capabilities.

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Helicopters, in particular, had proven their worth during the war for reconnaissance, medevac, and logistics. The technology was still very young, but its potential was absolutely massive, and military planners understood this.

The ability to arrive at an exact location, without the need for runways, was extremely valuable. It could be used to insert special forces operatives, drop off supplies, or perform medevac missions. Before helicopters, none of this could be done as precisely and covertly.

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In the post-war era, military strategists and engineers sought to expand the helicopter’s roles and capabilities, exploring concepts that could leverage their unique operational flexibility.

The Concept of Personal VTOL Aircraft

One such idea was a personal VTOL (Vertical Take-Off and Landing) aircraft. In 1955, the US Navy drew up a requirement for a small helicopter that could be airdropped behind enemy lines to shot-down pilots. The helicopter would arrive in a package and would need to be assembled by the downed pilot.

Once built, he could then fly himself back to friendly territory. The need for such a machine had been identified in the Korean War, where there were many occasions that downed pilots simply couldn’t be extracted.

Of course, if the helicopter was to be assembled by the pilot, likely in less-than-ideal conditions, it would need to be very simple to make this as easy as possible.

Outside of this specialised role though, the idea of a personal VTOL (Vertical Take-Off and Landing) aircraft was revolutionary. It could also be used for reconnaissance, provide new means of commando deployment, and enhance individual soldier mobility.

This concept was attractive for several reasons, including the potential to bypass traditional logistical challenges associated with troop movements and the ability to insert or extract personnel in locations inaccessible to conventional aircraft.

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One company, Gyrodyne, was in a perfect position to tackle such a job.

Development by Gyrodyne

Gyrodyne Company of America, which had experience in helicopter design and manufacturing, was awarded the contract to develop the Rotorcycle under the guidance of the Office of Naval Research and the U.S. Marine Corps.

Gyrodyne had been at the forefront of helicopter design since the latter half of the 1940s, and conveniently had already been working on very small VTOL machines. One of these was the Model 2C, which had counter-rotating main rotors and no tail-rotor.

The counter-rotating propellers cancelled out the rotational torque (twisting force) of a single rotor, which usually require a tail rotor to counter this torque. But tail rotors also provides a means of steering, so steering cannot be achieved by two rotors alone.

Gyrodyne’s approach to solving this was with drag brakes installed on the tips of each rotor. Simply put, zero activation of the drag brakes means the torque of both rotors perfectly cancel each other out, thus it remains horizontally stable (it doesn’t steer left or right).

When the drag brakes of one rotor are activated, the perfect balance of torque is interrupted, and the helicopter will begin to turn in the opposite direction of the unbraked rotor. This served as a steering system. In Gyrodyne’s design, this was achieved by simply depressing either a left or right foot peddle.

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This system allowed for a very compact, lightweight design, perfect for a personal VTOL extraction aircraft. The Navy awarded Gyrodyne with a contract to produce such a machine, which was named the XRON Rotorcycle.

Gyrodyne’s approach to the design was focused on simplicity, portability, and ease of use. The resulting XRON Rotorcycle was innovative in its use of a counter-rotating rotor system, which eliminated the need for a tail rotor and simplified control for inexperienced pilots.

By the end of November 1955, the first flight of the XRON took place. However the engine, a 40 hp two-stroke, was quickly found to be underpowered and was overheating during tests. A 55 hp Porsche boxer engine was acquired for testing, along with a Solar turbine engine.

After further testing, the turbine and Porsche engine were found to be the most suitable, so a more powerful Porsche engine was added, and testing continued.

XRON Design

The Gyrodyne XRON Rotorcycle featured several innovative design choices to meet its unique requirements. It was powered by a Porsche flat-four engine, chosen for its reliability and power-to-weight ratio, driving a co-axial rotor system that eliminated the need for a tail rotor.

With the 55 hp engine the rotors were 17 ft in diameter, and the craft weighed a total of 617 lbs. With the more powerful 72 hp Porsche engine a new transmission had to be added along with 20 ft rotors to accommodate the extra power and weight. This version weighed 900 lbs (400 kg).

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This use of counter-rotating propellers and tip-braking significantly simplified the aircraft’s control mechanisms, making it more accessible to personnel who were not specialised in piloting helicopters. Remember, its original purpose was to be dropped to a downed pilot and flown out.

The pilot may be injured, or located in an area that is not ideal for constructing and taking off in a small helicopter, so it needed to be simple.

The Rotorcycle was designed to be air-dropped or carried by vehicles and could be assembled in the field very quickly without special tools. Its compact dimensions and the ability to fold into a small package for transport were crucial features that enhanced its operational versatility.

In addition, the elimination of a long boom perfectly suited the XRON to naval operations aboard destroyers and carriers, within which space is a valuable commodity. It also made for a much more efficient machine, as there was no parasitic rear rotor, and as such all power was dedicated to lifting.

Despite its small size and relatively simple design, the Rotorcycle was capable of reaching speeds up to 80 miles per hour and had a service ceiling of over 10,000 feet. It could carry a payload of approximately 120 pounds, allowing for the transport of light equipment or supplies in addition to the pilot.

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It was constructed from beams, and at the rear a simple inverted “V”-shaped tailplane helped with stability while travelling forward at high speeds.

Testing

Testing of the XRON with its different engines took place through the latter-half of the 1950s. The Marine Corps were initially impressed with the aircraft, ordering five so they could conduct their own evaluations.

However the USMC declared that the XRON was too difficult to operate, and lost interest in the project. Meanwhile, the Navy began investigating the idea of a using a drone to deliver anti-ship and submarine weapons from long distances.

The aircraft may be lost on this mission and so would be considered semi-disposable. A pilotless version of the XRON looked like the perfect answer to this. Suddenly, Gyrodyne’s mission changed, and in 1958 the Navy awarded them another contract to modify the XRON into a pilotless drone named the QH-50.

They still wanted to make the XRON work though, so they continued to test and develop that machine at the same time. They showed it off at various international events, and even won the grand prize for the most manoeuvrable helicopter at the International Paris Air Show in 1961.

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However by 1964 the company was too busy with the QH-50, and thus work on the XRON came to a stop. The XRON proved itself to be a very reliable machine, suffering no crashes or deaths across all of its years of flying.

QH-50 Drone

The development of the QH-50 DASH was driven by the U.S. Navy’s need to enhance the anti-submarine warfare (ASW) capabilities of its destroyer fleet in response to the growing threat posed by Soviet submarines during the Cold War. Naturally, faced with such a threat, the US Navy wished to obtain a weapon system that could keep Soviet submarines far away from their own assets at sea.

Traditional ASW methods were limited by the range of shipboard sensors and weapons, prompting the Navy to explore new technologies that could project power beyond the immediate vicinity of its surface vessels.

Using the XRON as its basis, Gyrodyne created a revolutionary pilotless drone that set a number of world firsts in the field of aviation. The QH-50A came first. It was very similar to the XRON, and served to prove the concept of a pilotless drone and the capability of carrying a torpedo.

The first flights were manned, but on August 12, 1960 the QH-50A became the world’s first helicopter drone to fly. A few months later in December, it then achieved the world’s first unmanned landing on a ship.

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The next model, the QH-50B, was cancelled in favor of the QH-50C, which was powered by a Boeing turbine engine and could carry two torpedoes. The 255 hp turbine engine required a major rework of the design, resulting in a clear deviation from the XRON from this model onwards.

Delays

Due to its expanded capabilities, the C model would enter production, although it was set back by considerable delays. The US Navy modified a number of its outdated destroyers to operate the QH-50, saving them from the scrapyards. This large effort was actually finished early, creating a large gap where they were waiting for the drones to arrive.

As a result of the desperation to solve this embarrassing situation, Gyrodyne’s production began slipping and problems started arising. The main issue stemmed from a faulty government-supplied altimeter, which was causing the automatic flight control system to fail.

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Gyrodyne grounded the aircraft and created their own fix for the problem, which they completed in mid-1963. Production resumed, and Navy destroyers began receiving QH-50s.

More models followed, including the QH-50D and the QH-50E, which provided improvements in powerplants, guidance and flight controls. Over 750 examples of these aircraft were built throughout the 1960s.

The drones were controlled from the ship via a radio link, with operators using onboard equipment to guide the drone to the target area, release its torpedoes, and then return to the ship for recovery. They could be flown up to 22 miles away from their host ship before releasing their torpedoes.

This massively increased the effective danger zone around US vessels for any approaching submarine, and limited the time they had to respond to a torpedo launch.

Cancellation

By the end of the 1960s the QH-50 program was cancelled. This was mostly down to the Vietnam War absorbing significant quantities of the US’ defense budget, and the lack of submarine threats in that war.

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Despite this the drones continued in use in small numbers, and some were even fitted with cameras to help with navigation. Over their career in the Navy they earned a very poor reliability record, however this is attributed to improper maintenance as a result of the aforementioned budget cuts (Japan’s navy, who also operated the drones, had much lower failure rates).

Even when failures did occur, they were almost always related to the guidance system, rather than the airframe itself. The drones did see some combat, but not in their original role. They flew reconnaissance and spotting missions over Vietnam, where they were equipped with cameras and guided in naval artillery fire. In this role, they flew in zones that would be essentially impossible for manned aircraft to survive.

Incredibly, the QH-50 remained in use with the US Army until 2006! They were primarily used as target tugs. Their retirement marked the end of a very long career for not only the QH-50, but also the original XRON that it was developed from.

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Today, Gyrodyne is no longer in the business of designing and manufacturing helicopters. These portions of the company were sold off in the 1970s, and today it is a real estate investment firm.

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