Mind Your Step; The de Lackner HZ-1 Aerocycle

September 8, 2022

The idea of using some form of aerial conveyance to transport soldiers has a surprisingly long history. In the early 1800s, Napoleon himself apparently gave serious thought to creating some form of airborne corps for his proposed invasion of the United Kingdom, even going as far as to appointing experts to examine the idea, which was to have balloons carry soldier across the channel.

Needless to say, the concept was scrapped as impractical.

But the idea of airborne troops persisted and was eventually realised in action and on mass scale some 140 years or so after Napoleon’s musings. Paratrooper assaults became an important feature in the Second World War, though the results they achieved were highly variable, from hugely successful to awful failures.

But the utility of air mobility for armies was firmly established in the minds of militaries around the world by the end of the war. The helicopter was recognised as the means to achieve this, and development of this type of aircraft has effectively revolutionised how troops can deploy. But even as the helicopter was establishing itself in the 1940 and ‘50s there were those who thought perhaps more could be achieved.

They theorised that if the helicopter was to effectively become the airborne equivalent of the truck, then maybe there was a role for an airborne conveyance for the individual soldier, an airborne version of the motorcycle.

Meet the de Lackner HZ-1 Aerocycle.

The origins of this one-man vertical take-off and landing device go back to work done by Charley Zimmerman, an aeronautic engineer who worked for NACA. Zimmerman was thoroughly put out by how complicated and dangerous aircraft actually were to fly and wanted to basically make personal flying an everyday thing.

After conducting design work which led to things like the Vought XF5U – AKA the “Flying Flapjack” – Zimmerman came up with the math and basic design on how to essentially make a thrust vector propulsion system work with someone standing on it. Control could be achieved by the operator shifting his weight around to control movement in any direction.

This work was all conducted in the 1940s and Zimmerman actually created a prototype at his home on his own time to test his idea in 1946 – the first “Aerocycle” as he christened it.

The novel idea attracted attention from helicopter maker Hiller, who borrowed the aerocycle for testing in 1947/48. They didn’t think much could be made of it and returned it.

But Zimmerman continued with his experiments at NACA, principally with a hover board that used compressed air for propulsion, and by 1953 he had proven the concept well enough that the US Navy took an interest. And that in turn led to the US Army noticing.

Bear in mind, the Korean War was just about finished at this point and this had shown that rather than the wars of the future being fought with nuclear weapons, as had been theorised post World War Two, in fact conventional land forces still had a major role to play.

Korea had also demonstrated the sheer utility of the helicopter and vertical flight.

So, the US Army now had a very deep interest in any concept regarding tactical troop movement by air and the money to invest in new ideas and technology. And they thought that a one-man airborne transport might be perfect for reconnaissance troops.

Zimmerman, the true innovator that he was, happily gave up his patents on the aerocycle to encourage development of the concept, which led to two different machines being built.

The first was the Hiller VZ-1 Pawnee, which employed a ducted fan for lift.

The other was the invention of Lewis McCarty Jnr., another aeronautical engineer who had heard of the testing of Zimmerman’s jet board and thought it all a great idea. Working with the de Lackner Helicopter company McCarty’s vehicle was initially designated as the DH-4 Helivector.

 

This consisted of a frame that supported the engine; a Mercury Marine outboard motor that produced 40hp. This drove a pair of counter rotating propellers which had a diameter of 15ft (4.6m) and control was via a motorcycle style twist throttle for power and the pilot using his weight to direct the machine.

The landing gear on the first examples was comprised of an arrangement of airbags on the ends of spars, with a larger central float under the pilot. This allowed the HZ-1 to act as an amphibian, able to land and take off on both land and water, though I suspect you wouldn’t want to try the latter except on the smoothest of ponds.

Maybe this was recognised as not particularly useful as later examples employed a more conventional skid undercarriage.

Because the US Army were indeed interested enough in the aircraft to order twelve production examples for testing. These were originally designated as the YHO-2, which translates from “armyese” into “Prototype-Helicopter-Observation. But the unique nature of the aircraft led to the US Army issuing a unique designation – HZ-1, with the name “Aerocycle” also being reapplied.

In addition to the crewman, the Aerocycle was expected to be able to carry 120lbs (54kg) of cargo or else be fitted with an auxiliary five US gallon (19 litres) fuel tank. This would have boosted range from 15miles (24km) to 50 (80km).

The HZ-1 was also reportedly capable of a maximum speed of 75mph (121km/h) and of reaching a theoretical ceiling of 5,000ft (1,500m), though no one ever tried to achieve that. Instead, the Army’s testing was concentrated on examining how simple the Aerocycle was to operate. De Lackner apparently claimed that a person could learn to operate the vehicle in just twenty minutes, like riding a bike.

Of course, the thing about learning to ride a bike is that you quite often fall off…something that really doesn’t bear any contemplation when it comes have two threshing blades underneath you.

The HZ-1 did have a safety harness to stop that from happening, but as the whole thing worked by the pilot moving his weight to change the centre of gravity, one suspects that should they ever need to rely on the harness, things were going spectacularly wrong for them.

The first tethered flights were conducted by the Army in November 1954, and the results did seem promising, leading to the order for the twelve production aircraft. As said, their ideas were that the Aerocycle would provide infantry with a rapid reconnaissance vehicle for scouting and communication duties.

 

In 1956 a proper test program was implemented, being conducted at Fort Eustis in Virginia and being run by Captain Selmer Sundby, a pilot with over 1,500 hours of flying experience, much of it on helicopters. And he was very much of the opinion that the assertion that the HZ-1 could be flown with just twenty minutes of training was not true.

As he put it:

“. . it only took me one flight to realize that a non-flyer would have considerable difficulty operating it.”

Sundby also noted that the low-slung blades had the nasty tendency to kick up large amounts of dust and stones, hardly ideal for safe operation.

Plus the testing showed a rather alarming issue. With a total of 43 minutes of flight time, two of the HZ-1’s crashed, the result of the counterrotating blades intermeshing.

Fortunately, Capt. Sundby was unhurt in either event, even though one occurred at a height of forty feet, but the losses and close calls spelt the end of the HZ-1. The project was abandoned, Sundby was awarded a Distinguished Flying Cross for his efforts (which I would say proves how dangerous the brass thought the testing was) and the HZ-1s were scrapped, except for a final example that is retained at the U.S. Army Transportation Museum at Fort Eustis, Virginia.

Now, if you’ve read my previous article on the SPAD SA, you’ll know I have grave reservations about crew being placed right next to an active propeller. And with the HZ-1 my sense of Health and Safety is going into overdrive.

I mean they basically were aspiring to placing a soldier with twenty minutes of training over what looks to be a giant flying food blender…and then sending him into a combat zone…where he would be shot at.

To render a personal opinion, that sounds utterly insane and a great way to cover the field in a lot of unidentifiable goo.

However, though the HZ-1 may not have been the right machine, I have to give kudos to McCarty and to Zimmerman for trying and for their forward thinking. Because I suspect their ideas on the basic concept, giving the individual soldier the ability to fly, is something that will prove of real value when it is achieved in the future.

Considering that work has essentially been ongoing on the idea of flying troops ever since, with the current incarnation being the efforts of companies like Gravity Industries, it seems likely that at some point equipping personnel with a personal flying capability will become a reality.

Sources/Related:

https://en.wikipedia.org/wiki/De_Lackner_HZ-1_Aerocycle

http://www.howtoadvice.com/Sky-High

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