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Flexrotor vertical take-off and landing UAV enters second phase of development


May 2, 2012

The Flexrotor takes off vertically from its launch platform

The Flexrotor takes off vertically from its launch platform

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In an attempt to combine the vertical take-off and landing (VTOL) capabilities of a helicopter, with the speed, range and altitude capabilities of a fixed wing aircraft, tiltrotor aircraft, such as the AgustaWestland AW609 and the Bell Boeing V-22 Osprey rely on powered rotors mounted on rotating shafts or nacelles at the end of a fixed wing. But the tiltrotor design isn’t the only option for aircraft looking to get the best of both worlds. Like Aerovironment’s SkyTote, the Flexrotor is designed to transition from vertical to horizontal flight without any pivoting of its rotor.

Having been awarded a contract earlier this week by the Office of Naval Research (ONR), Aerovel Corporation will enter the next development phase for the Flexrotor, which is intended to deliver improved maritime surveillance capabilities. With the requirement that it launch from a ship, the unmanned aerial vehicle (UAV) has a wingspan of 3 m (9.84 ft) and an oversized rotor with a diameter of 1.85 m (6.07 ft).

The size of the propeller is designed to strike a balance between providing enough lift to enable the aircraft to take off vertically, while also being small enough to be efficient during horizontal flight.

Currently powered by a single-cylinder 28 cc two-stroke engine through a reduction gearbox, the Flexrotor takes off vertically like a helicopter from a portable fold-out rig that supports the wings. Once airborne, the tail is deployed and, once it reaches a high enough altitude, it transitions into horizontal flight by pitching over into a dive before leveling out. To transition back to vertical flight, the aircraft flies at about 70 knots (80 mph/130 km/h) before pulling up and entering a hover that allows it to descend vertically and land.

The aircraft completed its first successful transition from vertical to horizontal flight and back again in August 2011, which can be seen in the video below. This and subsequent test flights have been conducted in light winds, but Aerovel plans to gradually increase the aircraft’s operating envelope and expose it to windier conditions. The development of an upgraded propulsion system to allow the aircraft to cope with crosswinds and high winds will be the focus of the next development phase.

Aerovel is also creating an Automatic Servicing Platform from which the Flexrotor could launch, land, park and refuel with no human assistance. In addition to placement on a ship, the platform could also be used to remotely site the aircraft for launch.

“[The special ops personnel] like the idea of not exposing where they are when they need to launch and recover one,” said John Kinzer, ONR program officer for Air Vehicle Technology. “They could put it on a mountaintop somewhere and just leave it to do surveillance.”

At its maximum vertical take off weight of 19.2 kg (42.3 lb), the Flexrotor can climb at a rate of 1 m/s (197 ft/min). After making the transition to horizontal flight, the aircraft boasts a maximum level speed of 78 knots (90 mph/145 km/h) and can stay in the air for more than 40 hours to reach a maximum range of more than 3,000 km (1,865 miles).

Here's the video of the Flexrotor making its first successful transition from vertical to horizontal flight.

Source: ONR, Aerovel

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

Interesting, but the name is misleading.

Guy Macher

http://en.wikipedia.org/wiki/X-13_Vertijet I think this falls under the 'nothing new under the sun'. I remember something similar that was done many years ago. http://en.wikipedia.org/wiki/VTOL Here is one that is very similar but with counter-rotating propellers. http://upload.wikimedia.org/wikipedia/commons/thumb/3/31/Lockheed_XFV-1_on_ground_bw.jpg/220px-Lockheed_XFV-1_on_ground_bw.jpg


We seem to have the technology today to be able to develop and copy the way our feather friends do, which is a control stall when they come in to land. Why not go in that direction, as it will use less fuel.



The new part is the computer flying it and the landing station which isn't a bad idea although it is the only place this thing can land so what is the advantage of this? But saying it could land in gusty conditions with those wings on it is just a dream.

The Hoff

3000K in 40 hours...... NON stop?

Mr Stiffy

You guys are amazing both the Pogo and the Vertijet were total failures.

Also this little craft flies a completely different mission being small and not having an on board pilot.

I remember back in the days of the Pogo and the Vertijet one of the most common comments about either craft was that the vertical tail first landing was "terrifying"....quite a comment coming from hardened test pilots.

It seems to me that no matter what Gizmag puts up here there are a bunch of people that range in knowledge from zero to "too smart for you guys" that just want to tear the article apart. If Gizmag is so awful why do you continue to watch it? Is it so you can show us how smart you aren't?

Not bad. They should have used 2 6' props with electric motors both lift more and better high speed profile. By doubling the prop swept area you get almost 2x's the lift/hp. Plus in crosswinds the props counter rotating to each other makes it a lot more managable as much of the torques, wind loads of crosswinds cancel out. Another is props on the wingtips cut wing endplate drag if the prop comes up on the outside where the prop conteracts the tip vortex. I found this out designing a WIGE and a seaplane I hope to build soon. jerryd

Here is something to weigh: Which is easier - to get under a 100 pound set of barbells and push up - or to put it on the floor and roll it? The amount of energy wasted on vertical lift is not worth the waste.


Is this going to be passenger carrying ? It would be terrifying with that push-over into straight and level, as well as the zoom to vertical for landing ...


Yes vblancer, that's the type of forum Gizmag runs here. It's pretty much a free for all for the common man.

The Hoff

@spacewalker, think drone, think surveillance, no people on board dude, did you read the article?

Bill Bennett

It would be more efficient if its propeller blades were shorter but greater in number. You could use three two bladed propellers mounted one in front of the other. The trick is getting all six blades to cut through clean air but it is possible.

re; donwine

Horizontal takeoffs and landings take space not available on most ships. Therefore maximum efficiency in operation is not the same thing as maximum aerodynamic efficiency.

In other words it is NOT WASTE to be able to launch and recover vertically.


Slow-for-sure Helicopters have the highest fuel consumption of any aircraft for its weight. The solution to aircraft carriers is to go amphibious with a elevating loading ramp. The Osprey proved it can be done, at the sacrifice of payload capability, high fuel cost and more than a few have died in them.


vblancer- You attack what other's post with only part-correct "judgement" calls!

The two Convair protypes were not, as you call it, "total failures" and indeed the later Vertijet went part-way towards addressing pilot concerns. Helicopters 'back down' (or bottom down) for a landing and its mainly how the pilot's seat is positioned (plus final height above ground) that are the major factors.

A pilot's seat (or cabin module) that turns through 90 degrees is part of the answer, and the other is siting it towards the aircraft's tail (as it is in a Gee Bee Zee racer).

The landing gear (including the Vertijet's Hook-on Tower) solutions were not well developed, but this issue is not impossible. Indeed, I "created" a range of VTOL aircraft for a Screenplay (set in the 1970s) , and my own 'Pogofighter' solved all the issues through afore-mentioned pilot pod, and could even taxi about like a conventional aircraft. It even had a built-in pilot elevator for comfortable entry & egress.


re; dumbwine

Given the loss of airframe rate the US Navy experienced when using flying boats and amphibious aircraft in open sea conditions as artillery spotters it is cheaper to pay for the gas for vertical flight aircraft than to replace the destroyed airplanes. This does not include the human cost of lives lost both from crashing of maned aircraft and accidents in recovering the aircraft from the sea.

The news reports about the V-22 Osprey crashes for the most part have been blatantly libelous.


Slowdown! You would have to agree that all these problems would disappear if governments actually quit fighting wars. If all the inventions of war implements could bring peace - then we should have had peace a long time ago. There are no perfect airplanes for destroying one another. Just think how much better mankind would have been if all the money ever spent on armaments world wide had been diverted to helping one another.


re; dumbwine

The military of the USofA is the Largest disaster relief agency in the world.

"It takes two people to make peace, but only one to make war." Louis L'Amour


A single propellor makes sense for balance during takeoff and landing. But neither the article nor the video discuss the two small props at wing ends. I assume they are used for extra stability during landing.

Bruce H. Anderson
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