Darpa Takes Another Shot at High-Speed VTOL

Undeterred by past failures, the U.S. Defense Advanced Research Projects Agency (Darpa) is launching another attempt to develop a high-speed vertical-takeoff-and-landing (VTOL) aircraft with the hover capability of a helicopter.

The VTOL X-Plane program is a 52-month, $130 million effort to fly an experimental aircraft capable of exceeding 300 kt., but with a hover efficiency of 75% or better and a cruise lift-to-drag ratio of 10 or more. By comparison, according to Darpa, today’s conventional helicopters are capable of 150-170 kt., with a hover efficiency of 60% and a cruise L/D of 4-5.

High-speed compound helicopters such as Sikorsky’s X2 are capable of 240-260 kt., while the Bell Boeing V-22 tiltrotor can exceed 275 kt., but with low hover efficiency.

“We have a simple objective: to fly much faster, with improved efficiency in hover and forward flight, without sacrificing the ability to do useful work,” says Ashish Bagai, Darpa program manager and former Sikorsky principal engineer.

Useful work is defined as the difference between empty weight and maximum gross weight, he says. The program is targeting a useful load of at least 40% of gross weight, which is expected to be 10,000-12,000 lb. for the X-plane demonstrator.

This compares with a useful load of 35-40% of gross weight for a state-of-the-art helicopter, according to Darpa.

Bagai says Darpa is looking for “elegant” designs combining the attributes of fixed- and rotary-wing aircraft, that are “not overly complex and not brute-force approaches,” he says. A broad agency announcement has been released, and Darpa is hoping to attract proposals from nontraditional companies and “exotic ideas from smaller companies on technologies, agile teaming and rapid design,” he says.

This is not the agency’s first attempt to develop a high-speed VTOL aircraft. The canard rotor/wing Boeing X-50A Dragonfly was designed to demonstrate a circulation-control rotor that could be stopped in flight to act as a fixed wing. Both subscale unmanned demonstrators crashed before transition could be achieved and the program was terminated in 2006.

The Groen Heliplane was a high-speed gyroplane design with a rotor that was powered by tipjets for vertical takeoff and landing and autorotated in forward flight at speeds up to 350 kt. The program encountered technical challenges with noise from the tipjets and was terminated in 2008.

— This article first appeared in Aerospace Daily & Defense Report.

  • d. kellogg

    Granted Hollywood is the last place to look for scientific accuracy in its ideas,
    but I’d be curious just how close we could get in developing some kind of vertol similar to the “Whispercraft” helicopter like in The Sixth Day,
    or the twin-fan (but each using contra-rotating encased/shrouded rotors) gunship like in Avatar.

    There were, years past, numerous X-craft designs that investigated various VTOL/STOVL configurations, perhaps some of them need dusted off and tried again with modern technologies (we’ve come a long way from the ancestors of the V-22 into what it has become despite all its development troubles.

    Thrust vectoring engines, ducted fans, entire tilting engine pods, “fan-in-wing” concepts….there are sufficient ideas out there with a lot of potential.

    • Jay

      Why not the VTOL aircraft from the Avengers? two rotors in either wing and two jets on the back?

    • eDoggie

      Something similar to the Whispercraft from The Sixth Day was tried.

      • FormerDirtDart

        “Neither aircraft was able to achieve transition to full forward flight mode during the portions of the test flight program that were completed. In September, 2006, DARPA recognized the inherent design flaws and withdrew funding for the program.”

  • LtKitty

    Helicarrier?! *sigh* At the very least I can only dream…

    Seriously, though, this is a worthwhile endevour. I’m curious as to what design DARPA will build.

  • Musson

    Burt Rutan designed and built aircraft that would meet most of these milestones – decades ago. But – he was too offbeat for the military establishment.

    Rutan’s low cost COIN aircraft were even more amazing.

    • d. kellogg

      Scaled Composites-type aerospace entrepeneurs is what this nation needs more of.
      The ATTT transport concept, if enlarged to a C-130 sized fuselage, could’ve shuttled almost 50% more payload, and at much shorter take off and landing rolls with that unique double wing planform (or as-sized would’ve made a quite suitable C-2 COD replacement if “carrier-ized”).
      The ARES COIN jet will sadly only ever be remembered as the Me 263 from whichever Iron Eagle movie, but certainly had many ideal characteristics that COIN aircraft demand. It was born in a day and age when BAe had ideas like the SABA Small Agile Battlefield Aircraft, platforms which today would have great utility alongside UAS/drones.
      Few people over the years have filled me with that kid-in-a-candy-store elation as when I had the priviledge of meeting some of the Scaled folks seems like ages ago and glimpsed so many of their “napkin ideas” that unfortunately never made it beyond paper.
      These are the types of people we need developing each new generation of aircraft, not corporate committees like the big defense contractors whose priority is shareholders’ return first and churning out disappointing products that consistently need requirements lowered to meet them.

    • FormerDirtDart

      Exactly when did Burt Rutan design a VTOL aircraft? I have never heard of any. As “develop a high-speed vertical-takeoff-and-landing (VTOL) aircraft with the hover capability of a helicopter” is the primary milestone of the DARPA project this article discusses, I fail to see how any of Burt Rutan’s designs are even remotely relevant.

  • The Old Bear

    May I suggest that you have a good look at the OV-10X Super Bronco and look at it’s Operationial Roles, Sensors and Smart Weapon capabilities and then think of a modern V/STOL aircraft to replace it, the Apache, the AH-1V Venom as well as the Blackhawk and the Huey as well as the Harrier and the F-35 Bunter.
    Think outside the Box

  • jmhsutpe
  • jmhsutpe

    300Knt is not 300Kt, I think.

    • blight_

      And aren’t Newtons usually abbreviated as N? kt here is knots.

      • jmhsutpe
  • Sikorskys’s Raider.

  • Max

    Did I miss something or did they retire those floating black triangles that have been so numerous in the vicinity of Air Force bases? I think this news article is a joke


    Well, lets hope whatever they come up with is good. Worst come worse, DARPA maybe hit with “lets get rid of this program to save money” wave, and everything goes horribly wrong. Really though, a high-speed VTOL aircraft is something the US service needs. If there is ever another raid similar to the Abottobad Raid, this new DARPA machine will do it. I personally think several lift fans house in a wing, coupled with two engines embedded in low drag wings could cut it.

  • Jon

    Okay I think this is a great idea but in light of the coming sequestration and the fact that the Pentagon is whining that they cant even afford to deploy the Truman to the Persian Gulf is this really what we need to be spending our money on? I dont doubt the civil and military value of such a machine but in terms of priorities is this something we really need to be doing now? Would the advantages of such a craft really be so great compared to conventional choppers and tilt rotors that we absolutely have to have it NOW?

  • Thomas L. Nielsen

    Don’t get me wrong – I’m very much in favour of new developments in aerospace, and I agree that a high-speed VTOL aircraft with good hover efficiency is a great idea, but still….

    These new DARPA high-speed VTOL aircraft must “fly much faster, with improved efficiency in hover and forward flight, without sacrificing the ability to do useful work” and at the same time be an ” “elegant” designs combining the attributes of fixed– and rotary-wing aircraft, that are “not overly complex and not brute-force approaches,” “?

    For some reason this sets off my reality-disconnect klaxons.

    Regards & all,

    Thomas L. Nielsen

    • blight_

      At least Lockheed wasn’t awarded a cost-plus contract to deliver it…

  • Phono

    Keeping in mind the technology developed specifically for the Fan behind the cockpit of an F-35 – this is an interesting long-shot. We’ll see in a few years.

    • The Old Bear

      Shudder, please don’t remind me. The whole problem with the design is that blasted overcomplicated and badly designed V/STOL system.

      • blight_

        If the -B drops dead the -A and -C still have their own problems/technical hurdles. I think we blame the LiftSystem a little too much…

      • gaylord_gaylordson

        According to popular belief at least. According to conventional wisdom the F35 is doomed.

        Conventional wisdom, that is the thoughts of the crowd, are fortunately almost always wrong when it comes to technology.

  • blight_

    Perhaps Rolls Royce should talk to Boeing about doing a STOVL, but using their LiftSystem instead of thrust-vectoring like the RR Pegasus. But I think the LiftSystem was designed in partnership with Lockheed, so..

  • Miles Garnett

    On February 25, 2013 DARPA posted a desire for information on VTOL. I had been working on that for a long time for the civilian market and had already developed a successful model prototype in the form of a drone. It is more advanced than then any in the world including the U.S. Harrier, Osprey and the STOL F-35. It is simplicity at its best. The only problem I have is that I do not have the infrastructure organization to manufacture the full size version or an understanding of the paperwork to file, although having run a conglomerate I know how to set it up. The answer is due by the beginning of May 2013
    Simplicity with six point support is what I call it. One motor can handle four (4) points in a combination of two without vectoring. (up, down, forward & backward). The other two points are handled by the fixed ducted fans in the wings.

    Six points is the optimal requirement for a perfect VTOL. the plane and the tilting device design can both support jet engines for speeds in excess of 500 mph. I have an executive summary.