The Six-Engined VTOL Design

I was taking a peek at Lockheed Martin big defense contractors’ recent patent filings the other day when I came accross this whopper. A patent for a vertical take-off and landing aircraft with three wings and six tilting engines, notice I didn’t say tiltrotors.

Richard Oliver recently told Aviation Week that a DoD customer was interested in his six-engined Hexplane design (an unmanned version of which is shown above).

Yup, the patent filing, which lists Oliver as the inventor, calls for a six-engined craft that would eliminate the safety concerns associated with world’s only tiltrotor, the twin-engined Bell Boeing V-22 Osprey.

The patent filing claims the Osprey isn’t ideal for high-risk combat scenarios due to the fact that it cannot operate if one of its engines fails (kinda like a conventional chopper):

The current technology twin tilt rotor V22 Osprey’s recent performance is used as the best example of twin tilt rotor problems.

The failure of either propulsion unit to produce thrust, results in the loss of the aircraft and occupants. The cross coupled shaft system provides a marginal performance backup limited to engine failure, not gearbox or rotor failures. The loss of 50% of this aircraft’s power results in its’ inability to continue its’ mission and in many circumstances requires immediate landing. The present invention solves this problem with its’ fundamental design, providing for continued flight following the complete loss of thrust by any propulsion unit, no matter what the cause.

Inability to use evasive maneuvering tactics to avoid hostile fire, similar to that found in high threat landing zones. Quick maneuvering has resulted in the cracking and breaking of rotor root components which may result in the loss of a blade, and therefore the aircraft. The 38 foot rotors are limited to about 10 degree flapping angles. Quick maneuvering can (and has) easily exceed this angle resulting in the failure of a rotor and the potential loss of the aircraft. This limited maneuverability might be acceptable for commercial operations, but not for the intended applications of the military.

The document goes on to point out other shortcomings with the Osprey’s design, including a limited ability to allow troops to fast rope off the back of the aircraft due to the location of the Osprey’s center of gravity and rotor wash as well as the way the tiltrotor reacts to a vortex ring sate (the potentially deadly scenario where choppers and tiltrotors basically run out of air to lift them). In all of these cases, the patent filing says six propeller or jet engines, not rotors, would dramatically improve performance by providing increased stability, backup engines and better maneuverability. Props would be ideal for a medium-size transport while jet engines would be necessary for a faster, larger aircraft.

“While in vertical flight, the six propulsion units are arranged around the aircraft producing thrust. Imagine a round table with six legs,” reads the filing. “Remove one leg and the table remains standing! The center of gravity of this aircraft is generally located about its’ center. The propulsion units are placed such that the remaining thrust following the loss of thrust from one propulsion unit will maintain longitudinal and lateral static stability, therefore supporting the aircraft.”

As Oliver told AvWeek:

it has the unusual ability to survive the complete failure of any propulsion unit and remain statically stable. If you remove any one unit and wing in flight it will still fly safely, even a maximum gross weight and HOGE [hover out of ground effect].” The six engines are completely independent, with none of the cross-shafting you would see in a two- or four-prop tiltrotor.

The Hexplane design is all about survivability, he says, and about being able to continue the mission and not having to return and land after a failure. “I don’t see it as complex. There are not six throttles, just a single go lever and six-channel fly-by-wire,” Oliver says.

Click through the jump to read the patent filing’s detailed description of the design.

The term “Propulsion Unit” as used within this document refers to any method of producing thrust. The example of an engine driven propeller is chosen solely for illustration purposes and is not intended to limit the scope of this invention. The invention is valid for alternate means of propulsion including jet engines. When the propulsion units consist of jet engines this VTOL configuration is known as a “Tilt Jet” since the jets are tilted forward for forward flight and tilted vertically for vertical flight. The invention is valid for alternate propulsion unit tilting implementations. The engine (piston, turbine, rotary, electric or other power source) may be mounted on the wing and transfer power through a gearbox into its tilt-able propeller or rotor. This design allows the engine or motor to remain relatively fixed in a single position without having to operate in multiple positions of the propeller.

[0060] The aircraft configuration consists of a conventional aircraft fuselage, with a nose, with or without pilot and/or co-pilot crew stations in the case of Unmanned Aerial Vehicle (UAV) applications, a central cabin or payload area, and a tapering empennage. The aircraft has three wings, the front wing, middle wing, and the rear wing. Two propulsion units are mounted above, below, or on each of the three wings, yielding six propulsion units. The wings are fixed to the fuselage and the propulsion units rotate in unison to either of two (not including intermediate) positions, vertical or horizontal.

[0061] For electric motor, rotary, piston or turbine driven propeller or rotor embodiments, the propulsion units on opposite sides of the aircraft turn in opposite directions to cancel rotational moments about the yaw axis due to propeller or rotor torque. Small flapped wing panels are fixed outboard of the forward and rearward propulsion units. These wing panels are located within the propulsion units’ propeller slipstream. They provide yaw control during vertical flight. Their flaps are disabled in the neutral position once the propulsion units advance toward the horizontal position.

[0062] The main landing wheels are located at the rear end of the forward propulsion units. A retractable and steerable tail wheel is located on the center line of the fuselage near the rear of the aircraft and retracts rearward and upwards into the normally unused space in the tail cone or alternatively for applications which require rear doors or a ramp the tail wheel may retract forward into the bottom of the fuselage. This eliminates the normally complex and heavy landing gear retraction and extension system increasing payload capacity. When the engines or motors rotate with the propellers or rotors the main wheels are mounted to the aft end of the forward propulsion unit engine support structures. This takes advantage of the existing structural load path which already exists for the engine support. When the engines or motors are mounted in a fixed position with the propellers or rotors tilting, the main wheels may be attached to the aft end of the tilting assembly. The propulsion units are spaced further apart than typical main gear designs increasing ground stability. Gear up landings are not possible with this invention as the landing gear is always down when the aircraft is in vertical flight mode. Separate landing gear controls and systems are not required. Proper placement of the main gear below the nacelle center line and clam shell gear doors can enable partial conventional takeoff and landings (CTOL) to enable additional payload capability when a runway is available. This is accomplished by placing the propulsion units in an intermediate position considering ground clearance is provided for the propeller or rotor tips. With jet propulsion units this would not be a problem.

Click here to read the entire filing.


  • Twidget at large

    How about EMP shielding, what with everybody saying that those weapons are coming or are already here.

    • ben

      Who is saying that?

      Weapons that generate Electro-Magnetic Pulses have been available for 60 years in the form of nuclear bombs, so they are not even remotely new. And the only practical non-nuclear methods for producing an EMP still require huge quantities of conventional explosives. (and have miniscule effective ranges)

      The only “new” weapon concept I can think of that would be even remotely similar would be the electro-laser. Which is essentially a Lightning gun, that guides the electron beam with a laser that Ionizes a channel in the air. And the vast majority of aircraft are already protected against lightning strikes.

  • zardinuk

    An ejection seat wouldn’t be very useful would it…

    • ben

      helicopter ejections seats been around since at least 1995. The rotors are jettisoned along with the canopy.

    • Duke Nukem

      It’s a drone you doof… look at the pic.
      What the hell do you need with an ejection seat.

  • jamesb

    The darn thing looks weird…..

  • Black Owl

    Please tell me the services are not even considering funding that.

  • DougieR

    Haha it slices! It dices! It juliennes! It transforms into the world’s largest weed whacker!

    All kidding aside though this is an interesting concept. I wonder if it could be applied to the C-130 platform? 2 engines on the tail, 2 on the wings, and add 2 more on a forward canard. Add the versatility of a helo to a tried and true platform with proven lift capabilities.

  • Michael

    Is it just me, or is Lockheed making ugly planes nowadays? The F-16 was awesome…comparable to the A-4, and P-51 in sleekness and popularity. The F-35…nice, but the stubby wings are a little distracting. Now this?

  • fromage

    Furthermore – and this is where someone with mechanical or design knowledge of the V-22 should chime in – my understanding was that if an engine quit on the V-22, the vehicle could still function (albeit with a great reduction in performance). Not like boom goes the nacelle, mind you.

  • Alex

    OMG its the Moller skycar all over again ….

  • Copper

    Sorry Lockheed, but this just doesn’t look tacti-cool. That being said further development of this and others like it shall be interesting.

  • Lance

    That has to be the ugliest and worthless idea ever. The props would cut air off from the rear props and would make it slow and unmaneuverable. Stick with the V-22 or a regular helicopter.

  • zman537

    Looks wierd. Looks like alot of technical problems. Think about all the problems that osprey had, now add 4 more engines to it.

  • RCDC

    Probably they are forgetting to adopt to the harrier or F-35 jets jets.

  • mpower6428

    i had no idea how big a turkey the osprey was….

  • So what is it that this guy’s supposed to have invented?

    All he’s done is take an existing idea, and then say that if you stuck three times as many engines on it, it would have increased engine redundancy (and three times the engine maintenance costs).

    Surely the principle of tilt-prop/rotor aircraft isn’t a patentable idea – anyone can design a new one, just like anyone can go and design a new helicopter; and the same goes for the number of engines. I’m confused.

  • JRL

    I could see it being feasible if it was nuclear-powered and could also operate while submerged. And adding the turret and 120mm main gun from M-1 would make it really kickass!

  • TLAM Strike

    Needs Moar Engines!

  • ben, you can’t say that the number of engines is only an indirect cost – they are pretty fundamental to the thing getting off the ground. And it’s not just a bit more time consuming to bolt them on – someone has to pay for design and build; someone has to pay for maintenance, parts and labour, throughout the aircraft’s life. There’s also all the gubbins associated with each engine – alternators, starter/generators, control runs, fuel lines. Then there are all the prop components, controls, etc. And while your thermal efficiency point applies on an engine test-bed, an aircraft engine in airflow creates drag and increases fuel consumption – as will a malfunctioning prop, even if feathered.

    • Mastro

      Agreed Brian

      After all- if engine costs didn’t matter- everything would be multiengine, wouldn’t it?

    • Belesari

      The more complex a system the more people who work on it

      Say each engine requires 10hrs of maintanence time per flight hr. That means that you lose atleast 6 if not 12 people just to doing checks and general maintanence each hour of light time which means YOUR PAYING SOME OF THE MOST EXPENSIVE TROOPS IN THE WORLD to work on a engine.

      Thats just the engines. Its how that airforce has almost as many people as the army and has so few actucally going into combat. And why Super carriers have half their crew as part of the flight crew.

  • mpower6428

    well…. if looking at this picture doesnt nail the coffin shut on a more efficient VTOL aircraft then the plain old “helicopter”….. nothing will

    i have a bad feeling that we’re gonna be abused with these “MONEY PITS” for the next 30 years.

  • mpower6428

    if that “conceptual graphic” doesnt insult your intelligence…? nothing will.

  • zman537

    not really. in order to make this stable, all engines have to spin at the same RPM, same pitch and provide same lift. So if you have all six engines running seperate, that means you have to have a contol system for each motor, thats six computer/controls that need to be sync together to provide equal lift and torque which means thats 6 computer/controls that could fail. Its an interesting design, but i bet this doesnt make it. I do alot RC helicopter stuff, and even though this aircraft is more complex then any RC helicopter i have. the same still applies, the more engines you have that are providing verticle lift the more controls you need to sync together, the more controls and electronics you have the more chance there is of a failure.

  • Tim

    OK… If that thing can lift 200 tons or more, then may be it could be good for something. Otherwise, just the number of engines along, multiply that by multiple squadrons, then it could be a nightmare for the maintenance crew.

    • zman537

      not only that but the fuel consumption. this thing has 4 more engines then the osprey. thats like a 200% increase in fuel usage

  • ospreydriver

    Talk about a solution without a problem. The article seriously mentions FAST-roping as an issue with the Osprey? It’s NOT A PROBLEM. An engine failure as a limitation of the V-22? Unless that monstrosity has 3 sets of interconnecting driveshafts, it’d still be an issue. If it does, that’s a whole lot of complexity and weight.

    It does get redundancy, maybe. That’s at the cost of huge complexity, expense, and maintenance time. Operating efficiency goes WAY down. One big engine is always more efficient than two smaller ones. This magnifies that by a factor of three. A lot of multi-engine platforms are criticized for carrying what are basically “flying spares,” like the EH-101. There’s a reason the B-52 was the last 8-engine bomber, as another example.

    In the end, there’re just more opportunities for this thing to break.

  • Ron Gibson


  • STemplar

    Pretty picture. How much?

  • tiger

    The above design is what you get when you You do Meth & have access to AutoCAD. Even the Nazi’s did not have anything this wacky on the drawing boards.

  • William C.

    I love the aerospace industry taking risks and all of that, but lets stick with the quad tilt-rotor concept instead, okay?

  • oic

    I rather bet on a Sikorsky_S-97_Raider but a transport version. Can fly as fast as the osprey for a helicopter

  • Billy

    OooooooO Big waste of our tax payer money.

  • Tenn Slim

    Multiple engines on sticks. LOL…What a concept.
    The really last great aircraft with LOTS of engines was the old Peacekeeper the B36.
    Now, there was a really great bird. Wing span so long you could do laps on it.
    Multiple props, and jets, 6 turning 4 burning, A maintenance nightmare.
    Flew out of SAC bases around the world, keeping the Atomic Peace for some 10 years.
    A few old geezers will recall that bird.
    Semper FI

  • Thanks so much for the article.

  • silverfoxcole

    when you say the osprey has an “Inability to use evasive maneuvering tactics to avoid hostile fire, similar to that found in high threat landing zones.” how is this six engined design any better