VSTOL Aircraft - Arbalest 0.2

Visualization - Albalest VSTOL Plane - Gray Camo

Summary:

The Arbalest is a Design Proposal for a small multi-role Low to "Zero Roll" Take-Off and Landing Aircraft.  Both conventional Airplanes and Rotorcraft have distinct limitations in their flight envelops.  Rotorcraft while possessing vertical take off and landing have limits on their top speed, range and flight ceiling.  Conventional Aircraft have long range and high cruise speeds but need rather long runways.

Range and Speed of Various Airframe Typologies  Compared

Back Ground:

There is a lot of discussion about CAS these days as the discussion around the A-10's retirement heats up.  In this article over at Alfa Foxtrot (link) Tyler Rogoway points out how the OV-10 Bronco never reached its full potential.  He goes on to point out how the west is spending large sums of money to provide Combat Air Support.

"If there were ever the perfect use for the metaphor "killing an ant with a gold-plated sledgehammer," the Pentagon's never ending use of fast fighter jets and strategic bombers to fight guys with AK-47s and old Toyota pickup trucks would be it."

This is not an exaggeration at all.  In the Economist's article "Airpower on the Cheap" (link) expounds on this problem.  A Small Turbo Prop can run for as little as $500 per hour.  This contrasts to a fighter plane that cost more in the order of $40,000 per hour.  Specialized aircraft such as the CV-22 Osprey are even more expensive to run.  Helicopters further have the difficulty of rather low speeds and short range due to drag and rotary lift.  (See: Table Below)

Table of Aircraft Cost, Speed, Range and Capacity

Clearly there is a disconnect between the Schema of our "View of Threat" and the tools to deal with the given threat.  There are a few projects to address this from smaller manufactures.  The ARHLAC (link) is being developed in South Africa and Scorpion (link) in the United States.  These apply new technologies and design methologies to the existing paradigm.  These efforts should be applauded, they are moving the discussion forward.  A brief video discussion of these issues can be seen at Air & Space Magazine in an interview with K. P. Rice and William E. Beckett (Link).  The full length film about the OV-10 can be seen here. (Link)

VTOL / STOL Diagram:  Landing Distance Left, Take Off Right, Operating Ceiling vertical

Design:

The solution to the problem has already been in part identified.  A hybrid between a plane and a rotorcraft.   This is what the Osprey attempts to be but manages to be so complex that it is even more expensive to fly than an F-22 (ca. $80,000 per hour).  The need for a high lift body and low drag dictates the use of a very low aspect ratio wing design.  A design of a lifting body plane would allow VTOL/STOL and a high top speed.  The best of both worlds, and a very expensive compromise.  Sometimes we can learn something by looking back at paths not taken.

Original Design Sketch - Proved to be slightly too large for landing on narrow roads.

The plane pictured in these images is derivative of the Vought XF5U "Flying Flapjack" (Link).  The Vought XF5U was a plane developed for the Navy during WW2. It never flew as research/purchasing moved toward jet propulsion.  It's predicted performance was remarkable a top speed of 550 mph (885 km/h), a range of 1064 miles (1703km), not to mention, sharp maneuverability due to it's compact dimensions.  The test plane that was developed prior to the Vought XF5U, the Vought V-173 could perform a "Zero roll Take-Off" due to the high lift of the Wing/Body.  That is, it started to leave the ground as soon as it was rolling.  Likewise, landing distances were very short due to the low stall speed of the high lift wing/lifting body.

Vought XF5U - From Wikipedia (Link)

The Vought XF5U designed by Charles H. Zimmerman of the Chance Vought Aircraft Company.  Mr. Zimmerman worked extensively to bring VTOL to fixed wing Aircraft.  He is the author of numerous patents such as  this system for Vertical Take-Off (Link)  Mr. Zimmerman designed numerous VTOL aircraft including the precursor to the Osprey the LTV XC 142 (Link).  The Voight XF5U was pushing the technology of the day pretty hard.  The props were made of wood and the engines use a complex drive system more akin to a helicopter.  Today this concept could be much improved with modern construction materials, such as composites, and computer assisted analysis of aerodynamics.

Visualization - Search and Rescue & High Speed Air Ambulance

This solution is a compromise.  The high aspect wing and large props are far from a perfect solution for a VTOL Plane. The lifting body and oddly placed props impose restrictions on the safety and comfort of such a plane.  The large props could be dangerous and the cargo entrance at the back of the craft a bit breezy if the props were engaged.  Not to mention getting in and out of a plane that sits at a steep angle could prove challenging.  One last draw back is the lack of windows in the cargo hold / passenger area.  As I viewed this as a utility platform this was not addressed in this design cycle. (Link your mobile to an exterior camera?)  This is not a perfect solution but it perhaps a workable solution for many problems.  

Despite the drawbacks it does solve many of the problems that rotor-craft face.  They are also a bit dangerous when the rotor is turning and breezy when entering under the prop.  The Arbalest has a plus in that the pilot would not need rotorcraft certification.  This in itself would reduce running costs and open the pool of man power.  Many smaller communities would find it much easier to field air ambulances and resupply because of this.

Visualization - Medical Bay of Air Ambulance

This design as drawn is developed with four main design constraints: One: To be able to land on Roads in addition to runways.  Thus it had to be narrow enough to land on medium two lane road (ca. 12m (36') surface - Link) .   Two: The Arbalest had to have a similar passenger and cargo capacity as a BlackHawk UH-60.   Two Pilots and 11 passenger or four medics and place for six stretchers (see illustration above).  Three: An Anti-Armor weapon on a swivel (Like an Apache AH-64.  In the Illustration below I have used a 25mm Bushmaster with retractable aero bay. It is locked forward when not rotating)  Four: A cargo loading door that is large enough to put a standard ISO Pallet through.

Visualization - Bush / Military Seating for 8 + 2 pallets in supplies.

Visualization - Bush Plane for Rural Locations Loading Palletized Cargo.

As a Bush Plane the Arbalest would have the range, cargo capacity and speed of a twin prop such as the King Air or Cessna Conquest with the landing distance of Super Cub.  That could be a pretty handy combination.  Due to the depth of the wing area there is plenty of room in the fuselage for rough field landing gear.

Visualization - Combat Air Support and Intelligence Gathering firing 25mm Bushmaster.

This aircraft is not designed to be the fastest, baddest, or the most stealthiest, but rather something that can fill many roles.  It could be stationed close to the front lines for Army Air Units.  It has enough room for passengers / cargo / weapons / fuel / electronic warfare gear or whatever it needs to get kitted up.  It is small enough to land on a road or improvised runway.  It is large enough to carry a fair load cargo or people.  It could travel a long distance or it could loiter on station for long periods of time.  (Just add a WC).  ;-)  It could be a Bush Plane, an Air Ambulance,  Search and Rescue or Combat Air Support.  Importantly there are few complex systems that would add great expense to the platform.

Estimated Specifications: 

General Characteristics:

• Composite construction throughout

• Crew 1-2

• Passengers: Typical 8 (up to 12)

• Empty Weight: ca 2700kg (with ceramic armor for pilots and engines)

• Maximum Load: ca. 2500kg

• Wingspan: 10m 

• Wing Area (Lifting body) 32m2

• Power Plants: Pratt & Whitney Canada PT6 (1600hp)

Performance:

• Speeds: Stall 75km/h, Cruise 450km/h, Top +730 km/h

• Range: +3000km (5000km with external tank)

• Flight Ceiling: 10000m - 11000m (due to Lifting Body)

Performance Calculations Raymers "Simplified Aircraft Design Spreadsheet" (link).  These were cross referenced to the performance of the Voight XF5U and other aircraft os similar dimensions and performance.  That said they remain estimates. 

In closing: This is a great design problem.  It is very difficult to get the right mix of size, speed, cargo capacity and other capacities.  A well-balanced design is always the result of many revisions that create something that appears so simple that it appears to be the " intuitive" solution.  I am sure in time there will be new technology and design paradigms that deal with this problem set.

Updates:

None:

Sources:

Many points of information were taken from Wikipedia.

 http://www.worldaffairsboard.com/showthread.php?t=41634

https://en.wikipedia.org/wiki/Cessna_208_Caravan

http://www.politicsdaily.com/2010/04/09/air-force-eyes-mud-fighters-for-afghanistan-maybe/

http://militarynuts.com/index.php?showtopic=1460

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http://nation.time.com/2013/04/02/costly-flight-hours/

http://www.flightglobal.com/news/articles/usaf-estimates-f-35-will-cost-32000-per-hour-to-operate-386430/

http://www.dept.aoe.vt.edu/~mason/Mason_f/F22Spr11.pdf

http://www.scribd.com/doc/16228033/Air-Tractor-At-802u-Brochure#scribd

http://www.airforce-technology.com/projects/su25/

http://www.thinkdefence.co.uk/2014/09/low-cost-manned-istar/

http://aviationweek.com/defense/usaf-eyes-new-era-close-air-support

https://medium.com/war-is-boring/the-u-s-air-force-quashed-concerns-about-dumping-the-a-10-c1ed3c23e807

http://www.airspacemag.com/videos/category/military-aviation/one-tough-airplane/

http://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=1128

http://www.luft46.com/misc/sackas6.html

http://foxtrotalpha.jalopnik.com/lockheed-moves-foward-with-big-blended-wing-hybrid-tran-1726883912

http://www.bushplanedesign.com/

http://foxtrotalpha.jalopnik.com/heres-exactly-how-congress-wants-to-measure-the-a-10-wa-1773949233

http://warontherocks.com/2016/05/its-not-about-the-airplane-envisioning-the-a-x2/?utm_source=fark&utm_medium=referral&utm_campaign=im