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As we now have entered the second decade of the twenty-first century, and much of the available marketplace for aircraft that are designed for a family of four consist of designs that hark back from the 1950’s and 1960’s (fifty-sixty years ago) I thought it appropriate to trip the light-fantastic and consider what the twenty-first century family aircraft design should be, instead of what it currently is; so here goes...
First, the issue of what type of fuel should power this new general aviation aircraft? AVGAS is slowly being phased-out around the world, with just one or two alternatives currently under development; therefore I believe that we must design away from this venerable but boutique fuel.
As the Solar Impulse and other aircraft have proved, electric propulsion is fast becoming a viable option. The power-to-weight ratio is still problematic with this system of power, therefore it believe that this generation’s family aircraft design, from now on I shall call it the Family-Flyer, will have to utilize both a combustion and electrical power system, much like today’s Hybrid motorcars. Forget requiring a gasoline type of fuel though. It makes more sense to go with either a hydrogen or diesel burning engine instead. Obviously the thrust shall be derived both by internal combustion and by electrical motor power.
Next we are faced with the issue of how to convert the power produced by our hybrid engine into thrust? Will we be using a propeller, a gas turbine, exhaust jets, impulse engines, rockets; what? Personally I believe that there is much merit found in the Un-ducted Fan system that was developed by General Electric in the early 1980’s. Their prototype system delivered 35% or more in fuel efficiency over the turbo-fans that they were designed to replace. This concept is now back in-play by many airframe and engine manufacturers, with the intent to deliver greater fuel savings to the buyers of their large-cabin airline and military products; therefore I hereby declare that the Family-Flyer shall derive its propulsion from two un-ducted fans.
It might be argued that I have put the cart before the horse, so-to-speak, by choosing a propulsion system before thinking about the design of the airframe. Well you are welcome to your opinion, but my line of thinking is similar to the starting concept that most modern aircraft designers use today. The airframe is now built around the propulsion system.
Obviously we want our design to fly high and fast, while still being able to fly-in-and-out of short-ish runways, be safe and relatively easy to control. Be able to provide a quiet, comfortable and safe environment for the passengers and crew, and capable of carrying fuel-fuel, four 200 lb people and their associated baggage, with a large margin left in its weight and balance envelope for safety. It also has to be affordable, i.e. somewhere in the $500,000 target selling range would be ideal.
The airframe of the Family-Flyer shall be constructed from epoxy cured Carbon Fibre. The engines shall be mounted on the top-side of the wings ala Vereinigte Flugtechnische Werke (VFW)-Fokker 614 of the early 1970’s, and the 21st-century Honda-Jet HA-420. It will have spiroid winglets which shall deliver more than a 10% reduction in fuel-burn because of the reduced drag and increased aspect ratio.
The spiroid winglets shall be blended into a reflex-curved high-performance wing that features a wide and thick-corded inboard section that shall provide lots of lift both during climb and during slow approaches. The wings shall feature fowler flaps and leading-edge slats. All of these aerodynamic devices shall provide the aircraft with stellar low-and-slow, as well as excellent climb performance. Higher cruise speeds will be delivered thanks to the thin, near-super-critical high-aspect ratio outboard wing sections that will accelerate flow thanks to the reflex curves on the trailing edge sections. The wings will be able to fold, electrically to enable the Family-Flyer to fit a standard T-Hanger. As I mentioned earlier, the Family-Flyer is a twin-engine design.
Cruise attitude and pitch control will be provided by a cruciform empennage that features a split rudder that will also act as an air-brake. The all-moving horizontal stabilizer will be supplemented by stub- canards mounted on the forward nose section. The trim system will be independent of all other flight controls enabling control redundancy if ever the need arose. All communications and navigation antennas shall be laid-up within the plies of the empennage leading edges. These antenna arrays shall back-heated (to reduce EMI as well as maintenance) to provide anti-icing protection. The wing leading edges shall also incorporate heat blankets which can easily be replaced due to filament failure.
The undercarriage will be electrically actuated. The system will be extremely simple whereby the main legs shall fold/splay outward and be stiff-legs. The running gear shall be of the trailing link style. The nose gear will retract forward and it will also feature trailing dual axles. The emergency gear drop system shall be cable operated, whereby the actuator rod-ends shall disconnect and a simple blow-down gas-tube actuator shall override the disconnected screw system and ultimately hold as the down-lock. The main wheels shall feature anti-lock carbon-fibre brakes.
The fuel system will incorporate integral wet-wings inboard, along with fuel storage under the floor. The fuel shall be heated from the natural bonus heating that shall occur from the solar cell panels on the top of the wings. The lithium batteries shall be mounted both in the nose, and in the fuselage aft of the cabin; all shall be stored beneath the easily removed baggage floors in the same cavities.
When the combustion engines are providing thrust, the electric motors shall act as alternators, and shall charge the battery system, just like an automotive hybrid. During the day the solar cells shall provide charge. During night-time operations the wind generators (min-turbines embedded in the vertical stabilizer leading edge shall provide a charge also.
The interior shall be more like an automobiles, however the seats shall feature full harnesses that incorporate an airbag system. The seats shall also feature airbags as well. The Family-Flyer shall be air-conditioned and lit by fibre-optic edge lights and LED assemblies. The cabin shall be both pressurized and air conditioned. There will be a crew door on the captain’s side, while main cabin entry will be accessible through a main entrance air-stair door on the LH rear of the cabin.
The Avionics suite shall consist of three separate LCD monitors that have synthetic vision, primary flight displays, weather depiction and navigation overlays, along with airspace, charts and approach plate depiction. An entertainment and Internet mode shall also be incorporated as an available feed. The engine, electrical and environmental systems shall also be depicted in computerized format, but all three displays will be switchable amongst themselves. Certain add-ons shall be down-loadable just like ‘Aps’ used in in the Smart-phone marketplace.
All communications shall be accessed by touchscreen on either lower side-panel, and all audio shall be delivered by blue tooth, with cabin isolation as a switchable feature. The cabin shall have mini-LCD monitors at each seat that will allow entertainment and Internet feeds to be displayed. There will also be Droid and iPod docking stations at each seat (both crew and passenger) to stream and play personal content, and also allow in-flight communications via the WiFi and Blue-Tooth enabled features within this pleasant cabin space.
Lastly a cooler, hot-cup, mini-microwave, wireless printer and waste receptacle shall be located at the front of the cabin accessible by all occupants.All cabin windows shall feature Smart-Glass that can have the opaqueness and tint adjusted electrically. Both crew stations shall have a swing-out work surface that stows beneath the instrument panel, while the main cabin shall have a floor stow-able worktable that will bridge the gap between the two seats. If mortal peril is imminent for all occupants, the Family-Flyer shall be protected by a ballistic parachute similar to the Cirrus.
After reading this written depiction of what I believe this century's family aircraft should feature, you will agree that 90% of what I have mentioned is currently available today on a variety of designs. All that is necessary is for someone to clone them all together into one specific aircraft design...one hope that maybe Scaled Composites as one of the many capable design companies might consider doing this once the Virgin Galactic program has been completed? We can all but hope.
What design do you see in your minds eye, when you tackle the issue of what the Family-Flyer of today should look like? Please comment below, as both I and your fellow readers will be very interested to read your point of view.