Semper Apollo 

III: An alternative evolution in aviation.

The concept that a super-high performance aircraft could be forgiving and docile while still maintaining the ability to turn tighter than most modern fighter jets has been revisited many times in the past. Sadly most of these designs remained as either concepts or prototypes. In 1995, as an afterschool project, work began on a low aspect ratio designs with extreme wing sweep. After preliminary drawings, testing on computers and verification with formulas, the third major design known simply as III seemed too good to be true. 

And all these years later, its still too good.

• A long range cruise speed of Mach 0.95 is possible by simple yet advanced wing design.
• A potential top speed of Mach 1.50 is well within the capability of the same wing
• Low approach speed and tight turn radius due to vortex lift and low wing loading.
• 2500 nm range with 1.25 hr reserves allows transcontinental range in an ISA +10 atmosphere.
• Solid construction with cockpit safety frame and blended wing/body reduces weight and allows for +9/-4g limits.
• Incredible amount of excess thrust results in lateral accelerations of 1g, initial climb rates of over 40,000 fpm and takeoff ground rolls of 700 feet.
• Low drag, light weight and excess power keep engine temperatures and fuel flows lower, resulting in low operating costs and longer engine life.
• No high altitude coffin corner.
• Head up display and synthetic vision avionics provide all weather situational awareness.
• V-tail reduces weight, drag, takeoff roll, and increases maneuverability at high angles of attack.
• Double delta design highly resistant to conventional stalls, while low wing loading keeps induced drag low.

 Running the simulator is not satisfying enough anymore! We are now at the stage of constructing scale models for wind tunnel tests. The folders and binders full of theoretical data should match up fairly closely with what is observed.

*The performance figures and images are from X-Plane version 9.41.  

Specifications

Engine: 3000 lb thrust class low/medium bypass ratio turbofan
Length: 38 ft
Wingspan: 15 ft
Height: 12 ft
MTOW: 3500 lbs
Empty Weight: 1900 lbs
Fuel Capacity: 183 US Gal (1220 lbs Jet-A)
Seats: 2
Max Payload: 500 lbs
Wing Area: 187 sq ft
Aspect Ratio: 1.2
Wing Loading: 18.7 lbs/sq ft
Thrust To Weight: 1.16 lbs/lb st



Performance
(*The performance figures are from X-Plane version 9.41. Wind tunnel tests on an actual model hopefully are coming within the next few months.) 

 (ISA +10)

While it is relatively easy to build a jet on a computer, it is staggeringly more difficult to build one for real. The multitude of designs and companies which have come and gone in the last decade are testament to the task at hand. The missing factor in some specialty aircraft is a market. Aviation is driven by passion but unfortunately passion cannot always justify the cost of purchasing an aircraft. While III does not answer everyone's needs, it answers those for which there is no current solution.  

There are no revolutionary materials or exotic powerplants in III. The airframe will be constructed of a conventional mix of aluminum, titanium, steel and in certain places, composites. The engine is required to be a small diameter turbofan much like the FJ-44-2 or JT-15D. An advanced nozzle may be required for maximum efficiency at high subsonic and supersonic speeds. The normal shock inlet does incur higher losses than a multiple oblique inlet, but it is less heavy, complex, expensive and far more forgiving of unusual attitudes and extreme angles of attack. The placement under the aircraft is designed to allow the forebody to align the airflow naturally. 

The wing is a simple design that been overlooked in the quest for higher and higher lift to drag ratios, sometimes at the expense of speed. Keeping the inertia (wing loading) of the aircraft low results in a smaller angle of attack for any given flight condition than an aircraft with a smaller wing. This reduces induced drag and eliminates one of the biggest wastes of fuel in delta wing aircraft...off design point flight. 

Being inexpensive was a design criteria of this aircraft. In high school (when Jet-A cost $1.50/gallon), the idea of being able to fill up a private jet for less than $300 and fly across the country was something that appealed to anyone who knew what it cost to run a contemporary jet. Now with fuel prices approaching 5 times that value, the idea of saving money is even more critical.

When people call jets inefficient, they are only partially right. Most jets up until the advent of the VLJs had at least 6 to 8 seats. If they were full of passengers, the cost in seat miles per gallon was low. Leave seats empty and suddenly it becomes as efficient as using a top fuel dragster to run errands around town. The key to making this jet efficient was limiting the number of seats, which limits the weight, which limits the amount of thrust needed, which limits the amount of fuel required to fly a given stage.

In statute miles per gallon, at FL550 and M 0.98, III will turn in an average of 20 mpg. With both seats occupied, it results in an efficiency of 40 seat miles per gallon. This is equivalent to the fuel economy of a full size SUV with 2 people inside...except at 10 times the speed.

Operation around airports is predicted to be easy given the avionics suite, eventual head up display and tremendous power on hand. Even though at maximum power and high speed at low altitude will be a startlingly loud event, at legal speeds of 250 knots below 10,000 feet, the aircraft will be just as startlingly quiet. Takeoffs can be accomplished with less than 70% N1, making the aircraft a better fit with controlled airspace where rocketing vertically through Class B may not be smiled upon. Still a strong climb of at least 4000 fpm with reduced power means the small amount of noise generated will be further from human ears faster than any other comparable jet.

There is no way an aircraft that looks like this could be designed without consideration given to aerobatics and possible military use. The rate of roll is easily 360 degrees per second and may require limiters in certain phases of flight. The sustained G tolerance of the pilot will be more critical than that of the aircraft. The light loading ensures that 9g can be held all day at low altitudes (below 10,000 ft). Ridiculous angles of attack and post-stall nose pointing formerly the exclusive domain of 5th generation fighter jets is now in the reach of civilian agencies. High alpha flight, creeping along at 60 knots and 30 degrees AOA is not only comfortable, but safe due to the extra 20 degree margin in the wing. Loaded rolls, split-S, and defensive turns all can be accomplished with extremely small radii. Vertical maneuvering similar to the F-22's "Pedal Turn" and Su-27's "Cobra" are also within the capabilities of this aircraft.  

Finally, safety is highly important in such a high performance aircraft that will no doubt take extensive training in order to keep up with the speed. A safety cage surrounds the occupants in case of an off airport landing. The canopy will be able to withstand a 4 pound bird in excess of 400 ktas. On board oxygen generators reduce the amount of bleed air required and backup tanks provide each occupant with oxygen in case of a loss of pressurization. The fuel tanks are insulated and self sealing, located far behind the occupants to enhance CG performance and reduce risk of injury in the event of ignition. The low stall speed means that even with an engine failure, controlled contact with the ground should be something the occupants can walk away from.

Who would want such an aircraft and what would they do with it?