The Spratt 103 is truly :
The simplest : 200 h of construction
The safest : No stall or spins and absorbs turbulences
and The most economic : Less than 4.000 €/$ with new 4 stroke injected engine
of all aircraft
– For the construction of the fuselage : no or few milling or specific turning of parts, neither bending of tubes. Only straight stainless steel tubes = about 100 hours, without special skills or tools.
– For the construction of the wings : no complicated jigs or flat tables. No dihedral or sweep angles to worry about. No cables or internal rods, no hinges, no flaps nor ailerons, no upper struts, no sewing of fabrics, no or few handling of dangerous and/or harmful products = about 100 hours, without special skills or tools.
– For the motorization used : no or few adaptation, no reductor, no fuel mixture, few vibration and noise, high potential, no exhaust to realize.
– For the piloting (‘driving !’) : only a throttle and steering wheel. No pedals or other controls.
– On ground : low and rearward masses, wide and long wheel base, fuselage without inferior roughness, effective shock absorbers, wide and large diameter wheels, footrest (no dangerous pedals …), powerful front brake, rigid seat with ‘4 points’ safety belts, headrest, electric starter, propeller protected from stones, high wing to avoid obstacles and, in the event of accident, roll bars around the pilot.
– In flight : all the exceptional advantages of the concept (no stalls nor spins, absorbs turbulence, therefore max 1.5 G felt, …), maximum visibility in all directions due to the high wing and the pusher engine (so no exhaust gas for the pilot…), good gliding ratio due to a low drag design, few vibrations and noise, no carburetor icing or loss of power at altitude due to the very reliable injection engine, great autonomy (mini 7 hours) in spite of the small fuel quantity (25 liters, with directly visible fuel level), small overall weight and low landing speed limiting damage in case of emergency landing.
3) Most economic
Due to the very short construction time and the low cost of the used materials =
Fuselage : stainless steel tubes of standard size and quality, seat, wheels, fuel tank and other accessories are from classic distribution stores = about 500 euros (+ 500 for TIG welding/professional).
Wings : spars in aluminium tubes of standard size and quality, ribs in extruded polystyrene, specific cover = about 300 euros for the 2 wings.
Engine : 4-stroke, 25 HP, with electric starter (injected Honda IGX800 recommended) + two blade propeller of 1.20m diameter, battery and other accessories = about 2.500 euros.
= A total cost of around 3.800 euros, according to invoices relating to the first machines + by group purchase of new engines or the use of used ones (ex: ‘2 CV Citroen’ car engine at 500 euros in breakage) the final cost of this aircraft can be less than 2.000 euros.
In addition, designed to withstand bad weather and occupying only a space of 4m x 1m x 1m20 (folded in 30 minutes), there will be little or no hangar cost.
In summary :
The Spratt 103, designed for versatile use (amphibious, …) is currently an ultralight single-seater in stainless steel, of pendular type with steering wheel piloting, with free and autostable two rigid wings collectively and differentially controlled.
This revolutionary aircraft (the simplest, safest and most economic) with also the simplest plans available, is registered in France as ‘pendular’ and ‘multi-axis’ Ultralight (according to the license of the user) and it complies with the USA Part 103, English SSDR and German regulations.
Span : 8 m Length : 4 m Height : 2 m
Wing area : 10 sqm Gliding ratio : ~10
Empty weight : 80 to 90 kg, without engine (+ 15 kg/2 strokes to + 45 kg/4 strokes) Maximum mass : 250 kg
Needed power : Mini 22 real hp (= 80 kgs thrust with propeller d. 125 cm)
Fuel tank : maxi 25 litres Container/baggage : 25 litres
Performance with maximum mass and 22 hp motor = Minimum speed : 45 km/h (27mph) Maximum cruising : 100 km/h (64 mph) Climb rate : 3 m/s (600 ft/s) Take off distance ~ 100 m (330 ft) Landing ~ 50 m (165 ft)