Airtruk Airdynecraft
Transavia PL-12 Airtruk
The Transavia PL-12 Airtruk is a single-engine agricultural aircraft designed and built by the Transavia Corporation in Australia. The Airtruk is a shoulder-wing strut braced sesquiplane of all-metal construction, with the cockpit mounted above a tractor-location opposed-cylinder air-cooled engine and short pod fuselage with rear door. The engine cowling, rear fuselage and top decking are of fibreglass. It has a tricycle undercarriage, the main units of which are carried on the lower sesquiplane wings. It has twin tail booms with two unconnected tails. Its first flight was on 22 April 1965, and was certified on 10 February 1966.[2]
A Transavia PL-12 featured in the 1985 movie Mad Max Beyond Thunderdome.

Design and development
It was developed from the Bennett Airtruck designed in New Zealand by Luigi Pellarini. It has a 1 tonne capacity hopper and is able to ferry two passengers as a topdresser. Other versions can be used as cargo, ambulance or aerial survey aircraft, and carry one passenger in the top deck and four in the lower deck.

The Airtruk is also sometimes known as the Airtruck. Because the name "Airtruck" was registered by the New Zealand companies Bennett Aviation Ltd and Waitomo Aircraft Ltd, for their PL-11, Transavia found another name for their PL-12 ("Airtruk").

July 1978 saw the first flight of an improved model, the T-300 Skyfarmer, which was powered by a Textron Lycoming IO-540-engine. This was followed in 1981 by the T-300A with improved aerodynamics.[2] Transavia ceased production of the T-300 in 1985.

In 1982 certification was undertaken to enable sales in the North American market. Assistance was provided by the Aeronautical Research Laboratories (ARL) of the Defence Science and Technology Organisation (DSTO) and extensive tests carried out on the ground and in subsequent flight flutter clearance trials. ref. DSTO Structures Tech. Memo. 341

In 1985 an extended version was produced and released as the T-400. The engine was changed from a 6-cylinder to an 8-cylinder and the tail booms extended by 750 millimetres (30 in). Other minor changes were made to the aerodynamics. Flutter clearance tests were again carried out by ARL and manufacture proceeded.[3]

An isolated flutter incident was reported in 1986 involving violent oscillations of the rudder and tail boom on the T-400 during a delivery flight. Investigations were carried out by ARL and a split mass balance arm was fitted to each rudder. Prior to this the aircraft had relied on frictional damping provided by the lengthy control cables. The modified aircraft was tested both on the ground, and in flight trials in March 1988 over Port Philip near Melbourne, Australia. All attempts to induce the oscillations showed that there was no indication of a mode of vibration becoming unstable. The maximum speed achieved was 160 knots (180 mph; 300 km/h) in a steep dive. Oscillations were induced with an air operated tool fitted with an out-of-balance rotating mass. This device had a rotational speed from 18 Hz down to zero for each charge of the compressed air cylinder.[4]

At least 120 had been built by 1988.[2] ...

General characteristics
    Crew: 1
    Capacity: 2 pax / 2,000 lb (910 kg) dry chemicals or 818 L (216 US gal; 180 imp gal) liquids
    Length: 21 ft 0 in (6.4 m)
    Wingspan: 39 ft 4 in (11.98 m)
    Height: 9 ft 0 in (2.74 m)
    Wing area: 256 sq ft (23.8 m2)
    Airfoil: NACA 23012
    Empty weight: 1,709 lb (775 kg) :: PL-12U 1,830 lb (830 kg)
    Max takeoff weight: 4,090 lb (1,855 kg) (agricultural mission)
    Fuel capacity: 181.5 L (47.9 US gal; 39.9 imp gal) in two upper wing fuel tanks with optional second tank in each wing for a total of 373 L (99 US gal; 82 imp gal)
    Powerplant: 1 × Rolls-Royce/Continental IO-520-D 6-cyl. air-cooled horizontally opposed piston engine, 300 hp (220 kW)
    Propellers: 2-bladed McCauley D2A34C58/90AT-2 constant speed metal propeller, 7 ft 4 in (2.23 m) diameter

    Maximum speed: 103 kn (119 mph, 191 km/h) :: PL-12U 112 kn (129 mph; 207 km/h)
    Cruise speed: 95 kn (109 mph, 176 km/h) at 75% power at Sea level ISA
        PL-12U 102 kn (117 mph; 189 km/h)
    Stall speed: 52 kn (60 mph, 96 km/h) flaps down
        PL-12U 50 kn (58 mph; 93 km/h)
    Never exceed speed: 180 kn (210 mph, 330 km/h) :: PL-12U 150 kn (170 mph; 280 km/h)
    Rate of climb: 600 ft/min (3.05 m/s) :: PL-12U 4.066 m/s (800.4 ft/min)
Transavia Airtruk & Skyfarmer

The Airtruk and Skyfarmer owe their origins to New Zealand's first commercial aircraft, the Waitomo Airtruck. The original Waitomo Airtruck was designed by Luigi Pellarini in the mid 1950s, and used a number of components from the North American T6 Texan/Harvard series of piston engine military advanced trainers. These components included main undercarriage wheels, the front undercarriage assembly, fuel tanks and the 410kW (550hp) Pratt & Whitney R1340 radial piston engine. The Airtruck also featured a fairly tall and squat fuselage that accommodated a pilot, two passengers and a chemical hopper, tricycle undercarriage, a high mounted wing and boom mounted twin tails. The unusual twin tail configuration was adopted as it solved the problem of chemicals contaminating the rear fuselage, while it also allowed easier loading of the chemical hopper. The Airtruck first flew on August 2 1960. The Airtruck was not built in New Zealand, and instead was further developed in Australia by Transavia as the PL12 Airtruk. The Airtruk differed from the Airtruck in having a flat six Continental engine and additional lower stub wings. It was delivered from December 1966. The PL12U utility seats five and has the chemical tank deleted. It was delivered from 1971. The T300 and T300A Skyfarmers are improved developments of the PL12 with a Textron Lycoming IO540 engine; the T300 first flew in July 1971, the T300A, which introduced aerodynamic improvements, first flew in 1981. The final development was the 300kW (400hp) flat eight IO720 powered T400, four were delivered to China. Production ceased in 1993.
PL12U - One 225kW (300hp) Continental IO520D fuel injected flat six piston engine driving a two blade constant speed McCauley propeller. T300A - One 225kW (300hp) Textron Lycoming IO540 fuel injected flat six driving a three blade constant speed Hartzell prop.
PL12U - Max cruising speed 188km/h (102kt). Initial rate of climb 800ft/min. Service ceiling 10,500ft. Range with max payload 1205km (650nm), with max fuel 1295km (700nm). T300A - Max speed 196km/h (106kt), max cruising speed (75% power) 188km/h (102kt). Initial rate of climb 515ft/min. Service ceiling 12,500ft.
PL12U - Empty 830kg (1830lb), max takeoff 1723kg (3800lb). T300A - Typical empty 955kg (2100lb), max takeoff (ag category) 1925kg (4244lb).
PL12U - Wing span 12.15m (39ft 11in), length 6.35m (20ft 10in), height 2.79m (9ft 2in). Wing area 23.5m2 (252.7sq ft). T300A - Wing span 11.98m (39ft 4in), length 6.35m (20ft 10in), height 2.79m (9ft 2in). Wing area (including lower stub wing) 24.5m2 (264.0sq ft).
Single pilot in all versions. PL12, T300 and T400 - Seats for two passengers and fitted with a chemical hopper. PL12U seats five with no hopper.
Total production of 120 plus, including 18 assembled in New Zealand. Production complete.
Related Links
Transavia Airtruk & Skyfarmer
The backbone of this section is from the The International Directory of Civil Aircraft by Gerard Frawley and used with permission.


[ PDF ]

This present invention relates to subsonic aeroplanes, of any subsonic speed potential or of any size and use, which are endowed with a much greater economic potential than equivalent aeroplanes presently known, of equivalent size and power. As these aeroplanes, which form the object of the present invention, are endowed also with a different configuration as compared to known aeroplanes, they are called airdynecrafts, for distinction. The airdynecraft's new configurations and high economic potential are obtained by using known components most of which perhaps are common to any other existing aircraft, which components however are assembled in one final unit according to a new design pattern so as ultimately to obtain a flying craft capable to exploit more efficiently the potential energy that it carries and able also to comply more accurately with the first degree of flexibility of the atmospheric environment than the already known aircraft types The main advantages of the airdynecraft of the present invention, as compared to the same category of payload capability aircraft of current standard design, ares (1) Total utilisation of fuselage volume; (2) Less structural penalty (due to aero-elastic fatigue); (3) Embodiment throughout of fail-safe concepts at no weight penalty (4) Greater safety in emergency Take-Off-Landings (5) Comparatively much smaller overall dimensions and empty weight and therefore manufacturing cost; (6) More centralised thrust line with power-plant acting at rear of the fuselage; (7) Minimum shift of centre of gravity from empty to all up weight arrangements due to triangular distributions of payload into the delta planform fuselage; (8) Relatively smaller mass inertia about co-ordinates Y and Z; (9) Less wetted area to lift area ratio therefore max. substantially enhanced (C^ is the co-efficient of drag; and Cis the co-efficient of lift);

(10) Smaller wing loadings relative to wetted area and aspect ratio; (ID Less power required relative to payload and reduced operating cost; less noise and pollution;

(12) Intrinsic antiauto rotation characteristic due to fuselage lift above centre of gravity; (13) Increased payload to structural weight ratio, (due to self lifting fuselage); (14) Softer and shorter Take-Off-Landings due to forward wing and fuselage cushion ground effect;

(15) Substantial total lift gain due to fuselage in spite of the airflow momentum losses due to tandem wings in cascade of airfoils;

(16) Enhanced total lift due to forward wing lift and power plant thrust relationship; (17) Approximate spanwise eliptical distribution of overall lift; Less yawing and rolling unbalanced moments inthe event of engine failure; (19 Minimum structural damage in emergency landings; (20 Multiplicity of common and interchangeable components of comparably small size (economy); (21 Sectional fuselage in smaller size aircraft (manufacturing economy); (22 Larger useful floor areas for payload (passengers and/or cargo); (23 Versatility of use; (24 Panoramic vision (small size aircraft)? (25 Clean lifting surfaces free from engine presence (lower wing drag); (26 Shorter undercarriages; (27 Protection of engines from birds and debris - fire hazard greatly reduced; (28) Life saving factor unparallelingly high even in the event of landings on water. In one broad form the invention comprises an airdynecraft provided with a streamlined delta planform shaped fuselage, longitudinal airfoil sections which c&n vary their camber, two shoulder wings, in tandem and cascade at negative angles of incidence in respect of the zero lift angle of the fuselage, and a power plant system, located wholly or partly on top of the rear section of the fuselage^ said fuselage also carries internal compartments for payloads which are devised and arranged in accordance with both the planform tapering and the flying attitude (angle of attack) of the airdynecraft. In another form the airdynecraft comprises a narrow delta or approximately delta planform fuselage with a parabolically streamlined nose whose longitudinal section contours form low drag high lift aerodynamic airfoils of variable camber (and therefore of variable aerodynamic characteristics), said delta planform fuselage carrying two comparatively small-span shoulder type wings, in a close tandem set and in a narrow cascade of airfoils, whose mean aerodynamic chords form small positive angles, or even negative angles of incidence in respect to the zero-lift incidence of the fuselage mean aerodynamic chord and said delta fuselage carries the full power plant system or a portion of it above its upper skin, and as far as possible rearward in respectto its centre of gravity. In the accompanying drawings which are shown merely by way of example and illustration, two preferred forms of embodiments of the present invention approximately at the beginning and at the end of a vast range of intermediate practical applications in accordance with payloads and speeds are shown. The invention and its advantages shall become clearer from the following description with reference to the accompanying drawings in which: Figures 1, 2 and 3 represent basic views of an embodiment of the present invention? Figure 4 is a floor view of the above embodimentFigure 5 shows a longitudinal section of the above embodiment in taxiiing attitude and/or in emergency landing attitude?Figure 6 shows a fuselage according to this invention made by component parts; Figure 7 shows a schematic view of an embodiment of the airdynecraft showing relative forces produced by the thrust of the power plant located at the rear of the fuselage; Figure 8 represents a partial longitudinal section of a common leading edge slot as it is found in both wings; Figures 9, 10 and 11 are three orthogonal views of another embodiment of the invention showing a larger airdyne- craft of high subsonic speeds, with 400 to 450 passengers capacity and two jet engines as the power plant; Figure 12 is a floor view of the airdynecraft of Figures 9 to 11; and Figure 13 is a longitudinal section of the rear portion of the larger airdynecraft. The airdynecraft as envisaged herein is endowed with the highest possible speed potential, appropriate to its use and magnitude of power installed, so as to achieve maximum flying efficiency and at the same time is endowed also with the design characteristics essential for the attainment of the lowest possible take-off and landing speeds, as desirable for the attainment of the highest safety factor possible. Both these high and low speed potentialsalthough in contrast to each other, are coexisting, in the airdynecraft, to an unparalleled degree of efficiency, since its total wetted area to usable volume and/or floor area ratios are the minimum and its usable lifting area to total wetted area ratio is the maximum that are attainable, relatively to aspect ratio adopted, irrespective of whether these ratios are com™ pared against those pertaining to known aircraft of low orhigh subsonic speed,characteristics; and these fundamentally important ratios characterising any aircraft type, together with the ratios C/Cand C3/C2 (which are also partially dependent from them) essentially represent the basic factors from which, ultimately, flight economy strictly depends. In its frontal view, the airdynecraft may appear to be associated with an excess of air resistance, in spite of its well streamlined frame components; however its frontal view misleads grossly if it is being evaluated as a drag producing factor. In fact provided that the aircraft fuselage 1, and its wings 2, 3 (forming a single body) change very gradually in cross-sectional area and longitudinal profile and provided that the longitudinal rates of change of the width and depth of the fuselage, occurring under the wings (in a cascade of airfoils), balance each other appropriately so as to blend gently with the gradually increasing or decreasing rates of change superimposed by the wings (thus minimising the losses in the airflow momentum for vorticity and swirl which may be induced by any abrupt acceleration of local masses of fluid), then the aerodynamic drag of the aircraft would be zero, if it were invested by a fluid hypothetically inviscid and incompres ible and its attitude were such of producing neither positive nor negative lift. This zero drag condition (relative to the above- mentioned assumptions) would persist, irrespective of its cumbersome frontal appearancesince the airdynecraft, characterised by the streamlined features above described, conforms strictly to the geometric rule embodied in the equation of fluid motion, due to Laplace, i.e.3⁄4JjLf--f = o; <her±Λ.±ί,ΛΛthe σχ <5y d z 0 x 6 y ό z velocity components at any point X, Y, Z, on a well streamlined body not producing lift and invested by the hypothetical fluid above-mentioned). Thus, by logical extension to practical applications, even in a stream of viscous and compressible air the drag component inherent to the airdynecraft shape and frontal appearance remains quite negligible up to the small angles of incidence of cruising flight, so long asj (a) the vortices due to the lift, which is being produced at cruising incidence, are generating only a small amount of induced drag (as it is obtainable through a set of shoulder wings in cascade of an appropriate aspect ratio A, according to the relation, induced drag, C_. =· C= 1.1 )? (b) the drag component due to viscosity (friction drag) is generated by a nearly total laminar airflow, free of eddying motions and swirls (due to surface roughnesses)? in which case such drag component is simply a function of the wetted area, of the airdynecraft, irrespective of its frontal appearance? (c) the speed is not greater than 70% (7 „) of the speed of sound? that is, up to speeds at which bodies in motion do not affect appreciably the first degree of flexibility of the atmospheric environment? (flexibility enabling every physical disturbance of the environment to travel spontaneously at constant speed through intramolecular compressive and tensile impulses without displacement of matter, therefore with minimal expenditure of energy).From perusal of Figures 9, 10 and 11 of the attached drawings it should be noted that above speeds of .7. and up to the vicinity of speed of sound, that is, when the rate of increase of the drag (relative to compressibility and tensibility of the atmospheric environment) becomes more and more effective and increasingly dependent of the ma imum cross -sectional area of any aircraft that flies at those speeds or faster (irrespective of whether such area is formed mostly by the fuselage or mostly by the remaining components) the airdynec aft as envisaged herein maintains the constant advantage of being endowed with C/Cand C3/C2 ratios consistently better than the equivalent ratios pertaining to any other comparable payload capacity aircraft of conventional type, since its maximum cross-sectional area is approximately equal oif not smaller than, the maximum cross-sectional area of the above mentioned conventional aircraft and accordingly even its total aerodynamic drag (due to compressibility and tensibility effects, to the wetted area and to the lift produced) will be equal to, if not smaller than, the drag produced by such conventional types. On the other hand the lift generated by the airdynecraft is in a greater proportion due to its fuselage (whose wetted area is efficiently exploited for the generations of such a lift and whose position in respect of the wings grants the full recovery of the upper airflow momentum losses due to the tandem wings in cascade of airfoils) and therefore this lift is bound to be higher than the lift generated by conventional aircraft whose large wetted area of fuselage does not contribute to the generation of lift Therefore even above „7. speeds and upo the speed of sound the airdynecraft has the basiccharacteristic required for flying more efficiently than any of the existing conventional aircraft. In Figures 1 and 9 the main aerodynamic chord 11 of the front wing and the main aerodynamic chord 12 of the rear wing are at negative angles of incidence, in respect of zero lift angle 13 of the fuselage, in a manner to exploit the wetted area of the fuselage as a means of generating a large amount of lift, without an excessive induced drag. The power plant 7 is positioned as far back as practical on top of the rear section of the fuselage such that as shown in Figure 7 the resultant thrust 18 of the power plant would produce a nose down pitch effect about the centre of gravity 15 of the airdynecraft to be exploited as a means for obtaining additional useful lift 16, thus creating a resultant 17 passing as close as possible to the centre of gravity, in accordance with the remaining pitching moments. In Figure 3 there is shown the main stream of the airflow above the fuselage 1 being further energised by the side airflow streams activated by the front wings 2 and the upper surface of the rear wings 3 thereby increasing substantially the lifting potential of the fuselageFor maximum possible exploitation of the airflow airstream effect,, it is convenient to locate the forward wing ^ 3⁄4t €iZl appropriate stagger distance and higher than the rear wing in order to obtain the best possible effect from the resulting cascade of airfoils„ In Figure 4 the seating arrangement of a small airdynecraft is shown, according to the teachings of this invention, which can carry 9 people as well as large luggagecompartments 21 and 22.

Figure 5 shows the resultant force 20 which wov$l<3 occur in sho^t landing conditions. In an emer ency landing, te plane can land on a skid 10 ao as t<3⁄4 shorten the landing run for safety,

Figure 8 shows a partial longitudinal section of a common leading edge slot 5 as it is found in botft w ngs 2nd 3 as can be seen the leading edge slot S is o! a no mal convenient design as found in present a^ro ^fts. In Figure 11 a view of a large passenger car ying aircraft according to this invention is shown in which a power plant 7 is supported above the fuselage, and,forms a large portion of a tail lifting surface 8 which is connected to the fin and rudder surfaces 6. The fuselage trailing edge,elevator 4 is hinged to the fuselage 1 between the fin and rudder surfaces 6. The puter section of the rear wing haq the same shape as thQ forward wing 2. A Canard surfaqe 27 may be fitted ahead and elow of the forward wing 2 so as to gain additional rotating moment and lift especially in take-off-landing conditions.

Figure 12 shows the upper and lower deck flopr view (which are almost identical except for their moat forward portion 30 and 31, representing respectively the flying deck and a small cabin on upper deck and a single larger cabin on the lower deck) of this larger airdynearaft showing a forward pressurized passenger compartment connected by a pressurized passageway 26 to a cylindrically shaped rear compartment 25. All outer surfaces of the passenger compartments being curbed as shown also by Figure 10, so that the passenger areas exhibit the high pressure strength in relation to weight of material used as required for flying at high altitudes.

The cylindrical compartment 25 may subdivide in two portions 23, 24, the otherwise very large luggage compartment which does not have to be pressurized. The cylindrical compartment 25 could be used either as a normal passenger's cabin or as sleeping compartments. 15B represents the centre of gravity for unloaded conditions. As a result of the triangular distribution of payload, there is only a comparatively small shift of the centre of gravity at all up weight 15A from that of empty condition 15B. Figure 13 shows in side elevation how the pass enger area is divided into an upper and a lower deck 28 and 29 respectively as mentioned above. The two decks as described hereincombined with the payload triangular distribution, enable the airdynecraft to carry approximately twice as many passengers that can be carried in the same length and power on aircraft of a conventional design,, In conclusion this invention, representing a fair amount of research work and testing, relates to aeroplanes of unconventional design which nevertheless, are endowed with an economic potential by far greater than that pertain- ing to presently known conventional aircraft of equivalent empty weight and power; and furthermore, they offer an unparalled degree of safety, irrespective of whether they are exploited in civil or military operations.

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A) BACKGROUND OF THE INVENTION 1) Field of the Invention:<br/> This invention relaces to aircraft of any speed, size and use, which are endowed with enhanced safety and performance, as compared to conventional existing aircraft of equivalent payload and power, in virtue of the herein described features. As these aircraft look different, they will be called airsymbiocraft; but within this description they are called symbiocrafts, for short.

2) Prior Philosophy This invention, basically, is an amelioration of the symbiotic philosophy that the ght Brothers have embodied in their canard-biplane. They must have thought that mechanical flight does net necessarily have to simulate the flight of living beings (which are bestowed with limited velocity) and consequently they devised a truly revolutionary aircraft whose configuration had enabled them to fly safely before ii I_ anyone else. However, since this application consists of a number of complementary new ideas that improve consistently the basic concept of the Wright Brothers, then even this application should form zn invention in its own right.

It may seem paradoxical to pursue substantial improvements through a recourse, for inspiration, to biplane philosophy (long ago discarded in favour of the monoplane philosophy, which has become so familiar) nevertheless the fact is that, if the aircraft engines of the sixties were made available in the thirties, to enable the biplanes to fly efficiently at high tropospheric altitude, then the aircraft C development would have occurred in accordance with the canard biplane concept, which, at very high altitude, S g* is more aerodynamically convenient than the monoplane *e concept.

C Many experts share the conviction that the present conventional monoplanes have reached their top limits of safety, performance and economy and do not foresee any substantial economic advantage in their further development as monoplanes.

Even large aeronautical companies are involved in research for alternative solutions more advantageous than those of the present conventional monoplanes, J -3since even them judge that these monoplanes have reached a stumbling block, from the performance and economy viewpoint, despite the great achievements in propulsion, aerodynamics, structures and systems, made in the U.S. in the last fifty years.

Thus, by representing one of the most advantageous alternatives, the symbiocrafts should find a worthwhile area of application, in both civil and military aircraft fields as, in reality, nothing wrong has emerged by adapting to the symbiocraft the inspired concept of the canard biplane of Orville and Wilbur Wright, who have invented the mechanical means more convenient to fly safely and more eccnomically.

3) References and Experimental Findings in Unconventional Art:<br/> 0 0 a) FLYING WING AIRCRAFT characterised by: Simplicity, but low operating efficiency; low volumetric efficiency;<br/> lack of rotational angle of incidence in take-offe 5 landing; small wing loading; mediocre potential of development.

b) MULTIPLE FUSELAGE AIRCRAFT characterised by:<br/> Sufficient operational efficiency and good development potential but Jack of speed potential; excessive spanwise mass inertia; absence or difficult intercommunication.

7 -4c) LIFTING BODY AIRCRAFT characterised by: Insignificant operational efficienty; very low empty weight but of no use at subsonic speeds, if it is exploited alone.

d) SPANLOADER AIRCRAFT characterised by: Mediocre operational efficiency; lack of speed potential;<br/> mediocre volumetric efficiency; excessive lateral intertia; poor flying performance especially in takeoff/ andings; only apparent both simplicity and small empty weight.

15 e) AIRDYNECRAFT (as per above U.S. Patent 4 030 0 68) characterised by: Good operational efficiency;<br/> good volumetric efficiency; low empty weight, acceptable mass inertia on all three orthogonal axis; good flying 5 performance.

However: a large scale radio controlled model of the airdynecraft, during it reiterated flights in performing take-off/landings has manifested a 20 degree of potential danger, which was not evident in the wing-tunnel testings previously made with smaller mcdels. Such potential danger was due to adverse effects of the ground air-cushion, because of rotational peculiarities at take-off stage, since above a height of 2-3 times its wing m.g,c. from the ground, the model behaviour was very good and and comparatively competitive.

To get rid of such serious handicap were required various design alterations, starting from a gradual reduction of the main-plane aspect ratio of the model, and arriving to a stage in which the above mentioned U.S. Patent 4 030 688, was definitely superseded by the present concept embodied in this invention for which application now is made under the name of "Symbiocrafts".

*4 30 4) Comprehensive Principa Advantages of the U.

Invention:<br/> A new configuration and a particular type of structure providing greater and more chances of safety in general (and in particular during S* emergency landings on rough grounds or water).

0 U A configuration more suitable to carry simultaneously 35 passengers and more luggage (if the carrier is small), or a greater number of passengers and large or heavy cargo, (if the carrier is comparatively large), while providing maximum volumetric and structural efficiency for both types of payloads.

A configuration more suitable to cruise at higher jl I -6altitude, hence more economical cruising.

A configuration comparatively shorter and packed;<br/> which leads to symbiocrafts of comparatively small weight and mass inertia; therefore more suitable for further development in size and payload capacity; without imposing, for many years ahead, extensions or additional airport tarmacs or runways. In fact, the symbiocrafts can perform take-off/landings from runways no longer than those needed for conventional ~aircrafts capable of carrying only half the maximum payload carried by symbiocrafts of equal o*9 length. Therefore, the present airport runways S could remain adequate until the volume of airo traffic is much greater, (should the symbiocrafts be used).

f 10 5) Clarification concerning the description of the Symbiocrafts
Having found that the present invention is consistent and useful even if it applies to very small and slow symbiocrafts flying at relatively low altitude as well as it applies also to supersonic aircraft in general, wherein the velocity becomes imperative in determining their configuration and type of structure, the description of the invention IJ -7that follows will refer separately to small, large and supersonic symbiocrafts, so as to simplify the task of explaining them.

B) SUMMARY OF THE INVENTION Various short-comings of the known aircraft designs have been resolved by the present invention by providing new arrangements of aircraft components and new configurations which suit most of the civil S* and military aircraft, irrespective of whether they Are small or large, subsonic or supersonic.

The subsonic symbiocrafts, in fact, comprise a a lower and an upper-mainplane which are held together a by a pair of fins and rudders and a central air-streamlined pilon in manner to form an aircraft with rolling, directional 25 and pitching stability and maneuvrability; wherein the lower-mainplane is similar to a blunt wedge, whose longitudinal sections form thick contours of low drag airfoils; while the upper-mainplane is more or less similar to a conventional wing of fast characteristics and great aspect ratio; hence of great lifting potential.

Therefore the main function of the lower-mainplane in the context of this invention, is to provide larte amounts of useful space for payload and fuel and also to provide an efficient basic structure for the whole symbiocraft; while the main function of the upper-mainplane -8is the generation of economical lift and good performance.

The supersonic symbiocrafts, has a configuration broadly similar to that above described, except that ooth its mainplanes, in this case, are endowed with supersonic characteristics; hence both of them are endowed with small span and small thickness ratio; thereby the payload is carried by a slander fuselage which is supported by either the upper or the lower mainplane; but preferably by the upper-mainplane, so as to make the lower-mainplane housing the power plant and undercarriage away from a a a the fuselage.

e S* The invention, especially when it refers to large symbiocrafts, may also include two approximately horizontal winglets protruding from the top-rearsides of the lowermainplane and extending outwardly to receive and structurally connect at their tips two fin and rudder units, which C extend upwards until they reach, or surpass, the bottom skin of the upper-mainplane sides so as to structurally connect them with the lower-mainplane sides; and may S extend also downwards, so as to support an engine on each side of the lower-mainplane; thus forming part of the main central power-plant system of the symbiocrafts, when so it is preferred or necessary. Besides, such winglets would increase the aspect ratio of the lowermainplane.

The invention, furthermore, includes a power-plant system formed by a single, or a group of propulsive engines concentrated in proximity of the vertical plane of symmetry of the lower-mainplane, near its trailing edge, and may be fully exposed or housed into the body thickness of the trailing edge of the central portion ot the lower-mainplane. The power-plant, or portion ot it, may also hang trom the upper-mainplane; especially an small symbiocrafts or on supersonic ones.

S* The invention also comprises a canard surface, protruding from the sides of the nose of the lower-mainplane, preferably attached to its bottom; said surface being characterised by its relative smallness in span and area; hence lightness and simplicity.

20 The invention also includes symbiocrafts with a main under-carriage at a rearward station behind the symbiocrafts' centre of gravity and located underneath of the lower-mainplane, and inwardly from its leading edges and trailing edges, at a sufficient distance from them so as to allow its full retraction into the two sides of the lower-mainplane body; the said under-carriage comprising a train of two or more legs each side, which carry two or more coaxial wheels endowed with trailing deflection and retraction.

Another part of the present invention is a set of two mainplanes forming the lifting surface of the large symbiocrafts one high above the other and staggered in respect of the symbiocraft C. of G. according to their different sweep-backs, which are complemented by two slender components laying longitudinally between them, in their symmetrical plane, and structurally holding two central pilons, instead of one, in order to increase the strength and stiffness of the symbiocraft and make it more suitable as a two or more stages air-space vehicle as shown by the attached drawings.

The invention also includes a lower-mainplane, 35 for large subsonic symbiocrafts, whose body is formed by two swept-back symmetrical side bodies plus one or more central interbodies; all of which, in their turn, 0 can be subdivided in adjacent compartments or lobbies for passengers or cargo so that, the compartments for passengers are fully inter-communicating, while the 0, compartments for cargo are endowed with the unique feature of a continuous and simultaneous loading and unloading of a cargo (without reverse motion) and yet both entry and exit are being located At the very end of the two sides of the airsymbiocrafts; thereby making the symbiocrafts *000 more suitable for carrying many very large roadable vehicles, (if so required), or more cargo each fiiynt.

Still another aspect of the invention is a lower mainplane of great thickness ratio sufficient to obtain a blunt leading edge for the application of powerful forward slats so as to enhance its lifting effect due 1- 11-to the ground cushion of air in take-off or landing stages; thereby reducing the take-off run or sot teninq the landing impact of the symbiocraft; hence ;tro i I(ng 1 k reliet tor its structure and its under-carriage.

A further part of the invention consists; in a lower mainplane whose relevant thickness ratio allows exploitation of most ot the internal partition walls as, S;tructural members; furthermore provides the high torsional stiffne;s and strength required for holding the upper-mainplane at the best level required for having the two mainplanes producing and transferring to one another the best of the aerodynamic and stressing effects that are appropriate to each of the two mainplanes.

And again a part of the invention consists in two mainplanes forming a biplane wherein the upper-mainplane generates lift and drag nearly at the rate fitting a two dimensional airflow shile, instead, the lower-mainplane generates lift and drag at the rate of a strong three dimensional, (or vertical) airflow; hence insignificant aerodynamic interference and well rounded lifting curve of the symbiocraft (particularly important at take-offlanding speeds).

In conclusion, this invention represents the result of research carried out with the flying model made in accordance with the previous U.S. Patent 4 030 688, -122 now abandoned, as mentioned above...