Patent Publication Number: US-11027837-B2

Title: Aircraft having thrust to weight dependent transitions

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of co-pending application Ser. No. 15/972,431 filed May 7, 2018, which is a continuation-in-part of application Ser. No. 15/606,242 filed May 26, 2017, which is a continuation-in-part of application Ser. No. 15/200,163 filed Jul. 1, 2016, now U.S. Pat. No. 9,963,228, the entire contents of each is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD OF THE DISCLOSURE 
     The present disclosure relates, in general, to aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation and, in particular, to aircraft having multiple VTOL to biplane transition procedures selected based upon the thrust to weight configuration of the aircraft. 
     BACKGROUND 
     Fixed-wing aircraft, such as airplanes, are capable of flight using wings that generate lift responsive to the forward airspeed of the aircraft, which is generated by thrust from one or more jet engines or propellers. The wings generally have an airfoil cross section that deflects air downward as the aircraft moves forward, generating the lift force to support the airplane in flight. Fixed-wing aircraft, however, typically require a runway that is hundreds or thousands of feet long for takeoff and landing. Unlike fixed-wing aircraft, vertical takeoff and landing (VTOL) aircraft do not require runways. Instead, VTOL aircraft are capable of taking off, hovering and landing vertically. One example of VTOL aircraft is a helicopter which is a rotorcraft having one or more rotors that provide lift and thrust to the aircraft. The rotors not only enable hovering and vertical takeoff and landing, but also enable, forward, backward and lateral flight. These attributes make helicopters highly versatile for use in congested, isolated or remote areas where fixed-wing aircraft may be unable to takeoff and land. Helicopters, however, typically lack the forward airspeed of fixed-wing aircraft. 
     A tiltrotor aircraft is another example of a VTOL aircraft. Tiltrotor aircraft generate lift and propulsion using proprotors that are typically coupled to nacelles mounted near the ends of a fixed wing. The nacelles rotate relative to the fixed wing such that the proprotors have a generally horizontal plane of rotation for vertical takeoff, hovering and landing and a generally vertical plane of rotation for forward flight, wherein the fixed wing provides lift and the proprotors provide forward thrust. In this manner, tiltrotor aircraft combine the vertical lift capability of a helicopter with the speed and range of fixed-wing aircraft. Tiltrotor aircraft, however, typically suffer from downwash inefficiencies during vertical takeoff and landing due to interference caused by the fixed wing. A further example of a VTOL aircraft is a tiltwing aircraft that features a rotatable wing that is generally horizontal for forward flight and rotates to a generally vertical orientation for vertical takeoff and landing. Propellers are coupled to the rotating wing to provide the required vertical thrust for takeoff and landing and the required forward thrust to generate lift from the wing during forward flight. The tiltwing design enables the slipstream from the propellers to strike the wing on its smallest dimension, thus improving vertical thrust efficiency as compared to tiltrotor aircraft. Tiltwing aircraft, however, are more difficult to control during hover as the vertically tilted wing provides a large surface area for crosswinds typically requiring tiltwing aircraft to have either cyclic rotor control or an additional thrust station to generate a moment. 
     SUMMARY 
     In a first aspect, the present disclosure is directed to an aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation. The aircraft includes an airframe having first and second wings with first and second pylons extending therebetween. The first and second wings each have first and second outboard nacelle stations. A two-dimensional distributed thrust array is attached to the airframe. The thrust array includes a plurality of outboard propulsion assemblies coupled to the first and second outboard nacelle stations of the first and second wings. The thrust array is operable to provide thrust for the aircraft. A flight control system is coupled to the airframe and is operable to independently control a rotor speed and a thrust vector of each of the propulsion assemblies. In a low thrust to weight configuration of the aircraft, transitions from the VTOL orientation to the biplane orientation include establishing a pitch down flight attitude while engaging in collective thrust vectoring of the outboard propulsion assemblies to maintain hover stability followed by collectively reducing the thrust vector angles to initiate forward flight. In a high thrust to weight configuration of the aircraft, transitions from the VTOL orientation to the biplane orientation include maintaining a level flight attitude while collectively increasing the thrust vector angles of the outboard propulsion assemblies to initiate forward flight. 
     In certain embodiments, the outboard propulsion assemblies may be unidirectional thrust vectoring propulsion assemblies. In other embodiments, the outboard propulsion assemblies may be omnidirectional thrust vectoring propulsion assemblies. In some embodiments, in the low thrust to weight configuration, the aircraft may have a thrust to weight ratio below a predetermined threshold such as a thrust to weight ratio below 1.4. In certain embodiments, in the low thrust to weight configuration, the aircraft may have a thrust to weight ratio between about 1.1 and about 1.4. In some embodiments, in the high thrust to weight configuration, the aircraft may have a thrust to weight ratio above a predetermined threshold such as a thrust to weight ratio above 1.7. In certain embodiments, the first and second wings may each have first and second inboard nacelle stations having inboard propulsion assemblies coupled thereto. In such embodiments, the outboard propulsion assemblies may be omnidirectional thrust vectoring propulsion assemblies and the inboard propulsion assemblies may be non thrust vectoring propulsion assemblies. Alternatively, the outboard propulsion assemblies may be longitudinal thrust vectoring propulsion assemblies and the inboard propulsion assemblies may be lateral thrust vectoring propulsion assemblies. In some embodiments, the first and second pylons may each include an inboard nacelle station having an inboard propulsion assembly coupled thereto. In such embodiments, the outboard propulsion assemblies may be omnidirectional thrust vectoring propulsion assemblies and the inboard propulsion assemblies may be non thrust vectoring propulsion assemblies. 
     In certain embodiments, the pitch down flight attitude while engaging in collective thrust vectoring of the outboard propulsion assemblies to maintain hover stability, may be a pitch down flight attitude of between about 10 degrees and about 20 degrees or a pitch down flight attitude of between about 20 degrees and about 30 degrees. In some embodiments, transitions in the low thrust to weight configuration may include collectively reducing in the thrust vector angles and increasing the pitch down attitude until the thrust vectors are substantially horizontal and the wings are substantially horizontal. In certain embodiments, transitions in the high thrust to weight configuration may include maintaining the thrust vector angles and increasing the pitch down attitude until the thrust vectors are substantially horizontal and/or collectively reducing thrust vector angles and increasing the pitch down attitude while maintaining the thrust vectors substantially horizontal until the wings are substantially horizontal. In some embodiments, each of the outboard propulsion assemblies may include an aerosurface. In such embodiments, transitions in the low thrust to weight configuration may include collectively tilting the aerosurfaces to create a pitch down moment on the aircraft. 
     In a second aspect, the present disclosure is directed to an aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation. The aircraft includes an airframe having first and second wings with first and second pylons extending therebetween. The first and second wings each have first and second outboard nacelle stations. A two-dimensional distributed thrust array is attached to the airframe. The thrust array includes a plurality of outboard propulsion assemblies coupled to the first and second outboard nacelle stations of the first and second wings. The thrust array is operable to provide thrust for the aircraft. A flight control system is coupled to the airframe and is operable to independently control a rotor speed and a thrust vector of each of the propulsion assemblies. In a low thrust to weight configuration of the aircraft, transitions from the VTOL orientation to the biplane orientation include establishing a pitch down flight attitude while engaging in collective thrust vectoring of the outboard propulsion assemblies to maintain hover stability followed by collectively reducing the thrust vector angles to initiate forward flight followed by further collective reduction in the thrust vector angles and increasing the pitch down attitude until the thrust vectors and the wings are substantially horizontal. In a high thrust to weight configuration of the aircraft, transitions from the VTOL orientation to the biplane orientation include maintaining a level flight attitude while collectively increasing the thrust vector angles of the outboard propulsion assemblies to initiate forward flight followed by maintaining the thrust vector angles and increasing the pitch down attitude until the thrust vectors are substantially horizontal followed by collectively reducing thrust vector angles and increasing the pitch down attitude while maintaining the thrust vectors substantially horizontal until the wings are substantially horizontal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the features and advantages of the present disclosure, reference is now made to the detailed description along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which: 
         FIGS. 1A-1G  are schematic illustrations of an aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation in accordance with embodiments of the present disclosure; 
         FIGS. 2A-2I  are schematic illustrations of the aircraft of  FIG. 1  in a sequential flight operating scenario in accordance with embodiments of the present disclosure; 
         FIG. 3  is a flow diagram of a process for prioritizing the use of flight attitude controls in accordance with embodiments of the present disclosure; 
         FIGS. 4A-4D  are block diagram of various implementations of a thrust array and flight control system for an aircraft in accordance with embodiments of the present disclosure; 
         FIGS. 5A-5C  are schematic illustrations of various line replaceable propulsion assemblies for an aircraft in accordance with embodiments of the present disclosure; 
         FIGS. 6A-6I  are schematic illustrations of a propulsion assembly having a two-axis gimbal for an aircraft in accordance with embodiments of the present disclosure; 
         FIGS. 7A-7C  are schematic illustrations of a propulsion assembly having a single-axis gimbal for an aircraft in accordance with embodiments of the present disclosure; 
         FIGS. 8A-8B  are schematic illustrations of an aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation in accordance with embodiments of the present disclosure; 
         FIGS. 9A-9B  are schematic illustrations of an aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation in accordance with embodiments of the present disclosure; 
         FIGS. 10A-10B  are schematic illustrations of an aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation in accordance with embodiments of the present disclosure; 
         FIGS. 11A-11D  are schematic illustrations of a man portable aircraft system operable for rapid in-situ assembly in accordance with embodiments of the present disclosure; 
         FIG. 12  is a flow diagram of a process for automated configuration of mission specific aircraft in accordance with embodiments of the present disclosure; 
         FIG. 13  is a block diagram of autonomous and remote control systems for an aircraft in accordance with embodiments of the present disclosure; 
         FIGS. 14A-14C  are schematic illustrations of rapid connection interfaces operable for use in coupling component parts of an aircraft in accordance with embodiments of the present disclosure; 
         FIGS. 15A-15B  are schematic illustrations of rapid connection interfaces operable for use in coupling component parts of an aircraft in accordance with embodiments of the present disclosure; 
         FIGS. 16A-16B  are schematic illustrations of rapid connection interfaces operable for use in coupling component parts of an aircraft in accordance with embodiments of the present disclosure; 
         FIGS. 17A-17B  are schematic illustrations of rapid connection interfaces operable for use in coupling component parts of an aircraft in accordance with embodiments of the present disclosure; 
         FIGS. 18A-18D  are schematic illustrations of an aircraft operable to maintain hover stability in inclined flight attitudes in accordance with embodiments of the present disclosure; 
         FIGS. 19A-19B  are schematic illustrations of an aircraft operable to translate and change altitude in level and inclined flight attitudes in accordance with embodiments of the present disclosure; 
         FIGS. 20A-20D  are schematic illustrations of an aircraft operable for external load operations in accordance with embodiments of the present disclosure; 
         FIGS. 21A-21E  are schematic illustrations of an aircraft operable to perform transitions from a VTOL orientation to a biplane orientation in a low thrust to weight configuration in accordance with embodiments of the present disclosure; and 
         FIGS. 22A-22E  are schematic illustrations of an aircraft operable to perform transitions from a VTOL orientation to a biplane orientation in a high thrust to weight configuration in accordance with embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     While the making and using of various embodiments of the present disclosure are discussed in detail below, it should be appreciated that the present disclosure provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative and do not delimit the scope of the present disclosure. In the interest of clarity, not all features of an actual implementation may be described in the present disclosure. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present disclosure, the devices, members, apparatuses, and the like described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. As used herein, the term “coupled” may include direct or indirect coupling by any means, including moving and/or non-moving mechanical connections. 
     Referring to  FIGS. 1A-1G  in the drawings, various views of an aircraft  10  operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation are depicted.  FIGS. 1A, 1C, 1E  depict aircraft  10  in the VTOL orientation wherein the propulsion assemblies provide thrust-borne lift.  FIGS. 1B, 1D, 1F  depict aircraft  10  in the biplane orientation wherein the propulsion assemblies provide forward thrust with the forward airspeed of aircraft  10  providing wing-borne lift enabling aircraft  10  to have a high speed and/or high endurance forward flight mode. Aircraft  10  has a longitudinal axis  10   a  that may also be referred to as the roll axis, a lateral axis  10   b  that may also be referred to as the pitch axis and a vertical axis  10   c  that may also be referred to as the yaw axis, as best seen in  FIGS. 1E and 1F . In the VTOL orientation, when longitudinal axis  10   a  and lateral axis  10   b  are both in a horizontal plane and normal to the local vertical in the earth&#39;s reference frame, aircraft  10  has a level flight attitude. When at least one of longitudinal axis  10   a  or lateral axis  10   b  extends out of the horizontal plane, aircraft  10  has an inclined flight attitude. For example, an inclined flight attitude may be a nonzero pitch flight attitude such as a pitch down flight attitude or a pitch up flight attitude. This operation is depicted in  FIG. 1E  with aircraft  10  rotating about lateral axis  10   b , as indicated by arrow  10   d . Similarly, an inclined flight attitude may be a nonzero roll flight attitude such as a roll left flight attitude or a roll right flight attitude. This operation is depicted in  FIG. 1E  with aircraft  10  rotating about longitudinal axis  10   a , as indicated by arrow  10   e . In addition, an inclined flight attitude may include both a nonzero pitch flight attitude and a nonzero roll flight attitude. 
     Aircraft  10  is a mission configurable aircraft operable to provide high efficiency transportation for diverse payloads. Based upon mission parameter including flight parameters such as environmental conditions, speed, range and thrust requirements as well as payload parameters such as size, shape, weight, type, durability and the like, aircraft  10  may selectively incorporate a variety of propulsion assemblies having different characteristics and/or capacities. For example, the propulsion assemblies operable for use with aircraft  10  may have difference thrust types including different maximum thrust outputs and/or different thrust vectoring capabilities including non thrust vectoring propulsion assemblies, single-axis thrust vectoring propulsion assemblies such as longitudinal thrust vectoring propulsion assemblies and/or lateral thrust vectoring propulsion assemblies and two-axis thrust vectoring propulsion assemblies which may also be referred to as omnidirectional thrust vectoring propulsion assemblies. In addition, various components of each propulsion assembly may be selectable including the power plant configuration and the rotor design. For example, the type or number of batteries in a propulsion assembly may be selected based upon the power, weight, endurance and/or temperature requirements of a mission. Likewise, the characteristics of the rotors assemblies may be selected, such as the number of rotor blades, the blade pitch, the blade twist, the rotor diameter, the chord distribution, the blade material and the like. 
     In the illustrated embodiment, aircraft  10  includes an airframe  12  including wings  14 ,  16  each having an airfoil cross-section that generates lift responsive to the forward airspeed of aircraft  10 . Wings  14 ,  16  may be formed as single members or may be formed from multiple wing sections. The outer skins for wings  14 ,  16  are preferably formed from high strength and lightweight materials such as fiberglass, carbon, plastic, metal or other suitable material or combination of materials. As illustrated, wings  14 ,  16  are straight wings. In other embodiments, wings  14 ,  16  could have other designs such as polyhedral wing designs, swept wing designs or other suitable wing design. As best seen in  FIG. 1G , wing  14  has two pylon stations  14   a ,  14   b  and four nacelle stations  14   c ,  14   d ,  14   e ,  14   f . Likewise, wing  16  has two pylon stations  16   a ,  16   b  and four nacelle stations  16   c ,  16   d ,  16   e ,  16   f . Each of the pylon stations and each of the nacelle stations includes a rapid connection interface operable for mechanical and electrical connectivity, as discussed herein. Extending generally perpendicularly between wings  14 ,  16  are two truss structures depicted as pylons  18 ,  20 . Pylon  18  is coupled between pylon stations  14   a ,  16   a  and preferably forms a mechanical and electrical connection therebetween. Pylon  20  is coupled between pylon stations  14   b ,  16   b  and preferably forms a mechanical and electrical connection therebetween. In other embodiments, more than two pylons may be present. Pylons  18 ,  20  are preferably formed from high strength and lightweight materials such as fiberglass, carbon, plastic, metal or other suitable material or combination of materials. As best seen in  FIG. 1G , pylon  18  has a nacelle station  18   a  and a payload station  18   b . Likewise, pylon  20  has a nacelle station  20   a  and a payload station  20   b . Each of the nacelle stations and each of the payload stations includes a rapid connection interface operable for mechanical and electrical connectivity, as discussed herein. In the illustrated embodiment, as no propulsion assembly is coupled to either of pylons  18 ,  20 , a nacelle station cover  18   c  protects nacelle station  18   a  of pylon  18  and a nacelle station cover  20   c  protects nacelle station  20   a  of pylon  20 . 
     Wings  14 ,  16  and pylons  18 ,  20  preferably include central passageways operable to contain flight control systems, energy sources, communication lines and other desired systems. For example, as best seen in  FIGS. 1C and 1D , pylon  20  houses the flight control system  22  of aircraft  10 . Flight control system  22  is preferably a redundant digital flight control system including multiple independent flight control computers. For example, the use of a triply redundant flight control system  22  improves the overall safety and reliability of aircraft  10  in the event of a failure in flight control system  22 . Flight control system  22  preferably includes non-transitory computer readable storage media including a set of computer instructions executable by one or more processors for controlling the operation of aircraft  10 . Flight control system  22  may be implemented on one or more general-purpose computers, special purpose computers or other machines with memory and processing capability. For example, flight control system  22  may include one or more memory storage modules including, but is not limited to, internal storage memory such as random access memory, non-volatile memory such as read only memory, removable memory such as magnetic storage memory, optical storage, solid-state storage memory or other suitable memory storage entity. Flight control system  22  may be a microprocessor-based system operable to execute program code in the form of machine-executable instructions. In addition, flight control system  22  may be selectively connectable to other computer systems via a proprietary encrypted network, a public encrypted network, the Internet or other suitable communication network that may include both wired and wireless connections. 
     Wings  14 ,  16  and pylons  18 ,  20  may contain one or more of electrical power sources depicted as one or more batteries  22   a  in pylon  20 , as best seen in  FIGS. 1C and 1D . Batteries  22   a  supply electrical power to flight control system  22 . In some embodiments, batteries  22   a  may be used to supply electrical power for the distributed thrust array of aircraft  10 . Wings  14 ,  16  and pylons  18 ,  20  also contain a communication network including the electrical interfaces of the pylon stations, the nacelle stations and the payload stations that enables flight control system  22  to communicate with the distributed thrust array of aircraft  10 . In the illustrated embodiment, aircraft  10  has a two-dimensional distributed thrust array that is coupled to airframe  12 . As used herein, the term “two-dimensional thrust array” refers to a plurality of thrust generating elements that occupy a two-dimensional space in the form of a plane. A minimum of three thrust generating elements is required to form a “two-dimensional thrust array.” A single aircraft may have more than one “two-dimensional thrust arrays” if multiple groups of at least three thrust generating elements each occupy separate two-dimensional spaces thus forming separate planes. As used herein, the term “distributed thrust array” refers to the use of multiple thrust generating elements each producing a portion of the total thrust output. The use of a “distributed thrust array” provides redundancy to the thrust generation capabilities of the aircraft including fault tolerance in the event of the loss of one of the thrust generating elements. A “distributed thrust array” can be used in conjunction with a “distributed power system” in which power to each of the thrust generating elements is supplied by a local power system instead of a centralized power source. For example, in a “distributed thrust array” having a plurality of propulsion assemblies acting as the thrust generating elements, a “distributed power system” may include individual battery elements housed within the nacelle of each propulsion assemblies. 
     The two-dimensional distributed thrust array of aircraft  10  includes a plurality of inboard propulsion assemblies, individually and collectively denoted as  24  and a plurality of outboard propulsion assemblies, individually and collectively denoted as  26 . Inboard propulsion assemblies  24  are respectively coupled to nacelle stations  14   e ,  14   f  of wing  14  and nacelle stations  16   e ,  16   f  of wing  16  and preferably form mechanical and electrical connections therewith. Outboard propulsion assemblies  26  are respectively coupled to nacelle stations  14   c ,  14   d  of wing  14  and nacelle stations  16   c ,  16   d  of wing  16  and preferably form mechanical and electrical connections therewith. In some embodiments, inboard propulsion assemblies  24  could form a first two-dimensional distributed thrust array and outboard propulsion assemblies  26  could form a second two-dimensional distributed thrust array. In other embodiments, inboard propulsion assemblies  24  and outboard propulsion assemblies  26  could form a single two-dimensional distributed thrust array. 
     In the illustrated embodiment, inboard propulsion assemblies  24  and outboard propulsion assemblies  26  have difference thrust types. For example, outboard propulsion assemblies  26 , individual and collectively, may have a higher maximum thrust output than inboard propulsion assemblies  24 . Alternatively or additionally, outboard propulsion assemblies  26  may be variable speed propulsion assemblies while inboard propulsion assemblies  24  may be single speed propulsion assemblies. In the illustrated embodiment, inboard propulsion assemblies  24  are fixed pitch, variable speed, non thrust vectoring propulsion assemblies while outboard propulsion assemblies  26  are fixed pitch, variable speed, omnidirectional thrust vectoring propulsion assemblies. In this regard, inboard propulsion assemblies  24  and outboard propulsion assemblies  26  each form a two-dimensional distributed thrust array of a different thrust type. Specifically, inboard propulsion assemblies  24  may be referred to as a two-dimensional distributed thrust array of non thrust vectoring propulsion assemblies. Likewise, outboard propulsion assemblies  26  may be referred to as a two-dimensional distributed thrust array of omnidirectional thrust vectoring propulsion assemblies. Including a two-dimensional distributed thrust array of omnidirectional thrust vectoring propulsion assemblies on aircraft  10  enables aircraft  10  to maintain hover stability when aircraft  10  is in a level or inclined flight attitude state. In addition, the use of a two-dimensional distributed thrust array of omnidirectional thrust vectoring propulsion assemblies on aircraft  10  enables aircraft  10  to translate and/or change altitude while maintaining a level or inclined flight attitude or while changing the flight attitude state of aircraft  10 . 
     As illustrated, outboard propulsion assemblies  26  are coupled to the outboard ends of wings  14 ,  16 , inboard propulsion assemblies  24  are coupled to wing  14  in a high wing configuration and inboard propulsion assemblies  24  are coupled to wing  16  in a low wing configurations. Propulsion assemblies  24 ,  26  are independently attachable to and detachable from airframe  12  such that aircraft  10  may be part of a man portable aircraft system having component parts with connection features designed to enable rapid in-situ assembly. Alternatively or additional, the various components of aircraft  10  including the flight control system, the wings, the pylons and the propulsion assemblies may be selected by an aircraft configuration computing system based upon mission specific parameters. This may be enabled, in part, by using propulsion assemblies  24 ,  26  that are standardized and/or interchangeable units and preferably line replaceable units providing easy installation and removal from airframe  12 . As discussed herein, propulsion assemblies  24 ,  26  may be coupled to the nacelle stations of wings  14 ,  16  using rapid connection interfaces to form structural and electrical connections. 
     For example, the structural connections may include high speed fastening elements, cam and hook connections, pin connections, quarter turn latch connections, snap connections, magnetic connections or electromagnetic connections which may also be remotely releasable connections. The electrical connections may include forming communication channels including redundant communication channels or triply redundant communication channels. In addition, the use of line replaceable propulsion units is beneficial in maintenance situations if a fault is discovered with one of the propulsion assemblies  24 ,  26 . In this case, the faulty propulsion assemblies  24 ,  26  can be decoupled from airframe  12  by simple operations and another propulsion assemblies  24 ,  26  can then be attached to airframe  12 . In other embodiments, propulsion assemblies  24 ,  26  may be permanently coupled to wings  14 ,  16  by riveting, bonding and/or other suitable technique. 
     As best seen in  FIG. 1A , each inboard propulsion assembly  24  includes a nacelle  24   a  that houses components including a battery  24   b , an electronic speed controller  24   c , an electronics node  24   d , sensors and other desired electronic equipment. Nacelle  24   a  also supports a propulsion system  24   e  depicted as an electric motor  24   f  and a rotor assembly  24   g . Each outboard propulsion assembly  26  includes a nacelle  26   a  that houses components including a battery  26   b , an electronic speed controller  26   c , gimbal actuators  26   d , an aerosurface actuator  26   e , an electronics node  26   f , sensors and other desired electronic equipment. Nacelle  26   a  also supports a two-axis gimbal  26   g , a propulsion system  26   h  depicted as an electric motor  26   i  and a rotor assembly  26   j  and aerosurfaces  26   k . As the power for each propulsion assembly  24 ,  26  is provided by batteries housed within the respective nacelles, aircraft  10  has a distributed power system for the distributed thrust array. Alternatively or additionally, electrical power may be supplied to the electric motors and/or the batteries disposed with the nacelles from batteries  22   a  carried by airframe  12  via the communications network. In other embodiments, the propulsion assemblies may include internal combustion engines or hydraulic motors. In the illustrated embodiment, aerosurfaces  26   k  of outboard propulsion assembly  26  are active aerosurfaces that serve as horizontal stabilizers, elevators to control the pitch and/or angle of attack of wings  14 ,  16  and/or ailerons to control the roll or bank of aircraft  10  in the biplane orientation of aircraft  10  and serve to enhance hover stability in the VTOL orientation of aircraft  10 . 
     Flight control system  22  communicates via the wired communications network of airframe  12  with the electronics nodes  24   d ,  26   f  of the propulsion assemblies  24 ,  26 . Flight control system  22  receives sensor data from and sends flight command information to the electronics nodes  24   d ,  26   f  such that each propulsion assembly  24 ,  26  may be individually and independently controlled and operated. For example, flight control system  22  is operable to individually and independently control the speed of each propulsion assembly  24 . In addition, flight control system  22  is operable to individually and independently control the speed, the thrust vector and the position of the aerosurfaces of each propulsion assembly  26 . Flight control system  22  may autonomously control some or all aspects of flight operation for aircraft  10 . Flight control system  22  is also operable to communicate with remote systems, such as a ground station via a wireless communications protocol. The remote system may be operable to receive flight data from and provide commands to flight control system  22  to enable remote flight control over some or all aspects of flight operation for aircraft  10 . The autonomous and/or remote operation of aircraft  10  enables aircraft  10  to perform unmanned logistic operations for both military and commercial applications. 
     Each propulsion assembly  24 ,  26  includes a rotor assembly  24   g ,  26   j  that is coupled to an output drive of a respective electrical motor  24   f ,  26   i  that rotates the rotor assembly  24   g ,  26   j  in a rotational plane to generate thrust for aircraft  10 . In the illustrated embodiment, rotor assemblies  24   g ,  26   j  each include two rotor blades having a fixed pitch. In other embodiments, the rotor assemblies could have other numbers of rotor blades including rotor assemblies having three or more rotor blades. Alternatively or additionally, the rotor assemblies could have variable pitch rotor blades with collective and/or cyclic pitch control. Each electrical motor  24   f  is paired with a rotor assembly  24   g  to form a propulsion system  24   e . In the illustrated embodiment, each propulsion system  24   e  is secured to a nacelle  24   a  without a tilting degree of freedom such that propulsion assemblies  24  are non thrust vectoring propulsion assemblies. Each electrical motor  26   i  is paired with a rotor assembly  26   j  to form a propulsion system  26   h . As described herein, each propulsion system  26   h  has a two-axis tilting degree of freedom relative to nacelle  26   a  provided by two-axis gimbal  26   g  such that propulsion assemblies  26  are omnidirectional thrust vectoring propulsion assemblies. In the illustrated embodiment, the maximum angle of the thrust vector may preferably be between about 10 degrees and about 30 degrees, may more preferably be between about 15 degrees and about 25 degrees and may most preferably be about 20 degrees. Notably, using a 20-degree thrust vector yields a lateral component of thrust that is about 34 percent of total thrust. In other embodiments, the inboard and/or the outboard propulsion systems may have a single-axis tilting degree of freedom in which case, the propulsion assemblies could act as longitudinal and/or lateral thrust vectoring propulsion assemblies. 
     Aircraft  10  may operate as a transport aircraft for a payload  30  that is fixed to or selectively attachable to and detachable from airframe  12 . In the illustrated embodiment, payload  30  is selectively couplable between payload stations  18   b ,  20   b  of pylons  18 ,  20  preferably forming a mechanical and electrical connection therebetween. Payload  30  may carry, include or be integral with a variety of modules such as a package delivery module, an air reconnaissance module, a light detection and ranging module, a camera module, an optical targeting module, a laser module, a sensors module, an air-to-ground weapons module, an air-to-air weapons module, a communications module and/or a cargo hook module or the like depending upon the mission being perform by aircraft  10 . The connection between payload stations  18   b ,  20   b  and payload  30  may be a fixed connection that secures payload  30  in a single location relative to airframe  12 . Alternatively, payload  30  may be allowed to rotate and/or translate relative to airframe  12  during ground and/or flight operations. For example, it may be desirable to have payload  30  low to the ground for loading and unloading cargo but more distant from the ground for takeoff and landing. As another example, it may be desirable to change the center of mass of aircraft  10  during certain flight conditions such as moving payload  30  forward relative to airframe  12  during high speed flight in the biplane orientation. Similarly, it may be desirable to adjust the center of mass of aircraft  10  by lowering payload  30  relative to airframe  12  during hover. As illustrated, payload  30  may be selectively coupled to and decoupled from airframe  12  to enable sequential pickup, transportation and delivery of multiple payloads  30  to and from multiple locations. 
     Airframe  12  preferably has remote release capabilities of payload  30 . For example, this feature allows airframe  12  to drop payload  30  or cargo carried by payload  30  at a desired location following transportation. In addition, this feature allows airframe  12  to jettison payload  30  during flight, for example, in the event of an emergency situation such as a propulsion assembly or other system of aircraft  10  becoming compromised. One or more communication channels may be established between payload  30  and airframe  12  when payload  30  is attached therewith such that flight control system  22  may send commands to payload  30  to perform functions. For example, flight control system  22  may operate doors and other systems of a package delivery module; start and stop aerial operations of an air reconnaissance module, a light detection and ranging module, a camera module, an optical targeting module, a laser module or a sensors module; launch missiles from an air-to-ground weapons module or an air-to-air weapons module; and/or deploy and recover items using a cargo hook module. 
     Referring additionally to  FIGS. 2A-2I  in the drawings, a sequential flight-operating scenario of aircraft  10  is depicted. In the illustrated embodiment, payload  30  is attached to airframe  12  and may contain a desired cargo or module. It is noted, however, that payload  30  may be selectively disconnected from airframe  12  such that a single airframe can be operably coupled to and decoupled from numerous payloads for numerous missions over time. In addition, aircraft  10  may perform missions without having a payload  30  attached to airframe  12 . As best seen in  FIG. 2A , aircraft  10  is in a tailsitting position on the ground. When aircraft  10  is ready for a mission, flight control system  22  commences operations to provide flight control to aircraft  10  which may be autonomous flight control, remote flight control or a combination thereof. For example, it may be desirable to utilize remote flight control during certain maneuvers such as takeoff and landing but rely on autonomous flight control during hover, high speed forward flight and/or transitions between wing-borne flight and thrust-borne flight. 
     As best seen in  FIG. 2B , aircraft  10  has performed a vertical takeoff and is engaged in thrust-borne lift with payload  30  lifted into the air. As illustrated, rotor assemblies  24   g  of propulsion assemblies  24  are each rotating in the same horizontal plane forming a first two-dimensional distributed thrust array. Likewise, rotor assemblies  26   j  of propulsion assemblies  26  are each rotating in the same horizontal plane forming a second two-dimensional distributed thrust array. As longitudinal axis  10   a  and lateral axis  10   b  (denoted as the target) are both in a horizontal plane H, normal to the local vertical in the earth&#39;s reference frame, aircraft  10  has a level flight attitude. As discussed herein, flight control system  22  independently controls and operates each propulsion assembly  24 ,  26  including independently controlling speed, thrust vector and aerosurface position. During hover, flight control system  22  may utilize speed control, thrust vectoring and/or aerosurface maneuvers of selected propulsion assemblies  26  for providing hover stability for aircraft  10  and for providing pitch, roll, yaw and translation authority for aircraft  10 . As used herein, the term “hover stability” refers to remaining in one place in the air while maintaining a generally or substantially static flight attitude. 
     For example, flight control system  22  is operable to maintain or change the flight attitude of aircraft  10  by prioritizing the use of flight attitude controls based upon flight attitude control authority as described with reference to  FIG. 3 . As used herein, the term “flight attitude control” refers to mechanisms used to impart change to or maintain the current flight attitude state of aircraft  10 . For example, the flight attitude controls include the use of thrust vectoring, rotor speed, aerosurface position, combinations thereof and the like of one or more of the propulsion assemblies. As used herein, the term “flight attitude control authority” refers to the effectiveness and/or responsiveness of a flight attitude control to impart change to or maintain the current flight attitude state of aircraft  10 . In process  50 , flight control system  22  is configured to determine and maintain an optimal flight attitude state for aircraft  10 . During flight, flight control system  22  performs continuous analysis of the mission parameters and the current flight conditions to determine the optimal flight attitude state for the aircraft, as indicated in block  52 . This analysis determines, for example, whether the aircraft is in the VTOL orientation, the biplane orientation or some transitory orientation therebetween; whether a level flight attitude or an inclined flight attitude is desired; whether a stable flight attitude or a changing flight attitude is desired; and/or whether hover, translation, altitude change and/or direction change is desired and the rate at which such change may be desired. 
     In block  54 , flight control system  22  monitors the current flight attitude state of the aircraft. Data for this analysis may be provided from a sensor suite carried by airframe  12 , propulsion assemblies  24 ,  26  and/or payload  30  including, for example, an attitude and heading reference system (AHRS) with solid-state or microelectromechanical systems (MEMS) gyroscopes, accelerometers and magnetometers. Based upon the optimal flight attitude state for the aircraft and the current flight attitude state of the aircraft, flight control system  22  identifies any deviations between the current flight attitude state and the optimal flight attitude state in block  56 . For example, this process may identify deviations between a current pitch state and an optimal pitch state of the aircraft, deviations between a current roll state and an optimal roll state of the aircraft, deviations between a current yaw state and an optimal yaw state of the aircraft and/or combination thereof. This process may also involve determining a cause of the deviation such as identifying the occurrence of a flight anomaly such as turbulence, a bird strike, a component fault, a one engine inoperable condition or the like. 
     If a deviation is identified, flight control system  22  determines an order for the flight attitude controls of the aircraft based upon the flight attitude control authority of each of the flight attitude controls in the current flight attitude state, in block  58 . This process involves selecting the order in which the possible the flight attitude controls, for example, thrust vectoring, rotor speed and aerosurface position of each of the propulsion assemblies, should be used based upon the expected effectiveness and/or responsiveness of using a specific flight attitude control or a combination of flight attitude controls. The process considers the current state of each flight attitude control, the available envelope of each flight attitude control and the expected aircraft response to each flight attitude control. The process also considers the orientation of the aircraft. For example, in the VTOL orientation, changes in thrust vector and/or rotor speed of selected propulsion assemblies may create a more desired aircraft response than changes in aerosurface position, such as a response of a greater magnitude, a response with a greater rate of change and/or a response with a greater rate of rate of change. Similarly, in the biplane orientation, changes in aerosurface position and/or rotor speed of selected propulsion assemblies may create a more desired aircraft response than changes in thrust vector. 
     In block  60 , flight control system  22  implements the highest order flight attitude control to bias the aircraft from the current flight attitude state to the optimal flight attitude state. This process results in the use of the selected flight attitude control of thrust vectoring, rotor speed, aerosurface position and/or combinations thereof for one or more of the propulsion assemblies. Importantly, in this process, the highest order flight attitude control is not limited to a single type of flight attitude control such as thrust vectoring, rotor speed or aerosurface position. Instead, flight control system  22  is operable to evaluate combinations and/or permutations of thrust vectoring, rotor speed, aerosurface position of the propulsion assemblies to formulate the highest order flight attitude control available to yield the desired aircraft response toward the optimal flight attitude state. For example, the highest order flight attitude control may involve a change in the thrust vector but no change in rotor speed or aerosurface position of some or all of outboard propulsion assemblies  26  along with no change in the operation of any of inboard propulsion assemblies  24 . As another example, the highest order flight attitude control may involve a change in the rotor speed and aerosurface position but no change in the thrust vector of some or all of outboard propulsion assemblies  26  along with a change in the rotor speed of some or all of inboard propulsion assemblies  24 . Based upon these examples, those skilled in the art should understand that a large variety of flight attitude controls are available to aircraft  10  that must be evaluated by flight control system  22  to prioritize the order of use thereof. In block  62 , flight control system  22  senses the aircraft response to the implementation of the highest order flight attitude control to determine whether the aircraft transitioned from the current flight attitude state to the optimal flight attitude state using data, for example, from the attitude and heading reference system. In block  64 , flight control system  22  determines whether the aircraft response was consistent with the expected aircraft response. This process may include determining a cause of any deviation between the actual aircraft response and the expected aircraft response such as identification of a fault in one of the flight attitude controls. For example, this process may determine whether the thrust vectoring, rotor speed or aerosurface positioning capability of a propulsion assembly failed. If the aircraft response is consistent with the expected aircraft response, the process may return to block  52  as flight control system  22  continuously performs this function. If the aircraft response was not consistent with the expected aircraft response, in block  66 , flight control system  22  implements the next highest order flight attitude control to bias the aircraft from the current flight attitude state to the optimal flight attitude state. This process will take into account any faults identified in any flight attitude control to formulate the next highest order flight attitude control. The processes of block  64  and block  66  may be repeated until the optimal flight attitude state is achieved. 
     Returning to the sequential flight-operating scenario of aircraft  10  in  FIGS. 2A-2I , after vertical assent to the desired elevation, aircraft  10  may begin the transition from thrust-borne lift to wing-borne lift. As best seen from the progression of  FIGS. 2B-2E , aircraft  10  is operable to pitch down from the VTOL orientation toward the biplane orientation to enable high speed and/or long range forward flight. As seen in  FIG. 2C , longitudinal axis  10   a  extends out of the horizontal plane H such that aircraft  10  has an inclined flight attitude of about thirty degrees pitch down. As seen in  FIG. 2D , longitudinal axis  10   a  extends out of the horizontal plane H such that aircraft  10  has an inclined flight attitude of about sixty degrees pitch down. Flight control system  22  may achieve this operation through speed control of some or all of propulsion assemblies  24 ,  26 , collective thrust vectoring of propulsion assemblies  26 , collective maneuvers of aerosurfaces  26   k  or any combination thereof. As discussed herein, the specific procedure used for VTOL to biplane transitions may be depend upon the thrust to weight configuration of aircraft  10 . 
     As best seen in  FIG. 2E , rotor assemblies  24   g  of propulsion assemblies  24  are each rotating in the same vertical plane forming a first two-dimensional distributed thrust array. Likewise, rotor assemblies  26   j  of propulsion assemblies  26  are each rotating in the same vertical plane forming a second two-dimensional distributed thrust array. By convention, longitudinal axis  10   a  has been reset to be in the horizontal plane H, which also includes lateral axis  10   b , such that aircraft  10  has a level flight attitude in the biplane orientation. As forward flight with wing-borne lift requires significantly less power then VTOL flight with thrust-borne lift, the operating speed of some or all of the propulsion assemblies  24 ,  26  may be reduced. In certain embodiments, some of the propulsion assemblies  24 ,  26  of aircraft  10  could be shut down during forward flight. In the biplane orientation, the independent control provided by flight control system  22  over each propulsion assembly  24 ,  26  provides pitch, roll and yaw authority using collective or differential thrust vectoring, differential speed control, collective or differential aerosurface maneuvers or any combination thereof. As aircraft  10  approaches its destination, aircraft  10  may begin its transition from wing-borne lift to thrust-borne lift. As best seen from the progression of  FIGS. 2E-2H , aircraft  10  is operable to pitch up from the biplane orientation to the VTOL orientation to enable, for example, a vertical landing operation. As seen in  FIG. 2F , longitudinal axis  10   a  extends out of the horizontal plane H such that aircraft  10  has an inclined flight attitude of about thirty degrees pitch up. As seen in  FIG. 2G , longitudinal axis  10   a  extends out of the horizontal plane H such that aircraft  10  has an inclined flight attitude of about sixty degrees pitch up. Flight control system  22  may achieve this operation through speed control of some or all of propulsion assemblies  24 ,  26 , collective thrust vectoring of propulsion assemblies  26 , collective maneuvers of aerosurfaces  26   k  or any combination thereof. In  FIG. 2H , aircraft  10  has completed the transition from the biplane orientation to the VTOL orientation and, by convention, longitudinal axis  10   a  has been reset to be in the horizontal plane H which also includes lateral axis  10   b  such that aircraft  10  has a level flight attitude in the VTOL orientation. Once aircraft  10  has completed the transition to the VTOL orientation, aircraft  10  may commence its vertical descent to a surface. As best seen in  FIG. 2I , aircraft  10  has landing in a tailsitting orientation at the destination location and may, for example, remotely drop payload  30 . 
     Referring next to  FIGS. 4A-4D , a mission configurable aircraft having multiple thrust array configurations will now be described.  FIG. 4A  depicts the thrust array configuration of aircraft  10  in  FIGS. 1A-1G . Specifically, aircraft  10  includes four outboard propulsion assemblies  26  that form a two-dimensional thrust array of omnidirectional thrust vectoring propulsion assemblies. Propulsion assemblies  26  each include an electronics node depicted as including controllers, sensors and one or more batteries, a two-axis gimbal operated by a pair of actuators and a propulsion system including an electric motor and a rotor assembly. The flight control system  22  is operably associated with propulsion assemblies  26  and is communicably linked to the electronic nodes thereof by a communications network depicted as the arrows between flight control system  22  and propulsion assemblies  26 . Flight control system  22  receives sensor data from and sends commands to propulsion assemblies  26  to enable flight control system  22  to independently control each of propulsion assemblies  26  as discussed herein. 
     An embodiment of an omnidirectional thrust vectoring propulsion assemblies  26  is depicted in  FIG. 5A . Propulsion assembly  26  includes a nacelle  26   a  and a gimbal  26   g  that is coupled to nacelle  26   a . Gimbal  26   g  includes an outer gimbal member  261  and an inner gimbal member  26   m . Outer gimbal member  261  is pivotally coupled to nacelle  26   a  and is operable to tilt about a first axis. Inner gimbal member  26   m  is pivotally coupled to outer gimbal member  261  and is operable to tilt about a second axis that is orthogonal to the first axis. In the illustrated embodiment, actuator  26   n  is coupled between nacelle  26   a  and outer gimbal member  261  such that operation of actuator  26   n  shift linkage  26   o  to tilt outer gimbal member  261  about the first axis relative to nacelle  26   a . Actuator  26   p  is coupled between nacelle  26   a  and inner gimbal member  26   m  such that operation of actuator  26   p  shifts linkage  26   q  to tilt inner gimbal member  26   m  about the second axis relative to outer gimbal member  261  and nacelle  26   a . A propulsion system  26   h  is coupled to and is operable to tilt with gimbal  26   g  about both axes relative to nacelle  26   a . In the illustrated embodiment, the rotor assembly has been removed from propulsion system  26   h  such that only electric motor  26   i  is visible. 
     The operation of an omnidirectional thrust vectoring propulsion assemblies  26  will now be described with reference to  FIGS. 6A-6I . In one example, propulsion assemblies  26  are operable to provide aircraft  10  with control authority to translate in the longitudinal direction, fore-aft along longitudinal axis  10   a  in  FIG. 1E , during a stable hover. The achieve this, flight control system  22  sends commands to operate actuators  26   n  to collectively tilt each of propulsion systems  26   h  in the forward or aft direction while having actuators  26   p  in an unactuated state. In this configuration, propulsion assemblies  26  generate thrust vectors having a forward or aftward directed longitudinal component. In a stable hover, such collective thrust vectoring of propulsion assemblies  26  provides longitudinal control authority to aircraft  10 . As best seen in the comparison of  FIGS. 6A-6C , actuator  26   n  is operated to tilt propulsion system  26   h  longitudinally between a fully forward configuration shown in  FIG. 6A  and a fully aft configuration shown in  FIG. 6C  as well as in an infinite number of positions therebetween including the fully vertical configuration shown in  FIG. 6B . This operation longitudinally shifts the thrust vector of propulsion assembly  26  to enable the longitudinal control authority of aircraft  10 . The maximum longitudinal tilt angle of gimbal  26   g  may preferably be between about 10 degrees and about 30 degrees, may more preferably be between about 15 degrees and about 25 degrees and may most preferably be about 20 degrees. As should be understood by those having ordinary skill in the art, the magnitude of the longitudinal component of the thrust vector is related to the direction of the thrust vector, which is determined by the longitudinal tilt angle of gimbal  26   g.    
     If it is desired to translate aircraft  10  in the lateral direction, right-left along lateral axis  10   b  in  FIG. 1E , flight control system  22  sends commands to operate actuators  26   p  to collectively tilt each of propulsion systems  26   h  in the right or left direction while having actuators  26   n  in an unactuated state. In this configuration, propulsion assemblies  26  generate thrust vectors having a rightward or leftward directed lateral component. In a stable hover, such collective thrust vectoring of propulsion assemblies  26  provides lateral control authority to aircraft  10 . As best seen in the comparison of  FIGS. 6D-6F , actuator  26   p  is operated to tilt propulsion system  26   h  laterally between a fully right configuration shown in  FIG. 6D  and a fully left configuration shown in  FIG. 6F  as well as in an infinite number of positions therebetween including the fully vertical configuration shown in  FIG. 6E . This operation laterally shifts the thrust vector of propulsion assembly  26  to enable the lateral control authority of aircraft  10 . The maximum lateral tilt angle of gimbal  26   g  may preferably be between about 10 degrees and about 30 degrees, may more preferably be between about 15 degrees and about 25 degrees and may most preferably be about 20 degrees. As should be understood by those having ordinary skill in the art, the magnitude of the lateral component of the thrust vector is related to the direction of the thrust vector, which is determined by the lateral tilt angle of gimbal  26   g . Using both the longitudinal and lateral control authority provided by collective thrust vectoring of propulsion assemblies  26 , provides omnidirectional translational control authority for aircraft  10  in a stable hover. If it is desired to translate aircraft  10  in a direction between the longitudinal and lateral directions, such as in a diagonal direction, flight control system  22  sends commands to operate actuators  26   n  to collectively tilt each of propulsion systems  26   h  in the forward or aft direction and sends commands to operate actuators  26   p  to collectively tilt each of propulsion systems  26   h  in the right or left direction. In this configuration, propulsion assemblies  26  generate thrust vectors having a forward or aftward directed longitudinal component and a rightward or leftward directed lateral component. In a stable hover, such collective thrust vectoring of propulsion assemblies  26  provides omnidirectional translational control authority to aircraft  10 . As best seen in the comparison of  FIGS. 6G-6I , actuators  26   n ,  26   p  are operated to tilt propulsion system  26   h  diagonally between a fully aft/right configuration shown in  FIG. 6G  and a fully forward/left configuration shown in  FIG. 6I  as well as in an infinite number of positions therebetween including the fully vertical configuration shown in  FIG. 6H . This operation shifts the thrust vector of propulsion assembly  26  to enable the omnidirectional control authority of aircraft  10 . 
     Referring again to  FIG. 4A , aircraft  10  includes four inboard propulsion assemblies  24  that form a two-dimensional thrust array of non thrust vectoring propulsion assemblies. Propulsion assemblies  24  each include an electronics node depicted as including controllers, sensors and one or more batteries and a propulsion system including an electric motor and a rotor assembly. The flight control system  22  is operably associated with propulsion assemblies  24  and is communicably linked to the electronic nodes thereof by a communications network depicted as the arrows between flight control system  22  and propulsion assemblies  24 . Flight control system  22  receives sensor data from and sends commands to propulsion assemblies  24  to enable flight control system  22  to independently control each of propulsion assemblies  24  as discussed herein. An embodiment of a non thrust vectoring propulsion assemblies  24  is depicted in  FIG. 5B . Propulsion assembly  24  includes a nacelle  24   a  and a propulsion system  24   e  that is coupled to nacelle  24   a . In the illustrated embodiment, the rotor assembly has been removed from propulsion system  24   e  such that only electric motor  24   f  is visible. Thus, the thrust array configuration of aircraft  10  depicted in  FIG. 4A  includes inboard propulsion assemblies  24  having a first thrust type, non thrust vectoring, and outboard propulsion assemblies  26  having a second thrust type, omnidirectional thrust vectoring. 
       FIG. 4B  depicts another embodiment of a thrust array configuration of aircraft  10 . Specifically, aircraft  10  includes four outboard propulsion assemblies  26  that form a two-dimensional thrust array of omnidirectional thrust vectoring propulsion assemblies. Propulsion assemblies  26  each include an electronics node depicted as including controllers, sensors and one or more batteries, a two-axis gimbal operated by a pair of actuators and a propulsion system including an electric motor and a rotor assembly. The flight control system  22  is operably associated with propulsion assemblies  26  and is communicably linked to the electronic nodes thereof by a communications network depicted as the arrows between flight control system  22  and propulsion assemblies  26 . Flight control system  22  receives sensor data from and sends commands to propulsion assemblies  26  to enable flight control system  22  to independently control each of propulsion assemblies  26  as discussed herein. In addition, aircraft  10  includes four inboard propulsion assemblies  36  that form a two-dimensional thrust array of single-axis thrust vectoring propulsion assemblies. Propulsion assemblies  36  each include an electronics node depicted as including controllers, sensors and one or more batteries, a single-axis gimbal operated by an actuator and a propulsion system including an electric motor and a rotor assembly. The flight control system  22  is operably associated with propulsion assemblies  36  and is communicably linked to the electronic nodes thereof by a communications network depicted as the arrows between flight control system  22  and propulsion assemblies  36 . Flight control system  22  receives sensor data from and sends commands to propulsion assemblies  36  to enable flight control system  22  to independently control each of propulsion assemblies  36  as discussed herein. Thus, the thrust array configuration of aircraft  10  depicted in  FIG. 4B  includes inboard propulsion assemblies  36  having a first thrust type, single-axis thrust vectoring, and outboard propulsion assemblies  26  having a second thrust type, omnidirectional thrust vectoring. 
     An embodiment of a single-axis thrust vectoring propulsion assemblies  36  is depicted in  FIG. 5C . Propulsion assembly  36  includes a nacelle  36   a  and a gimbal  36   b  that is pivotally coupled to nacelle  36   a  and is operable to tilt about a single axis. In the illustrated embodiment, actuator  36   c  is coupled between nacelle  36   a  and gimbal  36   b  such that operation of actuator  36   c  shifts linkage  36   d  to tilt gimbal  36   b  about the axis relative to nacelle  36   a . A propulsion system  36   e  is coupled to and is operable to tilt with gimbal  36   b  about the axis relative to nacelle  36   a . In the illustrated embodiment, the rotor assembly has been removed from propulsion system  36   e  such that only electric motor  36   f  is visible. 
     The operation of a single-axis thrust vectoring propulsion assemblies  36  will now be described with reference to  FIGS. 7A-7C . Propulsion assemblies  36  are operable to provide aircraft  10  with control authority to translate in either the longitudinal direction or the lateral direction during a stable hover depending upon the direction of the single-axis of propulsion assemblies  36 . Accordingly, propulsion assemblies  36  may be referred to herein as longitudinal thrust vectoring propulsion assemblies or lateral thrust vectoring propulsion assemblies depending upon their orientation relative to the axes of aircraft  10 . For illustrative purposes, propulsion assemblies  36  will be described as longitudinal thrust vectoring propulsion assemblies in  FIGS. 7A-7C . If it is desired to translate aircraft  10  in the longitudinal direction, fore-aft along longitudinal axis  10   a , flight control system  22  sends commands to operate actuators  36   c  to collectively tilt each of propulsion systems  36   e  in the forward or aft direction. In this configuration, propulsion assemblies  36  generate thrust vectors having a forward or aftward directed longitudinal component. In a stable hover, such collective thrust vectoring of propulsion assemblies  36  provides longitudinal control authority to aircraft  10 . As best seen in the comparison of  FIGS. 7A-7C , actuator  36   c  is operated to tilt propulsion system  36   e  longitudinally between a fully forward configuration shown in  FIG. 7A  and a fully aft configuration shown in  FIG. 7C  as well as in an infinite number of positions therebetween including the fully vertical configuration shown in  FIG. 7B . This operation longitudinally shifts the thrust vector of propulsion assembly  36  to enable the longitudinal control authority of aircraft  10 . The maximum longitudinal tilt angle of gimbal  36   b  may preferably be between about 10 degrees and about 30 degrees, may more preferably be between about 15 degrees and about 25 degrees and may most preferably be about 20 degrees. As should be understood by those having ordinary skill in the art, the magnitude of the longitudinal component of the thrust vector is related to the direction of the thrust vector, which is determined by the longitudinal tilt angle of gimbal  36   b.    
       FIG. 4C  depicts another embodiment of a thrust array configuration of aircraft  10 . Specifically, aircraft  10  includes four outboard propulsion assemblies  36  that form a two-dimensional thrust array of single-axis thrust vectoring propulsion assemblies, either longitudinal thrust vectoring propulsion assemblies or lateral thrust vectoring propulsion assemblies. Propulsion assemblies  36  each include an electronics node depicted as including controllers, sensors and one or more batteries, a single-axis gimbal operated by an actuator and a propulsion system including an electric motor and a rotor assembly. The flight control system  22  is operably associated with propulsion assemblies  36  and is communicably linked to the electronic nodes thereof by a communications network depicted as the arrows between flight control system  22  and propulsion assemblies  36 . Flight control system  22  receives sensor data from and sends commands to propulsion assemblies  36  to enable flight control system  22  to independently control each of propulsion assemblies  36  as discussed herein. In addition, aircraft  10  includes four inboard propulsion assemblies  36  that form a two-dimensional thrust array of single-axis thrust vectoring propulsion assemblies, either longitudinal thrust vectoring propulsion assemblies or lateral thrust vectoring propulsion assemblies, preferably having the alternate thrust type of the outboard propulsion assemblies  36 . Inboard propulsion assemblies  36  each include an electronics node depicted as including controllers, sensors and one or more batteries, a single-axis gimbal operated by an actuator and a propulsion system including an electric motor and a rotor assembly. The flight control system  22  is operably associated with propulsion assemblies  36  and is communicably linked to the electronic nodes thereof by a communications network depicted as the arrows between flight control system  22  and propulsion assemblies  36 . Flight control system  22  receives sensor data from and sends commands to propulsion assemblies  36  to enable flight control system  22  to independently control each of propulsion assemblies  36  as discussed herein. Thus, the thrust array configuration of aircraft  10  depicted in  FIG. 4C  includes inboard propulsion assemblies  36  having a first thrust type, single-axis thrust vectoring in one of the lateral or longitudinal direction, and outboard propulsion assemblies  36  having a second thrust type, single-axis thrust vectoring in the other of the lateral or longitudinal direction. 
       FIG. 4D  depicts another embodiment of a thrust array configuration of aircraft  10 . Specifically, aircraft  10  includes four outboard propulsion assemblies  36  that form a two-dimensional thrust array of single-axis thrust vectoring propulsion assemblies, either longitudinal thrust vectoring propulsion assemblies or lateral thrust vectoring propulsion assemblies. Propulsion assemblies  36  each include an electronics node depicted as including controllers, sensors and one or more batteries, a single-axis gimbal operated by an actuator and a propulsion system including an electric motor and a rotor assembly. The flight control system  22  is operably associated with propulsion assemblies  36  and is communicably linked to the electronic nodes thereof by a communications network depicted as the arrows between flight control system  22  and propulsion assemblies  36 . Flight control system  22  receives sensor data from and sends commands to propulsion assemblies  36  to enable flight control system  22  to independently control each of propulsion assemblies  36  as discussed herein. In addition, aircraft  10  includes four inboard propulsion assemblies  24  that form a two-dimensional thrust array of non thrust vectoring propulsion assemblies. Propulsion assemblies  24  each include an electronics node depicted as including controllers, sensors and one or more batteries and a propulsion system including an electric motor and a rotor assembly. The flight control system  22  is operably associated with propulsion assemblies  24  and is communicably linked to the electronic nodes thereof by a communications network depicted as the arrows between flight control system  22  and propulsion assemblies  24 . Flight control system  22  receives sensor data from and sends commands to propulsion assemblies  24  to enable flight control system  22  to independently control each of propulsion assemblies  24  as discussed herein. Thus, the thrust array configuration of aircraft  10  depicted in  FIG. 4D  includes outboard propulsion assemblies  36  having a first thrust type, single-axis thrust vectoring in one of the lateral or longitudinal direction, and inboard propulsion assemblies  24  having a second thrust type, non thrust vectoring. 
     Even though particular embodiments of the thrust array configuration of aircraft  10  have been depicted and described, those having ordinary skill in the art will recognize that the mission configurable aircraft of the present disclosure has a multitude of additional and/or alternate thrust array configurations. For example, aircraft  10  could have four outboard propulsion assemblies  36  that form a two-dimensional thrust array of single-axis thrust vectoring propulsion assemblies, either longitudinal thrust vectoring propulsion assemblies or lateral thrust vectoring propulsion assemblies and four inboard propulsion assemblies  26  that form a two-dimensional thrust array of omnidirectional thrust vectoring propulsion assemblies. As another alternative, aircraft  10  could have four outboard propulsion assemblies  24  that form a two-dimensional thrust array of non thrust vectoring propulsion assemblies and four inboard propulsion assemblies  26  that form a two-dimensional thrust array of omnidirectional thrust vectoring propulsion assemblies. As still another alternative, aircraft  10  could have four inboard propulsion assemblies  36  that form a two-dimensional thrust array of single-axis thrust vectoring propulsion assemblies, either longitudinal thrust vectoring propulsion assemblies or lateral thrust vectoring propulsion assemblies and four outboard propulsion assemblies  24  that form a two-dimensional thrust array of non thrust vectoring propulsion assemblies. 
     In addition to thrust array configurations having four inboard propulsion assemblies and four outboard propulsion assemblies, mission configurable aircraft  10  may have thrust array configurations with other numbers of propulsion assemblies. For example, as best seen in  FIGS. 8A-8B , aircraft  10  has been configured with four propulsion assemblies  26  that form a two-dimensional distributed thrust array of omnidirectional thrust vectoring propulsion assemblies. In the illustrated embodiment, the airframe  12  is the same airframe described herein including wings  14 ,  16  each having two pylon stations and four nacelle stations. Extending generally perpendicularly between wings  14 ,  16  are two truss structures depicted as pylons  18 ,  20  each of which is coupled between two pylon stations of wings  14 ,  16  and preferably forming mechanical and electrical connections therebetween. Pylons  18 ,  20  each have a nacelle station and a payload station. Wings  14 ,  16  and pylons  18 ,  20  preferably include central passageways operable to contain systems such as flight control systems, energy sources and communication lines that enable the flight control system to communicate with the thrust array of aircraft  10 . In the illustrated embodiment, payload  30  is selectively couplable between the payload stations of pylons  18 ,  20  preferably forming a mechanical and electrical connection therebetween. 
       FIGS. 9A-9B , depict aircraft  10  configured with four outboard propulsion assemblies  26  that form a two-dimensional distributed thrust array of omnidirectional thrust vectoring propulsion assemblies and two inboard propulsion assemblies  24  that form a distributed thrust array of non thrust vectoring propulsion assemblies. In the illustrated embodiment, the airframe  12  is the same airframe described herein including wings  14 ,  16  each having two pylon stations and four nacelle stations. Extending generally perpendicularly between wings  14 ,  16  are two truss structures depicted as pylons  18 ,  20  each of which is coupled between two pylon stations of wings  14 ,  16  and preferably forming mechanical and electrical connections therebetween. Pylons  18 ,  20  each have a nacelle station and a payload station. Wings  14 ,  16  and pylons  18 ,  20  preferably include central passageways operable to contain systems such as flight control systems, energy sources and communication lines that enable the flight control system to communicate with the thrust array of aircraft  10 . In the illustrated embodiment, payload  30  is selectively couplable between the payload stations of pylons  18 ,  20  preferably forming a mechanical and electrical connection therebetween. 
       FIGS. 10A-10B , depict aircraft  10  configured with four outboard propulsion assemblies  26  that form a two-dimensional distributed thrust array of omnidirectional thrust vectoring propulsion assemblies and six inboard propulsion assemblies  24  that form a two-dimensional distributed thrust array of non thrust vectoring propulsion assemblies. In the illustrated embodiment, the airframe  12  is the same airframe described herein including wings  14 ,  16  each having two pylon stations and four nacelle stations. Extending generally perpendicularly between wings  14 ,  16  are two truss structures depicted as pylons  18 ,  20  each of which is coupled between two pylon stations of wings  14 ,  16  and preferably forming mechanical and electrical connections therebetween. Pylons  18 ,  20  each have a nacelle station and a payload station. Wings  14 ,  16  and pylons  18 ,  20  preferably include central passageways operable to contain systems such as flight control systems, energy sources and communication lines that enable the flight control system to communicate with the thrust array of aircraft  10 . In the illustrated embodiment, payload  30  is selectively couplable between the payload stations of pylons  18 ,  20  preferably forming a mechanical and electrical connection therebetween. 
     The versatility of the mission configurable aircraft of the present disclosure enables a single aircraft or fleet of aircraft to become a mission specific suite of aircraft. For example, in a mission scenario of picking up and delivering a payload, aircraft  10  could initially be configured as shown in  FIGS. 8A-8B  with four outboard propulsion assemblies  26  that form a two-dimensional distributed thrust array of omnidirectional thrust vectoring propulsion assemblies located on the outboard nacelle stations of aircraft  10 . This initial thrust array configuration provides aircraft  10  with the necessary thrust capacity and vehicle control to fly from a storage location such as an aircraft hub or hanger or a field location such as within a military theater to the location of the payload to be picked up, without the weight penalty of carrying the inboard propulsion assemblies and the accompanying loss of efficiency. Upon reaching the payload location, aircraft  10  could be reconfigured to the configuration as shown in  FIGS. 10A-10B  keeping the four outboard propulsion assemblies  26  and adding six inboard propulsion assemblies  24  that form a two-dimensional distributed thrust array of non thrust vectoring propulsion assemblies located on the inboard nacelle stations of aircraft  10 . This thrust array configuration provides aircraft  10  with the added thrust capacity to lift and transport a heavy payload  30  to a delivery location. After delivery of payload  30 , aircraft  10  could again be reconfigured to the configuration shown in  FIGS. 8A-8B ,  FIGS. 9A-9B ,  FIGS. 1A-1G , any of  FIGS. 4A-4D  or other desired configuration depending upon the parameters of the next mission. 
     In certain implementations, the mission configurable aircraft of the present disclosure may be part of a man portable aircraft system that is easily transportable and operable for rapid in-situ assembly. Such a man portable aircraft system  100  is depicted in  FIGS. 11A-11D  of the drawings. Man portable aircraft system  100  includes a container  102  formed from a base  102   a  and a cover  102   b  that may be secured together with hinges, latches, locks or other suitable connections. Cover  102   b  and/or base  102   a  may include handles, straps or other means to enable container  102  with aircraft  10  therein to be easily moved or carried. As used herein, the term “man portable” means capable of being carried by one man. As a military term in land warfare, “man portable” means capable of being carried by one man over a long distance without serious degradation to the performance of normal duties. The term “man portable” may be used to qualify items, for example, a man portable item is one designed to be carried as an integral part of individual, crew-served or team equipment of a dismounted soldier in conjunction with assigned duties and/or an item with an upper weight limit of approximately 31 pounds. 
     In the illustrated embodiment, container  102  has an insert  104  disposed within base  102   a  having precut locations that are designed to receive the various component parts of aircraft  10  therein while aircraft  10  is in a disassembled state. Aircraft  10  of man portable aircraft system  100  is preferably operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation, as discussed herein. In the illustrated embodiment, man portable aircraft system  100  includes wing  14  that has first and second pylon stations, first and second inboard nacelle stations and first and second outboard nacelle stations. Man portable aircraft system  100  also includes wing  16  having first and second pylon stations, first and second inboard nacelle stations and first and second outboard nacelle stations. Man portable aircraft system  100  further includes pylon  18  that is couplable between the first pylon stations of wings  14 ,  16  and pylon  20  that is couplable between the second pylon stations of wings  14 ,  16 . Pylons  18 ,  20  each include a payload station and an inboard nacelle station. When assembled, wings  14 ,  16  and pylons  18 ,  20  form the airframe of aircraft  10 . Man portable aircraft system  100  includes six inboard propulsion assemblies  24  which represent the maximum number of inboard propulsion assemblies that may be coupled to the inboard nacelle stations of wings  14 ,  16  and/or pylons  18 ,  20 . Man portable aircraft system  100  also includes four outboard propulsion assemblies  26  which represent the maximum number of outboard propulsion assemblies that may be coupled to the outboard nacelle stations of wings  14 ,  16 . In the illustrated embodiment, a flight control system  20   a  is disposed within pylon  20  and is operable to independently control each of the propulsion assemblies once aircraft  10  is in an assembled state. One or more batteries (not shown) may also be located in pylon  20 , within other airframe members and preferably within each propulsion assembly  24 ,  26 . Man portable aircraft system  100  includes a payload  30  that is operable to be coupled between the payload stations of pylons  18 ,  20 . Payload  30  may carry, include or be integral with a variety of modules such as a package delivery module, an air reconnaissance module, a light detection and ranging module, a camera module, an optical targeting module, a laser module, a sensors module, an air-to-ground weapons module, an air-to-air weapons module, a communications module and/or a cargo hook module or the like depending upon the mission being perform by aircraft  10 . Thus, in certain configurations, aircraft  10  may be operable as a man portable observation platform. 
     Man portable aircraft system  100  includes a computing system  108 , depicted as a tablet computer that is operable as a ground control station for aircraft  10 . Computing system  108  preferably includes non-transitory computer readable storage media including one or more sets of computer instructions or applications that are executable by one or more processors for configuring, programming and/or remotely controlling aircraft  10 . Computing system  108  may be one or more general-purpose computers, special purpose computers or other machines with memory and processing capability. Computing system  108  may include one or more memory storage modules including, but is not limited to, internal storage memory such as random access memory, non-volatile memory such as read only memory, removable memory such as magnetic storage memory, optical storage, solid-state storage memory or other suitable memory storage entity. Computing system  108  may be a microprocessor-based system operable to execute program code in the form of machine-executable instructions. In addition, computing system  108  may be selectively connectable to other computer systems via a proprietary encrypted network, a public encrypted network, the Internet or other suitable communication network that may include both wired and wireless connections. 
     In the illustrated man portable aircraft system  100 , computing system  108  is operable for automated configuration of a mission specific aircraft as described with reference to  FIG. 12 . In process  150 , computing system  108  is configured to receive mission parameters including flight parameters and payload parameters, as indicated in block  152 . The flight parameters may include time requirements, flight speed requirements, elevation requirements, range requirements, endurance requirements, environmental conditions and the like that may be manually input into computing system  108  or received as a digital flight plan from another computing entity over a wired and/or wireless communication channel. The payload parameters may include payload weight requirements, payload functionality requirements, payload coupling and decoupling requirements, payload operational requirements and the like. In block  154 , based upon the mission parameters, computing system  108  configures the airframe including selecting a flight control system, selecting the wings and selecting the pylons. While the illustrated man portable aircraft system  100  included only one set of wings, pylons and a flight control system, other man portable aircraft systems may include additional or different airframe components. For example, other man portable aircraft systems may have wings and pylons of different sizes, wings and pylons made from other materials, wings and pylons having other numbers of or locations for inboard and/or outboard propulsion assemblies, flight control systems having different capabilities and the like. Accordingly, computing system  108  is operable for mission specific aircraft configuration using a wide variety of different airframe components. In the illustrated example of man portable aircraft system  100 , computing system  108  is operable to select wing  14  having first and second pylon stations, first and second inboard nacelle stations and first and second outboard nacelle stations, wing  16  having first and second pylon stations, first and second inboard nacelle stations and first and second outboard nacelle stations, pylon  18  having a payload station, an inboard nacelle station and couplable between the first pylon stations of wings  14 ,  16  and pylon  20  having a payload station, an inboard nacelle station and couplable between the second pylon stations of wings  14 ,  16 . 
     In block  156 , computing system  108  is operable to determine the thrust requirements for aircraft  10  based upon the mission parameters. This process will identify a thrust array capable of the total and/or maximum thrust requirements of aircraft  10  based on upon various expected operating conditions including, for example, the thrust requirement during VTOL operations, the thrust requirement for stable hover in a level flight attitude, the thrust requirement for stable hover in an inclined flight attitude, the thrust requirement for attitude stability during translation and/or other high or unique thrust demand conditions. This process may also identify a thrust array capable of high efficiency for high endurance missions. In block  158 , computing system  108  is operable to configure a two-dimensional distributed thrust array based upon the thrust requirements. This process includes selecting the number, the type and the mounting locations for the propulsion assemblies. As an example, this process may include selecting the number and type of batteries to be contained within the selected propulsion assemblies. As another example, this process may include selecting various rotor blades for the selected propulsion assemblies such as selecting the number of rotor blades, the rotor assembly diameter, the rotor blade twist, the rotor blade chord distribution and the like. As discussed herein, aircraft  10  is a mission configurable aircraft that may be operated with various thrust array configurations such as with only outboard propulsion assembles as depicted in  FIGS. 8A-8B , with outboard propulsion assembles and pylon mounted inboard propulsion assemblies as depicted in  FIGS. 9A-9B , with outboard propulsion assembles and wing mounted inboard propulsion assemblies as depicted in  FIGS. 1A-2I , or with outboard propulsion assembles, wing mounted inboard propulsion assemblies and pylon mounted inboard propulsion assemblies as depicted in  FIGS. 10A-10B , as examples. 
     In the illustrated example of man portable aircraft system  100 , computing system  108  is operable to select a plurality of inboard propulsion assemblies having a first thrust type operable for coupling to the first and second inboard nacelle stations of wings  14 ,  16 , as indicated in block  160 . In addition, computing system  108  is operable to select a plurality of outboard propulsion assemblies having a second thrust type operable for coupling to the first and second outboard nacelle stations of wings  14 ,  16  with the first thrust type being different from the second thrust type, as indicated in block  162 . As examples, based upon the thrust requirements, computing system  108  may select outboard propulsion assemblies that are thrust vectoring propulsion assemblies and inboard propulsion assemblies that are non thrust vectoring propulsion assemblies. Computing system  108  may select outboard propulsion assemblies that are unidirectional thrust vectoring propulsion assemblies and inboard propulsion assemblies that are non thrust vectoring propulsion assemblies. Computing system  108  may select outboard propulsion assemblies that are omnidirectional thrust vectoring propulsion assemblies and inboard propulsion assemblies that are non thrust vectoring propulsion assemblies. Computing system  108  may select outboard propulsion assemblies that are omnidirectional thrust vectoring propulsion assemblies and inboard propulsion assemblies that are unidirectional thrust vectoring propulsion assemblies. Computing system  108  may select inboard propulsion assemblies that are longitudinal thrust vectoring propulsion assemblies and outboard propulsion assemblies that are lateral thrust vectoring propulsion assemblies. Computing system  108  may select outboard propulsion assemblies that are longitudinal thrust vectoring propulsion assemblies and inboard propulsion assemblies that are lateral thrust vectoring propulsion assemblies. 
     Referring additional to  FIG. 13 , computing system  108  not only includes the configuring application  170 , but also includes a programming application  172  and a remote control application  174 . Programming application  172  enables a user to provide a flight plan and mission information to aircraft  10  such that flight control system  22  may engage in autonomous control over aircraft  10 . For example, programming application  172  may communicate with flight control system  22  over a wired or wireless communication channel  176  to provide a flight plan including, for example, a staring point, a trail of waypoints and an ending point such that flight control system  22  may use waypoint navigation during the mission. In addition, programming application  172  may provide one or more tasks to flight control system  22  for aircraft  10  to accomplish during the mission. Following programming, aircraft  10  may operate autonomously responsive to commands generated by flight control system  22 . In the illustrated embodiment, flight control system  22  includes a command module  178  and a monitoring module  180 . It is to be understood by those skilled in the art that these and other modules executed by flight control system  22  may be implemented in a variety of forms including hardware, software, firmware, special purpose processors and combinations thereof. 
     During flight operations, command module  178  sends commands to inboard propulsion assemblies  24  and outboard propulsion assemblies  26  to individually and independently control and operate each propulsion assembly. For example, flight control system  22  is operable to individually and independently control the operating speed, the thrust vector and the aerosurface position of the propulsion assembly. In addition, command module  178  may send commands to payload module  30  such that payload module  30  may accomplish the intended mission. For example, upon reaching an operational location, command module  178  may command payload module  30  to release a package, engage in a surveillance operation, optically mark a target, launch an air-to-ground or air-to-air weapon, deploy a cargo hook or perform another payload module function. Also during flight operation, monitoring module  180  receives feedback from the various elements within inboard propulsion assemblies  24 , outboard propulsion assemblies  26  and payload module  30  such as information from sensors, controllers, actuators and the like. This feedback is processed by monitoring module  180  to supply correction data and other information to command module  178 . Aircraft  10  may utilize additional sensor systems such as altitude sensors, attitude sensors, speed sensors, environmental sensors, fuel supply sensors, temperature sensors and the like that also provide information to monitoring module  180  to further enhance autonomous control capabilities. Some or all of the autonomous control capability of flight control system  22  can be augmented or supplanted by remote control application  174  of computing system  108 . Computing system  108  may communicate with flight control system  22  in real-time over communication link  176 . Computing system  108  preferably includes one or more display devices  182  configured to display information relating to or obtained by one or more aircraft of the present disclosure. Computing system  108  may also include audio output and input devices such as a microphone, speakers and/or an audio port allowing an operator to communicate with, for example, other remote station operators. Display device  182  may also serve as a remote input device  184  in touch screen display implementation, however, other remote input devices, such as a keyboard or joysticks, may alternatively be used to allow an operator to provide control commands to aircraft  10 . Accordingly, aircraft  10  of man portable aircraft system  100  may be operated responsive to remote flight control, autonomous flight control and combinations thereof 
     Returning again to the automated configuration functionality of computing system  108 , once the design parameters of aircraft  10  have been determined by configuring application  170 , man portable aircraft system  100  is operable for rapid in-situ assembly of aircraft  10 . Specifically, the connections between the wings, the pylons, the propulsion assemblies and the payload of man portable aircraft system  100  are each operable for rapid in-situ assembly through the use of high speed fastening elements. For example, referring additionally to  FIGS. 14A-14C  of the drawings, the structural and electrical connections between an inboard nacelle station of a wing and an inboard propulsion assembly will now be described. In the illustrated embodiment, a section of wing  16  include inboard nacelle station  16   e  which is oppositely disposed from pylon station  16   a . Inboard nacelle station  16   e  has a rapid connection interface that includes a pair of upper mechanical connections depicted as cams  16   g ,  16   h , the outer slot portion of each being visible in the figures. Inboard nacelle station  16   e  includes a lower mechanical connection depicted as spring  16   i . Disposed between upper mechanical connections  16   g ,  16   h  and lower mechanical connection  16   i  is a central mechanical connection including an electrical connection depicted as a female mating profile with a plurality of electrical pins  16   j , such as spring biased pins. In the illustrated embodiment, inboard propulsion assembly  24  including a rapid connection interface  24   h  having a pair of upper mechanical connections depicted as hooks  24   i ,  24   j  and a lower mechanical connection depicted as a slotted fastener  24   k . Disposed between upper mechanical connections  24   i ,  24   j  and lower mechanical connection  24   k  is a central mechanical connection including an electrical connection depicted as a male mating profile with a plurality of electrical sockets  241 . 
     In operation, inboard nacelle station  16   e  and inboard propulsion assembly  24  may be coupled and decoupled with simple operations. Specifically, to coupled inboard propulsion assembly  24  with inboard nacelle station  16   e , the distal ends of hooks  24   i ,  24   j  are inserted into the outer slots of cams  16   g ,  16   h  with inboard propulsion assembly  24  tilted relative to inboard nacelle station  16   e  at an angle between about 30 degrees and about 60 degrees. Once hooks  24   i ,  24   j  are inserted into cams  16   g ,  16   h , inboard propulsion assembly  24  is rotated relative to inboard nacelle station  16   e  about cams  16   g ,  16   h  to reduce the angle therebetween, such that hooks  24   i ,  24   j  further penetrate into inboard nacelle station  16   e  providing a self location operation for the other mechanical and electrical connections. Specifically, as the angle between inboard propulsion assembly  24  and inboard nacelle station  16   e  is reduced, the male mating profile enters the female mating profile and pins  16   j  sequentially enter sockets  241  forming a multi-channel parallel interface. Depending upon the number of pin and sockets as well as the desired communication protocol being established therebetween, this electrical connection may provide single communication channels, redundant communication channels or triply redundant communication channels for the transfer of control commands, low power current, high power current and/or other signals between inboard propulsion assembly  24  and inboard nacelle station  16   e  to enable, for example, communication between flight control system  22  and components within inboard propulsion assembly  24  such as battery  24   b , electronic speed controller  24   c , electronics node  24   d , sensors and/or other electronic equipment, as discussed herein. 
     As the angle between inboard propulsion assembly  24  and inboard nacelle station  16   e  is further reduced, a lower mechanical connection between inboard propulsion assembly  24  and inboard nacelle station  16   e  is established with slotted fastener  24   k  and spring  16   i . Once spring  16   i  enters the channel of slotted fastener  24   k , a simple manual or automated quarter turn rotation of slotted fastener  24   k  securely completes the mechanical and electrical connection of inboard propulsion assembly  24  with inboard nacelle station  16   e . In a similar manner, the various connections may be made between pylons  18 ,  20  and pylon stations  14   a ,  14   b ,  16   a ,  16   b , outboard propulsion assemblies  26  and outboard nacelle stations  14   c ,  14   d ,  16   c ,  16   d , payload  30  and payload stations  18   b ,  20   b  as well as the other inboard propulsion assemblies  24  and inboard nacelle stations  14   e ,  14   f ,  16   f ,  18   a ,  20   a , in accordance with the desired configuration of aircraft  10 . 
     Disassembly of aircraft  10  is achieved by reversing the assembly process. Referring again to  FIGS. 14A-14C , from the assembled state, a quarter turn rotation of slotted fastener  24   k  enables separation of slotted fastener  24   k  from spring  16   i . Thereafter, inboard propulsion assembly  24  is rotated relative to inboard nacelle station  16   e  about cams  16   g ,  16   h  to increase the angle therebetween. As the angle between inboard propulsion assembly  24  and inboard nacelle station  16   e  is increased, the electrical connection between inboard propulsion assembly  24  and inboard nacelle station  16   e  is released as pins  16   j  sequentially separate from sockets  241  and the male mating profile separates from the female mating profile. As the angle between inboard propulsion assembly  24  and inboard nacelle station  16   e  is further increased, hooks  24   i ,  24   j  are released from cams  16   g ,  16  completing the mechanical and electrical decoupling of inboard propulsion assembly  24  from inboard nacelle station  16   e . In a similar manner, the connections between pylons  18 ,  20  and pylon stations  14   a ,  14   b ,  16   a ,  16   b , outboard propulsion assemblies  26  and outboard nacelle stations  14   c ,  14   d ,  16   c ,  16   d , payload  30  and payload stations  18   b ,  20   b  as well as the other inboard propulsion assemblies  24  and inboard nacelle stations  14   e ,  14   f ,  16   f ,  18   a ,  20   a  may be decoupled. 
     Referring to  FIGS. 15A-15B  of the drawings, an alternate embodiment of the structural and electrical connections between components of aircraft  10  will now be described. In the illustrated embodiment, a rapid connection interface  200  includes a pair of upper mechanical connections depicted as cams  202 ,  204  and a lower mechanical connection depicted as a female snap element  206 . Disposed between upper mechanical connections  202 ,  204  and lower mechanical connection  206  is a central mechanical connection including an electrical connection depicted as a female mating profile and a plurality of pins  208 . Rapid connection interface  200  may represent the connection interface of an inboard or outboard nacelle station, a pylon station and/or a payload station. In the illustrated embodiment, a rapid connection interface  210  includes a pair of upper mechanical connections depicted as hooks  212 ,  214  and a lower mechanical connection depicted as a male snap element  216 . Disposed between upper mechanical connections  212 ,  214  and lower mechanical connection  216  is a central mechanical connection including an electrical connection depicted as a male mating profile and a plurality of sockets  218 . Rapid connection interface  210  may represent the connection interface of an inboard or outboard propulsion assembly, a pylon and/or a payload. The connection of rapid connection interface  200  with rapid connection interface  210  is substantially similarly to the connection of inboard nacelle station  16   e  with rapid connection interface  24   h  described above with the exception that instead of using a quarter turn operation to securely complete the mechanical and electrical connection, a snapping operation is used to securely complete the mechanical and electrical connection. Likewise, the disassembly of rapid connection interface  200  from rapid connection interface  210  is substantially similarly to the disassembly of inboard nacelle station  16   e  and rapid connection interface  24   h  described above with the exception that instead of using a quarter turn operation to release the lower mechanical connection, an unsnapping operation is used to release the lower mechanical connection. 
     Referring to  FIGS. 16A-16B  of the drawings, another alternate embodiment of the structural and electrical connections between components of aircraft  10  will now be described. In the illustrated embodiment, a rapid connection interface  220  includes a pair of upper mechanical connections depicted as cams  222 ,  224  and a lower connection depicted as a magnetic element  226  such as a permanent magnet, a switchable magnet or an electromagnet. Disposed between upper mechanical connections  222 ,  224  and lower connection  226  is a central mechanical connection including an electrical connection depicted as a female mating profile and a plurality of pins  228 . Rapid connection interface  220  may represent the connection interface of an inboard or outboard nacelle station, a pylon station and/or a payload station. In the illustrated embodiment, a rapid connection interface  230  includes a pair of upper mechanical connections depicted as hooks  232 ,  234  and a lower connection depicted as a magnetic element  236  such as a permanent magnet, a switchable magnet or an electromagnet. Disposed between upper mechanical connections  232 ,  234  and lower connection  236  is a central mechanical connection including an electrical connection depicted as a male mating profile and a plurality of sockets  238 . Rapid connection interface  230  may represent the connection interface of an inboard or outboard propulsion assembly, a pylon and/or a payload. The connection of rapid connection interface  220  with rapid connection interface  230  is substantially similarly to the connection of inboard nacelle station  16   e  with rapid connection interface  24   h  described above with the exception that instead of using a quarter turn operation to securely complete the mechanical and electrical connection, magnetic attraction is used to securely complete the mechanical and electrical connection by, for example, establishing an electrical current to energize an electromagnet. Likewise, the disassembly of rapid connection interface  220  with rapid connection interface  230  is substantially similarly to the disassembly of inboard nacelle station  16   e  from rapid connection interface  24   h  described above with the exception that instead of using a quarter turn operation to release the lower mechanical connection, a mechanical force or discontinuing the electrical current is used to release the lower connection. 
     Referring to  FIGS. 17A-17B  of the drawings, a further alternate embodiment of the structural and electrical connections between components of aircraft  10  will now be described. This embodiment is particularly useful for payload coupling when remote release capabilities are desired. In the illustrated embodiment, a rapid connection interface  240  includes a pair of upper connections depicted as electromagnets  242 ,  244  and a lower connection depicted as an electromagnet  246 . Disposed between upper connections  242 ,  244  and lower connection  246  is an electrical connection depicted as a plurality of pins  248 . Rapid connection interface  240  may represent the connection interface of a payload station. In the illustrated embodiment, a rapid connection interface  250  includes a pair of upper connections depicted as magnets  252 ,  254  and a lower connection depicted as a magnet  256 . Disposed between upper connections  252 ,  254  and lower connection  256  is an electrical connection depicted as a plurality of sockets  258 . Rapid connection interface  250  may represent the connection interface of a payload. The connection of rapid connection interface  240  with rapid connection interface  250  is achieved by aligning upper connections  242 ,  244 , lower connection  246  and electrical connections  248  with upper connections  252 ,  254 , lower connection  256  and electrical connections  258  then engaging a current to create the desired magnetic attraction. In the case of the remotely releasable payload embodiment, when aircraft  10  has transported payload  30  to a desired location, flight control system  22 , either autonomously or responsive to commands send from computing system  108 , may disengage the current to electromagnets  242 ,  244 ,  246  which ends the magnetic attraction to magnets  252 ,  254 ,  256  thus releasing payload  30  from airframe  12  either during flight or after landing aircraft  10 . 
     Referring to  FIGS. 18A-18D  of the drawings, certain unique operations of aircraft  10  will now be described. As discussed herein, aircraft  10  is operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation. In addition, responsive to flight control system  22  independently controlling each propulsion assembly of aircraft  10  including speed control, thrust vectoring and/or aerosurface maneuvers, aircraft  10  is operable to maintain hover stability in level flight attitudes and inclined flight attitudes while also having pitch, roll, yaw and translation authority. In the illustrated embodiment, aircraft  10  has been configured with a two-dimensional distributed thrust array of outboard propulsion assembles  26 , such as aircraft  10  depicted in  FIGS. 8A-8B . Aircraft  10  has a longitudinal axis  10   a  and lateral axis  10   b  which are each located in the horizontal plane H, normal to the local vertical in the earth&#39;s reference frame, when aircraft  10  has a level flight attitude in hover (see  FIG. 2B ). Having hover stability in a level flight attitude is an important characteristic achieved by many VTOL aircraft. With aircraft  10 , such hover stability in a level flight attitude is achieved and/or maintained using the various flight attitude controls as discussed herein. Aircraft  10 , however, is also operable to achieve and/or maintain hover stability in inclined flight attitudes using the various flight attitude controls including speed control, thrust vectoring, aerosurface maneuvers and combinations thereof of the propulsion assemblies. For example, aircraft  10  has in a nonzero pitch down flight attitude in  FIG. 18A  and a nonzero pitch up flight attitude in  FIG. 18B . Angle P represents the pitch angle relative to the horizontal plane H that may be up to about five degrees, between about five degrees and about fifteen degrees, between about fifteen degrees and about twenty-five degrees, between about twenty-five degrees and about thirty-five degrees or other desired angle. For example, once aircraft  10  has transitioned from hover in a level flight attitude to hover in a nonzero pitch flight attitude, aircraft  10  may maintain hover stability in the nonzero pitch flight attitude using collective thrust vectoring of propulsion assemblies  26 , as illustrated in  FIGS. 18A-18B , wherein each of the rotor assemblies is rotating in a plane substantially parallel to the horizontal plane H. Depending upon the magnitude of angle P and the maximum thrust vector angle of propulsion assemblies  26 , the collective thrust vectoring flight attitude control may be augmented with differential speed control and/or aerosurface maneuvers of propulsion assemblies  26 . The ability to maintain hover stability in a nonzero pitch flight attitude may be particularly useful during missions requiring orientation of payload  30  relative to a stationary or moving target on the ground or in the air such as during missions using the light detection and ranging module, the camera module, the optical targeting module, the laser module, the air-to-ground weapons module or the air-to-air weapons module. 
     Aircraft  10  has in a nonzero roll right flight attitude in  FIG. 18C  and a nonzero roll left flight attitude in  FIG. 18D . Angle R represents the roll angle relative to the horizontal plane H that may be up to about five degrees, between about five degrees and about fifteen degrees, between about fifteen degrees and about twenty-five degrees, between about twenty-five degrees and about thirty-five degrees or other desired angle. For example, once aircraft  10  has transitioned from hover in a level flight attitude to hover in a nonzero roll flight attitude, aircraft  10  may maintain hover stability in the nonzero roll flight attitude using collective thrust vectoring of propulsion assemblies  26  as illustrated in  FIGS. 18C-18D , wherein each of the rotor assemblies is rotating in plane substantially parallel to the horizontal plane H. Depending upon the magnitude of angle R and the maximum thrust vector angle of propulsion assemblies  26 , the collective thrust vectoring flight attitude control may be augmented with differential speed control and/or aerosurface maneuvers of propulsion assemblies  26 . The ability to maintain hover stability in a nonzero roll flight attitude may be particularly useful during missions using the package delivery module, the cargo hook module or missions requiring vertical takeoffs and landings on unlevel surfaces and/or autonomous or self-docking of aircraft  10 . 
     While  FIGS. 18A-18B  have described and depicted aircraft  10  maintaining hover stability in a nonzero pitch flight attitude and  FIGS. 18C-18D  have described and depicted aircraft  10  maintaining hover stability in a nonzero roll flight attitude, it should be understood by those having ordinary skill in the art that aircraft  10  is also operable to maintain hover stability when aircraft  10  has a combination of a nonzero pitch flight attitude and a nonzero roll flight attitude using the various flight attitude controls of aircraft  10  including speed control, thrust vectoring, aerosurface maneuvers and combinations thereof of the propulsion assemblies. To maintain hover stability in any inclined flight attitude, the propulsion system of aircraft  10  should preferably be formed as a two-dimensional distributed array of omnidirectional thrust vectoring propulsion assemblies. It is noted, however, that selected hover stability in a single inclined orientation could be achieved with collective thrust vectoring of a two-dimensional distributed array of unidirectional thrust vectoring propulsion assemblies. For example, maintaining hover stability in the nonzero pitch flight attitude may be achieved using collective thrust vectoring of propulsion assemblies having longitudinal thrust vectoring capabilities. Likewise, maintaining hover stability in the nonzero roll flight attitude may be achieved using collective thrust vectoring of propulsion assemblies having lateral thrust vectoring capabilities. 
       FIG. 19A-19B  depict additional capabilities of aircraft  10  that are achievable through flight control system  22  independently controlling each propulsion assembly of aircraft  10  including speed control, thrust vectoring, aerosurface maneuvers and combinations thereof. Aircraft  10  is depicted with payload  30  having an aerial imaging module  260  such as a light detection and ranging module, a camera module, an X-ray module or the like. As illustrated, aerial imaging module  260  is orientated toward a focal point  262  of a stationary object  264  on the ground such as a military target or a structure being inspected. As represented by arrow  266 , flight control system  22  is operable to maintain the orientation of aerial imaging module  260  toward focal point  262  when aircraft  10  is translating in a level flight attitude, such as moving in the depicted fore-aft direction, moving in the lateral direction or moving in any diagonal direction therebetween. This translation is accomplished responsive to controlling the speed, the thrust vector and/or the aerosurface position of each of the propulsion assemblies. 
     Similarly, as represented by arrows  268 ,  270 , flight control system  22  is operable to maintain the orientation of aerial imaging module  260  toward focal point  262  when aircraft  10  is changing altitude by simultaneously adjusting the flight attitude of aircraft  10 . These altitude and attitude changes are accomplished responsive to controlling the speed, the thrust vector and/or the aerosurface position of each of the propulsion assemblies. For example, as aircraft  10  increases altitude from the lower right position to the middle position along arrow  268 , aircraft  10  transitions from a level flight attitude to a pitch down flight attitude with an incline or pitch angle P of between about five degrees and about fifteen degrees. As aircraft  10  further increases altitude from the middle position to the upper right position along arrow  270 , aircraft  10  transitions from a pitch down flight attitude with an incline or pitch angle P of between about five degrees and about fifteen degrees to a pitch down flight attitude with an incline or pitch angle P of between about fifteen degrees and about twenty-five degrees. 
     As represented by arrows  272 ,  274  in  FIG. 19B , flight control system  22  is operable to maintain the orientation of aerial imaging module  260  toward focal point  262  when aircraft  10  is translating in an inclined flight attitude, such as moving in the fore-aft direction, moving in the depicted lateral direction or moving in any diagonal direction therebetween. This translation is accomplished responsive to controlling the speed, the thrust vector and/or the aerosurface position of each of the propulsion assemblies. In one example, aircraft  10  is operable to travel in circles around stationary object  264  while maintaining the orientation of aerial imaging module  260  toward focal point  262  to engage in, for example, phased array aerial imaging and/or three dimensional aerial imaging of ground object  264 . 
     Referring next to  FIGS. 20A-20D , an advantageous use of aircraft  10  during external load operations is depicted. As discussed herein, aircraft  10  is operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation. In addition, in the VTOL orientation, aircraft  10  is operable to maintain hover stability while translating in a level flight attitude or an inclined flight attitude using the various flight attitude controls discussed herein. These unique capabilities of aircraft  10  enable aircraft  10  to lift, carry and transport cargo and/or equipment externally as a sling load. For example, aircraft  10  may engage in external load operations for military campaigns including ship-to-shore movement of equipment during amphibious operations, movement of supplies over a battlefield, vertical replenishment of ships, firepower emplacement and the like without putting pilots at risk. Aircraft  10  provides external load transportation advantages including the rapid movement of heavy or outsized equipment, efficient delivery of emergency supplies directly to the user, the ability to bypass surface obstacles as well as the use of multiple flight routes and/or landing sites, thereby providing improved movement flexibility to accomplish a mission. 
     In  FIG. 20A , aircraft  10  is engaged in aerial crane operations. Specifically, aircraft  10  includes payload  30  having a cargo hook module  280 . In the illustrated embodiment, cargo hook module  280  includes a fixed cargo hook attached to a lower portion of payload  30  when aircraft  10  is in the VTOL orientation. The cargo hook is operable to receive and suspend equipment underneath aircraft  10 . In the illustrated embodiment, a cargo net  282  is being used to support supplies and/or equipment disposed therein. The cargo hook may be opened manually and/or electrically by the ground crew during hookup and release operations while aircraft  10  is on the ground or during flight by attaching or removing, for example, a cargo net apex fitting ring from the cargo hook. During flight, a spring-loaded keeper prevents the fitting ring from slipping off the load beam of the cargo hook. In  FIG. 20A , aircraft  10  is engaging in thrust-borne lift in the VTOL orientation and is ascending, as indicated by arrow  284 , with the external load disposed within cargo net  282  and supported by cargo hook module  280 . In  FIG. 20B , aircraft  10  has transitioned to wing-borne lift in the biplane orientation and is engaged in forward flight, as indicated by arrow  286 . Depending upon the weight of the external load, aircraft  10  may be in a low thrust to weight configuration and may use a low thrust to weight transition procedure for the thrust-borne lift to wing-borne lift transition, as discussed herein. Upon arrival at the destination, aircraft  10  may transition back to the VTOL orientation and lower the external load such that ground crew may manually and/or electrically open the cargo hook to release the external load while aircraft  10  remains in the air or after aircraft  10  has landed. 
       FIG. 20C , depicts an alternate embodiment of aircraft  10  having a payload  30  including a cargo hook module  288 . In the illustrated embodiment, cargo hook module  288  includes a cargo hoisting device operable to raise and lower an external load while aircraft  10  remains in a stable hover. Cargo hook module  288  includes a retractable hoisting cable  290  that is supported by a cargo hook winch system  292  for raising and lowering the cargo hook, as indicated by arrow  294 .  FIG. 20D , depicts another alternate embodiment of aircraft  10  having a payload  30  including a cargo hook module  296 . In the illustrated embodiment, cargo hook module  296  includes a remote or free-swinging cargo hook on a fixed length sling leg assembly cable  298  that is operable to suspend the cargo hook a desired distance from the bottom of aircraft  10 . 
     Referring additionally to  FIGS. 21A-21E and 22A-22E , multiple VTOL to biplane transition procedures selected based upon the thrust to weight configuration of aircraft  10  will now be described. As discussed herein, aircraft  10  is a mission configurable aircraft that is operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a biplane orientation. As aircraft  10  is mission configurable, the particular thrust array that is coupled to a particular airframe may vary depending upon factors including flight parameters such as time requirements, flight speed requirements, elevation requirements, range requirements, endurance requirements, environmental conditions and the like as well as payload parameters such as payload weight requirements, payload functionality requirements, payload coupling and decoupling requirements, payload operational requirements, external loads requirements and the like. During certain portions of a mission, such as after picking up a payload or an external load, aircraft  10  may have a low thrust to weight configuration with a thrust to weight ratio below a first predetermined threshold, while during other portions of a mission, such as after delivery of a payload or releasing the external load, aircraft  10  may have a high thrust to weight configuration with a thrust to weight ratio above a second predetermined threshold. For example, the predetermined threshold for the low thrust to weight configuration of aircraft  10  may be about 1.4 or may be stated as between about 1.1 and about 1.4. The predetermined threshold for the high thrust to weight configuration of aircraft  10  may be about 1.7. 
     As illustrated in  FIGS. 21A-21E , aircraft  10  is in a low thrust to weight configuration and thus preforms a low thrust to weight transition procedure. In the illustrated embodiment, aircraft  10  includes a two-dimensional distributed thrust array of outboard propulsion assemblies  26  coupled to the outboard nacelle stations of the wings, such as the embodiment depicted in  FIGS. 8A-8B . Even through a particular aircraft is depicted in  FIGS. 21A-21E , it should be understood by those having ordinary skill in the art that any of the aircraft of the present disclosure having omnidirectional or longitudinal thrust vectoring propulsion assemblies could also preform the low thrust to weight transition procedure. In this procedure, the initial step involves engaging in a stable hover at a substantially level flight attitude, as illustrated in  FIG. 21A . The next step involves establishing a pitch down flight attitude while maintaining a stable hover, as illustrated in  FIG. 21B . This step is accomplished through the use of the flight attitude controls including rotor speed, thrust vector, aerosurface position and combinations thereof of one or more of the propulsion assemblies  26 . For example, using differential speed control the rotor assemblies  26   j  of the forward propulsion assemblies relative to the aft propulsion assemblies in combination with collective thrust vectoring, the level flight attitude is transitioned to the desired pitch down flight attitude. For example, the pitch down flight attitude may be between about 10 degrees and about 20 degrees relative to the horizontal. Alternatively, the pitch down flight attitude may be between about 20 degrees and about 30 degrees relative to the horizontal. The angle of the thrust vectors should substantially match the pitch down angle relative to the horizontal in order to maintain the stable hover. Optionally, collective tilting of the aerosurfaces  26   k  may be use such that air blowing thereon generates a pitch down moment for aircraft  10  to urge aircraft  10  in the pitch down direction, as illustrated in  FIG. 21B . 
     The next step involves initiating forward flight, as illustrated in  FIG. 21C . Beginning from the stable hover condition, collective increase or decrease in rotor speed will result in an increase or decease in altitude if desired. Collective reduction of the thrust vector angles causes the rotors assemblies  26   j  to tilt forward from the horizontal which in turn changes the direction of the thrust vectors to include not only down components but also aft components. The aft thrust vector components initiate the forward movement of aircraft  10 . As the airspeed increases, the thrust vector angles are collective reduced while simultaneously increasing the pitch down attitude of aircraft  10  until the thrust vectors and the wings are substantially horizontal, as seen in the progression of  FIGS. 21C-21E . By reducing the angle of attack of the wings in pitch down configuration prior to initiating forward flight, wing-borne lift can be generated at a lower forward airspeed thus enabling the low thrust to weight transitions from VTOL orientation to biplane orientation of aircraft  10 . 
     As illustrated in  FIGS. 22A-22E , aircraft  10  is in a high thrust to weight configuration and thus preforms a high thrust to weight transition procedure. In this procedure, the initial step may involve engaging in a stable hover at a substantially level flight attitude, as illustrated in  FIG. 22A . From this condition, collective increase or decrease in rotor speed will result in an increase or decease in altitude if desired. The next step involves engaging in collective thrust vectoring of propulsion assemblies  26  to initiate forward flight, as illustrated in  FIG. 22B . The next step involves maintaining the thrust vector angles and increasing the pitch down attitude of aircraft  10  until the thrust vectors are substantially horizontal, as illustrated in  FIG. 22C . Optionally, collective tilting of the aerosurfaces  26   k  may be use such that air blowing thereon generates a pitch down moment for aircraft  10  to urge aircraft  10  in the pitch down direction, as illustrated in  FIG. 22C . This is followed by collectively reducing the thrust vector angles and increasing the pitch down attitude while maintaining the thrust vectors substantially horizontal until the wings are also substantially horizontal, as seen in the progression of  FIGS. 22C-22E . In the high thrust to weight configuration of aircraft  10 , the command authority provided by collective thrust vectoring may provide the most efficient response when transitioning from VTOL orientation to biplane orientation is desired. 
     The foregoing description of embodiments of the disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosure. The embodiments were chosen and described in order to explain the principals of the disclosure and its practical application to enable one skilled in the art to utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the embodiments without departing from the scope of the present disclosure. Such modifications and combinations of the illustrative embodiments as well as other embodiments will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.