Abstract:
A double-deck airplane that facilitates passenger embarking/disembarking and cargo loading/unloading operations in order to maximize the number of flight missions carried out in a given time. The floors of its upper and lower decks are planar surfaces extending continuously inside the fuselage in at least the inner space of the fuselage intended for the payload; the lower deck is located at a height from the ground that allows carrying out passenger embarking/disembarking via equipment incorporated in the airplane without any external airport ground equipment; passenger and/or cargo compartments are distributed on the upper and/or lower decks; and the lifting structure is disposed in the airplane in a manner that none of its components crosses the upper and lower decks.

Description:
This application claims priority to EP 13382527.3 filed 18 Dec. 2013, the entire contents of which is hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     This technology herein relates to commercial airplanes and more particularly to double-deck airplanes for transporting passengers and/or cargo. 
     BACKGROUND OF THE INVENTION 
     Commercial airlines are continuously demanding airplanes that maximize revenue while reducing operational costs. It is likewise demanded that new airplanes comply with the current and future environmental standards. 
     This demand requires airplanes having low fuel consumption and being configured so as to facilitate efficient passenger embarking/disembarking and cargo loading/unloading operations in order to maximize the number of flight missions carried out in a given time. It is also required that aircraft design allows optimum use of internal volumes for a wide range of different airlines that have different requirements in terms of passengers, baggage and freight capacity. 
     Double-deck airplanes are one of the available options to meet that demand because in classical commercial aircraft configurations with an upper deck dedicated almost exclusively to carrying passengers and a lower hold only dedicated to cargo transportation it is not possible, for example, to use the empty cargo space to carry more passengers on a flight with no or little cargo being transported. 
     US 2004/0075025 describes an aircraft comprising an upper deck, a multipurpose lower deck and a wing structure passing through the lower deck area which leads to having separated front and aft portions on the lower deck. Thus the flexibility of use and the volume of the lower deck are limited by the presence of the wing. 
     US 2013/0099053 describes a double-deck airplane with a mid-wing. The airplane is configured with an upper compartment for passengers and a lower compartment with a frontal portion for passengers, a rear portion for cargo and an intermediate portion for the wing box and other facilities. This configuration is determined by the use of high bypass ratio turbofan engines or open rotor engines mounted on the underside of the wing and has the drawback that the wing box occupies a useful space for passengers or cargo inside the fuselage. 
     The technology herein is directed to solving all the problems mentioned above. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an airplane that facilitates passenger embarking/disembarking and cargo loading/unloading operations in order to maximize the number of flight missions carried out in a given time. 
     It is another object of the present invention to provide an airplane whose internal space can be distributed in a flexible manner between passenger and cargo compartments. 
     These and other objects are met by a double-deck airplane with the following features:
         the floors of the upper and lower decks are planar surfaces extending continuously inside the fuselage in at least the inner space of the fuselage intended for the payload;   the lower deck is located at a height from the ground that allows carrying out passenger embarking/disembarking autonomously without any specific airport ground equipment;   passenger and/or cargo compartments are distributed throughout the upper and/or lower decks;   the lifting structure is disposed in the airplane in a manner that none of its components crosses the upper and lower decks.       

     In an embodiment the passenger and cargo compartments are separated by at least a movable partition wall. Advantageously the airplane comprises one passenger compartment and a cargo compartment whose dimensions can be adjusted to the airline needs by moving the partition wall. Foldable seats installed on guides in a sliding manner may be used to increase/reduce the dimension of a passenger compartment. 
     In an embodiment the airplane is provided with at least lower doors accessible from ground and upper doors accessible from jetways for speeding the passenger embarking/disembarking and cargo loading/unloading operations. 
     In an embodiment the lower access doors to a passenger compartment are doors incorporating airstairs so that they can be used as passenger embarking/disembarking stairs from/to the ground. 
     The airplane of the invention can have different lifting structures, propulsion systems and landing gear arrangements. 
     The lifting structures in particular are based on a low wing or a high wing disposed so as not to interfere with the passenger and/or cargo compartments and a suitable empennage. 
     Other characteristics and advantages of the present invention will be clear from the following detailed description of embodiments illustrative of its object in relation to the attached figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view illustrating the basic interior configuration of an exemplary airplane of the invention. 
         FIGS. 2 a , 2 b , 2 c , 2 d    are schematic sectional views illustrating four possible distributions of space dedicated to passengers and cargo in exemplary airplanes of the invention. 
         FIGS. 3 a  and 3 b    are schematic sectional views illustrating, respectively, a space dedicated to passengers only and the same space dedicated to passengers and cargo using foldable seats for passengers. 
         FIG. 4 ,  FIG. 5  and  FIG. 6  are perspective, frontal and plan schematic views of a first embodiment of the airplane of the invention. 
         FIG. 7  is a schematic sectional view of the first embodiment of the airplane of the invention. 
         FIG. 8  is a perspective view of the first embodiment illustrating the aircraft access from the upper front door by mean of a jetway. 
         FIG. 9  is a perspective view of the first embodiment illustrating the aircraft access from the upper doors by mean of boarding stairs as part of the airport ground equipment. 
         FIG. 10  is a perspective view of the first embodiment illustrating the aircraft access from lower doors with airstairs. 
         FIG. 11 ,  FIG. 12 ,  FIG. 13  and  FIG. 14  are perspective, frontal, plan and side schematic views of a second embodiment of the airplane of the invention. 
         FIG. 15  is a perspective view of a third embodiment of the airplane of the invention. 
         FIG. 16  and  FIG. 17  are perspective and side schematic views of a fourth embodiment of the airplane of the invention. 
         FIG. 18  is a perspective front view of an alternative arrangement of the fourth embodiment of the airplane of the invention with a front cargo door located in the nose area. 
         FIG. 19  is a perspective rear view of an alternative arrangement of the fourth embodiment of the airplane of the invention with a cargo door located in the rear end area. 
         FIGS. 20   a,    20   b,    20   c  are side views of the fourth embodiment showing possible cargo and passenger arrangements and the impact on the overall passenger capacity and cargo volume. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As illustrated in  FIG. 1 , the basic features of the interior configuration of an exemplary double-deck airplane of the invention are that:
         the floors  31 ,  33  of upper and lower decks  41 ,  43  are flat surfaces that extend continuously in at least the inner space of the fuselage  13  intended for the payload which is delimited by the front end sections  36 ,  35  and the rear end section  37 ;   the lower floor  33  is located at a height close enough to the ground so that at least in part the passenger embarking/disembarking can take place autonomously without any specific airport ground equipment, for instance by using air-stairs incorporated in the doors that can rotate up and down;   at least a partition wall  42  on the upper deck  41  or on the lower deck  43  is used to separate passengers and cargo compartments  64 ,  63  (delimited by dashed lines).       

     In the particular configuration shown in  FIG. 1 , the passenger compartment  64  occupies the space comprised between the front end section  36  and the rear end section  37  in the upper deck  41  and the space comprised between the partition wall  42  and the rear end section  37  in the lower deck  43 . The cargo compartment  63  occupies the space comprised between the front end section  35  and the partition wall  42  in the lower deck  43 . On the other hand, the upper floor  31  extends beyond the front end section  36  delimiting a space for the cockpit while the lower floor  33  is limited by front end section  35  and the rear end section  37 . 
     The partition wall  42  can be located in different positions along the fuselage axis to modify the space allocated to the passengers and cargo compartments  64 ,  63 . 
     This configuration provides maximum flexibility for airlines to manage the payload space since the upper and lower decks  41 ,  43  with flat floors  31 ,  33  may be used, in whole or in part, as passenger or cargo compartments. Cargo can be carried on the lower deck  43  but also on the upper deck  41  by means of the same procedures used in certain modified versions of known commercial aircraft which are provided with a large cargo door giving access to the upper deck and can carry palletized or bulk cargo loaded by special ground equipment. 
     The flexibility of the split between passengers and cargo compartments  64 ,  63  is ensured by the partition wall  42  that can be installed at different positions along the fuselage axis depending on the airline&#39;s needs. As the floors  31 ,  33  are flat and continuous there is a total flexibility from the front end sections  36 ,  35  to the rear end section  37 . In this respect  FIG. 2 a    shows an airplane configured with only a passenger compartment  64  and  FIGS. 2 b -2 d    show airplanes configured with a passenger compartment  64  in the upper deck  41  and in part of the lower deck  43  and a cargo compartment  63  in the lower deck  43  of different dimensions. 
     This flexibility can be used in different operating scenarios:
         A first scenario is to have each airline choosing individually its own cabin layout with a given distribution of passenger and cargo compartments  64 ,  63  by choosing a specific position for the partition wall  42 . Once configured, this cabin layout remains the same for the whole life of the aircraft unless an important overhaul is performed on the airplane including a change of the cabin arrangement.   A second scenario can be to modify the airplane arrangement overnight at the airline base by moving the partition wall  42  and by adding or removing passenger seats into/from the passenger compartment  64  of the aircraft.   In a third scenario, the airlines benefit from this flexibility between every flight. As shown on  FIGS. 3 a    and  3   b,  the seats  65  are not moved in or out of the cabin when the passengers compartment  64  is increased or reduced but remain in the cabin whatever the cabin configuration. The partition wall  42  (a sliding wall or a net) can be moved to the right position by the cabin crew and the affected seats  65  are flattened or un-flattened depending on the cabin layout. When more cargo space is needed the affected seats are flat folded, sliding on guides  66  embedded in the floor and stacked next to each other. The partition wall  42  is then moved next to the folded seats  67  to free some space for the cargo compartment  63 . When less cargo space is needed, the operations above are reversed.       

     Another basic feature of the exemplary double-deck airplane is that the bottom part of the fuselage  13  is very close to the ground and its rear part has a proper inclination angle A (see  FIG. 1 ) to avoid a tail-strike during the takeoff or landing. The shorter length of the double deck fuselage of the exemplary airplane compared to a single deck aircraft of the same passenger capacity facilitates having the bottom part of the fuselage  13  very close to the ground while still attaining a good rotation angle at take-off or landing. 
     As in known configurations of double-deck airplanes, the fuselage  13  may be of ovoid or of double-bubble type cross section. 
     A first example embodiment of the invention (see  FIG. 4 ,  FIG. 5  and  FIG. 6 ) has the following features:
         Having a lifting structure formed by a low wing  15  (its central box being located under the lower floor  33 ) and a T-shaped empennage  17 .   Having a propulsion system formed by engines  19  mounted at the rear part of the fuselage  13 .   Having a nose landing gear  21  under the forward fuselage and a main landing gear  23  mounted on the underside of the fuselage  13  that is provided with fairings  26  to house the main landing gear  23 .       

       FIG. 7  shows a possible arrangement of the space provided for the payload in this embodiment. The upper deck  41  houses the upper part of the passenger compartment  64  with two access doors  51 ,  53  on each side and the lower deck  43  houses a forward cargo compartment  63  with an access door  55  on one side and the lower part of the passenger compartment  64  with two access doors  57 ,  59  on each side. The configuration shown in  FIG. 7  also includes an interior stairway  69  communicating the upper and lower part of the passenger compartment  64 . 
     This configuration allows passenger embarking/disembarking operations to/from the upper part of the passenger compartment  64  to be made through the upper doors  51 ,  53  using airport ground equipment such as a jetway  46  for door  51  (see  FIG. 8 ) or boarding stairs  48  for doors  51 ,  53  (see  FIG. 9 ). 
     The passenger embarking/disembarking operations to/from the lower part of the passenger compartment  64  can be done through the lower doors  57 ,  59  using airport ground equipment or autonomously including airstairs in the lower doors (see  FIG. 10 ). 
     The internal stairway  69  allows transfer of passengers from the upper deck  41  to the lower deck  43  and vice versa during embarking/disembarking operations. It is, then, possible to use only upper doors  51 ,  53  or only lower doors  57 ,  59  for the passengers embarking disembarking procedure of the full aircraft. When using lower doors only  51 ,  53 , it is possible to have fully autonomous embarking/disembarking process without using any airport equipment (boarding stairs, jetways) as the lower doors are equipped with integrated airstairs. 
     On the other hand, the simultaneous use of upper and lower doors  51 ,  53 ;  57 ,  59  allow fast embarking/disembarking process. 
     A second example embodiment of the invention (see  FIG. 11 ,  FIG. 12 ,  FIG. 13  and  FIG. 14 ) has the following features:
         Having a lifting structure comprising a low wing  15  (its central box being located under the lower deck  33 ) and an empennage formed by a vertical tail plane  18  and a horizontal tail plane  28 .   Having a propulsion system comprising two engines  19  mounted over the low wing  15  on each side of the fuselage  13  in a forward location with respect to the low wing  15 .   Having a nose landing gear  21  and a main landing gear  23  mounted on the underside of the low wing  25  that is provided with fairings  26  arranged in its rear part to house the main landing gear  23 .       

     The interior space of the fuselage  13  may be arranged in a manner very similar to that shown in  FIG. 7  except for the location of the access doors to the upper and lower decks  41 ,  43 . 
     A third embodiment of the invention (see  FIG. 15 ) is similar to the second embodiment with the exception that the two engines  19  are mounted over the low wing  15  on each side of the fuselage  13  in an aft location with respect to the wing and in that the empennage is a T-shaped empennage  17 . 
     A fourth example embodiment of the invention (see  FIG. 16  and  FIG. 17 ) has the following features:
         Having a lifting structure comprising a high wing  61  (its central box being located above and not protruding the upper deck  41 ) and a T-shaped empennage  17 .   Having a propulsion system comprising two engines  19  mounted under the high wing  61  on each side of the fuselage  13 .   Having a nose landing gear  21  and a main landing gear  23  mounted on the underside of the fuselage  13  that is provided with fairings  26  to house the main landing gear  23 .       

       FIG. 18  shows an alternative arrangement of the fourth embodiment with a portion  60  of the frontal fuselage configured as an access door to the forward lower deck  43  when this is used as a cargo compartment. This frontal door is an alternative arrangement to the side cargo access door  55  as shown in  FIG. 7 . As a second alternative,  FIG. 19  shows a portion  62  of the rear fuselage configured as a door in the aft part of the fuselage that can be used to load and unload the cargo when the cargo compartment  63  is located at the rear of the fuselage. 
     Finally  FIG. 20  shows three different cabin arrangements of the passenger and cargo compartments  64 ,  63  on the fourth embodiment illustrating its impact on the passenger capacity and cargo volume. 
     Overall the example airplanes of the invention can reduce the operational costs of the transportation of passengers and cargo by virtue of a greater payload capacity for a given fuselage length as the space inside the fuselage  13  intended for the payload is maximized. For the same reason the wetted area is reduced compared to a conventional single deck aircraft of same capacity. This enables an improved aerodynamic efficiency and a reduction of the fuel burn in flight. Finally the flexible distribution between passengers and cargo as well as its capacity to reduce the time used in the passenger embarking/disembarking and cargo loading/unloading operations is also an mean to improve the economic efficiency of the aircraft. 
     Although the present invention has been described in connection with various embodiments, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made, and are within the scope of the invention.