US3424411A

US3424411A - Door assembly for cargo aircraft

Info

Publication number: US3424411A
Application number: US662508A
Authority: US
Inventors: Willard S Blunschi Sr; Augustus H Chapman
Original assignee: Lockheed Aircraft Corp
Current assignee: Lockheed Corp
Priority date: 1967-08-22
Filing date: 1967-08-22
Publication date: 1969-01-28
Anticipated expiration: 1986-01-28

Description

Jan. 28, 969 w. s. BLUNSCHI, SR... ETAL 4,

DOOR ASSEMBLY FOR CARGO AIRCRAFT Filed Aug. 22, 1967 Sheet INVENTORS YUGUSTUS H.CHAPMAN I Agent WILLARD S. BLUNSCHI,$R.

Jan. 28, 1969 V w. s. BLUN'SCHI, sR., ETAL 3,

DOOR ASSEMBLY FOR CARGO AIRCRAFT Filed Aug. 22,1967

Sheet

2 or 2 INVENTORS. WILLARD S. BLUNSCH|,SR. AUGUSTUS H.CHAPMAN Agent United States Patent M 10 Claims Int. Cl. B240: 1/22; B24d 9/00; Ef 17/00 ABSTRACT OF THE DISCLGSURE A method of opening the aft fuselage of an aircraft for airdrop without exposing doors to the airstream and the attendant problems of flutter and sonic vibrations is provided by a center opening door mounted on a translating roller and track assembly. The forward end of this door is hinged to the bottom edge of the pressure door allowing it to be raised up and aft by the actuation of the pressure door during its opening cycle, and has side doors which fold inboard on top of the center door prior to the opening cycle. The folding side doors reduce the overall door width providing the clearance necessary to raise the door into the fuselage structure and at the same time leave the exterior of the airplane uncluttered.

This invention relates generally to doors for transport type aircraft facilitating the movement of goods and cargo on and off the aircraft, and more particularly to a cargo door assembly especially adapted for efiicient aerial delivery or airdrop operations without sacrificing some of the aerodynamic parameters and the size of the opening necessary for efficient ground operations with respect to on and off cargo loading.

In loading and unloading of cargo on and off aircraft, maximum efliciency, at least in the larger aircraft, has been obtained through end loading, i.e., loading (or unloading) through the end, more often the aft end or tail of the fuselage, eliminating turning and manuevering operations otherwise necessary. Such end loading, however, creates special problems in the design and construction of the fuselage adjacent the opening and also in the design, construction and operation of the closures or doors for these openings.

For ground loading and unloading, a simple hinged door or doors that swing outwardly have been employed in order to gain unobstructed access to the interior of the aircraft at or near its maximum transverse dimension. As the size of aircraft increases, this becomes more difficult since the open door must be properly supported to withstand not only its own weight, but also air loads and winds to which it may be subjected so as not to become damaged or distorted, preventing its subsequent closing. This has been satisfied largely through the use of doors that consist of multiple sections, such as the so-called clam shells or the like, it being usually preferred to increase the complexity of the door assembly and its operation rather than add Weight to the aircraft by reinforcement to the door and the adjacent supporting structure.

When greater performance is required of the aircraft as is presently the case and airdrop of cargo is included, these problems become compunded. Large openings make it necessary to reinforce the adjacent stationary structure to assure its integrity during the airdrop operation, and hence add weight to the aircraft. Where a solution has been sought through a multiple section door assembly, the extreme contour condition of the fuselage end has produced relatively complex structures and/ or mechanisms to synchronize the movement of the door sections.

3,424,41 1 Patented Jan. 28, 1969 This introduces maintenance problems and a question of reliability inasmuch as such coordinated operations of bulky and complex structures are prone to malfunction.

The present invention recognizes the above and other problems in the construction and operation of end loading cargo doors in modern aircraft and proposes a solution through the design and fabrication of an uncomplicated and yet efiicient door assembly. This door assembly, although not limited to, is particularly suited for aircraft with aerial delivery requirements in that it is so organized and arranged on the aircraft as to remove a bare minimum of support from the component in which it is located while presenting an opening large enough to satisfy the maximum airdrop requirement of the aircraft. At the same time, the open door is disposed totally within the airstream, i.e., the effective contour of the aircraft, so that it does not adversely alfect the aerodynamic efficiency thereof nor does it obstruct the opening or unduly reduce its size. This door assembly is capable of exposing the maximum cross-sectional dimension of the cargo compartment most important in ground on and off loading.

Moreover, the construction of the door assembly herein proposed lends itself to the stringent weight tolerance of aircraft, being designed and adapted to form in effect an integral part of the airframe when closed. The mounting of the door assembly is such that it is integrated with associated parts and structure of the aircraft to minimize the accessory means incidental to its actuation and/or movement.

More specifically, this door assembly comprises a main or center section with an appendage or secondary section hinged at and along each side. When disposed in one extreme position, these door sections coact to form a continuation of the wall of the aircraft defining the cargo compartment and completely fill the access opening therein. In the other extreme position, the side sections are folded or swung inwardly of the aircraft with their surfaces adjacent the inner surface of the center section, and the folded assembly of door sections elevated and held in position at the ceiling of the compartment.

This operation of the door assembly in moving to and from its extreme positions is integrated with the movement of the sealed aft door employed to maintain the hold or cargo compartment pressurized, i.e., under a preestablished constant air pressure, during normal operation of the aircraft. Thus, the center section of the door assembly is pivotally linked to the free end of the pressure door so that when the pressure door is swung to the open position the door assembly is concurrently lifted out of the access opening and moved linearly aft on a sliding pivot at its opposite end.

With the above and other objects in view as will be apparent, this invention consists in the construction, combination and arrangement of parts all as hereinafter more fully described, claimed and illustrated in the accompanying drawings wherein:

FIGURE 1 is a side elevation of the aft end portion of a typical cargo aircraft constructed to include a door assembly in accordance with the teachings of this invention shown in one extreme position, viz the closed position;

FIGURE 2 is a section taken along the line 22 of FIGURE 1 to show primarily the interconnection of the several sections comprising the door assembly and the actuating means for the movement of the side sections to the open position, the open position of the side sections constituting the initial stage in opening the door assembly being indicated in phantom lines;

FIGURE 3 is a view like FIGURE 1 showing the door assembly in the other extreme position, viz the open position;

FIGURE 4 is a section taken along the line 4-4 of FIGURE 3;

FIGURE 5 is a section taken along the line 55 of FIGURE 1 to show the track and roller assemby constituting a sliding pivot by which the door assembly is made to translate linearly at the same time it is being opened and closed; and

FIGURE 6 is a diagram of the power actuating system for the operation of the door assembly to show schematically the sequential operation thereof.

Referring more particularly to the drawings, 10 designates the aft end portion of a typical cargo aircraft, i.e., the fuselage, which terminates in an empennage section 11. Internally of the aircraft or fuselage 10 is a compartment 12 constituting the hold, adapted to receive and store cargo for which the aircraft is designed to transport.

In order to facilitate access to the compartment 12 for the on and off loading of the cargo, an opening 13 is provided in the fuselage 10 on the under side thereof. Adjacent its forward end, the opening is defined by a ramp 14 which extends the full width thereof, being hinged as at 15 to the fuselage 10. Thus, the ramp 14 is adapted to swing about the fuselage to and from extreme positions where its outer surface forms a smooth and unbroken continuation of the external surface of the fuselage 10 and a lowered position or positions compatible with offloading of cargo either in airdrop or ground operation. In the latter case, the outer free end of the ramp 14 contacts the ground or other surface to facilitate the passage of cargo from surface to ramp and into or out of the compartment 12. Conventional locking means (not shown) is employed to secure the ramp 14 in its several positions.

Associated with the opening 13 is a door assembly 16 formed by a center section 17 and identical side sections 18. Each side section abuts the fuselage 10 adjacent its upper side and ends with the associated external surfaces thereof disposed in a common plane and adapted to swing on a pivot 18' in an upward direction of the aircraft toward the center section 17. Suitable actuating means 19 is provided for such movement of each side section 18 being pivotally connected in appropriate manner at opposite ends to the center section 17 and its side section 18.

The center section 17 is pivotally connected to the fuselage adjacent the rear extremity thereof with its longitudinal side edges adaped to coact with the corresponding edges of the side sections 18 to form an uninterrupted continuation of the fuselage 10 when in the closed position. Thus, a sliding hinge 20 is effected by means of and through a projecting bracket 21 on the fuselage 10 in which a pair of adjacent rollers 22 are carried. A fixed track 23 carried by the center section 17 is adapted to receive and mount each roller 22 for relatively free and unrestricted linear movement thereof.

At its aft end, the center section 17 is formed with a generally triangular and transversely curved terminus 24 so as to conform to the tapered fuselage 10. With its apex aft, the forward side of this triangle 24 is adapted to abut the aft end of each side section 18 whereby the aerodynamically clean fuselage lines are preserved during normal flight of the aircraft with the door assembly 16 closed. The door assembly 16 is secured in this position by means of one or more latches 25 operative between each side section 18 and the associated fuselage 10 which may be constructed following known practice. Where multiple such latches 25 are employed on each side section 18, they are made to operate in unison as are the latches 25 of both side sections 18 as will hereinafter become more apparent.

At its forward end, the center section 17 is provided with a mount in the form of a pin joint 26 adapted to pivotally connect the outer end of an actuating link 27 pivotally secured at its opposite end to fixed structure of the fuselage 10. As shown, the link 27 is the pressure door which closes and seals the aft end of the storage compartment 12 to thereby maintain the compartment at constant pressure. In this case, a conventional power actuator 28 connected between the link or door 27 and fixed aircraft structures serves to swing the door 27 to and from its extreme positions.

Referring specifically to FIGURE 6, when it is desired to open this door assembly 16 a control valve 29 located in a line 30 from the main hydraulic system of the aircraft is opened, admitting fluid pressure to the latch 0r latches 25 associated with each side door section 18. The several latches 25 are thereby simultaneously released and the fluid pressure is admitted to the side door actuators 19 causing both side sections 18 to fold concurrently onto the center section 17. Thereafter, the fiuid pressure is admitted to the pressure door actuator 28 causing the pressure door 27 to raise and the door assembly 16 to open with it. The door assembly 16 is thereby located adjacent the overhead structure defining the interior of the fuselage 10 to allow for maximum clearance.

At the same time, in swinging upward the door assembly 16 is translated aft sliding on the tracks 23 in engagement with the rollers 22. During such translation, the arcuate, triangular end 24 remains in close proximity to the tapered fuselage 10 with its wider forward end moving upward around the maximum transverse dimension of the fuselage 10 at that location. Thus, the door assembly for all intents and purposes is maintained within the aerodynamic contour of the aircraft.

In view of the foregoing arrangement and construction, it is apparent that for aerial delivery as well as ground loading and unloading operations the center and the

side sections

17 and 18 respectively are all readily opened permitting the free and unobstructed movement of cargo to and from the compartment 12. During ground loading and unloading operations, the ramp 14 is in contact with the associated loading surface to facilitate the movement of the cargo into the compartment. On the other hand, during the aerial delivery operation, the ramp 14- may be positioned with its upper surface in the plane of and constituting an extension of the cargo fioor while the pressure door 27 and door assembly 16 is opened. With the pressure door 27 and door assembly 16 in the elevated position, the opening 13 is of maximum size for free and unobstructed airdrop of cargo. At the same time, due to the particular construction and operation of the door assembly 16, maximum structural integrity of the fuselage 10 is maintained to assure support of the empennage 11 and against damage or distortion thereof by the aerodynamic forces and loads.

What is claimed is:

1. A door assembly for the storage compartment of a cargo aircraft comprising:

multiple, generally coextensively disposed sections hinged one to another for movement to and from extreme positions of extension and retraction where they are juxtaposed and superimposed respectively;

a link pivotally connected at one of its ends to the aircraft and at its other end to one end of said multiple sections;

a sliding connection between the other end of said multiple sections and said aircraft;

at least one releasable latch operative between said multiple sections and said aircraft when said multiple sections are in the extended position aforesaid;

a first actuator between said link and said aircraft operative to swing the link concurrently translating the connected multiple sections linearly;

a second actuator between said several multiple sections operative to move them to and from their extreme positions aforesaid; and

a control for the sequential release of each said latch and operation of said actuators.

2. The door assembly of claim 1 wherein said multiple sections include a center section and a pair of side sections with said link and said sliding connections each engaging said center section.

3. The door assembly of claim 2 wherein said center section terminates in a transversely curved, generally triangular member with its apex aft and each said side section terminates in the plane of the forward side of said member so as to abut when said multiple sections are in the extended position aforesaid.

4. The door assembly of claim 2 wherein at least one of said latches is between each side section and the adjacent aircraft structure, and means for the operation of all of said latches in unison.

5. The door assembly of claim 1 wherein said sliding connection includes a roller carried by said aircraft and a track carried by said one multiple section.

6. The invention of claim 3 wherein said storage compartment is located within a nacelle of the aircraft and said door assembly is mounted adjacent and adapted to close the aft end of said nacelle when said multiple sections are disposed in the extended position, the exterior surface of said member conforming in shape to the adjacent nacelle surface to form a smooth and aerodynamically clean continuation thereof when said multiple sections are extended as aforesaid.

7. The door assembly of claim 2 wherein each said side section is approximately one half the width of said center section and said second actuator includes an extensible and contractable power unit connected between said center section and each said side section whereby the outer longitudinal edges of said side sections are proximate one another and their inner longitudinal edges are disposed substantially in the plane of the respective outer longitudinal edges of said center section when the said multiple sections are in the retracted position aforesaid.

8. The door assembly of claim 2 wherein said storage compartment is pressurized at least in part being closed at one end by a sealed door, said multiple sections are located externally of said compartment, and said sealed door constitutes the link aforesaid.

9. The door assembly of claim 2 wherein all of said actuators are hydraulic cylinders adapted to be operatively connected to a hydraulic system of the aircraft.

10. The door assembly of claim 9 including hydraulically actuated release means for said latches connectable to said hydraulic system.

References Cited UNITED STATES PATENTS 7/1961 McCormack 244137 X 4/1964 Pauli 244-137 X U.S. Cl. X.R.