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MILITARY STANDARD 1333A

AIRCREW STATION GEOMETRY FOR MILITARY AIRCRAFT

DEPARTMENT OF DEFENSE
Washington, D.C. 20301

30 June 1976

THE FOLLOWING ARE EXTRACTS.

1. PURPOSE AND SCOPE

     1.1 Purpose - This standard establishes the design requirements for aircrew station geometry in military aircraft. Compliance assures a design that is efficient, safe and comfortable for operation by aircrew personnel for the ranges of body sizes specified by the procuring activity. 

     1.2 Scope - The requirements defined herein apply to all piloted aircraft procured by the military departments."

2. REFERENCED DOCUMENTS

     Seventeen Specifications, Standards and other publications are cited as part of this standard to the extent specified herein.

3. DEFINITIONS

     3.1 Design eye position - The design eye position is a reference datum point based on the eye location that permits the specified vision envelope required by MIL-STD-850 [Aircrew Station Vision Requirements for Military Aircraft], allows for posture slouch and is the datum point from which the aircrew station geometry is constructed.

      3.2 Horizontal vision line - The horizontal vision line is a reference line passing through the design eye position (3.1) and parallel to the fuselage reference line. 

      3.3 Back tangent line - The back tangent line is established by a vertically inclined plane tangent to the back of the seated man at the thoracic region and buttocks. 

      3.4 Bottom tangent line - The bottom tangent line is a horizontal line coincident with the reference line of the seat. 

      3.5 Seat reference point (SRP) - The seat reference point is the intersection of the back tangent line and the bottom tangent line."

      3.6 Neutral seat reference point (NSRP) - The neutral seat reference point is the seat reference point with the seat in the nominal mid-position of the seat adjustment range. This seat position will place the 50th percentile (seated height) man with his eye in the design eye position. 

      3.7 Buttock reference point - The buttock reference point is the most forward limit of the bottom tangent line and represents the body pressure points located 5.75 inches forward of the seat reference point. This represents the area of the lowest seat cushion compression under a static vertical load of 1-g.

      3.8 Thigh tangent line - The thigh tangent line is the average line of the aircraft seat when occupied by a crewmember with the maximum weight as specified by the procuring activity. The thigh tangent line originates at the buttock reference point and extends upward and forward from that point to the forward edge of the seat. 

      3.9 Control grip reference point - The control grip reference point is the point at which the crewman's second finger (middle digit) is in contact with the forward or downward face of any grip-type control such as control stick, control wheel, collective stick, or throttle. 

      3.10 Efficient, safe, and comfortable aircrew operation - Efficient, safe, and comfortable aircrew operation is defined by the dimensions, size, and adjustments of an aircrew stations that will allow the aircrew to: reach and actuation all controls, have external vision in accordance with MIL-STD-850, have unobstructed internal  view of all critical controls and displays, be able to function effectively without undue fatigue or discomfort, and escape without injury. 

4. GENERAL REQUIREMENTS

      4.1 Selection of geometry Aircrew station geometry shall take into consideration all aspects of control and display requirements associated with safe flight, execution of the mission, and safe emergency egress and shall conform to the requirements specified herein. A description and explanation of the proposed geometry determined on the basis of the requirements contai8ned herein shall be approved by the procuring activity. This description shall contain a rationale for the proposed geometry and shall delineate the accommodation limitations, if any, for a specified aircrew population. 

            4.1.1 Basic geometry guide  - A basic geometry guide for this document is presented as Figure 1. 

            4.1.2 Seating geometry - The seating geometry shall conform to the requirements of Figure 2.

      4.2 External vision - The external vision for aircrew stations shall conform to the requirements of MIL-STD-850.

      4.3 Internal vision - The internal vision of all controls and displays shall conform to the requirements of MIL-STD-203 [Aircrew Station Controls and Displays for Fixed Wing Aircraft] and MIL-STD-250 [Cockpit Controls, Location and Actuation of for Helicopters].

      4.4 Ejection clearance dimensions - The ejection clearance dimensions for aircrew stations shall conform to the requirements of Figure 3. 

      4.5 Anthropometric considerations - The aircrew station geometry shall be based on the anthropometric percentile range specified by the procuring activity and employing the factors outlined in MIL-STD-1472 [Human Engineering Design Criteria for Military Systems, Equipment and Facilities] and/or obtained from studies conducted in accordance with the requirements of MIL-H-46855. 

            4.5.1 Body dimensions - The requirements for all body dimensions shall conform to the following documents for each Service, as applicable: 

            Army

                 USANL TR 72-51-CE [The Body Size of Soldiers, Anthropometry 1966]
                 USANL TR 72-52-CE [Anthropometry of U.S. Army Aviators 1970]

            Navy

                  NAEC ACEL Report No. 533 [Anthropometry of Naval Aviators 1964]

                  4.5.1.1 Functional body data - Figures 4, 10, 11, 12, 13, 14, and 15 present arm and leg link values derived from cockpit work space studies and functional considerations of anthropometric data. (PMTC Report TIP-75-1 [A Program to Compute the Range of Leg Reach from the Seat-Reference-Point, June 1975] provides the computation method employed.) [Because of space limitations, these figures are not reproduced here.]

                  4.5.1.2 Reach zones - Applicable data of reach/grasp capability defined in USAF Report AMRL-TDR-64-59 [KENNEDY, K. W., Reach Capability of the USAF Population, Phase 1, The Outer Boundaries of Grasping-Reach Envelopes for the Shirt-Sleeved, Seated Operator, AMRL-TDR-64-59, Aerospace Medical Research Laboratory, Wright-Patterson Air Force Base, OH, September 1964] shall be considered for reach zones illustrated in Figure 4 and defined as follows: [Figure 4 does not add substantial information for the understanding of reach zones and is not included here.]

ZONE 1 Restraint Harness Locked - Functional Reach
This zone includes the area that can be functionally reached with the seat in the full up (two-way seat) position and/or in the full up and forward (four-way) seat adjust position by the fully restrained crew-member without stretch of arm or shoulder muscles. Controls placed in this zone shall include those frequently used during operation of the aircraft in flight phases which required full restraint. This would include such flight phases as takeoff, landing, low altitude-hi-speed flight, weapons delivery, and escape. This zone defines the maximum limit allowed for the placement of emergency (escape system) controls and establishes the forwardmost operation limit of primary flight and propulsion controls (except for helicopters).

ZONE 2 Restraint Harness Locked - Maximum Functional Reach
This zone includes the area that can be functionally reached with the seat in the full up (two-way seat) position and/or in the full up and forward (four-way) seat adjust position by the fully restrained crew- member with maximum stretch of shoulder and arm muscles. This zone defines the maximum limit allowed for the placement of helicopters primary flight and propulsion controls and the placement of emergency controls other than escape controls.

ZONE 3 Restraint Harness Unlocked - Maximum Functional Reach
This zone includes the area that can be functionally reached with the seat in full up (two-way seat) position and/or full up and forward (four-way) seat adjust position by the crewmember with the shoulder restraint fully extended and the arms stretched full length. Only non-critical flight controls and ground operated controls shall be placed in this zone. For helicopters, emergency controls may be placed in this zone subject to the procuring activity approval."

     4.6 Effects of personal and survival equipment - All geometry requirements specified herein are based upon nude body dimensions and to not include any tolerance for clothing or equipment, except flight boots and basic headgear. Many items of personal and survival equipment significantly alter the crewman's position in the aircrew station. All such equipment specified by the procuring activity shall be considered at the earliest point in design, and adjustments made to the geometry to accommodate required equipment for the anthropometric range specified by the procuring agency. A check list of most frequently used items is contained in NAVAIR 13-1-6 Series Manuals [Aviation-Crew Systems Manual] and as otherwise specified by the procuring activity. 

     4.7 Accessibility of controls - Crewstation controls shall be accessible and usable by the entire anthropometric range of percentiles specified by the procuring activity. 

          4.7.1 Selection of controls - Selection of controls for the respective crewmembers shall be based upon the analyses and data derived from the studies required by MIL-H-46855 [Human Engineering Requirements for Military Systems, Equipment and Facilities] or by other techniques specified by the procuring agency. 

          4.7.2 Location and actuation of controls - The location and actuation of controls shall conform to MIL-STD-203 or MIL-STD-250, as applicable. Specific control locations and arrangements shall be established with the specified reach zones in accordance with the designated aircraft mission requirements. 

5. CONTROL AND DISPLAY REQUIREMENTS

     5.1 Controls

          5.1.1 Pitch and roll controls

               5.1.1.1 Stick type - The vertical location of the handgrip reference point shall be located from 11 to 15 inches above the neutral seat reference point, as required for the particular aircraft. The maximum envelope of stick throw shall be based on Zone 1 reach as defined in . . . paragraph 4.5.1.2. A minimum clearance of 1.5 inches . . . shall be maintained between the stick and all structures when the stick is in any extreme position. Special consideration shall be given to the effect of personal and survival equipment . . . when establishing stick envelope. 

                    (a) For helicopters the vertical distance from the cyclic reference point to the neutral seat reference point shall not exceed 12 inches to permit supporting the forearm against the leg. 

               5.1.1.2 Control wheel type - The height of the handgrip reference point above the neutral seat reference point shall be based upon the specified wheel configuration and upon maintaining a 1.5 inch clearance . . . between the bottom surface of the wheel through its full forward, aft, and rotational travel and the leg of the crewmember of maximum specified percentile with the seat in the full up position and yaw control pedals in full aft adjustment. The maximum wheel throw envelope shall be based on Zone 1 reach as defined in . . . paragraph 4.5.1.2. The minimum clearance between wheel and structure shall be 1.5 inches as shown . . . while a minimum clearance of 0.5 inch shall be maintained between the crewmembers' hand and body. 

          5.1.2 Propulsion controls

               5.1.2.1 Single throttle - The location of the forwardmost position of the throttle shall be based on Zone 1 reach as defined in . . . paragraph 4.5.1.2. The aft position shall be based on the aft structural clearance of the maximum specified arm . . .  .

               5.1.2.2 Multiple throttle - Locate the same as for single throttle, except the geometry of all throttles shall be based upon the forwardmost position of the throttle furthest from the crewman laterally.

          5.1.3 Collective lever

          5.1.4 Yaw control pedals - The yaw control shall consist of two pedals of the configuration conforming to MIL-B-8584. Differential braking as defined by MIL-B-8584 [Brake System, Wheel, Aircraft, Design of] shall be provided by these pedals. The most forward adjustment position of the yaw controls shall be based upon the specified percentile leg length seated with the seat full aft and full down, and yaw controls on, full forward throw, with the brake fully depressed . . .  . The most aft adjustment position of the yaw controls shall be based on the minimum specified percentile leg length seated with seat full forward and full up and full forward yaw control throw, with the brake fully depressed . . .  . Yaw control pedals forward and aft range requirements shall be based on the functional leg throw data . . .  . These requirements have been obtained for various seat positions with respect to a horizontal reference line (referred to as the heel reference line in PMTC Report, TIP-75-1) which is located 4.75 inches below the brake fulcrum point on the yaw controls (shown in Figure 2) and parallel to the horizontal vision line. A minimum clearance . . . of 1.5 inches above and 0.75 inches on either side of the pedal shall be maintained over the maximum specified percentile foot in a flight boot, throughout the full pedal travel. Throughout the range of yaw control adjustment and travel, the distance from the brake fulcrum to the nearest point on the crewstation floor shall be between 4.75 to 6.0 inches. Pedal length shall be the minimum required to satisfy braking requirements. With normal braking procedures, a 1.5 inch clearance between maximum size footwear and all adjacent instruments and structure shall be maintained . . .  . 

     5.2 Displays

          5.2.1 Lower surface consoles 

          5.2.2 Overhead consoles

          5.2.3 Instrument panel - The instrument panel shall be located so as to provide a 1.5 inch clearance with the crewmembers' legs through the full range of leg movement . . .  . On aircraft equipped with ejection seats, clearance shall be provided as shown in Figure 3. The panel shall provide the most normal viewing angle as practicable from the design eye position. 

     5.3 Seats - Aircrew seats conforming to the requirement of MIL-A-81815 [Aircrew, Automated Escape System], MIL-S-58095 [Seat System, Crashworthy, Non-Ejection, Aircrew, General Specifications for], MIL-S-81771 [Seat, Adjustable, Aircraft, General Specification for], and MIL-A-23121 [Aircrew Environmental Escape and Cockpit Capsule System, General Specifications for] shall provide the body positioning capability in accordance with the requirements specified herein. 

6. MULTI-CREW STATION REQUIREMENTS

     6.1 Tandem arrangement

          6.1.1 Dual control
               
               (a) The single crew station geometry specified herein shall be duplicated for both crew stations unless otherwise specified by the procuring activity. 

               (b) Minimum fore and aft spacing between the crew stations shall be based on the minimum space required to accommodate the largest specified percentile crew member in each station while maintaining full control movements in both stations. 

               (c) The external vision for the forward and aft crew stations shall conform to MIL-STD-850.

          6.1.2 Single control

     6.2 Side-by-side arrangement

          6.2.1 Dual control

               (a) . . .

               (b) Both crew positions shall be on the same level, unless otherwise specified. The lateral centerline spacing between crewmembers shall be a minimum of 26 inches and a maximum of 42 inches centerline to centerline for configurations with displays and controls common for both crewmembers. In rotary wing aircraft, the dimensions shall be a minimum of 26 inches and a maximum of 50 inches. 

               (c) Minimum lateral spacing shall be based upon minimum clearances between seat and structure or controls, and providing for no interference between crewmembers in performance of their flight tasks. The absolute minimum clearance between seats shall be 3 inches for non-ejection seats and 6 inches for ejection seats. 

          6.2.2 Single control - The flight control station geometry shall conform to the requirements herein and the other crew station geometry shall be configured for the specific aircraft mission. 

7. NOTES

     7.1 International interest


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