the reference eye position to any point along the upper limit of the forward windshield panels, and similarly, a line of vision from a point two inches below the reference eye position to the lower limit of the forward windshield panels. [Supp. 35, 22 F. R. 7359, Sept. 14, 1957] § 4b.352 Windshields and windows.

(a) All internal glass panes shall be of a nonsplintering safety type.

(b) The windshield panes which the pilots will be directly behind in the normal conduct of their duties and the supporting structures for such panes shall have sufficient strength to withstand without penetration the impact of a fourpound bird when the velocity of the airplane relative to the bird along the airplane's flight path is equal to the value of Vo at sea level selected in accordance with § 4b.210(b) (4).

(c) Means shall be provided to minimize the danger to the pilots from flying windshield fragments due to bird impact unless it can be shown by analysis or test that the probability of occurrence of a critical fragmentation condition is of a low order. The provisions of this paragraph are intended to apply to all transparent panes in the cockpit section which appear in the front view of the aircraft, are inclined 15 degrees or more to the longitudinal axis of the aircraft, and have any portion located so that fragmentation thereof will constitute a hazard to the pilots.

(d) The design of windshields and windows in pressurized airplanes shall be based on factors peculiar to high altitude operation. (See also § 4b.373.)

NOTE: Factors peculiar to high altitude operation as they may affect the design of windshields and windows include the effects of continuous and cyclic pressurization loadings, the inherent characteristics of the material used, the effects of temperatures and temperature differentials, etc.

[15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-6, 17 F.R. 1094, Feb. 5, 1952; Amdt. 4b-6, 22 F.R. 5564, July 16, 1957; Amdt. 4b11, 24 F.R. 7069, Sept. 1, 1959]

FIGURE 4b-17-POWERPLANT AND AUXILIARY CONTROLS (c) The controls shall be so located and arranged with respect to the flight crew's seats that there exists full and unrestricted movement of each control without interference from either the cockpit structure or the flight crew's clothing when seated with the seat belt fastened. This shall be demonstrated for individuals ranging from 5' 2" to 6' 0'' in height.

(d) Identical powerplant controls for each engine shall be located to prevent any misleading impression as to the engine to which they relate.

(e) The wing flap (or auxiliary lift device) and landing gear controls shall comply with the following:

(1) The wing flap control shall be located on top of the pedestal aft of the throttle(s), centrally or to the right of the pedestal centerline and shall be not less than 10 inches aft of the landing gear control.

(2) The landing gear control shall be located forward of the throttles and shall be operable by each of the pilots when seated with seat belts fastened.

(f) The control knobs shall be shaped in accordance with Figure 4b-22, and such knobs shall be of the same color, but of a color in contrast with that of not only the other control knobs but also the surrounding cockpit.

(a) Airplane cabins shall be provided with at least one easily accessible external door.

(b) Means shall be provided for locking each external door and for safeguarding against opening in flight either inadvertently by persons or as a result of mechanical failure. It shall be possible to open external doors from either the inside or the outside even though persons may be crowding against the door from the inside. The means of opening shall be simple and obvious and shall be so arranged and marked that it can be readily located and operated even in darkness.

NOTE: It is not the intent to prohibit the use of inward opening doors if sufficient measures are provided to prevent occupants from crowding against the door to an extent which would interfere with the opening of the door.

(c) Reasonable provisions shall be made to prevent the jamming of any external door as a result of fuselage deformation in a minor crash.

(d) External doors shall be so located that persons using them will not be endangered by the propellers when appropriate operating procedures are employed.

(e) Means shall be provided for a direct visual inspection of the locking mechanism by crew members to ascertain whether all external doors for which the initial opening movement is outward, including passenger, crew, service, and cargo doors, are fully locked (see also 4b.362 (e) (5) for emergency exits). In addition, visual means shall be provided to signal to appropriate crew members that all normally used external doors are closed and in the fully locked position.

[15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-4, 16 F. R. 11759, Nov. 21, 1951; Amdt. 4b-2, 20 F.R. 5306, July 26, 1955; Amdt. 4b-6, 22 F.R. 5565, July 16, 1957]

§ 4b.356-1 External doors (FAA policies which apply to § 4b.356).

The provisions of § 4b.356 should be applied to all cabin and crew compartment external doors usable for entrance or egress. It is not restricted to the main cabin door. Cargo and service doors not suitable for emergency egress need only comply with § 4b.356 (e) and safeguarding against opening in flight as a result of mechanical failure.

[Supp. 25, 20 F.R. 2279, Apr. 8, 1955]

§ 4b.356-2 Auxiliary latching devices (FAA policies which apply to § 4b.356(b)).

(a) The use of auxiliary latching devices is permitted. Such devices would include dual locking handles, other types of locking and safetying devices, and two position handles, and where one operation such as pushing or pulling on the handle unlocks the latching mechanism and the second operation of turning the handle unlatches the door for opening. Auxiliary safetying devices should be used only as an additional safety factor and should not be used as a means of correcting an inadequate design of the primary locking or latching means. The advantages to be gained from the installation of auxiliary or dual safety devices (safety chains and dual handle main locking means) should be weighed against the need to easily and rapidly open the door in case of emergencies so that the overall level of safety is as high as practicable.

(b) All locking or safety means, including safety chains and latches of any kind, should be so positioned and designed that their presence, location and means of operation are obvious to one not familiar with door designs.

(1) The means of fastening safety devices should be sufficiently simple to make removal easy.

(2) Any emergency release mechanism installed to release the safety device should operate with a simple motion and upon the application of relatively small forces.

(3) All locking devices should be readily operable from both inside and outside of the airplane and be appropriately marked both inside and outside.

(c) Auxiliary safety devices meeting the standards of paragraph (b) of this section may be fastened in place during the entire flight. It will not be necessary to have such devices unlatched during takeoff and landing. Auxiliary safety devices such as safety chains or bars that do not meet the standards of paragraph (b) of this section may be used provided operating instructions are installed at or near the device and a placard is installed requiring the removal of such devices prior to takeoff and landing. [Supp. 25, 20 F. R. 2279, Apr. 8, 1955] § 4b.356-3 Power operated external doors (FAA policies which apply to § 4b.356(b)).

Power operated doors should be so designed that the door can be opened by manual means even when power is inactivated. The loss of power should not cause the door to become unlatched.10

[Supp. 25, 20 F. R. 2279, Apr. 8, 1955] § 4b.356-4 Means for safeguarding against inadvertent opening in flight (FAA policies which apply to § 4b.356(b)).

Auxiliary latching devices may be used to reduce the probability of inadvertent opening in flight provided they meet the standards and conditions covered in § 4b.356-2.

(a) It is acceptable to create a limited access zone in front of the door to eliminate the possibility of a passenger using the door handle as a steadying means and thereby inadvertently opening the door. Although providing a restricted zone by means of a barrier may appear to conflict with the requirements of § 4b.362 (g) for an unobstructed passageway to Type I and II emergency exits, it is considered that it would contribute sufficiently to the overall safety of the aircraft occupants to be permitted. This device may be a rope, chain, rigid bar or gate. Such installations should be waist high to provide the maximum benefits for an adult and the end fasten

10 Since emergency landings, such as in the wheels-up condition, may reasonably result in the severance of electrical wires or rupture of hydraulic and pneumatic lines, the power which may be needed for operation of the doors or exits may be lost. Similarly, it is conceivable that under emergency conditions, the electrical power source may be purposely interrupted to reduce the possibility of fire.

ings should be simple to make removal easy. It is not considered acceptable to install full-length auxiliary doors, but waist-high rigid gates would be acceptable provided they open toward the door and will not block the opening of the cabin door in any way. The locking means should be one which could be easily overridden such as a springloaded ball type latch.

(b) Flexible gates such as those made from webbing are not acceptable on the basis that persons may become entangled during an emergency egress. The use of a barrier to prevent persons from inadvertently opening the door in flight does not eliminate the need for a safety means to provide for possible malfunctioning of the primary locking mechanism; however, the auxiliary safetying means of § 4b.356-2 may eliminate the need for a restricted zone.

[Supp. 25, 20 F. R. 2279, Apr. 8, 1955] § 4b.356-5 Direct visual inspection (FAA policies which apply to § 4b.356(e)).

The means of complying with § 4b.356 (e) will depend upon the type of door and locking mechanism used. It should be determined in all cases that means are provided to ascertain that an unsatisfactory condition does not exist after closing the door. In some instances a central window for viewing the position of the mechanism may be sufficient while other cases may require one or more windows in the door frame to permit inspection of the bayonet location relative to that portion of the lock in the door frame. The need for and/or the number and location of inspection openings or windows will depend on the type of door and locking mechanism used.

[Supp. 25, 20 F. R. 2279, Apr. 8, 1955] § 4b.356-6 Visual indicating system (FAA policies which apply to § 4b.356(e)).101

(a) The visual indicating system may consist of an indicator for each individual door, or a system connecting all doors in series. If the latter system

10b The objective herein is to be able to ascertain by visual means that the door and/or locking means is sufficiently engaged to eliminate hazards emanating from an improperly closed door. Outward opening doors present a different problem from inward opening doors.

is used, it need not necessarily show which door is not fully locked.

(b) It is not necessary that more than one crew member be able to ascertain by a visual signal that all external doors, normally used by the crew in supplying the airplane, or in loading and unloading passengers and cargo, are fully closed and locked. The visual signal should be located so that it may easily be seen by the appropriate crew member from his station.

[Supp. 25, 20 F. R. 2279, Apr. 8, 1955]

§ 4b.357 Door louvres.

Where internal doors are equipped with louvres or other ventilating means, provision convenient to the crew shall be made for stopping the flow of air through the door when such action is found necessary.

§ 4b.358 Seats, berths, and safety belts.

(a) General. At all stations designated as occupiable during take-off and landing, the seats, berths, belts, harnesses, and adjacent parts of the airplane shall be such that a person making proper use of these facilities will not suffer serious injury in the emergency landing conditions as a result of inertia forces specified in § 4b.260. Seats and berths shall be of an approved type (see also § 4b.643 concerning safety belts).

(b) Arrangement. (1) Passengers and crew shall be afforded protection from head injuries by one of the follow-ing means:

(i) Safety belt and shoulder harness which will prevent the head from contacting any injurious object,

(ii) Safety belt and the elimination of all injurious objects within striking radius of the head,

(iii) Safety belt and a cushioned rest which will support the arms, shoulders, head, and spine.

(2) For arrangements which do not provide a firm hand hold on seat backs. hand grips or rails shall be provided along aisles to enable passengers or crew members to steady themselves while using the aisles in moderately rough air.

(3) All projecting objects which would cause injury to persons seated or moving about the airplane in normal flight shall be padded.

(4) Berths shall be so designed that the forward portion is provided with a padded end board, a canvas diaphragm,

or other equivalent means, capable of withstanding the static load reaction of the occupant when subjected to the forward inertia force specified in § 4b.260. Berths shall be free from corners and protuberances likely to cause serious injury to a person occupying the berth during emergency conditions.

(5) Seats for all crew members at flight deck stations shall incorporate provisions for the use of a shoulder harness and the seats with such provisions shall comply with the strength requirements of paragraph (c) of this section.

(6) Seats for cabin attendants shall be disposed within the passenger compartment near approved floor level emergency exits. (See § 4b.362 (g).)

(c) Strength. All seats and berths and their supporting structure shall be designed for occupant weight of 170 pounds with due account taken of the maximum load factors, inertia forces, and reactions between occupant, seat, and safety belt or harness corresponding with all relevant flight and ground load conditions, including the emergency

landing conditions prescribed in § 4b.260. In the case of berths, the forward inertia force shall be considered in accordance with paragraph (b) (4) of this section and need not be considered with respect to the safety belt. In addition, the following shall apply:

(1) Pilot seats shall be designed for the reactions resulting from the application of pilot forces to the flight controls as prescribed in § 4b.224.

(2) In determining the strength of the seat or berth attachments to the structure, and the safety belt or shoulder harness attachments to the seat, berth, or structure, the inertia forces specified in § 4b.260 (a) shall be multiplied by a factor of 1.33.

[15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-6, 17 F. R. 1094, Feb. 5, 1952; Amdt. 4b-8, 18 F. R. 2215, Apr. 18, 1953; Amdt. 4b-3, 21 F.R. 993, Feb. 11, 1956; Amdt. 4b-6, 22 F.R. 5565, July 16, 1957; Amdt. 4b-8, 23 FR. 2591, Apr. 19, 1958]

§ 4b.358-1 Application of loads (FAA policies which apply to § 4b.358).

The actual forces acting on seats, berths, and supporting structure in the various flight, ground and emergency landing conditions will consist of many possible combinations of forward, sideward, downward, upward, and aft loads. However, in order to simplify the struc