33 addition, there must be a visual warning means to signal the appropriate flight crewmembers if any external door is not fully closed and locked. The means must be designed such that any failure or combination of failures that would result in an erroneous closed and locked indication is improbable for doors for which the initial opening movement is not inward.
(f) External doors must have provisions to prevent the initiation of pressurization of the airplane to an unsafe level if the door is not fully closed and locked. In addition, it must be shown by safety analysis that inadvertent opening is extremely improbable.
[(g) Cargo and service doors not suitable for use as emergency exits need only meet paragraphs (e) and (f) of this section and be safeguarded against opening in flight as a result of mechanical failure or failure of a single structural element.]
(h) Each passenger entry door in the side of the fuselage must qualify as a Type A, Type I, or Type II passenger emergency exit and must meet the requirements of §§ 25.807 through 25.813 that apply to that type of passenger emergency exit.
(i) If an integral stair is installed in a passenger entry door that is qualified as a passenger emergency exit, the stair must be designed so that under the following conditions the effectiveness of passenger emergency egress will not be impaired:
(1) The door, integral stair, and operating mechanism have been subjected to the inertia forces specified in § 25.561(b)(3), acting separately relative to the surrounding structure.
(2) The airplane is in the normal ground attitude and in each of the attitudes corresponding to collapse of one or more legs of the landing gear.
(j) All lavatory doors must be designed to preclude anyone from becoming trapped inside the lavatory, and if a locking mechanism is installed, it be capable of being unlocked from the outside without the aid of special tools.
b. Guidance.
(1) Refer to § 25.809 for related requirements, and AC 25.783-1, “Fuselage, Doors, Hatches, and Exits,” dated 12/10/86, for related guidance. (Amendment 25-54)
(2) Paragraph (b). Protection against inadvertent exit door openings is required, but at the same time, a single-motion handle operation to open a passenger door should be provided to facilitate emergency egress. Auxiliary locking devices that complicate the door opening process may be accepted as necessary, though undesirable, if it can be substantiated that there is no other practicable means of protecting against inadvertent exit door opening. (Amendment 25-54)
(i) Auxiliary locking devices that may initially be assumed to be necessary, in fact might be eliminated by assuring that the door is designed in accordance with human factors principles. A door that is opened by moving a handle from the up position to a down position represents a design contrary to the convention believed to be familiar to most people in the aircraft industry. Therefore, this design may lend itself to contributing to an inadvertent door opening, as has actually happened. In addition, a door handle that is in the up position when the door is closed lends itself to more easily being used as a handhold in flight, which may result in an inadvertent opening. The threat inherent in this design would practically mandate the inclusion of auxiliary locking devices, to the possible detriment of emergency egress capability.
On the other hand, a door handle which operates in a conventional manner (i.e., moves up to open, moves down to close) is not as prone to inappropriate operation, nor is it in a location as susceptible for use as a handhold in flight. Consequently, this design, in addition to being more user-friendly from a human factors viewpoint, may eliminate any need for auxiliary locking devices. (Amendment 25-54)
(ii) Handles which operate in a rotary manner (in a plane parallel to that of the door) are not known to have been implicated in any incidents as noted above, nor has clockwise versus counterclockwise rotary motion been known to be controversial in this regard (except that counterclockwise may be the most universally accepted convention for opening jars, faucets, etc.). Likewise, these handles have not been considered to represent the attractive handhold devices in flight that other types of handles might and, furthermore, they require a deliberate effort to actuate. (Amendment 25-54)
(iii) When it can be substantiated to the satisfaction of the FAA that auxiliary locking devices are necessary to comply with the inadvertent door opening requirements of §§ 25.783(a) and 25.809(f) (Amendment 25-72, 25.810(a)), and it is not through design defect that these devices are provided, any potentially adverse impact of these devices on emergency egress must be minimized through adherence to the available guidance pertinent to auxiliary locking devices. "Design defect" in this context may reasonably be considered to include designs which neglect to address known human factors concerns as highlighted herein.
Auxiliary locking devices which are deemed to be not simple and obvious, are not acceptable.
Devices which are hidden by design or color, recessed, contoured, camouflaged, or otherwise concealed to the degree that a naive person may need to read a placard to determine how to open the door are not simple and obvious, and are therefore not acceptable. Suitable demonstrations may be required to substantiate acceptability in this regard. (Amendment 25-54)
(3) Paragraphs (b) through (e). The requirements of these paragraphs apply to all cabin and pilot compartment external doors usable for entrance or egress. It is not restricted to the main cabin door. (Amendment 25-0)
(4) Paragraph (b). Auxiliary locking devices. (Amendment 25-0)
(i) The use of auxiliary locking devices is permitted. Such devices would include dual locking handles, other types of locking and safety devices, two position handles, and dual operation handles (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
35 opening). Auxiliary locking 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 locking 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. (Amendment 25-0)
(ii) 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. (Amendment 25-0) (A) The means of fastening safety devices should be sufficiently simple to make removal easy. (Amendment 25-0) (B) Any emergency release mechanism installed to release the safety device should operate with a simple motion and upon the application of relatively small forces.
(Amendment 25-0) (C) All locking devices should be readily operable from both inside and outside of the airplane and be appropriately marked both inside and outside. (Amendment 25-0)
(iii) Auxiliary safety devices meeting the standards of paragraph (ii) above 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 (ii) above 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. For related guidance, Refer to paragraph 351b(3). (Amendment 25-
0)
(5) Paragraph (b). Power operated external doors. 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. Since emergency landings, such as the wheels-up condition, may 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. (Amendment 25-0)
(i) 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 § 25.813 for an unobstructed passageway to Type I, and Type II emergency exits, it is considered that it would contribute sufficiently to the overall safety of the airplane 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 fastenings 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
36 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 spring-loaded ball type latch.
(Amendment 25-0)
(ii) 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 safety means covered above may eliminate the need for a restricted zone. (Amendment 25-0)
(6) Paragraph (e). Visual indicating system. The objective herein is to be able to ascertain by visual means that the door 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. (Amendment 25-0)
(i) 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 is used, it need not necessarily show which door is not fully locked. (Amendment 25-0)
(ii) It is not necessary that more than one crewmember 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 crewmember from his station.
(Amendment 25-0)
66. AMENDMENT 25-88, Effective December 9, 1996.
a. Regulation.
(a) Each cabin must have at least one easily accessible external door.
(b) There must be a means to lock and safeguard each external door against opening in flight (either inadvertently by persons or as a result of mechanical failure or failure of a single structural element either during or after closure). Each external door must be openable from both the inside and the outside, even though persons may be crowded against the door on the inside of the airplane. Inward opening doors may be used if there are means to prevent occupants from crowding against the door to an extent that would interfere with the opening of the door. The means of opening must be simple and obvious and must be arranged and marked so that it can be readily located and operated, even in darkness. Auxiliary locking devices may be used.
(c) Each external door must be reasonably free from jamming as a result of fuselage deformation in a minor crash.
(d) Each external door must be located where persons using them will not be endangered by the propellers when appropriate operating procedures are used.
(e) There must be a provision for direct visual inspection of the locking mechanism to determine if external doors, for which the initial opening movement is not inward (including passenger, crew, service, and cargo doors), are fully closed and locked.
The provision must be discernible under operational lighting conditions by appropriate crewmembers using a flashlight or equivalent lighting source. In addition, there must be a visual warning means to signal the appropriate flight crewmembers if any external door is not fully closed and locked. The means must be designed such that any failure or combination of failures that would result in an erroneous closed and locked indication is improbable for doors for which the initial opening movement is not inward.
(f) External doors must have provisions to prevent the initiation of pressurization of the airplane to an unsafe level if the door is not fully closed and locked. In addition, it must be shown by safety analysis that inadvertent opening is extremely improbable.
(g) Cargo and service doors not suitable for use as emergency exits only meet paragraphs (e) and (f) of this section and be safeguarded against opening in flight as a result of mechanical failure or failure of a single structural element.
[(h) Each passenger entry door in the side of the fuselage must meet the applicable requirements of §§ 25.807 through 25.813 for a Type II or larger passenger emergency exit.]
(i) If an integral stair is installed in a passenger entry door that is qualified as a passenger emergency exit, the stair must be designed so that under the following conditions the effectiveness of passenger emergency egress will not be impaired:
(1) The door, integral stair, and operating mechanism have been subjected to the inertia forces specified in § 25.561(b)(3), acting separately relative to the surrounding structure.
(2) The airplane is in the normal ground attitude and in each of the attitudes corresponding to collapse of one or more legs of the landing gear.
(j) All lavatory doors must be designed to preclude anyone from becoming trapped inside the lavatory, and if a locking mechanism is installed, it be capable of being unlocked from the outside without the aid of special tools.
b. Guidance.
(1) Refer to § 25.809 for related requirements, and AC 25.783-1, “Fuselage, Doors, Hatches, and Exits,” dated 12/10/86, for related guidance. (Amendment 25-54)
(2) Paragraph (b). Protection against inadvertent exit door openings is required, but at the same time, a single-motion handle operation to open a passenger door should be provided to facilitate emergency egress. Auxiliary locking devices that complicate the door opening process may be accepted as necessary, though undesirable, if it can be substantiated that there is no other practicable means of protecting against inadvertent exit door opening. (Amendment 25-54)
(i) Auxiliary locking devices that may initially be assumed to be necessary, in fact might be eliminated by assuring that the door is designed in accordance with human factors principles. A door that is opened by moving a handle from the up position to a down position represents a design contrary to the convention believed to be familiar to most people in the aircraft industry. Therefore, this design may lend itself to contributing to an inadvertent door opening, as has actually happened. In addition, a door handle that is in the up position when the door is closed lends itself to more easily being used as a handhold in flight, which may result in an inadvertent opening. The threat inherent in this design would practically mandate the inclusion of auxiliary locking devices, to the possible detriment of emergency egress capability.
On the other hand, a door handle which operates in a conventional manner (i.e., moves up to open, moves down to close) is not as prone to inappropriate operation, nor is it in a location as susceptible for use as a handhold in flight. Consequently, this design, in addition to being more user-friendly from a human factors viewpoint, may eliminate any need for auxiliary locking devices. (Amendment 25-54)
(ii) Handles which operate in a rotary manner (in a plane parallel to that of the door) are not known to have been implicated in any incidents as noted above, nor has clockwise versus counterclockwise rotary motion been known to be controversial in this regard (except that counterclockwise may be the most universally accepted convention for opening jars, faucets, etc.). Likewise, these handles have not been considered to represent the attractive handhold devices in flight that other types of handles might and, furthermore, they require a deliberate effort to actuate. (Amendment 25-54)
(iii) When it can be substantiated to the satisfaction of the FAA that auxiliary locking devices are necessary to comply with the inadvertent door opening requirements of §§ 25.783(a) and 25.809(f) (Amendment 25-72, 25.810(a)), and it is not through design defect that these devices are provided, any potentially adverse impact of these devices on emergency egress must be minimized through adherence to the available guidance pertinent to auxiliary locking devices. "Design defect" in this context may reasonably be considered to include designs which neglect to address known human factors concerns as highlighted herein.
Auxiliary locking devices which are deemed to be not simple and obvious, are not acceptable.
Devices which are hidden by design or color, recessed, contoured, camouflaged, or otherwise concealed to the degree that a naive person may need to read a placard to determine how to open the door are not simple and obvious, and are therefore not acceptable. Suitable demonstrations may be required to substantiate acceptability in this regard. (Amendment 25-54)
(3) Paragraphs (b) through (e). The requirements of these paragraphs apply to all cabin and pilot compartment external doors usable for entrance or egress. It is not restricted to the main cabin door. (Amendment 25-0)
(4) Paragraph (b). Auxiliary locking devices. (Amendment 25-0)
(i) The use of auxiliary locking devices is permitted. Such devices would include dual locking handles, other types of locking and safety devices, two position handles, and dual operation handles (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 locking 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 locking 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. (Amendment 25-0)
(ii) 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. (Amendment 25-0) (A) The means of fastening safety devices should be sufficiently simple to make removal easy. (Amendment 25-0) (B) Any emergency release mechanism installed to release the safety device should operate with a simple motion and upon the application of relatively small forces.
(Amendment 25-0) (C) All locking devices should be readily operable from both inside and outside of the airplane and be appropriately marked both inside and outside. (Amendment 25-0)
(iii) Auxiliary safety devices meeting the standards of paragraph (ii) above 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 (ii) above 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. For related guidance, Refer to paragraph 351b(3). (Amendment 25-
0)
(5) Paragraph (b). Power operated external doors. 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. Since emergency landings, such as the wheels-up condition, may 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. (Amendment 25-0)
(i) 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
40 inadvertently opening the door. Although providing a restricted zone by means of a barrier may appear to conflict with the requirements of § 25.813 for an unobstructed passageway to Type I, and Type II emergency exits, it is considered that it would contribute sufficiently to the overall safety of the airplane 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 fastenings 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 spring-loaded ball type latch.
(Amendment 25-0)
(ii) 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 safety means covered above may eliminate the need for a restricted zone. (Amendment 25-0)
(6) Paragraph (e). Visual indicating system. The objective herein is to be able to ascertain by visual means that the door 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. (Amendment 25-0)
(i) 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 is used, it need not necessarily show which door is not fully locked. (Amendment 25-0)
(ii) It is not necessary that more than one crewmember 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 crewmember from his station.
(Amendment 25-0) 67 - 80. [RESERVED]
41 SECTION 25.785 SEATS, BERTHS, SAFETY BELTS, AND HARNESSES
81. REGULATION IN EFFECT AT ADOPTION OF PART 25.
a. Regulation.
(a) Each seat, berth, safety belt, harness, and adjacent part of the airplane, at each station designated as occupiable during takeoff and landing, must be designed so that a person making proper use of these facilities will not suffer serious injury in an emergency landing as a result of the inertia forces specified in § 25.561.
(b) Each seat and berth must be approved.
(c) Each occupant must be protected from head injury by-
(1) A safety belt and shoulder harness that will prevent the head from contacting any injurious object;
(2) A safety belt plus the elimination of any injurious object within striking radius of the head; or
(3) Safety belt plus a cushioned rest that will support the arms, shoulders, head and spine.
(d) If the seat backs do not have a firm hand hold, there must be a hand grip or rail along each aisle to enable occupants to steady themselves while using the aisles in moderately rough air.
(e) Each projecting object that would injure persons seated or moving about the airplane in normal flight must be padded.
(f) Each berth must be designed so that the forward part has a padded end board, canvas diaphragm, or equivalent means that can withstand the static load reaction of the occupant when subjected to the forward inertia force specified in § 25.561. Berths must be free from corners and protuberances likely to cause serious injury to a person occupying the berth during emergency conditions.
(g) Each crewmember seat at flight deck stations must have provisions for a shoulder harness. These seats must meet strength requirements of paragraph (i) of this section.
(h) Cabin attendant seats must be in the passenger compartment near approved floor level emergency exits.
(i) Each seat, berth, and its supporting structure, must be designed for an occupant weight of 170 pounds, considering the maximum load factors, inertia forces, and reactions between the occupant, seat, and safety belt or harness, at each relevant flight and ground load condition (including the emergency landing conditions prescribed in § 25.561). For berths, the forward inertia force must be considered in accordance with paragraph (f) of this section and need not be considered with respect to the safety belt. In addition-
(l) The structural analysis and testing of the seats, berths, and their supporting structures may be determined by-
(i) Assuming that the critical load in the forward, sideward, downward, and rearward directions (as determined from the prescribed flight, ground, and emergency landing conditions) acts separately; and
(ii) Using selected combinations of loads if the required strength in each specified direction is substantiated;
(2) Each pilot seat must be designed for the reactions resulting from the application of the pilot forces prescribed in § 25.395; and
(3) The inertia forces specified in § 25.561 must be multiplied by a factor of l.33 (instead of the fitting factor prescribed in § 25.625) in determining the strength of the attachment of-
(i) Each seat to the structure; and
(ii) Each belt or harness to seat or structure.
b. Guidance.
(1) Paragraph (a). In order for the seat belt to be effective, it should be positioned to lay across the hip bone and ideally be about 45 degrees from the horizontal. An acceptable range for this angle is 35 degrees to 55 degrees. An acceptable range for the shoulder harness is 30 degrees above to 5 degrees below the horizontal. Refer to ACs 25.785-1A, “Flight Attendant Seat and Torso Restraint System Installations,” dated 1/6/94, and 43.13-1A, “Acceptable Methods, Techniques, and Practices-Aircraft Inspection and Repair (with Errata Sheet),” dated 4/17/72, for related guidance. When testing a seat to demonstrate compliance with the static requirements of § 25.561, the testing should be conducted with an occupant center of gravity (CG) location as defined in NAS 809 (referenced in Technical Standard Order (TSO) C39) and AS8049 (referenced in the current version of TSO-C127). This CG location should be utilized in any airplane interface load analysis conducted. (Amendment 25-0)
(2) Paragraphs (a) and (c). The FAA issued policy memorandum ANM-03-115-28, dated October 2, 2003, and titled “Policy Statement on Use of Surrogate Parts When Evaluating
43 Seatbacks and Seatback Mounted Accessories for Compliance with §§ 25.562(c) (5) and
25.785(b) and (d). This policy may be used with any test method used to demonstrate compliance with blunt force trauma for items mounted on the seatback. The policy is applicable to Amendment 25-0, for §§ 25.785 (a) and (c) as follows: (Amendment 25-0)
(i) In many row-to-row seat configurations, seatback mounted accessories are installed within the head paths of forward facing seated occupants. In order to demonstrate compliance with the aforementioned requirements, tests are conducted to assess the injury potential of these seatbacks and accessories. This policy only addresses head injury caused by blunt trauma. It does not address parts that become loose or sharp projections that are formed that may be injurious to a seated occupant during a head impact. (Amendment 25-0)
(ii) The types of tests that are conducted for blunt trauma assessments are dependant on the certification basis of the airplane. Typically, airplanes which do not have § 25.562(c)(5) in their certification basis, must still comply with the more general occupant protection requirements of §§ 25.785(a) and (c). Sections 25.785(a) and (c) require that a seat be designed so that an occupant would not suffer “serious injury” in an emergency landing and that injurious objects within the striking radius of the head be eliminated. As a result, seatbacks/accessories on these airplanes must be evaluated to ensure that an occupant would not suffer serious head injury from blunt trauma. (Amendment 25-0)
(iii) Currently, blunt trauma tests are conducted with seatback mounted accessories represented by actual production parts or parts that are similar in construction to the production parts. Industry has informed the FAA that certification delays occur due to the unavailability of actual accessories for testing. In addition, accessories are typically damaged during certification tests and are not usable in subsequent tests or for installation and delivery to a customer. Several specimens of the same part are repeatedly used, and damaged, during certification tests due to test failures or substantiating alternate seatback designs. This results in significant costs to manufacturers and customers. (Amendment 25-0)
(iv) The FAA has determined that it is acceptable to use a surrogate test article made of 6061-T4 aluminum which meets the criteria below in lieu of an accessory for demonstrating compliance with §§ 25.785(a) and (c) for blunt trauma assessments. An exception to the use of the surrogate test article occurs when the accessory is more rigid (deflects less and absorbs less energy during impact) than the plate defined in this AC. In that case, the accessory should be used in the test(s) and not a surrogate test article. The following criteria are applicable when using a surrogate test article during blunt trauma testing in accordance with §§ 25. 785(a) and (c): (Amendment 25-0) (A) The surrogate part should be fabricated from 6061-T4 aluminum and have a minimum thickness of 0.238-inch (i.e., 0.25-inch minus a 0.012-inch manufacturing tolerance) at all locations. The length and width of the surrogate part should equal, within tolerances, the length and width of the actual part, respectively. (Amendment 25-0) (B) The exposed surface of the surrogate part that will be impacted should be flat. That is, it is not required to have the contour of the accessory’s exposed surface represented
44 by the surrogate part. Note that this is based on typical accessory installations which are essentially mounted flush with the seatback and have a generally homogeneous contact area.
Small variations in the surface due to the contour of plastic parts may be ignored. Designs that differ from this (e.g., a design with an exposed structural protrusion) might require the exposed surface of the actual part to be represented in order to adequately assess head injury potential.
(Amendment 25-0) (C) The weight of the surrogate part, and additional ballast if needed, should be ±10 percent of the weight of the actual part. (Amendment 25-0) (D) The surrogate part should be located on the seatback in the same place
(i.e., within manufacturing tolerances for mounting the actual part) where the actual part would be located in terms of the x and y coordinates in Figure 81-1. The surrogate part should be located such that the surface, which will be contacted during the test, is at the same location (i.e., within manufacturing tolerances for mounting the actual part) where the actual part would be in terms of the z coordinate (refer to figure 81-1). (Amendment 25-0) (E) The surrogate part should be attached to the seat by the final production hardware or a conservative representation of the final production hardware. For substantiating blunt trauma requirements, a conservative representation of the attachment hardware would be at least as rigid as the actual hardware. The surrogate part should be mounted so that it would not move farther or faster, with respect to the seatback, than the actual part during the test.
(Amendment 25-0) (F) If the surrogate part cracks during a test, the test results are invalid.
(Amendment 25-0) (G) A surrogate part made of a material and thickness other than 6061-T4 aluminum in a nominal thickness of 0.25-inch may be used if an FAA Aircraft Certification Office finds that it is at least as rigid (i.e., it deflects less and absorbs less energy during the test).
Surrogate test articles which are less rigid than the aluminum surrogate part defined above are not addressed in this AC. If an applicant desires to use a surrogate part which is less rigid, its use should be approved through the issue paper process (or equivalent) or by an FAA policy memorandum. Testing may be required to determine the acceptability of these less rigid surrogate parts. (Amendment 25-0)