> U.S. Department\
> of Transportation![](media/image1.wmf){width="0.48333333333333334in"
> height="0.4798611111111111in"}

Federal Aviation\
Administration

  ---------- ----------------------------------------- -- ------------ ----------------
  Subject:   [INFORMATION]{.underline}: New Policy        Date:        November 25,
             with respect to compliance with §                         2002
             25.785(d), Amendment 25-88, for                           
             certification of passenger seat armrests.                 

                                                                       

  From:      Acting Manager, Transport Airplane           Reply to     02-115-15
             Directorate, Aircraft Certification          Attn. of:    
             Service, ANM-100                                          

                                                                       

  To:        See Distribution                             Regulatory   AC 25-17
                                                          Reference    

                                                                       
  ---------- ----------------------------------------- -- ------------ ----------------

The purpose of this memorandum is to provide additional Federal Aviation
Administration (FAA) certification policy with respect to compliance
with Title 14 Code of Federal Regulations (CFR) 25.785(d), Amendment
25-88, for transport category airplane passenger seat armrests. This
policy is specifically aimed at documenting an alternative to current
policy and guidance for demonstrating compliance with § 25.785(d) for
seat armrests, which may be struck by persons seated behind them. The
current version of § 25.785(d), as revised by Amendment 25‑88, is very
similar to the original version in part 25.

## 

## Current Regulation

> Section 25.785(d), Amendment 25-88:
>
> "Each occupant of a seat that makes more than an 18-degree angle with
> the vertical plane containing the airplane centerline must be
> protected from head injury by a safety belt and an energy absorbing
> rest that will support the arms, shoulders, head, and spine, or by a
> safety belt and shoulder harness that will prevent the head from
> contacting any injurious object. Each occupant of any other seat must
> be protected from the head injury by a safety belt and, as appropriate
> to the type, location, and angle of facing of each seat, by one or
> more of the following:

"(1) A shoulder harness that will prevent the head from contacting any
injurious object.

"(2) The elimination of any injurious object within striking radius of
the head.

"(3) An energy absorbing rest that will support the arms, shoulders,
head, and spine."

> Because this regulation is essentially the same from original to
> current version, the policy and guidance promulgated by this
> memorandum is applicable to all amendments to part 25 to date.

## Relative Existing Guidance and Past Practice

> Because the requirements of § 25.785(d) have not significantly changed
> since the adoption of part 25, the policy that is provided for
> § 25.785(c)(2), Amendment 25-0, in Advisory Circular 25-17, "Transport
> Airplane Cabin Interiors Crashworthiness Handbook" dated
>
> July 15, 1991, is still in effect and may be utilized in demonstrating
> compliance with armrests in the head strike area. The guidance
> provided is found in paragraphs 81b(3) and 81b(5) of the AC.
>
> In addition to the guidance in AC 25-17, the Transport Standards Staff
> of the Transport Airplane Directorate provided additional guidance to
> an applicant in a March 19, 1992, in a response to a request for
> written policy. The applicant was in the process of providing
> passenger seats for a new transport category airplane and requested
> clarification concerning the seat offset armrests as follows:
>
> "...There are seat placements within each of the aircraft that are
> configured with varying degrees of offset, ranging from 0 to 1.64
> inches. With respect to an FAA ruling that defines armrests that
> protrude into the head strike zone of the seat behind it as a head
> strike violation, where a head strike zone is defined as a 35-inch arc
> from the seat reference point (SRP) located between the center of the
> armrests, there is no established limit for seat offset."
>
> "This definition depicts a seat "offset" that is based on a seat
> positioned directly behind and in-line with the armcap. Since there
> can be varying degrees of offset, there is no definition for the
> boundary of acceptable or unacceptable offset. For instance, would
>
> a seat that is offset two (2) inches from being directly in line with
> a seat just forward
>
> be considered outside the armcap head strike zone?"
>
> The FAA provided the following written response to the applicants'
> request for guidance:
>
> "Your first question concerned the amount of offset for seat armrests
> that is permissible without having to substantiate the armrest end cap
> for headstrike. When seats are located directly behind one another,
> the armrests are lined up longitudinally, and the headstrike zone is
> treated as a 35-inch arc measured over the width of the seat, between
> the armrests. When the seats are offset, such as might happen in the
> non-constant section of an airplane, a 35-inch arc measured in this
> manner would intersect an armrest of the forward seat. We consider
> that this situation has two aspects."
>
> "The first of these occurs where the forward seat is an aisle seat and
> has an exposed (bounded on one side only) armrest. In this case, we
> consider that an offset that positions the forward armrest within the
> projected headstrike path of the rear occupant as described above is
> not acceptable unless the armrest is substantiated for headstrike.
> Depending upon the certification basis of the airplane this
> substantiation may take different forms. For airplanes with a
> certification basis prior to Amendment 25-64 to part 25, the
> substantiation may be a test, or an analytical comparison to the other
> components in the headstrike path, showing that the armrests is no
> worse. For airplanes with Amendment 25-64 in the certification basis,
> a Head Injury Criterion measurement of 1000 or less must be shown."
>
> "The second aspect occurs when the offset is not exposed. In this
> case, due to the protection afforded by the surrounding seatbacks, we
> consider that an offset of two (2) inches is acceptable without
> further substantiation of the armrest. Offsets greater than two (2)
> inches would have to be substantiated as described above."
>
> The Seattle Aircraft Certification Office sent a letter to an
> applicant on July 31, 1992, that modified the guidance provided above
> as follows:
>
> "The subject provision, at all Amendment levels to date, requires the
> elimination of any injurious object within striking radius of the
> head. Past guidance on the subject is compiled in the reference AC.
> This letter supplements that AC guidance by correcting an error which
> was carried over from past guidance, and expands on existing
> guidance."
>
> "The width of the headstrike zone had been previously defined by the
> extended centerlines of each armrest. Observance of this definition
> would have likely required the armrest of every seat group on every
> airplane to be padded, including those seats directly
>
> in line in fuselage constant sections. It has been determined that
> this was not an intended consequence of this definition, and that the
> width of the headstrike zone should be redefined by the extended inner
> surfaces of the armrests."

As noted above there are existing means to demonstrate compliance with §
25.785(d) and these means will remain as acceptable approaches to
certification of the armrests. The policy is as follows:

## Definitions Relative to New Policy

> Armrests that might possibly be struck by persons seated behind (aft
> of) them are characterized as "bounded" or "unbounded." [Bounded
> armrests]{.underline} are defined as follows:

1.  An armrest that has a seatback on both sides, with the distance
    between the structure of the adjacent seatbacks no greater than
    five (5) inches, or

2.  An armrest that has a seatback on one side and the airplane sidewall
    panel or a wall that is part of an airplane furnishing (e.g.,
    galley, closet, lavatory) on the other side with the distance
    between the structure of the seatback and the panel/wall no greater
    than five (5) inches.

> For purposes of this memorandum, the structure of the seatback is
> considered to be the parts of the seatback with load carrying
> capability. It does not include upholstery material or soft foam
> installed for occupant comfort. In some seat designs there is a metal
> frame in the seatback that forms the support structure to which the
> foam and upholstery are used to provide the shape of the seatback.
> When measuring the distance between the structure of the adjacent
> seatbacks of no greater than five (5) inches, the measurement would be
> between these metal or composite supports structures.
>
> [Unbounded armrests]{.underline} are those that do not meet either
> definition above. Additionally, seat places that are located aft of
> [unbounded armrests]{.underline} may be characterized as either
> "exposed" or "non-exposed." The [non-exposed seat place]{.underline}
> is typically an aisle seat place, i.e., located adjacent to a
> passenger aisle (see Figure 1). The [exposed seat place]{.underline}
> is typically located where the number of seats in the row forward is
> different from that of the seat row aft. For example, near Type III
> overwing exits, many airplanes have a double seat installed inboard of
> the exit with an empty space between the seat and the exit. The seat
> row aft of the double seat has a triple seat (see Figure 2). In Figure
> 2, seat place "A" is an exposed seat place that makes the outboard
> armrest of the double seat an [unbounded exposed armrest]{.underline}.
>
> The definitions above apply to all armrests in the airplane as
> applicable. The existing policy contained in AC 25-17 paragraphs
> 81b(3) and 81b(5) are still applicable to the armrests identified in
> the new policy below.

## New Policy

> Note: The policy below addresses armrests within the 35 inch head
> strike arc and surfaces 18 inches and greater above the floor.
> Armrests outside the 35-inch head strike arc and armrest surfaces less
> than 18 above the floor are acceptable as defined in AC 25-17
> paragraphs 81b(3) and 81b(5).

1.  An armrest is acceptable by inspection if the armrests of two
    consecutive (i.e., one aft of the other) seat assemblies (seats need
    not be of the same part number ) are offset no greater one half
    (0.5) inch total, including design and production tolerances.

2.  Bounded armrests and non-exposed unbounded armrests are acceptable
    if:

> a\. the armrests of two consecutive seat assemblies are offset greater
> than one half (0.5) inch but no greater than two (2) inches total,
> including design, and production tolerances, [and]{.underline}
>
> b\. the breakover feature of the seatback(s) adjacent to the armrest
> in the forward seat assembly is (are) locked out.
>
> The seatback breakover feature may be locked out by any method that
> requires a tool to release the lock out provision. The lockout of the
> breakover feature must be effective for the seatback in the upright
> position used for taxi, takeoff and landing. Seatbacks incorporating
> an energy absorbing feature to meet the HIC requirements of § 25.562
> are considered to have the breakover lockout and are acceptable.
> Whatever the method of seatback breakover lock out, there typically is
> some movement of the seatback. This movement of the seatback is
> acceptable as long as when the seatback is moved to the worst case
> position by a small hand load applied to the top of the seatback, the
> armrest is still afforded protection by the seatback, with the end of
> the top of the armrest being forward of the aft side of the seatback.

3.  Bounded armrests and non-exposed unbounded armrests, where the
    offset is greater than two (2) inches total, including design and
    production tolerances, need to be addressed as being injurious
    objects within the striking radius of the head, e.g., by padding the
    armrest.

4.  Exposed unbounded armrests; if the armrests of two consecutive seat
    assemblies that are offset by more than one half (0.5) inch total,
    including design and production tolerances, need to be addressed as
    being injurious objects within the striking radius of the head,
    e.g., by padding the armrest.

5.  Armrests that are padded (using appropriate padding material as
    described in paragraph 81b(3) of AC 25-17) must have the padding
    cover the length of the armrest that is encompassed by 35-inch and
    smaller head strike arcs. Bounded armrest, where the seatback(s)
    have the breakover feature locked out, need not be padded to
    encompass the entire 35 inch head strike arc because the seatbacks
    prevent the contact of the armrest on the forward side of the
    seatback(s). Therefore, these armrests need only be padded to the
    forward edge of the seatback(s) in their upright position achieved
    after the small hand force is applied to the seatback. Portions of
    the armrest surface that cannot be contacted by the head are not
    required to be padded, e.g., the lower (or under) surface of a
    curved armrest.

6.  As an alternative to the use of padding, surfaces within the
    striking radius of the head that translate out of the striking
    radius under a nominal (10 pound) load may be considered to provide
    adequate protection, e.g., armrests that have been pivoted upward,
    which pivot downward out of the head strike arc under the nominal
    load. During an evaluation of this feature, the load must be applied
    in a direction that approximates the motion of a seated and belted
    occupant in the seat aft of the armrest under crash conditions.

> ![](media/image2.jpeg){width="6.0in" height="3.8819444444444446in"}

## ![](media/image3.png)

## 

## Effect of Policy

> The general policy stated in this document does not constitute a new
> regulation or create what the courts refer to as a "binding norm." The
> office that implements policy should follow this policy when
> applicable to the specific project. Whenever an applicant's proposed
> method of compliance is outside this established policy, it must be
> coordinated with the policy issuing office, e.g., through the issue
> paper process or equivalent.
>
> Applicants should expect that the certificating officials will
> consider this information when making findings of compliance relevant
> to new certificate actions. Also, as with all advisory material, this
> policy identifies one means, but not the only means, of compliance.
>
> Any questions related to this policy may be directed to Jayson Claar
> at (425) 227-2194.
>
> /s/
>
> Ali Bahrami

  ------------ ------------------------- ---------------------------------
               **DISPOSITION OF PUBLIC   
               COMMENTS ON DRAFT POLICY  
               STATEMENT 02-115-15,      
               COMPLIANCE WITH           
               25.785(D), AMENDMENT      
               25-88, CERTIFICATION OF   
               PASSENGER SEAT ARMRESTS** 

  Commenter    Comment                   Disposition

  GAMA         GAMA is concerned that    The definitions do apply to all
               all armrests meeting the  seats, however, only those
               definition of unbounded   armrests within the 35-inch head
               armrests would be         strike arcs need to be padded. A
               required to be padded     clarification to the policy will
               under the new policy.     be made to address this issue.

  GAMA         GAMA is concerned that    The policy item number 1 is
               the policy item numbers 1 intended to address armrest
               and 2 are contradictory   offset 0 to .5 inches and item
               concerning the amount of  number 2 is intended to address
               acceptable offset.        bounded armrest and non-exposed
                                         unbounded armrest offset between
                                         .5 and 2.0 inches. A
                                         clarification to the policy will
                                         be made to address this issue.

  GAMA         GAMA proposes that for    The FAA agrees with the comment
               bounded armrest offset    provided that the seatbacks do
               more than 2.0 inches, the provide the protection. To
               padding need not extend   provide the protection the
               to the full 35 inches     seatback breakover feature must
               when the seatbacks        be locked out. A clarification to
               provide protection for    the policy will be made to
               the armrest forward of    address this issue.
               the aft side of the       
               seatback.                 

  GAMA         GAMA is concerned that    Many of the armrests pivot upward
               the policy item number 6  such that the armrest could
               is unclear on the intent  protrude beyond the seatbacks.
               and application of this   The intent of this policy is to
               policy for armrests that  accept these armrests that
               translate out of the      translate out of the striking
               headstrike arc with a     radius under a nominal (10 pound)
               nominal 10 pound load.    load. A clarification to the
                                         policy will be made to address
                                         this issue.
  ------------ ------------------------- ---------------------------------

  ------------ ------------------------- ---------------------------------
  GAMA         GAMA proposes that the    The FAA agrees that another
               option of passing a HIC   acceptable method of
               test is included in       demonstrating compliance is a
               policy item number 6.     successful HIC test on an object.
                                         However, that approach is already
                                         documented as an acceptable means
                                         of compliance in this policy
                                         memo. No change to the policy
                                         memo is required.

  Boeing       Boeing is concerned that  The FAA agrees that the policy
               the policy does not       does not define what "the
               define what "the          structure" of the seatback is and
               structure" of the         does need to provide
               seatback is and requests  clarification. A clarification to
               clarification.            the policy will be made to
                                         address this issue.

  Boeing       Boeing requested a        The FAA partially agrees with the
               revision to clarify the   Boeing request. A clarification
               five (5) inch measurement to the effectivity of the policy
               applies only within the   will be included.
               35 inch headstrike arc.   

  Boeing       Boeing is concerned that  The FAA partially agrees with the
               the policy item number 2  Boeing request for the changes to
               is not clear and proposed this item. A revision to the
               revised and additional    policy will be made to address
               wording for clarification this issue.
               for the issue of locked   
               out seatbacks.            

  Boeing       Boeing is concerned that  The FAA partially agrees with the
               policy item number 5 is   Boeing request for the changes to
               not clear and proposed    this item. A revision to the
               revised and additional    policy will be made to address
               wording for               this issue.
               clarification. The Boeing 
               concern is what armrest   
               parts need to be padded   
               and how much of the       
               armrest needs padding.    

  Boeing       Boeing requested the      The FAA agrees with the Boeing
               policy item number 6 be   position in general that
               revised to state loads    deviations to this policy can be
               above 10 pounds be        made on a case-by-case basis but
               acceptable on a           we disagree that it needs to be
               case-by-case basis.       documented in the policy. No
                                         change to the policy will be
                                         made.

                                         
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