[Federal Register Volume 65, Number 115 (Wednesday, June 14, 2000)]
[Notices]
[Pages 37449-37452]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-14910]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

[Policy Statement Number ACE-00-23.561.01]


Proposed Issuance of Policy Memorandum, Methods of Approval of 
Retrofit Shoulder Harness Installations in Small Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of policy statement, request for comments.

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SUMMARY: This document announces an FAA proposed general statement of 
policy applicable to the modification of small airplanes. This document 
advises the public, in particular, small airplane owners and modifiers, 
of additional information related to acceptable methods of approval of 
retrofit shoulder harness installations. This notice is necessary to 
advise the public of FAA policy and give all interested persons an 
opportunity to present their views on the policy statement.

DATES: Comments submitted must be received no later than July 14, 2000.

ADDRESSES: Send all comments on this policy statement to the individual 
identified under FOR FURTHER INFORMATION CONTACT at Federal Aviation 
Administration Small Airplane Directorate, ACE-111, Room 301, 901 
Locust, Kansas City, Missouri 64106.

FOR FURTHER INFORMATION CONTACT: Michael Reyer, Federal Aviation 
Administration, Small Airplane Directorate, ACE-111, Room 301, 901 
Locust, Kansas City, Missouri 64106, telephone (816) 329-4131; fax 816-
329-4090; e-mail; [email protected].

SUPPLEMENTARY INFORMATION:

[[Page 37450]]

Comments Invited

    Interested persons are invited to comment on this proposed policy 
statement, ACE-00-23-561-01, by submitting such written data, views, or 
arguments as they desire. Comments should be marked, ``Comments to 
policy statement ACE-00-23.561-01,'' and be submitted in duplicate to 
the above address. The Manager, Small Airplane Directorate, will 
consider all communications received on or before the closing date for 
comments.

Background

    This notice announces the availability of the following proposed 
policy memorandum, ACE-00-23.561-01, for review and comment. The 
purpose of this memorandum is to address methods of approval for 
retrofit shoulder harness installations in small airplanes.

Effect of General Statement of Policy

    The FAA is presenting this information as a set of guidelines 
appropriate for use. However, this document is not intended to 
establish a binding norm, it does not constitute a new regulation and 
the FAA would not apply or rely upon it as a regulation. The FAA 
aircraft Certification Offices (ACO's) and Flight Standards District 
Offices (FSDO's) that certify changes in type design and approve 
modifications in normal, utility, and acrobatic category airplanes 
should generally attempt to follow this policy when appropriate. 
Applicants should expect that the certificating officials would 
consider this information when making findings of compliance relevant 
to retrofit shoulder harness installations.
    Also, as with all advisory material, this statement of policy 
identifies one means, but not the only means, of compliance.
    Because this proposed general statement of policy only announces 
what the FAA seeks to establish as policy, the FAA considers it to be 
an issue for which public comment is appropriate. Therefore, the FAA 
requests comment on the following proposed general statement of policy 
relevant to compliance with 14 CFR Part 23, Sec. 23.561, and other 
related regulations.

General Statement of Policy

Summary

    Retrofit shoulder harness installations may be approved by 
Supplemental Type Certificate (STC), Field Approval, or minor change. 
An STC is the most rigorous approval and it offers the highest 
assurance that all of the airworthiness regulations have been met. 
Field Approvals are granted for an individual airplane for an 
alteration that involves little or no engineering. Some shoulder 
harness installations have been made as a minor change. In this case, 
the FAA certificated mechanic who installs it makes an entry in the 
airplane's maintenance log.
    We do not encourage retrofit shoulder harness installation by minor 
change. However, the FAA should not prohibit the airplane owner to have 
such installations made by minor change, even though they may not 
provide the 9.0 g forward occupant protection required by regulation 
[Civil Air Regulation (CAR) 3.386 or 14 CFR Part 23, Sec. 23.561]. 
While the preferred method of approval of such installations is by STC 
of Field Approval, shoulder harnesses could be installed by minor 
change in:
    (1) The front seats of those small airplanes manufactured before 
July 19, 1978, and
    (2) In other seats of those small airplanes manufactured before 
December 13, 1986.
    This may be performed as a minor change only if the installation 
requires no modification of the structure (such as welding or drilling 
holes). Also, the airplane's certification basis must be CAR 3 or 
predecessor regulations, or Part 23 prior to Amendment 23-20. Any 
retrofit shoulder harness installation, even those approved as a minor 
change, is a safety improvement over occupant restraint by seat belt 
alone.

Introduction

    In January 1997, the Anchorage Aircraft Certification Office (ACO) 
Manager requested the Small Airplane Directorate to study the issue of 
retrofit shoulder harness installations in small airplanes. The 
Anchorage ACO specifically requested guidance for a Supplemental Type 
Certificate (STC) project to install shoulder harnesses in Piper PA-18 
series airplanes. This proposed policy presents the results of our 
study for public comment. Approval of the harness installation only is 
addressed. Approval of the harness is made to Technical Standard Order 
(TSO)-C114, Torso Restraint Systems.
    During 1998, our office participated in an Aviation Safety Program 
to increase the use and effectiveness of occupant restraint systems in 
general aviation airplanes. This program is in support of the occupant 
survivability element of the Administrator's Safety Agenda for general 
aviation, which has a goal of significantly reducing the number of 
fatal accidents over a ten-year period. Most of the content of this 
proposed policy was presented in a paper at the August 19, 1998, 
meeting of this Aviation Safety Program.
    The Manager of the Continuing Airworthiness Maintenance Division of 
Flight Standards, AFS-300, has reviewed this proposed policy and 
concurs with it.

References

    1. Advisory Circular (AC) 21-34, Shoulder Harness--Safety Belt 
Installations, June 4, 1993.
    2. AC 23-4, Static Strength Substantiation of Attachment Points for 
Occupant Restraint System Installations, June 20, 1986.
    3. AC 43.13-2A, Acceptable Methods, Techniques, and Practices--
Aircraft Alterations, Revised 1977.
    4. Order 8300.10, Airworthiness Inspectors Handbook, Volume 2, 
Change 10, October 30, 1995.
    5. Technical Standard Order (TSO)-C114, Torso Restraint Systems, 
March 27, 1987.

Discussion

Requirements

    1. Front seat shoulder harnesses required. 14 CFR Part 23, 
Sec. 23.785, as amended by Amendment 23-19, effective July 18, 1977, 
required all normal, utility, and acrobatic category airplanes for 
which application for types certificate was made on or after July 18, 
1977, to have an approved shoulder harness for each front seat. Section 
91.205(b)(14) requires all small civil airplanes manufactured after 
July 18, 1978, to have an approved shoulder harness for each front 
seat. The shoulder harness must be designed to protect the occupant 
from serious head injury when the occupant experiences the ultimate 
inertia forces specified in Sec. 23.561(b)(2). The inertia force 
requirements are discussed in paragraph 3 below.
    2. Shoulder harnesses required at all seats. Section 91.205(b)(16) 
requires all normal, utility, and acrobatic category airplanes with a 
seating configuration of 9 or less, excluding pilot seats, manufactured 
after December 12, 1986, to have a shoulder harness, for forward-facing 
and aft-facing seats, that meets the requirements of Sec. 23.785(g) 
[which requires that the occupant be protected from the ultimate 
inertia forces specified in Sec. 23.56(b)(12)]. Section 23.78(g) also 
provides: ``For other seat orientations, the seat and restraint means 
must be designed to provide a level of occupant protection equivalent 
to that provided for forward and aft-facing seats with safety belts and 
shoulder harnesses installed.'' The above Part 91 operating rule stems 
from Sec. 23.2, Special retroactive requirements,

[[Page 37451]]

Amendment 23-32, effective December 12, 1985.
    3. Civil Air Regulation (CAR) 3.386 and Part 23, Sec. 23.561, 
Amendments 23-0 through 23-34, effective February 17, 1987, require 
occupant protection from serious injury during a minor crash landing 
when ``proper use is made of belts or harnesses provided for in the 
design,'' when the occupants are subjected to the following ultimate 
inertia forces:

------------------------------------------------------------------------
                                  Normal and utility
                                       category       Acrobatic category
------------------------------------------------------------------------
Forward.........................  9.0 g.............  9.0 g
Sideward........................  1.5 g.............  1.5 g
Upward..........................  3.0 g.............  4.5 g
------------------------------------------------------------------------

    At Amendment 23-36, effective September 14, 1988, the above words 
in quotes were changed in Sec. 23.561 to read: ``proper use is made of 
seats, safety belts, and shoulder harnesses provided for in the 
design.'' The ultimate inertia forces remain the same through the 
current amendment.
    For inertia force requirements for occupant protection preceding 
CAR 3, refer to Table 1 in AC 21-34, which lists the requirements for 
the regulations dating from Bulletin 7-A to the original Part 23.

Methods of Approval of Retrofit Shoulder Harness Installations

    1. Supplemental Type Certificate (STC): An STC is the most 
desirable and most rigorous approval, and it offers the highest 
assurance that all of the airworthiness regulations have been met. The 
STC approvals are issued by the FAA Aircraft Certification Offices 
(ACO's). Supplemental Type Certificate approvals are usually obtained 
by a shoulder harness installation kit supplier for multiple airplane 
installations in a particular airplane model or model series.
    Advisory Circular 21-34 and 23-4 (References 1 and 2) provide 
guidance and acceptable means of compliance for shoulder harness and 
seat belt installations. Advisory Circular 23-4 specifically addresses 
Part 23 installations. These AC's would also be applicable to 
installations in airplanes having a certification basis of predecessor 
regulations (CAR 3, etc).
    The applicant for an STC will often use a salvaged airplane 
fuselage to perform the pull test to apply the prescribed ultimate 
inertia loads because the 9.0 g forward load, in particular, may cause 
structural failure or permanent set. It may be a problem that the 
available test airframe may be stronger than the lowest strength 
production airframe. This may particularly be a problem in steel tube 
airframes. During the production of such airframes over the course of 
many years, even decades, various specification materials may be used. 
For example, many CAR 3 (and predecessor regulations) airplanes were 
originally produced from 1025 steel tubing and later constructed from 
higher strength 4130 steel. In the case studied, two different 
specification 1025 steel tubings were used that may have an ultimate 
tensile strength (UTS) ranging from 55,000 to 79,000 psi. The UTS of 
4130 steel is 90,000 to 95,000 psi.
    The test article should be representative of the lowest strength 
production airframe. This may be accomplished by a conformity 
inspection using the production drawings. The strength of materials of 
parts affected by the modification needs to be verified by the airframe 
manufacturer's process and production records. The serial number of the 
test article needs to be verified. An alternative course of action 
would be to determine, by appropriate tests (e.g., chemical analysis, 
hardness tests, strength tests), the strength of the parts of the test 
article affected by the modification, and test to a conservatively 
higher load that accounts for the difference in strengths of the test 
article and the lowest strength production article. Determination of 
the higher applied test load should take into account any uncertainty 
in the test(s) used to determine the strength of the material.
    Advisory Circular 23-4 provides an acceptable means of compliance 
for static strength substantiation of attachment points for occupant 
restraint system installations. A test block is described to apply the 
9.0 g forward inertia load. The safety belt installation alone is 
tested to 100 percent of the load. The shoulder and safety belt 
combined load is distributed 40 percent to the shoulder harness and 60 
percent to the seat belt.
    In airplanes having side-by-side seats, the pull test may need to 
be applied simultaneously to the harness fittings for both seats, 
depending on the type of harness and where the upper ends are anchored. 
Normally, this would not be necessary for a single diagonal belt 
shoulder harness attached to the outboard fuselage side or wing spar 
root end.
    In the case of a pull test for a retrofit shoulder harness 
installation in the tandem-seat tubular steel PA-18 fuselage, the 
forward inertia load was applied simultaneously for both harnesses. 
This was done for convenience in applying and reacting the loads. It 
was found that due to the tube geometry, the load at the aft harness 
attachment caused a tension in the rear spar carrythrough tube, to 
which the front seat shoulder harness upper end was attached. This 
enabled the front seat harness attachment to test to a higher load than 
if the pull test was applied to each harness individually. In such a 
case, the test loads for each harness should be performed individually.
    Part 21, Sec. 21.50(b), requires the holder of an STC to furnish 
Instructions for Continued Airworthiness, prepared in accordance with 
Sec. 23.1529.
    An STC cannot be used to modify an aircraft without the permission 
of the STC holder. Federal Aviation Administration Notice 8110.69 dated 
June 30, 1997, requires the STC holder to provide the customer 
(installer or airplane owner) with a signed permission statement that 
includes the following:
    (a) Product (aircraft, engine, propeller, or appliance) to be 
altered, inducing serial number of the product;
    (b) The STC number; and
    (c) The person(s) who is being given consent to use the STC.
    The permission statement needs to be maintained as part of the 
aircraft records. The requirement for this permission statement 
originated in the Federal Aviation Authorization Act of 1996 (Public 
Law 104-264). This provision was put into law to try to stop the 
``pirating'' of STC's.
    2. Field Approval. Shoulder harnesses may be installed by a Field 
Approval (FAA Form 337), given by a Flight Standards Aviation Safety 
Inspector. Field Approvals are granted for an individual airplane for 
an alteration that involves little or no engineering. If the 
installation requires structural modification, an engineering approval 
will need to be completed by an ACO. An installation by Field Approval 
would normally be performed when an STC is not available. A Field 
Approval constitutes a change to type design and must meet the same 
regulatory requirements as a STC.
    Advisory Circular 43.13-2A (Reference 3) contains methods, 
techniques, and practices acceptable to the Administrator for use in 
altering civil aircraft. Chapter 9 covers shoulder harness 
installations. Section 3 covers attachment methods. Shoulder harnesses 
installed by Field Approval must meet the same regulatory requirements 
as an STC. Therefore, the applicant should demonstrate by test   9.0 g 
forward load capability. The test load should be 814 pounds for Normal

[[Page 37452]]

Category or 910 pounds for Utility or Acrobatic Category, in accordance 
with AC 23-4.
    Reference 4, Chapter 1, Perform Field Approval of Major Repairs and 
Major Alterations, Section 1, paragraph 5. D(2) states: ``Acceptable 
data that may be used on an individual basis to obtain approval are:
     AC's 43.13-1A and 43.13-2A, as amended: *
     Manufacturer's technical information (e.g., manuals, 
bulletins, kits, etc.)
     FAA Field Approvals''

    Note: Advisory Circular (AC) 43.13-1A has been superseded by AC 
43.13-1B, dated September 8, 1998.

    When using a previous Field Approval as acceptable data, the pull 
test need not be performed if it can be determined that a previous pull 
test applied 814 pounds for Normal Category or 910 pounds for Utility 
or Acrobatic Category. Field Approvals for shoulder harness 
installations should not be done by referring a previous Field Approval 
and deleting the pull test, unless the attachment parts have a Parts 
Manufacturer Approval (PMA), or other FAA approval. If the attachment 
parts have no FAA approval, the strength is not known or assured, since 
they have not been manufactured to an FAA approved quality control 
system.
    Shoulder harness installations attaching to the center of an 
unsupported wing carrythrough tube, or other unsupported member, should 
not be given a Field Approval without a design approval by an Aircraft 
Certification Office. Applying the test load in such cases may cause 
damage or permanent set to the affected structure. Figure 9-16 in AC 
43.13-2A shows typical shoulder harness attachments to tubular members. 
These are all at tube intersections and not at the center of 
unsupported tubes. Figure 9-12 shows a typical wing carrythrough member 
installation. This appears to be in the center of the carrythrough 
member, which is a hat section as found in mental skinned airplanes. 
Part of this figure shows that the hat section is reverted to sheet 
metal skin (which would provide longitudinal support).
    Personnel performing the Field Approval must ensure that both the 
harness and belt are compatable and have a TSO approval.
    Flight Standards Information Bulletin for Airworthiness (FSAW) 98-
03, dated January 30, 1998, (in Order 8300.1) requires that a Field 
Approval include Instructions for Continued Airworthiness prepared (in 
the case of Part 23 airplanes) in accordance with Sec. 23.1529. The 
instructions will be documented on FAA Form 337 and become a part of 
either the aircraft's inspection or maintenance program, or both.
    3. Minor change. 14 CFR Part 21, Sec. 21.93(a), Classification of 
changes in type design states. ``A minor change is one that has no 
appreciable effect on the weight, balance, structural strength, 
reliability, operational characteristics, or other characteristics 
affecting the airworthiness of the product.''
    Information provided to us by the Anchorage ACO indicates that some 
shoulder harness installations that provide known safety improvements 
have been made as a minor change. In these situations, the FAA 
certificated mechanic who installs it makes an entry in the airplane's 
maintenance log.
    One shoulder harness installation kit supplier uses this process 
(no FAA approvals) to install shoulder harnesses in PA-18 airplanes. 
The installation does not require modification of the airframe. The 
front seat harness attaches to the center of the rear wing spar 
carrythrough tube. However, it may not meet the 9.0 g forward inertia 
load required by CAR 3.386. The kit supplier stated that some airplane 
owners that had accidents reported that the harness installation had 
saved their lives. Again, shoulder harness installations should not 
attach to the center of an unsupported wing carrythrough tube or other 
unsupported member, since this type of attachment may pose a risk to 
the structural integrity of the airplane.
    Some shoulder harnesses that have been installed by minor change do 
not have a TSO approval. Technical Standard Order C114, Torso Restraint 
Systems, was issued March 27, 1987, Torso restraint systems 
manufactured before that date did not have to meet the prescribed 
Society of Automotive Engineers standard, Aerospace Standard 8043, 
Aircraft Torso Restraint System, dated March 1986.
    We have studied the circumstances and legality of shoulder 
harnesses installations approved by minor change. An airplane owner may 
wish to install shoulder harnesses, but an STC or prior Field Approval 
is not available for his airplane. In this case, it is not likely that 
an individual airplane owner would apply for an STC or a Field Approval 
because of the costs involved in hiring an engineering consultant to 
perform the structural test and any associated structural analysis. 
Also, there is a possibility that the airframe may be damaged during 
the pull test. In such installations, a pull test would not be 
performed and there is no assurance that the installation will provide 
occupant protection to the ultimate inertia force requirements 
(particularly the 9.0 g forward force) of Sec. 23.561 or CAR 3.386.
    Concerning the legality of shoulder harness installation by minor 
change, we conclude the following: Since CAR 3.386 and 
Sec. 23.561(b)(1) prior to Amendment 23-26 (which became effective 
September 14, 1988) state that ``proper use is made of belts or 
harnesses provided in the design,'' the previously approved seat belt 
installation alone must meet the prescribed ultimate inertia forces.
    Civil Air Regulation 3.652, Functional and installational 
requirements, states: ``Each item of equipment which is essential to 
the safe operation of the airplane shall be found by the Administrator 
to perform adequately the functions for which it is to be used, shall 
function properly when installed and shall be adequately labeled as to 
its identification, function, operational limitations, or any 
combination of these, whichever is applicable.'' Prior to Amendment 23-
20 (which became effective September 1, 1977), Sec. 23.1301 contained 
essentially the same requirement as CAR 3.652. Amendment 23-20 deleted 
the words ``essential to safe operation'' and made the provisions of 
Sec. 23.1301 applicable to ``each item of installed equipment.'' 
Regarding these rules, we conclude that if a shoulder harness is not 
required equipment, it is not essential to the safe operation of the 
airplane. Therefore, CAR 3.652 and Sec. 23.1301, prior to Amendment 23-
20, should not be used as a basis to prohibit shoulder harness 
installation by minor change. These rules should be applied to shoulder 
harness installations made by STC, Field Approval, and minor change, 
but there is no way of enforcing this in the case of installation by 
minor change.
    The mechanic making such installations should consult AC 43.13-2A, 
Chapter 9, for information on restraint systems, effective restraint 
angles, attachment methods, and other details of installation. Only 
harnesses with TSO-C114 approval should be installed.

    Issued in Kansas City, Missouri, on May 31, 2000.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 00-14910 Filed 6-13-00; 8:45 am]
BILLING CODE 4910-13-M