[Federal Register Volume 62, Number 93 (Wednesday, May 14, 1997)]
[Proposed Rules]
[Pages 26453-26455]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-12575]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-141; Notice No. SC-97-3-NM]


Special Conditions: Boeing Model 737-600/-700/-800; High 
Intensity Radiated Fields (HIRF)/Engine Stoppage

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This notice proposes special conditions for Boeing Model 737-
600/-700/-800 airplanes. These airplanes will have novel and unusual 
design features when compared to the state of technology envisioned in 
the airworthiness standards for transport category airplanes. This 
notice contains the additional safety standards that the Administrator 
considers necessary to establish a level of safety equivalent to that 
provided by the existing airworthiness standards.

DATES: Comments must be received on or before (June 30, 1997.)

ADDRESSES: Comments on these special conditions may be mailed in 
duplicate to: Federal Aviation Administration, Office of the Assistant 
Chief Counsel, Attn: Rules Docket (ANM-7), Docket No. NM-141, 1601 Lind 
Avenue SW., Renton, Washington, 98055-4506; or delivered in duplicate 
to the Office of the Assistant Chief Counsel at the above address. 
Comments must be marked: Docket No. NM-141. Comments may be inspected 
in the Rules Docket weekdays, except Federal holidays, between 7:30 
a.m. and 4:00 p.m.

FOR FURTHER INFORMATION CONTACT: Gregory Dunn, FAA, Standardization 
Branch, ANM-113, Transport Airplane Directorate, Aircraft 
Certification Service, 1601 Lind Avenue SW., Renton, Washington, 
98055-4056; telephone (425) 227-2799; facsimile (425) 227-1149.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of 
these special conditions by submitting such written data, views, or 
arguments as they may desire. Communications should identify the 
regulatory docket or notice number and be submitted in duplicate to the 
address specified above. All communications received on or before the 
closing date for comments will be considered by the Administrator. The 
proposals described in this notice may be changed in light of the 
comments received. All comments submitted will be available in the 
Rules Docket for examination by interested persons, both before and 
after the closing date for comments. A report summarizing each 
substantive public contact with FAA personnel concerning this 
rulemaking will be filed in the docket. Persons wishing the FAA to 
acknowledge receipt of their comments submitted in response to this 
request must submit with those comments a self-addressed, stamped 
postcard on which the following statement is made: ``Comments to Docket 
No. NM-141.'' The postcard will be date stamped and returned to the 
commenter.

Background

    On February 4, 1993, Boeing submitted an application for an 
amendment to Type Certificate A16WE to include the next generation 737 
family of airplanes. Two of these airplanes will have the same length 
as the present 737-300 and 737-500. The third version will be the 
existing 737-400, stretched to add two additional passenger rows. In 
addition, all models will have increased wing size, higher thrust 
engines, and body structure modifications due to increased design 
weights and higher wing and tail loads. The maximum operating altitude 
is to be increased from 37,000 ft. to 41,000 ft. The long range cruise 
speed is increased to 0.78 Mach or better. The range is increased to be 
transcontinental of approximately 2,950 nmi. There is only one engine 
type being offered, which is a derivative of the existing CFM56 
referred to as the CFM56-7. The proposed modification includes the 
installation of digital avionics,

[[Page 26454]]

including Air Data Inertial Reference System (ADIRS) and Common Display 
System (CDS), which are vulnerable to high-intensity radiated fields 
(HIRF) external to the airplane.

Type Certification Basis

    Under the provisions of 14 CFR Sec. 21.101, Boeing must show that 
the Model 737-600/-700/-800 airplanes meet the applicable provisions of 
the regulations incorporated by reference in Type Certificate A16WE, or 
the applicable regulations in effect on the date of application for the 
change to the Model 737. The regulations incorporated by reference in 
the type certificate are commonly referred to as the ``original type 
certification basis.'' The proposed certification basis for the Model 
737-600/-700/-800 airplanes includes 14 CFR part 25, as amended by 
Amendments 25-1 through 25-77, except as indicate below:

----------------------------------------------------------------------------------------------------------------
                                                                                                     At Amdt. 25-
                Section                                            Title                                        
----------------------------------------------------------------------------------------------------------------
25.365................................  Pressurized Compartment Loads..............................            0
25.561................................  Emergency Landing Conditions--General......................            0
25.562................................  Emergency Landing Dynamic Conditions.......................          *64
25.571................................  Damage-tolerance and Fatigue Evaluation of Structure.......       **0,77
25.607................................  Fasteners..................................................       **0,77
25.631................................  Bird Strike Damage.........................................       **0,77
25.699................................  Lift and Drag Device Indicator.............................       **0,77
25.783(f).............................  Doors......................................................      **15,77
25.807(c)(3)..........................  Emergency Exits............................................           15
25.813................................  Emergency Exit Access......................................           45
25.832................................  Cabin Ozone Concentration..................................       **0,77
25.1309...............................  Equipment, Systems and Installations.......................       **0,77
25.1419(c)............................  Ice Protection.............................................      **23,77
----------------------------------------------------------------------------------------------------------------
Boeing has also elected to comply with Amendments 25-78 and 25-80 and portions of Amendments 25-79, 25-84, and  
  25-86.                                                                                                        
*Flight attendant seats will be qualified to Technical Standard Order C127. Passenger and flight deck seats will
  comply with 14 CFR Secs.  25.562 (a), (b), ((c), (1), (2), (3), (4), (7), and (8)).                           
**Applicable to new and significantly modified structure and systems and portions of the airplane affected by   
  these changes. Where two amendment levels are shown for the same paragraph, the number without the asterisk   
  (*) applies to structures, systems, and portions of the airplane which are not new or significantly modified. 
  The structure, systems, and components which comply with the later amendment will be identified in Boeing     
  document D010A001, approved by the FAA and JAA, and referenced on the type certificate data sheet.            
***Boeing provides FAA approved data (Document number D6-49779) to 737 operators to enable the operators to show
  ozone compliance per 14 CFR Sec.  121.578 for their specific route structures.                                
Amendment level ``0'' is the original published version of Part 25 (February 1, 1965).                          

    In addition, the certification basis will be upgraded to include 
the Part 25 complement to any Part 121 amendments adopted prior to the 
certification date and having impact on transport category airplane 
type designs, and the special conditions proposed in this notice.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model 737-600/-700/-800 airplanes must comply with the 
fuel vent and exhaust emission requirements of 14 CFR part 34, and the 
noise certification requirements of 14 CFR part 36.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25, as amended) do not contain adequate or 
appropriate safety standards for the Boeing Model 737-600/-700/-800 
airplanes because of novel or unusual design features, special 
conditions are prescribed under the provisions of 14 CFR Sec. 21.16 to 
establish a level of safety equivalent to that established in the 
regulations.
    Special conditions, as appropriate, are issued in accordance with 
14 CFR Sec. 11.49 after public notice, as required by 14 CFR 
Secs. 11.28 and 11.29, and become part of the type certification basis 
in accordance with 15 CFR Sec. 21.101(b)(2).
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other model that incorporates the same novel or 
unusual design feature, or should any other model already included on 
the same type certificate be modified to incorporate the same novel or 
unusual design feature, the special conditions would also apply to the 
other model under the provisions of 14 CFR Sec. 21.101(a)(1).

Novel or Unusual Design Features

    The Boeing Model 737-600/-700/-800 airplanes will incorporate new 
avionic/electronic systems, such as the Air Data Inertial Reference 
System (ADIRS) and Common Display System (CDS), that perform critical 
functions. These systems may be vulnerable to HIRF external to the 
airplane. In addition, the CFM56-7B engine proposed for the Boeing 737-
700 airplane is a high-bypass ratio fan jet engine that will not seize 
and produce transient torque loads in the same manner that is 
envisioned by current Sec. 25.361(b)(1) related to ``sudden engine 
stoppage.''

Discussion

    There is no specific regulation that addresses protection 
requirements for electrical and electronic systems from HIRF. Increased 
power levels from ground-based radio transmitters and the growing use 
of sensitive electrical and electronic systems to command and control 
airplanes have made it necessary to provide adequate protection.
    To ensure that a level of safety is achieved equivalent to that 
intended by the regulations incorporated by reference, a special 
condition is needed for the Boeing Model 737-600/-700/-800, which 
require that new electrical and electronic systems that perform 
critical functions be designed and installed to preclude component 
damage and interruption of function due to both the direct and indirect 
effects of HIRF.
    For the CFM56-7B engine proposed for the 737-600/-700/-800 
airplanes, the limit engine torque load imposed by sudden engine 
stoppage due to malfunction or structural failure (such as compressor 
jamming) has been specific requirement for transport category airplanes 
since 1957. The size,

[[Page 26455]]

configuration, and failure modes of jet engines has changed 
considerably from those envisioned in 14 CFR Sec. 25.361(b) when the 
engine seizure requirement was first adopted.
    Relative to the engine configurations that existed when the rule 
was developed in 1957, the present generation of engines are 
sufficiently different and novel to justify issuance of a special 
condition to establish appropriate design standards.
    The FAA is developing a new regulation and a new advisory circular 
that will provide more comprehensive criteria for treating engine loads 
resulting from structural failures. In the meantime, a special 
condition is needed to establish appropriate criteria for the Boeing 
737-600/-700/-800 airplanes.

High-Intensity Radiated Fields (HIRF)

    With the trend toward increased power levels from ground-based 
transmitters, plus the advent of space and satellite communications, 
coupled with electronic command and control of the airplane, the 
immunity of critical digital avionics systems to HIRF must be 
established.
    It is not possible to precisely define the HIRF to which the 
airplane will be exposed in service. There is also uncertainty 
concerning the effectiveness of airframe shielding for HIRF. 
Furthermore, coupling of electromagnetic energy to cockpit-installed 
equipment through the cockpit window apertures is undefined. Based on 
surveys and analysis of existing HIRF emitters, an adequate level of 
protection exists when compliance with the HIRF protection special 
condition is shown with either paragraphs 1, or 2 below:
    1. A minimum threat of 100 volts per meter peak electric field 
strength from 10 KHz to 18 GHz.
    a. The threat must be applied to the system elements and their 
associated wiring harnesses without the benefit of airframe shielding.
    b. Demonstration of this level of protection is established through 
system tests and analysis.
    2. A threat external to the airframe of the following field 
strengths for the frequency ranges indicated.

------------------------------------------------------------------------
                                                    Peak  (V/   Average 
                     Frequency                          M)       (V/M)  
------------------------------------------------------------------------
10 KHz-100 KHz....................................         50         50
100 KHz-500 KHz...................................         60         60
500 KHz-2 MHz.....................................         70         70
2 MHz-30 MHz......................................        200        200
30 MHz-100 MHz....................................         30         30
100 MHz-200 MHz...................................        150         33
200 MHz-400 MHz...................................         70         70
400 MHz-700 MHz...................................      4,020        935
700 MHz-1 GHz.....................................      1,700        170
1 GHz-2 GHz.......................................      5,000        990
2 GHz-4 GHz.......................................      6,680        840
4 GHz-6 GHz.......................................      6,850        310
6 GHz-8 GHz.......................................      3,600        670
8 GHz-12 GHz......................................      3,500      1,270
12 GHz-18 GHz.....................................      3,500        360
18 GHz-40 GHz.....................................      2,100        750
------------------------------------------------------------------------

Limit Engine Torque Loads for Sudden Engine Stoppage

    in order to maintain the level of safety envisioned by 
Sec. 25.361(b), more comprehensive criteria are needed for the new 
generation of high bypass engines. The proposed special condition would 
distinguish between the more common events and those rare events 
resulting from structural failures in the engine. For these more rare 
but severe events, the proposed criteria would allow deformation in the 
engine supporting structure in order to absorb the higher energy 
associated with the high bypass engines, while at the same time 
protecting the adjacent primary structure in the wing and fuselage by 
applying an additional factor on these loads.

Applicability

    As discussed above, these special conditions are applicable to the 
Model 737-600/-700/-800 airplanes. Should Boeing Commercial Airplane 
Group apply at a later date for a change to the type certificate to 
include another model incorporating the same novel or unusual design 
feature, the special conditions would apply to that model as well under 
the provisions of 14 CFR Sec. 21.101(a)(1).

Conclusion

    This action affects only certain design features on the Boeing 
Model 737-600/-700/-800 airplanes. It is not a rule of general 
applicability and affects only the applicant who applied to the FAA for 
approval of these features on the airplane.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Proposed Special Conditions

    Accordingly the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for Boeing Model 737-600/-700/-800 airplanes.
    1. Protection from Unwanted Effects of High-Intensity Radiated 
Fields (HIRF). Each electrical and electronic system that performs 
critical functions must be designed and installed to ensure that the 
operation and operational capability of these systems to perform 
critical functions are not adversely affected when the airplane is 
exposed to high intensity radiated fields.
    For the purpose of this special condition, the following definition 
applies: Critical Functions. Functions whose failure would contribute 
to or cause a failure condition that would prevent the continued safe 
flight and landing of the airplane.
    2. Engine Torque Loads. In lieu of compliance with Sec. 25.361(b), 
compliance with the following special condition is proposed:
    (b) For turbine engine installations, the mounts and local 
supporting structure must be designed to withstand each of the 
following:
    (1) The maximum torque load, considered as limit, imposed by:
    (i) sudden deceleration of the engine due to a malfunction that 
could result in a temporary loss of power or thrust capability, and 
that could cause a shutdown due to vibrations; and
    (ii) the maximum acceleration of the engine.
    (2) The maximum torque load, considered as ultimate, imposed by 
sudden engine stoppage due to a structural failure, including fan blade 
failure.
    (3) The load condition defined in paragraph (b)(2) of this section 
is also assumed to act on adjacent airframe structure, such as the wing 
and fuselage. This load condition is multiplied by a factor of 1.25 to 
obtain ultimate loads when the load is applied to the adjacent wing and 
fuselage supporting structure.

    Issued in Renton, Washington, on May 2, 1997.
Stewart R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-12575 Filed 5-13-97; 8:45 am]
BILLING CODE 4910-13-M