[Federal Register Volume 70, Number 242 (Monday, December 19, 2005)]
[Rules and Regulations]
[Pages 75002-75004]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-24158]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM337; Special Conditions No. 25-310-SC]


Special Conditions: Raytheon Aircraft Company Model HS.125 
Airplanes; High-Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for a Raytheon Aircraft 
Company Model HS.125 airplane modified by AeroMech Incorporated. This 
modified airplane will have a novel or unusual design feature when 
compared to the state of technology envisioned in the airworthiness 
standards for transport category airplanes. The modification 
incorporates the installation of Innovative Solutions and Support air 
data display units (ADDU). These systems perform critical functions. 
The applicable airworthiness regulations do not contain adequate or 
appropriate safety standards for the protection of these systems from 
the effects of high-intensity radiated fields (HIRF). These special 
conditions contain the additional safety standards that the 
Administrator considers necessary to establish a level of safety 
equivalent to

[[Page 75003]]

that established by the existing airworthiness standards.

DATES: The effective date of these special conditions is December 9, 
2005. Comments must be received on or before January 18, 2006.

ADDRESSES: You must mail two copies of your comments to: Federal 
Aviation Administration, Transport Airplane Directorate, Attention: 
Rules Docket (ANM-113), Docket No. NM337, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. You may deliver two copies to the 
Transport Airplane Directorate at the above address. You must mark your 
comments: Docket No. NM337. You can inspect comments in the Rules 
Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: Greg Dunn, FAA, Airplane and Flight 
Crew Interface Branch, ANM-111, Transport Airplane Directorate, 
Aircraft Certification Service, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2799; facsimile (425) 227-
1320.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA has determined that notice and opportunity for prior public 
comment is impracticable because these procedures would significantly 
delay certification of the airplane and thus delivery of the affected 
aircraft. In addition, the substance of these special conditions has 
been subject to the public comment process in several prior instances 
with no substantive comments received. The FAA therefore finds that 
good cause exists for making these special conditions effective upon 
issuance; however, we invite interested people to take part in this 
rulemaking by sending written comments, data, or views. The most 
helpful comments reference a specific portion of the special 
conditions, explain the reason for any recommended change, and include 
supporting data. We ask that you send us two copies of written 
comments.
    We will file in the docket all comments we receive, as well as a 
report summarizing each substantive public contact with FAA personnel 
concerning these special conditions. You may inspect the docket before 
and after the comment closing date. If you wish to review the docket in 
person, go to the address in the ADDRESSES section of this preamble 
between 7:30 a.m. and 4 p.m., Monday through Friday, except Federal 
holidays.
    We will consider all comments we receive on or before the closing 
date for comments. We will consider comments filed late if it is 
possible to do so without incurring expense or delay. We may change 
these special conditions based on the comments we receive.
    If you want the FAA to acknowledge receipt of your comments on 
these special conditions, include with your comments a pre-addressed, 
stamped postcard on which the docket number appears. We will stamp the 
date on the postcard and mail it back to you.

Background

    On June 6, 2005, AeroMech Incorporated, 1616 Hewitt Avenue, Suite 
312, Everett, Washington 98201, applied for a supplemental type 
certificate (STC) to modify a Raytheon Aircraft Company Model HS.125 
Series 400A airplane. This model is currently approved under Type 
Certificate No. A3EU. The Raytheon Model HS.125 airplane is a small 
transport category airplane powered by two turbine engines. It operates 
with a 2-pilot crew and can seat up to 15 passengers. The modification 
incorporates the installation of Innovative Solutions and Support air 
data display units. The avionics/electronics and electrical systems 
installed in this airplane have the potential to be vulnerable to high-
intensity radiated fields (HIRF) external to the airplane.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, AeroMech Incorporated must 
show that Raytheon Aircraft Company Model HS.125 Series 400A airplane, 
as changed, continues to meet the applicable provisions of the 
regulations incorporated by reference in Type Certificate No. A3EU, or 
the applicable regulations in effect on the date of application for the 
change. The regulations incorporated by reference in the type 
certificate are commonly referred to as the ``original type 
certification basis.'' The certification basis for the Raytheon 
Aircraft Company Model HS.125 Series 400A airplane includes Civil Air 
Regulations (CAR) 10, British Civil Airworthiness Requirements, and 
Special Conditions. This certification is equivalent to CAR 4b dated 
December 1953, Amendment 4b-1 through Amendment 4b-11, exclusive of CAR 
4b.350(e), and includes Special Regulations SR.422B. Type Certificate 
No. A3EU was amended to include HS.125 Series 400A on November 15, 
1968. Compliance over and above certification basis requirements has 
been met with CAR Amendment 4B-12 and Amendment 4B-14. Compliance has 
been established with the special retroactive requirements of 14 CFR 
25.2 as amended by Amendment 25-1 through Amendment 25-20, 14 CFR 21 at 
Amendment 21-27, and 14 CFR 36(1)(c)(2).
    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 Raytheon Model HS.125 Series 400A 
airplane because of a novel or unusual design feature, special 
conditions are prescribed under Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, Raytheon Aircraft Company Model HS.125 Series 400A airplane 
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.
    Special conditions, as defined in 14 CFR 11.19, are issued under 
Sec.  11.38 and become part of the type certification basis under Sec.  
21.101.
    Special conditions are initially applicable to the model for which 
they are issued. Should AeroMech Incorporated apply at a later date for 
a supplemental type certificate to modify any other model included on 
Type Certificate No. A3EU to incorporate the same or similar novel or 
unusual design feature, these special conditions would also apply to 
the other model under Sec.  21.101.

Novel or Unusual Design Features

    As noted earlier, Raytheon Model HS.125 airplane modified by 
AeroMech Incorporated will incorporate Innovative Solutions and Support 
air data display units that will perform critical functions. These 
systems may be vulnerable to high-intensity radiated fields external to 
the airplane. The current airworthiness standards of part 25 do not 
contain adequate or appropriate safety standards for the protection of 
this equipment from the adverse effects of HIRF. Accordingly, this 
system is considered to be a novel or unusual design feature.

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 avionics/electronics and electrical 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

[[Page 75004]]

reference, special conditions are needed for Raytheon Aircraft Company 
Model HS.125 Series 400A airplane modified by AeroMech Incorporated. 
These special conditions require that new avionics/electronics and 
electrical 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.

High-Intensity Radiated Fields (HIRF)

    With the trend toward increased power levels from ground-based 
transmitters, and the advent of space and satellite communications 
coupled with electronic command and control of the airplane, the 
immunity of critical avionics/electronics and electrical 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 paragraph 1 OR 2 below:
    1. A minimum threat of 100 volts rms (root-mean-square) per meter 
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 field strengths 
identified in the table below for the frequency ranges indicated. Both 
peak and average field strength components from the table are to be 
demonstrated.

------------------------------------------------------------------------
                                                        Field strength
                                                       (volts per meter)
                      Frequency                      -------------------
                                                        Peak     Average
------------------------------------------------------------------------
10 kHz-100 kHz......................................        50        50
100 kHz-500 kHz.....................................        50        50
500 kHz-2 MHz.......................................        50        50
2 MHz-30 MHz........................................       100       100
30 MHz-70 MHz.......................................        50        50
70 MHz-100 MHz......................................        50        50
100 MHz-200 MHz.....................................       100       100
200 MHz-400 MHz.....................................       100       100
400 MHz-700 MHz.....................................       700        50
700 MHz-1 GHz.......................................       700       100
1 GHz-2 GHz.........................................      2000       200
2 GHz-4 GHz.........................................      3000       200
4 GHz-6 GHz.........................................      3000       200
6 GHz-8 GHz.........................................      1000       200
8 GHz-12 GHz........................................      3000       300
12 GHz-18 GHz.......................................      2000       200
18 GHz-40 GHz.......................................       600      200
------------------------------------------------------------------------
The field strengths are expressed in terms of peak root-mean-square
  (rms) over the complete modulation period.

    The threat levels identified above are the result of an FAA review 
of existing studies on the subject of HIRF, in light of the ongoing 
work of the Electromagnetic Effects Harmonization Working Group of the 
Aviation Rulemaking Advisory Committee.

Applicability

    As discussed above, these special conditions are applicable to a 
Raytheon Aircraft Company Model HS.125 Series 400A airplane modified by 
AeroMech Incorporated. Should AeroMech Incorporated apply at a later 
date for a supplemental type certificate to modify any other model 
included on Type Certificate No. A3EU to incorporate the same or 
similar novel or unusual design feature, these special conditions would 
apply to that model as well under Sec.  21.101.

Conclusion

    This action affects only certain novel or unusual design features 
on a Raytheon Aircraft Company Model HS.125 Series 400A airplane 
modified by AeroMech Incorporated. 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.
    The substance of these special conditions has been subjected to the 
notice and comment procedure in several prior instances and has been 
derived without substantive change from those previously issued. 
Because a delay would significantly affect the certification of the 
airplane, which is imminent, the FAA has determined that prior public 
notice and comment are unnecessary and impracticable, and good cause 
exists for adopting these special conditions upon issuance. The FAA is 
requesting comments to allow interested persons to submit views that 
may not have been submitted in response to the prior opportunities for 
comment described above.

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 Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the supplemental type certification basis for the Raytheon Aircraft 
Company Model HS.125 Series 400A airplane modified by AeroMech 
Incorporated.
    1. Protection from Unwanted Effects of 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.
    2. For the purpose of these special conditions, 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.

    Issued in Renton, Washington, on December 9, 2005.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 05-24158 Filed 12-16-05; 8:45 am]
BILLING CODE 4910-13-P