[Federal Register Volume 65, Number 8 (Wednesday, January 12, 2000)]
[Rules and Regulations]
[Pages 1758-1760]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-690]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. CE158, Special Condition 23-101-SC]


Special Conditions; Ayres Corporation Model LM-200 Loadmaster; 
Protection of Systems for High Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration (FAA), DOT.


[[Page 1759]]


ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued to Ayres Corporation, One 
Ayres Way, Post Office Box 3090, Albany, Georgia 31706-3090, for a Type 
Certificate for the Ayres Corporation Model LM-200 Loadmaster airplane. 
This airplane will have novel and unusual design features when compared 
to the state of technology envisaged in the applicable airworthiness 
standards. These novel and unusual design features include the 
installation of electronic flight instrument system (EFIS) displays for 
which the applicable regulations do not contain adequate or appropriate 
airworthiness 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 the airworthiness standards applicable to these 
airplanes.

DATES: The effective date of these special conditions is December 23, 
1999. Comments must be received on or before February 11, 2000.

ADDRESSES: Comments may be mailed in duplicate to: Federal Aviation 
Administration, Regional Counsel, ACE-7, Attention: Rules Docket Clerk, 
Docket No. CE158, Room 506, 901 Locust, Kansas City, Missouri 64106. 
All comments must be marked: Docket No. CE158. 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: Ervin Dvorak, Aerospace Engineer, 
Standards Office (ACE-110), Small Airplane Directorate, Aircraft 
Certification Service, Federal Aviation Administration, 901 Locust, 
Room 301, Kansas City, Missouri 64106; telephone (816) 329-4123, or Les 
Taylor, Aerospace Engineer, at the same address, telephone (816) 329-
4134.

SUPPLEMENTARY INFORMATION: The FAA has determined that notice and 
opportunity for prior public comment hereon are impracticable because 
these procedures would significantly delay issuance of the approval 
design 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.

Comments Invited

    Interested persons are invited to submit 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 
special conditions may be changed in light of the comments received. 
All comments received 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. Commenters wishing the FAA to acknowledge receipt of their 
comments submitted in response to this notice must include a self-
addressed, stamped postcard on which the following statement is made: 
``Comments to Docket No. CE158.'' The postcard will be date stamped and 
returned to the commenter.

Background

    On May 6, 1996, Ayres Corporation made an application to the FAA 
for a Type Certificate for their new Ayres Corporation Model LM-200 
Loadmaster airplane with re-application made on March 12, 1999. The 
Ayres Corporation Model LM-200 commuter category airplane has a twin 
turbine LHTEC CTP800-4T powerplant with a maximum takeoff weight of 
19,000 pounds. The airplane incorporates a novel or unusual design 
feature, such as digital avionics consisting of an EFIS, that is 
vulnerable to HIRF external to the airplane.

Type Certification Basis

    Under the provisions of 14 CFR part 21, Sec. 21.17, Ayres 
Corporation must show that the Ayres Corporation Model LM-200 
Loadmaster aircraft meets the applicable provisions of Part 23 as 
amended by Amendment 23-1 through 23-53; Part 34 effective September 
10, 1990, as amended by the amendment in effect on the date of 
certification; Part 36 effective December 1, 1969, as amended by the 
amendment in effect on the date of certification; The Noise Control Act 
of 1972; exemptions, if any; other special conditions applicable to 
this airplane; and the special conditions adopted by this rulemaking 
action.

Discussion

    If the Administrator finds that the applicable airworthiness 
standards (i.e., 14 CFR part 23) do not contain adequate or appropriate 
safety standards because of a novel or unusual design feature of an 
airplane, special conditions are prescribed under the provisions of 
Sec. 21.16. Special conditions, as appropriate, are normally issued in 
accordance with Sec. 11.49, as required by Secs. 11.28 and 11.29(b), 
and become a part of the type certification basis in accordance with 
Sec. 21.17(a)(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, the special conditions would also apply to the 
other model under the provisions of Sec. 21.101(a)(1).

Novel or Unusual Design Features

    The Ayres Corporation Model LM-200 Loadmaster will incorporate 
certain novel and unusual design features into an airplane for which 
the airworthiness standards do not contain adequate or appropriate 
safety standards for protection from the effects of HIRF. These 
features include EFIS, which are susceptible to the HIRF environment, 
that were not envisaged by the existing regulations for this type of 
airplane.

Protection of Systems from High Intensity Radiated Fields (HIRF)

    Recent advances in technology have given rise to the application in 
aircraft designs of advanced electrical and electronic systems that 
perform functions required for continued safe flight and landing. Due 
to the use of sensitive solid state advanced components in analog and 
digital electronics circuits, these advanced systems are readily 
responsive to the transient effects of induced electrical current and 
voltage caused by the HIRF. The HIRF can degrade electronic systems 
performance by damaging components or upsetting system functions.
    Furthermore, the HIRF environment has undergone a transformation 
that was not foreseen when the current requirements were developed. 
Higher energy levels are radiated from transmitters that are used for 
radar, radio, and television. Also, the number of transmitters has 
increased significantly. There is also uncertainty concerning the 
effectiveness of airframe shielding for HIRF. Furthermore, coupling to 
cockpit-installed equipment through the cockpit window apertures is 
undefined.
    The combined effect of the technological advances in airplane 
design and the changing environment has resulted in an increased level 
of

[[Page 1760]]

vulnerability of electrical and electronic systems required for the 
continued safe flight and landing of the airplane. Effective measures 
against the effects of exposure to HIRF must be provided by the design 
and installation of these systems. The accepted maximum energy levels 
in which civilian airplane system installations must be capable of 
operating safely are based on surveys and analysis of existing radio 
frequency emitters. These special conditions require that the airplane 
be evaluated under these energy levels for the protection of the 
electronic system and its associated wiring harness. These external 
threat levels, which are lower than previous required values, are 
believed to represent the worst case to which an airplane would be 
exposed in the operating environment.
    These special conditions require qualification of systems that 
perform critical functions, as installed in aircraft, to the defined 
HIRF environment in paragraph 1 or, as an option to a fixed value using 
laboratory tests, in paragraph 2, as follows:
    (1) The applicant may demonstrate that the operation and 
operational capability of the installed electrical and electronic 
systems that perform critical functions are not adversely affected when 
the aircraft is exposed to the HIRF environment defined below:

------------------------------------------------------------------------
                                                          Field Strength
                                                            (volts per
                       Frequency                              meter)
                                                        ----------------
                                                          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) values.

or,
    (2) The applicant may demonstrate by a system test and analysis 
that the electrical and electronic systems that perform critical 
functions can withstand a minimum threat of 100 volts per meter, peak 
electrical field strength, from 10 kHz to 18 GHz. When using this test 
to show compliance with the HIRF requirements, no credit is given for 
signal attenuation due to installation.
    A preliminary hazard analysis must be performed by the applicant, 
for approval by the FAA, to identify either electrical or electronic 
systems that perform critical functions. The term ``critical'' means 
those functions whose failure would contribute to, or cause, a failure 
condition that would prevent the continued safe flight and landing of 
the airplane. The systems identified by the hazard analysis that 
perform critical functions are candidates for the application of HIRF 
requirements. A system may perform both critical and non-critical 
functions. Primary electronic flight display systems, and their 
associated components, perform critical functions such as attitude, 
altitude, and airspeed indication. The HIRF requirements apply only to 
critical functions.
    Compliance with HIRF requirements may be demonstrated by tests, 
analysis, models, similarity with existing systems, or any combination 
of these. Service experience alone is not acceptable since normal 
flight operations may not include an exposure to the HIRF environment. 
Reliance on a system with similar design features for redundancy as a 
means of protection against the effects of external HIRF is generally 
insufficient since all elements of a redundant system are likely to be 
exposed to the fields concurrently.

Applicability

    As discussed above, these special conditions are applicable to the 
Ayres Corporation Model LM-200 Loadmaster airplane. Should Ayres 
Corporation 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 Sec. 21.101(a)(1).

Conclusion

    This action affects only certain novel or unusual design features 
on one model of airplane. 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 period in several prior instances and has been 
derived without substantive change from those previously issued. It is 
unlikely that prior public comment would result in a significant change 
from the substance contained herein. For this reason, and 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 23

    Aircraft, Aviation safety, Signs and symbols.

Citation

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113 and 44701; 14 CFR part 21, 
Secs.  21.16 and 21.17; and 14 CFR part 11, Secs.  11.28 and 11.49.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for the Ayres Corporation Model 200 
Loadmaster airplane.
    1. Protection of Electrical and Electronic Systems from High 
Intensity Radiated Fields (HIRF). Each system that performs critical 
functions must be designed and installed to ensure that the operations, 
and operational capabilities of these systems to perform critical 
functions, are not adversely affected when the airplane is exposed to 
high intensity radiated electromagnetic fields external to the 
airplane.
    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 Kansas City, Missouri on December 23, 1999.
Marvin Nuss,
Acting Manager, Small Airplane Directorate Aircraft Certification 
Service.
[FR Doc. 00-690 Filed 1-11-00; 8:45 am]
BILLING CODE 4910-13-U