E6-13995. Special Conditions: Avcon Industries, Inc.; Learjet Model 23 Series Airplanes; High-Intensity Radiated Fields (HIRF)

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final special conditions; request for comments.

SUMMARY:

These special conditions are issued to Avcon Industries, Inc., for the Learjet Model 23 series airplanes modified by Avcon Industries, Inc. This airplane as modified by Avcon Industries, Inc., will have a novel or unusual design feature associated with the installation of a new Reduced Vertical Separation Minimum (RVSM) air data system. 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 that established by the existing airworthiness standards.

DATES:

The effective date of these special conditions is August 17, 2006. Comments must be received on or before September 25, 2006.

ADDRESSES:

Comments on these special conditions may be mailed in duplicate to: Federal Aviation Administration, Regional Counsel, ACE-7, Attention: Rules Docket CE258, 901 Locust, Room 506, Kansas City, Missouri 64106 or delivered in duplicate to the Regional Counsel at the above address. Comments must be marked: CE258. Comments may be inspected in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT:

Ervin Dvorak, Federal Aviation Administration, Aircraft Certification Service, Small Airplane Directorate, ACE-111, 901 Locust, Room 301, Kansas City, Missouri 64106; 816-329-4123; fax [phone].

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 on 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 special condition 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 CE258.” The postcard will be date stamped and returned to the commenter.

Background

On June 26, 2006, Avcon Industries, Inc.; P.O. Box 748; Newton, Kansas 67114, applied for a supplemental type certificate (STC) to modify Learjet Model 23 series airplanes currently approved under Type Certificate (TC) No. A5CE. The Learjet 23 series airplanes are normal category airplanes powered by two turbojet engines, with a maximum takeoff weight of 12,500 pounds. These airplanes operate with a 2-person crew and can seat up to 8 passengers. The proposed modification is the installation of an Innovative Solutions & Support Air Data Display Units and Analog Interface Unit. The avionics/electronics and electrical systems installed in this airplane have the potential to be vulnerable to HIRF external to the airplane.

Type Certification Basis

Under the provisions of § 21.101, Avcon Industries, Inc., must show that the Learjet Model 23 series airplanes, as changed, continue to meet the applicable provisions of the regulations incorporated by reference in Type Certificate No. A5CE, 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 regulations incorporated by reference in the Type Certificate No. A5CE for the Learjet Model 23 series airplanes includes Civil Air Regulations (CAR), part 3, effective May 15, 1956, as amended by Amendments 3-1 through 3-8, plus special conditions set forth in FAA letter to Learjet, dated November 12, 1963, and Amendment No. 1, dated July 31, 1964, and No. 2, dated March 14, 1966, and Exception No. 352 from compliance with CAR 3.74(a)(2) and (3) for ground operation at a maximum weight of 12,750 pounds.

If the Administrator finds that the applicable airworthiness regulations (i.e., part 23, as amended) do not contain adequate or appropriate safety standards for the Learjet Model 23 series airplanes because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16.

In addition to the applicable airworthiness regulations and special conditions, the Learjet Model 23 series 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.

Special conditions, as appropriate, as defined in § 11.19, are issued in accordance with § 11.38, and become part of the type certification basis in accordance with § 21.101.

Special conditions are initially applicable to the model for which they are issued. Should Avcon Industries, Inc., apply for a supplemental type certificate to modify any other model included on TC No. A5CE to incorporate the same or a similar novel or unusual design feature, these special conditions would also apply to the other model under the provisions of § 21.101.

Novel or Unusual Design Features

The Learjet Model 23 series airplanes, as modified by Avcon Industries, Inc., will incorporate an Innovative Solutions & Support Air Data Display Units and Analog Interface Unit. The Innovative Solutions & Support Air Data Display Units and Analog Interface Unit perform critical functions. These systems may be vulnerable to HIRF external to the airplane. The current airworthiness standards of part 23 do not contain adequate or appropriate safety standards for the protection of this equipment from the adverse effects of HIRF. Therefore, we consider this system 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 reference, special conditions are needed for the Learjet Model 23 series airplanes as modified by Avcon Industries, Inc. 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.

Frequency	Field strength (volts per 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 of the 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 Learjet Model 23 series airplanes modified by Avcon Industries, Inc. Should Avcon Industries, Inc., apply later for an STC to modify any other model included on TC No. A5CE to incorporate the same novel or unusual design feature, these special conditions would apply to that model as well under the provisions of § 21.101.

Conclusion

This action affects only certain novel or unusual design features on the Learjet 23 series airplanes modified by Avcon Industries, Inc. 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. 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 21.16 and 21.101; and 14 CFR 11.38 and 11.19.

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 Learjet Model 23 series airplanes modified by Avcon Industries, Inc.

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.

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 August 17, 2006.

David R. Showers,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.