01-9531. Special Conditions: Cessna Aircraft Company Model 500, 550, S550, and 560 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 for Cessna Aircraft Company Model 500, 550, S550, and 560 series airplanes modified by ElectroSonics. These modified airplanes will have a novel or unusual design feature associated with the installation of new dual air data display unit systems that 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 that established by the existing airworthiness standards.

DATES:

The effective date of these special conditions is April 10, 2001. Comments must be received on or before May 18, 2001.

ADDRESSES:

Comments on these special conditions may be mailed in duplicate to: Federal Aviation Administration, Transport Airplane Directorate, Attention: Rules Docket (ANM-114), Docket No. NM188, 1601 Lind Avenue SW., Renton, Washington 98055-4056; or delivered in duplicate to the Transport Airplane Directorate at that address. All comments must be marked: Docket No. NM188. 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:

For information concerning the certification program for Cessna Model 500, 550, S550, and 560 airplanes, contact: Meghan Gordon, Federal Aviation Administration, Standardization Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

For information on the general subject of HIRF, contact: Stephen Slotte, Federal Aviation Administration, Transport airplane Directorate, Airplane and Flight Crew Interface Branch, ANM-111, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA has determined that good cause exists for making these special conditions effective upon issuance; however, interested persons are invited to submit such written data, views, or arguments, as they may desire. Communications should identify the regulatory docket number and be submitted in duplicate to the address specified in the ADDRESSES section, above. All communications received on or before the closing date for comments will be considered by the Administrator. These 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 these special conditions must include a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket No. NM188.” The postcard will be date stamped and returned to the commenter.

Background

On August 10, 2000, ElectroSonics, 4391 International Gateway, Columbus, Ohio, applied for a Supplemental Type Certificate (STC) to modify Cessna Aircraft Company Model 500, 550, S550, and 560 airplanes. These models are certificated under 14 CFR part 25 as (small) transport category airplanes.

• The Cessna Model 500 airplane is powered by two Pratt & Whitney JT15D-1(A/B) turbofans with a maximum takeoff weight of 11,850 pounds. This airplane operates with a two-pilot crew and can hold up to 7 passengers.
• The Cessna Model 550 airplane is powered by two Pratt & Whitney JT15D-4 turbofans with a maximum takeoff weight of 14,100 pounds. This airplane operates with a two-pilot crew and can hold up to 11 passengers.
• The Cessna Model S550 airplane is powered by two Pratt & Whitney JT15D-4B turbofans with a maximum takeoff weight of 15,100 pounds. This airplane operates with a two-pilot crew and can hold up to 11 passengers.
• The Cessna Model 560 airplane is powered by two Pratt & Whitney JT15D-5A/D turbofans with a maximum takeoff weight of 16,300 pounds. This airplane operates with a two-pilot crew and can hold up to 11 passengers.

The modification that is the subject of these special conditions incorporates the installation of Innovative Solutions & Support air data display units (ADDU). The ADDU is a replacement for the existing analog flight instrumentation, and provides additional functional capability and redundancy in the system. The avionics/electronics and electrical systems installed in the subject Cessna airplanes have the potential to be vulnerable to HIRF external to the airplane.

Type Certification Basis

Under the provisions of 14 CFR 21.101, ElectroSonics must show that the Cessna Model 500, 550, S550, and 560 airplanes, as changed, continue to meet the applicable provisions of the regulations incorporated by reference in Type Certificate No. A22CE, 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 included in the certification basis for theses airplanes are as follows:

1. For the Cessna Model 500 Airplane

• 14 CFR part 25, effective February 1, 1965, as amended by Amendments 25-1 through 25-17; §§ 25.934 and 25.1091(d)(2) as amended by Amendments 25-1 through 25-23;
• § 25.1387 as amended by Amendments 25-1 through 25-30;
• §§ 25.1385 and 25.1303(a)(2) as amended by Amendments 25-1 through 25-38;
• Special Conditions 25-25-CE-4; and
• additional requirements listed in the type certificate data sheet that are not relevant to these special conditions.

2. For the Cessna Model 550 Airplane

• 14 CFR part 25 effective February 1, 1965, as amended by Amendments 25-1 through 25-17;
• §§ 25.934 and 25.1091(d)(2) as amended by Amendments 25-1 through 25-23;
• § 25.1401 as amended by Amendments 25-1 through 25-27;
• § 25.1387 as amended by Amendments 25-1 through 25-30;
• §§ 25.1303(a)(2) and 25.1385(c) as amended by Amendments 25-1 through 25-38;
• Special Conditions 25-25-CE-4; and
• additional requirements listed in the type certificate data sheet that are not relevant to these special conditions.

3. For the Cessna Model S550 Airplane

• 14 CFR part 25 effective February 1, 1965, as amended by Amendments 25-1 through 25-17;
• §§ 25.251(e), 25.934, and 25.1091(d)(2) as amended by Amendments 25-1 through 25-23;
• § 25.1401 as amended by Amendments 25-1 through 25-27;
• § 25.1387 as amended by Amendments 25-1 through 25-30;
• §§ 25.787, 25.789, 25.791, 25.853, 25.855, 25.857, and 25.1359 as amended by Amendments 25-1 through 25-32;
• §§ 25.1303(a)(2) and 25.1385(c) as amended by Amendments 25-1 through 25-38;
• Special Conditions 25-25-CE-4; and
• additional requirements listed in the type certificate data sheet that are not relevant to these special conditions.

4. For the Cessna Model 560 Airplane, Serial Numbers 560-0001 through 560-0259

• 14 CFR part 25 effective February 1, 1965, as amended by Amendments 25-1 through 25-17;
• §§ 25.251(e), 25.934, and 25.1091(d)(2) as amended by Amendments 25-1 through 25-23;
• § 25.1401 as amended by Amendments 25-1 through 25-27;
• § 25.1387 as amended by Amendments 25-1 through 25-30;
• §§ 25.787, 25.789, 25.791, 25.853, 25.855, 25.857, and 25.1359 as amended by Amendments 25-1 through 25-32;
• §§ 25.1303(a)(2) and 25.1385(c) as amended by Amendments 25-1 through 25-38;
• Special Conditions 25-25-CE-4; and
• additional requirements listed in the type certificate data sheet that are not relevant to these special conditions.

5. For the Cessna Model 560 Airplane, Serial Numbers 560-0260 Through 560-0538

• 14 CFR part 25 effective February 1, 1965, as amended by Amendments 25-1 through 25-17;
• §§ 25.251(e), 25.934, and 25.1091(d)(2) as amended by Amendments 25-1 through 25-23;
• § 25.1401 as amended by Amendments 25-1 through 25-27;
• § 25.1387 as amended by Amendments 25-1 through 25-30;
• §§ 25.787, 25.789, 25.791, 25.853, 25.855, 25.857, and 25.1359 as amended by Amendments 25-1 through 25-32;
• §§ 25.1303(a)(2) and 25.1385(c) as amended by Amendments 25-1 through 25-38;
• § 25.305 as amended by Amendments 25-1 through 25-54; and
• § 25.1001 as amended by Amendments 25-1 through 25-57.

In addition to the applicable airworthiness regulations and special conditions, these Cessna Model 500, 550, S550, and 560 airplanes must comply with the fuel vent and exhaust emission requirements of part 34 and the noise certification requirements of part 36.

The Effect of Special Conditions on the Type Certification Basis

If the Administrator finds that the applicable airworthiness regulations (i.e., 14 CFR part 25, as amended) do not contain adequate or appropriate safety standards for the Cessna Model 500, 550, S550, and 560 airplanes modified by ElectroSonics because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16.

Special conditions, as defined in § 11.19, are issued in accordance with § 11.38. In accordance with § 21.101(b)(2), the special conditions approved in this document will form an additional part of the type certification basis for these airplanes.

Special conditions are initially applicable to the model for which they are issued. Should ElectroSonics apply at a later date for a supplemental type certificate to modify any other model included on the same type certificate to incorporate the same novel or unusual design feature, these special conditions would also apply to the other model under the provisions of § 21.101(a)(1).

Novel or Unusual Design Features

As noted earlier, the Cessna Model 500, 550, S550, and 560 airplanes modified by ElectroSonics will incorporate a dual electronic primary flight display system that will perform critical functions. This system may be vulnerable to HIRF 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 that is equivalent to that intended by the regulations incorporated by reference, special conditions are needed for the Cessna Model 500, 550, S550, and 560 airplanes modified by ElectroSonics. 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, plus 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, alternatively, paragraph 2., below:

1. A minimum threat of 100 volts rms 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.

or

2. A threat external to the airframe for both of the following field strengths for the frequency ranges indicated. Both peak and average field strength components from Table 1 are to be demonstrated.

Table 1

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 in Table 1 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 Cessna Model 500, 550, S550, and 560 airplanes modified by ElectroSonics. Should ElectroSonics apply at a later date for a supplemental type certificate to modify any other model included on Type Certificate A22CE 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(a)(1).

Conclusion

This action affects only certain novel or unusual design features on the Cessna Model 500, 550, S550, and 560 airplanes modified by ElectroSonics. 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 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 Cessna Aircraft Company Model 500, 550, S550, and 560 series airplanes modified by ElectroSonics:

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 Renton, Washington, on April 10, 2001.

Ali Bahrami,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.