07-5698. Special Conditions: DynCorp International, Supplemental Type Certificate (STC), Project Number ST2902RC-R, Installation of Pratt & Whitney Canada PT6-67D Engine With Full Authority Digital Engine Control (FADEC) on Global Helicopter ...

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final special condition; request for comments.

SUMMARY:

This special condition is issued for Supplemental Type Certificate (STC), Project Number ST2902RC-R, for the installation of a Pratt and Whitney PT6-67D Turbine Engine on Global Helicopter Technology Inc. (GHTI), Restricted Category, U.S. Army military surplus helicopters, Model UH-1H, type certificated under type certificate (TC) R00002RC. The installation of the PT6-67D on the Restricted Category UH-1H will have a novel or unusual design feature associated with the installation of the Full Authority Digital Engine Control (FADEC). The applicable airworthiness regulations do not contain adequate or appropriate safety standards to protect systems that perform critical control functions from the effects of a high-intensity radiated field (HIRF). This special condition contains the additional safety standards that the Administrator considers necessary to ensure that critical control functions of systems will be maintained when exposed to HIRF.

DATES:

The effective date of this special condition is November 7, 2007. We must receive your comments by January 15, 2008.

ADDRESSES:

You must mail two copies of your comments to: Federal Aviation Administration (FAA), Rotorcraft Directorate, Attention: Rules Docket (ASW-111), Docket No. SW015, Fort Worth, Texas 76193-0111. You may deliver two copies to the Rotorcraft Directorate at the above address. You must mark your comments: Docket No. SW015. You can inspect comments in the Rules Docket weekdays, except Federal holidays, between 8:30 a.m. and 4 p.m. The Rules Docket for special conditions is maintained at the Federal Aviation Administration, Rotorcraft Directorate, 2601 Meacham Blvd., Room 448, Fort Worth, Texas 76137.

FOR FURTHER INFORMATION CONTACT:

Tyrone D. Millard, FAA, Rotorcraft Directorate, Rotorcraft Standards Staff, Fort Worth, Texas 76193-0110; telephone [phone], fax [phone].

SUPPLEMENTARY INFORMATION:

The FAA has determined that notice and opportunity for prior public comment hereon are unnecessary because the substance of this special condition has been subject to the public comment process in several prior instances with no substantive comments received. We are satisfied that new comments are unlikely. The FAA therefore finds that good cause exists for making this special condition effective upon issuance.

Comments Invited

We invite interested people to take part in this rulemaking by sending written comments, views, or data. The most helpful comments reference a specific portion of the special condition, explain the reason for any recommended change, and include supporting data.

We will file in the docket all comments we receive, as well as a report summarizing each substantive public contact with FAA personnel about this special condition. You can 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 8:30 a.m. and 4 p.m., Monday through Friday, except Federal holidays. We will consider all comments we receive by the closing date for comments. We will consider comments filed late if it is possible to do so without incurring additional expense or delay. We may change this special condition based on the comments we receive.

If you want us to let you know we received your comments on this special condition, send us 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 January 9, 2007, DynCorp International applied for an STC for the installation of a Pratt & Whitney PT6-67D Turbine Engine on the GHTI, U.S. Army UH-1H, Restricted Category Helicopter, type certificated under Type Certificate R00002RC. This UH-1H Restricted Category helicopter is a utility/heavy lift helicopter with a two-bladed teetering main rotor system. It is to be powered by a single Pratt and Whitney PT6-67D engine that incorporates a full authority digital engine control (FADEC). The maximum gross weight of the aircraft is 9,500 pounds.

Supplemental Type Certification Basis

Under the provisions of 14 CFR 21.101, DynCorp International must show that the Engine Installation meets the applicable provisions of the regulations as listed below:

• 14 CFR part 29 as amended through and including Amendment 29-1, effective August 12, 1965.
• 14 CFR part 29.1529, Instructions for Continued Airworthiness, Amendment Number 20, effective September 11, 1980.

In accordance with 14 CFR part 36.1(a)(4), compliance with the noise requirements was not shown for the aircraft. Therefore, the engine installations under this supplemental type certificate are only eligible for external load operations excepted by § 36.1(a)(4) and defined under § 133.1(b). Any alteration to the aircraft for special purpose not identified above will require further FAA approval and in addition, may require noise testing, flight testing, or a combination of noise and flight testing.

In addition, the certification basis includes an equivalent safety finding pertaining to a limitation associated with repetitive high torque cycle events that is not relevant to this special condition.

If the Administrator finds that the applicable airworthiness regulations do not contain adequate or appropriate safety standards for this STC because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16.

The FAA issues special conditions as defined in § 11.19, and issued in accordance with § 11.38, and they become part of the STC certification basis under § 21.17(a)(2).

Special conditions are initially applicable to the model, the modification, or a combination of the model and the modification for which they are issued. Should this STC be revised to include any other model that incorporates the same novel or unusual design feature, this special condition would also apply to the other model under the provisions of § 21.101.

Novel or Unusual Design Features

The GHTI UH-1H Restricted Category Helicopter with a Pratt & Whitney PT6-67D engine installed will incorporate the following novel or unusual design features: Electrical, electronic, or a combination of electrical and electronic (electrical/electronic) systems, specifically a FADEC, that will be performing critical control functions for the continued safe flight and landing of the helicopter. A FADEC is an electronic device that performs the critical functions of engine control during flight operations.

Discussion

The DynCorp International installation of the PT6-67D in the UH-1H helicopter, at the time of application, was identified as incorporating an electronic FADEC system. After the design is finalized, DynCorp International will provide the FAA with a preliminary hazard analysis. This analysis will identify the critical control functions that are required for safe flight and landing that are performed by the FADEC system.

Recent advances in technology have given rise to the application in aircraft designs of advanced electrical/electronic systems that perform critical control functions. These advanced systems respond to the transient effects of induced electrical current and voltage caused by HIRF incidents on the external surface of the helicopter. These induced transient currents and voltages can degrade the performance of the electrical/electronic systems by damaging the components or by upsetting the systems' functions.

Furthermore, the electromagnetic environment has undergone a transformation not envisioned by the current application of § 29.1309(a). Higher energy levels radiate from operational transmitters currently used for radar, radio, and television. Also, the number of transmitters has increased significantly.

Existing aircraft or alteration certification requirements are inappropriate in view of these technological advances. In addition, the FAA has received reports of some significant safety incidents and accidents involving military aircraft equipped with advanced electrical/electronic systems when they were exposed to electromagnetic radiation.

The combined effects of the technological advances in helicopter design and the changing environment have resulted in an increased level of vulnerability of the electrical/electronic systems required for the continued safe flight and landing of the helicopter. The design and installation of these systems will provide effective measures to protect this engine installation on this helicopter against the adverse effects of exposure to HIRF. The following primary factors contributed to the current conditions: (1) Increased use of sensitive electronics that perform critical control functions; (2) reduced electromagnetic shielding afforded helicopter systems by advanced technology airframe materials; (3) adverse service experience of military aircraft using these technologies; and (4) an increase in the number and power of radio frequency emitters and the expected increase in the future.

On July 30, 2007, we issued a final HIRF rule (72 FR 44016, August 6, 2007). This rule provides standards to protect aircraft electrical and electronic systems from HIRFs. It was effective September 5, 2007. However, that rule included provisions that provide relief from the new testing requirements for equipment previously certificated under HIRF special conditions issued in accordance with 14 CFR § 21.16. To obtain this relief, the applicant must be able to—

(1) Provide evidence that the system was the subject of HIRF special conditions issued before December 1, 2007;

(2) Show that there have been no system design changes that would invalidate the HIRF immunity characteristics originally demonstrated under the previously issued HIRF special conditions; and

(3) Provide the data used to demonstrate compliance with the HIRF special conditions under which the system was previously approved.

DynCorp's FADEC installation is eligible for this relief provided in 14 CFR § 29.1317(d) of the final HIRF rule. However, to meet their HIRF requirements, they must comply with this Special Condition, which is based on similar, historical HIRF protections requirements.

These special conditions will require the systems that perform critical control functions, as installed in the aircraft, to meet certain standards based on either a defined HIRF environment or a fixed value using laboratory tests.

The applicant may demonstrate that the operation and operational capabilities of the installed electrical/electronic systems that perform critical control functions are not adversely affected when the aircraft is exposed to the defined HIRF test environment. The FAA has determined that the test environment defined in Table 1 is acceptable for critical control functions in helicopters.

The applicant may also demonstrate by a laboratory test that the electrical/electronic systems that perform critical control functions can withstand a peak electromagnetic field strength in a frequency range of 10 KHz to 18 GHz. If a laboratory test is used to show compliance with the defined HIRF environment, no credit will be given for signal attenuation due to installation. A level of 200 volts per meter (v/m) is more appropriate for critical functions during VFR operations. Laboratory test levels are defined according to RTCA/DO-160D Section 20 Category Y (200 v/m and 300 mA). As defined in DO-160D Section 20, the test levels are defined as the peak of the root means squared (rms) envelope. As a minimum, the modulations required for RTCA/DO-160D Section 20 Category Y will be used. Other modulations should be selected as the signal most likely to disrupt the operation of the system under test, based on its design characteristics. For example, flight control systems may be susceptible to 3 Hz square wave modulation while the video signals for electronic display systems may be susceptible to 400 Hz sinusoidal modulation. If the worst-case modulation is unknown or cannot be determined, default modulations may be used. Suggested default values are a 1 KHz sine wave with 80 percent depth of modulation in the frequency range from 10 KHz to 400 MHz and 1 KHz square wave with greater than 90 percent depth of modulation from 400 MHz to 18 GHz. For frequencies where the unmodulated signal would cause deviations from normal operation, several different modulating signals with various waveforms and frequencies should be applied.

Applicants must perform a preliminary hazard analysis to identify electrical/electronic systems that perform critical control functions. The term “critical control” means those functions whose failure would contribute to or cause an unsafe condition that would prevent the continued safe flight and landing of the helicopter. The FADEC system identified by the hazard analysis as performing critical control functions is required to have HIRF protection.

Compliance with HIRF requirements will be demonstrated by tests, analysis models, similarity with existing systems, or a combination of these methods. The two basic options of either testing the FADEC system to the defined environment or laboratory testing may not be combined. The laboratory test allows some frequency areas to be undertested and requires other areas to have some safety margin when compared to the defined environment. The areas required to have some safety margin are those shown, by past testing, to exhibit greater susceptibility to adverse effects from HIRF; and laboratory tests, in general, do not accurately represent the aircraft installation. Service experience alone will not be acceptable since such experience in normal flight operations may not include an exposure to HIRF. Reliance on a system with similar design features for redundancy, as a means of protection against the effects of external HIRF, is generally insufficient because all elements of a redundant system are likely to be concurrently exposed to the radiated fields.

The modulation that represents the signal most likely to disrupt the operation of the system under test, based on its design characteristics should be selected. For example, flight control systems may be susceptible to 3 Hz square wave modulation. If the worst-case modulation is unknown or cannot be determined, default modulations may be used. Suggested default values are a 1 KHz sine wave with 80 percent depth of modulation in the frequency range from 10 KHz to 400 MHz, and 1 KHz square wave with greater than 90 percent depth of modulation from 400 MHz to 18 GHz. For frequencies where the unmodulated signal would cause deviations from normal operation, several different modulating signals with various waveforms and frequencies should be applied.

Acceptable system performance would be attained by demonstrating that the critical control function components of the system under consideration continue to perform their intended function during and after exposure to required electromagnetic fields. Deviations from system specifications may be acceptable but must be independently assessed by the FAA on a case-by-case basis.

Table 1.—Field Strength Volts/Meter

Frequency	Peak	Average
10-100 KHz	150	150
100-500 KHz	200	200
500-2000 KHz	200	200
2-30 MHz	200	200
30-100 MHz	200	200
100-200 MHz	200	200
200-400 MHz	200	200
400-700 MHz	730	200
700-1000 MHz	1400	240
1-2 GHz	5000	250
2-4 GHz	6000	490
4-6 GHz	7200	400
6-8 GHz	1100	170
8-12 GHz	5000	330
12-18 GHz	2000	330
18-40 GHz	1000	420

Applicability

As discussed previously, this special condition is applicable to Supplemental Type Certificate (STC) Project Number ST2902RC-R, for the installation of a Pratt & Whitney PT6-67D turbine engine in GHTI UH-1H military surplus helicopters type certificated under TC R00002RC. Should DynCorp International apply at a later date for a change to the STC to include another model incorporating the same novel or unusual design feature, the special condition would apply to that STC modification as well under the provisions of § 21.101.

Conclusion

This action affects only certain novel or unusual design features associated with this STC project. 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 helicopter.

The substance of this special condition has been subjected to a 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, the FAA has determined that prior public notice and comment are unnecessary, and good cause exists for adopting this special condition 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.

List of Subjects in 14 CFR Parts 21 and 29

• Aircraft
• Air transportation
• Aviation safety
• Rotorcraft
• Safety

The authority citation for this special condition is as follows:

Authority: 42 U.S.C. 7572; 49 U.S.C. 106(g), 40105, 40113, 44701-44702, 44704, 44709, 44711, 44713, 44715, 45303.

The Special Condition

Accordingly, pursuant to the authority delegated to me by the Administrator, the following special condition is issued as part of the supplemental type certification basis for STC Project ST2902RC-R, installation of PT6-67D on Global Helicopter Technology, Inc. (GHTI), Model UH-1H, Restricted Category Helicopters, type certificated under TC R00002RC.

Protection for Electrical and Electronic Systems From High Intensity Radiated Fields.

1. Each system that performs critical control functions must be designed and installed to ensure that the operation and operational capabilities of these critical control functions are not adversely affected when the helicopter is exposed to high intensity radiated fields external to the helicopter.

2. For the purpose of this special condition, critical control functions are defined as those functions, whose failure would contribute to, or cause, an unsafe condition that would prevent the continued safe flight and landing of the aircraft.

Issued in Fort Worth, Texas, on November 7, 2007.

Mark R. Schilling,

Acting Manager, Aircraft Certification Service, Rotorcraft Directorate.