[Federal Register Volume 61, Number 2 (Wednesday, January 3, 1996)]
[Rules and Regulations]
[Pages 114-115]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-55]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 35

[Docket No. 94-ANE-60; Special Condition No. 35-ANE-02]


Special Conditions; Hamilton Standard Model 568F Propeller

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Hamilton Standard 
Model 568F propeller with electronic propeller and pitch control 
system. The applicable regulations currently do not contain adequate or 
appropriate safety standards for constant speed propellers with 
electronic propeller and pitch control. These special conditions 
contain additional safety standards which the Administrator considers 
necessary to establish a level of safety equivalent to that established 
by the airworthiness standards of part 35 of the Federal Aviation 
Regulations (FAR).

EFFECTIVE DATE: February 2, 1996.

FOR FURTHER INFORMATION CONTACT:
Martin Buckman, Engine and Propeller Standards Staff, ANE-110, Engine 
and Propeller Directorate, Aircraft Certification Service, FAA, New 
England Region, 12 New England Executive Park, Burlington, 
Massachusetts, 01803-5229; telephone (617) 238-7112; fax (617) 238-
7199.

SUPPLEMENTARY INFORMATION:

Background

    On January 26, 1994, Hamilton Standard applied for type 
certification for a new Model 568F propeller. The new propeller would 
use a new electronic propeller and pitch control system in place of the 
primary governor control and synchrophaser unit.
    The existing propeller pitch control is monitored by a governor 
which senses propeller speed and adjusts the pitch to absorb the engine 
power and therefore maintains the propeller at the correct RPM. When 
the primary governor fails, the propeller pitch is controlled by an 
overspeed governor. This type of system is conventional and its 
airworthiness considerations are addressed by part 35 of the FAR's.
    The FAA has determined that special conditions are necessary to 
certificate a Hamilton Standard electronic propeller and pitch control 
in place of the primary governor control and synchrophaser unit for the 
Model 568F propeller. A Notice of Proposed Special Conditions was 
published in the Federal Register on January 20, 1995 (60 FR 4114) for 
the Hamilton Standard Model 568F propeller with electronic propeller 
and pitch control system. This control is designed to operate a 
mechanical and hydraulic interface for the engine and propeller. It 
commands speed governing, synchrophasing and provides beta scheduling. 
Electronic propeller and pitch controls introduce potential failures 
that can result in hazardous conditions. These types of 

[[Page 115]]
failures are not addressed by the requirements of part 35. These 
failures can lead to the following possible hazardous conditions:
    (1) Loss of control of the propeller,
    (2) Instability of a critical function,
    (3) Unwanted change in propeller pitch causing improper thrust/
overspeed, and
    (4) Unwanted action of a critical control function resulting in 
propeller flat pitch or reverse.
    Certification issues that must be addressed are possible loss of 
aircraft-supplied electrical power, aircraft supplied data, failure 
modes, environmental effects including lightning strike sand high 
intensity radiated fields (HIRF) and software design.
    The FAA finds that under the provisions of Sec. 21.16 of the FAR, 
additional safety standards must be applied to the Hamilton Standard 
electronic propeller control for Model 568F propellers to demonstrate 
that it is capable of acceptable operation.

Type Certification Basis

    Under the provisions of Sec. 21.17 of the FAR, Hamilton Standard 
must show that the Model 568F propeller meets the requirements of the 
applicable regulations in effect on the date of the application. Those 
FAR's are Sec. 21.21 and part 35, effective February 1, 1965, as 
amended.
    The Administrator finds that the applicable airworthiness 
regulations in part 35, as amended, do not contain adequate or 
appropriate safety standards for the Model 568F propeller. Therefore, 
the Administrator prescribes special conditions under the provisions of 
Sec. 21.16 to establish a level of safety equivalent to that 
established in the regulations.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49 of the FAR's after public notice and opportunity for 
comment, as required by Secs. 11.28 and 11.29(b), and become part of 
the type certification basis in accordance with Sec. 21.101(b)(2).

Discussion of Comments

    Interested persons have been afforded the opportunity to 
participate in the making of these special conditions. Due 
consideration has been given to the comments received.
    One commenter states concern that the term ``unacceptable change'' 
is vague and could lead to multiple interpretations if the term was not 
defined in the special condition.
    The FAA agrees, and the term ``unacceptable change'' has been 
removed from the text and replaced with the term ``hazardous'', which 
is defined in the special condition.
    The commenter also states concern with system redundancy and states 
that FAR 25.1309, its associated Advisory Circular and a Failure Modes 
Effects Analysis should be included in the special conditions.
    The FAA disagrees. The special condition as written in paragraph 
(a)(2) addresses the commenter's concerns by requiring that the 
propeller be designed and constructed so that no single failure or 
malfunction, or probable combination of failures of electrical or 
electronic components of the propeller control system, result in a 
hazardous condition. Also, the propeller manufacturer includes a 
Failure Modes Effects Analysis (FMEA) report as part of the data 
required for propeller certification. This same report is submitted to 
the airframe manufacturer for incorporation into aircraft certification 
documentation to show compliance with FAR 25.1309. Therefore, the 
commenter's concerns are already included in the certification 
documentation and a special condition is not needed.
    After careful review of the available data, including the comments 
noted above, the FAA determined that air safety and the public interest 
require the adoption of these special conditions with the changes 
discussed previously.

Conclusion

    This action affects only the Hamilton Standard Model 568F propeller 
with a new system of electronic propeller and pitch control. It is not 
a rule of general applicability and affects only the manufacturer who 
applied to the FAA for approval of these features on the propeller.

List of Subjects in 14 CFR Part 35

    Air transportation, Aircraft, Aviation safety, Safety.

    The authority citation for these special conditions continues to 
read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704; 14 CFR 
11.28, 21.16.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Federal Aviation Administration (FAA), the following special conditions 
are issued as part of the type certification basis for the Hamilton 
Standard Model 568F propeller and pitch control system. Considering 
that electronic propeller and pitch control systems introduce potential 
failures that can result in hazardous conditions, the following special 
conditions are issued.
    (a) Each propeller and pitch control system which relies on 
electrical and electronic means for normal operation must:
    (1) Be designed and constructed so that any failure or malfunction 
of aircraft-supplied power or data will not result in a hazardous 
change in propeller pitch setting or prevent continued safe operation 
of the propeller.
    (2) Be designed and constructed so that no single failure or 
malfunction, or probable combination of failures of electrical or 
electronic components, or mechanical and hydraulic interface of the 
propeller control system, result in a hazardous condition.
    (3) Be tested to its environmental limits including transients 
(variations) caused by lightning and high intensity radiated fields 
(HIRF) and demonstrate no adverse effects on the control system 
operation and performance or resultant damage. These tests shall 
include, but not be limited to, the following:
    (i) Lightning strikes, such as multiple-stroke and multiple-burst;
    (ii) Pin-injected tests to appropriate wave forms and levels;
    (iii) HIRF susceptibility tests.
    (4) Be demonstrated by analysis/tests that associated software is 
designed and implemented to prevent errors that would result in a 
hazardous change in propeller pitch or a hazardous condition.
    (5) Be designed and constructed so that a failure or malfunction of 
electrical or electronic components in the propeller control system 
could not prevent safe operation of any remaining propeller that is 
installed on the aircraft.
    (b) For purposes of these special conditions, a hazardous condition 
is considered to exist for each of the following conditions:
    (1) Loss of control of the propeller,
    (2) Instability of a critical function,
    (3) Unwanted change in propeller pitch causing improper thrust/
overspeed, and
    (4) Unwanted action of a critical control function resulting in 
propeller flat pitch or reverse.

    Issued in Burlington, Massachusetts, on December 19, 1995.
James C. Jones,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 96-55 Filed 1-2-96; 8:45 am]
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