[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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