[Federal Register Volume 66, Number 9 (Friday, January 12, 2001)]
[Notices]
[Pages 2949-2951]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-1088]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
[Policy Statement Number ACE-00-23.1155-01]
Issuance of Policy Memorandum, In-Flight Operation of Propellers
at Pitch Settings Below the Flight Regime for 14 CFR Part 23/CAR 3
Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of policy statement.
-----------------------------------------------------------------------
SUMMARY: This document announces an FAA general statement of policy for
certification of normal, utility, acrobatic, and commuter category
turbine powered airplanes with propeller beta mode pitch settings.
FOR FURTHER INFORMATION CONTACT: Randy Griffith, Federal Aviation
Administration, Small Airplane Directorate, Regulations and Policy
Branch, ACE-111, 901 Locust, Room 301, Kansas City, Missouri 64106;
telephone (816) 329-4126; fax (816) 329-4090; email:
[email protected]>.
SUPPLEMENTARY INFORMATION:
Background
This notice announces the following policy statement, ACE-00-
23.1155-01. The purpose of this statement is to address certification
of normal, utility, acrobatic, and commuter category turbine powered
airplanes with propeller beta mode pitch settings.
What Is the General Effect of This Policy?
The FAA is presenting this information as a set of guidelines
suitable for use. However, we do not intend that this policy set up a
binding norm; it does not form a new regulation and the FAA would not
apply or rely on it as a regulation.
The FAA Aircraft Certification Offices (ACO's) and Flight Standards
District Offices (FSDO's) that certify changes in type design and
approve alterations in normal, utility, and acrobatic category
airplanes should try to follow this policy when appropriate. Applicants
should expect the certificating officials would consider this
information when making findings of compliance.
As with all advisory material, this statement of policy identifies
one way, but not the only way, of compliance.
General Discussion of Comments
Has FAA Taken Any Action to This Point?
We issued a notice of policy statement, request for comments. This
proposed policy appeared in the Federal Register on September 1, 2000
(65 FR 53340) and the public comment period closed October 2, 2000.
Was the Public Invited To Comment?
The FAA encouraged interested people to join in making this
proposed policy. We received comments from 5 different commenters.
Commenters included manufacturers and aviation regulatory authorities.
Two commenters did not provide recommendations specific to the
policy. The first agreed with the content. The second provided
information and safety concerns on the possible rulemaking discussed in
the background to the policy. We have noted the second's comment, which
will be considered if we determine that rulemaking should be pursued.
Two commenters recommended that FAA consider for part 23 the
material that was recently prepared for 14 CFR part 25 under the
Powerplant Installation Harmonization Working Group (PPIHWG), as the
same risks and considerations apply. We disagree that the same risks
and considerations for part 25 airplanes directly relate to part
[[Page 2950]]
23 airplanes. The tasking that PPIHWG is working for part 25 airplanes
only considered transport category airplane design and operation. The
design and operation of part 23 airplanes is different from part 25
airplanes. Therefore, direct adoption of part 25 requirements into part
23 without fully evaluating these operational and design differences
could result in lowering the overall safety of part 23 airplanes.
A commenter stated that the proposed policy does not appear to
contain new policy material. We disagree. The proposed policy provides
new criteria, which has not been applied to all part 23/CAR 3
airplanes.
A commenter wrote that they oppose this policy as it proposes to
require new designs to prevent intentional prohibited operations. We
disagree. This policy is not requiring new designs to prevent
intentional prohibited operations, rather the policy is providing
certification considerations for part 23/CAR 3 airplanes that have in-
flight beta capability.
A commenter stated that the policy is for regulations that have not
been issued or approved. We disagree. The rules applicable to this
policy are Sec. 23.1155, which was adopted by Amendment 23-7 effective
September 14, 1969, and 14 CFR part 21, Secs. 21.21(b)(2) and
21.101(b), which were both effective with the basic part 21 dated
February 1, 1965. Therefore, the rules in question are more than 30
years old.
A commenter stated that it is unclear if the section ``Inadvertent
In-Flight Operation'' is directed towards existing type certificated
airplanes or future type certificated airplanes. Further, the commenter
states that the policy can be easily misconstrued as to require a
manufacturer to retrofit airplanes to prohibit in-flight beta
operations. We disagree in that the section specifically states ``For
airplanes with a certification basis before Amendment 23-7 that are
modified to add in-flight beta capability * * *'' Therefore, the
section obviously applies to existing type certificated airplanes that
are modified.
A commenter said the requirement for the flight manual to contain
appropriate operational limitations and consequence statements for in-
flight beta operation could not be mandated by policy. We agree, but
the policy does not mandate such actions. Rather the policy provides
certification guidance, which is reflected when the policy is
finalized.
A commenter stated that the beta lock-out systems discussion is
unclear; specifically, is it directed towards future type certificated
airplanes, existing type certificated airplanes undergoing
modification, or existing type certificated airplanes not undergoing
modification? Also, the commenter requested clarification of which
version of Sec. 23.1155 this section applies; before Amendment 23-7, at
Amendment 23-7, or the proposed Sec. 23.1155. Further, the commenter
states that if the section applies to the proposed Sec. 23.1155, this
policy can not enforce a rule that has not been issued. We agree with
the commenter's first comment. Therefore, the beginning of the second
paragraph of this section was modified to add qualifiers on which
airplanes this section applies. We disagree with the commenter's
remaining comments in that there is only one version of Sec. 23.1155,
the version at Amendment 23-7, which was the amendment level that
adopted the rule. Further, the commenter is incorrect in that this
policy is not proposing a rule change.
A commenter requested clarification on who does a system safety
analysis. We agree and this section was modified by indicating that the
applicant performs the analysis.
The Policy
Background
The National Transportation Safety Board (NTSB) has recommended
rulemaking action to amend 14 CFR part 23 to require a means to prevent
in-flight operation of the propeller at pitch settings below the flight
regime (beta mode). For turbine engine installations, Sec. 23.1155,
added by Amendment 23-7, requires that operation of the propeller
controls for pitch settings below the flight regime have a means to
prevent inadvertent operation. The new requirement recommended by the
NTSB would be fundamentally different from the current Sec. 23.1155.
Unless the airplane is certificated for such use, beta mode could not
occur in-flight, even if intentionally commanded. The Small Airplane
Directorate is initiating an ARAC, Aviation Rulemaking Advisory
Committee, study to determine whether a rulemaking effort should occur.
The FAA has taken actions to address previously certificated
airplanes with in-flight beta capability. A fleet wide review of all
turbopropeller powered transport, normal, utility, acrobatic, and
commuter category airplanes was performed. As a result of the review,
the FAA issued Airworthiness Directives that required applicable Flight
Manuals to include an operational limitation with consequence statement
for in-flight beta operation.
Also, the safety of future type certificated airplanes, with in-
flight beta capability, or currently certificated airplanes, which are
being modified to add an in-flight beta capability, should be assessed.
This assessment should consider both unintentional and intentional
operation of propellers in pitch settings below the flight regime.
Inadvertent In-Flight Operation
Regarding inadvertent operation, as previously mentioned, Amendment
23-7 added a requirement (Sec. 23.1155) that operations of the
propeller controls at pitch settings below the flight regime have a
means to prevent inadvertent operation. For airplanes with a
certification basis before Amendment 23-7 that are modified to add in-
flight beta capability, the provisions of Sec. 21.101(b) should be used
to evaluate the possible unsafe nature of inadvertent operation of
propellers in the beta regime. If it is determined that such operation
is unsafe, the issue may be addressed by showing compliance with
Sec. 23.1155.
The nature of the regulatory requirement provided by Sec. 23.1155
allows a subjective, qualitative evaluation for compliance
determination. The intent is to prevent inadvertent operation in the
beta mode, even if the possibility of inadvertent operation is remote.
If an operation or feature of the design can allow in-flight,
inadvertent placement of the control below the flight regime, the
design does not comply with the regulation. In other words, the design
should be evaluated considering the types of operations that will be
seen in service. Consider items such as hardware wear modes or
maintenance issues that may cause the control to be unintentionally
placed or creep into the beta regime over time.
Intentional In-Flight Operation
On all future type certification projects, the Flight Manuals
should include the appropriate operational limitations and consequence
statement for in-flight beta operation.
Beta Lock-Out Systems
To add an assurance that in-flight beta will not occur, some
airplanes have incorporated lock-out systems. These systems remove the
ability to do this operation in-flight, even if intentionally
commanded. It is important to note that the installation of a beta
lock-out system cannot be used instead of the design requirements of
Sec. 23.1155 compliance. Also, in some cases, propeller beta operation
is used to show compliance with stopping distances in part 23, Subpart
B. Under Subpart B, when means other than wheel brakes are used for
determining stopping distances, the means must be ``safe and
reliable.'' If beta operation is used to show
[[Page 2951]]
compliance with stopping distances, the reliability of a system that
would prevent in-flight beta operation must be such that this
capability, when required, will be available to comply with Subpart B,
and Sec. 21.21(b)(2) or Sec. 21.101(b). With a system safety analysis,
the applicant can determine the required reliability level for the beta
lock-out system based on the hazard level (for example, Sec. 23.1309
compliance).
Therefore, for new type certificated airplanes that have a beta
lock-out system incorporated or previously certificated airplanes that
add a beta lock-out system, the applicant should perform a system
safety analysis of the installation of this system. This analysis
should consider hazards such as the inability to command beta on one
engine on a multiengine airplane. For example, if beta is commanded on
both engines during land roll-out, but only one propeller goes into
beta mode, this might adversely affect ground controllability.
Issued in Kansas City, Missouri on December 22, 2000.
Marvin R. Nuss,
Acting Manager, Small Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 01-1088 Filed 1-11-01; 8:45 am]
BILLING CODE 4910-13-P