[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]


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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.

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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: 
<a href="/cdn-cgi/l/email-protection#3d4f5c535944135a4f545b5b5449557d5b5c5c135a524b"><span class="__cf_email__" data-cfemail="6f1d0e010b1641081d060909061b072f090e0e41080019">[email protected]</span></a>>.

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


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