01-1276. Proposed Issuance of Policy Memorandum, Automatic Pilot (Control Wheel Steering) Applications for Part 23/CAR 3 Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of policy statement; request for comments.

SUMMARY:

This document proposes to adopt new policy for certification of normal, utility, acrobatic, and commuter category turbine powered airplanes with automatic pilot (autopilot) (control wheel steering) applications.

DATES:

Comments sent must be received by February 16, 2001.

ADDRESSES:

Send all comments on this proposed policy statement to the individual identified under FOR FURTHER INFORMATION CONTACT.

FOR FURTHER INFORMATION CONTACT:

Sending comments: Bill Marshall, Federal Aviation Administration (FAA), Small Airplane Directorate, Regulations and Policy Branch, ACE-111, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone [phone]; fax [phone]; email: <[e-mail]>.

Asking technical questions: Jon Hannan, FAA, Small Airplane Directorate, Regulations and Policy Branch, ACE-111, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone [phone]; fax [phone]; email: <[e-mail]>.

SUPPLEMENTARY INFORMATION:

Comments Invited

How do I comment on the proposed policy? We invite your comments on this proposed policy statement, ACE-00-23.777-01. You may send whatever written data, views, or arguments you choose. We will consider all comments received by the closing date. We may change the proposals contained in this notice because of the comments received.

Please send comments using the following Internet address: [e-mail]. Comments sent using the Internet must contain “Comments to Policy Statement ACE-00-23.777-01” in the subject line. Writers should format in Microsoft Word 97 or ASCII any file attachments that are sent using the Internet.

Send comments using the following format:

• Organize comments issue-by-issue. For example, discuss a comment about the automatic pilot control panel and a comment about primary flight controls as two separate issues.
• For each issue, state what specific change you are requesting to the proposed policy memorandum.
• Include justification (for example, reasons or data) for each request. If sending your comments using the Internet will cause you extreme hardship, you may send comments using the U.S. Mail, overnight delivery, or facsimile machine. You should mark your comments, “Comments to Policy Statement ACE-00-23.777-01” and send two copies to the above address in the section “FOR FURTHER INFORMATION CONTACT: Sending comments.”

What would be the general effect of this proposed policy? The FAA is presenting this information as a set of guidelines suitable for use. However, we do not intend for this proposed policy to become 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. Also, as with all advisory material, this statement of policy identifies one means, but not the only means, of compliance.

Because this proposed general statement of policy only announces what the FAA seeks to establish as policy, the FAA considers it to be an issue for which public comment is appropriate. Therefore, the FAA requests comments on the following proposed general statement of policy relevant to compliance with § 23.777 of the Federal Aviation Regulations (14 CFR 23.777), and other related regulations.

Background

How does part 23 address the automatic pilot (autopilot) and control wheel steering? The guidance on autopilots used in part 23 airplanes does not specifically address Control Wheel Steering (CWS). Before 1996, CWS was a term used by industry to describe a momentary autopilot interrupt mode. Holding the CWS switch depressed temporarily disconnected the autopilot pitch and roll servos so the airplane could be maneuvered. When the CWS switch was released, the autopilot servos would reengage in the same mode as previously selected.

One minor exception was where an autopilot dropped the vertical axis from the reengagement. But in no case was there a change to a mode that had not been selected.

What recent developments have led to this proposed policy? More recently, there have been some autopilots certificated that could be engaged from a CWS mode switch on the primary flight controls. Additionally, some autopilots were certificated that changed modes from what had been previously selected by depressing the CWS switch.

In some cases, these two installations could lead to inadvertent autopilot engagement or mode changes during critical phases of flight such as liftoff, approach, and landing flare. Inadvertent operation could then lead to confusion and a misperception of a flight control problem or an unintended loss of approach coupling.

Although not specifically pertinent to autopilot controls, § 23.777 of the Federal Aviation Regulations (14 CFR 23.777) requires that each cockpit control “be located . . . to provide convenient operation and to prevent confusion and inadvertent operation.”

The Proposed Policy

In order to comply with the intent of § 23.777 of the Federal Aviation Regulations (14 CFR 23.777) as applicable to automatic pilots (autopilots) installed in part 23 airplanes, autopilots should be evaluated in accordance with the following:

Note:

These characteristics are not applicable to “go around” mode switches which are allowed on throttles.

• The automatic pilot (autopilot) should not be engaged from a switch on the primary flight controls, unless that switch is protected so inadvertent engagement is not possible. Guards covering the switch, which can be moved to provide access to the switch, may be acceptable in some cases.
• Mode changes should not be made by using a switch on the primary flight controls unless some reliable means is provided to prevent unsafe conditions caused by inadvertent mode changes. Refer to § 23.1329(h) of the Federal Aviation Regulations (14 CFR 23.1329(h)).
• The autopilot disengage button should be the color red and be of different design from nearby switches so it is distinguishable by touch.

Issued in Kansas City, Missouri on January 2, 2001.

Marvin R. Nuss,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.