AD 94-25-10 SUPERSEDED

This amendment adopts a new airworthiness directive (AD) that is applicable to all Beech Model 400, 400A, 400T, and MU-300-10 airplanes, and all Mitsubishi Model MU-300 airplanes. This action requires a revision to the Airplane Flight Manual that provides pilots with special operating procedures during icing conditions. This amendment is prompted by the results of icing tests, which demonstrated that ice accumulations on the horizontal stabilizer may cause the airplane to pitch down at certain flaps settings. The actions specified in this AD are intended to prevent uncommanded nose-down pitch at certain flap settings during icing conditions.

Final rule; request for comments.

94-25-10 BEECH AIRCRAFT CORPORATION and MITSUBISHI HEAVY INDUSTRIES (MHI), LTD.: Amendment 39-9094. Docket 94-NM-204-AD.

Applicability: All Beech Model 400, 400A, 400T, and MU-300-10 airplanes; and all Mitsubishi Model MU-300 airplanes; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent uncommanded nose-down pitch at flap settings exceeding 10 degrees during icing conditions, accomplish the following:

(a) Within 20 days after the effective date of this AD, revise the Limitations Section and Normal Procedures Section of the FAA-approved Airplane Flight Manual (AFM) to include the following statement. This may be accomplished by inserting a copy of this AD in the AFM.

"ICING CONDITIONS

If icing conditions are encountered during flight, no greater than 10 degrees flaps may be utilized for landing unless the following conditions are met:

1. The icing conditions were encountered for less than 10 minutes, and the Ram Air Temperature (RAT) during such encounter was warmer than -8 degrees C.

OR

2. A RAT of +5 degrees C or warmer is observed during approach and landing.

If either of the above two conditions are met, 30 degrees flaps may be utilized for landing.

Otherwise,
Flaps (landing flaps setting)..........................................................10 degrees
Land Select (LAND SEL) Switch........................................Flaps 10 degrees

For Mitsubishi Model MU-300 airplanes: Use landing data for 10 degrees flaps from Section 6, Performance.

For Beech Model 400, 400A, 400T, or MU-300-10 airplanes: Use landing data for 10 degrees flaps from Appendix 1 of this AD."

(b) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Wichita Aircraft Certification Office (ACO), FAA, Small Airplane Directorate. Operators shall submit their requeststhrough an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Wichita ACO.

NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Wichita ACO.

(c) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(d) This amendment becomes effective on December 28, 1994.

FOR A COPY OF APPENDIX 1 THAT WAS MANUALLY ADDED TO THIS AD, CALL AFS-613 AT (405) 954-6896.

Recently, the FAA has received the results of icing tests conducted on the horizontal stabilizer of a Beech Model 400 airplane. These icing tests, conducted in an icing wind tunnel, demonstrated that, under certain icing conditions, ice (called "runback ice") may accumulate on the horizontal stabilizer aft of the heated element on the leading edge. This accumulated ice caused the test airplane to pitch down at landing flaps set beyond 10 degrees.

After further review and evaluation of the test data, Beech has developed landing performance data for Beech Model MU-300-10 airplanes and Beech Model 400 series airplanes with flaps set at 10 degrees. These landing performance data include landing distances, landing brake energy, and maximum landing weight. (The 10-degree landing flap performance data for Mitsubishi Model MU-300 airplanes were included previously in that airplane's Airplane Flight Manual.)

Subsequent to those icing tests, the FAA received a report of tailplane icing that occurred during a maintenance flight of a Beech Model 400A airplane. The airplane's tail anti-ice/de-ice systems were turned on during this flight, which was only 15 minutes in duration, and the airplane did not go above 4,000 feet elevation. During this flight, when the flaps were extended beyond 20 degrees, the pilot noted some buffet and "stick walking," a pitch control effect in which uncommanded oscillation of the control column caused the airplane to pitch. The pilot was able to land the airplane without incident with the flaps set at 10 degrees. Subsequent investigation revealed that the horizontal stabilizer had accumulations of triangularly-shaped runback ice formations, which were approximately 2 inches in height. These runback ice formations were similar in size and shape to those used in the icing tests.

Such runback ice formations could result in an uncommanded nose-down pitch at flap settings that exceed 10 degrees.

Due tothe similarity in design of the horizontal stabilizers on Beech Model 400A airplanes and Mitsubishi Model MU-300 airplanes, and Beech Model 400, 400T, and MU-300-10 airplanes, the FAA has determined that all of these airplanes may also be subject to the same unsafe condition.

Since an unsafe condition has been identified that is likely to exist or develop on other Beech Model 400, 400A, 400T, and MU-300-10 airplanes and Mitsubishi Model MU-300 airplanes and of the same type design, this AD is being issued to prevent uncommanded nose-down pitch at flap settings that exceed 10 degrees during icing conditions. This AD requires a revision to the Limitations Section and Normal Procedures Section of the FAA-approved Airplane Flight Manual (AFM), that provides pilots with special operating procedures during icing conditions. The landing performance data developed as a result of the icing tests may be used under certain conditions for Beech Model MU-300-10 airplanes and Model 400 seriesairplanes.

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 94-NM-204-AD." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will not have substantial direct effects on the States, on therelationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 94-NM-204-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

The information concerning this amendment may be examined at the FAA, Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Small Airplane Directorate, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Tina L. Miller, Aerospace Engineer, Flight Test Branch, ACE-160W, FAA, Small Airplane Directorate, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas 67209; telephone (316) 946-4168; fax (316) 946-4407.