AD 96-25-02

This amendment adopts a new airworthiness directive (AD) that applies to Mitsubishi Heavy Industries, LTD. Models MU-2B-10, -15, -20, -25, -26, -26A, -30, -35, -36, -36A, -40, and -60 airplanes. This action requires revising the Limitations Section, the Procedures Section, and the Master Minimum Equipment List (MMEL) of the Airplane Flight Manual (AFM). These revisions require establishing a minimum airspeed for sustained level flight in icing conditions, limitations for the use of flaps for flight in icing conditions, cues for recognizing hazardous conditions, exiting procedures in icing conditions that are specific to Mitsubishi MU-2B series airplanes, and ensuring the wing illumination and taxi lights are operable prior to flight at night into known or forecast icing conditions. Several fatal accidents, involving certain Mitsubishi MU-2B series airplanes while flying in icing conditions, prompted this action. The actions specified by this AD are intended to prevent operating in conditions that are beyond the capability of the icing protection system, prevent aerodynamic stall at higher than normal airspeed because of icing conditions, and immediately provide the pilot with cues for recognizing hazardous conditions and exiting these conditions, which if not followed, could result in loss of the airplane.

Final rule; request for comments.

96-25-02 MITSUBISHI HEAVY INDUSTRIES, LTD.: Amendment 39-9843; Docket No. 96-CE-61-AD.

Applicability: Models MU-2B-10, -15, -20, -25, -26, -26A, -30, -35, -36, -36A, -40, and -60 airplanes (all serial numbers), certificated in any category.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated in the body of this AD, unless already accomplished.

To prevent operating in conditions that are beyond the capability of the icing protection system, prevent aerodynamic stall at higher than normal airspeed because of icing conditions, and immediately provide the pilot with cues for recognizing hazardous conditions and exiting these conditions, which if not followed, could result in loss of the airplane, accomplish the following:

(a) Within the next 24 hours time-in-service (TIS) after the effective date of this AD, accomplish the requirements of paragraphs (a)(1), (a)(2), and (a)(3) of this AD. Inserting a copy of this AD into the AFM accomplishes this action.

(1) Revise the FAA-approved Airplane Flight Manual (AFM) by incorporating the following into the Limitations Section of the AFM.

LIMITATIONS SECTION
ICING LIMITATIONS

The minimum airspeed for sustained level flight in icing conditions is 180 knots indicated airspeed (IAS).

Sustained flight in icing conditions with flaps extended is prohibited except for approach and landing.

WARNING

Severe icing may result from environmental conditions outside of those for which the airplane is designed. Flight in freezing rain, freezing drizzle, or mixed icing conditions (supercooled liquid water and ice crystals) may result in ice build-up on protected surfaces exceeding the capability of the ice protection system, or may result in ice forming aft of the protected surfaces. This ice may not be shed using the ice protection systems, and may seriously damage the performance and controllability of the airplane. In some cases the ice may appear to be of relatively small proportions. Often the appearance of the ice causing the most severe consequences is glaze ice or a combination of glaze ice and rime ice.

During flight, severe icing conditions that exceed those for which the airplane is certificated shall be determined by the following visual cues.If one or more of these visual cues exist, immediately request priority handling from Air Traffic Control to facilitate a route or an altitude change to exit the icing conditions.

- Airspeed losses greater than 20 knots that are not regained after a boot de-ice cycle.

- Decrease in rate of climb during a constant airspeed climb to 300 feet per minute.

- Unusually extensive ice accreted on the airframe in areas not normally observed to collect ice.

- Accumulation of ice on the lower surface of the wing aft of the protected area.

- Accumulation of ice on the propeller spinner farther aft than normally observed.

- Accumulation of ice on the upper surface of the wing aft of the de-icing boots visible from the pilot's position that is not removed by de-ice boot operation.

Note: Ice accretion beyond the limit of the boots on the upper surface may be visible from the pilot's position as a solid or partial ridge of ice.

Since the autopilot may mask tactile cues that indicate adverse changes in handling characteristics, use of the autopilot is prohibited when any of the visual cues specified above exist, or when unusual lateral or lateral/yaw trim requirements are encountered while the airplane is in icing conditions.

(2) Revise the FAA-approved Airplane Flight Manual (AFM) by incorporating the following into the Master Minimum Equipment List (MMEL) of the AFM. Inserting a copy of this AD into the AFM accomplishes this action.

All icing detection lights (tip tank taxi lights and wing illumination light) must be operable prior to flight into known or forecast icing conditions at night. [NOTE: This supersedes any relief provided by the Master Minimum Equipment List (MMEL).]

(3) Revise the FAA-approved AFM by incorporating the following into the Procedures Section of the AFM. Inserting a copy of this AD into the AFM accomplishes this action.

ABNORMAL PROCEDURES
SEVERE ICING ENCOUNTER

THE FOLLOWING DESCRIBES SOME OF THE WEATHER
CONDITIONS THAT MAY BE CONDUCIVE TO SEVERE
IN-FLIGHT ICING:

- Visible rain at temperatures below 0 degrees Celsius ambient air temperature.

- Droplets that splash or splatter on impact at temperatures below 0 degrees Celsius ambient air temperature.

PROCEDURES FOR EXITING SEVERE ICING ENVIRONMENT:

These procedures are applicable to all flight phases from takeoff to landing. Monitor the ambient air temperature. While severe icing may form at temperatures as cold as -18 degrees Celsius, increased vigilance is warranted at temperatures around freezing with visible moisture present. If the visual cues specified in the Limitations Section of the AFM for identifying severe icing conditions are observed, accomplish the following:

- Immediately request priority handling from Air Traffic Control to facilitate a route or an altitude change to exit the severe icing conditions to avoid extended exposure to flight conditions more severe than those for which the airplane has been certificated.

- Avoid abrupt and excessive maneuvering that may contribute to control difficulties.

- Do not engage the autopilot.

- If the autopilot is engaged, hold the control wheel firmly and disengage the autopilot.

- If an unusual roll response, an uncommanded roll, or an unusual trim is observed, lower the nose (reduce the angle of attack) and allow the airspeed to increase before any reduction in engine power.

- Do not extend flaps during extended operation in icing conditions. Operation with flaps extended can result in a reduced wing angle-of-attack, with the possibility of ice forming on the upper surface further aft of the wing than normal, possibly aft of the protected area.

- If the flaps are extended, do not retract them until the airframe is clear of ice.

- Report these weather conditions to Air Traffic Control.

NOTE 2: Operators must initiate action to notify and ensure that flight crewmembers are apprised of this change.

(b) Incorporating the AFM revisions, as required by this AD, may be performed by the owner/operator holding at least a private pilot certificate as authorized by section 43.7 of the Federal Aviation Regulations (14 CFR 43.7), and must be entered into the aircraft records showing compliance with this AD in accordance with section 43.11 of the Federal Aviation Regulations (14 CFR 43.11).

(c) An alternative method of compliance or adjustment of the compliance time that provides an equivalent level of safety may be approved by the Manager, Small Airplane Directorate, Aircraft Certification Service, 1201 Walnut, suite 900, Kansas City, Missouri 64105. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Small Airplane Directorate.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Small Airplane Directorate.

(d) Copies may be obtained and inspected at the FAA, Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(e) This amendment becomes effective on December 27, 1996.

The FAA has received several fatal accident reports on certain Mitsubishi MU-2B series airplanes. A common factor in these accidents was flying into freezing rain and freezing drizzle without recognizing specific cues and exiting these conditions. Freezing rain and freezing drizzle (also referred to as Supercooled Large Droplets (SLD)) are beyond the capability of the MU-2B series airplane icing protection system. Continued operation in these conditions will cause the airplane to develop unusual ice formations and ice build-up in areas where the airplane does not have ice protection. Ice accretion to this degree can cause increased drag, increased angle of attack, and aerodynamic flow separation resulting in uncontrollable rolling and pitching.

If the airplane is being flown by the autopilot in hazardous icing, the increase in drag will decelerate the airplane into a stall that is well above normal stall speed. There will not be an artificial stall warning by stick shaker. The natural pre-stall buffet will be shorter and stronger, or the airplane may stall with no warning. Stalling on the autopilot can cause a spin or near vertical spiral, neither of which may be recoverable. Using the autopilot while operating in icing conditions could mask the cues of deceleration and the autopilot may cross control the airplane while attempting to maintain altitude and heading. Sideslip at stall can also be induced during the deceleration by improper propeller pitch settings and/or engine fuel control settings that are not in accordance with the manufacturer's specifications.

Since an unsafe condition has been identified that is likely to exist or develop in other Mitsubishi MU-2B series airplanes of the same type design, this AD requires revising the Limitations Section, Procedures Section, and the Master Minimum Equipment List (MMEL) of the Airplane Flight Manual (AFM). These revisions require:

(1) Establishing a minimum airspeed for sustained level flight in icing conditions,

(2) Limited use of flaps while flying in icing conditions,

(3) Recognizing cues for hazardous icing conditions specific to the Mitsubishi Model MU-2B airplane,

(4) Operable wing illumination and taxi lights prior to flight at night into known or forecast icing conditions, and

(5) Exiting procedures for icing conditions.

Since a situation exists for possible uncontrollable flight in severe icing conditions that requires immediate adoption of this regulation, it is found that notice and opportunity for public prior 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 immediate flight safety and, thus, was not preceded by notice and opportunity to 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 should identify the Rules Docket number and be submitted in triplicate to the address specified above. 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 befiled in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 96-CE-61-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 the relationship 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 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 (otherwise, an evaluation is not required). A copy of it, if filed, may be obtained from the Rules Docket.

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 USC 106(g), 40113, 44701.

Section 39.13 - [AMENDED]
2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows: