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Airworthiness Directives; Mitsubishi Heavy Industries, Ltd. MU-2B Series Airplanes

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Information about this document as published in the Federal Register.

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Start Preamble

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment adopts a new airworthiness directive (AD) that applies to all Mitsubishi Heavy Industries, Ltd. (Mitsubishi) MU-2B series airplanes. This AD requires modifying the airplanes' operating systems. This AD results from several icing-related incidents and accidents of MU-2B series airplanes, and the Federal Aviation Administration's investigation of the airplane design and pilot's ability to operate in icing conditions. The actions specified by this AD are intended to assist in preventing departure from controlled flight while operating in icing conditions.

DATES:

This AD becomes effective on July 24, 2000.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in the regulation as of July 24, 2000.

ADDRESSES:

You may get the service information referenced in this AD from Mitsubishi Heavy Industries America, Inc., 15303 Dallas Parkway, suite 685, LB-77, Dallas, Texas 75248; telephone: (972) 980-5001; facsimile: (972) 980-5091. You may examine this information at FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 97-CE-21-AD, 901 Locust, Room 506, Kansas City, Missouri 64106; or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

Contact one of the following for questions or more information related to this subject: Mr. John Dow, Aerospace Engineer, Small Airplane Directorate, FAA, 901 Locust, Room 301, Kansas City, Missouri 64106, telephone: (816) 329-4121; facsimile: (816) 426-4090; Mr. Carl Fountain, Aerospace Engineer, Los Angeles Aircraft Certification Office, FAA, 3960 Paramount Blvd., Lakewood, California 90712; telephone: Start Printed Page 30866(562) 627-5222; facsimile: (562) 627-5228; or Ms. Alma Ramirez-Hodge, Aerospace Engineer, FAA, Airplane Certification Office, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone: (817) 222-5147; facsimile: (817) 222-5960.

End Further Info End Preamble Start Supplemental Information

SUPPLEMENTARY INFORMATION:

Events Leading to the Issuance of This AD

What caused this AD?

This AD is the result of several icing-related incidents and accidents of MU-2B series airplanes, and FAA's investigation of both the airplane design and pilot's ability to operate in icing conditions.

Has FAA taken any action to this point?

We issued a proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to all Mitsubishi MU-2B series airplanes. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on May 21, 1998 (63 FR 27872). The NPRM proposed to require you to incorporate the following modifications on the airplane's operating systems:

(1) An ice detection system;

(2) A deice monitoring system;

(3) An automatic autopilot disconnect system and a trim-in-motion alert system;

(4) An engine continuous-duty ignition replacement system; and

(5) An auto-ignition (re-light) system.

The NPRM also proposed to require you to fabricate a placard (using 1/8-inch letters) with the following words and proposed to require you to install this placard within the pilot's clear view:

“Prior to the first flight of each day, a negative torque sensing (NTS) check and a Propeller Feather Valve check must be performed in accordance with the Normal Checklist Procedures.”

Accomplishment of the proposed actions as specified in the NPRM would be required in accordance with:

  • Mitsubishi MU-2 Service Bulletin (SB) No. 217, Revision B, dated November 7, 1996;
  • Mitsubishi MU-2 SB No. 226, which incorporates the following pages:
PagesRevision levelDate
2 through 11, 13 through 24, 27 through 57, and 59 through 93AJanuary 13, 1997.
1, 12, 24, 25, 26, and 58BFebruary 27, 1997.
  • Mitsubishi MU-2 SB No. 231, dated July 2, 1997, Mitsubishi MU-2 SB No. 232, dated July 2, 1997;
  • Mitsubishi MU-2B SB No. 074/74-001, dated October 9, 1991;
  • Test Instrumentation, Inc. Document No. MU2-1001, Rev. C, dated June 15, 1997;
  • Test Instrumentation, Inc. Document No. MU2-4001, Rev. C, dated June 30, 1997;
  • Test Instrumentation, Inc. Document No. MU2-5001, Rev. E., dated May 21, 1997; and
  • Test Instrumentation, Inc. Document No. MU2-6005, dated September 28, 1997.

Was the Public Invited To Comment?

Interested persons were afforded an opportunity to participate in the making of this amendment through the following avenues:

  • Comments to the Docket file in accordance with the procedures specified in the NPRM; and
  • Communications with FAA at a public meeting held in December 1998. Announcement of this public meeting was published in the Federal Register on September, 29, 1998 (63 FR 51865).

Summary of This AD Action

Several icing-related incidents and accidents of Mitsubishi MU-2B series airplanes caused FAA to investigate the airplane design and pilot's ability to operate in icing conditions. The FAA conducted a special certification review, which focused on factual information related to Mitsubishi MU-2B series airplanes involved in icing incidents/accidents. This review was named a Focused Fact Finding Special Certification Review (FFFSCR). This review shows that several accidents and incidents have occurred, and that modifications to the airplane design and additional pilot training may prevent future accidents/incidents. The training issues were addressed in AD 97-20-14, Amendment 39-10150 (62 FR 51594, October 2, 1997).

The following presents whether FAA has included in or excluded from this final rule each action that was proposed in the NPRM:

ModificationIncluded in or excluded from AD
Ice Detection SystemExcluded from AD.
Deice Monitoring SystemIncluded in AD.
Automatic Autopilot Disconnect System and Trim-in-motion Alert SystemIncluded in AD.
Engine Continuous-duty Ignition Replacement SystemExcluded from AD.
Auto-ignition (Re-light System)Included in AD.
Placard to require negative torque sensing (NTS) check and Propeller Feather Valve check as part of the Normal Checklist ProceduresExcluded from AD.

The following presents the actions we proposed in the NPRM, but are excluding from the final rule AD. Also included is a brief description of why we are excluding each one:

1. Ice detection system: The Aviation Rulemaking Advisory Committee (ARAC) recently established an Ice Protection Harmonization Working Group (IPHWG). We are waiting for this group to conclude its study before deciding whether to require an ice detection system on the affected airplanes;

2. Engine continuous-duty ignition system: We determined that the safety aspect of this AD only required the incorporation of the auto-ignition (re-light) system or the engine continuous-duty ignition system. We chose the auto-ignition (re-light system) because it is independent of other pilot actions; and

3. Placard to require negative torque sensing (NTS) check and propeller feather valve check as part of the Normal Checklist Procedures: We determined that the safety aspects of including this information did not outweigh the confusion that could be Start Printed Page 30867generated through the installation of such a large placard on the instrument panel. If our analysis of the continued airworthiness of the affected airplanes shows that this information is necessary, we may initiate further rulemaking to require this information to become part of the Limitations Section of the Airplane Flight Manual (AFM).

The FAA has determined that the modifications required in this AD will correct the unsafe condition identified in the NPRM. We considered all comments received.

The following paragraphs present the comments received on the NPRM and at the public meeting. Also included is FAA's response to each comment, including any changes incorporated into the final rule based on the comments.

Comment Issue No. 1: Pilot Training

What Is the Commenters' Concern?

Many commenters state that inadequate pilot training is the cause of the referenced incidents and accidents of the Mitsubishi MU-2B series airplanes.

What Is FAA's Response to the Concern?

The FAA partially concurs. The FAA has determined that both systems modifications and pilot training are needed to prevent future icing accidents and incidents on the Mitsubishi MU-2B series airplanes. Training issues were addressed in AD 97-20-14, Amendment 39-10150 (62 FR 51594, October 2, 1997). The FAA will continue to monitor the need for future training and will take any appropriate action. This AD addresses the systems modifications.

We are not changing the AD as a result of these comments.

Comment Issue No. 2: Ice Detection System

What Are the Commenters' Concerns?

Numerous commenters object to the incorporation of an ice detection system because:

1. Pilot training is the issue and FAA should focus on providing the appropriate training.

2. The ice detection system will not solve the problem because the Aerospatiale Model ATR-72 airplane involved in the Roselawn accident had an ice detection system installed and a problem still existed.

3. The Roselawn accident with the Aerospatiale Model ATR-72 airplane would not have occurred if the autopilot had remained connected; therefore, the problem with the Mitsubishi MU-2B series airplanes is the autopilot disconnect.

4. The ice detection system is a bad idea because of the excellent visual icing cues of the MU-2B series airplanes and the potential for unrecognized mechanical failure.

5. Based on a commenter's experience in another type of airplane, the ice detection system could provide false positive warnings.

6. Install BF Goodrich Company SMART BOOTS on the affected airplanes. These boots incorporate electronic sensors imbedded into the surface of the vertical stabilizer deicing system; and detect the presence of ice on the surface of the boots, the proper functioning of the boots, and the presence of residual ice. The commenter believes that this system would allow FAA to learn more about the icing environment as it relates to the affected airplanes.

7. An ice detection system is unnecessary because the pilot would use the visual cues to detect ice and could then activate the deicing system. This would make the need for an ice detection system unnecessary.

8. Since the pilot is aware of the ice prior to the ice detection alert, the system is unnecessary, expensive, and a waste of money.

What Is FAA's Response to the Concerns?

The Aviation Rulemaking Advisory Committee (ARAC) has established an Ice Protection Harmonization Working Group (IPHWG). One of the areas this group is currently studying is the safety impact of having ice protection systems incorporated on aircraft. Because this study is ongoing and the IPHWG has not made any recommendations, we have determined not to require the ice detection system in this AD. We will evaluate the information that the IPHWG provides at the conclusion of the study to determine whether we should initiate rulemaking regarding this subject. The Mitsubishi MU-2B series airplanes would be among many aircraft evaluated to determine whether an ice detection system should be incorporated. The AD requirements for the automatic autopilot disconnect system and trim-in-motion alert system provide protection in the event of undetected, dangerous ice accretions. We determined that the modifications required by this AD, including the automatic autopilot disconnect system and trim-in-motion alert system, will provide the operators the necessary warning and equipment to safely operate their airplanes.

We excluded the ice detection system requirement from the AD.

Comment Issue No. 3: Stall Recovery

What Is the Commenter's Concern?

One commenter questions why FAA did not give the option (as a method of accomplishing the AD) of advancing the power (engine torque) to as high as possible (i.e., in excess of 150 percent, which occurred in another type design airplane). This idea is based on the commenter's operating experience in recovering from a stall during an icing-related incident.

What Is FAA's Response to the Concern?

We do not concur. When the engine torque is advanced over 100 percent, the thrust of the propeller may be reduced because of the flow separation of portions of the blade. Instead of an increase in thrust, a reduction in overall thrust is likely. Airflow over the wing in the propwash can be degraded. FAA analysis of the incident that the commenter refers to shows that the airplane recovery occurred when the flaps were extended from the cruise configuration to 15 degrees and when the angle of attack was decreased. The flow over the wing returned, control of the airplane was regained, and the roll attitude stabilized.

We are not changing the AD as a result of this comment.

Comment Issue No. 4: Misuse of the AD Process

What Are the Commenter's Concerns?

One commenter states that (1) AD's are only for defects in design or potential equipment failures; and (2) proceeding with the AD would be a misuse of the AD process.

What Is FAA's Response to the Concerns?

We do not concur. An AD is the vehicle that FAA uses to mandate modifications, inspections, etc., in order to correct an unsafe condition on products (airplanes). That condition could be caused by airplane usage (fatigue), quality control, design, maintenance problems (where the procedures to accomplish such maintenance are not available to the field or the current maintenance procedures are not meeting the necessary safety level), or any other problem. The FAA has determined that an unsafe condition exists in the Mitsubishi MU-2B series airplanes when utilized in icing conditions, and that the airplane modifications specified in the AD are necessary to correct this unsafe condition. We are not using this Start Printed Page 30868AD to improve the level of safety or upgrade the certification level of the Mitsubishi MU-2B airplanes.

We are not changing the AD as a result of these comments.

Comment Issue No. 5: Other Airplane Designs Are More Susceptible to Icing Problems Than the Mitusbishi MU-2B Series Airplanes

What Is the Commenters' Concern?

Several commenters suggest that other airplane models (specifically Raytheon models) are more susceptible to problems while operating in icing conditions than the Mitsubishi MU-2B series airplanes. The commenters believe FAA should withdraw the NPRM for this reason.

What Is FAA's Response to the Concern?

The FAA does not concur that the NPRM should be withdrawn because of the statement that other airplanes are more susceptible to problems while operating in icing conditions. The FAA analyzes the service history and design of each specific airplane make and model type design before taking AD action. Based on the service history and design of the Mitsubishi MU-2B series airplanes, FAA has determined that AD action is necessary. This does not mean that FAA will not take AD action on any other type design airplanes or that the Mitsubishi MU-2B series airplanes are being singled out from other type design airplanes. The FAA will continue to analyze the service history and design of each specific airplane make and model type design, and initiate and implement any appropriate rulemaking action.

We are not changing the AD as a result of these comments.

Comment Issue No. 6: No Evidence That the Affected Airplanes Are Susceptible to Undetectable Ice Accumulation

What Is the Commenter's Concern?

One commenter objects to the stated purpose and provisions specified in the NPRM. In particular, the commenter states that there is no evidence that the Mitsubishi MU-2B series airplanes are susceptible to undetectable ice accumulation.

What Is FAA's Response to the Concern?

The FAA does not concur. In one reported incident of undetectable ice accumulation on one of the affected airplanes, a pilot in 14 CFR part 135 operations experienced a 20-knot decrease in airspeed and a change of positive climb rate to a descent. After examining the airplane surfaces, the crew saw no evidence of ice and instead only saw a shiny appearance on the leading edge of the wing. At this time, the crew operated the deicing boots and witnessed approximately 1-inch of ice shedding from the leading edge of the wing. Airplane performance was restored to the level that existed before the airplane entered the icing condition and before operation of the deicing boots. The bulk of the ice was on the surface of the boots and not the unprotected areas of the fuselage or the propellers. Transparent (clear) ice can result from high liquid water conditions, high airspeed, static air temperatures just below freezing, large droplets, or a combination of any of these conditions. The Mitsubishi MU-2B series airplanes have shown flight characteristics in icing conditions with clear ice formation that are hazardous. These hazards may be attributed to a decreased stall angle, suddenness and the degree of roll upset, a subsequent rapid increase in airspeed, the consequent loss of control after ice accumulation, and difficulty in recovering from any of the above problems. We determined that the modifications required by this AD, including the automatic autopilot disconnect system and trim-in-motion alert system, will provide the operators the necessary warning and equipment to safely operate their airplanes.

We are not changing the AD as a result of this comment.

Comment Issue No. 7: High Incident/Accident Rate for the Mitsubishi MU-2B Series Airplanes

What Is the Commenter's Concern?

One commenter states that, of the 700 Mitsubishi MU-2B series airplanes in service, over 100 have been involved in incidents/accidents.

What Is FAA's Response to the Concern?

The FAA infers from this that the commenter agrees with and supports the AD.

We are not changing the AD as a result of this comment.

Comment Issue No. 8: No AD Justification Based on the FFFSCR

What Is the Commenters' Concern?

Several commenters state that, since the Mitsubishi MU-2B series airplanes “passed all the tests” in the FFFSCR, issuing an AD requiring modifications would be contrary to the FFRSCR. The commenters do not believe FAA should issue the AD because the airplane meets the appropriate certification regulations.

What Is FAA's Response to the Concern?

We do not concur. The FFFSCR specifically addressed flight into icing conditions. The tests were not pass/fail situations. The FFFSCR specifies that several accidents have occurred, and that future accidents/incidents may be prevented by modifications to the airplane design and by additional training to enhance the pilot's ability to manage the airplane in adverse operating conditions.

As discussed previously, an AD is the vehicle that FAA uses to correct unsafe conditions in type design products. A product that meets all certification requirements can still be found to have an unsafe condition that could exist or develop; also, an unsafe condition does not necessarily exist for products that do not meet certification requirements. Whether a product is in compliance with other regulations is unrelated to whether AD action should be taken on that product.

We are not changing the AD as a result of these comments.

Comment Issue No. 9: Unsafe Condition Already Covered by Existing AD's

What Is the Commenter's Concern?

One commenter states that the unsafe condition referenced in this AD is already addressed by current AD's that apply to Mitsubishi MU-2B series airplanes:

  • One that requires training for the pilots of the affected airplanes;
  • One that requires incorporating a minimum speed limitation; and
  • One that addresses actions to take when flying into severe icing.

For this reason, the commenter requests that FAA withdraw the NPRM.

What Is FAA's Response to the Concern?

We do not concur. The current AD's that address severe icing and a minimum speed limitation contain information that applies to many type design airplanes, not just the Mitsubishi MU-2B series airplanes. Pilot training and system modifications are specific to the type design of the Mitsubishi MU-2B series airplanes. The FFFSCR specifies that several accidents have occurred, and that future accidents/incidents may be prevented by modifications to the airplane design and by additional training to enhance the pilot's ability to manage the airplane in adverse operating conditions. We have determined that both systems modifications and pilot training are needed to prevent future icing incidents on the Mitsubishi MU-2B series airplanes. Training issues were addressed in AD 97-20-14, Amendment 39-10150 (62 FR 51594, October 2, 1997). The FAA will continue to monitor the need for future training and Start Printed Page 30869will take appropriate action. This AD addresses the systems modifications.

We are not changing the AD as a result of this comment.

Comment Issue No. 10: Trim-in-Motion

What Is the Commenters' Concern?

Several commenters oppose the incorporation of a trim-in-motion system. The commenters state that the trim-in-motion system will annunciate during normal trim activation and the pilot will hear the trim-in-motion alert continuously and “tune it out.” The commenters would like FAA to eliminate the trim-in-motion system requirement.

What Is FAA's Response to the Concern?

We do not concur. The trim-in-motion system for the MU-2B series airplanes annunciates only after the trim wheel has rotated more than 30 degrees in the nose-up direction when the flaps are retracted. This should eliminate “nuisance alerts”.

We are not changing the AD as a result of these comments.

Comment No. 11: Automatic Autopilot Disconnect

What Are the Commenters' Concerns?

Several commenters oppose the incorporation of an automatic autopilot disconnect. The commenters express the following concerns:

1. The automatic autopilot disconnect is dangerous in that the autopilot could become disconnected in high workload conditions.

2. The Mitsubishi MU-2B series airplane is a one-pilot airplane and the autopilot provides a useful function as a workload reliever.

3. The automatic autopilot disconnect is unnecessary because no accidents have occurred since the AD was issued that required a minimum 180 knot indicated airspeed (KIAS). The commenters would like FAA to eliminate the automatic autopilot disconnect requirement.

4. The autopilot would disconnect at a speed slightly faster than the best rate of climb speed for certain weight and altitude combinations. The commenters state that icing rarely occurs above 25,000 feet. This is the desired altitude in certain weather conditions where the slowest airspeeds are required for the best rate of climb. The commenters believe that a hazardous situation would exist if the pilot were to hand fly the airplane to achieve the best rate of climb instead of utilizing the autopilot.

What Are FAA's Responses to the Concerns?

The following presents FAA's response to each of the concerns regarding the automatic autopilot disconnect:

1. We concur that high workload conditions exist. However, the objective of the automatic autopilot disconnect is to prevent the autopilot from applying nose-up elevator control with pitch trim until the airplane stalls. When implemented, the pilot will be forced to take control of the airplane before the autopilot applies pitch control in the full trimmed nose-up direction. If the autopilot controls the airplane into a stall, then the chance of a recovery is unlikely. The automatic autopilot disconnect would, prior to a stall condition, give control to the pilot and allow detection and prevention of a stall. The automatic autopilot disconnects well below the cruise speed and just above the stall speed.

2. We concur that the Mitsubishi MU-2B series airplane is a single-pilot airplane and the autopilot provides a useful function as a workload reliever. The airplane was certificated without the autopilot and is considered optional equipment. Any pilot of this aircraft should be able to handle situations without the use of the autopilot the same as with the autopilot. As discussed above, the automatic disconnect function activates at a speed that provides increased margin to contaminated stall. This places the pilot in situations where the continued reliance on the autopilot may mask natural stall warnings prior to stall and upset.

3. We do not concur with the commenter that no accidents have occurred since the AD was issued to require a minimum 180 KIAS in icing conditions, and therefore the automatic autopilot disconnect is unnecessary. Since 1993 when the 180 KIAS minimum speed was established, an airplane upset occurred in an accident in Malad City, Utah. Speeds were lower than 180 KIAS.

4. We do not concur that a hazardous situation would exist if the pilot would hand fly the airplane at altitudes above 25,000 feet. Cumulonimbus clouds account for the icing above 25,000 feet. These clouds contain some of the most severe forms of icing conditions. Icing accrued at lower altitudes may easily remain on the airfoil and then the airplane could carry this ice to higher altitudes. As discussed earlier, these airplanes were certificated without the autopilot and the autopilot is considered optional equipment. Any pilot of this aircraft should be able to handle situations without the use of the autopilot the same as with the autopilot.

We are not changing the AD as a result of these comments.

Comment Issue No. 12: Require Either an Auto-ignition (Re-light) System or an Engine Continuous-Duty Ignition Replacement System

What Is the Commenters' Concern?

The commenters believe that requiring either the engine continuous-duty ignition replacement system or the auto-ignition (re-light) system is acceptable. The commenters state that requiring both is redundant and FAA has not provided justification for requiring both.

What Is FAA's Response to the Concern?

We concur that both of these systems should not be required. Based upon the operating record of other airplanes equipped with the auto-ignition (re-light) system, FAA believes that this system is the best for restoring engine power because:

  • Manual selection of the ignition after ice detection depends on the pilot seeing the ice and knowing when the airplane is no longer in a condition conducive to flameout; and
  • Use of the engine continuous-duty ignition replacement system for extended periods of time incurs repetitive igniter replacement costs. The use of the auto-ignition (re-light) system is independent of pilot ice detection. This system is also energized for a short period of time so it incurs less operating cost.

We excluded the requirement of incorporating an engine continuous-duty ignition replacement system.

Comment Issue No. 13: Experienced MU-2B Series Airplanes Operators Were Not Contacted

What Is the Commenters' Concern?

Several commenters question why FAA never contacted “experienced” MU-2B series airplane operators.

What Is FAA's Response to the Concern?

We contacted several MU-2B series airplane operators to seek information on possible upsets or near upsets in icing conditions. Among these were pilots in 14 CFR part 91 and part 135 operations.

We are not changing the AD as a result of these comments. Start Printed Page 30870

Comment Issue No. 14: Specific Accidents Are Unrelated to This AD

What Are the Commenters' Concerns?

Several commenters believe that most of the MU-2B series airplane accidents are unrelated to the subject matter of this AD. The commenters state that FAA should not take AD action because the accidents were related to pilot error or judgement. Some of the commenters state that, when you take the pilot error or judgement issues away, there are not enough accidents to warrant AD action.

What Is FAA's Response to the Concerns?

We do not concur. We determined that human error has not accounted for all accidents and incidents involving MU-2B series airplanes. The type and severity of the icing conditions in these accidents has resulted in fatalities to the occupants of these MU-2B series airplanes. This is because they were in uncontrolled flight into terrain from altitudes of 16,000 feet to 22,000 feet. Accidents are not a prerequisite for issuing an AD. The only prerequisite is an unsafe condition that is likely to exist or develop in other airplanes of the same type design.

We are not changing the AD as a result of these comments.

Comment Issue No. 15: Operation Outside the Design Envelope

What Is the Commenter's Concern?

One commenter states that the AD is not justified because the pilots of the Mitsubishi MU-2B series airplanes are flying outside the design limits of the airplane.

What Is FAA's Response to the Concern?

We do not concur. The FAA does not have evidence of the affected airplanes being flown outside of the design limits up to the moment of loss of control.

We are not changing the AD as a result of this comment.

Comment Issue No. 16: The MU-2B Passed All Tests

What Are the Commenters' Concerns?

One commenter states that AD action is unnecessary because the MU-2B series airplanes passed all the tests during the FFFSCR. Another commenter states that the MU-2B airplanes passed all the tests during the special certification review (SCR) that FAA performed in 1984.

What Is FAA's Response to the Concerns?

We do not concur. The purpose of the 1984 SCR was for the overall aspects of the airplane, and was not specific to icing-related problems. The 1996 FFFSCR specifically addressed flight into icing conditions. The tests during this FFFSCR were not pass/fail situations. The final report of the FFFSCR includes all the findings and conclusions and makes 14 different recommendations, including equipment and training recommendations.

We are not changing the AD as a result of these comments.

Comment Issue No. 17: Power is the Key to Exiting Icing Conditions

What Is the Commenter's Concern?

One commenter states that the one key to exiting icing conditions is power. The commenter requests that FAA focus on increasing power instead of system modifications.

What Is FAA's Response to the Concern?

We do not concur. While power is a key when a pilot immediately exits icing conditions, airfoil lift and stall aerodynamics are most significant in icing conditions. The significant aerodynamic characteristics for the MU-2B series airplanes are the stall angle of attack and lift coefficient with ice accretion. These could lead to increased drag, which may result in an insufficient amount of engine power (thrust) available to exit the icing conditions. The level of thrust necessary to overcome all icing conditions could be more than the MU-2B series airplanes can provide. Nominal changes in propeller effectiveness with ice accretion decrease propeller performance.

We are not changing the AD as a result of this comment.

Comment Issue No. 18: Similar Action Necessary for Other Aircraft

What Is the Commenter's Concern?

One commenter states that the icing accident statistics of other airplanes are higher than the Mitsubishi MU-2B series airplanes. The commenter specifically calls out the statistics for the Cessna Model 421 airplanes. Another commenter states that FAA should require similar actions on the Commander Model 114 airplanes.

What Is FAA's Response to the Concern?

The Cessna Model 421 airplanes and the Commander Model 114 airplanes are a different type design to that of the Mitsubishi MU-2B series airplanes. The FAA looks at the service history and design of each particular aircraft to determine whether an unsafe condition exists or is likely to develop, and AD action is necessary. The FAA will issue an AD if it determines that similar action needs to be taken on any other type design aircraft.

We are not changing the AD as a result of these comments.

Comment Issue No. 19: MU-2B Attracts Financially Weak Operators

What Is the Commenter's Concern?

One commenter states that the MU-2B series airplanes attract operators who do not have the financial strength to properly maintain their aircraft and train their crews. The commenter indicates that this is due to the affected airplanes being market bargains because of factors such as the issuance of the NPRM and the mandatory training AD against the MU-2B series airplanes. The FAA infers that the commenter believes the AD is only necessary to those operators without proper financial resources.

What Is FAA's Response to the Commenter's Concern?

The FAA does not concur. The unsafe condition exists when the airplane is flying in icing conditions. The FAA initiates AD action based only on whether an unsafe condition exists or could develop on type design aircraft. The market value of the affected airplanes or the financial status of the owners/operators of those airplanes does not enter into FAA's decision.

We are not changing the AD as a result of this comment.

Comment Issue No. 20: Severity of Ice Testing

What Is the Commenters' Concern?

Several commenters question the severity of the icing problems found during the tanker testing conducted with the FFFSCR. The commenters state that the AD is not necessary because they believe this testing is the primary justification for the AD.

What Is FAA's Response to the Concern?

We do not concur. The tanker testing was intended to examine only the ice accretion aft of the active portion of the deicing boots. This was where the ice accretion was found on the ATR airplane in the Roselawn accident. During this testing, only small portions of the airplane were exposed to the icing cloud at any particular time because the icing effect could not be accomplished simultaneously on all airplane surfaces located behind the tanker.

The entire natural icing environment cannot be replicated using computational fluid dynamics (CFD). This environment also cannot be sampled during flight testing in natural Start Printed Page 30871icing conditions. Each condition is unique and variable. If you then account for airplane design, the chances for developing the most severe ice shape for any one aerodynamic characteristic is difficult.

This information reveals that neither the testing nor other tools are able to address all possible hazardous conditions on the Mitsubishi MU-2B series airplanes. The FAA has determined that the systems modifications required by this AD will give the pilot the best chance of maintaining control of the airplane in icing conditions.

We are not changing the AD as a result of these comments.

Comment Issue No. 21: Congressional Pressure

What Is the Commenters' Concern?

Several commenters believe that FAA yielded to congressional pressures in conducting the FFFSCR and issuing the NPRM. These commenters state that the FFFSCR was precipitated by a letter from a U.S. congressman relating to an accident in Zwingle, Iowa. The MU-2B series airplane in this accident experienced an uncontained propeller blade failure and then struck a silo. The commenters believe the AD is unnecessary and FAA is taking action because of politics.

What Is FAA's Response to the Concern?

Although it was part of the information we reviewed when deciding to conduct the FFFSCR, the congressional letter was not the determining factor. The FAA was already analyzing the service history of the Mitsubishi MU-2B series airplanes. The decision to issue the NPRM was based on:

  • The conclusions made from the FFFSCR;
  • The review of the affected airplanes' service history; and -
  • The testing and approval of the system modifications included in the NPRM.

Our analysis of the situation does not link the Iowa accident referenced in the congressman's letter to the icing problems of the MU-2B series airplanes.

We are not changing the AD as a result of these comments.

Comment Issue No. 22: AD is an Economic Burden

What Are the Commenters' Concerns?

Several commenters addresss the economic impact caused by this AD and recent AD's against the MU-2B airplanes, including:

1. The AD's are senseless and have gone beyond reason;

2. The apparent bending of the regulatory rules against the MU-2B series airplanes has resulted in higher insurance premiums, higher parts costs, and decreased aircraft values; and

3. The NPRM, if adopted as a final rule, will cost each owner/operator about $27,000.

What Are FAA's Responses to the Concerns?

Our response to each concern follows:

1. We do not concur. The FAA presumes that the commenters are referring to the NPRM and other AD's written against the MU-2B series airplanes. Each AD, including the NPRM, must be justified through the identification of an unsafe condition. The FAA followed all regulatory processes for the AD's, including the NPRM, against the affected airplanes;

2. The FAA does not concur. As stated above, FAA followed all regulatory processes for the AD's, including the NPRM, against the affected airplanes; and

3. The FAA concurs that the NPRM as written would cost approximately $27,000 per airplane. The final rule will actually cost less than that proposed in the NPRM since the requirement for the ice detection system modification and the engine continuous-duty ignition replacement system modification are excluded. The FAA completed a Regulatory Flexibility Analysis on the NPRM. This analysis included the above modifications. The FAA has determined that the safety problems that would exist if this AD was not required outweigh the negative cost impact of this AD upon the public.

We Are not changing the AD as a result of these comments.

Comment Issue No. 23: Product Improvement Modifications

What Are the Commenters' Concerns?

Several commenters state that the installations specified in the NPRM are product improvements and do not address a true unsafe condition. The commenters indicate that Mitsubishi developed the modifications and issued the service bulletins before the FFFSCR.

Another commenter believes that FAA will use this AD as an example in mandating other product improvements in equipment such as global positioning systems (GPS) and stormscopes.

What Is FAA's Response to the Concerns?

We concur that a few of the modifications were developed prior to the FFFSCR. Since FAA had not mandated these modifications through an AD, they could have been considered product improvements at that time. Since that time, FAA performed the FFFSCR; determined that an unsafe condition exists and an AD should be issued; and analyzed the modifications that Mitsubishi developed. Part of addressing the unsafe condition is incorporating the modifications that were developed prior to the FFFSCR. The FAA can only mandate modifications that exist through an AD. An unsafe condition must be demonstrated for any AD action.

We are not changing the AD as a result of these comments.

Comment Issue No. 24: Require a Type Rating and Copilot for Certain Operations

What Are the Commenter's Concerns?

One commenter states that the following should be required when operating MU-2B series airplanes under 14 CFR part 135:

1. The pilot-in-charge should have a type rating; and

2. All Mitsubishi MU-2B series airplanes should have a copilot.

What Are FAA's Responses to the Concerns?

We do not concur with these concerns for the following reasons:

1. During the special certification review performed in 1984, FAA determined that a type rating was not necessary. Nothing has changed to warrant the need for a type rating.

2. Mandating a copilot in 14 CFR part 135 operations is beyond the scope of AD action. The FAA would need to make a rulemaking change to the specific regulation.

We are not changing the AD as a result of these comments.

Comment Issue No. 25: Delete the Requirement for Installing a Placard on the Instrument Panel

What Is the Commenters' Concern?

Several commenters request that the FAA delete the requirement to install a placard to require a negative torque sensing (NTS) check and propeller feather valve check as part of the Normal Checklist Procedures. The commenters state that confusion could be generated through the installation of such a large placard on the instrument panel.

What Is FAA's Response to the Concern?

We concur that a placard is not the best way of accomplishing this action. These checks are currently part of the Start Printed Page 30872Normal Checklist Procedures Section of the AFM. The FAA encourages accomplishment of all actions specified in this section. However, the only mandatory actions in the AFM are those included in the Limitations Section.

Mandating these checks as part of an addition to the Limitations Section of the AFM would impose actions that go beyond the scope of what was already proposed in the NPRM. If our analysis of the continued airworthiness of the affected airplanes shows that it is necessary to mandate these actions, we may initiate further rulemaking to require this information to become part of the Limitations Section of the AFM.

We excluded the placard requirement from the AD.

The FAA's Determination

What Is FAA's Final Determination on This Issue?

After reviewing all available information related to the subject presented above, we have determined that air safety and the public interest require the adoption of the rule as proposed except for the changes described above and minor editorial corrections.

How Do These Changes and Corrections Affect the AD?

We have determined that the addition and minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.

Compliance Time of This AD

What Is the Compliance Time of This AD?

The compliance time of this AD is within the next 12 calendar months after the effective date.

Why Is the Compliance in Calendar Time Instead of Hours Time-in-Service?

We have determined that the compliance time of this AD should be specified in calendar time instead of hours time-in-service. Although the condition addressed by this AD is unsafe while the airplane is in flight, the condition is not a result of repetitive airplane operation. The potential for the unsafe condition occurring is the same on the first flight as it is for subsequent flights. The compliance time of “12 calendar months after the effective date of this AD” will not inadvertently ground airplanes and will assure that all owners/operators of the affected airplanes accomplish this action in a reasonable time period.

Regulatory Flexibility Determination and Analysis

The Regulatory Flexibility Act of 1980 was enacted by Congress to assure that small entities are not unnecessarily or disproportionately burdened by government regulations. This Act establishes “as principle of regulatory issuance that agencies shall endeavor, consistent with the objectives of the rule and of applicable statutes, to fit regulatory and informational requirements to the scale of the businesses, organizations, and governmental jurisdictions subject to regulation.” To achieve this principle, the Act requires agencies to solicit and consider flexible regulatory proposals and to explain the rationale for their actions. The Act covers a wide range of small entities, including small businesses, not-for-profit organizations, and small governmental jurisdictions.

Agencies must perform a review to determine whether a rule will have a “significant economic impact on a substantial number of small entities.” If the determination is that it will, the agency must prepare a Regulatory Flexibility Analysis as described in the Act. However, if after a review for a proposed or final rule, an agency determines that a rule is not expected to have a significant economic impact on a substantial number of small entities, section 605(b) of the Act provides that the head of the agency may so certify and a Regulatory Flexibility Analysis is not required. A statement providing the factual basis for this determination must be included in the Docket file, and the reasoning should be clear.

The FAA has determined that this AD will have a significant economic impact on a substantial number of small entities. After a review of alternatives, as required by section 603(c) of the Act, this AD is the least costly alternative to reduce the possibility of an unsafe condition on Mitsubishi MU-2B series airplanes when operating in icing conditions.

The entities affected by this AD are believed to be mostly in Standard Industrial Classification (SIC) 4522, “Air Transportation, Nonscheduled.” Under the Small Business Administration (SBA), Table of Size Standards, March 1, 1996, an entity in SIC 4522 would be a small business if it has fewer than 1,500 employees.

The U.S. Registered Aircraft Database shows approximately 200 operators of Mitsubishi MU-2B series airplanes in the United States, but that only 13 entities operate 2 or more of these airplanes. Ownership of more than 1 MU-2B series airplane is believed to be limited to 5 percent of the affected aircraft owners. Only one of these operators had 10 or more of these airplanes. The total number of owners operating MU-2B series airplanes is in the range of 320 to 340, and the names of the owners suggest that the majority of these airplanes are operated by small entities. Consequently, this AD is likely to affect a substantial number of small entities.

The initial cost for each owner/operator of an MU-2B series airplane is estimated to be approximately $25,728. Reported usage rates of 32 to 33 hours per month (almost 400 hours per year) indicate that an airplane will be subject to a total of four inspections per year. At a nominal inspection time of 1 workhour per inspection and labor cost of $60 per workhour, the annual inspection costs will be approximately $240 per airplane. These estimates include costs for the associated record keeping. A reasonable range of costs arising from this AD is suggested in the following table:

Cost of capitalRemaining life of aircraft (in years)Annualized costPresent value of total cost
InitialTotal
10%/year20$3,022$3,262$27,771
15%/year204,1104,35027,230
10%/year104,1874,42727,203
15%/year105,1265,36626,933

The remaining life for an affected airplane will depend on the demand for the types of service provided (such as cargo delivery and medical evacuation), as well as the difference in cost between providing this service with the MU-2B series airplanes and the cost of using alternative aircraft or modes of transportation. According to the Start Printed Page 30873manufacturer, detailed inspections show that deterioration of the airframes has been quite small, so that a 20-year life expectancy may be a reasonable presumption. In addition, the manufacturer acknowledged recent instances of retired MU-2B series airplanes being returned to service. These considerations suggest that it is reasonable to presume a relatively long expected life for many of the MU-2B series airplanes, so that the annualized cost per affected aircraft may average less than $5,000.

With an average annual cost per airplane in the range of $3,200 to $5,400 (consistent with 10 to 20 years of remaining life and capital costs of 10 to 15 percent per year), the present value of the total cost will be approximately $27,000 per airplane. The total annualized cost of this AD for the U.S. fleet will be in the range of $1 million (320 × $3,200 = $1,024,000) to $1.8 million (340 × $5,400 = $1,836,000). The present discounted value of total costs imposed by this AD are in the range of $8.6 million to $9.4 million. Market values for the affected airplanes are believed to be in the range of $300,000 to $800,000, depending on the airplane's age, condition, and installed equipment. Therefore, the AD costs will be about 3.5 percent to 9 percent (($27,000 / $800,000) × 100% = 3.5% to ($27,000 / $300,000) × 100% = 9%) of the market value of the airplane. Because the costs imposed by this AD will be proportionately higher for less expensive airplanes, it is likely that they will also be proportionately higher for smaller, less financially strong operators than for larger operators.

In developing the Regulatory Flexibility Analysis, several alternatives to this AD were considered. The alternatives included:

Option No. 1

Take no action, including not issuing this AD.

The FAA's Position on Option No. 1: Taking no action will permit the continuation of current conditions that could result in a repeat of icing-related accidents similar to those that have occurred over the past 10 years.

Option No. 2

Require additional training.

The FAA's Position on Option No. 2: The FAA addressed the training issue in AD 97-20-14, Amendment 39-39-10150 (62 FR 51594). This AD requires periodic training for the pilots and crew flying any Mitsubishi MU-2 series airplane. The training provides information relative to flight into possible or forecast icing conditions. This training should assist in reducing future ice-related accidents for the affected airplanes.

Option No. 3

Issue AD action to restrict the MU-2B series airplanes operators from flight into known or suspected icing conditions.

The FAA's Position on Option No. 3: The FAA has determined that restricting flight into known or suspected icing conditions will not eliminate inadvertent encounters with icing conditions. Such restrictions may have little effect on flying into unforecast icing conditions with inoperable anti-ice equipment and insufficient flight planning. Unknown forecast conditions and insufficient flight planning contributed to two of the accidents (and 13 of the 14 fatalities) cited. In addition, such a restriction will impose costs on owners/operators because the airplanes will be prevented from making flights, despite being outfitted with anti-ice equipment.

Option No. 4

Require the actions in this AD.

The FAA's Position on Option No. 4: The FAA has determined that requiring the modifications in this AD will help prevent undetected failure conditions and provide a timely warning prior to upset. This warning will enable the pilot to manually control the airplane before an unsafe condition develops.

The FAA has determined that this AD is likely to have benefits in excess of costs and is not aware of a less costly alternative that will be likely to address the unsafe condition addressed in this AD.

A copy of the complete Regulatory Flexibility Analysis may be obtained from FAA, Central Region, Office of the Regional Counsel, 901 Locust, Room 506, Kansas City, Missouri .

Regulatory Impact

The regulations adopted herein will not have a substantial direct effect 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, FAA determines that this final rule does not have federalism implications under Executive Order 13132.

The FAA has determined that this action:

(1) Is not a “significant regulatory action” under Executive Order 12866;

(2) Is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and

(3) Could have a significant economic impact on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. We have placed a copy of the draft regulatory evaluation prepared for this action in the Rules Docket. You may obtain a copy of it at the Rules Docket at the location provided under the caption ADDRESSES.

Start List of Subjects

List of Subjects in 14 CFR Part 39

End List of Subjects

Adoption of the Amendment

Start Amendment Part

Accordingly, under the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (

End Amendment Part Start Part

PART 39—AIRWORTHINESS DIRECTIVES

End Part Start Amendment Part

1. The authority citation for part 39 continues to read as follows:

End Amendment Part Start Authority

Authority: 49 U.S.C. 106(g), 40113, 44701.

End Authority
[Amended]
Start Amendment Part

2. FAA amends § 39.13 by adding a new airworthiness directive (AD) to read as follows:

End Amendment Part

2000-09-15 Mitsubishi Heavy Industries, LTD.: Amendment 39-11724; Docket No. 97-CE-21-AD.

(a) What airplanes are affected by this AD? This AD applies to all serial numbers of the following Mitsubishi airplane models, certificated in any category:

MU-2B

MU-2B-10

MU-2B-15

MU-2B-20

MU-2B-25

MU-2B-26

MU-2B-26A

MU-2B-30

MU-2B-35

MU-2B-36

MU-2B-36A

MU-2B-40

MU-2B-60

(b) Who must comply with this AD? Anyone who wishes to operate any of the above airplanes on the U.S. Register must comply with this AD.

(c) What problem does this AD address? The actions specified by this AD are intended to assist in preventing departure from controlled flight while operating in icing conditions.

(d) What actions must I accomplish to address this problem? Within the next 12 calendar months after July 24, 2000 (the effective date of this AD), you must incorporate the following modifications:

(1) Install a pneumatic deice monitoring system. You must use the procedures contained in Test Instrumentation, Inc. Document No. MU2-5001, Rev. E., dated Start Printed Page 30874May 21, 1997; and Mitsubishi MU-2 Service Bulletin (SB) No. 232, dated July 2, 1997.

(2) Install a trim-in-motion alerting system and automatic autopilot disconnect system. Use the procedures contained in Test Instrumentation, Inc. Document No. MU2-1001, Rev. C, dated June 15, 1997; Test Instrumentation, Inc. Document No. MU2-4001, Rev. C, dated June 30, 1997; and Mitsubishi MU-2 SB No. 231, dated July 2, 1997.

(3) Install an auto-ignition (re-light) system. Use the procedures contained in Mitsubishi MU-2 SB No. 226, which incorporates the following pages:

PagesRevision levelDate
2 through 11, 13 through 23, 27 through 57, and 59 through 93AJanuary 13, 1997.
1, 12, 24, 25, 26, and 58BOctober 27, 1997.

(e) Can I comply with this AD in any other way?

(1) You may use an alternative method of compliance or adjust the compliance time if:

(i) Your alternative method of compliance provides an equivalent level of safety; and

(ii) The Manager of one of the following approves your alternative. Submit your request through an FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager.

(A) Los Angeles Aircraft Certification Office, FAA, 3960 Paramount Blvd., Lakewood, California 90712; or

(B) Fort Worth Airplane Certification Office, FAA, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150.

(2) 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 (e)(1) 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 you have not eliminated the unsafe condition, specific actions you propose to address it.

(f) Where can I get information about any already-approved alternative methods of compliance? Contact one of the following:

(1) Small Airplane Directorate, FAA, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone: (816) 329-4121; facsimile: (816) 426-4090;

(2) Los Angeles Aircraft Certification Office, FAA, 3960 Paramount Blvd., Lakewood, California 90712; telephone: (562) 627-5222; facsimile: (562) 627-5228; or

(3) Fort Worth Airplane Certification Office, FAA, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone: (817) 222-5147; facsimile: (817) 222-5960.

(g) What if I need to fly the airplane to another location to comply with this AD? The FAA can issue a special flight permit under sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate your airplane to a location where you can accomplish the requirements of this AD.

(h) Are any service bulletins incorporated into this AD by reference?

(1) You must accomplish the actions required by this AD in accordance with the following:

(i) Mitsubishi MU-2 SB No. 226, which incorporates the following pages:

PagesRevision levelDate
2 through 11, 13 through 23, 27 through 57, and 59 through 93AJanuary 13, 1997.
1, 12, 24, 25, 26, and 58BOctober 27, 1997.

(ii) Mitsubishi MU-2 SB No. 231, dated July 2, 1997;

(iii) Mitsubishi MU-2 SB No. 232, dated July 2, 1997;

(iv) Test Instrumentation, Inc. Document No. MU2-1001, Rev. C, dated June 15, 1997, and attachments;

(v) Test Instrumentation, Inc. Document No. MU2-4001, Rev. C, dated June 30, 1997, and attachments; and

(vi) Test Instrumentation, Inc. Document No. MU2-5001, Rev. E., dated May 21, 1997, and attachments.

(2) The Director of the Federal Register approved this incorporation by reference under 5 U.S.C. 552(a) and 1 CFR part 51.

(3) You can get copies from Mitsubishi Heavy Industries America, Inc., 15303 Dallas Parkway, suite 685, LB-77, Dallas, Texas. You can look at copies at FAA, Central Region, Office of the Regional Counsel, 901 Locust, Room 506, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

(i) When does this amendment become effective? This amendment becomes effective on July 24, 2000.

Start Signature

Issued in Kansas City, Missouri, on May 5, 2000.

Michael Gallagher,

Manager, Small Airplane Directorate, Aircraft Certification Service.

End Signature End Supplemental Information

[FR Doc. 00-11863 Filed 5-12-00; 8:45 am]

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