[Federal Register Volume 63, Number 98 (Thursday, May 21, 1998)]
[Proposed Rules]
[Pages 27872-27876]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-13517]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-CE-21-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to adopt a new airworthiness directive 
(AD) that would apply to certain Mitsubishi Heavy Industries, Ltd. 
(Mitsubishi) MU-2B series airplanes. The proposed action would require 
incorporating several modifications to the operating systems and 
installing a placard with operating limitations within the pilot's 
clear view. Service history of the affected airplanes prompted the FAA 
to examine the design of these airplanes and analyze the ability of the 
pilots of these airplanes to fly and operate in icing conditions. The 
actions specified by the proposed AD are intended to prevent departure 
from controlled flight and to assist the pilot in detecting ice 
accumulation on the airplane when flying in icing conditions that 
exceed the airplane's ice protection capability, which could result in 
possible loss of control of the airplane.

DATES: Comments must be received on or before July 22, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Central Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 97-CE-21-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106. Comments may be inspected at this location 
between 8 a.m. and 4 p.m., Monday through Friday, holidays excepted.
    Service information that applies to the proposed AD may be obtained 
from Mitsubishi Heavy Industries America, Inc., 15303 Dallas Parkway, 
suite 685, LB-77, Dallas, Texas 75248; telephone (972) 980-5001; 
facsimile (972) 980-5091. This information also may be examined at the 
Rules Docket at the address above.

FOR FURTHER INFORMATION CONTACT: Mr. John Dow, Aerospace Engineer, 
Small Airplane Directorate, 1201 Walnut, suite 900, Kansas City, 
Missouri 64106, telephone (816) 426-6934; facsimile (816) 426-2169.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed 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, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed 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 proposal will be filed 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. 97-CE-21-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Central Region, Office of the Regional Counsel, Attention: 
Rules Docket No. 97-CE-21-AD, Room 1558, 601 E. 12th Street, Kansas 
City, Missouri 64106.

Discussion

    Service history of the Mitsubishi MU-2B series airplanes prompted 
the FAA to examine the design of these airplanes and analyze the 
ability of the pilots of these airplanes to fly and operate in icing 
conditions. The FAA recently conducted a special certification review 
(SCR) for the Mitsubishi MU-2B series airplanes. This examination shows 
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. The training issues were 
addressed in AD 97-20-14. Indications are that the pilot is not 
detecting or properly interpreting the visual cues of ice build-up on 
the airframe. The pilots of the airplanes involved in the accidents did 
not exit the icing conditions, but instead, relied on the autopilot to 
fly the airplane. In these accidents, the airplanes stalled while on 
autopilot, which resulted in departure from controlled flight into a 
spin or near vertical spiral until ground contact was made.

Explanation of Departure From Controlled Flight

    Airplanes that fly in these severe icing conditions, although 
infrequently encountered, can accumulate ice formations that increase 
drag quickly and raise stall speeds significantly. Combining these 
elements with a loss of airspeed can cause aerodynamic flow separation 
or stall on one or both wings. This stall can result in an uncontrolled

[[Page 27873]]

rolling or pitching, especially if yawing is present at the stall. 
Heavy ice-induced stalls can occur very suddenly at airspeeds well in 
excess of normal stall speeds, with no artificial warning (stick 
shaker) or natural pre-stall buffet (stick shaker) to advise the pilot 
that the airplane is about to stall. If the pilot has put the airplane 
controls on autopilot, and takes no corrective actions during the ice 
induced slowdown, the autopilot then contributes to the departure from 
controlled flight.
    The certification tests and operation of the MU-2B series airplanes 
reveal that these airplanes have the capability to cope with normal 
icing conditions. However, the FAA's current understanding of freezing 
rain and drizzle, known as supercooled large drops (SLD), shows that 
atmospheric icing conditions exist that exceed the capability of the 
pneumatic ice protection found on turbopropeller airplanes, including 
the MU-2B series airplanes. Flight into SLD, or freezing rain and 
freezing drizzle, can cause ice accretion on and beyond the active 
portion of the de-icing boots, on the upper and lower surfaces of the 
wing, as well as other unprotected surfaces of the airplane. The ice 
that forms beyond the boots cannot be removed. Ice increases drag, 
leading to decreased airspeed, and if level flight is maintained, 
increased angle-of-attack. This evolution can ultimately lead to 
aerodynamic flow separation over the wing, or stall. Ice can also form 
around the engine inlets. The accumulated ice might then loosen and be 
ingested into the engine, interrupt the airflow, and flame out the 
engine at a critical time.

Relevant Service Information

    Mitsubishi has issued the following service bulletins which specify 
procedures that address the concerns in this proposed action.
    <bullet> Test Instrumentation, Inc. Document No. MU2-1001, Rev. C., 
dated June 15, 1997, and Mitsubishi MU-2 Service Bulletin (SB) No. 231, 
dated July 2, 1997: these documents include procedures for 
incorporating an audible trim-in-motion alert system to notify the 
pilot that the trim is trimming nose-up while the autopilot is engaged;
    <bullet> Test Instrumentation, Inc. Document No. MU2-5001, Rev. E., 
dated May 21, 1997, and Mitsubishi MU-2 SB No. 232, dated July 2, 1997: 
these documents include procedures for modifying the existing pneumatic 
de-icing system to assure that both wing and tailplane boots are 
receiving enough inflation pressure when the De-Ice System Annunciation 
is in the ``ON'' position, and circuit breaker modification is made;
    <bullet> Mitsubishi MU-2 SB No. 217, Revision B, dated November 7, 
1996 and Test Instrumentation Inc. Document No. MU2-6005, dated 
September 28, 1997: these documents include procedures for 
incorporating an ice detector system that includes an ice probe that 
will enunciate the presence of actual icing conditions.
    The service bulletin specifies using a Rosemont ice detector, part 
number (P/N) 0871CT1, but this part may be substituted with Rosemont P/
N 0871HL1/HL2 or an FAA-approved equivalent part number;
    <bullet> Test Instrumentation, Inc. Document No. MU2-4001, Rev. C, 
dated June 30, 1997, and Mitsubishi MU-2 SB No. 231, dated July 2, 
1997: these documents include procedures for incorporating an automatic 
autopilot disconnect system that turns off the autopilot when the 
airspeed of the airplane falls between 130 to 140 knots indicated 
airspeed (KIAS);
    <bullet> Mitsubishi MU-2 SB No. 226B, Revision B, dated October 27, 
1997: this document includes procedures for incorporating an auto-
ignition (re-light) system; and
    <bullet> Mitsubishi MU-2 SB No. 074/74-001, dated October 9, 1991: 
this document includes procedures for incorporating an engine ignition 
unit replacement (to increase the engines tolerance of ice) and reduce 
the chances of engine flame-out during critical phases of flight.

The FAA's Determination

    After examining the circumstances and reviewing all available 
information related to the accidents described above, including the 
previously referenced service information, the FAA has determined that 
AD action should be taken. Taking AD action is needed to prevent 
departure from controlled flight and to assist the pilot in detecting 
ice accumulation on the airplane when flying in icing conditions that 
exceed the airplane's ice protection capability, which could result in 
possible loss of control of the airplane.

Explanation of the Provisions of the Proposed AD

    Since an unsafe condition has been identified that is likely to 
exist or develop in other MU-2B series airplanes of the same type 
design, the proposed AD would require incorporating the following:
    (1) An ice detection system,
    (2) A de-ice monitoring system,
    (3) An automatic autopilot disconnect system and a trim-in-motion 
alert system,
    (4) An engine continuous-duty ignition unit replacement,
    (5) An auto-ignition (re-light) system, and
    (6) Fabricating a placard (using \1/8\-inch letters) and installing 
this placard within the pilot's clear view with the following words:

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

Proposed Compliance Time

    The FAA has determined that the compliance time of the proposed AD 
should be specified in calendar time instead of hours time-in-service. 
Although the condition addressed by the proposed 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 
proposed compliance time of ``12 calendar months after the effective 
date of this AD'' would not inadvertently ground airplanes and would 
assure that all owners/operators of the affected airplanes accomplish 
the proposed 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

[[Page 27874]]

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. The Certification must 
include a statement providing the factual basis for this determination, 
and the reasoning should be clear.
    The FAA has determined that this proposed AD would 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, the proposed AD is the least costly alternatives to improve the 
safety of the Mitsubishi MU-2B series airplanes that may encounter in-
flight 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 two or more of these airplanes. 
Ownership of more than one MU-2B series airplane is believed to be 
limited to five percent of the affected aircraft owners. Only one of 
these operators had ten or more of these airplanes. The total number of 
owners operating of 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 proposed 
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 would be subject to a total of four inspections per year. 
At a nominal inspection time of one hour per inspection and labor cost 
of $60 per hour, the proposed annual inspection costs would be 
approximately $240 per airplane. These estimates include costs for the 
associated record keeping. A reasonable range of costs arising from 
this proposed AD is suggested in the following table:

----------------------------------------------------------------------------------------------------------------
                                                                                Annualized cost        Present  
              Cost of capital                 Remaining life of aircraft  --------------------------   value of 
                                                                             Initial       Total      total cost
----------------------------------------------------------------------------------------------------------------
10%/year..................................  20 years.....................       $3,022       $3,262      $27,771
15%/year..................................  20 years.....................        4,110        4,350       27,230
10%/year..................................  10 years.....................        4,187        4,427       27,203
15%/year..................................  10 years.....................        5,126        5,366       26,933
----------------------------------------------------------------------------------------------------------------

    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 
manufacturer, detailed inspections show that deterioration of the 
airframes has been quite small, so that a 20-year life expectancy may 
be a reasonable assumption. 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 assume 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 would be approximately $27,000 per airplane. The total annualized 
cost of this proposed AD for the U.S. fleet would be in the range of $1 
million (320 x $3,200 = $1,024,000) to $1.8 million (340 x $5,400 = 
$1,836,000). The present discounted value of total costs imposed by the 
proposed 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 proposed AD costs 
would be about 3.5 percent to 9 percent (($27,000/$800,000) x 100% = 
3.5% to ($27,000/$300,000)  x 100% = 9%) of the market value of the 
airplane. Because the costs imposed by the proposed AD would be 
proportionately higher for less expensive airplanes, it is likely that 
they would also be proportionately higher for smaller, less financially 
strong operators than for larger operators.
    Based on the above-referenced conditions, the proposed AD would 
have a substantial economic impact on a significant number of small 
entities.

Cost Versus Benefits

    The purpose of the proposed AD is to improve flight safety under 
icing conditions for Mitsubishi MU-2B series airplanes. The National 
Transportation Safety Board (NTSB) Accident-Incident Database indicates 
that three Mitsubishi MU-2B airplane accidents occurred from 1982 
through 1996, with a total of 14 fatalities. All three accidents were 
related to loss of control of the airplane while flying in severe icing 
conditions. These three airplane accidents amount to about one percent 
of the MU-2B series airplane fleet. All were part 91 operations.
    In one of these accidents, involving eight fatalities in 1996, the 
pilot continued flight into (unforecast) severe icing conditions with 
known in-operative anti-ice gear. The NTSB report attributed the 
accident to flying with known equipment deficiencies and failure to 
maintain airspeed.
    In a second accident, involving five fatalities in 1990, the NTSB 
noted that the probable cause included improper flight planning, which 
resulted in flight into icing conditions, along with failure to 
maintain adequate airspeed and control. Pilot inexperience in this 
Mitsubishi MU-2B series airplane was also cited as a related factor.
    In a third accident involving one fatality in 1988, the pilot was 
the sole occupant. The pilot of the 1988 accident reported an 
uncontrolled descent shortly after starting to climb, following a 
descent that had been made in order to remove structural icing. 
Although the reason for this accident was indicated to be undetermined, 
the airplane was believed to have had problems with cabin 
pressurization, as well as some structural damage associated with 
landing in an overweight condition, prior to encountering the icing. 
Crew error was found to be one of the causes of the first two 
accidents, and seems

[[Page 27875]]

likely in the third accident. Timely warnings of the ice forming on the 
airframe may have prevented some or all of these accidents.
    In developing this Regulatory Flexibility Analysis several 
alternatives to proposing this AD were considered. The alternatives 
included: (1) taking no action, including issuance of the proposed AD, 
(2) requiring additional training and the provision of special 
instructions relating to operating in icing conditions for MU-2B series 
pilots, (3) banning the MU-2B series airplanes from flights into known 
or suspected icing conditions, and (4) issuing the proposed AD.
    Alternative (1): taking no action. Taking no action would 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.
    Alternative (2): requiring additional training. A requirement for 
additional training is addressed in AD 97-20-14, Amendment 39-10150 (62 
FR 51594) issued on September 26, 1997, which requires periodic 
training of pilots and crew flying any Mitsubishi MU-2 series airplane 
into possible or forecast icing conditions. This training should assist 
in reducing future ice-related accidents for the affected airplanes.
    Alternative (3): banning flight into known or suspected icing 
conditions. Banning flight into known or suspected icing conditions 
would not eliminate inadvertent encounters with icing conditions aloft. 
Such restrictions may have little effect flying into unforecast icing 
conditions with inoperable anti-ice equipment and insufficient flight 
planning. Unknown forecast conditions aloft and insufficient flight 
planning contributed to two of the accidents (and 13 of the 14 
fatalities) cited. In addition, such a ban would impose costs on 
owners/operators in the form of significant losses in value for the 
airplanes, since the airplanes would be prevented from making flights, 
despite being outfitted with anti-ice equipment.
    Alternative (4): issuing the proposed AD. Issuing the proposed AD 
would result in the installation of equipment that would provide a 
timely warning at the onset of icing conditions, so that most accidents 
resulting from inadvertent encounters with severe icing conditions 
could possibly be prevented.
    A benefit/cost comparison for this proposed AD can be made by 
noting that the present value of the costs imposed by this rule are on 
the order of $9 million. The present value of a single life saved 
sometime over the next 20 years (making use of the Department of 
Transportation's value for an avoided fatality of $2.7 million) is 
approximately $1.43 million. This figure reflects 1/20 of an annual 
avoided fatality ($2.7 million / 20 = $135,000) discounted over 20 
years at the Office of Management and Budget-specified discount rate of 
7 percent.
    With these figures in mind, the proposed AD would have benefits in 
excess of costs if it were to result in the avoidance of a single 
accident that involves 6 or 7 fatalities ($9 million / $1.43 million = 
6.29 avoided fatalities) over the next 20 years. Adding the benefit of 
avoiding the loss of an airplane worth nearly a half million dollars to 
the benefit presented above increases the benefits relative to costs 
related to the proposed actions.
    Although it may be assumed that current operators of these 
airplanes are now aware of the dangers posed by icing conditions, so 
that icing-related accidents are now less likely than in the recent 
past, the avoidance of 6 or 7 icing-related fatalities over the next 20 
years is not implausible. These airplanes can carry up to 12 passengers 
and crewmembers. The past 10 years' experience implies an annual icing-
related accident rate of 0.33 (3/10 = 0.33) with an annual icing-
related fatality rate of 1.4 (14/10 = 1.4). Seven avoided fatalities 
over the next 20 years implies an annual avoided fatality rate of 0.35 
(7/20 = 0.35), or one-fourth of the average Mitsubishi MU-2B airplane 
icing-related fatality rate observed over the past 10 years.
    For reasons outlined above, the FAA has determined that the 
proposed AD is likely to have benefits in excess of costs and is not 
aware of a less costly alternative that would be likely to bring about 
a significant improvement in the safety of Mitsubishi MU-2B series 
airplanes that encounter in-flight icing conditions.

Regulatory Impact

    The regulations proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify 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) if promulgated, 
will have a significant economic impact, positive or negative, on a 
substantial number of small entities under the criteria of the 
Regulatory Flexibility Act. A copy of the draft regulatory evaluation 
prepared for this action has been placed in the Rules Docket. A copy of 
it may be obtained by contacting 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.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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.


Sec. 39.13  [Amended]

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

Mitsubishi Heavy Industries, Ltd.: Docket No. 97-CE-21-AD.

    Applicability: Models 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, and MU-2B-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 (i) 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 within the next 12 calendar months after 
the effective date of this AD, unless already accomplished.
    To prevent departure from controlled flight and to assist the 
pilot in detecting ice accumulation on the airplane when flying in 
icing conditions that exceed the airplane's ice protection 
capability, which could result in possible loss of control of the 
airplane, accomplish the following:

[[Page 27876]]

    (a) Incorporate an ice detection system in accordance with the 
instructions in Mitsubishi MU-2 Service Bulletin (SB) No. 217, 
Revision B, dated November 7, 1996, and Test Instrumentation Inc. 
Document No. MU2-6005, dated September 28, 1997.

    Note 2: The Rosemount ice detection probe (part number (P/N) 
0871 HL1/HL2 or an FAA-approved equivalent part number) may be 
substituted for the Rosemount P/N 0871CT1 called out in Mitsubishi 
MU-2B SB No. 217, Revision B, dated November 7, 1996, and Test 
Instrumentation Inc. Document No. MU2-6005, dated September 28, 
1997.

    (b) Incorporate a pneumatic de-ice monitoring system in 
accordance with the instructions in Test Instrumentation, Inc. 
Document No. MU2-5001, Rev. E., dated May 21, 1997, and Mitsubishi 
MU-2 SB No. 232, dated July 2, 1997.
    (c) Incorporate a trim-in-motion alerting system and an 
automatic autopilot disconnect system in accordance with the 
instructions 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.
    (d) Incorporate an engine ignition unit replacement in 
accordance with the instructions in Mitsubishi MU-2B SB No. 074/74-
001, dated October 9, 1991.
    (e) Incorporate an auto-ignition (re-light) system in accordance 
with the instructions in Mitsubishi MU-2 SB No. 226B, Revision B, 
dated October 27, 1997.
    (f) Fabricate a placard with the following words and install 
this placard within the pilot's clear view:

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

    (g) Paragraph (f) of this AD can be accomplished 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 43.9 of the Federal Aviation 
Regulations (14 CFR 43.9).
    (h) 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.
    (i) 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, 1201 Walnut, 
suite 900, Kansas City, Missouri 64106. 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.

    (j) All persons affected by this directive may obtain copies of 
the documents referred to herein upon request to Mitsubishi Heavy 
Industries America, Inc., 15303 Dallas Parkway, suite 685, LB-77, 
Dallas, Texas; or may examine these documents at the FAA, Central 
Region, Office of the Regional Counsel, Room 1558, 601 E. 12th 
Street, Kansas City, Missouri 64106.

    Issued in Kansas City, Missouri, on May 13, 1998.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 98-13517 Filed 5-20-98; 8:45 am]
BILLING CODE 4910-13-U