Airworthiness Directives; American Champion Aircraft Corporation 7, 8, and 11 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-CE-79-AD]

RIN 2120-AA64

Airworthiness Directives; American Champion Aircraft Corporation

7, 8, and 11 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 American Champion Aircraft Corporation (ACAC)

7, 8, and 11 series airplanes, excluding Model 8GCBC airplanes. The

Federal Aviation Administration (FAA) previously proposed similar AD

action for the ACAC Model 8GCBC airplanes. The proposed AD would

require installing inspection holes on the top and bottom wing

surfaces, repetitively inspecting the front and rear wood spars for

damage, repairing or replacing any damaged wood spar, and installing

inspection covers. Damage is defined as cracks; compression cracks;

longitudinal cracks through the bolt holes or nail holes; or loose or

missing rib nails. The proposed AD results from a review of the service

history of the affected airplanes that incorporate wood wing spars. The

review was prompted by in-flight wing structural failures on ACAC Model

8GCBC airplanes, and revealed several incidents where damage was found

on the front and rear wood spars on the affected airplanes. The actions

specified by the proposed AD are intended to prevent possible

compression cracks and other damage in the wood spar wing, which, if

not detected and corrected, could eventually result in in-flight

structural failure of the wing with consequent loss of the airplane.

DATES: Comments must be received on or before January 8, 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-79-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 American Champion Aircraft Corporation, P.O. Box 37, 32032

Washington Avenue, Highway D, Rochester, Wisconsin 53167. This

information also may be examined at the Rules Docket at the address

above.

FOR FURTHER INFORMATION CONTACT: Mr. William Rohder, Aerospace

Engineer, FAA, Chicago Aircraft Certification Office, 2300 E. Devon

Avenue, Des Plaines, Illinois 60018; telephone (847) 294-7697;

facsimile (847) 294-7834.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed rule by submitting such

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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-79-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-79-AD, Room 1558, 601 E. 12th Street, Kansas

City, Missouri 64106.

Discussion

AD 87-18-09, Amendment 39-5725, currently requires inspecting (one-

time) the sides of the front and rear wood spars for compression cracks

on ACAC Model 8GCBC airplanes, repairing or replacing any wood spar

with compression cracks, and re-inspecting immediately after any

incident involving wing damage. AD 87-18-09 was the result of three

accidents involving ACAC Model 8GCBC airplanes where structural damage

to the wing caused by compression cracks in a wood spar was considered

to be a primary factor of the accidents.

Wood compression cracks are failures of wood fibers on a plane

perpendicular to the wood fiber longitudinal axis. Repetitive high

stress can initiate these compression cracks on the top surface of the

wing spar that is adjacent to doubler plate glue lines and rib nail

holes. These high stress conditions can occur during crop dusting,

banner and glider tow operations, turbulence, and rough field or float

operations. Compression cracks can also initiate if the wing contacts

the ground. Compression cracks can initiate at either the top or bottom

surface of the spar depending on the loads (either upward or downward)

at impact.

In-flight structural failure of the wing recently occurred on an

ACAC Model 8GCBC airplane that was initially inspected as required by

AD 87-18-09. A possible contributing factor of this incident was an

undetected compression crack on the right wing front spar.

Investigation of this accident and data acquired from inspections

of several ACAC Model 8GCBC airplanes indicate that wood spar

compression cracks can occur without previous wing damage. The data

indicates that detection of compression crack initiation is unlikely on

the sides of the spar, unless the crack is in an advanced state of

propagation. Based on this data, the FAA believes that repetitive

inspections are necessary. The FAA recently issued an NPRM on the Model

8GCBC airplanes that was published in the Federal Register on September

26, 1997 (62 FR 50527). This NPRM proposes to supersede AD 87-18-09,

and, if issued as a final rule, would require similar action to that

proposed in this document.

Reasons for the Proposed AD

The above-referenced incidents on the ACAC Model 8GCBC airplanes

prompted the FAA to review the service history of the other ACAC 8

series airplanes, as well as the 7 and 11 series airplanes. The FAA has

record of eight reports of accidents (five fatal) on ACAC 7 and 8

series airplanes, other than the Model 8GCBC airplanes. Four of these

accidents are attributed to overstress, two to wing failure due to

previous damage going undetected, one to an overload condition with

evidence of wing panel failure prior to impact, and one spar with an

out-of-specification wood spar grain slope. This review revealed 16

reports of spar crack damage (spar butt end and/or longitudinal

cracks), 6 reports of compression cracked spars, and 13 reports of

loose/missing rib nails. These reports break down as follows:

--Model 7AC (2,626 U.S. registered airplanes): 12 reports of spar crack

damage, plus 2 reports of loose/missing rib nails;

--Model 7BCM (253 U.S. registered airplanes): 1 report of spar crack

damage;

--Model 7ECA (871 U.S. registered airplanes): 1 report of a compression

cracked spar, plus 6 reports of loose/missing rib nails;

--Model 7GCBC (829 U.S. registered airplanes): 1 report of a

compression cracked spar;

--Model 7KCAB (482 U.S. registered airplanes): 2 reports of spar crack

damage, 2 reports of compression cracked spars, and 3 reports of loose/

missing rib nails; and

--Model 8KCAB (480 U.S. registered airplanes): 1 report of spar crack

damage, 2 reports of compression cracked spars, and 2 reports of loose/

missing rib nails.

The FAA believes that many cracked/damaged spars are not reported

because general aviation operators (operating in accordance with part

91 of the Federal Aviation Regulations (14 CFR part 91)) are not

required to submit service difficulty reports.

Relevant Service Information

The FAA has reviewed and approved the technical contents of ACAC

Service Letter 406, dated March 28, 1994, and ACAC Service Letter 417,

Revision A, dated October 2, 1997. ACAC Service Letter 406, dated March

28, 1994, includes procedures for conducting a detailed visual

inspection of both the front and rear wood wing spars for cracks;

compression cracks; longitudinal cracks through the bolt holes or nail

holes; and loose or missing rib nails (referred to as damage

hereafter). ACAC Service Letter 417, Revision A, dated October 2, 1997,

includes procedures for installing inspection holes and surface covers

and assuring that all applicable lower surface drain holes are

installed.

The FAA's Determination

After examining the circumstances and reviewing all available

information related to the incidents and accidents described above,

including the referenced service information, the FAA has determined

that (1) the wing design of all 7, 8, and 11 series airplanes equipped

with wood spars is similar and is conducive to spar cracks/damage; and

(2) AD action should be taken to prevent possible compression cracks

and other damage in the wood spar wing, which, if not detected and

corrected, could eventually result in in-flight structural failure of

the wing with consequent loss 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 ACAC 7, 8, and 11 series airplanes (excluding

the Model 8GCBC airplanes) of the same type design, the FAA is

proposing AD action. The proposed AD would require installing

inspection holes on the top

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and bottom wing surfaces, repetitively inspecting the front and rear

wood spars for damage, repairing or replacing any damaged wood spar,

and installing surface covers. Accomplishment of the proposed actions

would be as follows:

--Installations: in accordance with ACAC Service Letter 417, Revision

A, dated October 2, 1997;

--Inspections: in accordance with ACAC Service Letter 406, dated March

28, 1994; and

--Spar Repair and Replacement, as applicable: in accordance with

Advisory Circular (AC) 43-13-1A, Acceptable Methods, Techniques and

Practices; or other data that the FAA has approved for spar repair and

replacement.

Differences Between This Proposed AD and ACAC Service Letter 406

ACAC Service Letter 406, dated March 28, 1994, specifies the same

inspections as are proposed in this notice of proposed rulemaking

(NPRM). The differences between the service letter and NPRM are:

--the service letter specifies the proposed action within the next 30

days or 10 flight hours and at each 100 hour/annual inspection

thereafter. The FAA has determined that a more realistic and

enforceable compliance time would be to require:

1. The proposed initial inspection at the first annual

inspection that occurs 3 calendar months or more after the effective

date of the AD or within 15 calendar months after the effective date

of the AD, whichever occurs first; and

2. The proposed repetitive inspections thereafter at intervals

not to exceed 12 calendar months or 500 hours time-in-service (TIS),

whichever occurs first;

and

--the service letter applies to all ACAC 7 and 8 series airplanes,

whereas the NPRM applies to ACAC 7, 8, and 11 series airplanes with

similar design, except for the Model 8GCBC airplanes. The FAA

previously proposed similar AD action for the ACAC Model 8GCBC

airplanes, Docket No. 97-CE-33-AD (62 FR 50527, September 26, 1997).

Compliance Time of the Proposed AD

The compliance time of the proposed AD is presented in calendar

time and hours TIS. Although the unsafe condition specified in the

proposed AD is a result of airplane operation, operators of the

affected airplanes utilize their airplanes in different ways.

For example, an operator may utilize his/her airplane 50 hours TIS

in a year while utilizing the aircraft in no or very little crop

dusting operations, banner and glider tow operations, or rough field or

float operations. This airplane would obviously have a lower crack

propagation rate than an airplane operated 300 hours TIS a year in

frequent crop dusting operations, banner and glider tow operations, or

rough field or float operations. However, this airplane could have pre-

existing and undetected wood spar damage that occurred during previous

operations. In this situation, the damage to the wood spar would

propagate at a level that depends on the operational exposure of the

airplane and severity of the initial wood spar damage.

To assure that compression cracks do not go undetected in the wood

spars of the affected airplanes, the FAA has determined that the

following compliance times should be used:

1. The proposed initial inspection at the first annual

inspection that occurs 3 calendar months or more after the effective

date of the AD or within 15 calendar months after the effective date

of the AD, whichever occurs first; and

2. The proposed repetitive inspections thereafter at intervals

not to exceed 12 calendar months or 500 hours TIS, whichever occurs

first.

Cost Impact

The FAA estimates that 6,440 airplanes in the U.S. registry would

be affected by the proposed AD, that it would take approximately 6

workhours (Installations: 5 workhours; Initial Inspection: 1 workhour)

per airplane to accomplish the proposed action, and that the average

labor rate is approximately $60 an hour. Parts cost approximately $292

per airplane, provided that each airplane would only need 11 additional

standard inspection hole covers per wing bottom surface (total of 22

new covers per airplane). If the airplane would require the

installation of more inspection covers (i.e., a result of previous non-

factory wing recover work), the cost could be slightly higher. Based on

these figures, the total cost impact of the proposed AD on U.S.

operators is estimated to be $4,198,880 or $652 per airplane.

This cost figure is based on the presumption that no affected

airplane owner/operator has accomplished the installations or the

initial inspection. The FAA has no knowledge of any owner/operator of

the affected airplanes that has already accomplished the installations

and initial inspection.

This cost figure also does not account for repetitive inspections.

The FAA has no way of determining the number of repetitive inspections

each owner/operator of the affected airplanes will incur over the life

of his/her airplane. However, each proposed repetitive inspection would

cost substantially less than the initial inspection because of the cost

of the initial proposed inspection hole and cover installations would

not be repetitive. The inspection covers allow easy access for the

inspection of the wood spars, and the proposed compliance time would

enable the owners/operators of the affected airplanes to accomplish the

repetitive inspections at regularly scheduled annual inspections.

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 not 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 14

CFR part 39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

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

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

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Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding a new airworthiness directive

(AD) to read as follows:

American Champion Aircraft Company: Docket No. 97-CE-79-AD.

Applicability: The following airplane models, all serial

numbers, certificated in any category, that are equipped with wood

wing spars:

7AC

7BCM (L-16A)

7DC

S7EC

7GC

7GCB

7HC

7KCAB

S11AC

7ACA

7CCM (L-16B)

S7DC

7ECA

7GCA

7GCBA

7JC

8KCAB

11BC

S7AC

S7CCM

7EC

7FC

7GCAA

7GCBC

7KC

11AC

S11BC

Note 1: This AD applies to each airplane identified in the

preceding applicability provision, regardless of whether it has been

modified, altered, repaired, or reconfigured in the area subject to

the requirements of this AD. For airplanes that have been modified,

altered, repaired, or reconfigured 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) 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 possible compression cracks and other damage in the wood

spar wing, which, if not detected and corrected, could eventually

result in in-flight structural failure of the wing with consequent loss

of the airplane, accomplish the following:

(a) At the first annual inspection that occurs 3 calendar months or

more after the effective date of this AD or within the next 15 calendar

months after the effective date of this AD, whichever occurs first,

accomplish the following:

(1) Install inspection holes in the top and bottom surface of each

wing in accordance with American Champion Aircraft Corporation (ACAC)

Service Letter 417, Revision A, dated October 2, 1997. Assure that all

drainage holes are installed as depicted in this service letter, and

install drainage holes as necessary.

(2) Inspect (detailed visual) both the front and rear wood wing

spars for cracks; compression cracks; longitudinal cracks through the

bolt holes or nail holes; and loose or missing rib nails (referred to

as damage hereafter). Accomplish these inspections in accordance with

ACAC Service Letter 406, dated March 28, 1994.

(3) If any spar damage is found, prior to further flight,

accomplish the following:

(i) Repair or replace the wood wing spar in accordance with

Advisory Circular (AC) 43-13-1A, Acceptable Methods, Techniques and

Practices; or other data that is approved by the FAA for wing spar

repair or replacement.

(ii) If the wing is recovered, accomplish the installations

required by paragraph (a)(1) of this AD, as applicable.

(4) Install inspection hole covers on the top and bottom surface of

the wing in accordance with ACAC Service Letter 417, Revision A, dated

October 2, 1997.

(b) Within 12 calendar months or 500 hours TIS (whichever occurs

first) after accomplishing all actions required by paragraph (a) of

this AD, and thereafter at intervals not to exceed 12 calendar months

or 500 hours TIS, whichever occurs first, accomplish the inspection,

repair, replacement, and installation required by paragraphs (a)(2),

(a)(3), as applicable; including its subparagraphs; and (a)(4) of this

AD.

(c) If, after the effective date of this AD, any of the affected

airplanes are involved in an incident/accident that involves wing

contact damage (e.g., surface deformations such as abrasions, gouges,

scratches, or dents, etc.), prior to further flight after that

incident/accident, accomplish the inspection, repair, replacement, and

installation required by paragraphs (a)(2), (a)(3), as applicable;

including its subparagraphs; and (a)(4) of this AD.

(d) 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.

(e) An alternative method of compliance or adjustment of the

initial or repetitive compliance time that provides an equivalent level

of safety may be approved by the Manager, Chicago Aircraft

Certification Office (ACO), 2300 E. Devon Avenue, Des Plaines, Illinois

60018. The request shall be forwarded through an appropriate FAA

Maintenance Inspector, who may add comments and then send it to the

Manager, Chicago ACO.

Note 2: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Chicago ACO.

(f) All persons affected by this directive may obtain copies of the

documents referred to herein upon request to American Champion Aircraft

Corporation, P.O. Box 37, 32032 Washington Avenue, Highway D,

Rochester, Wisconsin 53167; 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 October 27, 1997.

Mary Ellen A. Schutt,

Acting Manager, Small Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 97-28984 Filed 10-31-97; 8:45 am]

BILLING CODE 4910-13-U