Airworthiness Directives; Schweizer Aircraft Corporation Model 269D Helicopters

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-SW-13-AD; Amendment 39-11002; AD 98-26-06]

Airworthiness Directives; Schweizer Aircraft Corporation Model

269D Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This document publishes in the Federal Register an amendment

adopting Airworthiness Directive (AD) 98-26-06 which was sent

previously to all known U.S. owners and operators of Schweizer Aircraft

Corporation (Schweizer) Model 269D helicopters by individual letters.

This AD requires removing the main rotor drive shaft (shaft) and

inspecting it for cracks. If a crack is found, replacing the shaft with

an airworthy shaft is required. This AD also requires periodically

verifying the torque of the main rotor hub (hub) bolts. This amendment

is prompted by four reports of cracking in the shaft of helicopters

with a large diameter hub. Wear patterns indicate cracking was caused

by loss of clamping torque on the hub and shaft assembly due to the use

of grease between the hub and shaft. This condition, if not corrected,

could result in failure of the shaft and subsequent loss of control of

the helicopter.

DATES: Effective February 3, 1999, to all persons except those persons

to whom it was made immediately effective by Priority Letter AD 98-26-

06, issued on December 9, 1998, which contained the requirements of

this amendment.

Comments for inclusion in the Rules Docket must be received on or

before March 22, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Office of the Regional Counsel, Southwest Region,

Attention: Rules Docket No. 98-SW-13-AD, 2601 Meacham Blvd., Room 663,

Fort Worth, Texas 76137.

FOR FURTHER INFORMATION CONTACT: Raymond H. Reinhardt, Aerospace

Engineer, Airframe and Propulsion Branch, ANE-171, FAA, New York

Aircraft Certification Office, 10 Fifth St., Valley Stream, NY,

telephone (516) 256-7532, fax (516) 568-2716.

SUPPLEMENTARY INFORMATION: On December 9, 1998, the FAA issued Priority

Letter AD 98-26-06, applicable to Schweizer Model 269D helicopters,

which requires removing the shaft and inspecting it for cracks. If a

crack is found, replacing the shaft with an airworthy shaft is

required. That AD also requires periodically verifying the torque of

the hub bolts. That action was prompted by four reports of cracking in

the shaft of helicopters with a large diameter hub. Wear patterns

indicate cracking was caused by loss of clamping torque on the hub and

shaft assembly due to the use of grease between the hub and shaft. A

pilot reported excessive vibration in one incident. An inspection

following that incident revealed a 2.5-inch horizontal crack in the

shaft. The crack started from one of the three lower bolt holes,

propagated to an adjacent bolt hole, and then propagated from the

second bolt hole in a downward direction. This condition, if not

corrected, could result in failure of the shaft and subsequent loss of

control of the helicopter.

Since the unsafe condition described is likely to exist or develop

on other Schweizer Model 269D helicopters of the same type design, the

FAA issued Priority Letter AD 98-26-06 to prevent failure of the shaft

and subsequent loss of control of the helicopter. The AD requires,

prior to 200 hours time-in-service (TIS), and thereafter at intervals

not to exceed 100 hours TIS, inspecting the shaft for cracks in the

area of the six hub attach bolts using a 10-power or higher magnifying

glass and bright light. If no crack is found as a result of the visual

inspection, the AD requires inspecting the shaft using a magnetic

particle inspection method. If a crack is found, the AD requires

replacing the shaft with an airworthy shaft. The AD also requires

periodically verifying the torque of the hub bolts. The short

compliance time involved is required because the previously described

critical unsafe condition can adversely affect the controllability of

the helicopter. Therefore, the inspections and replacement, if

necessary, are required prior to further flight, and this AD must be

issued immediately.

Since it was found that immediate corrective action was required,

notice and opportunity for prior public comment thereon were

impracticable and contrary to the public interest, and good cause

existed to make the AD effective immediately by individual letters

issued on December 9, 1998, to all known U.S. owners and operators of

Schweizer Model 269D helicopters. These conditions still exist, and the

AD is hereby published in the Federal Register as an amendment to

section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to

make it effective to all persons.

The FAA estimates that 6 helicopters of U.S. registry will be

affected by this AD, that it will take approximately 2 work hours for

the periodic inspections and 22 work hours to replace the shaft, if

necessary, per helicopter, and the average labor rate is $60 per work

hour. Required parts will cost approximately $12,000 per replacement

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

operators is estimated to be $80,640 to replace the shafts in all the

helicopters, and $7,200 a year for 10 inspections per year on each

helicopter.

[[Page 2822]]

Comments Invited

Although this action is in the form of a final rule that involves

requirements affecting flight safety and, thus, was not preceded by

notice and an opportunity for public comment, comments are invited on

this rule. Interested persons are invited to comment on this rule by

submitting such written data, views, or arguments as they may desire.

Communications should identify the Rules Docket number and be submitted

in triplicate to the address specified under the caption ADDRESSES. All

communications received on or before the closing date for comments will

be considered, and this rule may be amended in light of the comments

received. Factual information that supports the commenter's ideas and

suggestions is extremely helpful in evaluating the effectiveness of the

AD action and determining whether additional rulemaking action would be

needed.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the rule that might

suggest a need to modify the rule. All comments submitted will be

available, both before and after the closing date for comments, in the

Rules Docket for examination by interested persons. A report that

summarizes each FAA-public contact concerned with the substance of this

AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this rule must submit a self-addressed,

stamped postcard on which the following statement is made: ``Comments

to Docket No. 98-SW-13-AD.'' The postcard will be date stamped and

returned to the commenter.

The regulations adopted herein will not have substantial direct

effects on the States, on the relationship between the national

government and the States, or on the distribution of power and

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency

regulation that must be issued immediately to correct an unsafe

condition in aircraft, and that it is not a ``significant regulatory

action'' under Executive Order 12866. It has been determined further

that this action involves an emergency regulation under DOT Regulatory

Policies and Procedures (44 FR 11034, February 26, 1979). If it is

determined that this emergency regulation otherwise would be

significant under DOT Regulatory Policies and Procedures, a final

regulatory evaluation will be prepared and placed in the Rules Docket.

A copy of it, if filed, may be obtained from the Rules Docket at the

location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends part 39 of

the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

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

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

Sec. 39.13 [Amended]

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

to read as follows:

98-26-06 Schweizer Aircraft Corporation: Amendment 39-11002. Docket

No. 98-SW-13-AD.

Applicability: Model 269D helicopters with a large diameter main

rotor hub (hub), part number (P/N) 269A1002-11, and main rotor drive

shaft (shaft), P/N 269A5305-139, -143, -145, or -147, installed,

certificated in any category.

Note 1: This AD applies to each helicopter 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 helicopters that have been modified,

altered, or repaired so that the performance of the requirements of

this AD is affected, the owner/operator must use the authority

provided in paragraph (c) to request approval from the FAA. This

approval may address either no action, if the current configuration

eliminates the unsafe condition, or different actions necessary to

address the unsafe condition described in this AD. Such a request

should include an assessment of the effect of the changed

configuration on the unsafe condition addressed by this AD. In no

case does the presence of any modification, alteration, or repair

remove any helicopter from the applicability of this AD.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the shaft and subsequent loss of control

of the helicopter, accomplish the following:

(a) Prior to 200 hours time-in-service (TIS) since the assembly

of the hub and a shaft having zero hours TIS, and thereafter at

intervals not to exceed 100 hours TIS,

(1) Remove the shaft from the power train system.

(2) Clean and inspect the shaft for a crack in the area of the

six hub attach bolt (bolt) holes using a 10-power or higher

magnifying glass and bright light.

(3) If no crack is found, inspect the shaft using a direct or

indirect magnetic particle inspection method in accordance with ASTM

Standard No. E1444 as follows:

(i) For direct magnetization, use an AC, DC, or AC/DC wet

continuous method with fluorescent or nonfluorescent particles.

(A) Circular (Head Shot)--1,100 amperes

Look for a longitudinal crack.

(B) Longitudinal (Coil Shot)--Because of variations in coil

design, only the length-to-diameter ratio based on effective

diameter and inspection region is provided.

Effective diameter--1.279 inches,

Length--6.00 inches,

L/D Ratio--5,

Look for a circumferential crack.

(C) Demagnetize and clean the inspection areas with solvent to

remove residual particles.

(ii) For indirect magnetization, use an AC electromagnetic yoke

(Magnaflux product No. Y-6 or equivalent). Set the spacing and the

angle to suit the external diameter of the shaft.

(A) Magnetize each of the six hole areas by applying the AC

electromagnetic yoke (yoke) circumferentially across the hole.

(B) During each magnetization, apply dry color contrasting

particles to the inspection area and look for a circumferential

crack propagating from any hole.

(C) Demagnetize and repeat the inspections with the poles of the

yoke positioned longitudinally across each hole group looking for a

circumferential crack.

(D) Demagnetize and clean the inspection areas with solvent to

remove residual particles.

(iii) If no crack is found as a result of the magnetic particle

inspection, reassemble the hub and shaft.

Note 2: Procedures in Model 269D Handbook of Maintenance

Instructions (HMI) revised on June 12, 1998, include installing a

three-piece retention fitting, applying a higher torque to each

bolt, assembling with no lubricant, and applying zinc chromate

primer between the hub and the shaft.

(4) If a crack is found, replace the shaft with an airworthy

shaft.

(b) At intervals not to exceed 50 hours TIS after accomplishing

paragraph (a),

(1) Unsafety and clean the exterior of the bolts.

(2) Unsafety and loosen the droop stop nut.

(3) Apply 390 in-lbs of torque to each of the six bolts. If any

bolt rotates, accomplish the requirements of paragraph (a).

(4) Apply 390 to 410 in-lbs of torque to each of the six bolts

and resafety.

(5) Torque and safety the droop stop nut.

(6) Seal the exterior of the bolts and washers with a corrosion

preventative compound.

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

compliance time that provides an acceptable level of safety may be

used if approved by the Manager, New York Aircraft Certification

Office, FAA. Operators

[[Page 2823]]

shall submit their requests through an FAA Principal Maintenance

Inspector, who may concur or comment and then send it to the

Manager, New York Aircraft Certification Office.

Note 3: Information concerning the existence of approved

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

obtained from the New York Aircraft Certification Office.

(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 helicopter to a location where

the requirements of this AD can be accomplished.

(e) This amendment becomes effective on February 3, 1999, to all

persons except those persons to whom it was made immediately

effective by Priority Letter AD 98-26-06, issued December 9, 1998,

which contained the requirements of this amendment.

Issued in Fort Worth, Texas, on January 8, 1999.

Henry A. Armstrong,

Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 99-1064 Filed 1-15-99; 8:45 am]

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