Airworthiness Directives; Robinson Helicopter Company Model R44 Helicopters

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 96-SW-25-AD; Amendment 39-9779; AD 96-18-22]

RIN 2120-AA64

Airworthiness Directives; Robinson Helicopter Company Model R44

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) 96-18-22 which was sent

previously to all known U.S. owners and operators of Robinson

Helicopter Company (Robinson) Model R44 helicopters by individual

letters. This AD requires an inspection of the mating surfaces of the

main rotor gearbox (gearbox) components for pitting, elongated bolt

holes, or machining grooves, and replacement of the gearbox if

elongated bolt holes, machining grooves, or an improper amount of

pitting is discovered; and replacement of the 18 bolts and washers that

attach the gear to the gear carrier assembly (gear carrier). This

amendment is prompted by an inflight failure of the gearbox on a

French-registered Model R44 helicopter that resulted in an accident.

The actions specified by this AD are intended to prevent loosening of

the bolts securing the gear to the gear carrier, which could lead to

fatigue failure of the gear carrier within the gearbox, and subsequent

loss of power to the main rotor which could lead to a forced landing.

DATES: Effective October 25, 1996, to all persons except those persons

to whom it was made immediately effective by priority letter AD 96-18-

22, issued on August 29, 1996, which contained the requirements of this

amendment.

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

before December 9, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Office of the Assistant Chief Counsel, Attention:

Rules Docket No. 96-SW-25-AD, 2601 Meacham Blvd., Room 663, Fort Worth,

Texas 76137.

The referenced service information may be obtained from Robinson

Helicopter Company, 2901 Airport Drive, Torrance, California 90506.

FOR FURTHER INFORMATION CONTACT: Ms. Elizabeth Bumann, Aerospace

Engineer, FAA, Los Angeles Aircraft Certification Office, 3960

Paramount Blvd., Lakewood, California 90712; telephone (310) 627-5265,

fax (310) 627-5210.

SUPPLEMENTARY INFORMATION: On August 29, 1996, the FAA issued priority

letter AD 96-18-22, applicable to Robinson Model R44 helicopters, which

requires an inspection of the mating surfaces of the gearbox components

for pitting, elongated bolt holes, or machining grooves, and

replacement of the gearbox if elongated bolt holes, machining grooves,

or an improper amount of pitting is discovered; and replacement of the

18 bolts and washers that attach the gear to the gear carrier. That

action was prompted by inflight failure of the gearbox on a French-

registered Model R44 helicopter that resulted in an accident. An

inspection of the gearbox revealed that the 18 bolts securing the gear,

part number (P/N) C146-3, to the gear carrier, P/N C268-2, had lost

clamping torque due to the differences in the mating surface finish of

these components. As the rough surface of the gear seated into the

smoother surface of the gear carrier, the bolts lost clamping torque,

resulting in fretting and failure of the gear carrier. Inspections of

two other gearboxes that were returned to the manufacturer for overhaul

and maintenance revealed that the bolts securing the gear to the gear

carrier had also lost clamping torque. Prior to October 31, 1995,

Robinson did not have a requirement in their receiving inspections to

verify that the surface finish of the gear was completed in accordance

with the type design. As a result, gears have been found to have an

improper surface finish. This condition, if not corrected, could result

in loosening of the bolts securing the gear to the gear carrier, which

could lead to fatigue failure of the gear carrier within the gearbox,

and subsequent loss of power to the main rotor which could lead to a

forced landing.

Since the unsafe condition described is likely to exist or develop

on other Robinson Model R44 helicopters of the same type design, the

FAA issued priority letter AD 96-18-22 to prevent fatigue failure of

the gear carrier within the gearbox, and subsequent loss of power to

the main rotor which could lead to a forced landing. The AD requires,

before further flight, an inspection of the gearbox components for

pitting, elongated holes, or machining grooves (which appear similar to

grooves on a phonograph record) that can be felt with a fingernail, and

replacement of the gearbox with an airworthy gearbox if pits greater

than 0.001-inch deep, elongated holes, or machining grooves are

discovered on a mating surface; and replacement of the 18 bolts and

washers that attach the gear to the gear carrier with NAS6606-5 bolts

and spacers, P/N C130-29.

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 August 29, 1996 to all known U.S. owners and operators of

Robinson Model R44 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.

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

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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. 96-SW25-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:

AD 96-18-22 Robinson Helicopter Company: Amendment 39-9779. Docket

No. 96-SW-25-AD.

Applicability: Model R44 helicopters, with main rotor gearbox

(gearbox), part number (P/N) C006-1, Revisions A through P,

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 (v) 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 before further flight, unless accomplished

previously. To prevent loosening of the bolts securing the gear to

the gear carrier, which could lead to fatigue failure of the gear

carrier assembly (gear carrier) within the gearbox, and subsequent

loss of power to the main rotor which could lead to a forced

landing, accomplish the following:

(a) Drain the oil from the gearbox, part number (P/N) C006-1,

and remove the gearbox from helicopter.

(b) Lay the gearbox on its side with input yoke up. Loosen the

eight cap screws attaching the mast tube to the gearbox, but do not

remove the screws. Remove the twelve bolts and six cap screws

holding the sump and baffle in place (Figure 1). Note the location

of ground wires.

(c) Gently remove the sump, using care to keep all shim stacks

on their respective bolts. With the bolts still attached to the

sump, replace the nuts on the bolts and finger-tighten to retain the

shim stacks (shim stack is the same at each location). Discard the

O-Ring.

(d) Bend out the locking tabs on lockwashers, P/N C269-1 and P/N

C269-2, and remove the spanner nuts, P/N C153-1, from the main rotor

shaft. A scrap main rotor hub bolt, or equivalent, inserted through

the teeter hinge bolt hole in the main rotor shaft may be used to

react torque; clamp the bolt in a vice or fasten to a work bench. Do

not clamp the main rotor shaft. Retain the spanner nuts and discard

the lockwashers.

(e) Remove the gear carrier from the main rotor shaft. Mark the

gear and gear carrier for alignment during reassembly. Remove the 18

NAS6606-3 bolts attaching the gear to the gear carrier and remove

the gear. Discard the bolts, washers, and nuts.

(f) Clean the main rotor shaft splines, shoulder, and threads

with methyl-ethyl ketone or a comparable solvent that leaves no

residue upon evaporation. Clean the gear and gear carrier with the

solvent.

(g) Using a Scotch-Brite pad or 320 grit (or finer) sandpaper

and a flat block, remove any fretting or stains from the mating

surfaces of both the gear and the gear carrier. Visually inspect the

mating surfaces around all 18 holes for signs of pitting, elongated

holes, or machining grooves (which appear similar to grooves on a

phonograph record) that can be felt with a fingernail. If pits

greater than 0.001-inch deep, elongated holes, or machining grooves

are discovered on a mating surface, replace the gearbox with an

airworthy gearbox.

(h) Align the gear to the gear carrier and install NAS6606-5

bolts, spacers, P/N C130-29, and MS21042L6 nuts in 18 places (Figure

2). Keep the mating surfaces and hardware dry, clean, and free of

oil. Torque the nuts to 40 ft.-lb. (includes self-locking torque)

using the torquing sequence shown on Figure 3.

(i) Install the gear carrier on the main rotor shaft. Keep the

main rotor shaft clamping shoulder and the gear carrier clean and

dry during reassembly.

(j) For gearboxes, P/N C006-1, Revision P, use the following

torques for paragraphs (k) and (m): 560 ft.-lb. to seat the gear

carrier; 420-480 ft.-lb. for the first nut; and, 280-320 ft.-lb. for

the second nut.

(k) Install an unused lockwasher, P/N C269-2. Apply anti-seize,

P/N A257-9, or Loctite Anti-seize 767, to the main rotor shaft

threads and to the chamfered-side face and threads of one spanner

nut and install the nut with the chamfered side against the

lockwasher. Verify the pins are aligned with the holes in the

lockwasher. For Revision A through O gearboxes: Torque the nut to

370 ft.-lb. to seat the gear carrier; loosen the nut and retorque to

280-320 ft.-lb., as required to align the two lockwasher tabs with

the nut. Bend the two tabs into the nut and visually inspect the

edges of the bent tabs for cracks.

(l) Before installing the unused lockwasher, P/N C2691, note

that the edges are sharp on one side and rounded on the other. De-

burr the sharp edges on two opposite tabs (Figure 2). This will

reduce the chance of cracking when these tabs are bent. Install the

lockwasher with the de-burred edges toward the first nut.

(m) Apply anti-seize, P/N A257-9, or Loctite Anti-seize 767, to

the chamfered-side face and threads of the second nut. Align the two

de-burred tabs with the first nut and install the second nut with

the chamfered side against the lockwasher. Hand-tighten the nut to

hold the lockwasher in place. Bend the two de-burred tabs to lock

the first nut. For

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Revision A through Revision O gearboxes: Torque the second nut to

180-220 ft.-lb., as required to align two washer tabs. Bend the two

tabs to lock the second nut.

(n) Verify that all six bent tabs properly engage the nuts and

visually inspect the edges of the bent tabs for cracks. Replace any

cracked lockwashers. Remove any excess anti-seize.

(o) Lubricate the unused O-Ring, P/N C215-279, with oil, P/N

A257-2, and install the O-Ring on the sump. Clean and visually

inspect the sealing surface of the gearbox housing. Lightly

lubricate the sealing surface with oil, P/N A257-2.

(p) Install the sump on the gearbox housing, using care not to

damage the O-Ring.

(q) Install the baffle, P/N C747-1, and all the sump attaching

hardware. Ensure all the sump bolts have the same shim stack as

before. The threaded cap screws can damage the shim stack if not

installed properly. Install the ground wires using NAS6604-15, -16,

or -17 bolts (the other 11 bolts are NAS6604-15 bolts).

(r) Torque the sump bolts and drain plug assembly as follows:

Twelve lock nuts on NAS6604 bolts, 120 in.-lb.(includes locking

torque); six NAS1352-4H16P cap screws, 120 in.-lb. and safety wire;

A7260 drain plug assembly large hex, 150 in.-lb. and safety wire;

small hex, 75 in.-lb. and safety wire.

(s) Torque the eight NAS1356-6H24P cap screws attaching the mast

tube to the gearbox to 220 in.-lb. and safety wire.

(t) Reinstall the gearbox. Fill the gearbox with oil, P/N A257-

2, to the middle of the sight glass. Perform the main rotor balance

procedures.

(u) Report the serial number of any gearbox that has been

replaced in accordance with paragraph (g) of this AD, within 10 days

after the inspection to Mr. Randall Erwin, Principal Inspector, Los

Angeles Manufacturing Inspection District Office, FAA, Northwest

Mountain Region, 3960 Paramount Blvd., Lakewood, California 90712,

telephone (310) 627-5294, fax (310) 627-5293. Reporting requirements

have been approved by the Office of Management and Budget and

assigned OMB control number 2120-0056.

(v) 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, Los Angeles Aircraft Certification

Office, FAA. Operators shall submit their requests through an FAA

Principal Maintenance Inspector, who may concur or comment and then

send it to the Manager, Los Angeles Aircraft Certification Office.

Note 2: Information concerning the existence of approved

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

obtained from the Los Angeles Aircraft Certification Office.

(w) Compliance with Robinson Helicopter Company Service Bulletin

SB-15, dated August 2, 1996, and the reporting requirements

contained in paragraph (u) of this AD is an acceptable means of

compliance with this AD.

(x) 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.

(y) This amendment becomes effective on October 25, 1996, to all

persons except those persons to whom it was made immediately

effective by priority letter AD 96-18-22, issued August 29, 1996,

which contained the requirements of this amendment.

BILLING CODE 4910-13-U

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[GRAPHIC] [TIFF OMITTED] TR10SE96.000

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Issued in Fort Worth, Texas, on September 30, 1996.

Eric Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 96-26019 Filed 10-9-96; 8:45 am]

BILLING CODE 4910-13-U