[Federal Register Volume 61, Number 198 (Thursday, October 10, 1996)]
[Rules and Regulations]
[Pages 53046-53050]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-26019]


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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

[[Page 53047]]

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

[[Page 53048]]

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

[[Page 53049]]

[GRAPHIC] [TIFF OMITTED] TR10SE96.000



[[Page 53050]]

    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