[Federal Register Volume 60, Number 114 (Wednesday, June 14, 1995)]
[Rules and Regulations]
[Pages 31236-31240]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-14445]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 94-SW-27-AD; Amendment 39-9276; AD 95-06-03]


Airworthiness Directives; Robinson Helicopter Company Model R22 
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) 95-06-03 which was sent 
previously to all known U.S. owners and operators of Robinson 
Helicopter Company (Robinson) Model R22 helicopters by individual 
letters. This AD requires an inspection and modification of the main 
rotor (M/R) gearbox. This amendment is prompted by a report of an 
incident involving a Model R22 helicopter in which the two M/R mast 
spanner nuts (nuts) became loose, resulting in failure of the M/R mast 
support structure. The actions specified by this AD are intended to 
prevent M/R separation and subsequent loss of control of the 
helicopter.

DATES: Effective on June 29, 1995, to all persons except those persons 
to whom it was made immediately effective by priority letter AD 95-06-
03, issued on March 8, 1995, which contained the requirements of this 
amendment.
    Comments for inclusion in the Rules Docket must be received on or 
before August 14, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Assistant Chief Counsel, Attention: 
Rules Docket No. 94-SW-27-AD, 2601 Meacham Blvd., Room 663, Fort Worth, 
Texas 76137.

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 March 8, 1995, the FAA issued priority 
letter AD 95-06-03, applicable to Robinson R22 helicopters, which 
requires, within 25 hours time-in-service (TIS) after the effective 
date of this AD, removal and disassembly of the M/R gearbox; 
measurement of the break-loose torque value of the upper spanner nut; 
replacement of the lock washers; increasing the torque values of the 
two spanner nuts; reassembly and reinstallation of the M/R gearbox; and 
verification of the M/R balance in accordance with the applicable 
maintenance manual. That action was prompted by an incident reported by 
the Civil Aviation Authority (CAA) of New Zealand involving failure of 
the main rotor (M/R) mast support structure. An investigation revealed 
that the two M/R mast spanner nuts (nuts) became loose and allowed the 
M/R shaft to pull through the retention bearing in the
M/R gearbox. As the loads transferred from the M/R gearbox bearing to 
the top of the mast, the rivets that attach the mast bearing outer 
housing to the M/R shaft sheared, resulting in failure of the M/R mast 
support structure.
    Prior to June 15, 1992, the M/R gearbox assembly, P/N A006-1 
Revisions A through Z, may have been assembled with paint on the 
clamping surface of the M/R shaft, preventing a good clamping surface 
for the nuts. Two earlier incidents in Australia prompted the 
Commonwealth of Australia CAA to issue CAA AD/R22/35, dated September 
1992, to inspect the nuts for looseness and increase the nut torque 
values. The FAA did not issue an AD at that time due to inconclusive 
information from the two isolated incidents. The compliance procedure 
of this AD differs from CAA AD/R22/35 by requiring replacement of the 
lock washer, part number (P/N) A269-1, located between the mast bearing 
and the upper nut, with a different lock washer, P/N A269-2. The torque 
values on both nuts have also been increased. The FAA has determined 
that under-torqued nuts may become loose and create an unsafe 
condition. Due to the criticality of ensuring that the nuts are 
properly torqued, this AD is being issued immediately to correct an 
unsafe condition. That condition, if not corrected, could result in M/R 
separation and subsequent loss of control of the helicopter.
    Since the unsafe condition described is likely to exist or develop 
on other Robinson Model R22 helicopters of the same type design, the 
FAA issued priority letter AD 95-06-03 to prevent M/R separation and 
subsequent loss of control of the helicopter. The AD requires, within 
25 hours time-in-service (TIS), removal and disassembly of the M/R 
gearbox; measurement of the break-loose torque value of the upper 
spanner nut; replacement of the lock washers; increasing the torque 
values of the two spanner nuts; reassembly and reinstallation of the M/
R gearbox; and verification of the M/R balance in accordance with the 
applicable maintenance manual.
    Since the issuance of that AD, the FAA has received information 
that Robinson Helicopter Company may not 

[[Page 31237]]
be providing to all individuals the MT-124 tool required to remove and 
install the nuts. The relevant AD Note has been revised to state that 
individuals may request an alternative method of compliance to use a 
different nut socket in lieu of the MT-124 tool. Also, Note 1 has been 
added to the AD clarifying the applicability to helicopters that have 
been modified, altered, or repaired in the area subject to the 
requirements of this AD. The addition of this note changed the 
numbering of the subsequent notes. Paragraph (a) of the AD has also 
been changed to allow use of an unserviceable M/R hub bolt or \5/8\-
inch diameter bolt to counteract torque when removing the nuts. 
Finally, nomenclature and part numbers have been added throughout the 
AD for clarification. The FAA has determined that these minor changes 
will neither change the meaning or scope of the AD nor increase any 
burden on any operator.
    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 March 8, 1995, to all known U.S. owners and operators of 
Robinson Model R22 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 
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. 94-SW-27-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. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

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

95-06-03  Robinson Helicopter Company:
Amendment 39-9276. Docket No. 94-SW-27-AD.

    Applicability: Model R22 helicopters with main rotor gearbox 
(gearbox), part number (P/N) A006-1, Revisions A through Z, 
manufactured or overhauled prior to June 15, 1992, 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 (b) 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.
    Note 2: The revision level (revision letter) of the gearbox can 
be found on the data plate next to the sight glass.

    Compliance: Required as indicated, unless accomplished 
previously. To prevent main rotor (M/R) separation and subsequent 
loss of control of the helicopter, accomplish the following:
    (a) Within 25 hours time-in-service after the effective date of 
this AD, inspect and modify the gearbox in accordance with the 
following:
    (1) Remove the gearbox in accordance with the applicable 
maintenance manual.
    (2) Drain the gearbox by removing the chip detector housing.
    (3) Perform the following inspection and torquing of the shaft 
retaining nuts.

    Note 3: A special tool, a spanner nut socket, P/N MT124-1, may 
be obtained from Robinson Helicopter Company. If that tool is not 
available, individuals may propose using a different nut socket in 
accordance with paragraph (b) of this AD.

    (i) Lay the gearbox on its side using care to prevent damage to 
the slider tube. Remove the eight NAS1291-4 nuts and two MS20074-04-
10 hex head cap screws holding the sump in place.
    (ii) Gently remove the sump and discard the O-ring, using care 
to keep all washer-shims on their respective bolts. With the bolts 
still attached to the sump, replace the sump nuts on the bolts to 
retain the washer-shims (the washer-shim stack is the same at each 
location). Hand-tighten the nuts.
    (iii) Bend back the two lock washer tabs locking the lower nut, 
P/N A153-1. Insert an 

[[Page 31238]]
unserviceable M/R hub bolt or a \5/8\-inch diameter bolt through the 
teeter hinge bolt hole in the M/R shaft to counteract torque. Clamp 
the unserviceable M/R hub bolt or the \5/8\-inch diameter bolt in a 
vise or otherwise fasten it to a workbench. Do not clamp the M/R 
shaft. Remove the lower nut from the
M/R shaft using a socket, P/N MT124-1, or an FAA-approved equivalent 
tool. Remove and discard the lower lock washer, P/N A269-1.
    (iv) Bend back the two lock washer tabs locking the upper nut, 
P/N A153-1. Remove the upper nut, measuring the torque required to 
break the nut loose. Remove and discard the upper lock washer, P/N 
A269-1.
    (v) If the upper nut required more than 10 ft.-lb. torque to 
break loose, proceed to paragraph (a)(3)(vi). If the upper nut 
required 10 ft.-lb. torque or less to break loose, report within 5 
days the M/R gearbox P/N and break-loose torque value to the 
Propulsion Manager, Los Angeles Aircraft Certification Office, 3960 
Paramount Blvd., Lakewood, California 90712. Reporting requirements 
have been approved by the Office of Management and Budget and 
assigned OMB control number 2120-0056. Remove the gear carrier from 
the M/R shaft. Inspect the splines and clamping surfaces on both the 
shaft and gear carrier for pitting, galling, or scoring of surfaces. 
Replace any unairworthy parts. If the inspection revealed no 
pitting, galling, or scoring of surfaces, remove any paint from the 
clamping surface on the shaft using either paint remover or a 
plastic or wooden scraper, and ensure the surface is smooth and 
clean. Reassemble the gear carrier to the shaft.
    (vi) Inspect the two dowels or roll pins in the gear carrier for 
damaged surfaces. Dowels or roll pins must protrude 0.045 to 0.055 
inches for proper engagement with the lock washer, P/N A269-2. Also 
clean the nuts, M/R shaft threads, and sump, using methyl-ethyl-
ketone (MEK) or Trichlorethane (1,1,1, TCE) before reassembly.
    (vii) Install a lock washer, P/N A269-2. Apply anti-seize 
(Loctite Anti-seize 767), P/N A257-9, to the M/R shaft threads and 
to the chamfered-side face and threads of one nut and install the 
nut with the chamfered side against the lock washer. Verify that the 
dowels or roll pins are aligned with the holes in the lock washer. 
Torque the nut to between 170 and 200 ft.-lb., as required to align 
two lock washer tabs (tabs) with the nut. Do not untorque the nut to 
align the lock washer tabs with the nut. For the two tabs that are 
aligned with the recessed areas, bend down the tabs into the 
recessed areas of the nut and inspect the edges of the bent tabs for 
cracks.
    (viii) Before installing the lock washer,
P/N A269-1, note that the edges are sharp on one side and rounded on 
the other. De-burr the sharp edges on two opposite tabs (see figure 
1). This will reduce the chance of cracking when these tabs are bent 
up. Install the lock washer with the rounded edges toward the 
installed nut.
    (ix) Apply anti-seize, P/N A257-9, to the chamfered-side face 
and threads of the lower nut. Align the two de-burred tabs with the 
upper nut and install the lower nut with the chamfered side against 
the lock washer. Hand-tighten the nut to hold the washer in place. 
Bend the two de-burred tabs up to lock with the upper nut. Torque 
the lower nut to between 90 and 120 ft.-lb., as required to align 
the two additional tabs. Do not untorque the nut to align the lock 
washer tabs with the nut. For the two tabs that are aligned with the 
recessed areas, bend down the tabs into the recessed areas of the 
nut to lock the lower nut.
    (x) Verify that all six bent tabs properly engage the nuts (four 
tabs to the upper nut and two to the lower nut), and inspect the 
edges of the bent tabs for cracks. Replace any cracked lock washers. 
Remove excess anti-seize compound.
    (xi) Lubricate the O-ring, P/N A215-271, with oil, P/N A257-2, 
and install the O-ring on the sump. Clean and inspect the sealing 
surface of the gearbox housing for smoothness. Lightly lubricate the 
sealing surface with oil, P/N A257-2.
    (xii) Reinstall the sump onto the gearbox housing using the same 
washer-shim stacks that were removed in accordance with paragraph 
(a)(3)(ii) of this AD. Torque the sump bolts and chip detector as 
follows:
    (A) For the eight NAS1291-4 nuts on the AN4 bolts for the sump: 
90 in.-lb. of torque (includes nut self-locking torque);
    (B) For the two cap screws, P/N MS20074: 60 in.-lb. of torque 
and install safety wire;
    (C) For the chip detector, P/N A7260, (large nut): 150 in.-lb. 
of torque and install safety wire;
    (D) For the chip detector, P/N A7260, (small nut): 75 in.-lb. of 
torque and install safety wire.

    Note 4: Be sure to install ground wires under the nut located 
aft of the forward right-hand mount.

    (4) Reinstall the gearbox in accordance with the applicable 
maintenance manual.
    (5) Fill the gearbox with oil, P/N A257-2, to the middle of the 
sight glass.
    (6) Verify the M/R balance in accordance with the applicable 
maintenance manual.
    (b) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used when 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 5: 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.

    (c) 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.
    (d) This amendment becomes effective on June 29, 1995, to all 
persons except those persons to whom it was made immediately 
effective by Priority Letter AD 95-06-03, issued March 8, 1995, 
which contained the requirements of this amendment.

BILLING CODE 4910-13-P

[[Page 31239]]
[GRAPHIC][TIFF OMITTED]TR14JN95.000



BILLING CODE 4910-13-C

[[Page 31240]]

    Issued in Fort Worth, Texas, on June 7, 1995.
Mark R. Schilling,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 95-14445 Filed 6-13-95; 8:45 am]
BILLING CODE 4910-13-P