[Federal Register Volume 60, Number 225 (Wednesday, November 22, 1995)]
[Rules and Regulations]
[Pages 57824-57832]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-28537]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-SW-06-AD; Amendment 39-9425; AD 95-23-05]


Airworthiness Directives; Robinson Helicopter Company Model R22 
Series Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to Robinson Helicopter Company Model R22 series 
helicopters, that currently requires an inspection and repetitive 
visual checks for slippage of the tail rotor (T/R) drive and 
replacement of the T/R gearbox, if necessary. This amendment requires 
disassembly of the T/R gearbox to verify the installation of the input 
and output shaft keys (keys) between the input and output pinions and 
their respective shafts. This amendment is prompted by two incidents in 
which the key was not installed between the output shaft and 

[[Page 57825]]
the output pinion during assembly of the T/R gearbox at Robinson 
Helicopter Company. The actions specified by this AD are intended to 
prevent slippage of the T/R drive, loss of directional control, and 
subsequent loss of control of the helicopter.

EFFECTIVE DATE: December 27, 1995.

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: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by superseding AD 94-17-07, 
Amendment 39-9059 (59 FR 55203, November 4, 1994), which is applicable 
to Robinson Helicopter Company Model R22 series helicopters, was 
published in the Federal Register on May 26, 1995 (60 FR 27926). That 
action proposed to require an inspection and repetitive visual checks 
for slippage of the T/R drive until the T/R gearbox is disassembled to 
verify installation of the shaft keys. It also proposed to allow owner/
operator daily preflight checks for misalignment of the alignment dots 
that are installed on the tail cone skin and the drive shaft flange. 
These checks do not require the use of tools, precision measuring 
equipment, training, pilot logbook endorsements, or the use of 
technical data not contained in the AD. Additionally, these checks are 
considered part of the normal pilot ``Before Takeoff'' and ``After 
Landing'' checks. These checks are additional measures to detect 
slippage of the T/R drive until installation of the keys is verified. 
These checks may be performed by an owner/operator holding at least a 
private pilot certificate, but must be entered into the aircraft 
records showing compliance with this AD in accordance with sections 
43.11 and 91.417(a)(2)(v) of the Federal Aviation Regulations.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comment received.
    The manufacturer was the only commenter, and it believes that AD 
94-17-07, which required a one-time application of a 35-pound load to 
the tip of a tail rotor blade to induce slipping of the shaft and a 
daily ``dot alignment'' check for slippage, provides adequate 
safeguards to assure the safety of the helicopter. The manufacturer 
notes that proof tests were performed on various gearboxes with keys 
removed and the load required to cause slippage varied between 14 and 
27 pounds. The load tests combined with no reports of additional 
defective gearboxes leads the manufacturer to assert that the one-time 
application of the 35-pound load should be the terminating action. The 
FAA does not agree. The FAA has determined that the one-time 
application of a 35-pound weight on the tip of the tail rotor blade to 
test for slippage of the shaft cannot be considered terminating action 
for Priority Letter 94-17-07. Slippage is a function of surface 
friction of the material(s) and the attaching hardware clamping 
pressure, which may vary due to the condition of the gearbox. A no-
slippage condition does not ensure that the keys have been installed. 
Also, there is no assurance that the torque of the retaining nuts will 
be maintained until the next gearbox overhaul. Although no cases of 
slippage have been reported as a result of Priority Letter AD 94-17-07, 
there is no assurance that the keys have been installed.
     The FAA has determined that air safety and the public interest 
require the adoption of the rule as proposed except for deleting 
proposed paragraph (a)(2) since this procedure is not necessary to 
check for the misalignment of dots, deleting the requirement to vibro-
etch the AD number on the output cartridge since the requirement to 
vibro-etch the AD number on the input flange is sufficient to identify 
installation of the keys, exempting from the requirements of this AD 
196 additional serial-numbered gearboxes that have been verified by the 
manufacturer to have both keys installed, adding certain non-
substantive, descriptive, clarifying words, adding a clarifying figure, 
and making various editorial changes. The FAA has determined that these 
changes will neither increase the economic burden on any operator nor 
increase the scope of the AD.
    The FAA estimates that 500 helicopters of U.S. registry will be 
affected by this AD, that it will take approximately 5 work hours per 
helicopter to accomplish the required actions, and that the average 
labor rate is $60 per work hour. Based on these figures, the total cost 
impact of the AD on U.S. operators is estimated to be $150,000.
    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.
    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) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it 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, Incorporation by 
reference, 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), 40101, 40113, 44701.


Sec. 39.13  [Amended]

    Section 39.13 is amended by removing Amendment 39-9059 (59 FR 
55203, November 4, 1994), and by adding a new airworthiness directive 
(AD), Amendment 39-9425, to read as follows:

AD 95-23-05 Robinson Helicopter Company: Amendment 39-9425. Docket 
No. 95-SW-06-AD. Supersedes AD 94-17-07, Amendment 39-9059.

    Applicability: Model R22 series helicopters certified in any 
category, with tail rotor (T/R) gearboxes that were manufactured or 
overhauled by Robinson Helicopter Company prior to June 8, 1992. The 
following gearbox serial numbers have been determined to have the T/
R input and output shaft keys installed and are therefore exempt 
from this AD: 0012, 0013, 0014, 0015, 0018, 0020, 0021, 0030, 0040, 
0054, 0062, 0079, 0091, 0095, 0098, 0107, 0108, 0121, 0134, 0137, 
0146, 0149, 0153, 0169, 0179, 0184, 0185, 0191, 0193, 0201, 0205, 
0227, 0228, 0235, 0239, 0241, 0248, 0258, 0262, 0269, 0272, 0277, 
0280, 0296, 0304, 0321, 0333, 0342, 0345, 0346, 0355, 0365, 0385, 
0387, 0392, 0415, 0417, 0424, 0431, 0432, 0439, 0444, 0447, 0503, 
0504, 0505, 0525, 0542, 0546, 0547, 0548, 0554, 0558, 0559, 0565, 
0574, 0576, 0579, 0592, 0594, 0597, 0603, 0604, 0605, 0615, 0619, 
0632, 0634, 0639, 0641, 0644, 0650, 

[[Page 57826]]
0656, 0662, 0663, 0665, 0674, 0686, 0689, 0696, 0697, 0700, 0701, 0702, 
0707, 0722, 0734, 0735, 0736, 0742, 0755, 0756, 0759, 0767, 0777, 
0778, 0784, 0786, 0805, 0811, 0832, 0836, 0839, 0842, 0845, 0850, 
0862, 0863, 0866, 0868, 0880, 0885, 0887, 0892, 0926, 0937, 0939, 
0952, 0970, 0983, 0986, 0996, 0997, 0998, 0999, 1007, 1016, 1018, 
1021, 1029, 1030, 1035, 1048, 1062, 1072, 1078, 1081, 1087, 1104, 
1116, 1121, 1126, 1129, 1132, 1141, 1151, 1176, 1182, 1186, 1187, 
1197, 1199, 1205, 1208, 1217, 1222, 1224, 1228, 1233, 1237, 1245, 
1249, 1252, 1254, 1255, 1269, 1274, 1290, 1293, 1299, 1301, 1307, 
1310, 1311, 1323, 1328, 1330, 1333, 1338, 1339, 1341, 1342, 1350, 
1351, 1361, 1371, 1379, 1385, 1388, 1392, 1404, 1412, 1414, 1428, 
1429, 1435, 1438, 1442, 1450, 1460, 1468, 1494, 1499, 1505, 1508, 
1509, 1512, 1514, 1526, 1541, 1544, 1565, 1578, 1586, 1593, 1595, 
1597, 1605, 1610, 1627, 1628, 1629, 1636, 1643, 1647, 1648, 1652, 
1654, 1661, 1676, 1677, 1686, 1687, 1698, 1701, 1702, 1706, 1708, 
1710, 1714, 1724, 1731, 1732, 1738, 1739, 1741, 1750, 1752, 1754, 
1757, 1759, 1766, 1767, 1769, 1783, 1785, 1786, 1800, 1803, 1807, 
1808, 1814, 1816, 1823, 1828, 1830, 1833, 1837, 1844, 1846, 1851, 
1852, 1858, 1861, 1868, 1869, 1871, 1874, 1886, 1889, 1893, 1898, 
1899, 1909, 1911, 1912, 1913, 1920, 1922, 1927, 1928, 1948, 1951, 
1959, 1961, 1963, 1965, 1966, 1974, 1978, 1983, 1992, 1996, 2002, 
2025, 2028, 2034, 2037, 2043, 2051, 2058, 2071, 2100, 2101, 2103, 
2108, 2115, 2126, 2129, 2136, 2160, 2166, 2170, 2180, 2182, 2193, 
2197, 2203, 2216, 2231, 2242, 2254, 2265, 2269, 2272, 2279, 2280, 
2283, 2285, 2289, 2294, 2298, 2299, 2303, 2304, 2308, 2314, 2337, 
2346, 2357, 2360, 2362, 2364, 2377, 2380, 2381, 2387, 2395, 2406, 
2408, 2410, 2414, 2416, 2419, 2420, 2421, 2422, 2423, 2425, 2431, 
2435, 2436, 2459, 2467, 2479, 2492, 2498, 2513, 2529, 2531, 2536, 
2539, 2551, 2556, 2557, 2574, 2579, 2582, 2587, 2591, 2604, 2605, 
2607, 2609, 2616, 2627, 2634, 2642, 2651, 2672, 2682, 2683, 2687, 
2690, 2697, 2716, 2719, 2720, 2721, 2731, 2736, 2784, 2797, 2799, 
2815, 2826, 2841, 2842, 2845, 2862, 2863, 2873, 2937, 2945, 3004, 
3109.

    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 (d) 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 slippage of the T/R drive, loss of directional 
control, and subsequent loss of control of the helicopter, 
accomplish the following:
    (a) Before further flight, install alignment dots as follows: 
Remove the transparent inspection cover on the tail cone and rotate 
the T/R blades so that one blade leading edge is aligned with the 
tail cone centerline. Mark a dot on the tail cone skin aligned with 
the tip of the blade leading edge. With the same alignment, mark a 
dot on the centerline of the tail cone skin at the edge of the 
inspection hole, and mark a corresponding dot on the drive shaft 
flange (see figure 4).
    (b) Conduct the following daily preflight checks for 
misalignment of the alignment dots until compliance with paragraph 
(c) of this AD has been accomplished: Check for misalignment of the 
alignment dots installed on the tail cone skin and the drive shaft 
flange by rotating the T/R blade so that the alignment dot is 
visible in the inspection window and the tip of the T/R blade 
leading edge aligns with the dot on the tail cone skin. Ensure that 
the drive shaft flange dot is aligned with the dot on the centerline 
of the tail cone skin at the edge of the inspection window. If any 
misalignment is detected, before further flight, replace the T/R 
gearbox with an airworthy one that has been determined to have both 
the input and output keys installed in accordance with paragraph (c) 
of this AD or other FAA-approved procedures, or is exempt from the 
requirements of this AD as listed in the applicability section of 
this AD. The daily preflight checks required by this AD may be 
performed by an owner/operator holding at least a private pilot 
certificate and must be entered into the aircraft records showing 
compliance with paragraph (b) of this AD, in accordance with 
sections 43.11 and 91.417(a)(2)(v) of the Federal Aviation 
Regulations.
    (c) Within the next 100 hours time-in-service (TIS) after the 
effective date of this AD, or at the next annual inspection, 
whichever occurs first, verify installation of both the input and 
output shaft keys as follows:
    (1) Cut and remove the safety wire securing the chip detector to 
the sight gage on the T/R gearbox. Place a container under the T/R 
gearbox to catch the drained oil and remove the chip detector. 
Remove and discard the gasket on the chip detector.
    (2) Remove the T/R gearbox from the helicopter in accordance 
with the applicable maintenance manual.
    (3) Cut and remove the safety wire securing the filler vent plug 
to the sight gage on the T/R gearbox and remove the filler vent plug 
and sight gage. Remove and discard the gasket on the filler vent 
plug and sight gage.
    (4) Remove and disassemble the output cartridge, P/N A111-1, 
from the T/R gearbox case, P/N A109-1 (see figure 1) as follows:
    (i) Place a mark across the gear case, P/N A109-1, and output 
cartridge, P/N A111-1, with a felt pen or grease pencil to ensure 
proper reassembly.
    (ii) Cut and remove the safety wire around the four MS20074-04-
06 bolts securing the output cartridge to the gear case. Remove and 
retain each of the four bolts and their associated AN960-416L 
washer(s), noting the washer stacks for reassembly. Separate the 
output cartridge from the gear case (see figure 1).
    (iii) Remove and discard the safety wire, MS16562-24 or 52-022-
094-0437 roll pin, and MS14145L6 or LCN6M-624 retaining nut. Remove 
the AN960-616L washer(s) and the washer, P/N A141-2, noting the 
washer(s) location for reassembly. Do not damage the output shaft, 
P/N A107-1, or the shim(s), P/N A118-1 through -6, located next to 
the flange of the output cartridge when removing the retaining nut.
    (iv) Visually inspect for the presence of the output shaft key, 
P/N A114-2, between the pinion gear, P/N A545-1, and the output 
shaft (see figure 2).
    (v) If the output shaft key is missing, replace the T/R gearbox 
with an airworthy gearbox that has been determined to have the 
output key installed. Report any T/R gearbox that has a missing key 
within 10 days after the inspection to the Manager, Los Angeles 
Manufacturing Inspection Office, FAA, Northwest Mountain Region, 
3960 Paramount Blvd., Lakewood, California 90712, telephone (310) 
627-5290, fax (310) 627-5293. Reporting requirements have been 
approved by the Office of Management and Budget and assigned OMB 
control number 2120-0056.
    (vi) If the output key is installed, reinstall the washer, P/N 
A141-2, and AN960-616L washer(s). Install an MS14145L6 or LCN6M-624 
retaining nut, and torque to 225-275 in.-lbs. Install a MS16562-24 
or 52-022-094-0437 roll pin, and safety wire using 0.032-inch 
stainless steel safety wire. The safety wire pigtail must be wrapped 
tightly around the retaining nut.
    (5) Remove and disassemble the input cartridge, P/N A110-1, from 
the T/R gear case, P/N A109-1, as follows:
    (i) Place two marks across the gear case, P/N A109-1, and input 
cartridge, P/N A110-1, with a felt pen or grease pencil to ensure 
proper reassembly.
    (ii) Cut and remove the safety wire around the four MS20074-04-
06 bolts securing the input cartridge to the gear case. Remove each 
of the four bolts and their associated AN960-416L washer(s), noting 
the washer stacks for reassembly. Separate the input cartridge from 
the gear case (see figure 1).
    (iii) Secure the input cartridge to a block of wood through the 
two bolt holes in the input shaft assembly, P/N A116-1 (see figure 
1). Place the block of wood in a vise. Remove and discard the safety 
wire, roll pin, and retaining nut. Remove the AN960-616L washer(s), 
and washer, P/N A141-1, noting the washer(s) location for 
reassembly. Do not damage the input shaft or shim(s), P/N A118-1 
through -6, located next to the flange of the input cartridge.
    (iv) Visually inspect for the presence of the input shaft key, 
P/N A114-1, between the gear, P/N A545-2, and the input shaft (see 
Note on figure 2).
    (v) If the input shaft key is missing, replace the T/R gearbox 
with an airworthy gearbox that has been determined to have the input 
key installed. Report any T/R gearbox that has a missing key within 
10 days after the inspection to the Manager, Los Angeles 
Manufacturing Inspection District Office, FAA, Northwest Mountain 
Region, 3960 

[[Page 57827]]
Paramount Blvd., Lakewood, California 90712, telephone (310) 627-5290, 
fax (310) 627-5293. Reporting requirements have been approved by the 
Office of Management and Budget, and assigned OMB control number 
2120-0056.
    (vi) If the input key is installed, reinstall the AN960-616L 
washer(s) and washer, P/N A141-1. Install an MS14145L6 or LCN6M-624 
retaining nut, and torque to 225-275 in.-lbs. Install a MS16562-24 
or 52-022-094-0437 roll pin and safety wire using 0.032-inch 
stainless steel safety wire. The safety wire pigtail must be wrapped 
tightly around the retaining nut. Remove the two bolts securing the 
input shaft assembly to the block of wood. Vibro-etch the final rule 
AD number on the input cartridge attachment flange.
    (6) Reassemble the input and output cartridges to the T/R case 
as follows:
    (i) Color the ``X'' marked on the pinion gear, P/N A545-1, (one 
tooth only) of the output cartridge and on the gear, P/N A545-2, 
(located on two consecutive teeth) of the input cartridge with a red 
marker to make reinstallation easier. Note that these three gear 
teeth may already be colored (see figure 3).
    (ii) Visually inspect the edge of the chamfers in the gear case, 
making sure they are round and smooth so that the O-ring will not be 
damaged upon installation.
    (iii) Remove and discard the O-ring on both the input cartridge 
and output cartridge. Replace the O-ring with National P/N AS142 
B46-70, or Parker P/N 2-142 N674-70 O-ring. Lubricate the 
replacement O-ring with oil, P/N A257-2, and install an O-ring on 
each cartridge.
    (iv) Reinstall the output cartridge on the gear case with the 
four MS20074-04-06 bolts and AN960-416L washer stacks that were 
removed in accordance with paragraph (c)(4)(ii). Reinstall the input 
cartridge on the gear case with the four MS20074-04-06 bolts and 
AN960-416L washer stacks that were removed in accordance with 
paragraph (c)(5)(ii). Do not torque the bolts at this time.

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[[Page 57832]]

    (v) Look through the sight gage opening while using a flashlight 
pointed into the filler vent hole to verify the gears are meshed 
properly. Gears are properly meshed when the ``X'' marked on the 
pinion gear of the output cartridge is between the two ``X's'' 
marked on the gear of the input cartridge (see figure 3). Do not 
torque the MS20074-04-06 bolts until both cartridges are installed 
on the case and the gears are properly meshed. Torque the output 
cartridge bolts to 60 in.-lbs. first, then torque the input 
cartridge bolts to 60 in.-lbs. Safety wire with 0.032-inch stainless 
steel safety wire.
    (vi) Reinstall sight gage with MS35769-11 or AN900-10 gasket. 
Oil threads to prevent threads from locking up. Torque to 200 in.-
lbs.
    (vii) Reinstall the chip detector with a MS35769-8 or AN900-9 
gasket after lubricating the threads with oil. Torque the chip 
detector to 150 in.-lbs. Safety wire the sight gage to the chip 
detector using 0.032-inch stainless steel safety wire.
    (viii) Fill the T/R gearbox with oil to the level indicated on 
the T/R sight glass decal. Reinstall the filler vent plug, P/N A610-
1, with a MS35769-9 or AN900-8 gasket, after lubricating the threads 
with oil.
    (ix) Inspect the T/R gearbox assembly to ensure that the shafts 
and gears rotate freely.
    (7) Reinstall the T/R gearbox onto the helicopter in accordance 
with the applicable maintenance manual. Verify that the oil level of 
the T/R gearbox is at the recommended mark on the sight glass.
    (d) 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 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.

    (e) 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.
    (f) This amendment becomes effective on December 27, 1995.

    Issued in Fort Worth, Texas, on November 2, 1995.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 95-28537 Filed 11-21-95; 8:45 am]
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