1. PLANNING INFORMATION

A. Effectivity

All S-70A/C (BlackHawkderivatives), and S-70B and S-70C(M) (SeaHawkand Naval Hawk

derivatives) as identified in Section 3.,A.

Components:

Tail Gearbox Output Bevel Gear, Part Number: 70358-06620.

B. Purpose

To perform a initial UT inspection in accordance with Special Service Instructions (SSI) No.

70-121A or, latest revision. The inspection process shall be completed by personnel

certified as Level II UT Technicians or equivalent, with Sikorsky Aircraft Corporation

administered training specific to use this procedure.

Background

A TGB experienced a fracture of the output shaft spline that drives the tail rotor blades.

The investigation has revealed that spline geometry and/or fretting found may be a

contributor. It also revealed that potential cracks can be identified using a UT inspection

probe without additional TGB disassembly. The UT inspection can be performed during the

phase maintenance inspections when the tail rotor servo and pitch beam shaft are

removed.

C. Description

All customers are requested to immediately contact Sikorsky Aircraft Corporation, at

telephone number (203) 416-4299, or e-mail: (www.sikorskywcs@sikorsky.com) to schedule

the required administered training. The administered training will be performed at Sikorsky

Aircraft production facility in Stratford, CT USA. We recommend that all required

administered training be completed within the compliance time of this Alert Service Bulletin

 

THIS ALERT SERVICE BULLETIN IS THE PROPERTY OF SIKORSKY AIRCRAFT CORPORATION AND IS PROTECTED UNDER THE COPYRIGHT LAWS OF THE

UNITED STATES AND OTHER COUNTRIES. THIS ALERT SERVICE BULLETIN IS DISTRIBUTED ONLY TO OWNERS/OPERATORS OF COMMERCIALLY-CERTIFIED

SIKORSKY HELICOPTERS AND SIKORSKY-AUTHORIZED LOGISTIC AND SERVICE CENTERS FOR THE PURPOSE OF FOSTERING THE SAFE AND EFFICIENT

OPERATION OF SUCH HELICOPTERS AND UNDER THE EXPRESS CONDITION THAT THE CONTENTS OF THIS ALERT SERVICE BULLETIN ARE NOT TO BE

DISCLOSED, REPRODUCED, OR DISTRIBUTED, IN WHOLE OR IN PART, TO ANY THIRD PARTY, OR ADAPTED AS A DERIVATIVE WORK, WITHOUT THE

EXPRESS DOCUMENTED CONSENT OF SIKORSKY AIRCRAFT CORPORATION. ANY ACT IN VIOLATION OF APPLICABLE LAW MAY RESULT IN CIVIL AND/OR

CRIMINAL PENALTIES.

LIMITED DISTRIBUTION R SIKORSKY AIRCRAFT CORPORATION 1999

ALL RIGHTS RESERVED

No. 70-06-28A

Subject: DRIVE SYSTEM - Tail Rotor Gearbox (TGB) - Output Shaft - Initial Ultrasonic Test (UT)

Inspection of

March 27/08 Page 1 of 5

Revision A - May 21/09
(ASB), but no later than three (3) months from the issue date of this ASB.

Helicopter is prepared for maintenance. The tail rotor box fairing is removed. The tail rotor

servo and pitch beam shaft are removed. A UT inspection is performed and data is analyzed. If

tail gearbox output bevel gear fails the UT inspection, contact Sikorsky Aircraft Corporation for

further instructions. If tail gearbox output bevel gear passes UT inspection, the tail rotor servo

and pitch beam are installed. Tail rotor box fairing is installed. Helicopter is returned to service.

D. Compliance

Compliance is essential. The UT inspection outlined herein is to be accomplished as follows:

(1) For S-70A and S-70C Derivatives, perform initial UT inspection at next scheduled phase

maintenance inspection when the tail rotor servo is scheduled to be removed.

(a) Recurring UT inspection for S-70A and S-70C derivatives shall be performed at the

next phase PMS-2 special inspection.

(2) For SH-60F Derivatives S-70B, S-70B-6, S-70C(M)-1, S-70C(M2), perform initial UT

inspection at next scheduled phase maintenance inspection regardless if tail rotor servo is

scheduled to be removed or not.

(a) Recurring UT inspection shall be performed at the next scheduled phase inspection

when the tail rotor servo is scheduled to be removed.

(3) For SH-60B Derivatives S-70B-2, S-70B-3, S-70B-7 tail gearbox assemblies, perform initial

UT inspection at next scheduled phase maintenance inspection regardless if tail rotor

servo is scheduled to be removed or not.

(a) Recurring UT inspection shall be performed at the next scheduled phase inspection

when the tail rotor servo is scheduled to be removed.

E. Approval

Inspection Item.

F. Manpower (Estimated)

No. of Men No. of Hours Man-Hours

Remove Details 2 2.0 4.0

Install Details 2 2.0 4.0

NOTE: Does not include time required to prepare helicopter for maintenance, or return helicopter to flight

status.

No. 70-06-28A

DRIVE SYSTEM - Tail Rotor Gearbox (TGB) - Output Shaft - Initial Ultrasonic Test (UT) Inspection of

1. PLANNING INFORMATION (Continued)

March 27/08 Page 2

Revision A - May 21/09
G. Tooling

Refer to SSI No. 70-121A, or latest revision.

H. Weight and Balance

None.

I. Electrical Load Data

Not Changed.

J. References

Applicable Maintenance Manual for Removal and Installation procedures.

K. Publications Affected

(1) Applicable Preventive Maintenance Services, PMS-2

(2) Applicable Preventive Maintenance Information Cards, Phase A/B/C/D

(3) Applicable Preventive Maintenance Information Cards, Phase A/B

(4) Ultrasonic Testing inspection requirement will be added to the

Applicable Special/Conditional/Preservation Maintenance Requirement Cards at a later date.

L. Attachment

Special Service Instructions No. 70-121A for UT inspection of tail gearbox output bevel gear.

2 MATERIAL INFORMATION

A. Consumable Material

None.

B. Bill of Material

None.

3. ACCOMPLISHMENT INSTRUCTIONS

A. Determine inspection requirements as follows:

No. 70-06-28A

DRIVE SYSTEM - Tail Rotor Gearbox (TGB) - Output Shaft - Initial Ultrasonic Test (UT) Inspection of

1. PLANNING INFORMATION (Continued)

March 27/08 Page 3

Revision A - May 21/09
(1) For BlackHawkand S-70 Derivatives:

If the helicopter has not been through a Preventive Maintenance Services, PMS-2

inspection, then perform the one-time UT inspection at the next scheduled PMS-2

inspection.

(2) For Naval Hawkderivatives which follow the Preventive Maintenance Information Cards,

Phase A/B/C/D, perform the one-time UT inspection at the next scheduled 175 hr phase

inspection.

(3) For SeaHawkderivatives which follow the Preventive Maintenance Information Cards,

Phase A/B schedule, perform the one-time UT inspection at the next scheduled 250 hr

phase inspection.

B. Perform an initial UT inspection as follows:

(1) Prepare helicopter for maintenance.

(2) Remove tail rotor servo and pitch beam shaft, refer to applicable Maintenance Manual.

NOTE: The inspection process shall be completed by personnel certified as Level II UT

Technicians, or equivalent with Sikorsky Aircraft administered training specific to

use this procedure.

(3) Perform an initial UT inspection in accordance with SSI No. 70-121A or, latest revision.

(4) Record information on attached Tail Gearbox Output Bevel Gear Data Sheet.

(5) Install tail rotor servo and pitch beam shaft. Refer to applicable Maintenance Manual.

(6) Install tail rotor box fairing. Refer to applicable Maintenance Manual.

(7) Return helicopter to service.

C. Record of Compliance

(1) Make an appropriate logbook/log card entry to show compliance with this ASB.

(2) Upon compliance with this Alert Service Bulletin, complete attached ALERT SERVICE

BULLETIN COMPLIANCE RECORD CARD and return it to Sikorsky Aircraft Corporation.

No. 70-06-28A

DRIVE SYSTEM - Tail Rotor Gearbox (TGB) - Output Shaft - Initial Ultrasonic Test (UT) Inspection of

3. ACCOMPLISHMENT INSTRUCTIONS (Continued)

March 27/08 Page 4

Revision A - May 21/09
D. Tail Gearbox Output Bevel Gear Data Sheet.

Record following information for all Tail Gearbox Assembly Output Bevel Gear and FAX to

Sikorsky Aircraft Corporation, WCS at (860) 998-7565.

Make copy of Tail Gearbox Output Bevel Gear Data Sheet for each helicopter recorded.

Customer/Operator Name: _____________________________________________________

Inspection Performed by:________________________________Date:___________________

Installed on Helicopter Serial Number:_____________________________________________

Tail Gearbox Assembly Serial No. ________________________________________________

Part Removed at Phase X________________________________________________________

UT Inspection Performed: Yes___________________No_______________________________

Part Accepted: Yes____________________________No______________________________

Part Failed: Yes____________________________No_________________________________

Signal Percent:_______________________________________________________________

FSH

Attach a Screen Image

No. 70-06-28A

DRIVE SYSTEM - Tail Rotor Gearbox (TGB) - Output Shaft - Initial Ultrasonic Test (UT) Inspection of

3. ACCOMPLISHMENT INSTRUCTIONS (Continued)

March 27/08 Page 5

Revision A - May 21/09
WCS PRODUCT SAFETY MANAGER

WORLDWIDE CUSTOMER SERVICE

,

No. 70-06-28A

DRIVE SYSTEM - Tail Rotor Gearbox (TGB) - Output Shaft - Initial Ultrasonic

Test (UT) Inspection of
BUSINESS REPLY MAIL

MAILSTOP: K100A

WCS PRODUCT SAFETY MANAGER

WORLDWIDE CUSTOMER SERVICE
May 21, 2009

TRANSMITTAL SHEET

Subject: SPECIAL SERVICE INSTRUCTIONS NO. 70-121 -TAIL GEAR BOX ASSEMBLY -Ultrasonic

Testing of Ultrasonic Inspection of

This page transmits Revision A to Special Service Instructions No. 70-121 dated March 27,

2008.

Special Service Instructions No. 70-121A supersedes Special Service Instructions No. 70-121

dated March 27, 2008.

The text changed by this Revision is indicated by a vertical line in the outer margin of the

page.

Revision Feature: The Instructions section, paragraph (5), has been revised to reflect new blade disposition

procedures. Paragraph (6), and Reference (a) have been deleted.

In Description section, revised 25% full screen height to allowable full screen height.

In References Section, changed ASB to reflect revison A.

In Instructions Section, step A. (1) a., added; including appropriate cable.

In Instructions Section, step A. (1) e., added: The 20.0-inch Non-metallic Rod (to be used

when cleaning shaft bore).

In Instructions Section, step A. (2) g., added: Mode:

In Instructions Section, step A. (2) h., added: Add six dB when scanning.

In Instructions Section, step A. (4), added: Point of contact for any questions information.

Renumbered remaining steps.

In Instructions Section, added steps (5) and revise existing procedures.

In Consumable Materials Section, added Lint-free Cleaning Cloth or Wipes information.

In Tools Required Section, added Feeler Gage and added steps (2) and (3) for Source.

Added new Figure 1 and renumbered remaining Figures.

Revised Figure 5.

Revised Figure 7.

SIKORSKY AIRCRAFT

Technical Directives Section

1 of 1
Sikorsky

A United Technologies Company

Sikorsky Aircraft Corporation 

6900 Main Street 

P.O. Box 9729 

Stratford, Connecticut 06497-9129 

(203) 386-4000

March 27, 2008 

Revision A – May 21/09 

Page 1 of 15

SPECIAL SERVICE INSTRUCTIONS No. 70-121A

Subject: TAIL GEAR BOX ASSEMBLY – Ultrasonic Testing of 

Purpose: To perform an inspection using ultrasonic testing process. 

Model: All S-70A/C (Blackhawk derivatives), and S-70B and S-70C(M) (Seahawk and Naval Hawk 

derivatives). 

Description: Helicopter is prepared for maintenance. Tail rotor fairing is removed. Tail rotor servo and 

pitch beam shaft are removed. Ultrasonic test (UT) inspection is performed on tail gear box 

output bevel gear. Any UT signals in the inspection area that exceed allowable full screen 

height (FSH) UT are to be reported to Sikorsky Aircraft Corporation. If the UT signals appear 

to be near allowable FSH, re-oil the bore and reinspect the area in question. If on second 

inspection the same result is noted, clean the bore and reinstall the tail rotor servo, pitch 

beam shaft, and tail rotor fairing. Helicopter is returned to service. 

References: (a) Applicable Maintenance Manual. 

(b) Alert Service Bulletin 70-06-28A or latest revision. 

Effectivity: All S-70 A/C helicopters (Blackhawk derivatives), and S-70B and S-70C(M) helicopters 

(Seahawk and Naval Hawk derivatives). 

Component: Tail Gear box Output Bevel Gear p/n 70358-06620. 

Instructions: 

A. UT Inspection Procedure: 

(1) The following equipment shall be used: 

a. Ultrasonic Instrument: Sonatest, Panametrics (or equivalent) including appropriate cable. 

b. Ultrasonic Inspection Tool: Olympus HB 2344 (or equivalent as approved by Sikorsky Aircraft 

Corporation). 

c. Ultrasonic Couplant: Tail Gear box Oil (DOD-PRF-85734 preferred or MIL-PRF 23699). 

d. Calibration Standard: Ring - EWR203026. 

e. The 20.0 inch Non-metallic Rod (to be used when cleaning shaft bore). 

f. Reference Document: Tech Sheet 5047, latest revision. 

(2) Set ultrasonic test equipment for calibration as follows: 

a. Frequency: 10 MHZ. 

b. Range: 1.0 inch. 

c. Dampening: 50 Ohms. 
SPECIAL SERVICE INSTRUCTION NO. 70-121A 

d. Velocity: 0.1254”/microsecond. 

e. Delay/Zero: Exit point at “0” graticule (0.266”) or 3.998 μ Sec. 

f. Reject: Off. 

g. Mode: Pulse-Echo. 

h. Sensitivity Level: Set signal amplitude from Calibration Notch to 80% FSH (Figure 1). Add six 

dB when scanning. 

(3) Inspection: 

a. 80% FSH from ID Notch (10% baseline material signal in shaft). 

b. Scan Index: 1/16”. Refer to instructions in Section (4). 

c. Discontinuity Evaluation: Any positive signal appearing in output bevel gear spline area shall 

be evaluated. Signals allowable FSH or greater are cause for rejection. Remove retention 

plate to expose spline for evaluation. 

(4) Point of contact for any questions: 

a. Andy Voor: Telephone No. 1-(203) 383-7539. 

b. Mike Shakinovsky: Telephone No. 1-(203) 386-4935. 

(5) Perform ultrasonic test on tail gear box output bevel gear as follows: 

a. Calibrate instrument using calibration standard noted in Section (2.) (Figure 1). 

b. Adjust signal amplitude to 80% FSH from OD notch. Add 6dB to this reference for scanning 

(approximately 10% baseline material noise in shaft is acceptable). 

c. Clean tail gear box shaft bore as follows: 

1 Using dry lint free wipes clean the tail gear box shaft bore prior to inspection. Refrain 

from using any solvents or cleaners that could possibly contaminate the tail gear box. 

NOTE

Count number of wipes used and make sure they are all removed upon completion. 

2 Push wipes in from servo side out through rotor side of bore to avoid pushing dirt into 

tail gear box. 

NOTE

Make sure there is adequate oil coverage prior to performing inspection. 

d. Lubricate spline end bore with tail gear box oil as follows:

March 27, 2008 

Revision A – May 21/09 

Page 2 of 15
SPECIAL SERVICE INSTRUCTION NO. 70-121A 

NOTE

• Make sure the Transducer Wedge is tipped forward to allow insertion into the bore. 

• Make sure search unit is adequately coupled throughout inspection. A dry bore is 

usually indicated by increase friction of probe; reduction in amplitude of the front 

spline signal and/or baseline noise. If this condition is detected, recouple/lube and 

reinspect. 

• After ultrasonic tool is inserted, rotate it 360 degrees to spread the oil. 

e. Insert ultrasonic tool into rear bore from servo end of tail gear box and rotate to spread oil 

(Figure 2). 

f. Using a standard feeler gage, make sure there is a gap of 0.010 inches between probe head 

and shaft flange. If gap is less than 0.010 inches loosen screws 3/8 (0.375) inches apply 

Loctite 420 (or equivalent) to threads, then tighten screws to set shaft flange against feeler 

gage (Figure 6). 

g. Fully insert tool and locate large plug in rear bore. Maintain its position in rear bore while 

scanning at approximately 1.00 inch per second (Figure 3). 

NOTE

• Make sure all surfaces of probe are visually clean prior to inserting device into 

bore. 

• Check all screws, fasteners, and other components of probe prior to and after 

inspection. 

h. Scan toward front of spline until signals from spline end shoulder are visible and probe 

reaches forward stop ring. (Figure 4). 

i. Rotate tool clockwise approximately 1/16 (0.0625) inch. Scan spline area as tool is withdrawn 

to aft stop ring. 

j. Any positive signal appearing in output bevel gear spline area shall be evaluated as follows: 

k. Repeat this procedure until entire spline area has been scanned. 

l. Repeat scan, by rotating tool one full revolution, then index forward and repeat until full spline 

area has been scanned. 

m. Clean tail gear box shaft bore as follows: 

1 Using dry lint free wipes clean the tail gear box shaft bore prior to inspection. Refrain 

from using any solvents or cleaners that could possibly contaminate the tail gear box. 

NOTE

Count number of wipes used and make sure they are all removed upon completion. 

March 27, 2008 

Revision A – May 21/09 

Page 3 of 15
SPECIAL SERVICE INSTRUCTION NO. 70-121A 

2 Push wipes in from servo side out through rotor side of bore to avoid pushing dirt into 

tail gear box. 

n. Check calibration sensitivity with calibration ring after each output bevel gear shaft has been 

inspected. Recalibrate and reinspect if calibration is off by more than 5%. 

NOTE

Evaluate at Calibration Sensitivity (scan sensitivity minus 6 dB). 

1 In areas within two adjacent splines on either side of missing spline as shown in 

Figure 1, Zone 1, signals 25% FSH or greater at calibration sensitivity (not scan 

sensitivity) are cause for investigation/rejection. 

2 In tip of spline as shown in Figure 1, Zone 2, signals 35% FSH or greater at 

calibration sensitivity (not scan sensitivity) are cause for investigation/rejection. 

Verification of indications from tip of spline (Zone 2) can be conducted by damping 

using an oil soaked Q-tip. This does not require re-verification after subsequent 

assembly. 

3 In all remaining splines, signals 35% FSH or greater at calibration sensitivity (not 

scan sensitivity) are cause for investigation/rejection. 

4 Check calibration sensitivity with calibration ring after each output bevel gear shaft 

has been inspected. 

5 Screen view in Figure 5 is signal response from spline end with probe position 

towards front stop. Note the two typical low amplitude signals from spline end that 

follow main spline end signal. 

6 An indication from a spline crown anomaly will be further out in time than one from a 

spline root anomaly (Figure 6). 

7 An example of signals from a simulated crack (EDM notches) is shown in Figure 5. 

Remove retention plate if further investigation is necessary. 

NOTE

• Crack indications shall be recorded on the data sheet attached and reported to 

Sikorsky Aircraft Corporation. 

8 If a tail gear box is rejected for this inspection, tag rejected tail gear box with the 

following note: 

“THIS TAIL GEAR BOX HAS BEEN REJECTED AND BEING RETURNED FOR 

OUTPUT SHAFT SPLINE CRACK INDICATION DURING PHASE UT INSPECTION.”

March 27, 2008 

Revision A – May 21/09 

Page 4 of 15
SPECIAL SERVICE INSTRUCTION NO. 70-121A 

B. Record of Compliance: 

Make an appropriate logbook/log card entry to show compliance with this SSI. 

Weight and Balance Data:

None. 

Manpower (Estimated):

No. of Men No. of Hours Man-Hours

Mechanic 1 1.5 *1.5 

UT Technician 1 1.5 *1.5 

Total Man/Hours 4.0 

*Does not include time required to prepare helicopter for maintenance or return it to flight status. 

Parts Required:

Not Applicable 

Consumable Material: 

WARNING

OBSERVE ALL CAUTIONS AND WARNINGS ON CONTAINERS WHEN USING 

CONSUMABLES. WHEN APPLICABLE, WEAR ALL NECESSARY PROTECTIVE GEAR 

DURING HANDLING AND USE. IF A CONSUMABLE IS FLAMMABLE OR EXPLOSIVE, 

MAKE CERTAIN CONSUMABLE AND ITS VAPORS ARE KEPT AWAY FROM HEAT, SPARK, 

AND FLAME. MAKE CERTAIN EQUIPMENT IS PROPERLY GROUNDED AND 

FIREFIGHTING EQUIPMENT IS READILY AVAILABLE PRIOR TO USE. FOR ADDITIONAL 

INFORMATION ON TOXICITY, FLASHPOINT, AND FLAMMABILITY OF CHEMICALS, 

CONSULT YOUR MEDICAL PEOPLE, OR MANUFACTURER OF THE CONSUMABLE. 

Qty Nomenclature Part Number Source

A/R Oil, Tail Gear box DOD-PRF-85734 (or MIL-PRF-23699), or 

equivalent 

(1) 

A/R Lint-free Cleaning Cloth or 

Wipes 

MIL-C-85043 or equivalent (2) 

A/R Loctite 420 MIL-A-46050C Type II, Class I, or equivalent (3) 

March 27, 2008 

Revision A – May 21/09 

Page 5 of 15
SPECIAL SERVICE INSTRUCTION NO. 70-121A 

A. Tools Required: 

Qty Nomenclature Part Number Source

1 Calibration Ring EWR 203026 (1) 

1 Feeler Gage Standard Feeler Gage with 0.010 

inch gage 

(2) 

1 Ultrasonic 

Inspection Tool 

Olympus, HB 2344 or equivalent (as 

approved by Sikorsky Aircraft 

Corporation) 

(1) 

1 Ultrasonic 

Inspection Tech 

Sheet 

Reference Document: Tech Sheet 

5047 (latest revision) 

(1) 

 

Source: 

(1) Supplied by Sikorsky Aircraft Corporation. 

(2) Procure from local supply. 

(3) Ellsworth Adhesives, Web site: 

http://www.ellsworth.com/display/productdetail.html?productid=981 

March 27, 2008 

Revision A – May 21/09 

Page 6 of 15
SPECIAL SERVICE INSTRUCTION NO. 70-121A 

TAIL GEAR BOX DATA SHEET 

Table 1: Tail Gear box (TGB) 

P/N 70358-_____-___ 

S/N 

Time Since New (TSN) 

Time Since Overhaul (TSO) 

Table 2: Retention Plate 

P/N 70358-06612-____ 

S/N 

TSN 

TSO 

Table 3: Output Bevel Gear (only for helicopter models where P/N is recorded on TGB log card 

P/N 70358-06620-____ 

S/N 

TSN 

TSO 

March 27, 2008 

Revision A – May 21/09 

Page 7 of 15
SPECIAL SERVICE INSTRUCTION NO. 70-121A 

Table 4: Torque Check (torque sequence is 1, 9, 13, 5, 11, 3, 15, 7, 2, 10, 14, 6, 16, 8, 12, and 4) 

Note: 

Torque Check is only required if output shaft spline does not pass UT inspection. 

March 27, 2008 

Revision A – May 21/09 

Page 8 of 15
SPECIAL SERVICE INSTRUCTION NO. 70-121A 

Zone 1 

Zone 2: 

Applies to all splines 

including those in 

Zone 1. 

FIGURE 1: Inspection Zones 

March 27, 2008 

Revision A – May 21/09 

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SPECIAL SERVICE INSTRUCTION NO. 70-121A 

FIGURE 2: Signal Response of an EDM Notch 

March 27, 2008 

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SPECIAL SERVICE INSTRUCTION NO. 70-121A 

FIGURE 3: Spline Scan Area 

March 27, 2008 

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SPECIAL SERVICE INSTRUCTION NO. 70-121A 

FIGURE 4: Fully Insert Tool to Locate Large Plug in Rear Bore 

March 27, 2008 

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SPECIAL SERVICE INSTRUCTION NO. 70-121A 

FIGURE 5: Signal Response of Spline End 

March 27, 2008 

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SPECIAL SERVICE INSTRUCTION NO. 70-121A 

FIGURE 6: Signal Responses of Crown Notch and Root Notch 

March 27, 2008 

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SPECIAL SERVICE INSTRUCTION NO. 70-121A 

FIGURE 7: Scan Positioning and Length of Scan Stops 

March 27, 2008 

Revision A – May 21/09 

 15 of 15