bell 212

TECHNICAL BULLETIN No. 212-84-84

Bell Helicopter TEXTRON DATE 2-29-84DATE

REV. Post Office Box 482 For Worth Texas 76101 PAGE NO.

MODEL AFFECTED: 212

SUBJECT: FLIGHT CONTROL CYLINDER, P/N 212-076-005-7, -11, -101, PISTON HEAD SEALS,REPLACEMENT OF

HELICOPTERS AFFECTED: Model 212 helicopters, serial numbers30501 through 31216, 31218 through31231, 31234, 31235, and 31247.

[Helicopter serial numbers 31217, 31232,31233, 31236 through 31246, and 31248and subsequent will have the intent ofthis bulletin accomplished prior todelivery.]

COMPLIANCE: Part 1: At the next Preflight Check of theHydraulic System and each PreflightCheck thereafter until compliancewith Part II.

Part II: Recommend at the next overhaul orrepair of the flight control cylinder.

DESCRIPTION:

Reports from helicopter operators indicate early deteriorationof the piston head seals used in flight control cylinderassembly, P/N 212-076-005-7, -11, and -101. This condition mayresult in cylinder motoring, sluggish operation or erraticcontrol.

The attached HR Textron Service Bulletin,FMTC No. 260, providesinstructions for installing modification kit KC48088996UN.This kit replaces the existing piston head seals with a newseal, P/N S30772-124G20N, or P/N CEC6601-124-75. The kitinstallation will result in extended seal wear life andimproved service life of the flight control cylinder.

FAA APPROVAL:

The engineering design aspects reflected in the attached HRTextron Service Bulletin FMTC No. 260 are FAA approved.

AN APPROPRIATE ENTRY SHOULD MADE IN THE AIRCRAFT LOG BOOK UPON ACCOMPLISHMENTIF OWNERSHIP OF AIRCRAFT HAS CHANGED PLEASE FORWARD TO NEW OWNER

T.B. 212-84-84Page 2 of 3

MANPOWER:

Manhours are based on "hands-on" time. Elapsed time toaccomplish the required maintenance task may vary due tomanpower and facilities available.

Part I. No appreciable additional time is required toperform cylinder operational checks during theHydraulic Preflight Check.

Part II. Approximately five (5) manhours are required toaccomplish Part II of this bulletin. If seals arereplaced during flight control cylinder overhaul,no additional time is required for theirinstallation.

MATERIAL:

See attached HR Textron Service Bulletin.

SPECIAL TOOLS:

See attached HR Textron Service Bulletin.

WEIGHT AND BALANCE:

Not affected.

ELECTRICAL LOAD DATA:

Not affected.

REFERENCES:

Flight Control Cylinder Assembly Overhaul Manual, HR TextronPart Number 41000470 (BHT P/N 212-076-005).

HR Textron Service Bulletin FMTC No. 260.Model 212 Maintenance Manual.Model 212 Flight Manual (ALL).BHT Technical Bulletin No. 212-80-45.

PUBLICATIONS AFFECTED:

Flight Control Cylinder Assembly Overhaul Manual, HR TextronPart Number 41000470 (BHT P/N 212-076-005).

T.B. 212-84-84Page 3 of 3

ACCOMPLISHMENT INSTRUCTIONS:

Part I.

1. Perform the Preflight Check of the helicopter HydraulicSystem in accordance with the appropriate Model 212 FlightManual. While performing the check, attentiveness shouldbe given to the detection of any abnormal control motionsdue to improper flight control cylinder operation. Ifcylinder motoring, erratic control, or sluggish operationis detected, remove cylinder(s) from service and accomplishPart II.

Part II.

1. Remove cyclic and collective flight control cylinders fromthe helicopter in accordance with the Model 212 MaintenanceManual, Chapter 27.

2. Replace the piston head seals in the flight controlcylinder assemblies, P/N 212-076-005-101, and all otherprevious dash numbers that have been modified per TechnicalBulletin No. 212-80-45, in accordance with the attached HRTextron Service Bulletin FMTC No. 260.

3. Install cyclic and collective flight control cylinders inthe helicopter in accordance with the Model 212 MaintenanceManual, Chapter 27.

HR

SERVICE BULLETINREPLACEMENT OF PISTON HEAD SEALS CEC5071-124-55

ON FLIGHT CONTROL CYLINDER ASSEMBLY41000470-005, -009, -011, OR -013

FAA 4861 FMTC NO. 260

1. Planning Information

A. Effectivity

This Service Bulletin affects flight control cylinder assemblyBHT 212-076-005-101 (HRT 41000470-013), and all other previous dashnumbers that have been modified in accordance with Service Bulletin FMTCNo. 247.

B. Reason

Recent field reports indicate a deterioration and disintegration of thepiston head seal, causing motoring, erratic control, and/or sluggishoperation.

C. Description

HR Textron, has available upon request, a new replacement seal,S30772-124G20N or CEC6601-124-75. During each preflight check, if anymotoring, erratic control or sluggish operation is detected, the flightcontrol cylinder assembly should be removed from the helicopter andmodified in accordance with this Service Bulletin.

D. Approval

HR Textron Engineering:

E. Manpower

Approximately 1.5 manhours are required to modify one shipset.

F. Material

Modification Kit KC48088996UN for replacement of piston head seals may beobtained from HR Textron, 25200 W. Rye Canyon Road, Valencia, CA 91355,Attention: Product Support Department.

G. Tooling

Installation Tool T556-33 and Sizing Tool T557-14.

Oct 31/83 Page 1 of 6

25200 West Rye Canyon Road * Valencia, California 91355 * 805/259-4030 * TWX 910/336/1438 * TELEX 65/1492

HR


H. Weight and Balance

Not affected.

I. Electrical Load Data

Not affected.

J. References

Flight Control Cylinder Assembly Overhaul Manual 41000470(BHT 212-076-005).

K. Publications Affected

Flight Control Cylinder Assembly Overhaul Manual 41000470(BHT 212-076-005).

2. Accomplishment Instructions:

A. Remove lockwire securing four screws (1, figure 1).

B. Remove four screws (1) and end cap (2) from piston (3). Do not disturbcomponents on end cap (2).

C. Slide cylinder (5) towards upper servo head assembly (6) to expose pistonhead seal (4).

D. Remove and discard existing piston head seal. Using Seal InstallationTool T556-33, carefully install and properly seat and form new piston headseal (4), Part Number S30772-124G20N (or alternate CEC6601-124-75) intogroove on piston (3), prior to using sizing tool. Using SizingTool T557-14, size and form new piston head seal (4).

E. Slide cylinder (5) back over piston head seal (4), using care not to cutor deform piston head seal (4).

F. Install end cap (2) over piston (3) and onto cylinder (5).

G. Install and secure four screws (1). Torque screws to 50 inch-pounds.Safety wire four screws together per MS33540 using lockwire MS20995C32.

H. Remove lockwire securing four screws (7, figure 1).



I. Remove four screws (7) and slide end cap (8) from lower servo head. Donot remove end cap (8) from piston (9).

J. Remove piston (9) from lower servo head assembly (10).

K. Remove and discard existing piston head seal. Using Seal InstallationTool T556-33, carefully install and properly seat and form new piston headseal (4), Part Number S30772-124G20N (or alternate CEC6601-124-75) intogroove on piston (9), prior to using sizing tool. Using SizingTool T557-14, size and form new piston head seal (4).

L. Slide piston (9) back into lower servo head assembly (10), using care notto cut or deform piston head seal (4).

M. Slide end cap (8) into lower servo head assembly (10), and secure withfour screws (7). Torque screws to 50 inch-pounds. Safety wire fourscrews together per MS33540 using lockwire MS20995C32.

N. Identify modification plate (12) with applicable serial number and theletter G, and install around center of lower servo head assembly (10).Carefully form modification plate to contours of lower servo head assemblyand secure with RTV 3145.

O. Testing. Three Optional Testing Methods:

Option 1. Utilization of a test stand capable of supplying 2250 psi.This is the preferred option.

Option 2. External hydraulic supply connected to helicopter afterinstallation of actuators.

Option 3. Utilization of the helicopter hydraulic supply afterinstallation of actuators. This option should be used only asa last resort or emergency situation. A satisfactoryinstallation of the seal cannot be verified with this optionduring ground test.

P. Testing Procedure Options:

Option 1. Connect flight control cylinder assembly to test stand.

(a) Connect both systems pressure and return lines. Apply500 psi to pressure ports.

(b) Cycle actuator five full stroke cycles to ensure actuatorand system are free of air.


HR


(c) Block return line and apply 2250 psi proof pressure.Hold input lever in neutral, full extend, and fullretract positions for a minimum of 1 minute in eachposition.

Requirement - There shall be no evidence of externalleakage, permanent deformation or looseningof parts.

(d) Connect a drip spout to each return port and apply

1000 psi. Monitor leakage out each return port withinput lever at neutral, full extend, and full retract.

Requirement - Leakage shall not exceed 80 cc/min ineither position.

(e) Cycle actuator 50 times to monitor external leakage fromend caps.

Requirement - Leakage shall not exceed four drops fromeither seal.

(f) Verify seal leakage in the innerconnect housing (11) byextending piston (9) to full extend position and hangingactuator in vertical position with lower servo headassembly (10) down, for 15 minutes. Check for leakage atvent hole in end of piston (9).

Requirement - Leakage shall not exceed four drops fromthe vent hole.

(g) Apply 500 psig to PRESS ports and cycle unit severaltimes to purge all air, then close PRESS and RETURN portsso that all ports are blocked and unit is full of fluid.

Shift input lever to full extend, then full retract andnote amount of force required at the pilot input tomanually move actuator through full excursions (extend toretract, then retract to extend).

Requirement - With input lever shifted to full extend orfull retract, actuator shall be capable ofbeing manually moved through full excursionwith a force not exceeding 31 pounds.

(h) If actuator meets all of the above requirements, it is

considered acceptable.



Option 2. Install actuator on helicopter and connect hydraulic groundpower cart.

(a) Adjust external hydraulic supply to 1000 psi systempressure.

(b) Move cyclic and collective controls through fullstroke. Observe actuator for leakage and monitor formotoring, erratic control or sluggish operation.Reference hydraulic system check in BHT Flight Manual.

(c) Further verification of satisfactory assembly can bechecked by removing return lines and test per Step (d) inOption 1.

Requirement - If there is no motoring, erratic control orsluggish operation and/or the leakagerequirements are within limits, theactuator is considered acceptable.

Option 3. This option should only be performed in an emergency.

(a) Install actuator on helicopter.

(b) Move cyclic and collective controls through travel asdescribed in BHT Flight Manual, hydraulic system check.Check for motoring, erratic control and/or sluggishoperation.

Requirement - If any of the above conditions exist,remove actuators and repair as required.


HR


SCREw 1

END CAP 2

3 PISTON

*PISTON HEAD SEAL 4PART NUMBER

30772-124G20N(OR ALTERNATECEC6601-124-75) -5 CYLINDER- c

11 INTERCONNECT HOUSING6 UPPER SERVIC

HEAD ASSEMELY

LOWER SERVO 10HEAD ASSEMBLY

12 MODIFICATION PLATE

*PISTON HEAD SEAL 4-PART NUMBERS30772-124G20N 9 PISTON(OR ALTERNATECEC6601-124-75'

END CAP8

Figure 1. Piston Head Seal Installation Data


TB 212-84-84 - FLIGHT CONTROL CYLINDER, P/N 212-076- 005-7, -11, -101, PISTON HEAD SEALS, REPLACEMENT OFMODEL AFFECTEDHELICOPTERS AFFECTEDCOMPLIANCEPART 1PART II

DESCRIPTIONFAA APPROVALMANPOWERPART IPART II

MATERIALSPECIAL TOOLSWEIGHT AND BALANCEELECTRICAL LOAD DATAREFERENCESPUBLICATIONS AFFECTEDACCOMPLISHMENT INSTRUCTIONSPART IPART II

SERVICE BULLETIN1. PLANNING INFORMATIONA. EFFECTIVITYB. REASONC. DESCRIPTIOND. APPROVALE. MANPOWERF. MATERIALG. TOOLINGH. WEIGHT AND BALANCEI. ELECTRICAL LOAD DATAJ. REFERENCESK. PUBLICATIONS AFFECTED

2. ACCOMPLISHMENT INSTRUCTIONSFIGURE 1 - PISTON HEAD SEAL INSTALLATION DATA

bell 212

Documents