Tyre Inflation

This document and the information herein are proprietary to Messier-Bugatti-Dowty, They must not be copied or communicated to a third party without the prior written authorization of

Messier-Bugatti-Dowty.

Maintenance Practices

In-Service Experience: Tire inflation

& deflation N

1/ March, 2012

SAFRAN and MESSIER-BUGATTI names are marks owned respectively by SAFRAN and Messier-Bugatti-Dowty companies.

The mark DOWTY is used under license.

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IN-SERVICE EXPERIENCE – WARNING

In-Service Experience / Tire inflation & deflation / N

1, March 2012

This “In Service Experience” is Messier-Bugatti-Dowty proprietary.

Its use is strictly limited to Messier-Bugatti-Dowty customers operating

and/or repairing the relevant products.

It shall never be copied nor transmitted to any other organization without

Messier-Bugatti-Dowty authorization.

The information given in the “In-Service Experience” is not contractual.

In no case shall it supersede the applicable Messier-Bugatti-Dowty

Technical Publication (eg : Component Maintenance Manual, Service

Bulletin, Service Letter, Product Deviation Authorization etc…) for

operation and/or maintenance purposes.

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INTRODUCTION LETTER

We are pleased to introduce our 1st issue of „In-Service Experience‟

dedicated to « tire inflation & deflation »

In order to share yours and our common expertise and experience, all

comments about this document are welcome

Refer to last page for details

We aim to target several updates per year to introduce new subjects and

include the workshop‟s comments


1, March 2012

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MESSIER-BUGATTI-DOWTY MAINTENANCE

OBJECTIVES

Adopt our recommendations to your operations whenever possible

Anticipate and comply with environmental and health constraints

Continuously improve the in service performance of our equipment

To reduce the maintenance cost for Airlines


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AGENDA

Aim of the ISE

Valve & Plug description

Inflation valve

Description

Disassembly

Assembly

Thermal fuse plug

Description

Disassembly

Assembly

Overinflation valve

Description

Disassembly

Assembly


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Tire deflation

Procedure

Tools

Inflation

Trouble shooting

Toolings

Consumables

Bibliography

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AIM OF THIS IN-SERVICE EXPERIENCE

To give information on wheels inflation systems especially on:

Inflation devices

Tire inflation/deflation

Consumables

Trouble shooting

Equipment and tooling

Service Letter F6137-32-795 (only for Messier-Bugatti-Dowty product ) :

Clarify the bases and objectives of the CMM jobs

Remind the general Messier-Bugatti-Dowty maintenance policy intended to all

operators

Define the field of applicability for limitation to certain CMM jobs

Target : save time and reduce maintenance cost


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VALVES AND PLUGS DESCRIPTION

Parts to be checked in case of pressure loss


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Overinflation valve

or plug

Inflation valve

TPIS or

plug

Fuse plug

O-ring seal

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VALVES AND PLUGS DESCRIPTION

Depending on the program, plugs & valve may be secured by lockwire or

Loctite®


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Secured by Loctite® Secured by Lockwire

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INFLATION VALVE

DESCRIPTION A valve assembly in the inner half-wheel assembly permits to inflate the tire

Standard inflation valve (high/low flow)


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Core

Low flow

Protective cap

Short bore

Long bore

High flow

Protective cap

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INFLATION VALVE

DESCRIPTION

Example of inflation valve with pressure gauges used at MBD


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INFLATION VALVE

DESCRIPTION Valve core description


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INFLATION VALVE

DISASSEMBLY Loosen and remove the valve core with the correct tool

Loosen and remove the valve stem

Remove the preformed packing from the valve stem with the correct tool


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Warning : Removal of the valve core on an inflated tire/wheel

assembly could project the core with dangerous speed and force

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INFLATION VALVE

ASSEMBLY WITH TORQUEMETER Torque wrench, dial type : accurate and compact for torquing the core

valve to the values given in CMM


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Valve body Adaptor Core Torquemeter

Torquemeter

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THERMAL FUSE PLUG

DESCRIPTION Thermal fuse melt in case of overheat to prevent wheel damage, tire burst

Eutectic alloy is a mixture of two or more components which melt in a

given temperature, as per CMM


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Thermal fuse screw Threadless fuse plug

Eutectic

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THERMAL FUSE PLUG

DISASSEMBLY Thermal fuse screw

Push and remove the fuse plug assemblies

Remove the preformed packing from the fuse plug assemblies with

the correct tool

Thermal fuse plug

Install a threaded rod in each fuse plug assembly

Pull and remove the fuse plug assemblies from the inner half-wheel

assembly

Loosen and remove the threaded rods from the fuse plug assemblies

Remove the preformed packing from the fuse plug assemblies


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Warning : Discard all the fuse plug assemblies from a main

landing gear assembly which was overheated

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THERMAL FUSE PLUG

ASSEMBLY

Example on 737 program: fuse plug


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Install lubricated preformed packing on the fuse plugs.

Install the fuse plugs in the hole by hand

Threaded hole to ease removal

Get access to fuse from outside of wheel barrel

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THERMAL FUSE PLUG

ASSEMBLY: USE OF LOCTITE® Some plugs are secured with Loctite® in order to avoid plug loss

Valve: A320 program

Thermal fuse plug: A321 & 767 programs

Recommendation

During plug/valve installation it is recommended to apply specified Loctite® thread-lock

compound as per relevant CMM

Clean plug/valve and wheel port threads, with Loctite® 7063 or 790 (or equivalent), to remove

contaminants

Apply Loctite® 7649 primer N on plug/valve (optional) and a layer of Loctite® 242 or 274 on the thread

and under the head

Install and torque the thermal relief plug as per relevant CMM


1, March 2012

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THERMAL FUSE PLUG

ASSEMBLY: USE OF LOCTITE® Apply a paint or a torque seal mark on the valve/plug to allow a quick

visual check of loosen devices


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Warning : Do not tighten again Loctite® devices otherwise you

break the Loctite® “layer”

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OVERINFLATION VALVE

DESCRIPTION An overinflation valve releases the tire pressure

In case of overpressure the membrane will be burst


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Antidust seal

Pressure

membrane

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OVERINFLATION VALVE

DISASSEMBLY

Loosen and remove the overinflation valve from the main landing gear

wheel assembly.

Remove the preformed packing from the overinflation valve with the

correct tool


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Caution : Disassemble the main landing gear wheel assembly in a

room free from dust and moisture on a clean, flat and soft surface.

A smooth rubber surface is recommended.

Warning : Removal of the overinflation valve assembly should be

carried out on a fully deflated tire.

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OVERINFLATION VALVE

ASSEMBLY

Apply a thin layer of silicone grease to the preformed packing

Install the preformed packing on the pressure relief valve with the correct tool

Apply a thin layer of adhesive compound to the threads of the pressure relief

valve

Install the pressure relief valve in the inner half-wheel assembly on the outer

half-wheel assembly side.

Torque the pressure relief valve to the correct value as per CMM


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Caution : Apply only specified lubricant product to the preformed

packing. An incorrect lubricant product can cause damage to the

preformed packing

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TIRE DEFLATION

PROCEDURE

Loosen and remove the cap from the valve assembly

Use a deflation tool to deflate the tire

Fully deflate the tire before its removal from the wheel

If damage has occurred, a tire/wheel assembly should be deflated in a

protective cage


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Warning : Removal of the valve core on an inflated tire/wheel

assembly could project the core with dangerous speed and force

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TIRE DEFLATION

TOOLS Deflate the tire with a deflation tool


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Example of deflation tools

Details of the tooling

1 2 3

Myers : www.myerstiresupply.com

ATI Tools : http://www.atitools.com

Catana Aero : http://www.catana.aero

Warning : These equipments were not tested by

Messier-Bugatti-Dowty

Brand names are only provided for information not for

any product endorsements

http://www.myerstiresupply.com/

http://www.atitools.com/



http://www.catana.aero/

http://www.catana.aero/

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TIRE DEFLATION

TOOLS Tire deflation is noisy

See devices to reduce noise

The air is released outside, which reduce the noise during tire deflation


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Zeca : www.zeca.it/en/index.php

Warning : These equipments were not tested by Messier-Bugatti-Dowty

Brand names are only provided for information not for any product endorsements

http://www.zeca.it/en/index.php

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INFLATION

Inflate the tire in an inflation cage.

WARNING: Overinflation can cause an explosion / tire burst

Use a regulated pressure source to inflate the tire.

WARNING: An unregulated pressure source can cause injuries to the personnel and

damage to the wheel and tire

2 layers of regulation is recommended: primary and a back-up

Inflate the tire with dry nitrogen for storage and on-aircraft use

Oxygen concentration must not exceed 5%. A chemical reaction between oxygen

and volatile gases from the tire is possible leading to a tire explosion


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INFLATION

PRESSURE RETENTION PROCEDURE Check pressure retention as per Tire manufacturer‟s procedure for

wheel release to service


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Period Criteria of

pressure loss

Procedure

24 hours 5 % Normal

12 hours 2,5 % Alternate

Michelin inflation procedure

Bridgestone recommended inflation procedure

Air retention criteria

Courtesy of Michelin

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INFLATION IN-SERVICE TIRE PRESSURE CHECK

For instruction on removing unserviceable tires, refer to relevant AMM

Maintaining proper tire inflation is one of the key element to ensuring

satisfactory tire service life

Tire manufacturers recommend that tire pressures be checked every 24

hours whenever possible because with a maximum daily pressure loss

of 5%, longer intervals will

increase the likelihood

of operating at underinflated.

Tire pressure follow-up is

key to determine if the tire is

serviceable


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TROUBLE SHOOTING

LOW PRESSURE

If pressure drops more than 5% in the 24 hours

Possible root causes:

Environment

‒ Decrease of the ambient temperature after inflation

‒ Area (Airport altitude)

Wheel & Tire

‒ Crack on a half wheel

‒ Tread cuts / Foreign Object Damage (FOD)

‒ Leakage on O-ring groove of the wheel

‒ Leakage between bead & wheel rim

‒ Leakage

‒ on inflation valve

‒ on thermal fuse plug

‒ on sidewall vent holes (green mark)

‒ on TPIS/plug

‒ on inner liner of the tire

Improperly torqued or defective valve


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Courtesy of Michelin

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TROUBLE SHOOTING

LOW PRESSURE


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Check with water or soap solution

If no leaks are found, rerun 24 hour diffusion check

If pressure still drops more than 5%, disassemble tire/wheel

assembly

Check wheel O-ring seal for condition,

‒ proper size/type and lubricant

Check wheel for cracks, porosity, fuse plug or pressure release

plug malfunction

Alternate not recommended: Dip the wheel

Some operators submerge the wheel (without bearing) and

slowly rotate the wheel and check for air bubbles

Reapply operating pressure and wait for tire stretch

Warning : Water in wheel bearings is bad

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TROUBLE SHOOTING

THERMAL FUSE PLUG Superficial holes, core extrusion or cracks are due to normal manufacturing

process (possible fusible material retraction during the cooling).


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A

Holes or Cracks

Extrusion

Variable geometry are authorized within the area indicated “A”.

A leakage test could be performed as trouble shooting in

case of leak not yet located with water soap solution.

Fuse plugs with cracks or core extrusion are acceptable if they

succeed to the leakage test

Melted plug

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TROUBLE SHOOTING

LOOSEN PLUG

Depending on the program, valve/plug have to be fitted with Loctite®

Apply a paint or a torque seal mark on the valve/plug to allow a quick

visual check of loosen devices


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Warning : Do not tighten again Loctite® devices otherwise you

break the Loctite® “layer”

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TROUBLE SHOOTING

THREAD CRUSH Background

A/L have a few experience of thread crush caused by the corrosion between

different metal

Preventive recommendation

Dry properly the wheels after cleaning

A good greasing of the packing should ensure the sealing


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TROUBLE SHOOTING

USE OF LOCTITE® 7063 Background

The use of Loctite® 7063 can damage the paint surrounding the bore of the wheel

Preventive recommendation

The area surrounding the bore needs to be masked or any Loctite® 7063 residuals

needs to be wiped off immediately after application

Dry properly the wheels after cleaning

A good greasing of the packing should ensure the sealing


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Silencer (optional)

Inflation cage (Kunz/Bauer)

TOOLING

EXAMPLE Valve core removal

Core torque

Fuse plug test if any or

trouble shooting (CMM)


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CONSUMABLES


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Loctite

Isopropyl Alcohol

(for cleaning) Petroleum

jelly

Lockwire

Petroleum jelly

Loctite

Isopropyl Alcohol

(for cleaning)

Silicone grease

or

Petroleum jelly

Loctite

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BIBLIOGRAPHY

Tire manufacturer

Michelin: www.michelin.com/aviation

Bridgestone: www.bridgestone.com/products/speciality_tires/aircraft/index.html

Goodyear: www.goodyearaviation.com

Dunlop: www.dunlopaircrafttyres.com

Aircraft manufacturer

Airbus:

SIL32-119 – Suggested maintenance procedures for wheel and tire assembly

Boeing:

SL32-138 – Suggested maintenance procedures for wheel and tire assembly

Extract from Boeing Aeromagazine – Issue 29 – Qtr 1_2008

‒ Wheel/Tire pressurization: simple precautions can save lives (By Chris Dubuque)

(http://www.boeing.com/commercial/aeromagazine/articles/qtr_1_08/AERO_Q108.pdf)

MBD: Techpub

ISE

CMM


1, March 2012

http://www.michelin.com/aviation

http://www.bridgestone.com/products/speciality_tires/aircraft/index.html

http://www.goodyearaviation.com/

http://www.dunlopaircrafttyres.com/

Tyre Inflation

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