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SX300 BULLETIN

May 2, 2006

Revised March 17, 2009

 

This bulletin is to advise all Sweringen SX300 owners of the potential for Main Landing Gear Trunion failure.To prevent possible structural damage and bodily harm, The SX300 Group and its Technical Adviser is recommending that all owners, particularly those with flying airplanes, replace the original Airight Main Landing Gear Trunions p/n 67001-1 &-2 with a new modified part as soon as possible.We currently have a supplier, “Forming & Machining, Inc.” for the new modified parts. You can place your order, either by calling, Doug Poli  817-988-0859 or Bill Johns 913 294-5348.

Note: These new parts are built to specs. per alterations made to the original drawings and a digitized computer model produced from a modified original trunion.The new prototype was sent to Doug and place in a fixture to insure accuracy. This process was done several times before the final OK was given to produce parts. The result is a quality part.

You can respond by telephone, to Doug Poli at  817 626-3371 or email:  This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Trunion Failures

The trunion failures that occurred have been on airplanes with more than

500 hours logged. On John Fonville's trunion failure, it is reported that the aircraft has never had

anything but normal use, no hard landings or abuse. The airplane does have dual

calipers on the brakes and he recalls swerving quickly and applying

brake to even strut extension.

 

Below are photo comparisons of the new trunions versus the original trunions.

Please click on any thumbnail for larger view and to read the notes on them,

then use your browser's Back button to return to this page.

doug.jpg (44048 bytes) doug33.jpg (33774 bytes) doug77.jpg (45033 bytes)

doug100.jpg (42593 bytes) doug8.jpg (55552 bytes) doug6.jpg (54451 bytes)

 

 

Overview Of The Nitrogen Operated Emergency Gear Extension System

This is an experimental system. The system is designed to replace the main gear gas springs with modified new gas springs to operate as an actuator cylinder. The system is just for the main gear; the nose gear operates fine on the original gas spring and does not require replacement by this kit. The nose gas spring should be inspected frequently & replaced every year to ensure optimum operation. The main gear cylinders are made from new gas springs which have been modified by taking out the cross over piston and replacing it with a piston using a urethane cup seal. The cylinder has been ported for a 1/8" pipe fitting on the base of the cylinder for the nitrogen entrance and ported for exhaust on the rod end of the cylinder with a screen and filter. Each activating cylinder is 4.4 cubic inches in volume, plus hoses and the volume of the lines to the actuators from the storage battle. The total volume of the operating system is 10 cubic inches. The normal system pressure should be 1,700 to 2,000 psi at 1700 psi the system will put the gear down three times, losing about 280 psi per cycle. The schematic drawing of the system below shows the basic layout of all of the components.

Cautions

This Nitrogen Operated Emergency Gear Extension System has been developed to increase the reliability and safety of the landing gear. Bear in mind that you are removing one safety system and replacing it with another. The components and material that make up the system are of the highest quality but the quality of these materials and components can easily be compromised by a poor installation. Particular attention should be paid to preventing contamination of any kind including moisture, metal shavings, etc. from entering the system in the future. Metal shavings can damage the valve and particularly the piston. Moisture can cause internal corrosion of the actuator and can also freeze, especially in the tiny 1/8" tubing. Service the system with dry nitrogen "only". And last, but certainly not least, all component placement and mounting, line routing and the system in general should not interfere with any flight critical system (control cables, push pull tubes, wiring etc.).

 

 

 

HYDRAULIC ACTUATOR & SHOCK STRUT SEALS

 

MLG Strut -  Airight PN 67000-3, -4

COMPONENT

QTY

PART NO.

DESCRIPTION

Piston Tube

1

7222FS-160-T

GT Ring

Piston Tube

1

19-5S11065

Scraper

Seal Pack / Strut

1

MS28775-226

O Ring

Seal Pack / Strut

1

MS28774-226

Back-Up Ring

Metering Tube

1

MS28775-137

O-Ring

Service Valve Adapter

1

MS28778-5

O-Ring

Service Valve Body

1

AN901-5C

Washer

NLG Strut - Airight PN 66000-1

COMPONENT

QTY

PART NO.

DESCRIPTION

Piston Tube

1

7221FS-160-T

GT Ring

Piston Tube

1

DW1450-16-1

Scraper

Seal Pack / Strut

1

7223MT-160-T

GT Ring

Piston Tube, Upper

1

MS28775-127

O Ring

Strut / Trunion

1

MS28775-137

O Ring

Metering Tube

1

MS28775-131

O Ring

Upper Strut / Trunion

1

MS28775-232

O Ring

Service Valve Body

1

AN901-5C

Washer

NLG Strut - Airight PN 66000-2

COMPONENT

QTY

PART NO.

DESCRIPTION

* Piston Tube 1 MS28775-221 O Ring
* Piston tube 1 MS774-221 Back-Up Ring
* (Alt) Piston Tube 1 7221FS-160-T GT Ring
Seal Pack / Strut 1 7223MT-160-T GT Ring
Piston Tube, Upper 1 MS28775-127 O Ring
Strut / Trunion 1 MS28775-137 O Ring
Metering Tube 1 MS28775-131 O Ring
Upper Strut / Trunion 1 MS28775-232 O Ring
Service Valve Body 1 AN901-5C Washer

MLG Actuator - Airight PN 73050-5, -6

COMPONENT

QTY

PART NO.

DESCRIPTION

Piston Rod

1

MS28775-115

O Ring

Piston Rod

1

MS28774-115

Back-Up Ring

Cylinder End Cap

1

MS28775-126

O Ring

Cylinder End Cap

1

MS28774-126

Back-Up Ring

Piston

1

MS28775-219

O Ring

Piston

2

MS28774-219 Back-Up Ring

NLG Actuator - Airight PN 26230-1

COMPONENT

QTY

PART NO.

DESCRIPTION

Piston Rod

1

DW-1450-3-1

Scraper

Piston Rod

1

MS28775-114

O Ring

Piston Rod

1

MS28774-114

Back-Up Ring

Cylinder End Cap

1

MS28775-123

O Ring

Cylinder End Cap

1

MS28774-123

Back-Up Ring

Piston

1

MS28775-212

O Ring

Piston

2

MS28774-212

Back-Up Ring

Down Lock Hook Actuator - Airight PN 75025-1

COMPONENT

QTY

PART NO.

DESCRIPTION

Piston

1

MS28775-014

O Ring

Door and Flap Actuators - Airight PN 73150-1, -5

COMPONENT

QTY

PART NO.

DESCRIPTION

Piston Rod

1

MS28775-011

O Ring

Cylinder End Cap

1

MS28775-111

O Ring

Piston

1

MS28775-204

O Ring

Piston

1

MS28774-204

Back-Up Ring

Hand Pump - Airight PN 20700-8

COMPONENT

QTY

PART NO.

DESCRIPTION

Piston Rod

1

MS28775-114

O Ring

Piston

1

MS28775-115

O Ring

Cylinder End Cap

1

MS28775-117

O Ring

 

SX300 PARTS FOR SALE

P.M. Research Cowl Protective masks . . . . . . . . . . . . . .   $   400.00

NLG Seal Kits . . . . . . . . . . . . . . . .  . . . . . . . . . . . . . . . . . $     60.00

Large Capacity Hydraulic Powerpack "Burp" Cans . . .  .. $    100.00

Bubble Canopy Kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .$ 4850.00

Century Autopilot Installation Kits . . . . . . . . . . . . . . . . . .. $   800.00

S-Tec Yaw Damper Installation Kits . . . . . . .  . . . . . . . . ..$   350.00

Oil Filter Drain Kits (each)...............................................$     125.00

See drawing below.

 

 

 

NLG Wheel Axle Plug Recess

The RH nose landing gear wheel axle plug as it comes from Airight, Inc., sits on the outside of the fork creating a close fit between the plug and the NLG drag brace weldment (PN 29-12201-1) when wheel is retracted.

A good idea to prevent the plug from catching on the weldment is to recess the plug flush with the fork surface. Some are closer than others, so look closely at your SX at the next inspection.

 

Red arrow shows NLG Almost Retracted in Wheel Well. Note Flush Axle Plug.

 
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