Power Pak Pressure Switch Upgrade

   Airight, Inc. is offering a new pressure switch for use on their Power Paks. 

The switch PN 91450-1 is more reliable than previous switches, so be sure to specify this PN

when ordering. See drawing below for switch location on Power Pak.




NLG Rigging And Inspection

    The Nose Landing Gear Retraction System parts are showing signs of wear on SX's with 300 or more

hours in service. Refer to the drawing below for specific inspection items. Rigging of the Actuator, Bell crank 

and Link Assembly must be maintained to insure good over center force on the Drag Brace. Any wear in the 

Bell crank Assembly or attaching parts will compromise the ability of the Actuator to apply the force needed 

to keep the Drag Brace over center. Also, I've noticed a variety of springs being used on the Bell crank. 

Most are too weak to do the job. Remember, if you lose hydraulic pressure and have to rely on the gas spring 

to extend the gear, the Actuator is not applying  force on the Bell crank to hold the Drag Brace over center. 

Only the spring is going to hold the Drag Brace over center, so the spring should be strong enough to do the 

job. If the Drag Brace is allowed to move away from the over center position, the Down Lock Hook will not 

prevent the Nose Gear from collapsing.  




Engine Air Box Sides Modification

        Inspection of SX300 engine Air Box sides on aircraft with 200 or more hours has revealed

 cracking and elongated attach screw holes. I presume that the cracks are due to different expansion

 rates of each cylinder. If each side panel is cut, thus isolating each panel to its respective cylinder, 

the cracking can be minimized. Reinforcing the attach screw holes with steel washers riveted to the

panel prevents the screw head from chafing into the side panel. See drawing below.







SX 300 Hydraulic System Schematic    See Below




                           SX300 Home    Doug's Page

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