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Trimming your Jab to fly straight

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Trimming your Jab to fly straight

Postby diablo » Tue Mar 22, 2016 7:56 am

This is likely to be useful to most of us when trimming the Jabiru airframe to fly straight. It is pretty universal so can be applied to any airframe. The starting point is to get the aircraft flying level so that it does not want to bank in either direction. To do that, The prerequisites are:

Pre-Requisites
1. Ideal conditions are light winds wind no gusts. When testing, aircraft must be flown into wind (nil wind conditions are best for testing)
2. Weight on P1 and P2 seats should be equal (or approximately)
3. On jabiru airframe, trimming is adjusted by increasing or reducing the amount of flap by screwing in or out the flap rod end. Some basic mechanical knowledge and tools are required to do this.

Should you decide to make changes to the aircraft, you will be doing so at your own risk and you should get the aircraft inspected by an LAA inspector before undertaking a flight


Procedure
Settle the aircraft at cruise speed (91 kts) and trim for straight and level flight. Let go of controls and note which way aircraft banks. The procedure for adjusting the tendency to bank in either direction is as follows:

1. Release rod end locknut on P1 flap.
2. Turn rod end (half, one or two turns) clockwise or anticlockwise to raise (if aircraft banks to starboard) or lower (if aircraft banks to port) port flap.
3. Test aircraft as above
4. Continue adjustment until aircraft flies level and tendency to bank is corrected.

Now for the final part which involves correcting or fine tuning balance. Ideally your aircraft will have a trim tab on the rudder. If you do not have one, get one made up or ask the forum for a rudder trim tab kit. They are cheap and easy to install. The final phase is done by adjusting rudder trim.

1. Settle the aircraft at cruise speed (91 kts) and trim for straight and level flight.
2. Check balance ball on balance indicator
3. Adjust rudder trim to correct balance

Job done ...
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Re: Trimming your Jab to fly straight

Postby Garyo » Tue Mar 22, 2016 10:46 am

assume this is done at MTOW or would you do it at your normal weight you fly every day at
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Re: Trimming your Jab to fly straight

Postby diablo » Tue Mar 22, 2016 11:02 am

Best way to do it is to set the aircraft up as you would normally fly (i.e: one up, two up). I do not think total weight really matters, it is the position of the load that is more important. I normally fly solo, therefore I would set my aircraft up to fly straight without a passenger.

Bear in mind that once it is set up to fly straight in that configuration, for example one up, it will not fly straight when you have a passenger on board and vice versa.
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Re: Trimming your Jab to fly straight

Postby Russ » Thu Mar 24, 2016 6:17 am

I would LOVE to be able to reduce the side load off my control stick,when battling a strong xwind hr after hr.
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Re: Trimming your Jab to fly straight

Postby diablo » Thu Mar 24, 2016 8:42 am

Hello Russ,

there is a way to do that.

Run a bungee across the top of your cockpit and another from the stretched bungee to your joystick (in a T with top part of T running along top of cockpit). Hook bottom of T onto the joystick and move along to give desired side load. you still retain full control of flight surfaces but in a neutral position (no force on joystick by you) the bungee will pull joystick towards tension. Looks a bit messy but works. Motorcycle elastic bungees work well!

;)
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