J430 trimming

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Shaunus
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J430 trimming

Unread post by Shaunus » Thu May 16, 2019 11:09 am

Morning good Jab Family!

I friend has just bought a J430 and was inquiring about how the plane climbs when you take your hands off the controls, and that you still need down pressure even when trimmed all the way forward. Mine is the same, though it never really bothered me as the autopilot is able to hold the pressure for longer flights.

Below is the difference between full forward, and full back. Seem right?

Cheers
Shaun

WhatsApp Image 2019-05-15 at 9.27.29 PM(1).jpeg
WhatsApp Image 2019-05-15 at 9.27.29 PM.jpeg
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Re: J430 trimming

Unread post by Burner » Thu May 16, 2019 12:59 pm

It's been ages since I last flew a Jab4. But I do remember that with a very aft C of G, the ones I flew did require a constant forward pressure on the stick. It has fixed trim tabs, so moving the trim basically just moves the sticks neutral point.

With two up, then he should be able to trim it hands off in all phases of flight. With a load in the back, he may have to apply forward pressure on the stick slightly.

The generous legroom in the back, doesn't come for free!
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Re: J430 trimming

Unread post by Flooi » Fri May 17, 2019 1:47 pm

Strange. I've never experienced that before. All my Jabbies flew hands off if trimmed. I have never flown a J430 with pax in back seat though.....
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Re: J430 trimming

Unread post by JimmyZ » Fri May 17, 2019 2:17 pm

Not sure about the J430. However if it helps, on the J170 (and if I remember correctly the J120 and SP470 too) the full forward and full back positions on the elevator looks exactly the same as your attached photos. Elevator moves way up but hardly moves down past level. It's strange at first, but after a while it is accepted as normal.

I've been a pax in the backseat of a J430 a couple of years ago, and I remember the PIC briefing about caution with rotation on takeoff run because of myself in the backseat bringing the CG back, but can't recall what the situation with trim was on that occasion.
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Re: J430 trimming

Unread post by mikestark » Fri May 17, 2019 5:42 pm

When I had my 450 I would always fly with almost full down trim except on the landing phase.
Took a big step and cut the trim tabs off altogether. Was the best move I made. Normal cruise was in the Centre and I added 5kts to the cruise. (The trim tab and the elevator fighting one another added drag)
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Re: J430 trimming

Unread post by Flooi » Fri May 17, 2019 6:38 pm

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Re: J430 trimming

Unread post by Shaunus » Mon May 20, 2019 9:43 pm

Thanks for the replies so far. With just me up, in the cruise with trim full forward, I still need to maintain positive downward pressure on the stick. The autopilot will also sometimes slip in the descend, probably due to the overriding forces. Even having a 70kg co-pilot (me being 85) requires a small position pressure.

Thus what are my options besides trimming the trim tab and/or flying with a 200kg pax as copilot?

Anyone else have success with a shave off the trim tab?

Cheers
Shaun
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Re: J430 trimming

Unread post by CJW » Tue May 21, 2019 8:58 am

Shaunus wrote:
Mon May 20, 2019 9:43 pm
Thanks for the replies so far. With just me up, in the cruise with trim full forward, I still need to maintain positive downward pressure on the stick. The autopilot will also sometimes slip in the descend, probably due to the overriding forces. Even having a 70kg co-pilot (me being 85) requires a small position pressure.

Thus what are my options besides trimming the trim tab and/or flying with a 200kg pax as copilot?

Anyone else have success with a shave off the trim tab?

Cheers
Shaun
If I remember correctly, there was a post quite some years ago about how to adjust the trim. The adjustment assembly is underneath the cover under the tail. If my memory serves me correct there is a number of pre-drilled holes in the adjustment assembly which moves trim forces by way of springs forward and backward. Back then one of the gurus on here suggested that one open up the cover and carfully study the mechanism before fiddling.

On my 430 I also sometimes run out of forward/down trim in the cruise, even with 190kg in the front seats alone. I believe it is not only the weight on the different seats that influence trim, but also the AoA which is speed and weight dependant. In the cruise with two up (190kg) I find that reducing speed just a little bit will stop the autopilot from telling me to "trim down". With my family (4 people, 225kg in total, with a split of 165kg in front and 60kg in the rear) she seems very happy in the cruise at 105 - 113 TAS.
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