J430 trimming

[Shaunus]

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

[Burner]

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!

[Flooi]

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.....

[JimmyZ]

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.

[mikestark]

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)

[Flooi]

viewtopic.php?t=109258

[Shaunus]

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

[CJW]

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.

[Shaunus]

So after adjusting the trim settings as much as possible, and still requiring a gym session before flying, I got gat-vol yesterday and began the process to adjust the fix trim tabs slightly. I began with a 5mm shave on each side, then flying in in a empty fuel and full fuel configuration, I then kept trimming 2mm off at a time and re-testing. Of the initial 25mm tab, I settled on trimming around 12mm i.e. half of the tabs.

The Outcome?

Wish I had done this 5 years ago. Forces are now perfectly neutralized, have picked up around 4-5kts in the cruise, and the autopilot now actually works in the climb and decent. Everything just feels more stable, it was like the elevator was always fighting itself. Maybe my fixed trim tabs were too long to start with?

Super happy all in all!

[V5 - LEO]

....that is great to hear Shaunus and this is exactly the purpose of NTCA aircraft

[mikestark]

My experience with the 450 was no trim tab = massive improvement.
Glad you took action.

[lessersg]

We did something similar on our J400. removed the trim tabs and trim mechanism and installed electric trim tab. Big difference. its somewhere on avcom the whole installation. And balanced the elevator, so if you disconnect the linkage elevator lies level.

[Tasmag]

Shaunus

I have not long finished the build of my 430, at some stage the angle of incidence was changed on the Horizontal Stabiliser for new builds, and I notice yours looks to be the old angle (3 degrees I think it was).

That would explain the problem, I think.

I don't that have that issue with mine at all.

Mike

[Shaunus]

Shaunus

I have not long finished the build of my 430, at some stage the angle of incidence was changed on the Horizontal Stabiliser for new builds, and I notice yours looks to be the old angle (3 degrees I think it was).

That would explain the problem, I think.

I don't that have that issue with mine at all.

Mike

Hi there Mike

There is actually a pic of a friends plane, so will tell him. But probably the same on my plane too, I haven't yet managed to measure any of the angles on mine - a 2013. Hows your J430 flying, what are your stats looking like?!

Cheers
Shaun

[Tasmag]

Shaun

I haven't really nailed then down yet, fitted mgl all through and have had some issues.

The issues related to the readings not being correct , as the actual temps are all pretty good. Not the fault of MGL though.

I think I am just about sorted, except for oil temp which may need a standard sender fitted, the one that came with the engine was for Dynon and appears to be reading 20 degrees low on the iefis.

It's a Gen 4, CHT in cruise around 110 to 120.

Usually around 120 KTAS at 2850 to 2900 above 5000.

Very impressed with the engine, doesn't use a lot of oil, pretty quick to spit out whatever you put in over about the halfway mark.

Starts on the first turn every time, hot or cold, without a cold start kit.

Just fitted a Steve rance TOCA, which has changed the oil pressure. Was a lot more stable with the standard adapter, which I may go back to yet.


Mike