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GRT baro and altitude setting

Tankerpilot75

Well Known Member
My GRT EX EFIS system seems to resist the quick setting of the altimeter and intended climb altitude before takeoff. Here’s what is happening:

1. Barometer setting: I attempt to set the airport altimeter heard over AWAS after engine start but when I go to enter the setting (say 30.15) the right knob will turn quickly but the change in the window is not immediate. In fact I have to stop turning the knob and wait for window readout to catch up and then continue trying to set the barometer in the EFIS.

2. Climb Altitude setting: Again, on the ground, I try to setup my initial climb out altitude using the right knob and instead of changing the big numbers first (hundreds of feet) it goes immediately to tens of feet. When I turn it quickly it just delays the setting of my intended climb out altitude because you have to wait for the (tens of feet) to catch up.

I don’t remember this occurring when I initially installed the EFIS units last summer but it’s occurring now for some unknown reason. Thankfully it doesn’t seem to be an inflight issue.

Has anyone else experienced this problem and if so how did you correct it. I haven’t seen any setting in either General or PDF page setup settings that can impact this issue.

Bob Turner, if you see this, please offer a suggestion.
 
Both my GRT units respond the same, turn knob slower, it keeps up, spin it like a roulette wheel and the lag appears. Just how it works, always has for me, no an issue, but it does happen.
 
On the earlier SX, at one time I had a problem with the rotary encoder.

I *think* there was a fix that involved the equivalent of a a rubber washer.
Also, I am pretty sure that the problem at that time got fixed in later units.

So you may just have a failure of the encoder.

On the other hand, there **IS** a difference in how it responds based on the SPEED of your turn. That is by design. Rotation speed modifies how fast it jumps in changing the altimeter setting and modifies whether you are adjusting 10's or 100's of feet altitude.

I would call GRT and leave a specific question. They will get back to you via email or phone call with the answer. You can also post to the GRT forum and an answer will be provided.
 
If you have dual GRT EFIS’s, try setting the baro with the other screen. I had this same problem with my RV4 which had a Horizon, and a mini-X. One was slaved to the other, and the slaved one couldn’t keep up. I don’t know if this is normal, but you could try it.
 
I would call GRT and leave a specific question. They will get back to you via email or phone call with the answer. You can also post to the GRT forum and an answer will be provided.

I’m reluctant to contact GRT directly. My experience last summer with their tech support wasn’t pleasant and the exchange left a bad taste in both my mouth and theirs.
 
Speed of rotation is definitely a factor. I have a Mini-X, HX and Sport EX - all three are tied to the inter-display link so baroset is synchronised across the three EFIS units. I've had what appeared to be lag in the baroset, but what it really turned out to be was GRT's software saying "don't be an idiot - spin it that fast and you'll grossly overshoot your target". I slow down the spin a bit and, even then, sometimes overshoot the target but do so without lag.
 
GRT’s response appreciated

My GRT EX EFIS system seems to resist the quick setting of the altimeter and intended climb altitude before takeoff. Here’s what is happening:

1. Barometer setting: I attempt to set the airport altimeter heard over AWAS after engine start but when I go to enter the setting (say 30.15) the right knob will turn quickly but the change in the window is not immediate. In fact I have to stop turning the knob and wait for window readout to catch up and then continue trying to set the barometer in the EFIS.

2. Climb Altitude setting: Again, on the ground, I try to setup my initial climb out altitude using the right knob and instead of changing the big numbers first (hundreds of feet) it goes immediately to tens of feet. When I turn it quickly it just delays the setting of my intended climb out altitude because you have to wait for the (tens of feet) to catch up.

Thought I’d share with VAF folks GRT’s response to my problems in case anyone else experiences these issues. Haven’t had the opportunity to implement their suggestions but will let folks know how they worked. I’m hopeful!

If the number bounces around when you turn quickly, check SET MENU, General Setup, Inter-Display Link, Inter-Display Link ID on both screens. One of them needs to be set to "Primary" and the other can be Auto or 2.

If that's good, make sure the knob functions correctly. The best way to test knob rotation is to scroll up and down in the SET MENU. If that doesn't work well we may need to send you a software update to change how it senses the knob rotation.

2. The altimeter will go to tens of feet mode if you last set or synchronized a non-zero tens or if you let the setting mode sit for 5 seconds. If you round it to 100 and exit then the next time it will start by setting the hundreds.”


Scott, jclark and BH1166: you might want to also check this out since it possibly could also help you too.
 
Last edited:
Thanks.

I had had that discussion with them some years ago, so I was aware. Mine has been fine for years.
 
2. Climb Altitude setting: Again, on the ground, I try to setup my initial climb out altitude using the right knob and instead of changing the big numbers first (hundreds of feet) it goes immediately to tens of feet. When I turn it quickly it just delays the setting of my intended climb out altitude because you have to wait for the (tens of feet) to catch up.

In my experience, if you wait too long after the initial turn of the knob, it will move from 100's to 10's. Once you first turn the knob, you need to keep going or it will go to 10's. After the initial few turns, it seems the timer is lengthened.

Larry
 
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