TruTrak Gemini PFD Pirep / Feedback

[Brantel]

Just so this review is complete, after flying for a while behind the Gemini, i have the following observations. Nothing major but stuff to know and understand. Posted this on the TT forum and I am waiting on a response:

"Lucas,

I now have a few hours behind my Gemini PFD.

I have a couple questions/concerns:

The past few times I have turned on the unit sitting on the ground I have noticed that it settles to about 2-3degrees of right bank instead of the wings level indication. In the beginning it would always slowly go to wings level indication no matter what angle it was actually in. Over a period of like 10 minutes it eventually started showing wings level again like i would expect. Is this error temp related or???

The PFD is shows a slight offset on airspeed from my Dynon. Is there anyway that you can give the end user the ability to tweak the indication?

The PFD is indicating about 25-35 ft lower than my Dynon which just past an IFR static/alt/xponder test last month....it was dead on. Is there any way you can give the end user the ability to tweak the altitude indication?

I have noticed that in a sustained high rate turn that when I roll wings level that the PFD shows about a 5 degree roll angle error for a while till it settles out. Is there anything that can be done about that?

Today I was climbing out after take off and climbing at a 10 degree pitch up indicated on the Dynon and at 1000fpm on the Dynon. The PFD was showing 2----2 for the entire climb. I was not climbing at 2000fpm and I was not at 20degrees of pitch up. What gives with this indication?"

[kevinh]

Thanks Brantel,

Can you update this thread when you get a reply? I'm thinking about buying one.

[TrutrakTech]

The 2-3 degree bank offset is temperature related. The gyros are calibrated at operating temperature so until they get fully up to temp there may be a slight offset. 2-3 degrees should be as much as you see on that.

What is the difference you see on the airspeed?

There isn't a way for the end user to change the altimeter calibration. Do you see this discrepancy all the time or only after power up? This could also be temperature related.

I'll look into the other two issues. The vertical speed display was tested extensively against several references so I'm not sure what's going on in yours.

Originally Posted by Brantel

Just so this review is complete, after flying for a while behind the Gemini, i have the following observations. Nothing major but stuff to know and understand. Posted this on the TT forum and I am waiting on a response:

"Lucas,

I now have a few hours behind my Gemini PFD.

I have a couple questions/concerns:

The past few times I have turned on the unit sitting on the ground I have noticed that it settles to about 2-3degrees of right bank instead of the wings level indication. In the beginning it would always slowly go to wings level indication no matter what angle it was actually in. Over a period of like 10 minutes it eventually started showing wings level again like i would expect. Is this error temp related or???

The PFD is shows a slight offset on airspeed from my Dynon. Is there anyway that you can give the end user the ability to tweak the indication?

The PFD is indicating about 25-35 ft lower than my Dynon which just past an IFR static/alt/xponder test last month....it was dead on. Is there any way you can give the end user the ability to tweak the altitude indication?

I have noticed that in a sustained high rate turn that when I roll wings level that the PFD shows about a 5 degree roll angle error for a while till it settles out. Is there anything that can be done about that?

Today I was climbing out after take off and climbing at a 10 degree pitch up indicated on the Dynon and at 1000fpm on the Dynon. The PFD was showing 2----2 for the entire climb. I was not climbing at 2000fpm and I was not at 20degrees of pitch up. What gives with this indication?"

[Brantel]

Thanks Lucas on the bank angle offset. Your info confirms what I thought I was seeing.

The airspeed difference is minor < 5 knots

The altitude offset is constant.

Looking forward to the answers on the last two questions.

Originally Posted by TrutrakTech

The 2-3 degree bank offset is temperature related. The gyros are calibrated at operating temperature so until they get fully up to temp there may be a slight offset. 2-3 degrees should be as much as you see on that.

What is the difference you see on the airspeed?

There isn't a way for the end user to change the altimeter calibration. Do you see this discrepancy all the time or only after power up? This could also be temperature related.

I'll look into the other two issues. The vertical speed display was tested extensively against several references so I'm not sure what's going on in yours.

[TrutrakTech]

Is the airspeed always ~5kts off or is it relative to current speed?

We verified the vertical speed again today using three methods; tested against our own EFIS, tested against the G3X display, and timed manually. It was right on target.

The only other thing I can think of on the vertical speed is that it is also temp related if this was on takeoff. The pressure transducers also have to get up to temp. I'll look further into this.

[Brantel]

Originally Posted by TrutrakTech

Is the airspeed always ~5kts off or is it relative to current speed?

We verified the vertical speed again today using three methods; tested against our own EFIS, tested against the G3X display, and timed manually. It was right on target.

The only other thing I can think of on the vertical speed is that it is also temp related if this was on takeoff. The pressure transducers also have to get up to temp. I'll look further into this.

Lucas, will have to fly again to be sure on the airspeed. I will scan the video I made as well and see how it relates on there.

I think the VS was temp related because later in the flight I could not get it to do the same thing again.

The ambient temp that day was around 80°F.

EDIT: I scanned thru the video I made http://youtu.be/KtlLPJzRXtg

You can see the airspeed difference is pretty minor on that flight. About 2 maybe 3 knots. I can live with that. I doubt two different sensors are going to get much better.

You can see the altitude difference varies from about 25ft to about 35ft.

The vertical speed seems to close on that flight.

I thinks some of the difference is that you guys have different filtering algorithms. That will make a difference.

At 6:20, 7:10 and 8:10 you can see the bank angle error that comes into play after an extended coordinated turn.

@ 8:30 I started doing some pretty good pitch changes and they were pretty close.

See you at Osh!

[Tom Martin]

I have a few flights with my PFD now and it is working properly. The airspeed, altitude and heading match perfectly with my AFS 4500 effis. The rate of turn and attitude indications also mimic the 4500. With my older and wiser eyes I am not sure if this unit would be large enough to be my primary instrument but as a standby unit it really puts a lot of information in a small space.

[777Dave]

Can someone elaborate on how vertical speed is presented? Is it numerical? Can't seem to see it on the video...

I'm leaning toward the Gemini in my VFR RV4 .... no ADI whatsoever at the moment. Prefer an instrument that has actual ASI and altimeter.

Thanks

[Brantel]

The Vertical Speed is indicated via the horizontal lines of the attitude display.

Since the attitude display is instantaneous gyro info that transitions over time to vertical speed, once you have a vertical speed established, the attitude display is vertical speed.



The arrow in the above pic is pointing at the 1000ft/min up indication for VS. The scale of the VS indicator changes depending on air speed.

In the video, starting at around 8:35:00, you can see me do a few ups and downs and cans see how the VS indication works when compared to the Dynon.

[rocketbob]

Originally Posted by Brantel

Since the attitude display is instantaneous gyro info that transitions over time to vertical speed, once you have a vertical speed established, the attitude display is vertical speed.

Not so. On the way home from OSH I discovered we have a static leak. Opening and closing avent would result in a 300 fpm climb/descent nearly instantly. Interestingly enough the Gemini will show a climb and keep showing a climb which tells me its just a VSI. As far as I'm concerned that's fine as long as one understands how the instrument operates. In a skidding turn it will flat out lie to you. 30 degrees of right bank with quite a bit of left rudder will show a left turn.