EFIS Question

I know there are no stupid questions, but I've had some before .. anyway, I recently installed an EFIS in my RV. This stuff is all new to me. I did not choose to also install the Magnetometer. However, I was a little surprised to see that there is no way to set a "directional gyro" to the compass as we "round gage" folks normally do. At least that would give me what I had before. Any comments? (Other than what you may be thinking!!)

Which EFIS?

If you have no magnatometer most that I am familiar with show TRACK, which jump around until you actually move the GPS and it shows a track then.

Anytime the plane is moving even a knot or two, you will have the track indicated.

There is not and likely will not be any means to set the heading on the EFIS to match your aircraft's magnetic compass.

Without a magnetometer installed, the heading information shown will NOT be heading but rather will be GPS GROUND TRACK. In fact you will likely see it display dashes or some other symbology to flag it as invalid data unless the aircraft is moving and actually producing a ground track.

Just to be clear, inside your EFIS there isn't a spinning iron gyro like there is your DG. The "gyros" inside your EFIS are semiconductor devices which are dependent on a ton of software to properly interpret their output and convert that output into usable information. Each of those sensors is somewhat dependent on the others, thus the attitude displayed does not come from a single attitude sensor but rather from an array of sensors which are used to produce all the indications on the screen (pitch, role, yaw, G etc).

It's the complexity of deriving all the other indications on the EFIS screen that preclude the ability to allow us to "set the DG". If you want a real DG-like indication, installing the magnetometer is the only way you'll likely be able to get magnetic heading displayed.

I've been asking for years for a "free running DG" mode from a couple of different EFIS manufacturers. This is because I have every intention of flying in the north where compass reliability is poor. So far both manufacturers have told me the same thing - having a setable DG just isn't in the works.

pilotmansam said:

I know there are no stupid questions, but I've had some before .. anyway, I recently installed an EFIS in my RV. This stuff is all new to me. I did not choose to also install the Magnetometer. However, I was a little surprised to see that there is no way to set a "directional gyro" to the compass as we "round gage" folks normally do. At least that would give me what I had before. Any comments? (Other than what you may be thinking!!)

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Why would you want an additional instrument. The reason they have DGs is because they behave better than a mag compass in turning flight, but the downside is that they drift so they have to be reset. The yaw axis gyro in the efis doesn't have misbehave during turning flight and it doesn't drift so does not need to be reset. I don't really know what part of the heading display comes from the gyro and what comes from the gps, but it is transparent to the pilot. You have one heading indication and it is correct and doesn't need to be reset and doesn't have deviation so you don't have to worry about a compass card.

It seems like we are so used to working around the limitations of the old type of instruments that we want to continue using the work arounds even if they are no longer required.

pilotmansam said:

I know there are no stupid questions, but I've had some before .. anyway, I recently installed an EFIS in my RV. This stuff is all new to me. I did not choose to also install the Magnetometer. However, I was a little surprised to see that there is no way to set a "directional gyro" to the compass as we "round gage" folks normally do. At least that would give me what I had before. Any comments? (Other than what you may be thinking!!)

Click to expand...

The short answer - install the magnetometer.

If you do not have another compass, you are not legal to fly.

Your comment on ?this would give me back what I had before? is telling. What you had before is simply not in the same league with a modern EFIS install. Of late I?ve been flying a plane with a full IFR six pack panel, including a 430W. After years of flying with a dual SKyView install, it is like I?m back in the Stone Age. The iPad with ADS-B in rarely leaves my hand.

Carl

Which EFIS is an important question. The different vendors have slightly different approaches. Did you install an ADAHR or something with a similar acronym? With some vendors, this will substitute for a magnetometer.

For example, my first EFIS required a ahrs and a magnetometer. My current EFIS has everything is a single box.

It sounds like you're saying you have an EFIS that has an optional external magnetometer, and you chose not to install it. If that's right, chances are your instructions gave you specific direction on how to install and align the display and associated AHARS unit with respect to the longitudinal axis of the aircraft. So, it has an internal magnetometer.

The external magnetometer is often needed in aircraft with full avionics suites due to electromagnetic interference at the instrument panel.

Compare your GPS track to your ADAHARS heading when directly into the wind, or no wind condition. They should agree within a fairly small margin of error. Just like an HSI, there's no need to align to wet compass.

Also, there should be some guidance in your install manual for checking for RF/electromagnetic interference with your EFIS installation.

Carl Froehlich said:

The short answer - install the magnetometer.

If you do not have another compass, you are not legal to fly.
Carl

Click to expand...

Well, since he is asking about an EAB airplane, I think the correct statement should be ?.....you are not legal to fly at night, nor under ifr.?

BobTurner said:

Well, since he is asking about an EAB airplane, I think the correct statement should be ?.....you are not legal to fly at night, nor under ifr.?

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Well, the regs require a Magnetic Direction Indicator, even for VFR! I don't think GPS Track meets the requirements, but I'm not a DRE, or the FAA.

I see from your old posts that this is an RV6 which previously had a full compliment of steam gauges and the EFIS is a GRT Sport EX which replaced several of those 6 pack gauges.

So Sam:

• the Sport EX has an adaptive AHRS which includes an internal magnetometer.
  
• it does have the option of connecting an external one if you want to fit one in the plane and the internal one isn't giving a very accurate heading.
  
• a magnetometer input keeps your EFIS heading reference permanently slaved to the earth's magnetic field. No need to fiddle with it the old fashion way, once a calibration is done (see manual). Most EFIS displays will revert to displaying GPS track if a magnetometer input is not present so that can't be manually altered anyway.

DGlaeser said:

Well, the regs require a Magnetic Direction Indicator, even for VFR! I don't think GPS Track meets the requirements, but I'm not a DRE, or the FAA.

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Yes, for type certificated a/c.

For experimentals? I'm no authority, but I've been told that no instruments are required at all, for day VFR.

Boy, am I amazed at the response one gets to a question on this forum! Thank you everyone for the feedback. I believe Canadian_JOY gave me the response I needed. (It's just too hard to do and the magnetometer does not cost that much.)
My EFIS is the GRT EX but I sometimes am reluctant to discuss specific products here. But, it does seem to be working great as advertised. It does not have an internal magnetometer which is available as an option which I decided to just add later. I was just thinking that it just seemed that you should be able to "electronically" set a digital DG. Don't really no why I care, there's not that much wind here in the SE anyway!