AV-30-C vs regular vacuum DG

2nd505th

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2nd505th
Which is more accurate- The AV-30C with magnetometer or a refurbished vacuum DG? My current vac DG drifts 20 degrees in a turn. What kind of drift do the AV-30-Cs experience?
 
Even an AV-30c without a magnetometer will do less than 20 degree drift. With the magnetometer, it's pretty accurate. If you connect it to the GPS source it's synced to GPS track. If you don't mind mentally adjusting for heading vs. track this is also a good option.

I have one AV-30c and I plan to add another. The big question for you is what is your path for integrating to an autopilot? If none, then I would say the AV-30c is a great option.

If an autopilot integration is in your future, it looks like AV-30 won't be supporting an interface anytime soon. They are going down the cheaper path of supporting the Aerocruz and the Trio.

I was looking at the Aerocruz anyway. So it fits my needs.
 
A mechanical DG should do better than that, sounds like yours needs an overhaul. My mechanical DG when healthy would drift about 5-10* every 15 mins, depending on how much maneuvering I was doing. Last year the AI needed another overhaul so I replaced both AI & DG with dual AV-30 and removed the vac system entirely. The AV-30 without a magnetometer drifts about the same as the mechanical. The big drawback to the AV-30 in DG mode is when the temperature changes significantly from what it was when the DG aligned itself during startup (example: take off in 50* F air then climb to sub-freezing temps), it drifts so bad it becomes useless.

Due to this temperature issue, I just bought the external magnetometer but haven't yet installed it.
 
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A mechanical DG should do better than that, sounds like yours needs an overhaul. My mechanical DG when healthy would drift about 5-10* every 15 mins, depending on how much maneuvering I was doing. Last year the AI needed another overhaul so I replaced both AI & DG with dual AV-30 and removed the vac system entirely. The AV-30 without a magnetometer drifts about the same as the mechanical. The big drawback to the AV-30 in DG mode is when the temperature changes significantly from what it was when the DG aligned itself during startup (example: take off in 50* F air then climb to sub-freezing temps), it drifts so bad it becomes useless.

Due to this temperature issue, I just bought the external magnetometer but haven't yet installed it.
I've heard a lot on the AV-30s without an external magnetometer as being not too good. But many say with a magnetometer it improves a lot. But does it get better than a standard vacuum DG? If not and it is not at least better then perhaps I should just get mine overhauled. It would be way cheaper. I'm looking for better data on just how well it maintains accuracy with the magnetometer. Does it also degrade more when maneuvering? But if I could get 5 degrees drift per hour would be superb.
 
The AV-30 in DG mode had issues early on and uAvionix released several firmware updates to improve the error correction. The current versions without the magnetometer perform similar to a healthy mechanical gyro. Your goal of 5* per hour is far better than a standard vacuum DG or the AV-30C. Is it possible with the external magnetometer? Maybe - I will find out soon myself, but someone here may post their results.

With the external magnetometer I would expect no drift at all because it's an electronic compass that directly measures the Earth's magnetic field. But what do I know?
 
So I contacted UAvionix and they said with the external magnetometer there is no drift. Zero. (can anyone vouch?) Also asked them if pitot tube sharing causes any loss of airspeed information - they answered 'no'. Also they plan to have a lot of autopilot integration in the future, with tru-trak, trio, s-tec and century. Good stuff to know.
 
So I contacted UAvionix and they said with the external magnetometer there is no drift. Zero. (can anyone vouch?) Also asked them if pitot tube sharing causes any loss of airspeed information - they answered 'no'. Also they plan to have a lot of autopilot integration in the future, with tru-trak, trio, s-tec and century. Good stuff to know.
Pitot tube follows Bernoulli's principle of pressure. Pressure is felt across the entire system. It doesn't take much air volume to change the instrument reading so the pressure can be distributed to multiple instruments. I have 3 instruments attached to my pitot/static. They use t-fittings with quick connectors.

Good to know they are planning to add Century. Will they do it in this century? (LOL)
 
Which is more accurate- The AV-30C with magnetometer or a refurbished vacuum DG? My current vac DG drifts 20 degrees in a turn. What kind of drift do the AV-30-Cs experience?
Mine is extremely accurate with the magnetometer. Next to no drift
 
So I contacted UAvionix and they said with the external magnetometer there is no drift. Zero. (can anyone vouch?) Also asked them if pitot tube sharing causes any loss of airspeed information - they answered 'no'. Also they plan to have a lot of autopilot integration in the future, with tru-trak, trio, s-tec and century. Good stuff to know.
We added the magnetometer and that eliminated the annoying drift.
 
Which is more accurate- The AV-30C with magnetometer or a refurbished vacuum DG? My current vac DG drifts 20 degrees in a turn. What kind of drift do the AV-30-Cs experience?

How is your vacuum system?
 
AV-30C drift without the magnetometer in our Grumman traveler was 30 degrees off after a few minutes or after clearing turns. With the magnetometer, it's great and right on the money. In my opinion they shouldn't be sold separately anymore.
 
Without the magnetometer mine was a little better, but similar to, the mechanical one it replaced. And no vacuum system!

With the magnetometer, there is no drift at all. I’m a happy customer.

Head to head, the GI 275 is better. But budget….
 
Gaah, I gotta get that stupid field update harness made so I can flash my AV-30C to the new firmware version. That's the only thing stopping me from using the Mag. Like many others, I find the DG mode unusable without the magnetometer.

Initial test flights with my restored Decathlon show the AV-30C performs fine in AHI mode. Once I finish engine break-in and start flying acro, I'll post some videos of how long it holds orientation during extreme attitudes, and how long it takes to recover. Will be interesting to compare to my previous device, an RC Allen 2600, which was quite impressive.
 
So I contacted UAvionix and they said with the external magnetometer there is no drift. Zero. (can anyone vouch?).
You may not quite understand the purpose of a magnetometer. Any installation with one is constantly correcting, so there is no drift unless something is broken. Any DG or HSI with a magnetometer is detecting the magnetic north pole itself, so it should always be spot-on. After all, you don't hear about airline pilots resetting their DGs every 15 minutes - because they have magnetometers too.
 
Regarding DG drift, remember that the rotation of the Earth itself is about 15* per hour, so a perfect unslaved gyro drifts at least that much.
A magnetometer nips that in the bud, turning the DG into a slaved magnetic compass.
 
If you are going to fly IFR, and are going to go to the trouble to install a magnetometer in the wing (typical) anyway, consider getting a G5 or GI275, which are true HSIs that will integrate with your IFR GPS as a primary CDI, and also direct an autopilot.
 
I wish I had a dime for every time I heard the promise of "in the future" in aviation. Reminds me of the old lyric " Domani, forget domani, for domani never comes.
 
If you are going to fly IFR, and are going to go to the trouble to install a magnetometer in the wing (typical) anyway, consider getting a G5 or GI275, which are true HSIs that will integrate with your IFR GPS as a primary CDI, and also direct an autopilot.
Good advice. The uAvionix magnetometer is inexpensive so the entire system (vac removal, dual AV-30C) is still significantly less expensive than Garmin. My avionics shop quoted $6k for uAvionix versus $9k for Garmin (both prices all-in). uAvionix is great for VFR only airplanes like mine. But if you're going IFR, the Garmin system is more capable and worth the extra bucks for most people.
 
Fair, for one system.

But if you have a desire to delete the vacuum system you'll need 2, in most cases.

And budget.....

VFR and IFR are different decision processes.
 
Fair, for one system.
But if you have a desire to delete the vacuum system you'll need 2, in most cases.
...
Indeed. Both quotes I mentioned were for complete vac system removal and dual instruments. I'm sure the prices have gone up over the past year but the ratio between them is probably unchanged (Garmin about 50% more).
 
Good advice. The uAvionix magnetometer is inexpensive so the entire system (vac removal, dual AV-30C) is still significantly less expensive than Garmin. My avionics shop quoted $6k for uAvionix versus $9k for Garmin (both prices all-in). uAvionix is great for VFR only airplanes like mine. But if you're going IFR, the Garmin system is more capable and worth the extra bucks for most people.
Find an A&P to check your work and do the AV-30 install yourself. Really easy.

I agree, UAvionix is an excellent VFR solution, but Garmin is superior for IFR.
 
After fixing the heading drift with our AV-30's, now we have an issue with the airspeed being off. I would be ok if it was within a few mph of the old analog airspeed indicator, but it's around 7-9 mph off on the high side. Moreover, at all altitudes the TAS on the display is slower that the indicated. That could be installation error or something is malfunctioning.
I've flown in IMC with both dual G5s and dual AV-30s. Hand flying, the G5 are better mainly because of the true HSI with glideslope, but the AV-30s are capable when they're working properly and its limitations understood. I have trust issues though.
 
After fixing the heading drift with our AV-30's, now we have an issue with the airspeed being off. I would be ok if it was within a few mph of the old analog airspeed indicator, but it's around 7-9 mph off on the high side. Moreover, at all altitudes the TAS on the display is slower that the indicated. That could be installation error or something is malfunctioning.
I've flown in IMC with both dual G5s and dual AV-30s. Hand flying, the G5 are better mainly because of the true HSI with glideslope, but the AV-30s are capable when they're working properly and its limitations understood. I have trust issues though.
The install manual will tell you how to trim the IAS.
 
After fixing the heading drift with our AV-30's, now we have an issue with the airspeed being off. I would be ok if it was within a few mph of the old analog airspeed indicator, but it's around 7-9 mph off on the high side. Moreover, at all altitudes the TAS on the display is slower that the indicated. That could be installation error or something is malfunctioning.
I've flown in IMC with both dual G5s and dual AV-30s. Hand flying, the G5 are better mainly because of the true HSI with glideslope, but the AV-30s are capable when they're working properly and its limitations understood. I have trust issues though.
Mine was way off until I set the calibration offset correctly. Now my altitude is within 20 feet of my original altimeter and airspeed is within about +/- 2 knots of over the entire range (I fly at 150 IAS so the range is wide). I calibrated my airspeed at 100 IAS. You also need to calibrate your OAT to the field elevation, not the analog gauge that came with your airplane. That made a big difference for me.

My TAS shows a few knots higher than ground speed. I'm not sure why. But it's within 1-2 knots of my analog TAS. At 160 ground speed (corrected for winds) I usually show 165 TAS. At lower speeds like say 120 knots the difference is not really noticeable. At the same IAS my airspeed reads about 1 knot high on the AV-30. (I calibrated to 100 knots).
 
Find an A&P to check your work and do the AV-30 install yourself. Really easy.

I agree, UAvionix is an excellent VFR solution, but Garmin is superior for IFR.
I did self install. I wouldn't say "really easy". That would depend on skill level. The install involves wiring harnesses and pitot-static tubing. The OAT needs to be installed outside which usually requires drilling a hole in your airplane skin or an inspection panel.

I've used the AV-30 in IFR IMC. It works. "Superior" I would say means two things. 1) a larger display. 2) Maybe a slightly faster reaction time / smoother. GI-275 is also certified as a primary on lots of stuff, but you still need a backup. uAvionics didn't certify the altimeter and airspeed because it would drive the cost up. It just means you need to keep your existing airspeed, altimeter and vertical speed. AV-30 is a gyro replacement, not a glass panel.

I don't think uAvionix is trying to compete with Garmin. Likely it is the other way around. Garmin suspiciously came out with the GI-275 just after uAvionix AV-30 was certified. uAvionics is competing against vacuum instruments, which is an easy sell because they fail often. I've had 3 attitude indicators and 1 vacuum pump fail in the last 8 years.

If I had $11,000 to burn I would install two GI-275's. But if I could afford $2500 and all I had were vacuum instruments, I would immediately rip those out and install at least one AV-30.
 
Mine was way off until I set the calibration offset correctly. ...
Same here. My temperature sensor was off, which threw off the density altitude and true airspeed values. After I trimmed the temperature to read properly, the rest was also correct. That's something the installers should do, but at least it's user-configurable.
 
I'm going to try trimming the OAT and IAS settings tomorrow. Have 4 legs planned. Hopefully I'll have it all set by the end of the day. I still having difficulty understanding why the TAS would consistently read slower than the IAS even if the OAT is off. Perhaps it's possible the TAS readout is in knots while the IAS is displaying in mph?
 
Did some testing today. AV-30 DG drifted 30 degrees in 10 minutes, 90 degrees in 20 minutes, and 180 degrees in 30 minutes. Straight and level flight.
 
I'm going to try trimming the OAT and IAS settings tomorrow. Have 4 legs planned. Hopefully I'll have it all set by the end of the day. I still having difficulty understanding why the TAS would consistently read slower than the IAS even if the OAT is off. Perhaps it's possible the TAS readout is in knots while the IAS is displaying in mph?
Be sure to read the manual about calibrating the airspeed. I believe it should be done at a specific point in your green or white arc. (I don't remember exactly what it said). For my airplane that works out to 105 IAS. Yours will probably be different.
 
Did some testing today. AV-30 DG drifted 30 degrees in 10 minutes, 90 degrees in 20 minutes, and 180 degrees in 30 minutes. Straight and level flight.

Didn't you add the external magnetometer?
 
Not yet, still gotta flash the unit to new firmware

OK that explains it. I'm looking at the experimental unit but I'm gonna add the magnetometer if/when I do.

I'm sure you know that there is a Wi-Fi connector available so that it's easier to do updates (listed as only allowed for experimental installs):

 
Hey, my vacuum system failed a few weeks ago so I’ve been doing all my hood training partial panel. I’m for sure going with dual AV-30s and an av-20 for the right seat and ripping out the vacuum system. Got quoted $3500 for install, is that reasonable?
 
Hey, my vacuum system failed a few weeks ago so I’ve been doing all my hood training partial panel. I’m for sure going with dual AV-30s and an av-20 for the right seat and ripping out the vacuum system. Got quoted $3500 for install, is that reasonable?
It's likely that a lot of labor charge is for removing the vacuum system. Often when you remove tubing all the zip ties will need to be redone for wiring.

Actual AV-30 install is pretty easy. If installing three units most likely they will do a pitot-static hub quick connector. AV-20 requires only power and pitot-static.

Are you getting the magnetometer installed?
 
It's likely that a lot of labor charge is for removing the vacuum system. Often when you remove tubing all the zip ties will need to be redone for wiring.

Actual AV-30 install is pretty easy. If installing three units most likely they will do a pitot-static hub quick connector. AV-20 requires only power and pitot-static.

Are you getting the magnetometer installed?

Yes planning on it. Also 2 OATS, one for the av-20 and on for the DG
 
Be sure to read the manual about calibrating the airspeed. I believe it should be done at a specific point in your green or white arc. (I don't remember exactly what it said). For my airplane that works out to 105 IAS. Yours will probably be different.

I'll dig back in the manual. I trimmed the airspeed and it is now within a 1-2 mph of the analog airspeed indicator. Also trimmed the OAT, matching temp to the AWOS. However, the TAS readout is still off. Sometimes it's ten mph less than the IAS others times it is just a few mph slower.
 
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