How accurate are garmin avionics?

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Hengelo

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Hengelo
Pitch & roll: is the margin of error 1%, 2%, 5%?

…?
 
Thanks. Looking for a real answer to the question.
 
I mean are they accurate to a degree or a tenth of a degree?
 
Hengelo said:
I mean are they accurate to a degree or a tenth of a degree?
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Installation calibration?
TSO requirements?
???

You ask a question with several answers depending on what you're looking for...
 
texasclouds said:
Garmin is dead nuts accurate…
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For TAS as well? My newish 275 reads a few knots faster than the steam gauge. Both are plumbed into the same pitot-static system (which had all the tubing replaced when the 275 went in). I wanna believe the 275 but just checking.

But I think you’re right.
 
Llewtrah381 said:
For TAS as well? My newish 275 reads a few knots faster than the steam gauge. Both are plumbed into the same pitot-static system (which had all the tubing replaced when the 275 went in). I wanna believe the 275 but just checking.
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Absolutely! You paid good money to go faster ;)
 
The accuracy might be more limited by the display resolution than electronics sensors.
 
Llewtrah381 said:
For TAS as well? My newish 275 reads a few knots faster than the steam gauge. Both are plumbed into the same pitot-static system (which had all the tubing replaced when the 275 went in). I wanna believe the 275 but just checking.

But I think you’re right.
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Your steam gauge shows TAS?
 
midlifeflyer said:
Your steam gauge shows TAS?
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It has a knob you turn to set the temp vs alt, which moves a ring (white in the pix) to show TAS. Both the CAS and TAS on the steam gauge consistently read a few knots lower than the 275.

Yep - I was at 16K in my (180hp) Warrior. A solid endorsement for ElectroAir!

IMG_6237.pngIMG_6238.jpeg
 
StraightnLevel said:
As stated above, the question in the OP doesn't have a single clear answer.

Some background to help clarify:
1) Are you asking about accuracy or precision? In general, analog sensing has theoretically infinite precision but is limited by noise, mechnical issues, and accuracy of the installation and calibration; digital systems are precision-limited, based on the resolution of the A/Ds used in the system.
2) Are you asking about the sensor, the processing unit, or the display? Each limits the overall combined accuracy and precision, and the interactions are not always obvious.
3) Are you asking about theoretical maximum numbers, or are you asking how to determine the performance of an installed system?
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OP: What time is it?

StraightnLevel: This is how you build a watch…..:lol:
 
Llewtrah381 said:
It has a knob you turn to set the temp vs alt, which moves a ring (white in the pix) to show TAS.
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That's pretty standard. I thought you were referring to to a direct readout rather than what is essentially an "in-the-ballpark" slide rule/E6B which depends on the accuracy of the ASI, the accuracy of the Kollsman, temperature and airspeed lines on both the ASI and the OAT, the accuracy of your reading of those items, and the degree of perfection of your manual fine-tuning lining things up.

Hmmm... I wonder which is more accurate ;)
 
It does seem there should be some standard and some statement of accuracy. There is such a standard for car speedometers, but I can’t recall what it is. Something like +3%, -0%. And given the importance of knowing attitude, I’m sure there’s some standard for certified flight instruments, and some known performance from Garmin.
 
midlifeflyer said:
That's pretty standard. I thought you were referring to to a direct readout rather than what is essentially an "in-the-ballpark" slide rule/E6B which depends on the accuracy of the ASI, the accuracy of the Kollsman, temperature and airspeed lines on both the ASI and the OAT, the accuracy of your reading of those items, and the degree of perfection of your manual fine-tuning lining things up.

Hmmm... I wonder which is more accurate ;)
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The knob correlates pretty well with the result I get from the E6B in my Aera 660 - typically either spot on or off by a knot either way. Same with the 275 and the E6B, for that matter, since the IAS is consistently lower on the steam gauge than the 275.

Interestingly the altimeter reads a few feet lower on the 275 gauge than the steam gauge, which isn’t a huge surprise given the age and nature of the steam gauge.

ADD: I’m totally fine with believing the 275 is the “gold standard”, which, intuitively, seems correct. But I didn’t want the fact that I’m now seeing 130KIAS or better in my lowly Warrior to just be a gauge lying to me.

IMG_6239.jpeg
 
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If the pilot can’t use the altimeter in the GI275 as primary (per the GI275 manual - see warnings) why would the pilot be able to use the airspeed indicator as primary?
 
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I think you'd want to talk about how it performs in specific scenarios since the attitude sensing works, at least partially, by integrating the rate gyro and accelerometer signals - which will make the accuracy time variant.

The ADC items- airspeed, altitude, are a lot easier since they can make a direct pressure measurement in the pitot-static systems, apply whatever corrections they need, and display the results - they're quasistatic measurements, maybe with some low pass filtering applied to deal with transients.
 
bentmettle said:
I think you'd want to talk about how it performs in specific scenarios since the attitude sensing works, at least partially, by integrating the rate gyro and accelerometer signals - which will make the accuracy time variant.
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I sometimes watch my AV-30 when flying aerobatics. It lags during aggressive maneuvering, eventually losing orientation after >5 complex maneuvers in close sequence, then recovers after 5-10 seconds of upright flight. But "aggressive maneuvering" means far more rapid attitude and heading changes than would ever be experienced in IFR flight. One of these days I'm going to video a test sequence and post it.

Most digital AI's that display airspeed and altitude have a trim function in setup to adjust for error.
 
I haven't tried looking online at the Garmin website, but there's probably some regulation somewhere that publishes tolerances that have to be met.
 
Ed Haywood said:
I sometimes watch my AV-30 when flying aerobatics. It lags during aggressive maneuvering, eventually losing orientation after >5 complex maneuvers in close sequence, then recovers after 5-10 seconds of upright flight. But "aggressive maneuvering" means far more rapid attitude and heading changes than would ever be experienced in IFR flight. One of these days I'm going to video a test sequence and post it.

Most digital AI's that display airspeed and altitude have a trim function in setup to adjust for error.
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Interesting. E-attitude instruments zonk out if you exceed the listed rate, or if they're mems-based, the installation vibration exceeds the filter gain. Most acro spam cans don't have the control authority to tumble at rates to do that, unless the instrument is consumer grade junk. Decathlons are not particularly avid tumblers, they're quite slow rollers too, so I'm gonna go with the AV-30 is consumer grade as far as attitude presentation resiliency is concerned. Bummer, I'm generally a fan of uavionix. In fairness, I had an equally underwhelming experience with a Dynon D1 portable EADI back in the early 2010s. In that case the problem was vibration. It just could not tolerate the operational environment, it was not dependable and became a brick in my flight bag pretty much instantly.

Didn't you use to own an RCA that gave you better attitude performance? Honestly surprised, I would expect e-indicators plumbed to the pitot system to be more resilient than mems-only indicators like the RCA. Latter which I used to own too for a few months in the arrow before the bolts tried to come from together inflight, but I digress.
 
hindsight2020 said:
Didn't you use to own an RCA that gave you better attitude performance? Honestly surprised, I would expect e-indicators plumbed to the pitot system to be more resilient than mems-only indicators like the RCA. Latter which I used to own too for a few months in the arrow before the bolts tried to come from together inflight, but I digress.
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I did have an RC Allen 2610. I think the performance was similar to the AV-30, but that is just a general impression, nothing quantifiable or objective. Here is a sequence with the RCA from several years ago. You can see it at the bottom of the screen whenever the G forces are increased.
 
Wow, just saw it. yeah that's pretty bad. Well then, I stand corrected on giving the AV-30 crap, seems like that's par for the course with these spam can electronics writ large. That level of precession and red-Xing on the attitude indicator would be an immediate code3 grounding mx write up in the T-6 or T-38, and we don't do even tail slides or hammerheads in those not-for-tumbling built turbine applications mind you. At least the mechanical gyros, much as they're damaged by these flight profiles, can be manually quick-erected in level flight.
 
Ed Haywood said:
I sometimes watch my AV-30 when flying aerobatics. It lags during aggressive maneuvering, eventually losing orientation after >5 complex maneuvers in close sequence, then recovers after 5-10 seconds of upright flight.
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So basically once it gets some g force pointing in the same direction on its accelerometers long enough, it resets its attitude calculation errors…
 
Matthew said:
I haven't tried looking online at the Garmin website, but there's probably some regulation somewhere that publishes tolerances that have to be met.
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If the box is built to one or more technical standard orders one of them or a referenced spec will have tolerances under a variety of conditions. If it meets the TSO it will be as good as or better than the tols.

Nauga,
standardized
 
Llewtrah381 said:
For TAS as well? My newish 275 reads a few knots faster than the steam gauge. Both are plumbed into the same pitot-static system (which had all the tubing replaced when the 275 went in). I wanna believe the 275 but just checking.

But I think you’re right.
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Uuh, do mean IAS? TAS is calculated from IAS and temp and pressure altitude.

Some steam gauge air speed indicators have a scale that can be set to read TAS, but many forget that you need to set your altimeter to 29.92 to get pressure altitude to set that scale.
 
Llewtrah381 said:
It has a knob you turn to set the temp vs alt, which moves a ring (white in the pix) to show TAS. Both the CAS and TAS on the steam gauge consistently read a few knots lower than the 275.

Yep - I was at 16K in my (180hp) Warrior. A solid endorsement for ElectroAir!

View attachment 129200View attachment 129199
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Did you set your altimeter to 29.92 for pressure altitude to set the TAS ring??????
 
KE5BM said:
Smaller instruments require higher precision...jus' sayin' :ihih:
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This is where we begin an argument about the difference between precision and accuracy. I think that this form of argument is colloquially known as a ****ing match.
 
iamtheari said:
This is where we begin an argument about the difference between precision and accuracy. I think that this form of argument is colloquially known as a ****ing match.
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*laugh*

Former engineering teaching assistant - this is specifically one of the points taught in the experimental engineering class I taught in. Not much of an argument in my class. You either knew it or you went into sales :D
 
bentmettle said:
*laugh*

Former engineering teaching assistant - this is specifically one of the points taught in the experimental engineering class I taught in. Not much of an argument in my class. You either knew it or you went into sales :D
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...thus explaining why sales drones talk about accuracy when they mean precision and talk about precision when they mean bovine excrement.
 
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