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petersb

Well Known Member
The MGL installation manual says that the AHARS is dangerous in turbulent cloud conditions and should not be used, even Rainer has said this in forums, are they being extra cautious due to liability reasons? This caution is also given for their expensive AHARS.

My Dynon D10A also tilts slightly in mild turbulents probably for the reason discused above, how does the Skyview perform?

I read that the Grand Rapids and AFS units are used for heavy IFR, are their AHARS different?

Peter
 
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Even the best gyros can be off a bit in turbulent conditions.
If it's bumpy enough to be bouncing my instruments around, it's too bumpy for me to be flying and I get on the ground as soon as possible.
 
Yes, we still have that statement and a bit of explanation as to why in our manuals. We do realize that we seem to be the only ones doing this but will continue with this even if that means we loose sales.
Modern strapdown AHRS systems are relative devices. This means they can only measure relative rotations. They actually have no idea where the ground is - a seperate system that is included in any AHRS called an accelerometer (or pendulous unit in a vaccum driven gyro) errects the image when this is possible (which is the case in unaccelerated flight).
A modern AHRS can also use other sources of information such as from a GPS or even airspeed indicator to assist (but never completely fix the issue).
Like others, our AHRS has been in continued development for nearly 10 years now and obviously, they are getting better (now in generation 7) and will continue to do so. We are even working on a laser gyro system for a very demanding space based application and guess what - even that has limitations and very real ones.
We strongly feel that it is our responsibility to inform any user of possible limitations. We have come across too many (even professional) pilots that do not understand these limitations and put blind faith into an AHRS, ignoring common sense procedures that used to be tought as part of IF and IMC training. Even with the best and most expensive EFIS money can buy, nothing much has changed in physics. Gravity is still a bitch.

Rainier
CEO MGL Avionics

petersb said:
The MGL installation manual says that the AHARS is dangerous in turbulent cloud conditions and should not be used, even Rainer has said this in forums, are they being extra cautious due to liability reasons? This caution is also given for their expensive AHARS.

My Dynon D10A also tilts slightly in mild turbulents probably for the reason discused above, how does the Skyview perform?

I read that the Grand Rapids and AFS units are used for heavy IFR, are their AHARS different?

Peter
Click to expand...
 
Rainier Lamers said:
We strongly feel that it is our responsibility to inform any user of possible limitations. We have come across too many (even professional) pilots that do not understand these limitations and put blind faith into an AHRS, ignoring common sense procedures that used to be tought as part of IF and IMC training. Even with the best and most expensive EFIS money can buy, nothing much has changed in physics. Gravity is still a bitch.

Rainier
CEO MGL Avionics
Click to expand...

I'm still learning IFR flying and only have about 8 hours simulated IMC behind a standard 6 pack. If I was training behind an EFIS, how would I be able to detect if it were not accurate? Or is it good enough to simply be aware that it may not be accurate in turbulence?

Seems like something you'd pick up on flying in VFR conditions.
 
jbagley said:
I'm still learning IFR flying and only have about 8 hours simulated IMC behind a standard 6 pack. If I was training behind an EFIS, how would I be able to detect if it were not accurate? Or is it good enough to simply be aware that it may not be accurate in turbulence?

Seems like something you'd pick up on flying in VFR conditions.
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How do you know if you're vacuum driven attitude indicator is accurate? (Rhetorical question, the answers are the same eithe way.)
 
Sig600 said:
How do you know if you're vacuum driven attitude indicator is accurate? (Rhetorical question, the answers are the same eithe way.)
Click to expand...

You have more than one indication. The horizon (equivalent to what a vaccum or electrical gyro shows) is just one of them.
It is also the first to "loose" it (and it matters not at all if you have a old spinning top gyro or a modern strapdown AHRS).
You have a directional indicator, either a gyro based one, magnetic or a combination. If things get iffy, you're no longer that much interested in actual directions (which can be wrong by now) but if you are turning and in what direction. Obviously, if you're lost - the first thing to establish is that you are not turning. Then you have the slip indicator. Get that ball in the middle and you're balanced. If that coincides with not turning you're almost there. Now look at your VSI. That is a pretty reliable instrument. Are you going down or up ? What does the altimeter say ? Don't forget - in what position are your controls ? Look at them !

You get the idea. The above is a rough outline and is EXACTLY the same if you have a fancy EFIS (no matter what the price tag), a cheap one or are flying behind steam gauges.
Your training should include progressive instrument failure while flying under the hood. You need to be able to cross check all indications to recognize when an instrument indicates wrongly and then exclude that from your mind.
You have a lot to help you even in bad situations if you can keep a level head and stop screaming.

One example of when this does not happen is the Air France crash a year or so ago. That could have been avoided.

Rainier
CEO MGL Avionics
 
I have had an EFIS roll inverted just 50 feet AGL on a zero zero takeoff. I am convinced there should be backups to an EFIS. One may argue if those backups must be old school or not but absolutely backups are needed.
 
petersb said:
The MGL installation manual says that the AHARS is dangerous in turbulent cloud conditions and should not be used, even Rainer has said this in forums, are they being extra cautious due to liability reasons? This caution is also given for their expensive AHARS.

My Dynon D10A also tilts slightly in mild turbulents probably for the reason discused above, how does the Skyview perform?

I read that the Grand Rapids and AFS units are used for heavy IFR, are their AHARS different?

Peter
Click to expand...


There are issues with any and all instruments that are installed in your aircraft. As the PIC, it is your responsibility to understand the limitations of each instrument in your aircraft. Rainrer is perhaps a little more verbose that some of the other vendors in regards to the AHARS. But, your traditional DG also has issues as Craig mentioned. Just ask anyone that does aerobatics.

To minimize the risk for IFR, you'll want dual AHARS. However, that still has issues. Most EFIS has the capability to tell you which AHARS goes bad. Then you have to figure out which one is still accurate. As Rainier mentioned you have to depend on other sources to assist you in your decision making process. This is one of many reasons that folks planning on flying IFR will install another EFIS from a different vendor as backup to become a tie breaker.

The process is not much different if your standard DG starts to roll over.

bob
 
how badly does turbulence affect the displayed results

Trying to understand what is the issue is, and how badly it can affect what is displayed. Is is just the transients build in some short term error (too many rapid changes and local flex of struucture) or is it you can be hundreds of feet off for prolonged periods..... and many degrees off.

I haven't heard this before with ADHRS systems, and want to understand before getting all excited and convinced it is the way to go, and trust.
 
My experience has shown it needs to be damned violent for quite a while to get the kind of drift that will bring you a severe downgrade of accuracy.

When it gets that bad for that long you may be more worried about how to maintain an attitude with wings or flight controls missing:eek:

The small amount of drift I have seen has quickly gone away again, as Rainer says above, all instruments suffer drift.

I doubt the MGL gear will kill you that easily. Nor the others. But it is an interesting fact.
 
This is a terribly difficult question to answer. The only unsatisfactory answer is: "It depends".
Your AHRS installation is the most important part here. Understand what the AHRS has to do and it becomes clear what you need to do to make it work well. You must ensure that the AHRS roll rate measurments are not corrupted. One of the worst sources of corruption are vibrations and movements caused by airframe shocks. The AHRS needs to measure your roll rates with almost incredible accuracy - even small errors will quickly accumulate and render your device useless. Any AHRS has a maximum roll rate that it can measure. Bottom end is around 150 degrees/second while the top end currently is around 400 degrees/second. Vibration and movement of the AHRS relative to your aircraft due to bad installation method or location can easily exceed this rate and the result is never good.

Some time ago we had a Jabiru in with bad AHRS performance. Is was fine straight and level but would go out in a turn fairly fast. The owner had installed the unit below the seats directly on the airframe skin - and that got buffeted by prop wash causing the issue. Relocation solved the issue.
This just as a small example.

So, assuming a good quality AHRS using current generation gyros - what can you expect ? Assuming a good installation of course, you can put your aircraft into a turn and keep it there for hours and the AHRS will be just fine. The older electrical gyros and vaccum driven ones will slowly errect as they will think you are straight and level after a while (just how long depends on the errection force of the pendulous unit).
In turbulence it gets interesting - usualy, there is no issue as algorithms are clever and can average your gravity vector. Keep in mind older devices have severe limitations regarding pitch and bank angles - modern AHRS systems can follow you through aerobatics quite well.
It needs to get really bad (and I mean extended kind of bad for some time) before a good AHRS will become suspect - as long as you do not exceed its abilities.
In an uncontrolled, rapid rate, random tumble (not exceeding measurement rates) a good AHRS can follow you quite well for perhaps 30 to 120 seconds before errors start getting noticable. This is a situation where aiding does not work as aircraft attitude cannot be assumed (I know, it is possible - but not in our kind of environment or budgets).

Rainier
CEO MGL Avionics

thinkn9a said:
Trying to understand what is the issue is, and how badly it can affect what is displayed. Is is just the transients build in some short term error (too many rapid changes and local flex of struucture) or is it you can be hundreds of feet off for prolonged periods..... and many degrees off.

I haven't heard this before with ADHRS systems, and want to understand before getting all excited and convinced it is the way to go, and trust.
Click to expand...
 
RV10inOz said:
My experience has shown it needs to be damned violent for quite a while to get the kind of drift that will bring you a severe downgrade of accuracy.

When it gets that bad for that long you may be more worried about how to maintain an attitude with wings or flight controls missing:eek:

The small amount of drift I have seen has quickly gone away again, as Rainer says above, all instruments suffer drift.

I doubt the MGL gear will kill you that easily. Nor the others. But it is an interesting fact.
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I concur...... If you are flying in weather bad enough to cause an AHARS failure, one might question your risk management decision making ability.
 
Turbulence

I've had numerous occasions flying into Denver or Reno where Center has reports of severe turbulence in clear air. The reports are from 737's, 767's, etc. I have been beat up pretty bad too when I least expected it, with no reports and in clear air. Maybe I didn't read enough but I don't remember seeing this warning on my Garmin system and in the Collins/Honeywell systems I fly in.
 
Rainier Lamers said:
Your training should include progressive instrument failure while flying under the hood. You need to be able to cross check all indications to recognize when an instrument indicates wrongly and then exclude that from your mind.
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It seems like instrument failure and instrument error are two different things. An EFIS that displays an incorrect image due to prolonged turbulence hasn't really failed, its just exceeded its normal range of operating conditions. This is a lot different than vacuum pump failure.

So how to do you effectively cross-check an EFIS if the AHRS is already taking all the raw data into account to compute the image it displays?
 
petersb said:
The MGL installation manual says that the AHARS is dangerous in turbulent cloud conditions and should not be used, even Rainer has said this in forums, are they being extra cautious due to liability reasons? This caution is also given for their expensive AHARS.

My Dynon D10A also tilts slightly in mild turbulents probably for the reason discused above, how does the Skyview perform?

I read that the Grand Rapids and AFS units are used for heavy IFR, are their AHARS different?

Peter
Click to expand...

The simple answer to the question is it depends on how much money you are willing to invest in the EFIS system.

All modern jets are equipped with EFIS systems and reliability in turbulence is not an issue. It wasn't an issue 15 years ago when I worked for a living and it isn't today.

But the cost of such a system is in an experimental airplane would be way beyond what anyone here is willing to pay. There are people flying with what is available but the reliability factor has not been proven to government standards set for commercial operators.

That's the bottom line of it. If you fly IFR with EFIS at this level you do so at a greater risk than if you buy a ticket and travel with SWA.
 
Thank you for the good answers.

No comments on comparisons to the other systems that are available, eg: Skyview etc

I normally only fly VFR, however if turbulence upset the AHARS then this could also occur VFR, in Canada we can fly over the clouds and are expected to decend in VFR, however, you can get caught and have to do a basic decent through cloud into VFR.

Peter
 
I have the Dynon 100.

My EFIS is over 5 years old and the early, non-synthetic vision model and has taken me up and down through more cloud layers than I can count. Never a failed mode or wrong indication of attitude. The more I fly it IFR, the more confident I become....these things are just that good.

On cross-country flights, you're flying straight and level mostly, so no need for any real worries about it becoming upset and not tell you whether you're upright or not. My ADI autopilot is a great backup for that anyway.

The one failed EFIS vendor is no longer in business and the companies that remain all produce good, dependable products.

Best,
 
Everything that Rainier says it true - there is no such thing as a perfect EFIS from an engineering standpoint. However, if you are looking for perfection in any human design, you won't find it - everything has limitations. I have spent enough of my life (as have thousands of others) flying behind mechanical gauges that are affected by temperature, turbulence, wear, debris, etc, etc. If you compare the limitation of the modern electronic attitude systems to the real-world limitations of the old stuff (not to a non-existent "idea") you'll probably discover that from a reliability standpoint, it is hard to beat any of the current crop of experimental EFIS's. I have an awful lot of time using GRT, Dynon, Garmin...and some time with AFS as well. (One of these days, I need to fly behind your stuff Rainier, and I look forward to it!) I've never had a serious attitude issue - and I have been in turbulence that cracked a canopy. this is not high on my worry list.

I do, of course, subscribe to the practice of having independent, dissimilar backups if my life depends on the data I am receiving from my panel, and I constantly cross-check to make sure I am not being lied to. ALL equipment will eventually let you down in some way, so have a plan....
 
Rainier Lamers said:
You get the idea. The above is a rough outline and is EXACTLY the same if you have a fancy EFIS (no matter what the price tag), a cheap one or are flying behind steam gauges.
Your training should include progressive instrument failure while flying under the hood. You need to be able to cross check all indications to recognize when an instrument indicates wrongly and then exclude that from your mind.
You have a lot to help you even in bad situations if you can keep a level head and stop screaming.

One example of when this does not happen is the Air France crash a year or so ago. That could have been avoided.

Rainier
CEO MGL Avionics
Click to expand...

I've done partial panel work with a 6 pack and have enjoyed the challenge (especially while hand flying an RV!). But, it seems harder to train for this with an EFIS. Is it possible to simulate a partial failure in an EFIS for the purpose of training? Or is it better to train on a 6 pack? I know that Advanced Flight Systems simulates a 6 pack on their display partially for this purpose.

Having the airspeed slowly drop to zero would be much more realistic than putting a card over the airspeed indicator. But, probably this is a better idea for the simulator!
 
I guess if we are looking for an absolute bullet-proof-system to be completely safe, flying behind a simulator would be the only option.

However, as others have noted, EIFS can and are safe enough for many including airliners to fly behind them. One of course can increase the odds by installing multiple systems.

My dual GRT which has redundant AHAR has been performing far better than expected specially in steep turns or turbulence. The redundant AHAR continuously checks against drift with each other and reports and discrepancies which have been fine so far in turbulence, loops and roles. But I also have a set of steam gauges as a backup, mainly as a concern to any electrical problem rather mechanical.
 
Question to the experts

I have an early Dynon D-10 as my primary attitude reference, backed up by steam altmeter, VSI and airspeed. I recently replaced my electric turn needle ball with the Trutrak Pictoral Pilot. I file IFR routinely and have no problem filing into "IFR lite" (lets not open that thread drift channel), single pilot with a good autopilot and moving map GPS with geo-referenced approaches.

My area has some geography that produces some fairly consistent turbulence. Maybe twice, while practicing on the gauges in some uncomfortable and repeated bumps, I have seen the Dynon "flicker" into a 60 degree or so AOB that obviously did'nt actually happen to the airplane. This isolated spurious indication was momentary - a "blink", with the indication instantly righting itself and all normal.

Is this the type of anomaloy that you might expect to see in a turbulence confused AHRS????

I consider the Dynon to be as good and reliable as any attitude system I have ever flown behind (primarily military grade traditional stuff). I beleive that the electronics (even these "experimental grade" ones) are at least as reliable as vacumn or electric gyros. I also have some confidence that I could stay out of trouble using my combination steam and digital (Pictoral Pilot) partial panel backups and related auto pilot in the event of AHRS failure.

How does that square with the risk management judgement of others???

By the way, I have chosen not to use the altitude, airspeed, vsi tapes on the dynon. I scan the steam gauges (arranged in the classic 6 pak) for this info, using the dynon for attitude and heading only. This seemed a logical way for me to ease into the transistion toward a full EFIS. A side benefit is that it might be a help in seamlessly transistioning back to a partial panel scan if that would ever be necessary too!
 
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EFIS's in IFR

I'm using the GRT EFIS's (three ) with dual AHRS, with backup Airspeed, Altitude and a TruTrak ADI (round gages). A TruTrak autopilot acts as another level of redundency. I do routinely fligh hard IFR (200' at 1/2 mile vis approaches and have frequenly 'taken the extra 100 ft' when only the rabbit was seen).
I have seen differences in the AHRS (one failed in IFR). Between the other AHRS (GRT allows them to be seperated as well as 'Dual'), the whiskey compass, and the ADI, I was able to isolate the failure, and continue to my destination. (The autopilot can also be used to resolve heading differences.)
That said, nothing is perfect. Never rely on a single attitude source in IFR. Always have redundency. If you have two of the same technology, have a third type to resolve differences between the two common types. ALWAYS cross check.... If you haven't anything to do while flying in IFR, you've forgotten something!

petersb said:
The MGL installation manual says that the AHARS is dangerous in turbulent cloud conditions and should not be used, even Rainer has said this in forums, are they being extra cautious due to liability reasons? This caution is also given for their expensive AHARS.

My Dynon D10A also tilts slightly in mild turbulents probably for the reason discused above, how does the Skyview perform?

I read that the Grand Rapids and AFS units are used for heavy IFR, are their AHARS different?

Peter
Click to expand...
 
Well, since redundancy has been mentioned...

Our new iEFIS system allows you to connect no fewer than 4 independent AHRS systems in a vote based system with automatic exclusion on any failure detect.
In addition, our GPS based AHRS is a very interesting - drift free - alternative that has the huge advantage to be based on a completely different technology - so this is a great tool to compare the AHRS against in flight and a good confidence booster.

From a reliability point of view, I think I can state with some measure of confidence that modern strap down AHRS systems, in particular the latest crop like our SP-7 which uses a single mass gyro are way beyond what old mechanical systems could do. There is simply nothing to wear or break if unusual attitudes or forces are presented (i.e. no caging requirements).

Our SP-7 was the recent attitude (and autopilot gyro) source that flew the Sling-4 aircraft right around the World (99.8% of the time with engaged autopilot). For those that did not follow this little adventure - this included some truly hair raising periods in very bad conditions.

I think it is time to welcome even low cost AHRS systems into the "as good as it gets" hall of aircraft instrumentation fame...
The days when these things would topple if looked at skew are long gone.

On second thoughts - it's perhaps a better idea to move the source of worry from the EFIS to that engine up front...

Rainier
 
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