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  #1  
Old 06-12-2021, 08:36 PM
scrollF4's Avatar
scrollF4 scrollF4 is offline
Moderator, Asst. Line Boy
 
Join Date: Jan 2010
Location: Flower Mound, TX
Posts: 1,595
Default Skyview HDX: Runaway ADAHRS

I have a sudden problem with both of my HDX ADAHRS units. Last week my avionics guy (among this community’s very best, so don’t think I’m knocking him) accomplished KELLI GIRL’s biannual pitot/static/transponder IFR cert. No problems, no leaks.

On the first flight (day VMC), about 1 minute after takeoff, the gyro- and mag-based instruments want tango uniform. Both ADAHRS tumbled, and not at the same rate or direction. The mag compass just picked a direction and started spinning.

The attached photo shows an example during straight and level flight (I swear it! I can't get the photo to stay upright ). Note the difference between the PFD mag heading and the mag track on the map display.

(Oh, and don't judge my switch alignment. Remember: An amateur built my airplane.)

All the while, I got several continuous and successive “ADAHRS Mismatch” warnings. When I compared the two ADAHRS outputs, each differed from the other, but neither was correct, so I couldn’t pick one.

Meanwhile, the GPS-based information stayed rock solid (the map, ground track, course, ground speed). The pitot/static readings (KIAS, altitude, and vertical velocity) were also reliable, as was the TAS. After landing for fuel and returning home, they worked PERFECTLY on the second flight.

That was Wednesday. It happened again yesterday (Friday): Two flights, the first one with major ADAHRS errors, but the second one perfectly fine.
I called Dynon after Friday’s flights: They recommended I perform a compass calibration which I did on the surveyed Compass Rose at KGLE (thank you 99s!).

In today’s 5 flights, the first three flights showed errors but each subsequent flight showed an improvement over the previous flight. Flights 4 and 5 were perfect. Of note, on today’s last flight I opened up the airborne compass calibration page and noted heading accuracy levels ABOVE 100% so I know the heading is capable of being spot on.

So here’s where I stand. Data from GPS and pitot/static looks rock solid. It appears that the gyro-derived or gyro-influenced information (attitude indicator, turn/slip, and mag heading) are somehow goofed up. Oh, and autopilot and flight director? That was an adventure all its own. KELLI GIRL is red-X for IFR flight until I get this figured out.

Now, I did inspect my ADAHRS units behind the baggage wall: Nothing loose, no misplaced tools, no loose connections. My avionics guy confirmed that he didn’t disconnect/reconnect the units or their electrical connections: He did nothing to them other than check the security of the air lines (no leaks).

I will get back in touch with Dynon to see where they want me to go next. HOWEVER, have any of you run into this issue? How did you resolve it?
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__________________
Scroll

Sid "Scroll" Mayeux, Col, USAF (ret)
52F NW Regional/Aero Valley Airport, Roanoke TX (home of DR's Van Cave)
"KELLI GIRL" N260KM RV-7A tipper
Catch her on YouTube's "Because I Fly!" channel

Exemption waived.
Proud and grateful 2021 -=VAF=- Contributor

PS: I am not an influencer. I have no influence. Just ask my kids.
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  #2  
Old 06-12-2021, 10:58 PM
Pdtofly Pdtofly is offline
 
Join Date: Jan 2012
Location: Reno, NV
Posts: 506
Default Did he turn off the pitot static test mode?

Did the shop forget to turn off the pitot static mode test in Dynon, or forget to turn it on before the test?

Read the following on how to perform the pitot static check to understand why you turn it on.

Performing Pitot/Static Checks

Background

Dynon Avionics SV-ADAHRS-200/201 use airspeed in the calculation of attitude (or GPS ground speed when airspeed is unavailable). The internal rate sensors are monitored and calibrated in flight using feedback from the accelerometers and from airspeed to achieve a highly accurate attitude solution.

When a pitot or static test is performed the sensors in the SV-ADAHRS-200/201 are being exposed to dynamics that are impossible to achieve in a real aircraft flight environment, namely, large airspeed changes without the accompanying accelerations and rotations. This false condition will cause a well-calibrated unit to incorrectly adjust its calibration. Furthermore, when a unit is in a test situation a change in applied pitot or static pressure will cause the attitude to pitch up or down. This is expected.

SkyView contains a special mode that allows you to perform required altimeter and/or airspeed checks without affecting the calibration of the attitude-sensing components.

Pitot/Static Test Instructions

This test must be used when performing pitot/static, transponder, or other tests that manipulate either the pitot or static pressures.

Before conducting any pitot/static testing, follow these guidelines:

View System Installation Guide – Revision AI 5-23

1. The aircraft itself should be temperature stable. For example, if the aircraft is moved from outside in the sun to a hangar for testing, tests should not be started until the airplane has stabilized at the hangar temperature. 2. Turn SkyView on and let it warm up until the altitude reading is stabilized. This period should be at least 5 minutes, but may take longer depending on environmental conditions.

To enter pitot/static test mode, go to:

SETUP MENU > HARDWARE CALIBRATION > ADAHRS CALIBRATION > PITOT STATIC TEST MODE.
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  #3  
Old 06-13-2021, 06:03 AM
RVDan RVDan is offline
 
Join Date: Jun 2012
Location: Frederick, MD
Posts: 931
Default

As stated in post #2, this is a known issue if the static system test function is not used.
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Frederick, MD
PA28-140
Hph 304CZ
RV6 built and sold
N199EC RV6A flying
Retired Aerospace Engineer and A&P/IA
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  #4  
Old 06-13-2021, 08:13 AM
Scotty G Scotty G is offline
 
Join Date: Aug 2020
Location: PHX
Posts: 111
Default

Great info here; thanks for posting.
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CHD
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  #5  
Old 06-13-2021, 09:08 AM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,120
Default

I'm the guy that did the P-S test, I've done plenty of Dynon's, all run in test mode except for the minor adjustment for alt offset to get '0' altitude within limits (you can't do the offset in test mode). I've done plenty of Dynon certs the same way but I have never heard of anyone having this problem after finishing.
It certainly appears that my small excursions of P-S pressures, with the units turned on but prior to the actual testing taking place caused some kind of software issue with this/these units.
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1900+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 06-13-2021 at 10:12 AM.
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  #6  
Old 06-13-2021, 09:34 AM
WenEng WenEng is offline
 
Join Date: Aug 2008
Location: Jacksonville, FL
Posts: 528
Default Welcome to first time

Quote:
Originally Posted by Walt View Post
I'm the guy that did the P-S test, I've done plenty of Dynon's, ..... I have never heard of anyone having this problem after finishing.
I have learned to apply cause/effect logic long ago. You are no doubt a smart experienced person whose input I have relied on many times on VAF. In this situation, I would always have first questioned what possibly had changed from last flight to 1st problem flight. I would be asking, in this case, you, to revisit this work to see if anything was amiss.

Just my 2cents and don't take offense at my logic. None meant.
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RV-6A 3/4 done...N48JE Reserved
Build site: www.mykitlog.com/weneng
Donated to VAF in 2021
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  #7  
Old 06-13-2021, 09:47 AM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,120
Default

Quote:
Originally Posted by WenEng View Post
I have learned to apply cause/effect logic long ago. You are no doubt a smart experienced person whose input I have relied on many times on VAF. In this situation, I would always have first questioned what possibly had changed from last flight to 1st problem flight. I would be asking, in this case, you, to revisit this work to see if anything was amiss.

Just my 2cents and don't take offense at my logic. None meant.
Don't disagree, it would appear I will have to be more careful during "setup" with the Dynon systems, however it's practically impossible to have zero airspeed/alt excursions during initial setup checking connections and leak rates before starting the testing.
Apparently even small excursions with the Dynon when not in 'test mode' subject the system to parameters it can't deal with.

When I do an altitude offset adjust I have always driven the alt to '0' ft to do the adjustment, our field elevation varies with pressure alt but usually around 700 ft, so perhaps going from 700 ft to 0' ft when not in test mode is what caused this? (Just thinking out loud). I've always done it this way without problems but maybe I need to revise my procedure.

I know some folks that just quit doing Dynon testing before/after the "white paper" procedure came out due to all the problems/hassle.
I'm getting a little leery myself now again after this, seems like the system is a bit 'finicky'.
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1900+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 06-13-2021 at 10:33 AM.
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  #8  
Old 06-13-2021, 06:38 PM
Don Jones's Avatar
Don Jones Don Jones is offline
 
Join Date: Nov 2005
Location: Snohomish, Washington
Posts: 704
Default

Quote:
Originally Posted by scrollF4 View Post
I have a sudden problem with both of my HDX ADAHRS units. Last week my avionics guy (among this community’s very best, so don’t think I’m knocking him) accomplished KELLI GIRL’s biannual pitot/static/transponder IFR cert. No problems, no leaks.

On the first flight (day VMC), about 1 minute after takeoff, the gyro- and mag-based instruments want tango uniform. Both ADAHRS tumbled, and not at the same rate or direction. The mag compass just picked a direction and started spinning.

The attached photo shows an example during straight and level flight (I swear it! I can't get the photo to stay upright ). Note the difference between the PFD mag heading and the mag track on the map display.

(Oh, and don't judge my switch alignment. Remember: An amateur built my airplane.)

All the while, I got several continuous and successive “ADAHRS Mismatch” warnings. When I compared the two ADAHRS outputs, each differed from the other, but neither was correct, so I couldn’t pick one.

Meanwhile, the GPS-based information stayed rock solid (the map, ground track, course, ground speed). The pitot/static readings (KIAS, altitude, and vertical velocity) were also reliable, as was the TAS. After landing for fuel and returning home, they worked PERFECTLY on the second flight.

That was Wednesday. It happened again yesterday (Friday): Two flights, the first one with major ADAHRS errors, but the second one perfectly fine.
I called Dynon after Friday’s flights: They recommended I perform a compass calibration which I did on the surveyed Compass Rose at KGLE (thank you 99s!).

In today’s 5 flights, the first three flights showed errors but each subsequent flight showed an improvement over the previous flight. Flights 4 and 5 were perfect. Of note, on today’s last flight I opened up the airborne compass calibration page and noted heading accuracy levels ABOVE 100% so I know the heading is capable of being spot on.

So here’s where I stand. Data from GPS and pitot/static looks rock solid. It appears that the gyro-derived or gyro-influenced information (attitude indicator, turn/slip, and mag heading) are somehow goofed up. Oh, and autopilot and flight director? That was an adventure all its own. KELLI GIRL is red-X for IFR flight until I get this figured out.

Now, I did inspect my ADAHRS units behind the baggage wall: Nothing loose, no misplaced tools, no loose connections. My avionics guy confirmed that he didn’t disconnect/reconnect the units or their electrical connections: He did nothing to them other than check the security of the air lines (no leaks).

I will get back in touch with Dynon to see where they want me to go next. HOWEVER, have any of you run into this issue? How did you resolve it?

Sid,
I would definitely like to talk to you about this. It isn't normal and would like to get to the bottom of it. Shoot me an email to my attention at support@dynonavionics.com with a good time to call and best contact number
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Don Jones
Technical Support Manager
Dynon Avionics
CFI-IA, AGI, IGI
RV9-A
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  #9  
Old 06-13-2021, 07:58 PM
scrollF4's Avatar
scrollF4 scrollF4 is offline
Moderator, Asst. Line Boy
 
Join Date: Jan 2010
Location: Flower Mound, TX
Posts: 1,595
Default

Quote:
Originally Posted by Don Jones View Post
Sid,
I would definitely like to talk to you about this. It isn't normal and would like to get to the bottom of it. Shoot me an email to my attention at support@dynonavionics.com with a good time to call and best contact number
Wilco, Don.
__________________
Scroll

Sid "Scroll" Mayeux, Col, USAF (ret)
52F NW Regional/Aero Valley Airport, Roanoke TX (home of DR's Van Cave)
"KELLI GIRL" N260KM RV-7A tipper
Catch her on YouTube's "Because I Fly!" channel

Exemption waived.
Proud and grateful 2021 -=VAF=- Contributor

PS: I am not an influencer. I have no influence. Just ask my kids.
Reply With Quote
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