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Ground speed wrong in 750?


Gregg_Seipp

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Posted
35 minutes ago, RXP said:

I don't know but I think I'm confused too LOL! Maybe it's time for me to really switch off this computer and sleep over it!

Not sure about my day tomorrow, but perhaps the resident meteorologist can take a flight and see what's up (or down). I am a stickler that my real world based flight plans be closely reflected when in the air with FSX, and winds aloft and enroute times are an important element of that as they dictate fuel burn.  I have been too long in the hangar/shop the past several days so its time to catch some air...

Frank Patton
Corsair 5000D Airflow Case; MSI B650 Tomahawk MOB; Ryzen 7 7800 X3D CPU; ASUS RTX 4080 Super; 
NZXT 360mm liquid cooler; Corsair Vengeance 64GB DDR5 4800 MHz RAM; RMX850X Gold PSU;; ASUS VG289 4K 27" Display; Honeycomb Alpha & Bravo, Crosswind 3's w/dampener.  
Former USAF meteorologist & ground weather school instructor. AOPA Member #07379126
                       
"I will never put my name on a product that does not have in it the best that is in me." - John Deere

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Posted

Ok. So here is my planned flight for tomorrow (If I can find time) from Easton, Maryland, to Spirit of St Louis, Missouri. Take a look at the wind component column I circled.  Virtual headwinds so this should be a great determinate.  My weather engine is Real World Global Weather, which I have high confidence in with over 1,000 logged hours using their weather feed.

I have not yet logged a flight with the RXP GTN's so this should tell the tale if there is an issue.  My flights with the v2 GNS gauges have been accurate.

http://12-10-17 plan-XL.jpg

 

Frank Patton
Corsair 5000D Airflow Case; MSI B650 Tomahawk MOB; Ryzen 7 7800 X3D CPU; ASUS RTX 4080 Super; 
NZXT 360mm liquid cooler; Corsair Vengeance 64GB DDR5 4800 MHz RAM; RMX850X Gold PSU;; ASUS VG289 4K 27" Display; Honeycomb Alpha & Bravo, Crosswind 3's w/dampener.  
Former USAF meteorologist & ground weather school instructor. AOPA Member #07379126
                       
"I will never put my name on a product that does not have in it the best that is in me." - John Deere

Posted

Okay, so here's a screencapture I just did.  Looks like the issue is the direction of the wind arrow in the GTN.

  • Wind is in the upper left 233 magnetic at 87 knots...what a tail wind I have!
  • The arrow is pointing as if I have a side wind
  • I calibrated my airspeed indicator.  -13 degrees at FL210.  True airspeed is 258 KIAS.  Add that 87 knot tailwind it would be 345 knots ground speed.  
  • So, the ground speed actually looks right...it's the wind arrow that's pointing the wrong way.

 I remembered to check the DALT/TAS/Wind a bit later.  It shows 233 at 93KT.  The P3D wind at altitude showed 232 at 92 at that time.  The wind arrow was showing as if the wind was about 010 degrees at 93.

Open the image below in a new tab so you can read my small captions.

pUD9Dci.jpg

Gregg Seipp

"A good landing is when you can walk away from the airplane.  A great landing is when you can reuse it."
i7-8700 32GB Ram, GTX-1070 8 Gig RAM

Posted

Hard to see the text labels on your image but yes something is screwy.  I'm not seeing that though.  But maybe I don't have the latest version either.  Which version do you have? (of the RXP gauges)

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Posted
2 hours ago, fppilot said:

Not sure about my day tomorrow, but perhaps the resident meteorologist can take a flight and see what's up (or down).  I have been too long in the hangar/shop the past several days so its time to catch some air...

Yeah, you have to open it in another tab and then zoom in.  Where do I find the version?

Gregg Seipp

"A good landing is when you can walk away from the airplane.  A great landing is when you can reuse it."
i7-8700 32GB Ram, GTX-1070 8 Gig RAM

Posted
15 minutes ago, ryanbatcund said:

Hard to see the text labels on your image but yes something is screwy.  I'm not seeing that though.  But maybe I don't have the latest version either.  Which version do you have? (of the RXP gauges)

Yeah, you have to open it in another tab and then zoom in.  Where do you find the version?

Gregg Seipp

"A good landing is when you can walk away from the airplane.  A great landing is when you can reuse it."
i7-8700 32GB Ram, GTX-1070 8 Gig RAM

Posted
25 minutes ago, Gregg_Seipp said:

Where do you find the version?

Open up the RXP Configuration Panel in sim and check updates (lower left of window).

GTN and GNS. are updated.

 

 

Posted
6 minutes ago, bills511 said:

Open up the RXP Configuration Panel in sim and check updates (lower left of window).

I don't see a "Check Updates" in the Add Ons->Reality XP GTN->Aircraft Setup dialog.

Gregg Seipp

"A good landing is when you can walk away from the airplane.  A great landing is when you can reuse it."
i7-8700 32GB Ram, GTX-1070 8 Gig RAM

Posted
7 minutes ago, Gregg_Seipp said:

I don't see a "Check Updates" in the Add Ons->Reality XP GTN->Aircraft Setup dialog.

Press and hold the SHIFT key then RIGHT-Click the top edge of the GTN device to open the configuration panel.

 

 

Posted
5 minutes ago, bills511 said:

Press and hold the SHIFT key then RIGHT-Click the top edge of the GTN device to open the configuration panel.

Thanks Bill.  I got it right clicking the left bezel.  I clicked Check Updates and there is an update so I downloaded it.  I'll install it in the morning.  Pretty late here on the east coast.

Gregg Seipp

"A good landing is when you can walk away from the airplane.  A great landing is when you can reuse it."
i7-8700 32GB Ram, GTX-1070 8 Gig RAM

Posted

Is it common for antivirus to report problems with the update?  Just asking.

Gregg Seipp

"A good landing is when you can walk away from the airplane.  A great landing is when you can reuse it."
i7-8700 32GB Ram, GTX-1070 8 Gig RAM

  • Commercial Member
Posted

Thank you Gregg for the screenshot and info, this helps. It looks like it the arrow is off by (180-6) roughly (taking measurements from the screenshot). KMCO magvar is 6W... ;-)

Or I can see you're flying HDG 73 and WIND 233, 73+233 = 306 which is roughly the wind arrow on your screen, in other words, we might be feeding the wind direction but need to subtract the acft heading to the value (i.e. feed relative wind vector instead of absolute wind vector).

This leads me to: I wonder what version you were running because we've made changes to this computation specifically a few versions back, nevertheless, it could be also a bug in GTN Trainer 6.41 vs 6.21 (what I mean by 'bug' is the trainer might be using a different data source, say direction to in true, instead of direction from in mag).

We'll review this and see what we can find, because this used to pass our synthetic tests, but you never know what bug we've introduced lately as well.

Jean-Luc | reality-xp.com
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Posted
45 minutes ago, Gregg_Seipp said:

Is it common for antivirus to report problems with the update?

It is common for antivirus to report false positives with our files, only because they are protected with specific 'protection' technologies. They also embed a 'taggant' which is s technology agreed upon by A/V vendors and protection vendors, so as to not flag false positives since the file can be traced back, nevertheless, some A/V vendors fail miserably.

Jean-Luc | reality-xp.com
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Posted
Just now, RXP said:

It is common for antivirus to report false positives with our files, only because they are protected with specific 'protection' technologies. They also embed a 'taggant' which is s technology agreed upon by A/V vendors and protection vendors, so as to not flag false positives since the file can be traced back, nevertheless, some A/V vendors fail miserably.

ok

Gregg Seipp

"A good landing is when you can walk away from the airplane.  A great landing is when you can reuse it."
i7-8700 32GB Ram, GTX-1070 8 Gig RAM

Posted

OK. Let's see how well I can write this. Am up in the Real Air Turbine Duke v2 (TDv2). Am at 20,000 feet (29.92).  Pointing at the airspeed indicator in the TDv2 provides a tooltip showing both IAS and TAS.  My IAS is 201 kts and TAS shown as 266 kts.  Pointing the mouse pointer at the TDv2 outside temperature gauge shows OAT of -29°C/-21°F.  

The RXP GTN750 is showing 219 kts ground speed. Winds at 48 kts.  My autopilot guided flight plan has vectored me around the Washington, DC protected airspace so I have been at various headings so far into my flight. My GTN indicated wind speed has changed several times. However the wind direction arrow has not changed at all. 

I am flying with a real world flight plan created at FltPlan.com and flying with weather infusion from FS Global Real Weather (FSGRW).  My FSX/FSGRW departure weather at Easton was spot on with my FltPlan.com flight plan. My GTN indicated winds aloft have been in very close proximity to my flight plan.

I believe my GTN indicated ground speed is off and I may have determined why.  The GTN Map's User Fields (via Menu) include an option to show Outside Temperature (OAT).  It is indicating -20°C.  The OAT gauge in the TDv2 is as stated above showing -29°C/-20°F.  So the GTN may be using the °F instead of the °C.  Pulled out my trusty Sporty's electronic E6B calculator and calculated TAS from Pressure Altitude (20,000), Calibrated Airspeed (CAS or IAS), and OAT. I did this for the TDv2 °C reading of -29°C and for the GTN °C reading of -20°C and the differences in the two results, after subtracting the GTN indicated wind speed accounts for the difference.  Yes, I used the indicated wind speed and did not convert it to true component vs my heading, but I did if the same for both the TDv2 and GTN OAT °C readings. The wind component would be the same for both.

I did not get a chance to time any FSX enroute segments vs my plan to determie as my FSX just crashed, likely due to all my messing around and Alt-Tab's between other applications.  

In closing, my GTN wind direction arrow did not at any point change, and it may be that the GTN is using a °F reading for OAT instead of °C, which if true places TAS and thus GS off by a handful of knots.  Perhaps 6 to 8 in the case of my flight.

Frank Patton
Corsair 5000D Airflow Case; MSI B650 Tomahawk MOB; Ryzen 7 7800 X3D CPU; ASUS RTX 4080 Super; 
NZXT 360mm liquid cooler; Corsair Vengeance 64GB DDR5 4800 MHz RAM; RMX850X Gold PSU;; ASUS VG289 4K 27" Display; Honeycomb Alpha & Bravo, Crosswind 3's w/dampener.  
Former USAF meteorologist & ground weather school instructor. AOPA Member #07379126
                       
"I will never put my name on a product that does not have in it the best that is in me." - John Deere

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