LX7007 speed-to-fly problem, revisited ...

I had a pair of seemingly disjoint flight data problems through Saturday and I’m curious whether their absence on Sunday had them connected in some way.

My setup: LX7007 Pro IGC (ver 2.01) providing NMEA and LXWP* sentences to an Oudie (SeeYou Mobile, latest version). I use the LX for general task and flight direction including speed commanding, and the Oudie for birds-eye situational awareness (landing options) and second opinion on final glide data. (The Oudie is new this year, replacing my old hx4705 that also ran SYM.)

Problem One: the LX’s speed commander hadn’t worked in a long time. (Hard to pinpoint when since I’ve flown so little since summer 2010.) I recently had the LX’s firmware upgraded from 1.2 to 2.01 hoping that would fix the problem. It didn’t. The speed director would always tell me to fly slower, no matter how slow I was flying. It would only suggest faster (err, less slower) speeds if I upped the McCready to high settings ( 4).

Problem Two: the Oudie’s altitude display was way off, even though I set it to the field elevation in the Settings page before launch. During the flight it would read up to several thousand feet different than the analog instrument or the LX’s. This was giving me incorrect arrival altitudes on the Oudie, thus rendering it nearly useless as a situational awareness tool.

Saturday evening while discussing the problem with N7, he suggested, wrt Problem One, it might be a polar data problem in the LX. This reminded me that sometime in the last two years I switched from using my own calculated polar coefficients (for ASG-29/15) to simply using the ASW-27 selection in the LX’s polar list. So Sunday morning I reinstated the polar data numbers I used from 2008 to ~2011, and made the same change to the Oudie’s polar setting.

Sunday’s flight saw BOTH problems disappear.

Coincidence? I’m concerned about Problem Two happening again, and how it might be fixed in flight.

Regardless … sure was nice to finish my first AST in nearly two years, even if I was slower than N7’s tortoise (http://www.youtube.com/watch?v=fTpgqgfJs4w).

~ted/2NO

ps I suppose if Problem Two happens again I can tell it to use internal GPS instead of LX data, but I hate to lose the air data in SYM ...

How is your cruise / climb set up? Switch or airspeed? Maybe the airspeed is set too high, but this wouldn't explain the problem of randomness. Have you checked what ASI readings the LX is getting? You could have a leak somewhere...

On Monday, April 22, 2013 12:24:12 PM UTC-4, 2NO wrote:
I had a pair of seemingly disjoint flight data problems through Saturday and I’m curious whether their absence on Sunday had them connected in some way.



My setup: LX7007 Pro IGC (ver 2.01) providing NMEA and LXWP* sentences to an Oudie (SeeYou Mobile, latest version). I use the LX for general task and flight direction including speed commanding, and the Oudie for birds-eye situational awareness (landing options) and second opinion on final glide data. (The Oudie is new this year, replacing my old hx4705 that also ran SYM..)



Problem One: the LX’s speed commander hadn’t worked in a long time. (Hard to pinpoint when since I’ve flown so little since summer 2010.) I recently had the LX’s firmware upgraded from 1.2 to 2.01 hoping that would fix the problem. It didn’t. The speed director would always tell me to fly slower, no matter how slow I was flying. It would only suggest faster (err, less slower) speeds if I upped the McCready to high settings ( 4).



Problem Two: the Oudie’s altitude display was way off, even though I set it to the field elevation in the Settings page before launch. During the flight it would read up to several thousand feet different than the analog instrument or the LX’s. This was giving me incorrect arrival altitudes on the Oudie, thus rendering it nearly useless as a situational awareness tool.



Saturday evening while discussing the problem with N7, he suggested, wrt Problem One, it might be a polar data problem in the LX. This reminded me that sometime in the last two years I switched from using my own calculated polar coefficients (for ASG-29/15) to simply using the ASW-27 selection in the LX’s polar list. So Sunday morning I reinstated the polar data numbers I used from 2008 to ~2011, and made the same change to the Oudie’s polar setting.



Sunday’s flight saw BOTH problems disappear.



Coincidence? I’m concerned about Problem Two happening again, and how it might be fixed in flight.



Regardless … sure was nice to finish my first AST in nearly two years, even if I was slower than N7’s tortoise (http://www.youtube.com/watch?v=fTpgqgfJs4w).



~ted/2NO



ps I suppose if Problem Two happens again I can tell it to use internal GPS instead of LX data, but I hate to lose the air data in SYM ...

I use a switch on my flap handle, so the unit is in climb mode when the flap is in position 5 or higher.

I checked the p-tot using a simple blow test but nothing more sophisticated..

Alas I cannot find a way to view the IAS on the LX. An option I guess it to turn on the LX's IAS (logging) sentence and compare it to observations.

Another problem I'm having with the LX that could possibly be related is that when on the ground, the LX always thinks it's in flight, which makes it impossible to change certain settings or to transfer a flight log. That would happen, I think, if it is getting an indicated airspeed.

Pure speculation, but I think the IAS could be the issue. I'm pretty sure there is a way to get this as one of the readouts on your vario (upper or lower number). At least it is on the new color screens coming as an option with refurbed LX7007 units like one I just purchased. You may be able to just buy a new screen, which might seem like overkill, but I do prefer the stepper motor and color indicators an improvement on the old LCD variety readouts, especially having a needle moving instead of LCD indicators coming on and off.

2C

On Monday, April 22, 2013 7:49:16 PM UTC-4, 2NO wrote:
I use a switch on my flap handle, so the unit is in climb mode when the flap is in position 5 or higher.



I checked the p-tot using a simple blow test but nothing more sophisticated.



Alas I cannot find a way to view the IAS on the LX. An option I guess it to turn on the LX's IAS (logging) sentence and compare it to observations.



Another problem I'm having with the LX that could possibly be related is that when on the ground, the LX always thinks it's in flight, which makes it impossible to change certain settings or to transfer a flight log. That would happen, I think, if it is getting an indicated airspeed.

I've been through the v2.0 manual from top to bottom and the only mention of IAS is in the list of logging sentences that can be enabled. It is definitely not one of the options on either of the LCD lines (unless my actual 2.01 firmware differs from the user manual). I've sent an email to support at LX and hoping to hear from them about how to read IAS.

In our club Duo Discus we have an LX7007 installed which also seems to show similar problems. Speed to fly always seems to be too low. I have not looked into it in detail, but maybe it actually is an LX7000 specific problem.

On my most recent flight (24 Apr) I seemed to solve the speed commanding issue by specifying a different polar instead of the built-in ASW-27. We'll see whether the issue returns.

The second issue was gone on Sunday as well ...

Well I have two seemingly disjoint problems, but they are definitely related: (1) my LX gets stuck in "in flight" mode, and (2) the speed commanding is b0rken.

Both are almost certainly related to the LX's IAS reading (or TAS calculation) being stuck. When my speed command stopped working in flight on Sunday I set the LCD indicator to show SPEED (TAS), and it was stuck on 102. At other times in the flight it was stuck on other values (usually high values, above 90) -- but stuck.

Waiting to hear from the factory on this but if anyone has any experience with unsticking a stuck IAS/TAS in an LX, I'm all ears.

(I'm pretty sure this is not a plumbing issue ... if it was, I seriously doubt the indicated value would be constant.)

tuno

On Sunday, April 28, 2013 9:11:20 PM UTC-4, 2NO wrote:
Well I have two seemingly disjoint problems, but they are definitely related: (1) my LX gets stuck in "in flight" mode, and (2) the speed commanding is b0rken.



Both are almost certainly related to the LX's IAS reading (or TAS calculation) being stuck. When my speed command stopped working in flight on Sunday I set the LCD indicator to show SPEED (TAS), and it was stuck on 102. At other times in the flight it was stuck on other values (usually high values, above 90) -- but stuck.



Waiting to hear from the factory on this but if anyone has any experience with unsticking a stuck IAS/TAS in an LX, I'm all ears.



(I'm pretty sure this is not a plumbing issue ... if it was, I seriously doubt the indicated value would be constant.)



tuno

Well, it was a different device (LX160) but I saw the same thing a while back.
It turned out the connector on the back of the vario was a little loose, and
the unit took that to indicate that my climb/cruise switch was in the cruise
setting (I didn't actually HAVE a switch!). My fix was to switch to a different
brand of vario!

Matt

If you are sure it's not the plumbing then it has to be the device, more accurately the pressure sensor for TAS. You probably can't replace it yourself so you'll have to send the LX to whoever does repairs in the US.