Unusually poor glide ratio

[arneh]

I encountered something strange during last night's SBC race, I was getting significantly worse glide ratio than the other gliders I were flying with. Most notable on the incredibly long final glide. On the final leg I turned final turnpoint together with MX, and being at almost the same height (me slightly higher), and at the time the final glide computer claimed I would reach finish at +100 m. Then we kept the same speed for the entire glide, but I kept losing height compared to MX continuously, despite us both following much the same track. By the time I got to the final hills I was 300 m below him (-200 to make finish), and unable to get over the final hills. I then had to follow the ridge sideways for quite a bit, until I finally found a thermal.

And the stats seem to confirm that I was getting notably worse glide ratios the entire task (or having to fly much slower to get the same ratio). On the first leg which was almost just thermals, and where I was flying together with MX and 8K, as you can see below I was getting on average 13 less glide ratio than 8K despite flying 8 kph slower on average. Glide ratio was about the same as MX, but he as going on average 11 kph faster.

And for the final glide we were getting about the same glide ratio (mine inflated somewhat by about 20 km of ridge flying), but I was doing just 135 kph average in my attempt to at all make it, while they were going much faster at 170 and 156 kph.

glideratio.png

The obvious explanation would be that I flew with the gear or brakes out, but I tested extending and retracting both of those to make sure I really had them retracted, so I don't think that is the problem. And I was using the correct flap setting (0), at least as far as the speed indicator seems to tell me is correct. I and 8K were flying Nimbus, while MX flew ASW 22. I was full water the entire task, except for the very last thermal to get me over the last ridge.

Anyone have any idea what could be my problem? Am I attracting all the bugs to my wings, while everyone else flies clean?

[EDB]

I haven't compared glide ratios to others yet, but I have been guessing what happened to me yesterday also.
I had the same problem. It felt like continuous extra sink on the final leg. When flying sollfahrt I had IAS too high compared to block-speed and was getting under flightpath constantly. I now thought that it might have been the spoilers that where out of the lock, but I doubt it.

You were in front of me before the last TP. I was grounded just before the finish sector when I saw you finishing, so we were on the last leg in the same time window on the same server. I was on FG when leaving the mountains. But had to thermal halfway to get back on FG, but eventually didn't make it...

If you look at my FG in the barogram you can see it is not a straight line. I constantly had to fly slower and slower. I had to stop using sollfahrt :
http://www.condor-club.eu/analysis/0/?res=79638

This can happen in real life. A big area with sink. But this is new for me in Condor...

[EDB]

To Rheinfelden EDTR (Final Glide)

EDB started higher, so a higher FG Mc (slightly lower mGN) and a higher speed is to be expected...

Glider: 8K, AXM, EDB
mGN: 45,1 43,09 38,47
mIAS: 170,06 139,69 146,03

Missing 30kph on average... That's a lot...

[Spirals]

Hi

Very interesting comments, especially as my experience was just the opposite, and to me equally confusing during the long final glide along the whole of the third leg.

I left the 2nd turn at 9,250 feet (ASW22 full water and no bug wipers fitted) and if I remember correctly the MC had me at around 3.5kts with no safety margin and although I was flying as accurately as possible to this and certainly not knowingly slower and only managed a few pull ups under clouds on track I did notice that I was slightly gaining height against the final glide and was able to keep tweaking the MC up.

Towards the end it was up above 5 knots and over the last obstacle it was above that. It is not obvious from studying it on See You that the Gsp was higher towards the end but I did have a lot of time to consider what was happening and toyed with the idea that the flight computer wasn't taking into account the downwind component - it must have been taking it into account but that was the only thing I could come up with at the time.

Perhaps the slowing down for the occasional dolphin would have helped but surely not that noticeably with such a long glide and the small number and only weak lift involved.

My own and 8K's final glider look almost identical (Nim4 v ASW22) - I've not found a way of synchronising the See You animation to be from the 2nd turn point which would be more interesting for all 4 flight tracks.

Steve

[EDB]

You can sync in See You on the Finish Time to compare FG.

[Freebird]

I have experienced this before, also with open class when gliding with others you have a noticeably inferior glide angle & when following an identical glider at the same height on FG end up lowering MC constantly to get home while watching the other glider disappear into the distance. Not sure why it happens but it does occasionally happen in reverse where you constantly raise MC on FG as you seem to gain more than you should.

[EDB]

The glider in front of us is creating big vortices...
So next time be the first that goes on FG... All gliders behind you will be 30kph slower..!

First Image source : Olivier Cleynen

[Spirals]

Hi EDB

I had synchronised to the finish time but you and AXM took roundabout routes so I was hoping to sync to the turning of TP2 for a closer comparison of the final glides - not found a way of doing that on See You (I was hoping that you could sync to TP2 or work out the time offset and then manipulate the playing of the tracks so that they coincided at that point within 'Custom').

I understand what you are saying about the turbulence from machines ahead and obviously the tugs have prop wash in Condor but have the brilliant individuals that produced Condor gone to the trouble of programming in complex and hidden effects, such as glider wakes, into Condor itself?

I'm sure though that I recall a famous German glider pilot (not positive which one) saying that you could use the wake effect to your advantage in the following glider if you positioned yourself correctly - maybe it was just anecdotal.

I recall in a K6E on an incredibly calm day/evening flying in smooth circles in still air and coming across what I was sure was the glider's own wake from the previous circle - quite eerie (and unusual for my circling to be that precise).

If they have programmed in the wake effect then looking at the overall scores we need two volunteers a week to offer to park themselves ahead of AXM on all the final glides and hope that he does not find the advantagous position!

Steve

[EDB]

I'm using an older version of SeeYou and can not sync on specific points and don't think newer versions can. But I normally use the finish time for FG comparison. You can however check glides between thermals in the flight parameters.

My post about the wake was just a joke. I don't think Condor is simulating this. Condor also doesn't simulate area rise and sink. That's why I don't understand what happened on the last FG. Did all the gliders with this problem fly through invisible dying cloud-streets constantly..? I don't think so. Condor doesn't simulate cloud-streets.

If you position yourself to the side and a bit behind the leading glider, you can gain from the vortices in real life. You can see it in the pictures above. The vortices create lift to the left and right of the aircraft. You just have to look at how birds do formation flying... in the V formation...
But with a glider this affect only helps you a few meters, because when you rise above the vortex, the effect is gone.

I have been comparing the FG values of some flights to the Condor polar and I'm now more questioning the faster flights then the slower flights that had strange sink problems... The slower flights are closer to the Condor polar then the faster flights...
I still don't understand the sollfahrt values I got. Maybe I try to check the Condor polar for anomalies when I have time.

[OXO]

I believe you are correct that condor doesn't simulate those effects.

I think it does simulate the effect of g load changes though. maybe if you were doing pullups in lift on fg, then this would give you the difference.

[EDB]

I had to do one or two pull-ups trying to get back on FG and to compensate for the sink in the outer ring of a thermal. A pull-up reduces your FG speed yes. And if you do this to aggressive you can put it into a high speed stall... But that doesn't explain the continuous sink and sollfahrt sink indications in glide mode (a higher speed-to-fly then expected).

I was also thinking of CoG. With an aft CoG you have to trim forward when on FG. This will create more lift and drag on the horizontal stabilizer.
I'm leaving MX out of the comparison, because he was flying an ASW22 with a different speed polar. These gliders were Nimbus 4 :
8K CoG 0
AXM CoG -3
EDB CoG -4

But as far as I know (from Tim K) this is also not simulated in Condor. Or is it..? If it is, the influence on FG in Condor is huge. Like dropping an anchor..
Because I never seen this behaviour earlier, I don't think it is.

I really had hoped that you would have told us that last Sunday the SBC team was using Condor V2 test-servers with a macro weather model. Servers that were compatible with Condor V1 clients...

(Fingers crossed that Olympia doesn't read this...)

[wickid]

Might it be related to ping times? Maybe lag causes condor to miscalculate the sinkrate.

[EDB]

Personally I think that sinkrate is calculated on the client side. And that glider position is reported to the server. And that the files for these calculations on the client side are checked by the server to prevent cheating. But I might be wrong...

[arneh]

I think it does simulate the effect of g load changes though. maybe if you were doing pullups in lift on fg, then this would give you the difference.

I usually do some pullups if flying through thermals on glide, but if anything I was making fewer than normal pullups, simply because there weren't many thermals left at this point. And from observing the calculated arrival height I do see that the pullups usually give me 20-50 m more margin, so I'm gaining energy, not losing it. While during normal glide towards a turnpoint/finish the calculated arrival height will remain more or less static (as it should in still air).

In this flight the calculated arrival height was continuously decreasing during the entire glide, decreasing at what seemed like a constant rate the entire time.

[arneh]

I was also thinking of CoG. With an aft CoG you have to trim forward when on FG. This will create more lift and drag on the horizontal stabilizer.
I'm leaving MX out of the comparison, because he was flying an ASW22 with a different speed polar. These gliders were Nimbus 4 :
8K CoG 0
AXM CoG -3
EDB CoG -4

In real life a more rearward CG (negative value in Condor) will give less drag. But as you mentioned, I don't think this is modeled i nCondor.