hawx2k

777 ground friction changes in P3D v4?

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Good morning,

I just flew the 777 for the first time in P3D v4 and noticed a significantly increased ground friction (in FlyTampa Dubai). Without (constant) significant thrust (N1 >28%) the plane would stop taxiing after a short while (within 10-15 seconds). I'm not sure if I have done something wrong or if this is an intentional change (I'm not flying a T7 in real life, so couldn't tell :D).

Thanks for any insight.

Jan

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Fsuipc has a section that handles friction. I forget how it works but Google should help 

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Don't forget that this is an entirely new simulator, and it does not take your old calibrations into effect. You will need to re-set your calibrations, null zones, and so on in the new sim to ensure that you are not dragging your brakes.

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Thanks all.

1) I don't use the paid FSUIPC version (yet) - hence there is no friction control I could have accidentally enabled

2) based on Kyle's input I re-calibrated the rudder pedals (Saitek Pro) and even increased the null zones to over 50 which for sure would loosen the brakes -> to no avail. Also, in the 747, the same setup - no change in calibration - works like a charme. The aircraft keeps rolling even in idle thrust. With the 777 I need north of 28% N1 to keep it rolling. I don't think that's normal. What else can it be?

3) Same behavior in P3D v3 (where I'm actually using FSUIPC for the axis assignment and calibration). 

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Same situation even though I install the latest update only in v3: I need 2% more thrust to keep the 777 moving.

I also noticed that some videos in Youtube about the 777 in v4 also encounter this problem, that the aircraft slows down quickly when N1 is below 24%.

 

Yunchong

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Am I right to assume that ground friction is currently not working in FSUIPC5?

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It's not caused by any old axis settings dragging brakes. 

Ground friction changed in v4 but something's off with triple 7 as it simply won't move and feels horribly sluggish. I remember that the engines in v3 were powerful enough that even when almost  idle it already moved (which I found quite realistic). Now it's just glued to ground and slows down quickly. Plus you can't reverse with reverse thrust (so something's definitely off with physics). 

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19 hours ago, Mephic said:

It's not caused by any old axis settings dragging brakes. 

Ground friction changed in v4 but something's off with triple 7 as it simply won't move and feels horribly sluggish. I remember that the engines in v3 were powerful enough that even when almost  idle it already moved (which I found quite realistic). Now it's just glued to ground and slows down quickly. Plus you can't reverse with reverse thrust (so something's definitely off with physics). 

Just ran a test.

Empty plane, Short fuel, 30.0% thrust (N1), clear weather, JYO 35, 16JUN17 at 10:00. Pop the parking brake and you hit 58 knots by the runway end.

Fun factoid from that test: v3, end of runway at 58 knots; v4, end of runway at 58 knots.

...but no, you're right. The 777's compatibility-only update (i.e. no behavioral code changes) is causing some sort of fundamental change in friction, and it is not being caused by improper hardware setup.

 

Of all of the people reading this, which would you prefer:

Potentially solve your problems by chasing down actual issues with your hardware setup, or chase ghosts and blame code?

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You  said at Fly Tampa Dubai.

Does this apply elsewhere?

if no could it be one of those problems of a part of Fly Tampa being compiled in an earlier version as RR has indicated this may cause problems?

 

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15 hours ago, scandinavian13 said:

Just ran a test.

Empty plane, Short fuel, 30.0% thrust (N1), clear weather, JYO 35, 16JUN17 at 10:00. Pop the parking brake and you hit 58 knots by the runway end.

Fun factoid from that test: v3, end of runway at 58 knots; v4, end of runway at 58 knots.

...but no, you're right. The 777's compatibility-only update (i.e. no behavioral code changes) is causing some sort of fundamental change in friction, and it is not being caused by improper hardware setup.

 

Of all of the people reading this, which would you prefer:

Potentially solve your problems by chasing down actual issues with your hardware setup, or chase ghosts and blame code?

Issue is not there with other aircrafts. 

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16 hours ago, scandinavian13 said:

Just ran a test.

Empty plane, Short fuel, 30.0% thrust (N1), clear weather, JYO 35, 16JUN17 at 10:00. Pop the parking brake and you hit 58 knots by the runway end.

Fun factoid from that test: v3, end of runway at 58 knots; v4, end of runway at 58 knots.

...but no, you're right. The 777's compatibility-only update (i.e. no behavioral code changes) is causing some sort of fundamental change in friction, and it is not being caused by improper hardware setup.

 

Of all of the people reading this, which would you prefer:

Potentially solve your problems by chasing down actual issues with your hardware setup, or chase ghosts and blame code?

Kyle,

have you even read what I posted a few posts above the one you were replying to:

1) I don't use the paid FSUIPC version (yet) - hence there is no friction control I could have accidentally enabled

2) based on Kyle's input I re-calibrated the rudder pedals (Saitek Pro) and even increased the null zones to over 50 which for sure would loosen the brakes -> to no avail. Also, in the 747, the same setup - no change in calibration - works like a charme. The aircraft keeps rolling even in idle thrust. With the 777 I need north of 28% N1 to keep it rolling. I don't think that's normal. What else can it be?

3) Same behavior in P3D v3 (where I'm actually using FSUIPC for the axis assignment and calibration). 

I think I had done the part you refer to as "chasing down actual issues with your hardware setup" and no where I can see I was chasing ghosts or blamed code?

What I'm missing in your test altogether BTW is what we had claimed to be the issue to begin with: the plane will stop when reducing to idle thrust almost immediately (within 10-15 seconds). I already said that you can keep the plane rolling with N1 of 28%. So I even believe your "test". The only problem is, it doesn't address our issue at all. 

Edit: In an effort to be diligent I tried replicating your test with a twist: disconnected and disabled all external hardware control input and ran your test twice (with external controls enabled and disabled). Result: in both cases I reached 38 kts at the end of the runway (10,000ft - KCLT 36C) with N1 30% thrust. Going to idle thrust: in both cases the plane stopped within 15 seconds (from 30kts). 

Would appreciate a serious answer/attempt to help and considering input by customers rather diligently and not dismissing it before even reading it. 

Jan

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15 hours ago, harrry said:

You  said at Fly Tampa Dubai.

Does this apply elsewhere?

if no could it be one of those problems of a part of Fly Tampa being compiled in an earlier version as RR has indicated this may cause problems?

 

It's happening on other airports as well: Tested so far: OMDB, LOWW, KCLT, KDEN. The latter two are supposedly fully v4 compatible. OMDB and LOWW at least have v4 compatible patches. But the spread across four airports and three developers at least suggest some coherence although it probably is still no scientifically significant sample size :).

P.S. forgive my slight irony, but Kyle's response just tripped me off on the wrong foot.

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Hi,

To compare the incomparable (:laugh:), in fsx I couldn't taxi the T7 at idle thrust except when fully empty with minimum fuel.

25-30% was something I was used to use for normal ops to taxi the T7 before I started to use the dynamic friction LUA of Fsuipc4.

If I recall well the friction model has been improved on the QOTS II (and that it would be updated on the T7 (?) when upgrading it with the progresses made with the QOTS II)

Actually there was already a difference in ground friction in FSX between the T7 and the QOTS II. I used the LUA dynamic friction for the T7 and not for the QOTSII.

It seems to be exactly the same in P3D v4. Not better not worst. The "grip" of the T7 feels the same.

But maybe I'm a lucky one because I have also none of the brake issues. I did a profile in fsuipc 5 from scratch for both aircrafts and recalibrated all my hardware in the P3D v4 controls.

I'm still missing the Lua dynamic friction for the T7 in P3D v4 as I used it in FSX but without it it feels the same in both sims FSX and P3D.

 

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I did a full recalibration and wiped out all of key binds to ensure there is no conflicts and issue is still there. Aircraft stops very quickly instead of rolling or slowly slowing down like in v3. 

 

LM stated that they modified friction parameters in v4 if I recall. Maybe adjustments are needed?  I also want to have the issue solved but blaming our hardware where it's clearly not the issue is simply not fair approach and not what I expect as customer which I am spending couple of hundred bucks for PMDG addons. 

I always support PMDG so I don't think it's too much to expect same in return. 

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Just now, Budbud said:

I'm still missing the Lua dynamic friction for the T7 in P3D v4 as I used it in FSX but without it it feels the same in both sims FSX and P3D.

Is the dynamic friction feature not yet included in FSUIPC5?

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2 hours ago, Budbud said:

Hi,

Yes it is but I understood from Pete Dawson's post here that it is doesn't work in P3D v4 so I didn't even try it.

http://forum.simflight.com/topic/83542-p3dv4-ground-friction/?do=findComment&comment=505020

Maybe I'm wrong and it's worth testing it. I'm beta testing another software for now so I don't have much time to perform tests for myself.

 

I just hope there won't be friction issues with the NGX when it's avialable...

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Any issues you have with "friction" or more accurately rolling resistance with the B77L in P3Dv4 is due to your configuration.  I just checked, out of curiosity, and with a 728.8 klb GW she easily breaks away with as little as 28%N1 and 27%N1 will get you to 10-15 kts and continue to accelerate for as long as you have pavement, which in my short test was 19 kts at the 8000 ft marker at KLAX.  This doesn't seem like an "issue."

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6 hours ago, downscc said:

Any issues you have with "friction" or more accurately rolling resistance with the B77L in P3Dv4 is due to your configuration.  I just checked, out of curiosity, and with a 728.8 klb GW she easily breaks away with as little as 28%N1 and 27%N1 will get you to 10-15 kts and continue to accelerate for as long as you have pavement, which in my short test was 19 kts at the 8000 ft marker at KLAX.  This doesn't seem like an "issue."

The thing is, I can achieve the same result with only 25% or 26% of N1 in previous versions. And with the LUA enable, same thing can be done with even 24% N1. 

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On 6/15/2017 at 2:47 PM, hawx2k said:

Good morning,

I just flew the 777 for the first time in P3D v4 and noticed a significantly increased ground friction (in FlyTampa Dubai). Without (constant) significant thrust (N1 >28%) the plane would stop taxiing after a short while (within 10-15 seconds). I'm not sure if I have done something wrong or if this is an intentional change (I'm not flying a T7 in real life, so couldn't tell :D).

Thanks for any insight.

Jan

 

Just a bit of sharing of what the real airplane feels like.

Taxiing the real 773ER (772LR would be similar and probably worse if light) would be like driving a car with conventional automatic transmission with a torque converter, anything below 300tons the airplane will break away at idle thrust albeit very slowly.

Then after the airplane gets up to about 5-6kts it will accelerate a bit faster with idle thrust when taxiing on a completely flat taxiways. And you will need to use the brake to control your speed. Otherwise it will keep accelerating. 

The normal practice when taxiing on a long straight taxiway is to let the airplane accelerate to ~30kts then applies the brakes smoothly to slow down around 15kts and then let it accelerate again. Repeat the same process units you reach the runway holding point or the ramp/apron area. 

Usually it is normal for guys to push the thrust up to about 28%-30% N1 to get it rolling initially especially when a 90deg turn is required shortly after, because the airplane slows very quickly in turn so it is normal to keep the thrust at around 25% N1 to prevent the speed from decreasing when in a turn. Even on an upslope taxiway at MTOW, 35% -38% N1 of break away thrust is all you need. 

anything below 250tons on the 773ER the airplane would be accelerate even if one engine running only (we shut down one normally after landing to save fuel nowadays after a cooling period of 3 min when workload and airport facility permits) 

To be very honest even in the Level D simulator which the pilots use for their training and check, the ground fiction model is never correct, because  it is hard thing to model.

And this is one of the reason why simulator landing is not "quite real" as well, and there are companies which provide an "add on" algorithm to level D which aims to fine tune it. 

Even the landing distance performance on the PMDG 777 was not correct either, and basically what you get when you use Autobrake 2 in P3D/FSX at Groundspeed of ~150-155kts will roughly give you a Autobrake 4 stopping distance in real life which is about ~1900m-2000m (6200-6400ft). May be it is my own problem but it is completely fine to me, I did not use any FSUIPC software, the only thing aircraft add on is pmdg 777 on my computer. 

other than that, the overall simulation experience is quite good.

Hopefully you can fine tune your fiction and bring the thrust down a bit in order to maintain your Taxi speed. 

Have a good weekend gents. 

 

 

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I haven't really noticed any issues with the 777 but one thing I don't understand... When reading through this thread, there seems to be an unwillingness of helping to identify the underlying problem and more of a confrontational attitude of those experiencing it, in order to promote an agenda which goes to discredit the support given from PMDG and the product.

Oh, well... Gents, how about trying the following:

  1. Disconnect ALL hardware from your computer. And I do mean ALL. Everything till you end up with having a keyboard and mouse connected.
  2. Duplicate Kyle's scenario found here.
  3. Let us know what results you get.

Start with the most basic setup and work your way from there. Default airport. Everything disconnected etc. If there's no problems when doing this, we can eliminate that the 777 is to blame. If not - well, then maybe we could be one step closer to identifying it... 

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Thanks Anders.

I'll just ignore the insinuation and assume that the fact that you seem to ignore all my previous posts that attempted to replicate what Kyle had suggested is a mere oversight and get to the point:

- re-ran the test as I already did per:

- this time indeed with an empty plane and short fuel (in my initial test I had admittedly full fuel and standard payload which of course should naturally increase friction) and default airport (P3D default Eglin AFB, RW19)

1. as before I disconnected all hardware except mouse and keyboard: set N1 to approx. 30%; the plane accelerated faster than in my initial test which is normal because the plane is lighter (got to about 40kts by half the runway), then reduced to thrust idle; plane decelerated moderately but noticeably to about 20 kts within 10 seconds and would come to a standstill after about 20 seconds.

2. re-connected all external hardware (HOTAS joystick and throttle, Saitek pedals) and re-ran the above test: the exact same result. There is no difference.

This pretty much replicates what Kyle @scandinavian13 had found (as I had already stated in my previous post) and rules out any external hardware mis-calibration or other issues with the hardware setup. So I think we are at jeopardy of agreeing violently that we get the same results in our tests (albeit Kyle didn't test the deceleration part), but we seem to disagree on the conclusion: is this the correct behavior and had it changed to previous 777 versions? 

@Driverab330 seems to suggest it is not the real thing:

I for sure can't tell since I'm not a RL pilot.

The only thing I can say is that I remain committed to resolving the issue (if it is one) and hope PMDG support can do the same (as I am used to it does) and we can leave the somewhat controversial attitudes behind us and stick to the facts.

Thanks,

Jan

 

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Going  to add my 2  cents  in this  topic, users  expect   the  sim to behave   as per  the  rw  aircraft its not  going  to happen you will always  have  different  variables  in play   so  as  Driverab330  has  stated  in his  post above  said  the  overhaul  simulation is  good

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Ignoring all pointless accusations, I've disconnected the Saitek Yoke, rudder pedals and both of my Throttle sets and repeated Kyle's test adding also decceleration part where the actual problem is and result is exactly the same, plane stops itself much quicker than in v3, with or without hardware connected.

Since LM changed their ground friction model between v3 and v4 I believe some adjustments had to be made, but obviously I might be wrong as I'm not developing this aircraft. 

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