Single Engine Taxi impossible

Driver170
Posts: 3463
Joined: 29 Feb 2016, 02:22
Location: Edinburgh

Re: Single Engine Taxi impossible

Post by Driver170 »

Lapi wrote: 18 Jun 2020, 21:42
Driver170 wrote: 18 Jun 2020, 10:35 Based on a Captain at Jet2 he said when they do single engine taxi after landing is about 40-50%
That's perfectly fine. I mentioned the N1 to get the A/C moving and not the taxi phase.
But also Lapi with P3D poor friction model this also decreases the spees very quickly when you close the thrust levera to ground idle.
P3D's friction is not at all poor, not too good either, it is a bit too dependent on the surface type and seasons, but more or less can be circumvented in the flight-model.

regards
Lapi
So how is this flight model co-efficient during braking on wet or contaminated runway vs dry
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Piddy
Posts: 63
Joined: 29 Oct 2019, 17:16
Location: EDDL

Re: Single Engine Taxi impossible

Post by Piddy »

Hi all.

to pick up this topic again.....

Single engine taxi is still not possible satisfactorily as thrustsetting is too high until A/C moves and during taxi. So A/C cannot be taxied on yellow lines as thrust giers the bus to opposite side of running engine. Flight must be finished on runway unfortunately and not a any gate.

It does not matter wether the rwy is dry or wet.

Any other Idea?

Peter
Mangal
Posts: 3
Joined: 24 Apr 2021, 14:23
Location: Berlin

Re: Single Engine Taxi impossible

Post by Mangal »

I can confirm that SE taxi is not realistic / possible.
But I assume this is one the limitiations that we have to accept in P3D as the core simulator.
I think here are already a lot of features of Prosim programmed "around the Sim" in order to increase realiam,
but that's limited.
Maybe. Just my 2cents
Tim
Posts: 65
Joined: 05 Apr 2021, 11:23
Location: Belgium

Re: Single Engine Taxi impossible

Post by Tim »

Lapi wrote: 18 Jun 2020, 09:37
Driver170 wrote: 18 Jun 2020, 09:13 Also get this with the 737.
No, you do not.
A 60T GW A/C with average W&B at ISA on normal surfaces needs approximately 30-32% N1 to get it moving, then thrust can instantly be reduced and it will move with 26-28% N1 at 15 kts or so.
If only one engine is running, you obviously need to double the figures above (without mentioning asymmetric thrust) so to get it moving at 60%N1 is absolutely fine.

regards
Lapi
Hi Lapis,

I understand your logic but thrust is not linear.

With your logic, an aircraft flying at up speed with 60% N1 would need 120% N1 on single engine. That would make single engine flight impossible. Where in fact, 70% N1 is sufficient to maintain up speed (+10% N1).

The logic is the same for the taxi. Although you need a lot of thrust to start the movement on single engine (about 40% for 60 tons but will change according to taxiway slope). This is why single engine is only recommended when no stopping is expected.

Once rolling, thrust setting is pretty low. Somewhere between idle and 30% N1.

I do understand that different simulator logic/friction value etc makes the development very difficult for you guys. I see the same difficulties when taxiing on single engine using other 737 addons.

Cheers

Tim
Piddy
Posts: 63
Joined: 29 Oct 2019, 17:16
Location: EDDL

Re: Single Engine Taxi impossible

Post by Piddy »

That´s it exactly.
In Prosim you need a constant SE taxi thrust of around 55-60%, even AC is rolling. Lower Thrustsettings lead to taxispeed decrease.
In real life Once rolling 30% thrust on one engine is enough to keep AC taxiing.
Best regards. :)
Lapi
Posts: 3037
Joined: 26 Nov 2011, 02:00

Re: Single Engine Taxi impossible

Post by Lapi »

Tim wrote: 09 May 2021, 08:20 Hi Lapis, I understand your logic but thrust is not linear.
With your logic, an aircraft flying at up speed with 60% N1 would need 120% N1 on single engine. That would make single engine flight impossible. Where in fact, 70% N1 is sufficient to maintain up speed (+10% N1).
Hello Tim,

Lapi, not Lapis. Otherwise it's kind of you picking a ten months old sentence of mine.
Yes, thrust is not linear, and the reaction was related to get the A/C moving in the sim by a given GW and not single engine flight, as you try to state.
The logic is the same for the taxi. Although you need a lot of thrust to start the movement on single engine (about 40% for 60 tons but will change according to taxiway slope). This is why single engine is only recommended when no stopping is expected.
The logic is definitely not the same for taxi, so when you mention theoretical values in flight, is not related to moving the A/C on ground.
You are absolutely right, thrust is not linear, that's why (in real circumstances) you would not apply 60% N1 even with SE, because you would get a few things blown behind you and because around 50% would be enough. But you also know the rule no to apply more than 40% on ground, so the entire discussion is simply theoretical as under very rare circumstances would someone to try to taxi with SE.
(You know that if you close No.2 you won't be able to turn to the left, specially so if there's a wet surface).
Once rolling, thrust setting is pretty low. Somewhere between idle and 30% N1.
That's what I exactly said, many months ago.
I do understand that different simulator logic/friction value etc makes the development very difficult for you guys. I see the same difficulties when taxiing on single engine using other 737 addons.
It's not difficult, as a matter of fact, it is impossible, because FSX-P3D comes from a FM originally designed for single engine props.
Therefore ANY SE operation is just a bad approximation in ANY of the commercially available simulators, including FS2020.

regards
Lapi
RomanR
Posts: 140
Joined: 15 May 2020, 10:33

Re: Single Engine Taxi impossible

Post by RomanR »

I remember there was some kind of fix for the high friction problem in the PMDG 737 back in the FSX and P3D v3 times. It was a .lua script that required FSUIPC (registered version). I don't know what happened with that as it doesn't seem to be available for newer P3D versions, but it somehow worked and made SE taxi possible back in the days.
Best Regards
Roman
Lapi
Posts: 3037
Joined: 26 Nov 2011, 02:00

Re: Single Engine Taxi impossible

Post by Lapi »

RomanR wrote: 09 May 2021, 15:47 I remember there was some kind of fix for the high friction problem in the PMDG 737 back in the FSX and P3D v3 times. It was a .lua script that required FSUIPC (registered version). I don't know what happened with that as it doesn't seem to be available for newer P3D versions, but it somehow worked and made SE taxi possible back in the days.
That was before P3D went to 64 bits.
It is not possible anymore.

regards
Lapi
Tim
Posts: 65
Joined: 05 Apr 2021, 11:23
Location: Belgium

Re: Single Engine Taxi impossible

Post by Tim »

Lapi wrote: 09 May 2021, 12:24 Lapi, not Lapis. Otherwise it's kind of you picking a ten months old sentence of mine.
Yeah it looks like an autocorrect problem with my phone :D sorry :lol:
Lapi wrote: 09 May 2021, 12:24 The logic is definitely not the same for taxi, so when you mention theoretical values in flight, is not related to moving the A/C on ground.
You are absolutely right, thrust is not linear, that's why (in real circumstances) you would not apply 60% N1 even with SE, because you would get a few things blown behind you and because around 50% would be enough.
It seems to me that you don't get what I say. Because thrust is not linear you will NEVER need twice the power of what you use with 2 engines. I guarantee you that with 60% N1 you will get that baby moving pretty fast.
To start a taxi on a single-engine, 40% N1 should get it going, slowly but surely (unless high upslope).
Lapi wrote: 09 May 2021, 12:24 But you also know the rule no to apply more than 40% on ground, so the entire discussion is simply theoretical as under very rare circumstances would someone to try to taxi with SE.
(You know that if you close No.2 you won't be able to turn to the left, especially so if there's a wet surface).
I don't see why this is theoretical as we use it on a daily basis and it works very well, even on a wet surface (no matter what turn). But I do understand simulation limitation to have a good friction effect.

Cheers

Tim
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