jgoggi

N1 increasing/decreasing with speed?

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Hi,

Let's consider the case where there are NO FD, NO A/P, NO A/T armed, so everything is manual and I am flying levelled at constant speed. Is it correct that, if the speed increases WITHOUT me touching the thrust levers, so for example I pitch down and the speed increases, the engines N1 slowly and constantly increases as speed increases? Viceversa, if I pitch up and the speed decreases, N1 will decrease? Same thing on the ground: I manually set an N1 takeoff thrust and there is NO autothrottle at all. As speed increases in my takeoff run, N1 increases as well. I suppose that this is due to the air speed that flows more quickly into the fan and makes it turn faster. Is that correct? In this case, the EEC does not intervene? Thank you.

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The EEC on a RR B744 has full authority over engine operation, irrespective of whether you are using the Autopilot/Flight Director and Autothrottle or manually flying the aircraft and handling your own engine thrust. 

In Normal Mode it controls the EPR based on the thrust lever position anywhere between idle and maximum EPR and in Alternate Mode it uses N1 rpm..  Furthermore, in Normal Mode it will also keep the thrust constant independently of the outside air temperature and pressure and even adjust the thrust automatically for changes in bleed and pressurisation needs, including wing and engine anti-icing. You can probably work out the rest of your answers!   🙂

Edited by berts

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Since I guess the EEC works the same in the GE engines (I haven't tested the RR), the answer is simple and it's a 3 letter words: BUG…. Going to open a ticket...

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10 hours ago, jgoggi said:

Since I guess the EEC works the same in the GE engines (I haven't tested the RR), the answer is simple and it's a 3 letter words: BUG…. Going to open a ticket...

Your hyperfocus on this topic over the years is interesting.

Nobody’s handing out gold stars for your celebration in finding these things, and I’m not entirely sure this is actually a bug, so the celebratory/accusatory speech is - at best - inappropriate.

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15 hours ago, jgoggi said:

Since I guess the EEC works the same in the GE engines (I haven't tested the RR), the answer is simple and it's a 3 letter words: BUG…. Going to open a ticket...

You guessed wrong. 🙂

Grace and Peace,

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3 hours ago, Bluestar said:

You guessed wrong. 🙂

I just need a proved proof that the EEC does not intervene and leaves the engine N1 do whatever it likes, then I will shut up...

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8 hours ago, scandinavian13 said:

Your hyperfocus on this topic over the years is interesting.

Nobody’s handing out gold stars for your celebration in finding these things, and I’m not entirely sure this is actually a bug, so the celebratory/accusatory speech is - at best - inappropriate.

Sorry, no accusatory/celebartory intention, here (it's only a pain for me if I find out any issue, not a joy...), only a bit surprised that this issue is still coming out after it has been fixed for the HOLD mode... Anyway, like I said above, if it is proved that the EEC does not control the N1 in manual thrust (I am talking about the GE engines), I will be very happy to regret having used that word...

Edited by jgoggi

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Look at this video from min. 3:00, it's the famous 747 PS1. The thrust levers are manually moved to the takeoff thrust of 101.0 N1... You can clearly see that N1 remains stuck at 101.0 as speed increases... I wonder how the HOLD mode has been fixed in the 747 QOTS II without fixing the manual mode...

 

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8 hours ago, jgoggi said:

Sorry, no accusatory/celebartory intention, here (it's only a pain for me if I find out any issue, not a joy...)

Then there would be no need for the over-the-top line, here:

On 1/27/2019 at 6:45 AM, jgoggi said:

the answer is simple and it's a 3 letter words: BUG

Just seems a bit overly-invested for something that brings someone pain. Any time I let someone know about a bug (or discuss it), it's pretty straightforward: I think this might be a bug.

12 minutes ago, jgoggi said:

Look at this video from min. 3:00, it's the famous 747 PS1. The thrust levers are manually moved to the takeoff thrust of 101.0 N1... You can clearly see that N1 remains stuck at 101.0 as speed increases... I wonder how the HOLD mode has been fixed in the 747 QOTS II without fixing the manual mode...

The Aerowinx is a good sim, but it's not the real plane. There are a number of things on any 744 sim that aren't 100% perfect there either.

Additionally, I'm still not quite sure you've found a bug here. Just because you see something you do not expect does not make it a bug.

 

 

To be clear, I'm more than happy to take up a case and bring it to the team to say "hey, this is broken." The takeoff pause bug (fixed in the next update) was one of those things. I like fixing bugs. I don't like sending people on a wild goose chase for some random assertion without real evidence that something is wrong. Pointing to another sim doesn't prove much of anything. Their modeling of something could be just as wrong as ours.

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1 hour ago, jgoggi said:

it's the famous 747 PS1.

How do you know Hardy got it right? Have you talked to him about it?  There have been a lot of changes in PSX since version 1.  

I own PSX 1 and 10 which are nice simulators, but PMDG/P3dv4 is my sim of choice and the one I fly almost exclusively. 🙂

Grace and Peace,   

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26 minutes ago, Bluestar said:

How do you know Hardy got it right? Have you talked to him about it?  There have been a lot of changes in PSX since version 1.  

I own PSX 1 and 10 which are nice simulators, but PMDG/P3dv4 is my sim of choice and the one I fly almost exclusively.

I owned PS1 but now it doesn't work anymore in my computer, this is just a video I found on YouTube. You my want to check if PSX behaves the same or not, it's very easy to find out... However, considering that the EEC controls the engine N1, it's logical to think that, if you provide a certain thrust at takeoff, it shall be kept constant, otherwise, at lift off, the thrust will be quite higher than the planned one…  

I hope Robert and the 747 pilots beta testers can confirm the correct behaviour, based on their real experience...

Edited by jgoggi

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Check out this training video related to PSX touch and goes: www.youtube.com/watch?v=PR66MkOpDjQ&feature=youtu.be

Ok, this is another simulator, I know, but PSX is very precisely simulated and comes 15 years after PS1. I don't think that, if PS1 was wrong, it is wrong as well...

Although the 747 in the video has RR engines, just look at N1 at around mins 3:00 and 10:50: N1 doesn't increase as speed increases...

The fact of N1 increasing/decreasing with airspeed increasing/decreasing is not correct, as it was not correct in HOLD mode. Please, it needs to be fixed as well. Thank you.

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On 1/28/2019 at 8:26 AM, scandinavian13 said:

The takeoff pause bug (fixed in the next update) was one of those things. 

Really looking forward to this. There’s no temporary work around we can use until the update, is there?

Alex Pugh

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Even on the PMDG 737 there is no N1 variation when speed increases at takeoff with manual thrust (see from min. 5:20)...

 

... and on the PMDG 777 (see from min. 19:20)...

 

Edited by jgoggi

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On 1/28/2019 at 2:26 PM, scandinavian13 said:

To be clear, I'm more than happy to take up a case and bring it to the team to say "hey, this is broken." The takeoff pause bug (fixed in the next update) was one of those things. I like fixing bugs. I don't like sending people on a wild goose chase for some random assertion without real evidence that something is wrong. Pointing to another sim doesn't prove much of anything. Their modeling of something could be just as wrong as ours.

It isn't a random asserion. With GE engines, the thrust lever position sets an N1 demand in the EEC. A linear interpolation between idle, CLB and TO N1. Changing airspeed, without significant changes to ambient conditions, will result in the engine adjusting fuel flow to maintain the demanded N1, unless other engine parameters become limiting.

 

On 1/29/2019 at 7:11 AM, jgoggi said:

The fact of N1 increasing/decreasing with airspeed increasing/decreasing is not correct, as it was not correct in HOLD mode. Please, it needs to be fixed as well. Thank you.

If it was fixed for HOLD mode then it ought to be working correctly with A/T disengaged. If it isn't then the fix wasn't applied properly.

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3 minutes ago, kevinh said:

If it was fixed for HOLD mode then it ought to be working correctly with A/T disengaged. If it isn't then the fix wasn't applied properly.

Thank you, Kevin, for your clarification. Indeed, what was a surprise for me was realizing that in HOLD mode it now works correctly, but not in manual thrust. Looks like the developers have "cheated" a little bit here, don't they? 😏

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