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Driver170

N1 difference

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can anyone explain the discrepancy between the 2 N1 engines

 

 

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Both packs on AUTO

Sorry NO ENGINE BLEED TAKEOFF matt

ISOLATION VALVE CLOSED

Something to do with the pressure duct ?

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###### the N1 difference, what is that on the lower EICAS???

 

Surprisingly, the forum censors posts but not the emails it sends.

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Well good to know, In UK English, swearing has less effect, it can be used in endearment. You can easily use C U Next Tuesday (work it out) to your friends easily as a term of endearment

 

However, back to topic

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Something is not set right on the pneumatic panel.  Probably a pack or bleed switch in the wrong position.

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Without looking into the manuals. I don't know if this is modeled. But it could be something called "N1 Compensation".

This being the case, the N1 "limit" is reduced as the engine actually makes the required thrust at a lower N1. (Newer Engine).

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can anyone explain the discrepancy between the 2 N1 engines
Using the NGX default flight for five different flights both engines have the same N1 in the FMC. Your plane must be setup incorrectly. Find the difference between your panel state and the NGX default panel state and there is your answer.

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Both packs on AUTO

Sorry NO ENGINE BLEED TAKEOFF matt

ISOLATION VALVE CLOSED

Something to do with the pressure duct ?

 

RW, that would be indicative of one pack on, one pack off. You may have a bug.

 

Let's see a pic of the overhead panel with that N1 indication.

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Posted Today, 12:14 AM

Something is not set right on the pneumatic panel.  Probably a pack or bleed switch in the wrong position.

 

RW, that would be indicative of one pack on, one pack off. You may have a bug.

 

Let's see a pic of the overhead panel with that N1 indication.

 

PACKS AUTO

 

BLEEDS ON

 

APU ON - BLEED SW ON

 

ISOLATION VALVE - CLOSED

 

I will reconfigure the same setup today and post a pict and see if the N1 changes

Using the NGX default flight for five different flights both engines have the same N1 in the FMC. Your plane must be setup incorrectly. Find the difference between your panel state and the NGX default panel state and there is your answer.

 

I use my own panel. But i hope not! Never seen this before only when doing a NO ENGINE BLEEDS OFF

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PACKS AUTO

BLEEDS ON

APU ON - BLEED SW ON

ISOLATION VALVE - CLOSED

I will reconfigure the same setup today and post a pict and see if the N1 changes

pcubine, on 19 Jun 2015 - 10:53 PM, said:

Using the NGX default flight for five different flights both engines have the same N1 in the FMC. Your plane must be setup incorrectly. Find the difference between your panel state and the NGX default panel state and there is your answer.


I use my own panel. But i hope not! Never seen this before only when doing a NO ENGINE BLEEDS OFF

 

You have both the engine bleeds and the APU bleed on.  The proper config for a bleeds off takeoff is:

 

Right pack - AUTO

Isolation valve - CLOSE

Left Pack - AUTO

Engine 1 bleed - OFF

APU bleed - ON

Engine 2 bleed - OFF

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Something is not set right on the pneumatic panel. Probably a pack or bleed switch in the wrong position.

+1

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can anyone explain the discrepancy between the 2 N1 engines

 

This is related to the way PMDG have modelled bleed corrections to N1 command. It's come up before in the forum. They aren't looking at the bleed and pack switches as they should. It appears that they are looking at whether the packs are running and applying a correction to the associated engine's N1 command. It always assumes the engine is the bleed source. This works ok till you try a bleeds off takeoff.

 

So it's a limitation of the current simulation. Can't be fixed without a model update.

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This is related to the way PMDG have modelled bleed corrections to N1 command. It's come up before in the forum. They aren't looking at the bleed and pack switches as they should. It appears that they are looking at whether the packs are running and applying a correction to the associated engine's N1 command. It always assumes the engine is the bleed source. This works ok till you try a bleeds off takeoff.

 

So it's a limitation of the current simulation. Can't be fixed without a model update.

 

Thank you for that kevin.

 

Its certainly not my configuration, i always do a takeoff review and always check my essentials. Everything was setup right!

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Its certainly not my configuration, i always do a takeoff review and always check my essentials. Everything was setup right!

Vernon

 

In the NGX world, bleeds off is not correct. If you want the N1 for the two engines to agree as shown in your screenshot the bleeds must be on. Maybe your setup is correct for the real world but it not correct for the NGX world which is the one we live in when preparing the NGX for flight. Go to bleeds on.

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So its not possible for a bleeds off then?

Vernon

 

I have no idea. I have always switched to bleeds on once I have started the engines. Try a bleeds off take off and see what happens.

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A bleeds off take-off is certainly possible.

 

However, what was the reason why you had the APU on during take-off? I can only think of one scenario off the top of my head

 

Also, just noticed your new signature Vernon. I couldn't be any less surprised that you are a beta team for FS2Crew. :)

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A bleeds off take-off is certainly possible.

 

However, what was the reason why you had the APU on during take-off? I can only think of one scenario off the top of my head

 

Also, just noticed your new signature Vernon. I couldn't be any less surprised that you are a beta team for FS2Crew. :)

The APU is on for a bleeds off takeoff. It supplies air to one pack.

So its not possible for a bleeds off then?

It's possible to do from a procedural point of view, you just won't quite have the same N1 on both engines. It might be better to just switch the packs off for takeoff. That way the NGX won't compute any bleed correction for the engines. Then your performance will be right, though the cabin won't be getting any air. Simply turn the packs on after reducing to climb power.

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Also, just noticed your new signature Vernon. I couldn't be any less surprised that you are a beta team for FS2Crew. :)

 

Ha, thanks! Couldn't turn the opportunity down.

 

 

It's possible to do from a procedural point of view, you just won't quite have the same N1 on both engines. It might be better to just switch the packs off for takeoff. That way the NGX won't compute any bleed correction for the engines. Then your performance will be right, though the cabin won't be getting any air. Simply turn the packs on after reducing to climb power.

 

Is a packs OFF takeoff even approved? Never seen that procedure in the FCOM?

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