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martinpk

B777 N2 Indicator Reading High

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Just installed the latest version of the PMDG B777 in to FSX Steam. I noticed that the N2 engine indicator is reading about 10 percent to high. Not sure if this is a problem relating to FSX Steam or not. I do know that the previous version that was installed in FSX non steam reads correctly. Wondering if anyone else has seen issue. Not sure if it has something to do with simconnect.

Thanks.

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Just installed the latest version of the PMDG B777 in to FSX Steam. I noticed that the N2 engine indicator is reading about 10 percent to high. Not sure if this is a problem relating to FSX Steam or not. I do know that the previous version that was installed in FSX non steam reads correctly. Wondering if anyone else has seen issue. Not sure if it has something to do with simconnect.

Thanks.

 

Welcome to the forum, Martin (I'm assuming that's your name). Full names are required to be placed in every post here, per the forum rules.

 

As far as your post goes, what are you basing your data/comparison off of?


Kyle Rodgers

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Hello Kyle,

 

I based my observations on the previous FSX install and real life operation of turbine engines. At idle I get 70 percent N2 which is closer to a flight idle rpm than a ground idle, should be about 60-65 percent. At a takeoff power of 94 percent N1, I am getting an N2 of 108 which is at the redline and to high in relationship to the N!. I would expect somewhere around 98 to 102 percent N2. As stated if this is an issue with the steam edition or the update. Any help would be appreciated.

Thanks,

Martin

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Wow...there is someone who monitors his engines closely :-)

(I mean that in a good way).

 

But are you sure N2 Redline is 108%?

 

I know the GE90-90B (I know, little different engine) has N2 limit at 117%!

(and N1 limit 109%)


Rob Robson

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I based my observations on the previous FSX install and real life operation of turbine engines.

 

We need something a little more concrete than that. I have real life experience with reciprocating engines, but I wouldn't consider my knowledge of the usually tiny GA types (or even maintaining car engines) good enough to discuss the intricacies of big radials (though I've picked up a decent bit about the P&W 1830 over the past couple years). Do you have a table/chart of expected values?

 

Also, full names means first and last. Thanks for adding your first name in your last post, however.


Kyle Rodgers

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I can't find an actual table showing the idle parameters (though it ought to be in an FCOM/FCTM somewhere), but I did find this Flight International article (in which, incidentally, the author is invited by Boeing to test-fly a B777 for the review: what a gig!)

 

 

 

The engines were started one at a time using the auto-start feature of the full-authority digital engine controls. Each engine reached an idle N2 of about 69% in less than 1min, with exhaust gas temperature peaking at around 500°C

 

http://www.flightglobal.com/news/articles/flight-test-boeing-777-300er-fast-and-heavy-176585/

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Thanks folk,

 

Maybe then I stand corrected. I am a commercial pilot and aircraft mechanic. I have spent many hours on the flight decks of most of the Boeing and Douglas fleet performing various functions and tests. Been around the CFM56,CF6,RB211 and PW engines but very little time on the B777 variants. I can't give exact numbers from a graph as I don't have access to an AMM or ops manual. From what 777 simmer and skelsey have both stated with numbers, perhaps I am incorrect although 108 does seem rather high for a derated power setting 94 percent. The aircraft use a squat switch that senses weight on wheels, this puts the aircraft in ground mode so the engine goes from flight idle to ground idle. Flight idle is higher due to the chance having to perform a go around. 

I will do a little more research and see what I find.

 

Martin Picke'

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Okay, I guess that I am just used to operating the smaller fan engines. I did have an AMM and here are some numbers. These are for the GE90-100 series engines. N1 max 2602 rpm - 110.5 percent, N2 max 11292 rpm - 121.0 percent. For a typical max take off power run these are the numbers: Air temperature of 75 degrees, N1 81.24 percent, N2 109.1. these numbers used for power assurance runs to ensure that the engine will make takeoff power with out exceeding EGT limits.

Thanks to all,

Martin Picke'

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Thats an okay number for the N2 Spool, Infact the GE90s sometimes run higher speed cores becasue the turbines are that efficient, causes headaches let me tell you. Obviously the PMDG is going to be using some sort of standard numbers for the N2 calculation, but in the RW, the overhaul status of the engine will alter the core speed dramatically, for instance, if the stage 1 or 2 turbine blades need replacing due to high cycles then the turbine will get an overhaul,  but a borescope inspection of the compressor could yeild a servicable module so wouldnt need to be disassembled. It might have a rotor wash to clean it out. what you then get is a moderately efficient compressor with a very efficient turbine. Youve also got to remember that the HMU metering unit has a flyweighted overspeed valve totally independent of the FADEC system that will modulate an overspeed in the event that the core speed gets too high. Hope that gives a small insight !


Boeing777_Banner_Pilot.jpg

AME GE90, GP7200 CFM56 

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Thanks Dan,

I do agree with you on the HMU. If the engine had redlined the numbers will be showing red as an exceedence. As stated I am just not used to seeing such a high N2. PMDG has made a terrific job modeling the aircraft and look forward to the new B747-400.

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The GP7000 is similar too, although a pain in the a** to work on...Yeah they have done a great job on the modelling, and im very much looking forward to the 747 also!


Boeing777_Banner_Pilot.jpg

AME GE90, GP7200 CFM56 

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