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Does RPM value shown on F-16 RPM gauge stands for N1 Value?

Just for curiousity...

If it is not, than what value does it show?

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Last edited by Habu on Dec 09, 2003 - 07:05 PM; edited 1 time in total

If there was only one tachometer, then yeah I would think so. But you have N1 and N2.

Its for N2 (compressor core). N1 would be for the Fan, which the F-16 is not showing (at least not in the cockpit), it is recording it in the EMSC (engine monitoring sustem computer)

Thank you guys!

When flying the fan and core are areodynamicly connected, one will not go faster than the other. the two different speeds N1 for fan and N2 for Core are only for engine fuel and air scheduling to enhnace engine performance. When in augmentation mode the engine is anywhere from 97% RPM to 104% RPM depending on manufacture and flight conditions.

Joined: Feb 01, 2007 Posts: 0 Status: Offline

WHAT? (Jet engine mechanics love this type of thread…………….)

Since when does a Crew Dawg know turbine engine theory and operation?

They are not "aerodynamically connected” In a PW Fan RPM is mostly controlled by Nozzle position and Core RPM is mostly controlled by fuel flow.

When "bad things" happen to an engine the fan may loose speed independently of the core and vice-versa.

I've seen damaged engines loose almost all their fan RPM, while the DEEC struggles to maintain EPR by keeping the core at max temp/speed to compensate.

Also..............when the engine accelerates or decelerates fan and core RPM will rise and fall independently of each other. This is due to compression/flow rates, fuel flow schedules, engine pressure, and augmentation back pressure.........

See one of your engine troops for an engine familiarization book.......

IDCrewDawg, Is right. Read up on it in the 70 GS.

Joined: Feb 01, 2007 Posts: 0 Status: Offline

the 70GS actually says that!?! is it for the PW or the GE? I'll look myself when I get back to work this week.........

Actually the GS says they are "aerodnyamically coupled" instead of connected. I know for a fact its in the PW version but I would suspect that it might be in both of them. I will check both books first thing in the morning.

Havent had a chance to dig through the GS yet. I did look in the handbook that GE gave me years ago though and it does state that the HPT and the LPT are aerodynamically coupled together.

Hmm, so a crewdawg does know what he is talking about over an engine troop? (playfull jab) Laughing

I know they operate seperatly (sp) however, if the core didn't turn the turbine wouldn't turn, therfore the fan woudn't turn. hmm sounds pretty connected (or coupled) to me.

Joined: Feb 01, 2007 Posts: 0 Status: Offline

To a point yes. But they spool up/down at different rates. They are affected by different operating parameters, and external factors.

Dual spool engines have been know to operate with the fan frozen for some reason or another......even if they don't run right.

N1 is dependant on N2 to a point, but not so much as the term "coupled/connected" would lead one to believe. The air flows through both N1 and N2 so they do share that.

Lets remember the GS is NOT where you want to go when troubleshooting the engine!

Where are the other Engine Troops to help me out here!?

Bix, I agree with everything you are saying about the engine. I was also agreeing with the one statement that the HPT and the LPT are "aerodynamically coupled". I know that there is MUCH more to it than just that one statement. I have taught the engine O&M class in FTD years ago so I have more than just a passing knowledge when it comes to engine lore Wink

. My engine classes anymore consist of engine run for GE and PW.

I also have more than just a GS knowledge base when refering to the engine. True to point the fan does spin down at a slower rate than the core, however at operational normal speed. Wich is what I was refering to, one can not operate effectively with out the other. If the fan is stopped, and I mean not turning, the engine will essentially suffocate, as airflow will be severly restricted. It will operate, but at a very reduced rate. True if the pilot goes to SEC (secondary) then nozzels are close, this is to give him maximum thrust with minimum effort. If he lost the nozzle completely it would be like blowing air through a straw, and would get very little thrust (correct me if I am wrong). Your knowledge of the PW engine is very good, I was talking in general terms of basic therory.

Joined: Feb 01, 2007 Posts: 0 Status: Offline

Basic theory, maybe, but the "coupled" statement must have been made by an AF Engineer who writes TOs for a living, and has never even seen a jet engine operate from the control cab.

An engine will make pleanty of power without the nozzle, just not "optimum".

Speaking of "engine lore", want to get into the how does a jet engine moves?
1. Screws it's way through the air like a propeller
2. Pressure on the turbine wheel pushes it forward
3. Pressure in the combustion chamber pushes it along
4. Mass acceleration through the engine
5. Pressure at the front of the engine is less than inside the engine...........
Shall I go on!?

I've had debates on that with 20+ year jet engine mechanics!

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