engine power

[mvsgas]

Tyger, if I may, I would like to quote your sig

leave your semantics at the door

[Frostiken]

Normally I'll jump up the ladder to take a quick look or if it's beyond my knowledge and specs or weapons show up and notice the system hasn't even been powered up...

 

True story from two weeks ago from E-models:

 

Pilot: "Hey, our UFCs aren't working... well his in the back wasn't working but now it is."

Me: "Alright, I have to ask - is it turned on?"

Pilot: "Yeah, it flashed briefly, but now there's nothing on it."

WSO: "Mine did that but it came on later."

Me: "Can you turn it off and on again?"

<Pilot reaches up, turns knob. UFC flashes to life.>

Pilot: "Oh. Uh. It's working now."

Me: "Yeaaaah.... uh, was that all?"

 

 

On the topic.... I just push the throttle and listen for the vroom.

[Heli Shed]

Tyger, if I may, I would like to quote your sig

 

:thumbup:

 

soooo true!

 

'T'

[LawnDart]

Only half-true when there's actually a difference. ;)

[LawnDart]

For someone who flies a plane with the TF-34's sister engine, the CF-34 (Bombardier CL-65), we use N2 (core speed) settings for lower rpm (mostly ground, crossbleed starts etc.) and N1 (fan speed) for higher rpm settings (when airborne). It's obviously a mix of both, but these engines are actually under electric fan speed control above a certain rpm (79% N2 I believe), which means they're "N1 controlled" at anything above that, while below this percentage they're under hydro-mechanical control or "N2 controlled" when you move the thrust levers.

 

(Sorry if I'm a bit rusty. That's what happens when you fly the somewhat bigger version of the same jet with FADEC controlled engines).

 

While I'm unfamiliar first hand with the specs of the TF-34, I'd say that's a safe assumption.

[BlueRidgeDx]

Core RPM is usually the setting one typically looks at when setting power because it responds the fastest and can be set the most precise and reliably. Fan RPM is actually the most indicative of thrust because about 80% of the thrust of the engines comes from bypass air. Now you know where both opinions came from and why people would disagree! Isn't learning fun.

 

To say that N2 is primarily used to set power is only true of a small subset of airplanes, and even then, it's not 100% true for the A-10. The vast majority of airplanes allow the pilot to set N1 directly and very accurately (within 0.1%).

 

 

V-NE is 450 knots. There is not a "V-NE Mach" that would be M-NE for "Mach, never exceed." I think all V-speeds are given in IAS, maybe CAS I forget. Of course you can't always fly up to V-NE or M-NE safely because there are other restrictions like the barber pole or stores or otherwise.

 

Again, Vne is not applicable to jet airplanes. The correct terms are Vmo (Velocity, Max Operating), and Mmo (Mach, Max Operating). Vmo/Mmo is represented on the airspeed indicator by the moving Barber Pole. The Barber Pole will move to indicate the lower of 450KIAS or Mach .75.

[Griffin]

Fan RPM is actually the most indicative of thrust because about 80% of the thrust of the engines comes from bypass air.

 

I don't know THE answer to the original question but this is true only at sea level. When going up the ratio changes and at cruising altitudes it can be 50/50 % between core and fan.

[ashcanpete]

These kinds of discussions are why I can't get enough of this forum.

 

I love the way these threads always start off with a suggestion to read the manual, only to be followed by a 4 page intensive exposition on far more material than is ever covered in the manual.

[LawnDart]

So true. Good convo.

 

I'm not suggesting there's a right or wrong answer, but I know I'll be using N1 as my primary target thrust number in the upper troposphere tomorrow (and the FADECs would concur ;) )...

[Yo-Yo]

Well talking to some of our pilots I got a mixed bag. Some say they go by Fan others by Core speed. I myself call out Core speed if a wingman asks.

 

Basic thermodynamics for the turbofan determins that Fan speed is a function of Core speed, i.e. for given full pressure and temperature at the inlet station of the engine we will have determined Fan speed for a given Core speed.

 

So both numbers are equal as indicators of the thrust

Edited July 28, 2011 by Yo-Yo