Turbine Questions

[avbug]

Furloughedgal,

The learjet pitches in response to the addition of power because the longitudinal axis of the engine is canted down and aft, and is not in line with the long axis of the airplane. Application of power will cause a downward pitching moment because of the thrust vector. It has nothing to do with being ahead of, or behind the power curve.

 

[ksus]

Hey Bobby hi!!
I don't mean to start an argument, but aren't we teaching our students : Power controls Altitude---and ---Pitch controls Airspeed?

fly safe!!

 

[Speedtree]

This argument will go on forever.

The reason is because the two are ultimately linked together. You can choose to see them as opposites, pitch and power controlling airspeed and altitude, or we can see the big picture. The airplane is flying in a state of motion (hopefully) in an airmass and any change in one will necessitate a change in the other. If you pitch down you will increase airspeed and lose altitude. If you reduce power you will slow down if you make the resulting pitch change necessary to hold altitude. (if you don't, the aircraft should continue in a flight path to achieve the airspeed it was trimmed at before the power reduction probably resulting in a descent) and so on. Let's look at them for what they are... both working in harmony to create a state of equilibrium for our aircraft.

Obviously there are different techniques we want to use for different flight situations and configurations.

 

[bobbysamd]

Endless argument

Absolutely. Coordinated pitch and power. Some would argue that you trim for airspeed. Isn't that what Wolfgang Langwische wrote in Stick and Rudder? I may be wrong.

Look at it in terms of flying an ILS. Add power while maintaining the glideslope and the airplane will gain airspeed.

The FAA's line has always been power controls speed and pitch controls altitude. I will opt out of the debate because it will never end. Just remember the FAA's line when it comes checkride time.

 

[Lindy]

Avbug you are correct...

I'm sorry if anyone thought that I was discussing aerodynamics with respect to the L/D curve.....I even stated 250K (last time I checked it wasn't near the "area of reverse command" or the "back side of the power curve" or whatever linguistics are being utilized).


The Learjet does have interesting pitching moments due to the thrust of the engines and is easily demonstratable.