mspano85

Hey Guys,
I'm stuck on a few questions and for some reason I can't seem to even find the answer google searching or clearly defined in my books.

The first one I keep going back and forth.

Increasing speed also

A) increases lift, drag, control surface effectiveness and altitude.
B) decreases altitude.
C) increases lift, drag, and control surface effectiveness.

I know B) is wrong. I'm trying to think logically here for the other two. It's the altitude one that gets me. I think of a car. When I accelerate and increase speed the car will raise. The same thing happens when accelerating down the runway. Since it does increase lift on the wings, it should increase altitude, correct? Or is that just the torque increasing the altitude?

The second question is about axis. I answered all my other axis questions fine but this one pertains to the center pressure of a wing and I'm not comprehending it on my own. Maybe you all can enlighten me.

The center of pressure of a wing causes the aircraft to rotate around the _____________ axis and affects the _________________ stability.

A) longitudinal / lateral
B) lateral / lateral
C) lateral / longitudinal

I think A) is wrong. Lateral Axis of flight would be wingtip to wingtip, pitch, whereas longitudinal would is tip to tail. I'm lost on which stability it would affect?

Thanks for any help guys. I appreciate the answers. My apologies if this is "Airplane 101."

UAL T38 Phlyer

First question: What if you were inverted? Going faster would create more lift and...you would go down.

So altitude is a distractor.

Second question: how well does a wing fly by itself? Ever built one of those drug-store balsa gliders, and watched what the wing does if it falls off the fuselage?

They tumble, normally forward. The more lift you make, the more nose-down the wing wants to go. That is why you have a horizontal stabilizer: to counteract that force.

I won't do your homework for you. These should be enough clues.

Don't confuse the orientation of the Axis with the direction of the MOTION around it...

mspano85

Perfect! This is mainly what I was looking for in terms of an answer. Something to lead me in the right direction!

Question 1 solved. Putting the plane "inverted" helped me realize the solution. I was leaning towards "No" for the altitude so that worked out good.

As for number 2 thinking about the horizontal stabilizer helps. I was pretty certain Lateral was the correct axis. Without the horizontal stabilizer the planes motion would to be to roll forward, which is directly related to the Longitudinal Stability of an airplane.

I hope I'm thinking this clearly. I'm going with lateral/longitudinal as my answer.

Thanks UAL

UAL T38 Phlyer

You're welcome!

mspano85

Part 2!!! I need some help figuring this out...

Which engine condition is to be avoided when operating a constant-speed propeller?

A.Low RPM with low manifold pressure.
B.Low RPM with high manifold pressure.
C.High RPM with low manifold pressure.

I'm a little confused and having trouble figuring it out.

Any help would be appreciated!

Thanks all!

pokey9554

This can be compared to driving a manual transmission car.

Think of the prop as the wheels on your car. Think of the manifold pressure as the position of the gas pedal. Is it harder on your engine to:

A. Be going slow with the gas pedal near idle
B. Be going slow in 6th gear with the pedal floored
C. Be going fast with the gas pedal near idle

mspano85

I was trying to compare by using automobiles before I asked and I was thinking the answer would be B. Being in high gear at the lower speeds driving around town puts a lot more load on the engine. My guess is you probably wouldn't have as much oil pressure as well.

However, if going fast, higher rpm, with the gas pedal near idle, the second you step on the pedal you're going to be "redlining" it.

I'm still a little torn. I'm guessing at the exact moment, B would be the correct answer, but if anything changes it could easily be C.

I hope I'm thinking this through the right way.

mspano85

Actually, I see. It is B. Having the pedal floored from low speed in high gear is going to put a ton of stress, load on the pistons, etc..

Got it!

Thanks for the help!