Questions for you CFI's

hoff327

hoff327

Well-Known Member
Quick question for you guys, I am almost embarrassed to ask but for clarification purposes......

1. Why does an airplane stall at a higher airspeed while in a bank?

2. Which wing will stall first depending on the bank?

Thanks for your help, I appreciate it.

Mike
 
hoff327 said:
Quick question for you guys, I am almost embarrassed to ask but for clarification purposes......

1. Why does an airplane stall at a higher airspeed while in a bank?
Click to expand...

In steep banks a portion of the lift is devoted to turning the aircraft (horizontal component of lift). To maintain the same altitude (to make up for the lost vertical component of lift), back pressure must be applied. This increase in back pressure means an increase in angle of attack. Remember, a stall can happen at any airspeed, as stalling is only a function of angle of attack.

Since you have a higher angle of attack in a steep turn, you are closer to stalling than at level flight at the same airspeed.

2. Which wing will stall first depending on the bank?

Thanks for your help, I appreciate it.

Mike
Click to expand...

Both wings will stall at the same time if the aircraft is coordinated during the turn. Maintain coordinated flight, and no wing drop should happen.

Does that help?

G
 
slip - inside wind (low)
skid - outside wing (high)

that's my guess. anyone alse?

bueller
bueller
bueller
 
hoff327 said:
1. Why does an airplane stall at a higher airspeed while in a bank?
Click to expand...

As an added note, remember that stall speed only increases during a level turn. If you let the plane descend, instead of pulling back on the yoke and "holding" the plane up, the stall speed will not increase at all. You also won't have any increase in load factor, for that matter. Of course, an increase in stall speed and load factor are one and the same.

As an example of what I'm talking about, go flying and try to figure out a way to stall the plane without pulling back on the yoke or using excessive trim. It can't be done. It might sink, but it won't stall, regardless of attitude.

In case you're wondering why this matters, it's because it can work to your advantage when maneuving down low to the ground. I've flown with numerous people that don't feel comfortable putting the plane in a steep bank close to the ground because they're worried they'll get into an accelerated stall. I show them how it's not the bank angle that matters, but rather the increase in AoA/load factor from pulling back on the yoke that causes problems.

That being said, you have to understand that if you do not pull on the yoke, and therefore reduce the AoA/load factor, you will sink faster. If you're close to the ground, sinking can be a bad deal. But it's all tradeoffs and judgement calls anyway.

This can be handy knowledge when high and tight in the pattern, or needing to make a tight turn onto a field during a simulated engine failure. Not that I encourage pilots to make excessively tight patterns or misjudge the glide distance to fields, but I think this is an important concept to understand.

The bottom line--steep banks do nothing to stall speed as long as you're willing to let the plane descend.

hoff327 said:
Which wing would stall first in a slip or a skid?
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The wing that you're "stepping" on will always stall first. You could also say that the wing opposite the inclinometer ball stalls first, or that the plane will always "spin away from" the ball during a spin entry.

So if you have too much left rudder, it doesn't matter if you're in a slip or skid, it's the left wing that will stall first. Too much right rudder and the right wing will stall first.

Oh, and don't worry about asking questions. These aren't bad questions at all. You know why I know so much about the whole inclinometer ball/slip/skid/stall/spin concepts? Because it was one of the few areas that I was really weak in even after 300 hours of flight time and the examiner on my CFI checkride nailed me on it.
 
Got another one for you guys.....:)

Why does Manifold pressure increase when you reduce the RPM's of a constant-speed propeller?

Thanks for the help, I do try and read it but sometimes I have no clue what Jepp or the FAA are talking about in the text.....:insane:
 
Paraphrased from Manifold Pressure Sucks! (great article - find it at http://www.avweb.com/news/columns/182081-1.html):

Assume you have the throttle set, say at 20 inches of manifold pressure and engine/prop speed of 2000 RPM. Since this is a direct-drive system, the prop is turning at the same speed as the engine. If you reduce the RPMs using the propeller lever, the engine will now be turning at a slower rate. Slower rate of the engine means it is not working as hard, and creating less suction. Since the manifold pressure gage is really a measure of suction at the engine intake, MP will increase, despite the engine developing less power than before.
 
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