Pulling it too soon....

[TMetzinger]

Or - pitch and power yield performance.

 

[dmccormack]

Dan:

I suspect that, someone like Mari, is pretty qualified on this subject.

The thing is--no matter what I say--you're not going to see the light. You just aren't getting that they are both connected and it works both ways exactly.

Oh I know exactly what you're saying and since I fly, I know the two (pitch and power) are very related. When I'm flying alone left seat I don't hink "Pitch for airspeed, etc". It just happens.

But -- it's pretty useless to tell a student "You'll get a feel for which one controls which eventually."

Plus, the pitch for airspeed, power for altitude makes setting up descents on ILS or a short grass field very easy, predictable and consistent.

Your view:
Pitch for airspeed, power for altitude

1. Decrease Pitch
2. Increase Power
3. Equals more airspeed with same glideslope

I didn't say that.

The answer you want me to say is:

1. Increase Power

That is fine. Because of course--that is the first thing you're going to do. But you'll find yourself doing this as well:

1. Increase Power
2. Increase Pitch (this may happen some on its own on SOME planes. not all)

You could swap number one for two, and as long as you did them both, you would be fine.

If you were low, and the a/s was dead on, and you added power, why would you change pitch?

Dan, the point I'm trying to get at, is really its both. Depending on the question one throws out there you can switch which one most pilots are likely to do first.

If Mari needs more airspeed in her Learjet and is on the glideslope I suspect she will just increase power a little bit. She may have to change pitch some--but it will be very small--as she barely increased power and is pretty much a super pilot, so it will be natural without thought.

And that's fine once the reactions are internalized.

But you cannot teach so that people immediately operate at that level -- you have to explain, they have to practice, and they have to comprehend, apply, correlate, and in some cases, innovate.

 

[Everskyward]

OK, maybe I figured out a better way to explain it.

In most airplanes (discounting ones with high mounted engines) if you leave the trim alone, power will control altitude. Since you are trimmed for an airspeed the airplane will pitch up and climb when you add power (of course this could be seen as changing the pitch too). If you leave the power alone, pitch will control airspeed. Obviously if you pitch down you will speed up. This is nice in theory. I know it seems easier to teach students the simplified version, and I understand the reason for teaching pitch controls airspeed is so that they will be less likely to get too slow if their first reaction is to put the nose down, especially since trainers do not have a whole lot of excess power. However, if you have altitude constraints the simplified version does not work very well.

 

[dmccormack]

In most airplanes (discounting ones with high mounted engines) if you leave the trim alone, power will control altitude. Since you are trimmed for an airspeed the airplane will pitch up when you add power. If you leave the power alone, pitch will control airspeed. Obviously if you pitch down you will speed up. This is nice in theory. I know it seems easier to teach students the simplified version, and I understand the reason for teaching pitch controls airspeed is so that they will be less likely to get too slow if their first reaction is to put the nose down, especially since trainers do not have a whole lot of excess power. However, if you have altitude constraints the simplified version does not work very well.

Good point, but the pitch = airspeed/ power = altitude works very well in the pattern and other places.

How about stall recovery?

 

[dmccormack]

Anyone willing to offer an answer to the AoA on descent question?
B)

 

[flyingcheesehead]

So you're saying AoA is different in a descent than in cruise?

[Hint: THINK before you answer]

And -- can you descend with a greater AoA than what you had in cruise?

Anyone willing to offer an answer to the AoA on descent question?
B)

Yes yes yes!!! I've been offline for a couple days.

AoA in a steady-state descent at the same IAS as cruise will be the same as it was in cruise. Read what I wrote a few days ago:

7) As we accelerate from climb speed to cruise speed, the increasing indicated airspeed means that we don't need such a high angle of attack to maintain the same lift. We slowly lower pitch attitude (and trim nose-down for the higher speed) as we accelerate. AoT=0, so AoA equals pitch again, and lift = weight while we're in a steady state vertically.

8) Transition to descent: Let's say we're going to descend at cruise speed, leaving trim unchanged and lowering power. Lowering power means that there will be more drag than thrust. That will slow the airplane down, and since we're trimmed for cruise airspeed, the nose will lower to compensate. When the nose lowers, AoA will be reduced, again resulting in weight being greater than lift, resulting in downward acceleration. Since we started with our vertical speed and AoT at zero, the downward acceleration will result in a descent. If we hold descent attitude, the AoT will lower until once again the AoA is back to the same value it was at in cruise. So, since we have the same indicated airspeed as we had at the end of cruise, once the AoT is lowered to where the AoA is the same as it was in cruise, we'll have a steady-state descent.

9) In the steady-state descent, lift=weight. AoT will be negative, pitch will be somewhere around zero, AoA will still have the same positive value as it did in cruise if we are still at cruise airspeed.

It's the transition from cruise to descent where the AoA will momentarily be lowered.

 

[flyingcheesehead]

A stalled wing still produces some degree of lift. Therefore it is entirely possible for a wing to be more stalled than the other-

Agreed - I just was picking nits. I had a post typed up about part of the wing being completely stalled rather than the whole wing being partially stalled... But then my damn aircard crashed my machine again and I lost that post.

 

[docmirror]

What I have learned from this thread:
I will never, ever post in this topic again. I can't begin to describe how sorry I am that I brought this up. We've been all over the place, when I answered my own point long before putting electrons to screen.

 

[dmccormack]

What I have learned from this thread:
I will never, ever post in this topic again. I can't begin to describe how sorry I am that I brought this up. We've been all over the place, when I answered my own point long before putting electrons to screen.

I'm very sorry to hear that, Doc.

I thought there was a good exchange with some excellent clarifications/ corrections/ learning -- I know I sure did.

 

[docmirror]

I'll get over it. Another thing I've learned, well knew already I guess. Knowledge transfer from the internet is a tough one.

 

[flyingcheesehead]

What I have learned from this thread:
I will never, ever post in this topic again. I can't begin to describe how sorry I am that I brought this up. We've been all over the place, when I answered my own point long before putting electrons to screen.

Doc,

I'm sorry to hear that as well - This is a great thread, lots of learning going on, and nobody's gotten snippy. It's given us all an opportunity to think through your situation and several others in detail, and made us all just a bit better pilots. What's there to be sorry for?

 

[docmirror]

Post #2 compared the technique to a 172, which is decidedly un-Bonanza-like. Post 3 has flown a Bonanza(big tail), but disagrees about the trim range. Post 7 - infinity Dan(who has the right plane) starts disagreeing with everything my empirical experience just taught me.

Yes, the plane does enter the reverse command if you pull too soon at high weight and DA. If you want proof, we'll find a long runway, some sacks of cement and I'll be glad to show you. Yes, I know what AoA or AOA is.

I was trying to get this quite simple principle across, I can take off with light, cool conditions much sooner than with hot, heavy. If I leave the plane on until 73MPH solo on a cool day, it will skitter across the ground, don't want that.

 

[jesse]

Post #2 compared the technique to a 172, which is decidedly un-Bonanza-like. Post 3 has flown a Bonanza(big tail), but disagrees about the trim range. Post 7 - infinity Dan(who has the right plane) starts disagreeing with everything my empirical experience just taught me.

Yes, the plane does enter the reverse command if you pull too soon at high weight and DA. If you want proof, we'll find a long runway, some sacks of cement and I'll be glad to show you. Yes, I know what AoA or AOA is.

I was trying to get this quite simple principle across, I can take off with light, cool conditions much sooner than with hot, heavy. If I leave the plane on until 73MPH solo on a cool day, it will skitter across the ground, don't want that.

It sounds to me like you would prefer no one post at all in the thread. Welcome to Pilots of America. We post our thoughts in threads and people learn. All I see is learning occurring here.

When you start a thread you don't own the thread. All you own is your post. People are free to write what they feel as long as it isn't in violation of the RoC. You are making something out of nothing.

 

[dmccormack]

It sounds to me like you would prefer no one post at all in the thread. Welcome to Pilots of America. We post our thoughts in threads and people learn. All I see is learning occurring here.

Must be something going on in this thread, given the number of posts, the number of views, and the relatively cordial, civil exchange.

 

[gismo]

OK.. now answer the question...

I gotta go with Jesse on this on (belatedly). It's a combination of pitch and power that determine both vertical speed and airspeed. There are examples where either relationship is "proven" wrong. E.G. sitting still on the runway, pitch has very little impact on airspeed compared to power and in many airplanes (a Lake being the classic exception) adding power in flight without retrimming will decrease the stabilized hands off airspeed.

Alternatively, rolling down a level runway (with or without a conveyor) with forward elevator your altitude will never change until you change your pitch attitude regardless of how much power you add.

 

[gismo]

Post #2 compared the technique to a 172, which is decidedly un-Bonanza-like. Post 3 has flown a Bonanza(big tail), but disagrees about the trim range. Post 7 - infinity Dan(who has the right plane) starts disagreeing with everything my empirical experience just taught me.

Yes, the plane does enter the reverse command if you pull too soon at high weight and DA. If you want proof, we'll find a long runway, some sacks of cement and I'll be glad to show you. Yes, I know what AoA or AOA is.

I was trying to get this quite simple principle across, I can take off with light, cool conditions much sooner than with hot, heavy. If I leave the plane on until 73MPH solo on a cool day, it will skitter across the ground, don't want that.

I hope you didn't think my comments about AoA vs Pitch were aimed at you. I was responding to remarks from Dan (who I believe also knew the difference between the two but was posting an unnecessary and confusing statement about them being the same thing).

But back to your original issue, it is certainly true that you can more easily get away with "pulling" the plane off the runway below the optimal airspeed in a low DA situation than when the air is thin, but the optimal speed for the initial climb is always the same (adjusted for weight) regardless of the DA. And I think the reason for this is rather obvious, it's because with a lower DA you have considerably more power than what's required to hold the plane in the air. As you mentioned, you can lift off and fly with the airspeed below the speed at the bottom of the power required curve but as indicated by that curve the further below that speed the more power you will need. At high DA there's less power available and more power required so the difference can be quite remarkable.

 

[dmccormack]

I hope you didn't think my comments about AoA vs Pitch were aimed at you. I was responding to remarks from Dan (who I believe also knew the difference between the two but was posting an unnecessary and confusing statement about them being the same thing).

But back to your original issue, it is certainly true that you can more easily get away with "pulling" the plane off the runway below the optimal airspeed in a low DA situation than when the air is thin, but the optimal speed for the initial climb is always the same (adjusted for weight) regardless of the DA. And I think the reason for this is rather obvious, it's because with a lower DA you have considerably more power than what's required to hold the plane in the air. As you mentioned, you can lift off and fly with the airspeed below the speed at the bottom of the power required curve but as indicated by that curve the further below that speed the more power you will need. At high DA there's less power available and more power required so the difference can be quite remarkable.

This is the last time (I hope!) I have to clarify, but the context and intent of my posts is being misrepresented.

In the context of determining pitch attitude on takeoff, the Attitude Indicator can be referenced and in the Bonanza series (from "small tail V" to A36), and that attitude is 10 degrees pitch up (There may be slight differences in various Bonanzas due to AI settings, stall strip placement, VG installation, etc).

In Bonanzas, 10 degrees nose up attitude will allow the airplane to accelerate from Vr to Vy.

Is there a relationship or correlation between 10 degrees nose up on takeoff and AoA?

Absolutely.

Is that the case in all flight regimes?

Absolutely not.

The 10 degrees shown on on the AI doesn't equal "10 degrees AoA".

Rather, the airplane's attitude on takeoff (level wings, or nearly so) can be consistently set and the airplane will fly off at that angle. There may be a slight reduction in that angle for High DA conditions, but the reduction is slight -- on the order of 2-3 degrees.

By verifying the pitch up attitude on takeoff (as another cue checked to determine performance) the pilot will know that she will not exceed critical AoA. Also, less than optimal pitch up attitude (from 10 degrees to 5, for example) will increase the time to altitude and reduce the angle of climb.

Sorry, but I don't buy the "Well, they're gonna do it anyway, so teach them to only use the Airspeed indicator."

Really? What happens when a bug smashes into the pitot tube? Or they left the cover on and failed to check airspeed alive on the ground run?

Airplane attitude on takeoff is another Very Important Cue that should confirm all the other cues you use to determine the airplane's performance.

No pilot should depend on a single gauge or indicator when others are available to verify and check the indications of the first.