finally got airborne and had a decent lesson. but I have a ?

[korben88]

After 2 lessons that never got off the ground due to mechanical issues (like the one where I ended up in a field because of a faulty brake) I was able to get some flight time today.

Started off with a couple aborted takeoffs which honestly had me anxious thanks to my previous experience. Pulled them off without a hitch though.

Then we did a couple touch and goes, the first was ugly, but knocked the rust off and I cleaned it up on the second.

Next we went out to the practice area, did a couple steep turns, one ugly but passing and the next was much better.

A simulated engine out landing out at tvy and we headed back to u42 to practice slips to a landing. My slip and approach was decent, but I sailed long on the landing. ATIS said calm winds, but the sock was favoring 16 on inbound. Passing the sock after landing however showed the winds had swiched to 34. I powered up and on climb out checked on old glory south east of the airport and it was pointing north again.

We circled around, checked the sock (showing 34 still) and setup for a 45 downwind for 34. Just as I'm about to come in a copter says winds are favoring 16. So I loopty loop and setup for an entry to 16 (righ traffic) and come in for another slip to landing. Again I floated down the runway. And again the sock showed a tail wind.

So I decided to call it a day. I was glad to get in the air especially on such a nice cool morning. Getting the aborted takeoff monkey off my back was nice and setup for a great day.

Next lesson short and soft takeoff/landings


Anyways my question is this: my instructor mentioned that Va decreases as the weight of the plane decreases. why is that?

 

[RyanB]

To try and explain in a simple way... The lighter the aircraft is the steeper the angle of attack can be before the airplane breaks into a stall. The heavier it is, the lower the angle of attack will be to create a stall. So basically when the weight goes down, the aircraft can be maneuvered at steeper AOA's in a sense. I know someone will be along to explain it better than this. Hopefully this will help!

 

[ollopa]

This is the best explanation I've found: http://aviation.stackexchange.com/q...aneuvering-speed-vary-with-weight/18917#18917

 

[RotorDude]

Think of this. The lighter the aircraft is the steeper the angle of attack can be before the airplane breaks into a stall. The heavier it is, the lower the angle of attack will be to create a stall. So basically when the weight goes down, the aircraft can be maneuvered at steeper AOA's in a sense. I know someone will be along to explain it better than this. Hopefully this will help!

No, that's a misconception.
The angle of attack at stall is essentially the same, regardless of weight or wing loading.

 

[ircphoenix]

Maneuvering speed is designed to protect the airframe and components in the plane from rapid acceleration. Since the heavier plane can't get forced around as much, you can fly a bit faster. The lighter plane will get forced around easier, so you can't fly quite as fast. A rapid deflection of the control surfaces isn't going to generate as much acceleration in a fat plane as it will in a light plane. So a fatter faster plane is going to break *AFTER* a slimmer plane traveling at the same speed.

I like to think of it as if you're driving a tank, you're not gonna feel a wall if you run into it at 20mph. If you're on a moped, you're going to be hurting, even at the same speed. Same general principle.

 

[RyanB]

No, that's a misconception.
The angle of attack at stall is essentially the same, regardless of weight or wing loading.

A heavy aircraft will take longer to accelerate into a steep AOA vs. a light aircraft. Va is more or less calculated based on G loading.

 

[Cooter]

To try and explain in a simple way... The lighter the aircraft is the steeper the angle of attack can be before the airplane breaks into a stall. The heavier it is, the lower the angle of attack will be to create a stall. So basically when the weight goes down, the aircraft can be maneuvered at steeper AOA's in a sense. I know someone will be along to explain it better than this. Hopefully this will help!

Critical AOA stays the same, but for a heavier weight an aircraft will have to fly a higher AOA to maintain the same speed. It will therefore be closer to the stall at the same speed. For a lighter weight, the excess lift can be converted to angular momentum. The lighter it is, the more "pull" is available to turn and pull "Gs".

 

[RotorDude]

A heavy aircraft will take longer to accelerate into a steep AOA vs. a light aircraft. Va is more or less calculated based on G loading.

All of which has nothing to do with your statements above that "The lighter the aircraft is the steeper the angle of attack can be before the airplane breaks into a stall" or "The heavier it is, the lower the angle of attack will be to create a stall", both of which are plain wrong.

 

[RyanB]

Critical AOA stays the same, but for a heavier weight an aircraft will have to fly a higher AOA to maintain the same speed. It will therefore be closer to the stall at the same speed. For a lighter weight, the excess lift can be converted to angular momentum. The lighter it is, the more "pull" is available to turn and pull "Gs".

Which is basically the same thing I wrote above. I tried to simplify it so it's easy to understand. Va can be a very confusing topic.

 

[RotorDude]

Which is basically the same thing I wrote above. I tried to simplify it so it's easy to understand. Va can be a very confusing topic.

Perhaps you find it confusing, but that's no reason to post statements that are completely wrong and may confuse newbies.

 

[RyanB]

Perhaps you find it confusing, but that's no reason to post statements that are completely wrong and may confuse newbies.

Im not trying to get down to the nitty gritty here. The lighter airplane can accelerate into a steeper AOA and fly a higher G load slower than that of a heavy aircraft, not sure how that's incorrect. I suppose the way I have been explaining it should have raised reg flags during BFR's and checkrides.

 

[Cooter]

Im not trying to get down to the nitty gritty here. The lighter airplane can accelerate into a steeper AOA and fly a higher G load slower than that of a heavy aircraft, not sure how that's incorrect. I suppose the way I have been explaining it should have raised reg flags during BFR's and checkrides.

It's the way you are saying AOA is "steeper". The AOA is essentially the same. I think you mean attitude, but that doesn't really apply either because attitude is irrelevant.

 

[RotorDude]

Im not trying to get down to the nitty gritty here. The lighter airplane can accelerate into a steeper AOA and fly a higher G load slower than that of a heavy aircraft, not sure how that's incorrect. I suppose the way I have been explaining it should have raised reg flags during BFR's and checkrides.

It's not a matter of "nitty gritty". You post completely and unequivocally wrong statements and refuse to accept that they were wrong. This might confuse newbies who rely on this forum for information from experienced members. It's fine to make a mistake, we all do, but you should at least accept that you were wrong instead of trying to change the subject or sweep it under the rug.
As far as BFR's and checkrides, I suppose most CFIs focus on the flying and perhaps regs, and don't expect you to be an aerodynamicist, but these are very basic points that could some day save your life if you understand them properly.

 

[RyanB]

It's not a matter of "nitty gritty". You post completely and unequivocally wrong statements and refuse to accept that they were wrong. This might confuse newbies who rely on this forum for information from experienced members. It's fine to make a mistake, we all do, but you should at least accept that you were wrong instead of trying to change the subject or sweep it under the rug.
As far as BFR's and checkrides, I suppose most CFIs focus on the flying and perhaps regs, and don't expect you to be an aerodynamicist, but these are very basic points that could some day save your life if you understand them properly.

I'm happy to admit to a fault, I just dont see what's so astronomically wrong with the above statements. I guess was taught incorrectly.

 

[RotorDude]

I'm happy to admit to a fault, I just dont see what's so astronomically wrong with the above statements. I guess was taught incorrectly.

Key points: Your stall AOA is independent of weight, wing loading and speed.
The greater the AOA (below the stall angle), the more lift the wing produces per given airspeed.
If you are heavier and want to stay level, you need more speed (or more AOA, but that's limited by the stall AOA), to produce the required extra lift.
If you look at the lift equation, you'll see it's independent of weight or wing loading.

 

[Vance Breese]

To try and explain in a simple way... The lighter the aircraft is the steeper the angle of attack can be before the airplane breaks into a stall. The heavier it is, the lower the angle of attack will be to create a stall. So basically when the weight goes down, the aircraft can be maneuvered at steeper AOA's in a sense. I know someone will be along to explain it better than this. Hopefully this will help!

I feel it is important to understand stalls and angle of attack because of the number of stall/spin accidents.

In my opinion the loading does not change the angle of attack the wing stalls at.

I feel this is the antithesis of what you posted.

A lightly loaded airplane does not stall at a higher angle of attack than the same airplane with a heavy load.

I feel someone would be foolish trying to learn to fly from the posts on Pilots of America because of the amount of incorrect information. My hope would be that reading the posts would help the student understand what he didn’t understand and ask his instructor to reconcile the divergence between the posts and what he understood.

 

[korben88]

Thatnks for the replies everyone. I think I have a good grasp on it now.
I asked my instructor and he gave me an answer, but we were kind of rushed for time. I find it helps me to get a few different points of view on stuff like this anyways, and striking up a conversation about it is always good too. Most stuff I've learned on here is from reading other members posts.

My instructor did say that at the private pilot level the science wasn't necessary to know as long as you're aware that lighter plane = lower Va.

 

[korben88]

Oh, I forgot to add on my lesson break down how we did a small bit of "mountain flying" and scared some sheep

That was fun!

 

[exncsurfer]

Thatnks for the replies everyone. I think I have a good grasp on it now.
I asked my instructor and he gave me an answer, but we were kind of rushed for time. I find it helps me to get a few different points of view on stuff like this anyways, and striking up a conversation about it is always good too. Most stuff I've learned on here is from reading other members posts.

My instructor did say that at the private pilot level the science wasn't necessary to know as long as you're aware that lighter plane = lower Va.

I'll give it a shot at over simplifying. For Va you want to be closer to the stall, the light airplane has to fly slower to be closer to the stall than the heavier one as its already closer at a given speed.

 

[ircphoenix]

I feel someone would be foolish trying to learn to fly from the posts on Pilots of America because of the amount of incorrect information. My hope would be that reading the posts would help the student understand what he didn’t understand and ask his instructor to reconcile the divergence between the posts and what he understood.

Are you kidding? These forums are PERFECT for new pilots. The back and forth that exists serves to educate everyone. One person says a common misconception and 5 other people jump on them immediately telling them that they are wrong, and THIS is why. It educates us ALL.

Now if these question threads only got 1 answer, then you'd be right. But they often end up 3-4 pages long of back and forth about the question that is asked, covering dozens of permutations of whatever the original scenario was.

 

[SoCal RV Flyer]

Are you kidding? These forums are PERFECT for new pilots. The back and forth that exists serves to educate everyone. One person says a common misconception and 5 other people jump on them immediately telling them that they are wrong, and THIS is why. It educates us ALL.

Now if these question threads only got 1 answer, then you'd be right. But they often end up 3-4 pages long of back and forth about the question that is asked, covering dozens of permutations of whatever the original scenario was.

It's like any internet forum....you've got to surf it awhile, and identify the truly knowledgeable, helpful people versus those who are all about bluster and bravado (and you know who you are! ). Separate the wheat from the chaff. Sometimes you see an consensus on a subject, and other times it's split right down the middle. The latter case is tougher...

And sometimes the response won't provide a final, definitive answer, but provides a compass to point the OP in the direction of further research.

 

[Vance Breese]

Are you kidding? These forums are PERFECT for new pilots. The back and forth that exists serves to educate everyone. One person says a common misconception and 5 other people jump on them immediately telling them that they are wrong, and THIS is why. It educates us ALL.

Now if these question threads only got 1 answer, then you'd be right. But they often end up 3-4 pages long of back and forth about the question that is asked, covering dozens of permutations of whatever the original scenario was.

I wasn’t kidding; I feel it would be foolish to try to learn to fly from POA.

It appears to me you misunderstood what I intended to communicate.

In my opinion there is value here for all pilots although I feel it is not a place to learn to fly.

I feel trying to separate fact from fiction by consensus is a mistake.

The original poster’s CFI feels the science is not important on a private pilot level as long as you're aware that lighter plane = lower Va. I am glad he has a CFI that will take the time to explain things to him on a level he can understand.

 

[ircphoenix]

It's like any internet forum....you've got to surf it awhile, and identify the truly knowledgeable, helpful people versus those who are all about bluster and bravado (and you know who you are! ). Separate the wheat from the chaff. Sometimes you see an consensus on a subject, and other times it's split right down the middle. The latter case is tougher...

And sometimes the response won't provide a final, definitive answer, but provides a compass to point the OP in the direction of further research.

Usually when it's split right down the middle, then it's an AIM answer, and it's a recommendation, not a regulation... and then people argue about whether or not you should follow the recommendation or not. And back in my day we were NORDO in the snow uphill both ways!

 

[bflynn]

Maneuvering speed is designed to protect the airframe and components in the plane from rapid acceleration. Since the heavier plane can't get forced around as much, you can fly a bit faster. The lighter plane will get forced around easier, so you can't fly quite as fast. A rapid deflection of the control surfaces isn't going to generate as much acceleration in a fat plane as it will in a light plane. So a fatter faster plane is going to break *AFTER* a slimmer plane traveling at the same speed.

I like to think of it as if you're driving a tank, you're not gonna feel a wall if you run into it at 20mph. If you're on a moped, you're going to be hurting, even at the same speed. Same general principle.

This. The lighter airplane is more maneuverable and therefore can maneuver in ways that could break the airplane more easily. You can make turns on a moped that you can't make in a tank. Va is lower when lighter because Va is a "safe" speed related to not being able to break the airplane.

And it sounds like there was a lot of confusion about AOA. We all know that AOA does not change with weight because the AOA is about the aerodynamic design of the airplane, right? You need more power to hold the same altitude when the plane is heavier. You might run out of power and not be able to maintain altitude at certain speeds. But the AOA is the same because weight does not change the aerodynamic design of the airplane.

 

[luvflyin]

.........................Anyways my question is this: my instructor mentioned that Va decreases as the weight of the plane decreases. why is that?

Because the whole point of Va is that you want the airplane to stall before it bends or breaks. Heavier airplane means a higher speed at which AOA reaches a point where the wing stalls.

 

[PilotRPI]

I have a degree in aeronautical and mechanical engineering. Graduated #2 in my class. Not saying this to brag, just trying to explain why my answers may be more correct than others:

First off, the angle of attack at which an airfoil stalls has nothing to do with weight of the plane, it all has to do with shape of the airfoil. It may be affected by reynolds number, if I remember correctly, but that wouldn't affect a GA aircraft with a relatively small airspeed envelope anyway.

Va, maneuvering speed, has to do with G loading. They want to make sure you don't overcontrol or overload the plane, especially in turbulent conditions. As discussed, a wing will always stall at the same angle of attack on your plane, after it stalls the loads decrease, so that max angle will create the most lift. Items in your plane are designed to withstand a certain number of Gs. At gross weight, your max lift (and G's) is at the highest coefficient of lift, which happens shortly before the stall angle of attack. Again, this is a fixed value (angle). There is a certain speed at max weight, which this angle and Cl, creates a certain loading of G's that equals the max your plane was designed for. This speed is Va at max gross. To pull that same number of Gs at a lower weight, your speed will be a lower as the angle for max Cl (and the total lift force) stays the same since the wing area doesn't change. Now some people think, hey, my plane weighs less, and my wings are designed for a certain number of pounds of force, not a max number of Gs, so why can't I increase my G's at lower weights to maintain the same number of pounds of lift in my wings before they tear off?

Good question. And the answer is, you could. But there are structural elements all over the plane. While the plane's overall weight decreased, the engine did not, and the engine mount is designed for a certain stress. So while the wings might stay attached at higher Gs, the engine could rip off the mounts, or your baggage could rip through the floor at more Gs, etc. So while the weight decreases, the Va decreases so you don't overstress the other elements in the plane.

This is just the longitudinal axis. You also need to calculated similar things for roll and yaw axis, so it gets more complicated, but the general idea is the same.