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WingFlaps wrote:
On Mar 14, 9:11*am, Brian wrote: As for your question above, given that the airplanes are ascending or decending at constant rates then the lift is equal to the wieght of the airplane in both cases. If the aircraft are the same wieght then the lift generated will be the same. That is not correct. Hmmm. Brian's statement appears essentially correct - and you are correct too. The "gotcha" is that the vertical component of the lift force exceeds the weight only during the transition from level flight to constant ascending flight. And the lift force is less than the weight during the transition from level flight to constant descending flight. But once the vertical speed becomes constant (whether up or down) the vertical component of lift has to equal the downward force of gravity. If it didn't, then the aircraft would begin _accelerating_ up or down, depending on the difference. |
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On Mar 14, 9:33*am, Jim Logajan wrote:
WingFlaps wrote: On Mar 14, 9:11*am, Brian wrote: As for your question above, given that the airplanes are ascending or decending at constant rates then the lift is equal to the wieght of the airplane in both cases. If the aircraft are the same wieght then the lift generated will be the same. That is not correct. Hmmm. Brian's statement appears essentially correct - and you are correct too. The "gotcha" is that the vertical component of the lift force exceeds the weight only during the transition from level flight to constant ascending flight. And the lift force is less than the weight during the transition from level flight to constant descending flight. But once the vertical speed becomes constant (whether up or down) the vertical component of lift has to equal the downward force of gravity. If it didn't, then the aircraft would begin _accelerating_ up or down, depending on the difference. Nope, if the airspeed is constant, the lift from the two wings is not the same. This is thought provoking discussion I was hoping to start! Can you see why lift does not equal weight in both cases? Cheers |
#3
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WingFlaps wrote:
On Mar 14, 9:33*am, Jim Logajan wrote: WingFlaps wrote: On Mar 14, 9:11*am, Brian wrote: As for your question above, given that the airplanes are ascending or decending at constant rates then the lift is equal to the wieght of the airplane in both cases. If the aircraft are the same wieght then the lift generated will be the same. That is not correct. Hmmm. Brian's statement appears essentially correct - and you are correct too. The "gotcha" is that the vertical component of the lift force exceeds the weight only during the transition from level flight to constant ascending flight. And the lift force is less than the weight during the transition from level flight to constant descending flight. But once the vertical speed becomes constant (whether up or down) the vertical component of lift has to equal the downward force of gravity. If it didn't, then the aircraft would begin _accelerating_ up or down, depending on the difference. Nope, if the airspeed is constant, the lift from the two wings is not the same. This is thought provoking discussion I was hoping to start! Can you see why lift does not equal weight in both cases? I don't wish to be confrontational since you are looking for thought provoking discussion, but I am pretty sure there is a fair amount of imprecision, and therefore ambiguity, in your statements. This tends to make it difficult to get very far in these discussions. Would it help any if I presented the 2-D equations of force involved? And perhaps you could do the same? |
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On Mar 14, 9:59*am, Jim Logajan wrote:
WingFlaps wrote: On Mar 14, 9:33*am, Jim Logajan wrote: WingFlaps wrote: On Mar 14, 9:11*am, Brian wrote: As for your question above, given that the airplanes are ascending or decending at constant rates then the lift is equal to the wieght of the airplane in both cases. If the aircraft are the same wieght then the lift generated will be the same. That is not correct. Hmmm. Brian's statement appears essentially correct - and you are correct too. The "gotcha" is that the vertical component of the lift force exceeds the weight only during the transition from level flight to constant ascending flight. And the lift force is less than the weight during the transition from level flight to constant descending flight. But once the vertical speed becomes constant (whether up or down) the vertical component of lift has to equal the downward force of gravity. If it didn't, then the aircraft would begin _accelerating_ up or down, depending on the difference. Nope, if the airspeed is constant, the lift from the two wings is not the same. This is thought provoking discussion I was hoping to start! Can you see why lift does not equal weight in both cases? I don't wish to be confrontational since you are looking for thought provoking discussion, but I am pretty sure there is a fair amount of imprecision, and therefore ambiguity, in your statements. This tends to make it difficult to get very far in these discussions. Would it help any if I presented the 2-D equations of force involved? And perhaps you could do the same?- Hide quoted text - Sure here you go: D=drag L=lift W=weight T=thrust alpha=angle of thrust For no acceleration in any plane: W=Tsin(alpha) + L D=Tcos(alpha) What you and many other texts have missed is that the thrust angle changes... What this means is that when you make a plane climb at constant speed you are deliberately reducing lift from from the wing and supplanting it with engine thrust! To extend this idea further, it is not the climb per se that may be the problem but a decaying airspeed... The above equations can be extended to the AOA and airspeed but the conclusion remains the same. Now, what about that tricky updraft? Is this thought provoking :-) Cheers |
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On Mar 13, 1:37 pm, WingFlaps wrote:
Nope, if the airspeed is constant, the lift from the two wings is not the same. This is thought provoking discussion I was hoping to start! Can you see why lift does not equal weight in both cases? Common misconception: that a climbing wing is generating more lift than a descending wing. If the flight paths are both straight lines, whether climbing or descending, the lift is the same in both cases. As Jim said, only a change in the direction of flight will change the lift/weight ratio. A G-meter (such as in our Citabrias) will prove it. If the airspeeds are the same and the flight paths are both straight, the AOAs are both the same, too. But change the speeds while leaving the flight paths alone, and the AOA will change. It's why the airplane has a nose-high attitude in level slow flight as opposed to a lower nose attitude in level cruise. Dan |
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On Mar 14, 1:00*pm, wrote:
On Mar 13, 1:37 pm, WingFlaps wrote: Nope, if the airspeed is constant, the lift from the two wings is not the same. This is thought provoking discussion I was hoping to start! Can you see why lift does not equal weight in both cases? * * * Common misconception: that a climbing wing is generating more lift than a descending wing. If the flight paths are both straight lines, whether *climbing or descending, the lift is the same in both cases. As Jim said, only a change in the direction of flight will change the lift/weight ratio. A G-meter (such as in our Citabrias) will prove it. * * * If the airspeeds are the same and the flight paths are both straight, the AOAs are both the same, too. But change the speeds while leaving the flight paths alone, and the AOA will change. It's why the airplane has a nose-high attitude in level slow flight as opposed to a lower nose attitude in level cruise. Hi Dan see my rely to Jim. In fact, lift is reduced in a steady climb. Cheers |
#7
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On Mar 13, 8:50 pm, WingFlaps wrote:
On Mar 14, 1:00 pm, wrote: On Mar 13, 1:37 pm, WingFlaps wrote: Nope, if the airspeed is constant, the lift from the two wings is not the same. This is thought provoking discussion I was hoping to start! Can you see why lift does not equal weight in both cases? Common misconception: that a climbing wing is generating more lift than a descending wing. If the flight paths are both straight lines, whether climbing or descending, the lift is the same in both cases. As Jim said, only a change in the direction of flight will change the lift/weight ratio. A G-meter (such as in our Citabrias) will prove it. If the airspeeds are the same and the flight paths are both straight, the AOAs are both the same, too. But change the speeds while leaving the flight paths alone, and the AOA will change. It's why the airplane has a nose-high attitude in level slow flight as opposed to a lower nose attitude in level cruise. Hi Dan see my rely to Jim. In fact, lift is reduced in a steady climb. Cheers The trust vector is added to the lift vector in a climb, as the drag is added to weight. Dan Mc |
#8
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On Mar 14, 2:46*pm, Dan wrote:
On Mar 13, 8:50 pm, WingFlaps wrote: On Mar 14, 1:00 pm, wrote: On Mar 13, 1:37 pm, WingFlaps wrote: Nope, if the airspeed is constant, the lift from the two wings is not the same. This is thought provoking discussion I was hoping to start! Can you see why lift does not equal weight in both cases? * * * Common misconception: that a climbing wing is generating more lift than a descending wing. If the flight paths are both straight lines, whether *climbing or descending, the lift is the same in both cases. As Jim said, only a change in the direction of flight will change the lift/weight ratio. A G-meter (such as in our Citabrias) will prove it. * * * If the airspeeds are the same and the flight paths are both straight, the AOAs are both the same, too. But change the speeds while leaving the flight paths alone, and the AOA will change. It's why the airplane has a nose-high attitude in level slow flight as opposed to a lower nose attitude in level cruise. Hi Dan see my rely to Jim. In fact, lift is reduced in a steady climb. Cheers The trust vector is added to the lift vector in a climb, as the drag is added to weight. Are you saying that wing lift does not change with attitude in a non- accelerating frame? Cheers |
#9
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On Mar 13, 9:57 pm, WingFlaps wrote:
On Mar 14, 2:46 pm, Dan wrote: On Mar 13, 8:50 pm, WingFlaps wrote: On Mar 14, 1:00 pm, wrote: On Mar 13, 1:37 pm, WingFlaps wrote: Nope, if the airspeed is constant, the lift from the two wings is not the same. This is thought provoking discussion I was hoping to start! Can you see why lift does not equal weight in both cases? Common misconception: that a climbing wing is generating more lift than a descending wing. If the flight paths are both straight lines, whether climbing or descending, the lift is the same in both cases. As Jim said, only a change in the direction of flight will change the lift/weight ratio. A G-meter (such as in our Citabrias) will prove it. If the airspeeds are the same and the flight paths are both straight, the AOAs are both the same, too. But change the speeds while leaving the flight paths alone, and the AOA will change. It's why the airplane has a nose-high attitude in level slow flight as opposed to a lower nose attitude in level cruise. Hi Dan see my rely to Jim. In fact, lift is reduced in a steady climb. Cheers The trust vector is added to the lift vector in a climb, as the drag is added to weight. Are you saying that wing lift does not change with attitude in a non- accelerating frame? Cheers Of course it does. However -- In a climb thrust acts contrary to drag some component of weight (depending on the angle of climb). Thus the angle of attack is not *necessarily* equal to the angle of climb. Dan Mc |
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