Ben2000
2nd Apr 2024, 21:20
Hi all,
So, hopefully, I'll get somewhere with this question. I did get some help on another forum, and then the question bank threw me off completely. From the Oxford books, this is what I get (sorry, can't seem to post images):As the aircraft accelerates, air speed will increase, causing a decrease in the angle of attack of the blades. Less thrust and less propeller torque will be generated.
But then the question bank ...
As an aircraft with a variable-pitch, constant-speed propeller accelerates along the runway:
[A] The blade pitch angle increases, maintaining a constant angle of attack and R.P.M. ✅
The angle of attack will remain constant and the engine R.P.M. will increase.
[C] The linear velocity of the propeller tip will gradually decrease.
[D] The angle of attack will decrease and the engine R.P.M. remain constant.
So, what exactly is it? I tried to deduce the answer, i.e. compare with a fixed-pitch prop, as the aircraft accelerates, the relative wind angle changes (moves forward), therefore the AoA decreases. OK.
With a constant speed, I select an RPM say, 2500. When I start to accelerate, then due to the forward speed, the blade tries to rotate faster > this causes the CSU to slow it down, making it more coarse to reduce and control the RPM, so again the blade pitch angle will increase, and maintain a constant RPM.
Is that correct? What will cause the blade to rotate faster when accelerating? And what happens to the AoA?
Many thanks for your help!
So, hopefully, I'll get somewhere with this question. I did get some help on another forum, and then the question bank threw me off completely. From the Oxford books, this is what I get (sorry, can't seem to post images):As the aircraft accelerates, air speed will increase, causing a decrease in the angle of attack of the blades. Less thrust and less propeller torque will be generated.
But then the question bank ...
As an aircraft with a variable-pitch, constant-speed propeller accelerates along the runway:
[A] The blade pitch angle increases, maintaining a constant angle of attack and R.P.M. ✅
The angle of attack will remain constant and the engine R.P.M. will increase.
[C] The linear velocity of the propeller tip will gradually decrease.
[D] The angle of attack will decrease and the engine R.P.M. remain constant.
So, what exactly is it? I tried to deduce the answer, i.e. compare with a fixed-pitch prop, as the aircraft accelerates, the relative wind angle changes (moves forward), therefore the AoA decreases. OK.
With a constant speed, I select an RPM say, 2500. When I start to accelerate, then due to the forward speed, the blade tries to rotate faster > this causes the CSU to slow it down, making it more coarse to reduce and control the RPM, so again the blade pitch angle will increase, and maintain a constant RPM.
Is that correct? What will cause the blade to rotate faster when accelerating? And what happens to the AoA?
Many thanks for your help!