Thank you so much for the excellent explanation of the relative airflow on a propeller. I have watched so many videos and I did not get my answer until now. Now, I understand the vectors and the resultant relative airflow for a rotating propeller. I can confidently say that no other video has explained how these vectors are derived.
This is a great video. Very informational and cleared up several misconceptions I had regarding angle of attack vs blade angle. Keep up the great work!
It's just that the rotation in this case as you have shown is anticlockwise or left hand rotation. You have to look at the propeller from inside the cabin. Most of single engine pistons have clockwise rotation, so probably this propeller is also clockwise rotating, which would mean that it is rotating in the other than shown direction. Cheers mate
yea...but air speed is determined thrust/clime/Descent relative to earth/gravity. So to increase air speed- either pinch change (less gravity) or increase in power
I canot understand how the relative airflow is opposite to the propeller motion ? Should the realtive airflow comes from behind the falt side of blades not from the ground as your drawing them ?
I don't understand why the propeller is always drawn pointing so far forward of the plane of rotation (such as at 1:46). Aren't the propeller blades flat with the plane of rotation?
This is the best video I found on the subject thank you! What really got me every time was that cross section diagram with the graphs. I had no clue what part of the propeller we're actually looking at. From what I can understand (and it would REALLY help to have an animation of an airplane going into the position of the graph before disappearing and leaving just that cross section) we are looking at the SIDE of the propeller as the plane is flying in from the right (and thus airspeed coming from the left). Is this correct? Thank you!
I'm not sure that this is correct. But I look at this from a wind turbine perspective but the principles are the same. Angle of attack (i) =Angle of incidence b/w relative wind and direction of motion of the plane (I) - Pitch angle (alpha). Given that the pitch angle remains the same an increase in I will increase the AoA. This is done via increasing wind speed or increasing plane velocity. Is this correct. Im unsure about propeller planes but can the pitch of the blades vary accordingly to optimise the AoA(i) so as to optimise Fd/Fl
How we have to Check the Direction of propeller rotation. Whether it is Clockwise or anti clockwise. From which position we have to check? I mean. by Standing infront of a/c or Sitting in pilot Seat?
So the final question to tie this all together.. can a Fixed pitch propeller, operating normally (no malfunctions), engine operating normally to spin the prop, etc…..Can it stall?
Why don't we have compact telescopic 3 tears propeller blades today for use in PAV's ( personal air vehicles) so that they can be extended in flight and retracted for driving on the ground ? For a real life all terrain vehicle?
Yes, it is drawn incorrectly. I only noticed it after I’d posted and fully intended to remake the video. It’s now years later and I still ave great intentions of remaking it. 😀
First you mention Greenarrow upside inclined. it satisfies vector addition triangle.second time you mentioned Green arrow downside inclined it didn't satifies vector addition. it confuse me. please explain .Thank you.
Amazing video Thanks. I had a doubt though , So the angle of attack at tip of the propeller would change because it moves at a higher angular velocity that the root of the , Blade correct? If not can someone clear this doubt for me ?
No, the blade angle at the tip is smaller because the rotational velocity (V) is greater at the tip. The angular velocity ( omega) is the same all along the blade. The equation is: V = omega.radius At the tip the radius is at the maximum so the velocity is at the maximum.
So my textbook explain it right too but instead of talking about movement of airflow it use RPM and foward speed of the aircraft... Which is the incorrect way to explain the relative airflow.
Vertical speed is a result of higher propeller RPM that line is the measurement in force hitting the bottom of the airfoil. The lengths of the lines are 2d representation of the amount pressure exerting on the airfoil as the propeller moves faster or slower in that clockwise direction (vertical) or forward in airspeed (horizontal)
Thank you Roddy, I was refering to last few seconds of the video, there is both decrease increase. Yup, speed up = angle of attack going down:) thanks for the video! Well made!
How are you increasing RPM? Are you increasing the power to the engine, then there will be an increase in power delivered by the propeller, or are you increasing RPM by selecting a more fine blade angle?
*Assuming a fix pitched propeller for simplicity.* An increase in RPM does not necessarily assume an increase in airspeed. For example, slow flight relies upon pitch for airspeed and power for altitude.
@@RoddyMcNamee Hi, i have the same question. why increase the RPM but the airspeed is the same? I didn't understand from your reply. Could you please explain more??
This is WRONG. Propellers SUCK AIR IN, as well as rotate, as well as are connected to a usually-moving thing, like an airplane. This video only considers the last two, and not the fact that the air is being sucked in in the first place. This was almost certainly left out deliberately - the shape of the blade and the angle of attack determines it's efficiency, which determines how much air it sucks in, which gets ugly. The angle-of-attack determines the airflow, AND the airflow determines the angle of attack - at some point an equilibrium is reached, which is highly non-trivial. You simply can't simplify this concept like Roddy did here.
13 years on and this has just helped me massively for my POF exam ! Thankyou 😊
Thank you! So much easier to understand visually than from a textbook
Seriously you've done a great job explaining this, keep going
Thank you so much for the excellent explanation of the relative airflow on a propeller. I have watched so many videos and I did not get my answer until now. Now, I understand the vectors and the resultant relative airflow for a rotating propeller. I can confidently say that no other video has explained how these vectors are derived.
Absolutely! The direction of the relative airflow should be pointing towards the propeller and not away from it!
Definitely the best explanation with proper visuals! Thank you Roddy
What a beautifully paced and well structured video this is. Many thanks for all your hard work.
this is what i was looking for. Now i can understand the other aspects of propeller blade bitting the air, blade and pitch. Thank you very much
Thank you so much. I am working on CFI. I was trying to find this perfect explanation for a while. Finally I got it here. Good Job!
This is a great video. Very informational and cleared up several misconceptions I had regarding angle of attack vs blade angle. Keep up the great work!
Cristal clear explanation. Thank you so much for putting this together
Amazing explanation! Simple, clear and precise
I ve been researching that for a whole week, thanks mate
Roddy, thanks so much for this video. This is the first time that I actually understand how the different forces changes the Aoa
It's just that the rotation in this case as you have shown is anticlockwise or left hand rotation. You have to look at the propeller from inside the cabin. Most of single engine pistons have clockwise rotation, so probably this propeller is also clockwise rotating, which would mean that it is rotating in the other than shown direction. Cheers mate
Thanks so much ! This help me to visualise AOA of propeller which is much more clear than those text books !
Thanks man...the way u explained made me understand everything in 4 mins..which I wasn't being able to do by going thru the book fr hours
Wow, ive been looking for a video like this for a while. Finally i understand this. thanks!!!
just to check, the relative air flow should be pointing opposite (as in pointing towards upper right corner)?
Best explanation I have ever seen, thanks so much....
Dudee, thank you so much.. You have no idea how it got simple after i watch yur video...
Sir, thank you very much, from you i understood how the propeller works.
Thank you so much you explained it so well with those clearly-illustrated diagrams
wow best explanation i was confused now its all clear thank you so much🙏🙏
yea...but air speed is determined thrust/clime/Descent relative to earth/gravity. So to increase air speed- either pinch change (less gravity) or increase in power
A very very clear presentation
YES. UGH YOURE BETTER THAN MY INSTRUCTOR. THANK U
Great, well explained. Good for PPL learning.
I canot understand how the relative airflow is opposite to the propeller motion ? Should the realtive airflow comes from behind the falt side of blades not from the ground as your drawing them ?
For me the cross section of the blade looks wrong for a clockwise rotating prop and the airflow direction vectors you show. Maybe its just me......
AviationMy, sorry for the tardy resonse, but I''Ve just seen your comment. For me, Blade Angle and Blade Pitch are the same thing.
Superb sir.
Hats off to your explanation..
Thank u so much
very good explanation.
Thanks for the feedback
Cheers man! I didn't understand it at PPL theory, but thanks to you I do!
A Short clip and so useful , Thank u very much :)
Thanks. It is very clear. Way to go!
I don't understand why the propeller is always drawn pointing so far forward of the plane of rotation (such as at 1:46). Aren't the propeller blades flat with the plane of rotation?
Perfectly explanation!!!! Cheers
very well illustrated thanks man..
at the end, i think there is a typo error with "a decrease increase in AoA". Need to remove 'increase'. You have simplified a hard stuff.
This is the best video I found on the subject thank you! What really got me every time was that cross section diagram with the graphs. I had no clue what part of the propeller we're actually looking at.
From what I can understand (and it would REALLY help to have an animation of an airplane going into the position of the graph before disappearing and leaving just that cross section) we are looking at the SIDE of the propeller as the plane is flying in from the right (and thus airspeed coming from the left). Is this correct? Thank you!
Yes, the cross section is of the propeller blade looking in from the side, with the aircraft flying from right to left.
I'm not sure that this is correct. But I look at this from a wind turbine perspective but the principles are the same. Angle of attack (i) =Angle of incidence b/w relative wind and direction of motion of the plane (I) - Pitch angle (alpha). Given that the pitch angle remains the same an increase in I will increase the AoA. This is done via increasing wind speed or increasing plane velocity. Is this correct.
Im unsure about propeller planes but can the pitch of the blades vary accordingly to optimise the AoA(i) so as to optimise Fd/Fl
Thank you so much you explained it so well!
How we have to Check the Direction of propeller rotation. Whether it is Clockwise or anti clockwise. From which position we have to check? I mean. by Standing infront of a/c or Sitting in pilot Seat?
Standing behind the aircraft and looking forward.
@@RoddyMcNamee thank you Sir!
Thank you so much!!! Finally I got it!!!
Great video
Superb explanation.
So the final question to tie this all together.. can a Fixed pitch propeller, operating normally (no malfunctions), engine operating normally to spin the prop, etc…..Can it stall?
In flight, I would say the answer is no, it is very unlikely to stall.
Very clear explanation indeed
Angle of Attack ??? what does it effect
Why don't we have compact telescopic 3 tears propeller blades today for use in PAV's ( personal air vehicles) so that they can be extended in flight and retracted for driving on the ground ? For a real life all terrain vehicle?
Well explained, thank you
Elaborate what would be the effect when both acts at the same time sir...this video was really helpful, still there are some doubts
Yes perfect explanation!!!
Very well explained.
Great explanation thank you
At 1:44 , the direction of relative airflow vector is incorrect. It should be opposite to what you have drawn. Great explanation though.
Yes, it is drawn incorrectly. I only noticed it after I’d posted and fully intended to remake the video. It’s now years later and I still ave great intentions of remaking it. 😀
@@RoddyMcNamee Naah , it’s a great video. Why spend time on it when you can make one on a different topic for us :)
This one is great
Made perfect sense. Thank you.
thanks, i was going to claw my eyes out playing flyout
Omg thank you!! You literally saved my ass!!!
Thanks a lot. Bristol Atpl books are far away of fully understable explanation in principles of flight and other subjects :((
Thank you I couldn't learn this in my college
Hi I want to ask, in aircraft if blade angle increase what happened to the propeller blade pitch? (increase or decrease)
Awesome! Just what I was lloking for! Thanks sir! :-)
what happens if the air speed is constant
You're welcome. Glad it was of some use.
Have a look at another screencast I made about blade asymmetric loading. If that doesn't help, come back to me.
When he says tree blade propeller and you think wow what a funny accent and then you remember that no wait tree is actually how you say it
That relative wond component is wrong, please correct it. By the way the video is informative, Thankyou.
First you mention Greenarrow upside inclined. it satisfies vector addition triangle.second time you mentioned Green arrow downside inclined it didn't satifies vector addition. it confuse me. please explain .Thank you.
The green vector (relative airflow) is pointing in the wrong direction. It should point upwards.
Roddy Mc Namee Thank you. I was confused about this part. Otherwise very good explanation!
Sir, can u tell me how this value of "vector due to rotational speed" is obtained ? is this actually the centrifugal force acting on the blades?
No, it is the velocity vector due to the rotational speed. V= omega.r. where omega is the rotational speed in radians per second.
@@RoddyMcNamee oh u mean angular velocity ?
Amazing video Thanks. I had a doubt though , So the angle of attack at tip of the propeller would change because it moves at a higher angular velocity that the root of the , Blade correct?
If not can someone clear this doubt for me ?
No, the blade angle at the tip is smaller because the rotational velocity (V) is greater at the tip. The angular velocity ( omega) is the same all along the blade. The equation is:
V = omega.radius
At the tip the radius is at the maximum so the velocity is at the maximum.
Thank you
great job!
If the airspeed increases, AoA decreases. How can we increase the airspeed?
Put the aircraft into a dive.
@@RoddyMcNamee I see, make sense.
Thank You...nice and simple...
easy to understand Thank you
So my textbook explain it right too but instead of talking about movement of airflow it use RPM and foward speed of the aircraft... Which is the incorrect way to explain the relative airflow.
The relative airflow is the vector sum of forward speed and prop airflow due to RPM. So there is no difference in how they are being explained.
I did not understand the vertical speed. From where it comes from? 😔
Vertical speed is a result of higher propeller RPM that line is the measurement in force hitting the bottom of the airfoil.
The lengths of the lines are 2d representation of the amount pressure exerting on the airfoil as the propeller moves faster or slower in that clockwise direction (vertical) or forward in airspeed (horizontal)
thanks m8. thats very helpful
And what is the ideal angle of attack ?
It depends on the prop, but usually the best lift / drag ratio of an airfoil occurs at about 4 degrees.
BRILLIANT
If the airspeed increases, this will cause a DECREASE INCREASE in angle of attack? Please DECREASE or INCREASE?
All other things being equal (Blade angle, RPM), as airspeed increases, angle of attack will DECREASE.
Thank you Roddy, I was refering to last few seconds of the video, there is both decrease increase. Yup, speed up = angle of attack going down:) thanks for the video! Well made!
"Tree bladed propeller". I assume its a wooden one then?
straight fire
Thanks Roddy. I presume this is for a fixed propeller?
Yes, this was for a fixed pitch propeller but the principle can still be applied to a variable pitch prop.
If you increase the RPM therefore increasing the speed, how would it affect the AOA?
How are you increasing RPM? Are you increasing the power to the engine, then there will be an increase in power delivered by the propeller, or are you increasing RPM by selecting a more fine blade angle?
*Assuming a fix pitched propeller for simplicity.* An increase in RPM does not necessarily assume an increase in airspeed. For example, slow flight relies upon pitch for airspeed and power for altitude.
@@RoddyMcNamee Hi, i have the same question. why increase the RPM but the airspeed is the same? I didn't understand from your reply. Could you please explain more??
great job ,thanks
very useful..thank you very much...more videos on gas turbine please:)
I SUBSCRIBED
Is there a video of solving the aoa?
There are some videos called Propeller Analysis 1, 2 and 3. If they’re not helpful I’ll do one for you next week.
@@RoddyMcNamee you're the best!
@@comctrevor864 have a look at this: ruclips.net/video/CaVINtjMIqo/видео.html is this what you were looking for?
GOD DAWM thanks finaly i understand !
nice one propeller blade ................i understand
Thanks
finally!
Well I suppose on the bright side it wasn't BORRRRRING.
You're welcome.
This is WRONG. Propellers SUCK AIR IN, as well as rotate, as well as are connected to a usually-moving thing, like an airplane. This video only considers the last two, and not the fact that the air is being sucked in in the first place. This was almost certainly left out deliberately - the shape of the blade and the angle of attack determines it's efficiency, which determines how much air it sucks in, which gets ugly. The angle-of-attack determines the airflow, AND the airflow determines the angle of attack - at some point an equilibrium is reached, which is highly non-trivial.
You simply can't simplify this concept like Roddy did here.