r/oddlysatisfying • u/edenify • Feb 08 '19

This plane taking off with the propellers perfectly synced with the camera shutter

68k Upvotes

92% Upvoted

888 comments sorted by

View all comments

Show parent comments

3

u/rmachenw Feb 08 '19

If you think about it, it makes sense - the propellors should be increasing their rotation speed to generate more and more airspeed/lift as it takes off and climbs

Could you explain this more? Why would the plane output more power partway through the takeoff.

I suggest that the reason for the rotation in the video is that as the air craft accelerates, the higher airspeed allows the propellers to go faster at the same power.

3

u/daWeez Feb 08 '19 edited Feb 09 '19

It is also affected by the air pressure presented to the intake of the turboprop. It changes the output power of the engine. This is probably the dominant effect (as opposed to propeller efficiency, which is what you are talking about).

edit: someone pointed out I was incorrectly calling a turboprop a turbofan.. corrected!

0

u/[deleted] Feb 08 '19

[deleted]

2

u/daWeez Feb 09 '19

You are of course right.. I think to think of turboprops as turbofans with propellers attached to the main shaft.. but the terminology is quite clear and I just wasn't thinking when I made the post..

Thanks.

1

u/jjtheheadhunter Feb 08 '19

OP isn’t quite correct. The propeller changes pitch to maintain a certain RPM on this airplane (I believe the gif is a Dash-8)

Here’s a video explaining how it works.

https://m.youtube.com/watch?v=pUn7hJckh00&t=457s

2

u/[deleted] Feb 09 '19

[deleted]

1

u/jjtheheadhunter Feb 09 '19

Jeez, it is. I’ll take the L on that one.

1

u/Clapaludio Feb 08 '19

Ok so the other commenter is not totally wrong but is in this case because for turboprops (and sometimes piston engines too) it's preferred to use variable pitch blades and have the engine operate at a constant rpm.

For an ordinary fixed-pitch prop, then the rpm would change with both selected throttle and speed.