Riddle me this.......
05-19-2007 | 06:06 AM
#1
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05-19-2007 | 06:14 AM
#2
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From: Jump
That's a cool illusion.
That video must have been shot with a video camera that has a frame rate with the same speed as the rotation rate of the main rotor. It would give the illusion that the main rotor is standing still.
You can see that the tail rotor appears to be rotating slowly which means it is at a slightly different rate from which the camera is filming.
You can definitely hear the sound of the rotating blades in the audio, so you know they're turning and not standing still.
You can also get this illusion with airplane propellers.
That video must have been shot with a video camera that has a frame rate with the same speed as the rotation rate of the main rotor. It would give the illusion that the main rotor is standing still.
You can see that the tail rotor appears to be rotating slowly which means it is at a slightly different rate from which the camera is filming.
You can definitely hear the sound of the rotating blades in the audio, so you know they're turning and not standing still.
You can also get this illusion with airplane propellers.
05-19-2007 | 08:29 AM
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From: B777
05-19-2007 | 02:08 PM
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From: ATP, CFI etc.
Actually both. The frame rate has to be equal to keep up with the position of the blades, or a multiple thereof, and the shutter speed has to be shorter or equal so that blurring does not occur. Since video chips do not have shutters, I suspect video cleanup processing is involved using some kind of software. The fact the pilot is gradually rotating the helicopter has nothing to do with it, but serves to distract the viewer in a deliberate attempt to delude the viewer. If the helicopter chassis were moving quickly across the screen doing fast manuevers such as banking and turning, the illusion of still blades standing still would be more impressive.
My avatar was shot while the turbine was running (just joking).
My avatar was shot while the turbine was running (just joking).
Last edited by Cubdriver; 05-19-2007 at 02:35 PM.
05-19-2007 | 08:36 PM
#7
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From: CRJ left
Question for helicopter experts..... Does the main rotor of a turbine helicopter maintain a contant RPM during those types of maneuvers? I have seen similar videos where the shutter speed equals the RPM and the blades appear stationary, but usually that does not last more than a second or two as the RPM changes....
05-24-2007 | 03:02 AM
#9
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From: Body at sea level; heart at 70,000+
Long time ago I flew an Aero-commander with "poilished" props. To "sync" them we looked at the reflection of the right prop in the left prop. Moved the prop lever until the right one "Stopped." Then they were synchronized.
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