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Spinner strobing as a "Bird Strike Countermeasure"



 
 
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  #11  
Old December 3rd 07, 06:17 AM posted to rec.aviation.piloting,rec.aviation.homebuilt
Mxsmanic
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Default Spinner strobing as a "Bird Strike Countermeasure"

Roger (K8RI) writes:

At cruise RPM that effect would be completely lost. There's not a
bird or human alive that can discern stroboscopic effects of more than
a couple hundred cycles let alone over a 1000. Most of us can't even
discern 60 cps.


Birds have much better vision than human beings, and I don't believe anyone
has tested their ability to discern stroboscopic effects. And the front fan
on a turbofan is turning at around 40-50 revolutions per second, not
thousands.
  #12  
Old December 3rd 07, 06:21 AM posted to rec.aviation.piloting,rec.aviation.homebuilt
Mxsmanic
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Default Spinner strobing as a "Bird Strike Countermeasure"

Maxwell writes:

Seems I have heard the 16 cps is all that is required for movies to appear
continuous.


Motion pictures use 24 ips, repeated once, giving 48 fps (24 images shown
twice each). The motion is smooth as long as the image isn't too bright,
large, or fast-moving. Sometimes a stroboscopic effect can be seen in the
latter cases. It can be hidden by allowing image elements to blur.

You can see this effect very clearly on TV (30 ips in the U.S.) when sporting
events are showing that have been recorded with high shutter rates in the
cameras. Each image is sharp and it's easy to see that a succession of
individual images is being shown on the screen, even at 30 ips.

I think the human eye loosed it around 12 or 13.


Higher than that. Twelve images per second tends to look noticeably jerky.

Hence the reason an aircraft propeller will
appear to be revolving slowly backwards at times.


Not when being observed directly. That only happens in movies and video due
to the interaction between the imaging rate and the rotation rate of the
propeller.
  #13  
Old December 3rd 07, 08:52 AM posted to rec.aviation.piloting,rec.aviation.homebuilt
Maxwell
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Default Spinner strobing as a "Bird Strike Countermeasure"


"Mxsmanic" wrote in message
...
Maxwell writes:

Seems I have heard the 16 cps is all that is required for movies to
appear
continuous.


Motion pictures use 24 ips, repeated once, giving 48 fps (24 images shown
twice each). The motion is smooth as long as the image isn't too bright,
large, or fast-moving. Sometimes a stroboscopic effect can be seen in the
latter cases. It can be hidden by allowing image elements to blur.

You can see this effect very clearly on TV (30 ips in the U.S.) when
sporting
events are showing that have been recorded with high shutter rates in the
cameras. Each image is sharp and it's easy to see that a succession of
individual images is being shown on the screen, even at 30 ips.

I think the human eye loosed it around 12 or 13.


Higher than that. Twelve images per second tends to look noticeably
jerky.

Hence the reason an aircraft propeller will
appear to be revolving slowly backwards at times.


Not when being observed directly. That only happens in movies and video
due
to the interaction between the imaging rate and the rotation rate of the
propeller.


Wrong again you clueless twit.


  #14  
Old December 3rd 07, 08:52 AM posted to rec.aviation.piloting,rec.aviation.homebuilt
Maxwell
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Posts: 1,116
Default Spinner strobing as a "Bird Strike Countermeasure"


"Mxsmanic" wrote in message
...
Roger (K8RI) writes:

At cruise RPM that effect would be completely lost. There's not a
bird or human alive that can discern stroboscopic effects of more than
a couple hundred cycles let alone over a 1000. Most of us can't even
discern 60 cps.


Birds have much better vision than human beings, and I don't believe
anyone
has tested their ability to discern stroboscopic effects. And the front
fan
on a turbofan is turning at around 40-50 revolutions per second, not
thousands.


Guess again.


  #15  
Old December 3rd 07, 11:30 AM posted to rec.aviation.piloting,rec.aviation.homebuilt
Stefan
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Default Spinner strobing as a "Bird Strike Countermeasure"

Wolfgang Schwanke schrieb:

Hz flicker CRT televisions, and most people don't notice it. Americans
who've grown up with 60 Hz NTSC report noticing bad flicker with
European PAL televisions.


But they see at last twice the same colour... :-)
  #16  
Old December 3rd 07, 02:18 PM posted to rec.aviation.piloting,rec.aviation.homebuilt
Yes - I have a name[_2_]
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Default Spinner strobing as a "Bird Strike Countermeasure"

"Mxsmanic" wrote in message
...
And the front fan on a turbofan is turning at around 40-50 revolutions per

second, not
thousands.


My phonograph turns at either 33-1/3 or 45 RPM, which is just as relevant to
this conversation as your mention of turbofans.


  #19  
Old December 3rd 07, 05:01 PM posted to rec.aviation.piloting, rec.aviation.homebuilt
soaringpilot2
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Posts: 9
Default Spinner strobing as a "Bird Strike Countermeasure"


I wonder about doing the candy stripe spiral on them, or painting the blades different colors...



The candy stripe spiral on the spinner was a recognition thing, the
Germans started doing that in the summer of '44. The Japanese did
something similar thru the war years by painting the inboard leading
edge of the wing yellow. Quick recognition by your comrades in a
dogfight when head on...

This is the first I've heard of the 1/3 and 2/3's strobe effect, I
thought it was also for recognition...Maybe I'll try it on my 172...

-Ryan

  #20  
Old December 3rd 07, 07:19 PM posted to rec.aviation.piloting, rec.aviation.homebuilt
[email protected]
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Posts: 83
Default Spinner strobing as a "Bird Strike Countermeasure"


U.S. TV is 60 fields/second, European is 50/second.


And it takes two interlaced fields to make a frame, therefore US
broadcast TV standard (NTSC) is actually only 30 frames per second.
Europe's PAL and SECAM standards are both 50 interlaced fields per
second, yielding 25 actual frames per second.


 




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