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#71
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Spinner strobing as a "Bird Strike Countermeasure"
"Gig 601XL Builder" wrDOTgiaconaATsuddenlink.net wrote in
: cavelamb himself wrote: STANDARD FLAME POST version 3.432 (c) 1996-1997. Check all that apply. I hadn't seen that in a long time. You need to update though to the 4.0(rec.aviation) version. It replaces all of that with. Shut the **** up, MX. Bwawhahwhahhwahwh! Bertie |
#72
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Spinner strobing as a "Bird Strike Countermeasure"
In a previous article, "Yes - I have a name" said:
I'm sure I've seen wheels on cars that appear to be moving backwards. Are my eyes defective? That's due to something else strobing the light, such as the reflection off other wheels or off the lugnuts. It's also reported that a steady vibration of your eyes can cause the effect, such as when humming (or probably while sitting in a noisy airplane). http://findarticles.com/p/articles/m...17/ai_18471030 The discrete vision theory has been discredited. Kline K, Holcombe A, Eagleman D (2004). "Illusory motion reversal is caused by rivalry, not by perceptual snapshots of the visual field.". Vision Res 44 (23): 2653-8. PMID 15358060. Kline K, Holcombe A, Eagleman D (2006). "Illusory motion reversal does not imply discrete processing: Reply to Rojas et al.". Vision Res 46 (6-7): 1158-9. PMID 16199075 -- Paul Tomblin http://blog.xcski.com/ C is *supposed* to be dangerous, damnit! -- Anonymous, on "Safer C" |
#73
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Spinner strobing as a "Bird Strike Countermeasure"
"Paul Tomblin" wrote in message
... That's due to something else strobing the light, such as the reflection off other wheels or off the lugnuts. So Anthony's statement IS wrong : "it never appears to move backwards." Refer to MX rule #1 |
#74
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Spinner strobing as a "Bird Strike Countermeasure"
Gig 601XL Builder wrote:
cavelamb himself wrote: STANDARD FLAME POST version 3.432 (c) 1996-1997. Check all that apply. I hadn't seen that in a long time. You need to update though to the 4.0(rec.aviation) version. It replaces all of that with. Shut the **** up, MX. Dude! That's sweet. Direct, to the point, and saves considerable bandwidth. Wish this idiot could do the same. But Noooooo.... Not this one. Ah well. Richard |
#75
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Spinner strobing as a "Bird Strike Countermeasure"
In rec.aviation.piloting Mxsmanic wrote:
writes: Any light that flickers at an appropriate rate will cause the prop to appear to turn in reverse. The likelyhood of being somewhere with lights that flicker is irrelevant. It's highly relevant in aviation, where exposure to flickering lights is essentially unknown. A new appearance of Non Sequitur Kid. The original statement was that it -ONLY- happens in movies and video, and that absolute statement is false as are most of MX's absolute statements. The original assertion was that it was an artifact of human vision, which is never true. The Revisionist appears to pull MX's butt from the fire and fails. You do know this stuff is archived and it is trivial to show you are lying? -- Jim Pennino Remove .spam.sux to reply. |
#76
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Spinner strobing as a "Bird Strike Countermeasure"
In rec.aviation.piloting Mxsmanic wrote:
writes: When observed directly under artifical light that "flickers", the most obvious being a strobe light, but there are other types of artificial lights that have flicker. That is an artifact of the lighting, not of human vision. Non Sequitur Kid suddenly appears... Additionally, natural light (e.g., sunlight) does not flicker. Captain Obvious puts in yet another appearance. -- Jim Pennino Remove .spam.sux to reply. |
#77
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Spinner strobing as a "Bird Strike Countermeasure"
In rec.aviation.piloting Mxsmanic wrote:
Yes - I have a name writes: My phonograph turns at either 33-1/3 or 45 RPM, which is just as relevant to this conversation as your mention of turbofans. At any given moment there are thousands of aircraft powered by turbofans in flight. The Non Sequitur Kid puts in a surprise appearance. Yet he fails to state that at any given moment there are thousands of phonographs in use. -- Jim Pennino Remove .spam.sux to reply. |
#78
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Spinner strobing as a "Bird Strike Countermeasure"
On Dec 3, 7:21 pm, Harry K wrote:
On Dec 3, 2:45 pm, Just go look it up! wrote: On Mon, 03 Dec 2007 21:52:04 -0800, Airbus wrote: In article , says... When observed directly under artifical light that "flickers", the most obvious being a strobe light, but there are other types of artificial lights that have flicker. -- Fine - but which ones cause you to see the propellers turning in apparent reverse? Do you frequently operate your airplane indoors? Propellers are usually observed in natural light, which does not flicker. At night, on the rare occasions where you actually see the props clearly, it is from the aircraft's own lighting, which is DC. I have nbever seen the props turning backwards on a real plane - see it frequently in movies though. . . Night, near one of those big off-amber ramp lights, run the RPM up and down, there's a range where it will look like it's going backwards. I thought it was kind of interesting. It's something similar to the poor-man's "is my RPM somewhat right" test, it'll appear stopped at (I forget what RPM now) RPM and if your tach is somewhat near, viola.- Hide quoted text - - Show quoted text - Been a long, long time but my rusty math skills says it would be about 3600 unless I am wrong (per wife that is my normal state). That is the 1/2 harmonic of the rpm/flicker rate. 60 X 120 = 7200. The phenomenon should appear at 1/2, 1/4, double rate etc intervals. Harry K- Hide quoted text - - Show quoted text - After thinking that over... It gets worse. There will be multiple rpm that will show the effect under strobe conditions. With a 2 blade prop it can be sychronizing every 1/2 rev. 3-blade prop every 1/3 or 2/3 rev, etc. in addition to synching on the harmonics. Harry K |
#79
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Spinner strobing as a "Bird Strike Countermeasure"
If any of you have tried to use a strobe light to determine rotational
speed, you'll remember harmonics are a serious problem. If there's a single mark on a shaft, it will appear stationary if the flash rate is equal to the time it takes the shaft to turn once. It will also appear stationary if its rate is half of that time, (it will blink on the spot every other time) a quarter of that time, and so on. It gets worse. If the blink rate is twice that of the shaft speed, the spot will appear stationary, but only half as intense, since one flash will 'lock' the spot, and the next will illuminate the opposite side of the shaft at an unmarked place. To make this relevant to aviation, replace spot with prop blade. On Dec 4, 11:17 am, Harry K wrote: On Dec 3, 7:21 pm, Harry K wrote: On Dec 3, 2:45 pm, Just go look it up! wrote: On Mon, 03 Dec 2007 21:52:04 -0800, Airbus wrote: In article , says... When observed directly under artifical light that "flickers", the most obvious being a strobe light, but there are other types of artificial lights that have flicker. -- Fine - but which ones cause you to see the propellers turning in apparent reverse? Do you frequently operate your airplane indoors? Propellers are usually observed in natural light, which does not flicker. At night, on the rare occasions where you actually see the props clearly, it is from the aircraft's own lighting, which is DC. I have nbever seen the props turning backwards on a real plane - see it frequently in movies though. . . Night, near one of those big off-amber ramp lights, run the RPM up and down, there's a range where it will look like it's going backwards. I thought it was kind of interesting. It's something similar to the poor-man's "is my RPM somewhat right" test, it'll appear stopped at (I forget what RPM now) RPM and if your tach is somewhat near, viola.- Hide quoted text - - Show quoted text - Been a long, long time but my rusty math skills says it would be about 3600 unless I am wrong (per wife that is my normal state). That is the 1/2 harmonic of the rpm/flicker rate. 60 X 120 = 7200. The phenomenon should appear at 1/2, 1/4, double rate etc intervals. Harry K- Hide quoted text - - Show quoted text - After thinking that over... It gets worse. There will be multiple rpm that will show the effect under strobe conditions. With a 2 blade prop it can be sychronizing every 1/2 rev. 3-blade prop every 1/3 or 2/3 rev, etc. in addition to synching on the harmonics. Harry K- Hide quoted text - - Show quoted text - |
#80
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Spinner strobing as a "Bird Strike Countermeasure"
In rec.aviation.piloting Harry K wrote:
On Dec 3, 7:21 pm, Harry K wrote: On Dec 3, 2:45 pm, Just go look it up! wrote: On Mon, 03 Dec 2007 21:52:04 -0800, Airbus wrote: In article , says... When observed directly under artifical light that "flickers", the most obvious being a strobe light, but there are other types of artificial lights that have flicker. -- Fine - but which ones cause you to see the propellers turning in apparent reverse? Do you frequently operate your airplane indoors? Propellers are usually observed in natural light, which does not flicker. At night, on the rare occasions where you actually see the props clearly, it is from the aircraft's own lighting, which is DC. I have nbever seen the props turning backwards on a real plane - see it frequently in movies though. . . Night, near one of those big off-amber ramp lights, run the RPM up and down, there's a range where it will look like it's going backwards. I thought it was kind of interesting. It's something similar to the poor-man's "is my RPM somewhat right" test, it'll appear stopped at (I forget what RPM now) RPM and if your tach is somewhat near, viola.- Hide quoted text - - Show quoted text - Been a long, long time but my rusty math skills says it would be about 3600 unless I am wrong (per wife that is my normal state). That is the 1/2 harmonic of the rpm/flicker rate. 60 X 120 = 7200. The phenomenon should appear at 1/2, 1/4, double rate etc intervals. Harry K- Hide quoted text - - Show quoted text - After thinking that over... It gets worse. There will be multiple rpm that will show the effect under strobe conditions. With a 2 blade prop it can be sychronizing every 1/2 rev. 3-blade prop every 1/3 or 2/3 rev, etc. in addition to synching on the harmonics. It isn't that bad. Synchronization only occurs on integral fractions and engine RPM is usually 1000 and about 2700 RPM so the possibilities are limited. For a 2 bladed prop: 7200/2= 3600 - 1800 RPM 7200/3= 2400 - 2400 RPM and 1200 RPM 7200/4= 1800 - 1800 RPM and 900 RPM etc. I leave it to someone else to show how many blades you see at each RPM. -- Jim Pennino Remove .spam.sux to reply. |
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