Whats With The Flashing Lights
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Whats With The Flashing Lights
Good evening all.
Just wondering if anyone can "illuminate" me as to the reason why the inboard ie in the wing landing lights on 737-800's flash alternately bit like police cars.
I noticed it the other day but it seems only approach coming down North East Rd Adelaide and either taxiing or taking off.
They do not appear to be flashing when first illuminated on descent.
Probably has been covered in a thread previous or elsewhere, but it's tweaked my interest.
As usual
Rock on!
Just wondering if anyone can "illuminate" me as to the reason why the inboard ie in the wing landing lights on 737-800's flash alternately bit like police cars.
I noticed it the other day but it seems only approach coming down North East Rd Adelaide and either taxiing or taking off.
They do not appear to be flashing when first illuminated on descent.
Probably has been covered in a thread previous or elsewhere, but it's tweaked my interest.
As usual
Rock on!
Sprucegoose
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It is meant to reduce bird strikes, apparently it has had little or no effect!
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The theory is that a bird (supposedly) can't see an object that maintains a relative position to it. The occulting (flashing) landing lights are supposed to create the illusion of a change in relative position. And of course, every one knows that birds always fly in straight lines, thus maintaining a constant relative position. 
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Occulting flashing
Capt.Claret, sorry to be nitpick but navigation wise, a flashing light is when the period of darkness (inbetween flashes) is longer thanthe period of light and occulting is the reverse, when the period of darkness is shorter than that of light..........if you see what I mean
Nunc est bibendum
Gannet, what if they're on and off for the same amount of time? By your definition they're neither flashing or occulting. 
Having seen them I'd agree with Clarrie that they're occulting. The period of total darkness in each lens is less than period during which you'll see light!
Having seen them I'd agree with Clarrie that they're occulting. The period of total darkness in each lens is less than period during which you'll see light!
They are called PulseLites.
On the Dash they definately increase lamp life, not changing as many these days.
Easy to see the aircraft, as for birdstrikes - manufacturer claims 20-30% reductions in murdered birdies, reality shows them trending up but that could be due to other environmental factors like the drought.
The Pulselites can also be wired to pulse if you get a TCAS TA - but it's not implemented on the Dash, dunno about the other aircraft.
On the Dash they definately increase lamp life, not changing as many these days.
Easy to see the aircraft, as for birdstrikes - manufacturer claims 20-30% reductions in murdered birdies, reality shows them trending up but that could be due to other environmental factors like the drought.
The Pulselites can also be wired to pulse if you get a TCAS TA - but it's not implemented on the Dash, dunno about the other aircraft.
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Flashing Keg
Interesting point and this is drifting a bit from the thread but on navigation charts at sea lights are either flashing or occulting, in either red green or white, never equal time on and off.
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The theory is that a bird (supposedly) can't see an object that maintains a relative position to it. The occulting (flashing) landing lights are supposed to create the illusion of a change in relative position.
Sprucegoose
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yes it has been proven to distract birds,
How do they affect landing at night? Or is the fact that they are 'occulting' (thanks Clarrie and Keg) providing enough light?
Cheers, HH.
As to whether they are flashing of occulting both Keg and Claret are INCORRECT the lights are actually always on. 
they just dim very substantially (like standing at home and rotating the dimmer knob quickly) as having them go constantly on/off as opposed to fade to dim then increase to bright would definitely shorten the bulb life. Whereas by dimming you get the same effect but with extended life. As the effect on birds I haven't noticed any real difference. They are however more visible than steady lights especially during daylight.
the lights are actually always on. they just dim very substantially (like standing at home and rotating the dimmer knob quickly) as having them go constantly on/off as opposed to fade to dim then increase to bright would definitely shorten the bulb life. Whereas by dimming you get the same effect but with extended life. As the effect on birds I haven't noticed any real difference. They are however more visible than steady lights especially during daylight.
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I have flown in several places where the aircraft were fitted with alternating landing lights -always for the same reason: Visibility.
As I would expect most of you to know, it can be extremely difficult to pick up other aircraft against ground clutter and awkward lighting conditions in high traffic density areas and in the vicinity of airports. The alternating lights are a tremendous aid. I've never before heard of their use in the context of bird-strike, but I am not going to discount the possibility that it may be of some benefit.
Wasn't there a thread here a few months ago with someone questioning the use of landing lights during daylight hours? That sparked quite a lively discussion which is probably quite relevant to this one..
As I would expect most of you to know, it can be extremely difficult to pick up other aircraft against ground clutter and awkward lighting conditions in high traffic density areas and in the vicinity of airports. The alternating lights are a tremendous aid. I've never before heard of their use in the context of bird-strike, but I am not going to discount the possibility that it may be of some benefit.
Wasn't there a thread here a few months ago with someone questioning the use of landing lights during daylight hours? That sparked quite a lively discussion which is probably quite relevant to this one..
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They also make the aircraft easier to see for other pilots, which goes to prove that pilots are bird brained.
and then of course there is this little bewdy.
Accession Number : AD0295085
Title : AN INVESTIGATION OF THE EFFECTS OF PULSED LIGHTING UPON AIRCRAFT DISPLAYS RELATIVE TO THE PRESERVATION OF DARK ADAPTATION FOR NIGHT FLYING
Corporate Author : DOUGLAS AIRCRAFT CO INC LONG BEACH CALIF
Personal Author(s) : UYEDA,L.R. ; LEVEDAHL,B.H.
Report Date : 18 JUL 1962
Pagination or Media Count : 1
Abstract : THE RELATIONSHIP OF PULSED AND CONTINUOUS LIGHTING UPON A COMPENSATORYTASK, AND ITS SUBSEQUENT EFFECT ON SCOTOPIC DETECTION PERFORMANCE WAS EXAMINED UNDER TWO LEVELS OF ILLUMINATION. RESPONSE LATENCY OF DETECTING LANDOLT RINGS AS WELL AS THE NUMBER OF DETECTION ERRORS INCURRED WAS AN INDEX OF THE TIME REQUIRED TO EFFECTIVELY REGAIN DARK ADAPTATION. ON THE BASIS OF THE RESULTS OBTAINED, IT IS CONCLUDED THAT DARK ADAPTATION MAY BE PRESERVED IF THE VISUAL DISPLAY TO WHICH AN INDIVIDUAL IS ATTENDING IS ILLUMINATED WITH PULSED LIGHTING IN THE FREQUENCY RANGE OF 5 TO 15 CPS. IN THIS CONDITION, THE EXPERIMENTAL VEHICULAR TRACKING PERFORMANCE APPEARS UNIMPAIRED
Descriptors : *INSTRUMENT PANELS, ADAPTATION(PHYSIOLOGY), AIRCRAFT, BRIGHTNESS, DISPLAY SYSTEMS, HUMAN FACTORS ENGINEERING, LIGHT PULSES, NIGHT FLIGHT, TEST METHODS, VISION, VISUAL ACUITY.
Distribution Statement : APPROVED FOR PUBLIC RELEASE
and then of course there is this little bewdy.
Accession Number : AD0295085
Title : AN INVESTIGATION OF THE EFFECTS OF PULSED LIGHTING UPON AIRCRAFT DISPLAYS RELATIVE TO THE PRESERVATION OF DARK ADAPTATION FOR NIGHT FLYING
Corporate Author : DOUGLAS AIRCRAFT CO INC LONG BEACH CALIF
Personal Author(s) : UYEDA,L.R. ; LEVEDAHL,B.H.
Report Date : 18 JUL 1962
Pagination or Media Count : 1
Abstract : THE RELATIONSHIP OF PULSED AND CONTINUOUS LIGHTING UPON A COMPENSATORYTASK, AND ITS SUBSEQUENT EFFECT ON SCOTOPIC DETECTION PERFORMANCE WAS EXAMINED UNDER TWO LEVELS OF ILLUMINATION. RESPONSE LATENCY OF DETECTING LANDOLT RINGS AS WELL AS THE NUMBER OF DETECTION ERRORS INCURRED WAS AN INDEX OF THE TIME REQUIRED TO EFFECTIVELY REGAIN DARK ADAPTATION. ON THE BASIS OF THE RESULTS OBTAINED, IT IS CONCLUDED THAT DARK ADAPTATION MAY BE PRESERVED IF THE VISUAL DISPLAY TO WHICH AN INDIVIDUAL IS ATTENDING IS ILLUMINATED WITH PULSED LIGHTING IN THE FREQUENCY RANGE OF 5 TO 15 CPS. IN THIS CONDITION, THE EXPERIMENTAL VEHICULAR TRACKING PERFORMANCE APPEARS UNIMPAIRED
Descriptors : *INSTRUMENT PANELS, ADAPTATION(PHYSIOLOGY), AIRCRAFT, BRIGHTNESS, DISPLAY SYSTEMS, HUMAN FACTORS ENGINEERING, LIGHT PULSES, NIGHT FLIGHT, TEST METHODS, VISION, VISUAL ACUITY.
Distribution Statement : APPROVED FOR PUBLIC RELEASE
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Abstract : THE RELATIONSHIP OF PULSED AND CONTINUOUS LIGHTING UPON A COMPENSATORYTASK, AND ITS SUBSEQUENT EFFECT ON SCOTOPIC DETECTION PERFORMANCE WAS EXAMINED UNDER TWO LEVELS OF ILLUMINATION. RESPONSE LATENCY OF DETECTING LANDOLT RINGS AS WELL AS THE NUMBER OF DETECTION ERRORS INCURRED WAS AN INDEX OF THE TIME REQUIRED TO EFFECTIVELY REGAIN DARK ADAPTATION. ON THE BASIS OF THE RESULTS OBTAINED, IT IS CONCLUDED THAT DARK ADAPTATION MAY BE PRESERVED IF THE VISUAL DISPLAY TO WHICH AN INDIVIDUAL IS ATTENDING IS ILLUMINATED WITH PULSED LIGHTING IN THE FREQUENCY RANGE OF 5 TO 15 CPS. IN THIS CONDITION, THE EXPERIMENTAL VEHICULAR TRACKING PERFORMANCE APPEARS UNIMPAIRED
These blokes must be practising for a career in politics:
These blokes must be practising for a career in politics: