Hash

[rhtrudder]

Quote

 

Just fitted a led to my landing leg, super bright, been a couple of midair’s so I figured it might help on final, trouble is it drowns out the radio , any way I can make it work, wired it to the nav lights

[RFguy]

needs suppression components fitted at the LEDs

1uF in parallel with 0.1uF in parallel with 0.010uF ceramic disc capacitors

THEN

3 turns of the wiring through a type 43 ferrite choke toroid or 10  x 1/2" beads

 

[rhtrudder]

Ok thanks I’ll get onto it

[facthunter]

Don't get onto HASH. Nev

[RFguy]

Try just the capacitors first use lead length on the capacitors of about 0.1" to 0.4" : for the 1uF and 0.1uF, and use 0.1" lead length for the 0.01uF . 

 

https://www.minikits.com.au/components/passive/capacitors/ceramic-capacitors/MLCC-Series

1uF X7R 50V 5mm MON105-X7R-50B

100nF X7R 50v 5mm MON104-X7R-50B

10nF XR7 50v 5mm MON103-X7R-50B

 

ferrite toroid : x2

https://www.minikits.com.au/FT82-43?search=ferrite 43 FT82

 

 

 

[skippydiesel]

2 hours ago, rhtrudder said:

Just fitted a led to my landing leg, super bright, been a couple of midair’s so I figured it might help on final, trouble is it drowns out the radio , any way I can make it work, wired it to the nav lights

Just parroting stuff I have read & heard -

• Aircraft lights work well : in  low light conditions and when viewed from the ground.
• Aircraft lights have little benefit:  when viewed in bright sunlight and in aircraft to aircraft situations.

 

The consistent opinion/advice is that  the best most cost effective defence (in small aircraft) against a mid air collision is the transceiver ie communication. Pilots, interested in safety, must give regular updates on their position and intentions, using the correct frequency(s) and verbal format. Its always best to make a few too many calls than to few.

 

The human eye is as well adapted for flight as the rest of the body and can not be relied on to see  other aircraft without having a hint (communication) where to look.

[rhtrudder]

Agreed, but I noticed when waiting to enter the active runway and checking for incoming aircraft the ones with their landing lights on seem to stand out more

[RFguy]

yeah, they do, but ..then what are you looking out for : an aircraft with   no landing light AND no radio comms ?  the two probably go together so I dont think you've improved safety by much...  But I agree, a really bright landing light will be more visible than nothing-

Edited November 21, 2022 by RFguy

[RFguy]

Let us run some numbers

Sky background on a clear day with sun at Zenith is about mag -23, which equates to about 3400 lux

 

That's the minimum I reckon.

Let's assume you have a 10W LED about 90lm/watt, (=900lm)  over a 10 deg cone- At 1m away, that's what...78 square degrees, out of 41253 =which at 900 lm source will be... 472,000lux (lm/sqM) . now 1km away, will be 1000x1000 less or 0.472 lux. gee we're a long way short at 1km  at noon.....  

 

Now the 737 landing light I read GE Lighting Q4559X https://www.gecurrent.com/catalog/par64-halogen-lamp-42552

They are specified at around 8,000,000 lux !. 1km away they'll be 8 lux. hmm quite a bit !    15min after sunset,  clear sky is ABOUT  3 lux - so yes you can see a 737 at 1km away .

 

Venus is about mag-4, that's a good one to  to compare to , that is visible at dusk and dawn.... that is only 86microLux. so the background dusk sky is at least darker than that. 

 

I'll think about those numbers, wonder i I have got my numbers wrong.

 

 

[Carbon Canary]

I suspect strobes will get more attention than a steady light at the same strength.

[RFguy]

And for very low point light differences , for a continuous light source, there is something like 2.5 seconds perception delay, so you need to stare at that bit of sky, a glance will not do  it.   Pulse light sources are treated differently. more complex relationships with pulse length, intensity etc

 

Probably well described in some FAA publication somewhere

 

 

 

[skippydiesel]

Without  having the all important location "clue"  aircraft lights for day time (good visibility) conditions are, at best, a nice bit of "bling" that adds a professional look to the aircraft/pilot.

 

When viewing an aircraft in flight, from the ground: we have immediately restricted (located) the aircraft to somewhere above the horizon, we may then have an audio clue (noise) further narrowing its position. If we are a pilot waiting for take off,  we should have heard positions calls from the airborne aircraft and we will look for it (or any other aircraft) in the circuit/on final (location) - lights on the airborne aircraft will help, a little but we most likely already have it  sighted.

 

When trying to find an aircraft in the 3 dimensional world of flight, our lack of adaption for this environment is almost total. Lights will make very little difference. The keys to seeing/being seen by, another aircraft are; having a practised visual sweep of the sky (still only a low chance of picking up an aircraft but better than nothing) and communication (by the far the best). Communication narrows the position, so that our poor vision has a chance to locate the other aircraft (& visa versa) It may no longer be required to give as many calls, as we were once were (possibly too many) but the current ambiguous communication rules just make our struggle to see & be seen so very much worse and wee lights, twinkly or otherwise, have very little benefit.

 

[onetrack]

Quote

15min after sunset, clear sky is ABOUT 3 lux - so yes, you can see a 737 at 1km away

And at say, 200mph on final, and 1 km away - that gives you around 11 secs to get out of its way!

[danny_galaga]

Reading all I've read here about lights makes me wish I didn't have any. All that extra wiring and weight and an extra switch virtually for nothing. I actually wouldn't have fitted them except the wing tips have a clear section for the lights so I thought I might as well fill it up with something 😄

Edited November 22, 2022 by danny_galaga

[rhtrudder]

I just took it off , looks like it wasn’t worth the trouble, thanks for all the input 

[facthunter]

"Proper" strobes are pretty intense. In cloud they upset passengers and you never use them near other planes when on the ground. Nev

[Blueadventures]

Good to have strobes and landing light.  Also good for early winter taxiing as can see the ground ahead a little.  Sort the hash.

 

 

[RFguy]

Good strobes are 50 Joule flashtube pulses and about 1mS pulse. smaller ones are 25Joules

 

a xenon flashtube converts about 30% of that energy into the visible light range. pretty good. light output of 50*0.3 = 15J . 0.001 = 15,000W .

which is... what.. x683 = 10,245,000 lumens., so if an isotropic radiator (uniform illumination of a sphere)  1km away would be 10 lux. wow. quite a bit. now, most of these have fresnel lens reducing the beam angle by 3x, but efficiency of the lens maybe 70%, so on axis maybe 10lux*.7 * 3 =21lux.

....dont trust all my numbers here, they're my first dig at this over a cereal   bowl ..... 

Now, as 15min after sunset could be somewhere around 3 lux sky brightness, I tend to generally believe those 21 lux numbers I came up with , since those strobes are fairly good after the sun dips.

 

not sure I have my conversion of venus apparent mag of -4.5 to lux and background sky correct (earlier post either) .  Venus is visible in the day, in very clear atmosphere at closest approach, at ap-mag of -4.5 ish. I am going to have to do some research. Yes magnitude per arc-second of sky is what I need to work on..... more later

[RFguy]

working more on point sots of light and how the eye perceives such things....

the calcs  above I did not do my spherical calcs correctly. (doing over breakfast cereal) 

actual output of the strobe at 1km was 0.8lux, and after the tail top strobe fresnel lens, improved to 1.7 lux

 

clear sky brightness is 1.5 to 4  magnitudes per square arc second. 

venus close is -4.5 mag and half face illuminated of the 29 arc seconds of diameter is  330 sq. arc seconds which is surface brightness of -4.5mag + 2.5log(330)=1.8.   ah ha. visible ! OK my math corroborates with :

https://iopscience.iop.org/article/10.1086/430212/pdf and https://vanderbei.princeton.edu/SUTU/2010Oct20.shtml

 

at 2km distant, the tumbler sized strobe is a truly a point source as far as the eye is concerned- only 10 arc seconds in diameter lets call it 157sq arc seconds. 

 

maybe go back to working in W/m^2.

apparent mag zero is  2.5e-08 W/m^2

 

 

 

 

 

 

Edited November 22, 2022 by RFguy

[Carbon Canary]

So after all that, I suppose a ‘good’ strobe is more discernible then ?

[RFguy]

Yes very much so.

15W of light , increased in intensity on axis (fresnel lens in a tail strobe) x2.1 = ~30W of light from a 50 Joule strobe.. approx

30W at 2km = 30 x (1/ 4pi (2000x2000))  = 6e-07 W/m^2

clear sky app. magnitude  of say 1.6 (bright). ( about 0.229 of mag 0)  in W/m^2 is 6e-09 W/m^2.

so the strobe at 6e-07 W/m^2 is considerably brighter than the clear crisp background daytime sky at 2km.

 

there is an absolute ratio there of around 100x there.   recall the 50J flashtube is about 10,000,000 lumens in a sphere  , about 21 million on narrow lens axis....

 

So an LED to do the a tenth of the same job (but likely still visible) needs at least a 2 million lumens on the subject. 

If the LED is 20,000 lumens (I made a bike flasher that bright). over a 30 degree cone, that's a gain of 58 over a spherical illumination, that's an on axis intensity of 20,000 x 58 = 1.1 million lm-  ...... 

A 3000 lm LED bike light over 30 deg cone will only get you to half a million lumens. 

 

 

 

 

[rhtrudder]

I’m starting to wish I hadn’t asked the question 

[Carbon Canary]

By asking questions, we all learn something, or at least get entertained along the way.

 

Now we know why emergency vehicles and heavy aircraft have flashing lights - someone did the math.

[skippydiesel]

No offence RFGuy but all the maths does not address the ability (lack of) of the human eye to pick up other aircraft (in flight) in good VFR conditions, with or without lights (of any intensity and/or twinkle).

 

I have often been impressed by the effectiveness of bicycle flashing lights, even in bright sunlight, however they are constrained/restricted to the road in front  (location, location, etc) not somewhere in an imaginary sphere surrounding my aircraft.

[facthunter]

You have to be taught to do a proper scan.. Nev