How bright are those lights

[pelmet]

Ok, I am talking about HIAL(High Intensity Approach Lights) settings. Maybe the vis is a bit low and you would like a brighter than normal setting but not too bright as you noticed that the last time you tried strength 5, they were quite bright on short final. So you decide to as for strength 4.

As a percentage compared to 5, what is the brightness of strength 4?

[PostmasterGeneral]

4/5ths, or about 8/10ths if you prefer metric

[photofly]

Ok, I am talking about HIAL(High Intensity Approach Lights) settings. Maybe the vis is a bit low and you would like a brighter than normal setting but not too bright as you noticed that the last time you tried strength 5, they were quite bright on short final. So you decide to as for strength 4.

As a percentage compared to 5, what is the brightness of strength 4?

Is this a trick question?

[J31]

Ok, I am talking about HIAL(High Intensity Approach Lights) settings. Maybe the vis is a bit low and you would like a brighter than normal setting but not too bright as you noticed that the last time you tried strength 5, they were quite bright on short final. So you decide to as for strength 4.

As a percentage compared to 5, what is the brightness of strength 4?

LED or incandescent?

[J31]

We landed in Calgary a few years ago with the LED lights on 17L stuck on high. The tower could not turn them down and they were almost blinding during the flare. The weather was about 400 feet and 2 miles of mist.

[MCB]

4/5ths, or about 8/10ths if you prefer metric

This is actually completely incorrect, nor is it a trick question as someone else questioned. The following is an excerpt from the AC Halifax accident report.

High-intensity lighting systems have 5 intensity settings (1 through 5, with 5 being the brightest) and ODALS have 3 intensity settings (1 through 3, with 3 being the brightest).

According to NAV CANADA's Air Traffic Control Manual of Operations (ATC MANOPS),Footnote 29 when visibility is less than ½ sm at night, the high-intensity runway edge and centre-line lights should be at setting 4 and the ODALS should be at setting 3. When visibility is less than 1 sm at night, the runway edge and centre-line lighting should be at setting 3, and the ODALS at setting 3. The tower controller can select the brightness in accordance with ATC MANOPS or with pilot request.

According to Transport Canada's (TC's) Aerodrome Standards and Recommended Practices,Footnote 30 setting 5 of the high-intensity lighting system provides 100% of the required output and setting 4 provides 25% of the required output; setting 5 is thus 4 times brighter than setting 4.

The required output of setting 3 of the ODALS is more than 3 times greater than setting 2.

[photofly]

Measured in lumens per square metre? Or lux per square metre? Or RMS voltage apples to the lamp? Or current in amperes? Is the weighting function adjusted for the change in wavelength profile as the filaments change temperature? How accurately is it calibrated? These details are very very important to know exactly how to interpret this vital quantitative result.

Or is this a trick question?

[pelmet]

4/5ths, or about 8/10ths if you prefer metric

This is actually completely incorrect, nor is it a trick question as someone else questioned. The following is an excerpt from the AC Halifax accident report.

According to Transport Canada's (TC's) Aerodrome Standards and Recommended Practices,Footnote 30 setting 5 of the high-intensity lighting system provides 100% of the required output and setting 4 provides 25% of the required output; setting 5 is thus 4 times brighter than setting 4.

Correct. It is not a trick question and yes, I am now going through the AC Airbus Halifax accident report in great detail along with reading various threads about it.

I was surprised when I read about light strength 4 being only 25% of strength 5. I would have assumed perhaps 75%. That is why I decided to post this info.

Strength 4 isn't almost as bright as strength 5, in fact it is nowhere close(only 25% or 1/4 as bright). One of those little gotcha's that you come across once in a while.

That is why I thought I might pass it on. Perhaps someone can let me know if this info is located elsewhere for pilots knowledge.

No idea about the technical details and from a pilots point of view, I am not interested in over-analysis. That's for the smart guys who design these systems. For me, it is just good to be aware about the overall effect of a system expectation when it is working as designed.

[DanWEC]

African or European?

[goingnowherefast]

African or European?

Haha, I was waiting for that comment.

Short answer to the OP
5 is "too f--kn bright"
4 is usually good for day time in crap weather
2 or 3 at night.

Just ask for brighter or dimmer if you don't like what you see. Maybe if it's a bright foggy morning at the approach ban limit, ask for strength 5, bit otherwise it's blinding.

[photofly]

I was being silly; but the eye has a great range of accommodation to different brightnesses: from a moonlit night to bright sunlight is a vast range of illumination when measured. So it makes a lot of sense to that a 1-5 scale of brightness would be non-linear. What you might want on a clear moonless night be a millionth of what you need on a bright but foggy day.

[co-joe]

This is actually completely incorrect, nor is it a trick question as someone else questioned. The following is an excerpt from the AC Halifax accident report.

According to Transport Canada's (TC's) Aerodrome Standards and Recommended Practices,Footnote 30 setting 5 of the high-intensity lighting system provides 100% of the required output and setting 4 provides 25% of the required output; setting 5 is thus 4 times brighter than setting 4.

Correct. It is not a trick question and yes, I am now going through the AC Airbus Halifax accident report in great detail along with reading various threads about it.

I was surprised when I read about light strength 4 being only 25% of strength 5. I would have assumed perhaps 75%. That is why I decided to post this info.


[/quote]

It likely has to do with the type of lights (some form of incandescent, would be my guess) and how they are dimmed. Power varies with the square of voltage, so indeed 25% less voltage is 4 times less power. An incandescent dimmer works by putting a resistor in series with the light, and resistance is basically a constant.

If they were to use LED lights, they are dimmed electronically by changing the conduction angle of the ac wave form with SCRs, so the same formula power = voltage squared divided by resistance, does not factor in as the voltage is not changed, just the time that the lamp receives that voltage is.

[co-joe]

According to Transport Canada's (TC's) Aerodrome Standards and Recommended Practices,Footnote 30 setting 5 of the high-intensity lighting system provides 100% of the required output and setting 4 provides 25% of the required output; setting 5 is thus 4 times brighter than setting 4.


Correct. It is not a trick question and yes, I am now going through the AC Airbus Halifax accident report in great detail along with reading various threads about it.

I was surprised when I read about light strength 4 being only 25% of strength 5. I would have assumed perhaps 75%. That is why I decided to post this info.

It likely has to do with the type of lights (some form of incandescent, would be my guess) and how they are dimmed. Power varies with the square of voltage, so indeed 25% less voltage is 4 times less power. An incandescent dimmer works by putting a resistor in series with the light, and resistance is basically a constant.

If they were to use LED lights, they are dimmed electronically by changing the conduction angle of the ac wave form with SCRs, so the same formula power = voltage squared divided by resistance, does not factor in as the voltage is not changed, just the time that the lamp receives that voltage is.

[photofly]

Incandescent lights are historically dimmed with Triacs, by changing the phase angle of the ac cycle at which conduction starts. (LED dimming is typically done by changing the phase angle at which conduction ends.) Resistance dimming went out in the 1950s.

But you are right that the dimming of incandescent lamps is very non linear (in respect to phase angle) and somewhat (but only somewhat) proportional to RMS voltage. The latter relationship is actually implicit in the definition of RMS (“root mean squared”) since this is the most useful way to define the (single) voltage value of a non sinusoidal waveform, being the voltage of a sinusoid that would give the same power through a pure resistive load.

Dimming circuits are designed with a dimming law built in to try to allow the user better to regulate the perceived brightness rather than find that all the control is “bunched up at one end”.

Even when you have good control of the power, you still must consider perceived brightness curves, and the change in colour of filament lamps, when designing a system.

I’m fairly sure that systems installed at airports are carefully engineered according to some standard or other and somewhat more sophisticated in control than something you’d find attached to the wall of your house.

On the other hand, maybe the airport builder did just nip down to the electrical department at Home Depot. The spares would certainly be cheap.