"Dimming" runway lights?

[Chronistin]

I always thought that the brightness of runway lights is standardized, or depending on the bulbs used. Yesterday, a spotter friend told me he heard on his scanner a pilot asking the tower for dimming of the runway lights. I said he must have misunderstood. He insisted. (But he also said there was no noticeable difference in lights after the request.)

So, is this even possible? Can the brightness of the lights be adjusted?

[Jumbo744]

yes absolutely.

In Canada for exemple, if you fly at night at an uncontrolled aerodrome, you will be the one turning the lights on, and setting their brightness!

Depending on the aerodrome, you will click on your push-to-talk button with the radio set on the aerodrome frequency 5 or 7 times in 5 seconds to turn the lights on. They will come up at full intensity, if it is too bright for you, you click again (i think once) and it will decrease the brightness, click again and it will decrease even more...

[Ratatat]

Brilliancy settings of 100% , 80% (PAPI's only?), 30% , 10% , 3% and 1% are available on most of the services which can be selected individually. ie edge, centreline, threshold, high intensity approach lights, papi's, touch down zone and supplementary high intensity approach lights.

There are specific settings for day, twilight and night with visibility and cloud height also having an impact.

This applies to Gatwick and I presume the major airfields of the UK.

[BOAC]

As Ratatat says, the lights SHOULD be adjusted for the conditions, but I have often had to ask for the lights 'down' at many airports when someone got it wrong and the lights were far too bright for the conditions so as to dazzle and take away any ability to see the runway itself.

The other 'old chestnut' is where a sequenced flashing approach light chain leads to the runway - known as the 'rabbit' - and the call was 'shoot the rabbit'.:)

[DIBO]

(But he also said there was no noticeable difference in lights after the request.)

When observing the RWY lights from the side, the dimming is less noticeable (omni-directional low intensity); from within the RWY axis, you'll observe the dimming of the high intensity lightbeam created by the lenses in the light dome.
Example of 'concentric circle' lenses in a light-dome which focus the light in an high intensity light beam: RWY Light Lens (http://www.genesislamp.com/clearoldstyle.html)

[kharmael]

OP:

When training to fly at night or practise for going to more "austere" airfields, the runway lights and PAPIs are dimmed or switched off completely to force the pilot to judge his approach angle and height without external aids. :ok:

[Chronistin]

Wow, learning something new every day! Thankyou for the answers (although I owe the guy a beer now... :ouch: ).

[Scarbagjack]

Well, strike me pink!! Would never have thunk it.
Always something to learn on this site,excellent!!
Good question and answers. Well Done.:D

Cheers, SBJ

[411A]

Brilliancy settings of 100% , 80% (PAPI's only?), 30% , 10% , 3% and 1% are available on most of the services which can be selected individually. ie edge, centreline, threshold, high intensity approach lights, papi's, touch down zone and supplementary high intensity approach lights.


In the USA, these lights are generally adjusted in 'steps', step 1 (the least) to step 5 (full bright).
It would not be unusual, therefore...for a pilot to request 'step 5' for approach in low visibility conditions, and then ask for the lights to be dimmed once the runway was in sight.

[jumpseater]

Brilliancy settings of 100% , 80% (PAPI's only?), 30% , 10% , 3% and 1% are available on most of the services which can be selected individually. ie edge, centreline, threshold, high intensity approach lights, papi's, touch down zone and supplementary high intensity approach lights.

There are specific settings for day, twilight and night with visibility and cloud height also having an impact.

This is correct though the PAPI's I'm familiar with have the same settings as all the others. They can be adjusted by ATC to reflect operational and meteorological changes, so the viz and cloud criteria settings above can be over ridden by ATC on a tactical basis. These can include turning them up to assist a pilot visually finding the airfield/runway, and then reducing them for the rest of the approach.

You could also turn them down too much, that however normally results in 'paperwork' :oh:

[Sir George Cayley]

Those loverly peeps at the CAA have written it all down:ok: So take a Gander at CAP168 Chapter 6 AGL on the publications section of their website and search out the table of brilliancies.

It's all controlled by Voltage RMS apparently wot evor that is:D

Sir George Cayley

[BOAC]

Out of the 50+ RMS abbreviations I'll put my money on Root Mean Square. I'm pretty sure that even the CAA would not use a Retail Management System or a Royal Mail Ship for that- although on second thoughts......................

[reportyourlevel]

We have a touchscreen lighting control panel now, and there are several presets so all we have to do is select day/twilight/night and a combination of visibility/cloud for the lights to be displayed at the correct (CAP168) intensities. There is a manual override if we need to change anything.