When flying at night and nearing the destination seeing the airport all lit up is a wonderful and relaxing sight, but what happens if the air traffic controller has gone home or there was never one there, to begin with? Are the lights on all the time? Are they on some kind of dusk/dawn sensor?
ARCAL is Aircraft Radio Control of Aerodrome Lighting and it allows the pilot to turn on the airport lighting system for 15 minutes by clicking their microphone transmit button 5 or 7 times within 5 seconds on the designated frequency. It is only available at airports listed in the Chart Supplement.
To this day I can still remember my first cross-country night flight when I was back in flight school and it was to Salem airport in Oregon. There was just a large black void by the city lights and when my instructor turned on the airport lights it was an incredible sight! From that point on I always waited until I had a good view of the airport before turning on the lights!
Let’s find out how it’s done!
What is Pilot-Controlled Airport Lighting?
There are many terms used to describe remote-controlled airport lighting.
ARCAL – Aircraft Radio Control of Aerodrome Lighting
PAL – Pilot Activated Lighting
PCL – Pilot Controlled Lighting
Whichever term pilots use it is all the same type of system. There is an electronic device at the airport that is constantly waiting for a signal from a pilot to initiate turning on the lights.
There are two main types of PCL systems in use in North America:
- Type K System – This requires 7 clicks of the pilot’s radio ‘Push-To-Talk’ button to turn on the lights to the maximum intensity
- Type J System – This requires 5 clicks of the radio PTT button to turn on to the maximum intensity
To activate the PCL lighting system, the pilot clicks their radio transmit button up to seven times in a 5 second period. Seven clicks will put the lights on to maximum intensity. Once the lights are on the pilot can then click a further 5 clicks to reduce the lights to medium intensity, and 3 clicks for low intensity.
The system works by monitoring a specific radio frequency ‘Carrier Wave’. Each airport will have a designated frequency for the pilot-controlled lighting or it will be monitoring the regular airport radio frequency.
When the pilot radio is tuned to the correct PCL frequency and the pilot presses the radio’s PTT button, the aircraft radio will send out a carrier wave signal for the entire time the button is held. Normally when the pilot is talking to air traffic control or another aircraft the carrier wave is also transporting the voice communication with it.
Think of the carrier wave of a pilot’s radio transmission like a boat and the people on the boat is the spoken message from the pilot. Because the PCL system only needs the carrier wave clicks, the pilot does not need to speak, just click the radio transmit button.
The PCL system just listens for the carrier wave signal. When it receives a series of 5 or 7 pulses (depending on if it’s a Type J or K) of the carrier wave it operates the airport lights and will keep them on for 15 minutes before automatically turning them off.
This airport lighting can consist of all or some:
- Runway End Identifier Lights
- Runway Edge Lights
- High-Intensity Runway Lights
- Taxiway Lights
- Approach Indicator Lights
In other words, the whole field will light up, or it could be just a simple landing strip – It all depends on the size of the airport the pilot is heading into.
One of the dangers of the PCL system is the 15 minute on-time. If a pilot turns on the airport lighting when in or above the clouds and then has to complete a time-consuming instrument approach, the lights can turn off again just as the pilot needs them!
There is nothing worse than on short final to an airport with very little terrestrial or city light around and at 200ft the lights go out! I have had this demonstrated to me and it is a very uncomfortable experience!
To prevent the lights from going out at just the wrong time the PCL system will flash all the airport lights 2 minutes before shutdown, but the pilot may still be in the cloud when this happens and they do not see the warning.
Just to be sure, most pilots are always trained to give the radio mic button 5/7 quick clicks just before starting the final approach as this resets the 15 minute timer, and the lights will be on and shining bright just when you need them!
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When Is Pilot-Controlled Lighting Used?
PCL lighting systems are used extensively at airports where the tower or air traffic controller does not work 24 hour shifts and at smaller airports that have no controller at all.
The main benefit of the PCL system is energy savings. Even with the advances in LED airport lighting technology, it is a waste of money to keep the airport fully lit all night, every night. This system also comes in handy when a pilot is flying an IFR approach in low visibility conditions like fog and the airport lighting can be turned to maximum intensity even during the day.
Another reason is to protect the neighbors from the light pollution large airports can create. An airport with multiple runways, taxiways, and parking aprons has a lot of lights and they do throw off a lot of light pollution.
PCL systems are not just limited to airports. Many hospital rooftop and ground-based helipads may use the system as well as public heliports.
When I flew the air ambulance, our local hospital had the helipad perimeter lights, windsock light, and HVAC intake fans connected to the PCL system.
Dialing the frequency 123.2MHz into the radio and keying the mic 5 times would bring on the lights and shut down the HVAC intake fans for 15 minutes.
Shutting down the intake fans was a great add-on, as the predominant wind at the hospital always blew the helicopter exhaust gas into the hospital and patients would complain of the smell. We always helped out by turning the system off after engine shutdown to keep the HVAC system off for a minimum amount of time. To turn the PCL system off we just keyed the mic 5 times again.
How Do Pilots Find Out About Pilot Controlled Lighting?
Pilots can easily find out about the PCL and type of airport lights by consulting a publication called the FAA Chart Supplement. This used to be known as the AFD (Airport Facility Directory). This publication lists all the details a pilot would wish to know about the airport they intend to fly into or out of.
This is the airport information for Salem Airport in Oregon – My first PCL experience! There is so much information on here but the two parts a pilot is interested in for the lighting are first in yellow, then red.
The yellow box tells the pilot what type of runway lighting pattern is available for each runway then right at the end it says CTAF. This is telling the pilot the PCL system can be activated by keying the CTAF (Common Traffic Advisory) frequency.
To find the CTAF frequency, the pilot then looks in the ‘Communications’ section for CTAF 119.1, this tells the pilot that tuning the radio to 119.1 will have them on the right frequency for the lights. This is also handy, as it is the same frequency they will be talking on when making their calls as they approach and operate around the airport.
If you want to experience a really cool experience I suggest you go for a flight at night with a flying instructor to see how beautiful an airport looks when it appears out of the ink.
By simply selecting the right frequency and keying the microphone a pilot can activate this wonderful system to help them safely approach an airport at night or when the visibility is really low.
One of aviation’s simple, yet well-used technologies!
If you would like to know how pilots can even find their way to an airport in the first place, I recommend you read my article:
Source – Kuhnmi