Walking this evening I looked up and saw a plane which I assumed was on approach to Liverpool John Lennon. When I looked carefully I could see that as well as the anti-collision strobes it was flashing two lights in sequence. I assumed they were the landing lights as they were very bright and positioned towards the wing tips. However, they were clearly flashing one at a time, left then right.
I've never seen this before, is it normal and does it signify anything?
The flashing lights help to make the airplane more noticeable. They have also been suggested to reduce the risk of bird strikes. This is offered as an option or add-on for many types of aircraft.
In addition to helping the pilots to see ahead of them when on the ground in dark conditions, landing lights help to make planes more visible to others. The FAA requires landing lights to be on for commercial flights under 10,000 feet, and encourages pilots to turn them on at least when near an airport or in low visibility. Flashing the lights makes them less likely to be confused for something like a star at night.
It is certainly a standard feature on the Dassault Falcon, we have a "pulse"position where it flashes as you describe which we switch below 10 000 ft, and then the "ON" position which we use on we are clear to land.The latest being purely a company SOP.
I thinking what you saw were the landing lights. Airplanes do tend to have taxi lights and landing lights in order to make it easier for pilots during night time.
