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I asked Does runway center lighting increase runway lifetime? and this video was was mentioned.

I don't really understand the significance and I first assumed centreline lighting in night conditions helped crews know half the runway is done and they don't accidentally overshoot the runway.

But I was explained centreline lighting helps in directional and alignment guidance for the aircraft. How is that possible?

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    $\begingroup$ OK, you've now asked two questions "Do runways have centreline lighting for reason X?" Why don't you just ask, "Why do runways have centreline lighting?" $\endgroup$ – David Richerby Nov 27 '16 at 10:38
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    $\begingroup$ I wonder if you wouldn't be interested in reading training documentation, e.g. the Pilot handbook of aeronautical knowledge. Its chapter 14 is about airport operations, and runway lighting starts page 14-18. $\endgroup$ – mins Nov 27 '16 at 12:13
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Runway centreline lights serve two main purposes:

  • Inform the pilot about where the centre of the runway is (they are installed on the runway centreline.
  • Inform the pilot about how far away the end of the runway is (by colour coding the final 900 m metres of runway centre line lights).

Their safety objective is to help prevent misalignments when landing and taking off, as well as to help prevent undershoots and overruns.

They are not always required, and in fact they are considered a complementary system to other visual aids such as runway edge lighting or runway markings, amongst others.

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Yes. From wikipedia

Runway centerline lighting system (RCLS) – lights embedded into the surface of the runway at 50 ft (15 m) intervals along the runway centerline on some precision instrument runways. White except the last 900 m (3,000 ft): alternate white and red for next 600 m (1,969 ft) and red for last 300 m (984 ft).

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    $\begingroup$ This feature is not unique to centerline lights—runway edge lights are designed the same way—and does not answer the question of the purpose for runway centerline lights, which is primarily providing directional and alignment guidance to the flight crew. $\endgroup$ – J Walters Nov 27 '16 at 3:04
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centerline markings (including lights) provide an aiming point for pilots to keep their aircraft properly lined up.
Giving a distance indication is nice, but secondary.

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  • $\begingroup$ now the way the video shows, it seems the runway with side-lights and the centrelight is a huge 'H' with lights on the left and right-side of the runway and the centreline lighting running in the middle of it. How does it help in directional and alignment guidance ? $\endgroup$ – shirish Nov 27 '16 at 6:48
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    $\begingroup$ @shirish ever tried keeping exact center on the road without a centerline to guide you? Most people tend to end up driving way off center, hugging the left or right marker lines. Same applies to runways, the centerline helps the pilot stay on center, and gives him an aiming point to determine where center is even before he gets to the ground. $\endgroup$ – jwenting Nov 27 '16 at 10:31
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    $\begingroup$ Are you possibly confusing the centerline lights which run longitudinally down the runway with either the decision bar or runway end lights that run laterally. The only H-shape I can think of would be if there was a lahso bar running across the runway to indicate the point they need to stop by $\endgroup$ – TomMcW Nov 27 '16 at 22:43
  • $\begingroup$ My previous comment was notended for the OP. Forgot to tag him $\endgroup$ – TomMcW Nov 27 '16 at 23:37
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There are special coded red lights for the last 900m of runways. But not for all. You have to check it before you go.

Runway Lights

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