Why do planes take off down the centre line?

Why do planes take off down the centre line?

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Discussion

bitchstewie

Original Poster:

58,507 posts

225 months

Saturday 20th January 2024
quotequote all
I feel I'm setting myself up to look stupid here but having watched a lot of cockpit videos on YouTube something that's always puzzled me is why takeoff seems to be exactly down the centre line so it looks from the cockpit vids like the airplane is getting quite a shaking from the front gear going over all the centre lights.

Seems a bit like deliberately driving down a row of cats eyes at high speed and the accompanying bumps unless the videos are exaggerating the effect?

normalbloke

8,068 posts

234 months

Saturday 20th January 2024
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The pilots like to monitor the rate the cats eyes pass under the front wheel, as an additional positive indicator of rate of acceleration….

Jimbo.

4,081 posts

204 months

Saturday 20th January 2024
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A good visual indicator of how far left or right the aircraft may be drifting?

Boozy

2,425 posts

234 months

Saturday 20th January 2024
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Because it’s the middle and planes are quite big?

Bill

55,691 posts

270 months

Saturday 20th January 2024
quotequote all
It's just a habit from the old paper licence where it says tear along the dotted line.






Sorry...getmecoat

greygoose

8,975 posts

210 months

Saturday 20th January 2024
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Bill said:
It's just a habit from the old paper licence where it says tear along the dotted line.


Sorry...getmecoat
hehe



mike_e

593 posts

278 months

Saturday 20th January 2024
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Because the wheels under the wings are closer to the edge of the runway than the nosewheel, and crosswinds can make the plane veer to one side.


Prawo Jazdy

5,003 posts

229 months

Saturday 20th January 2024
quotequote all
If your directional control is impacted by (as said above) wind, “contamination” on the runway, or an engine failure on a twin (or other thrust asymmetry), you’ll benefit from having as much room as possible to sort it out before running off the edge.

Some airports like Mykonos have narrower runways than the fairly standard 45 metres, so flying there requires extra training to be completed.

Motorman74

475 posts

36 months

Saturday 20th January 2024
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Surely because it's good practice to be in the centre of the runway, so if something unexpected happens, you have the maximum available space on both sides to keep it on the tarmac

surveyor

18,352 posts

199 months

Saturday 20th January 2024
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They should not be exactly in the centre...

https://aviation.stackexchange.com/questions/95794...

Leon R

3,434 posts

111 months

Saturday 20th January 2024
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Surely if you were right on the centre line the nose wheels would be either side of the lights.

In most aircraft anyway.

Countdown

44,361 posts

211 months

Saturday 20th January 2024
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For those suggesting the planes are quite big , surely 6 inches either side of the centreline still leaves a fair amount of safety gap to either side ?

Terminator X

17,659 posts

219 months

Saturday 20th January 2024
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2 wheels isn't it so if exactly mid point the wheels would be either side?



TX.

Mr_J

466 posts

62 months

Saturday 20th January 2024
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surveyor said:
They should not be exactly in the centre...

https://aviation.stackexchange.com/questions/95794...
We put them in the centre.

IanH755

2,290 posts

135 months

Saturday 20th January 2024
quotequote all
The centreline lights are actually used as a form of braille for the few blind pilots on a diversity hire, so when the "bumps" get closer together the pilot knows to lift the nose and take-off. Landing was a whole lot trickier until they allowed guide dogs to be used, now the pilot can just feel when the lead goes slack to know they're close to the ground.

True story.

smile

texaxile

3,471 posts

165 months

Sunday 21st January 2024
quotequote all
IanH755 said:
The centreline lights are actually used as a form of braille for the few blind pilots on a diversity hire, so when the "bumps" get closer together the pilot knows to lift the nose and take-off. Landing was a whole lot trickier until they allowed guide dogs to be used, now the pilot can just feel when the lead goes slack to know they're close to the ground.

True story.

smile
Have a biglaughbiglaughbiglaughbiglaugh

Reminds me of that old joke about the blind parachutist...

Cl4rkyPH

300 posts

62 months

Sunday 21st January 2024
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Going over the lights doesn’t cause them or the plane any harm, nor any discomfort to passengers (other than an already abrupt/loud part of the journey). So it makes perfect sense to train pilots to position the aircraft right down the middle.

If pilots were taught to align the aircraft “just to the side of the centreline” it would then create a grey area e.g “how far can I stray from the middle?” As other posters have said above, straying from the middle is not ideal for many reasons.

As such, the centreline serves the best point for pilots to align with.

bitchstewie

Original Poster:

58,507 posts

225 months

Sunday 21st January 2024
quotequote all
Thanks all.

Honestly when you watch some of the videos the sound of the bumps seems very audible to the point where if it was a car you'd try not to go over them.

If it's as simple as other than sounding a bit noisy they don't do any damage that's fair enough and perhaps I was overthinking it smile

normalbloke

8,068 posts

234 months

Sunday 21st January 2024
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You want to see the efforts a B52 goes to, trying to avoid them…

Eric Mc

123,848 posts

280 months

Sunday 21st January 2024
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The Trident airliner's nose wheel was offset so keeping to the middle of the runway ensured that the nose wheel didn't hit the lights. That wasn't the reason the nose wheel was offset but it was a consequence of the design.