LOWVIS and displaced threshold

[iFly738]

Hey guys,

got a question about LOWVIS ops and displaced thresholds.
In our company we can lower the RVR required for take off to 125m on the 737.
One of the requirements is that the centerline lights are spaced 15m apart and the runway edge lights 60m.

Now when you have a displaced threshold. Are the centerline lights before the displacedthreshold also spaced 15m apart? For example LIMC - Milano
I can't find it in LIDO and the airport diagram only shows CL spacing is 15m.
There is no difference in the part before and after the displaced threshold.
But is this true? I remember it was different....

Thanks!

[rudderrudderrat]

Hi iFly738,

The runway centre line lights before the displaced Landing Threshold serve as Approach Lights so will be 30m apart. The CL Lights after the landing threshold will be 15m apart.

One of the requirements is that the centerline lights are spaced 15m apart and the runway edge lights 60m.
Check with your Company Ops manual.
Ours permits us to use the full take of length, despite the lights being 30m apart initially - provided we can see the required visual clues using "Pilot assessment".

[RAT 5]

R.Rat: Pilot assessment requires counting the lights to gauge distance. The question is how do you know the lights before the threshold are different to after? In 125ish RVR it will be difficult to estimate if there is a difference. While you say the light before the threshold are technically approach lights, they are also takeoff lights if full length is approved. In that case why would they not be the same as the rest of the rwy? You'll guess I do not know the answer 100%.

[iFly738]

Thanks for the reply (and so fast!). :ok:
That they serve as approach lights.... totally forgotten about that!

We are required to count the lights before we go in take-off.
But how do I know when the lights are 30m apart?
On the LIDO charts there is only a statement of CL 15m. And the lowvis charts doesn't come with any nr of spacing of the CL.



Strange thing (in my opinion) is that we need an RVR of 125m and only a visual segment of 90m, 6 lights (+ 12 m obscured on the 737) is a total of 102m visual segment. Where is the other 23m?

[STBYRUD]

You are supposed to count six lights to have a 90m visual - but of course only if the actual reported RVR is at or above 125m.

[rudderrudderrat]

@ iFly738 But how do I know when the lights are 30m apart?
The Runway Layout diagrams in Jeppesen show the approach light drawn in black bars over the white background, and white bars over the black runway background. They are all standard 30m apart down to the landing threshold. The Landing data shows the spacing of the runway lights for the Landing Roll.

@ RAT 5 While you say the light before the threshold are technically approach lights, they are also takeoff lights if full length is approved. In that case why would they not be the same as the rest of the rwy?
If all the runway centre line lights for the full length including up to the inset landing threshold were 15m apart, how do you propose to turn off half of them off for Landing Traffic and back on again for departing traffic?

Next time you line up on a runway at night - have a look out of the window.

[9.G]

while opinions diverge about the TDZ RVR report necessity one thing is absolutely crucial about LVO takeoff. Rejected takeoff at low speed is most challenging maneuver requiring utmost availability of visual reference. That being said takeoff from the displaced THR is more viable as it doesn't contradict the performance calculations and provides best visual reference with 15 M CL.:ok:

[iFly738]

@rudderrudderrat
Thanks!

Found it indeed!