Screen height?

[doubtfire]

Can someone help me out with a perf question on screen height.
As I understand, the screen height is predicated on toda which can include a clearway. If that is the case and the clearway is the max allowed then in the case of a performance limiting field (no flex, max flap, toga) then the main wheels over the end of the physical runway may be well below 35ft (or 15ft) However. in other definitions it states the screen height is above the end of "takeoff surface". If the screen height was based on tora then I understand completely but if it`s based on toda (with a clearway) then you could possibly get airborne with the main gear literally skimming the runway end identifier lights. Help please.

[STFMD80]

That's why the clearway has to have a maximum slope of 1.25%, be at least 500ft wide and without protruding objects. Runway lights are the only exception to this provided they are at the side of the runway and with a maximum height of 26 inches.

[FLX/MCT]

According to my understanding the "take-off run" caters for the MLG "skimming" over the lights.

The take-off run on a dry runway is
the greater of –
(i) The horizontal distance along
the take-off path from the start of the takeoff
to a point equidistant between the point
at which VLOF is reached and the point at
which the aeroplane is 11 m (35 ft) above
the take-off surface, as determined under CS
25.111 for a dry runway; or
(ii) 115% of the horizontal distance
along the take-off path, with all engines
operating, from the start of the take-off to a
point equidistant between the point at which
VLOF is reached and the point at which the
aeroplane is 11 m (35 ft) above the take-off
surface, determined by a procedure
consistent with CS25.111.

[FlightDetent]

What FLX/MCT says. The mid-point between lift-off point and achieveing the screen height needs to be over the runway end the latest. On a dry runway that is.

[john_tullamarine]

As a side note, older BCAR Types would have been certificated to (as best as I can recall this time of the evening ..) 1:2 rather than the more usually seen 1:1 ratio for the flare to screen.