PPRuNe Forums - View Single Post - Screen height 35ft, where is it?
View Single Post
Old 1st Apr 2017, 04:02
  #3 (permalink)  
john_tullamarine
Moderator
 
Join Date: Apr 2001
Location: various places .....
Posts: 7,197
Received 111 Likes on 71 Posts
is it at the end of the runway or clearway (TODR)?

Subtle points of note -

(a) end of runway is TORA

(b) end of clearway is TODA

(c) TODR, for a specific aircraft, is the figure which comes out of the AFM calculations and must not exceed TODA (as noted)

The 35' screen is at the end of TODA


(d) A very common error; I guess mainly due to the typical BFL drawing one tends to see in the textbooks. Screen is at the end of TODR. If there be excess available in the TODA compared to TODR, that's fine, but it's not relevant to the specific takeoff calculation once the V1/VR ratio is selected.

If the particular situation results in TODR = TODA, then screen will be at the end of the TODA but that is a specific instance rather than the general case. An extreme way to visualise the distinction is for an aircraft with TODR = 2000 ft departing from a 14,000 ft runway .... hitting 35 ft at the end, while probably being great fun, is not relevant to the routine takeoff exercise.
john_tullamarine is offline