ac500u,
The ICAO documents are not like Canadian AIP. I checked once more.
Just a copy paste for you from Annex 14 Aerodromes
10.2 Displaced threshold
10.2.1 If an object extends above the approach surface
and the object cannot be removed, consideration should be
given to displacing the threshold permanently.
10.2.2 To meet the obstacle limitation objectives of
Chapter 4, the threshold should ideally be displaced down the
runway for the distance necessary to provide that the approach
surface is cleared of obstacles.
10.2.3 However, displacement of the threshold from the
runway extremity will inevitably cause reduction of the
landing distance available, and this may be of greater operational
significance than penetration of the approach surface
by marked and lighted obstacles. A decision to displace the
threshold, and the extent of such displacement, should
therefore have regard to an optimum balance between the
considerations of clear approach surfaces and adequate landing
distance. In deciding this question, account will need to be
taken of the types of aeroplanes which the runway is intended
to serve, the limiting visibility and cloud base conditions under
which the runway will be used, the position of the obstacles in
relation to the threshold and extended centre line and, in the
case of a precision approach runway, the significance of the
obstacles to the determination of the obstacle clearance limit.
10.2.4 Notwithstanding the consideration of landing
distance available, the selected position for the threshold
should not be such that the obstacle-free surface to the threshold
is steeper than 3.3 per cent where the code number is 4 or
steeper than 5 per cent where the code number is 3.
10.2.5 In the event of a threshold being located according
to the criteria for obstacle-free surfaces in the preceding paragraph,
the obstacle marking requirements of Chapter 6 should continue to be met in relation to the displaced threshold.
But may be this might be of help for you (also from An14) :
3.1.5 Recommendation.- When it is necessary to
displace a threshold, either permanently or temporarily, from
its normal location, account should be taken of the various
factors which may have a bearing on the location of the
threshold. Where this displacement is due to an unserviceable
runway condition, a cleared and graded area of at least 60 m
in length should be available between the unserviceable area
and the displaced threshold. Additional distance should also
be provided to meet the requirements of the runway end safety
area as appropriate.
Best Regards,
Guclu