Aircraft Operations. Volume II - Construction of Visual and Instrument ...

II-1-1-App B-2 Procedures — Aircraft Operations — Volume II
Use the formula:
23/11/06
2.3 Determination of the height of equivalent approach obstacle
ha =[hma cot Z + (x – Xzo)]/(cot Z + cot θ)
where: ha = height of equivalent approach obstacle
hma = height of missed approach obstacle
θ = glide path angle
Z = angle of missed approach surface
Xzo = new co-ordinate of Z surface origin
x = range of obstacle relative to threshold (negative after threshold).
Note.— In using criteria specified in the text and drawings of paragraphs 1.5 and Chapter 3, 3.5, “Missed
approach segment” use the newly calculated co-ordinate of “Z” surface origin (Xzo) instead of the value of –900 m.
2.4 Re-survey of obstacles
As the configuration of the OAS is changed, a re-survey of obstacles may be required.
2.5 Promulgation
A special note shall be included on the instrument approach chart stating that appropriate aircraft and crew
qualifications are required to use such a procedure (see Annex 4, 11.10.8.6).
3. HEIGHT LOSS MARGIN AND OTHER CONSIDERATIONS
3.1 Height loss margins for glide paths greater than 3.5° or less than 3.5°
The height loss margin can be obtained by extrapolation from the formulas in 1.4.8.8.3.1 and Chapter 3, 3.4.8.8.3.1,
both entitled “Height loss (HL)/altimeter margins”. However, this extrapolation may not be valid for glide paths greater
than 3.5° or less than 3.5° when the nominal rate of descent (Vat for the aircraft type × the sine of the glide path angle)
exceeds 5 m/sec (1 000 ft/min), unless certification on flight trials has verified the effects of:
a) minimum drag configuration;
b) effect of wind shear;
c) control laws;
d) handling characteristics;
e) minimum power for anti-icing;