Tue Mar 16, 2021 10:25 am
#1833597
Could you help explaining this, please?
Shouldn't it be opposite to side approach?
Thanks
Moderator: AndyR
A4 Pacific wrote:I have to ask because I genuinely don’t know. Does that mean that on shorter runways the localiser beam for full deflection is wider at distance from the field? On longer runways the beam will be narrower at the same distance? For example LCY is about 1200m, LHR about 4000m.
Because that’s not as I understood it? Is the position of the loc antenna adjusted to provide the same pattern on all runways? It’s something I’ve never really thought of.
The difference could be quite considerable couldn’t it?
FlightDek wrote:So full scale deflection of the CDI is not necessarily 2.5º off-course?
AndyR wrote:
The longer runways will in fact have a more 'sensitive' localiser on intercept for the same distance from the threshold as the beam width is narrower. There are limits, but when the localiser is checked, this is one of the tolerances it must meet, the width being co-dependent on the runway length.
David Wood wrote:I suspect (but this is only a guess) that it's to do with the 1/2 scale deflection limit insofar as if at minimums (usually 200') you were at the limit of a legal approach (ie, at a half-scale deflection of the CDI) and looked up to visually acquire the runway you then would be in a position in which, albeit off the center-line, you would not need to make significant heading changes in order to make a safe landing. That's my guess.