On Sat, 04 Oct 2003 01:45:54 GMT, David Megginson
wrote:

I was glancing at the IAP for the CYKF (Kitchener/Waterloo) ILS 25
tonight (like most Canadian plates, it's not available online), and I
noticed that the DH is very high:

ILS 1554 (500) 1 1/2
LOC 1560 (506) 1 1/2
CIRCLING [A,B] 1560 (506) 1 1/2 [C] 1560 (506) 2 [D] 1700 (646) 2

Ouch! Does anyone know why DH for the ILS approach is nearly the same
as circling minima? I landed there once VFR and do no remember any
major obstructions, and there's nothing noted on the plate near the
final segment. The CFS has a couple of notes on this approach in the
PRO section:

1. The approach overflies Guelph airport about 1000 ft above circuit
altitude.

2. Expect delays when CYYZ (Toronto) 05 and 06R are in use.

but neither of these would affect DH.

Nearby, the CYXU (London) ILS 15 and CYHM (Hamilton) ILS 12 approaches
both have the regular 200 ft DH.



It's not always possible to know why without being a TERPS expert (or
whatever the equivalent is in Canada) and having detailed topo maps. For
example, at my local airport, the MDA on one approach is constrained by a
tree that is some 30,000' from the airport. Since that tree has to be
cleared by a certain altitude, and since there is a maximum allowable
descent gradient, that obstacle determines the minimums. (At some time in
the future, with GPS, they may add a step-down fix to get us lower).
There'd be no way to determine that from aviation charts.

Some guesses:

1. If there is a requirement to be 1000' above circuit altitude going over
Guelph, then descent gradient restrictions may preclude a lower DH.

2. Other charts show two towers about 1100' from the centerline inside
Kilo. One is 1400/350 and the other 1324/274 MSL/AGL. Could these be
having an effect?

3. There is a tower (1117'/96') in what should be the missed approach
protected area about 1/2 mile WNW of the runway.

4. Or it could be some other reason altogether.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)