LOC(BC) MDA: 287 ft AGL

I've just noticed in the latest CAP (Canadian approach plates) that the MDA
for the LOC(BC) 25 approach at Ottawa/CYOW has been lowered from 800 ft (427
AGL) to 660 ft (287 AGL). I can see how it makes operational sense -- it is
the approach runway usually named in the ATIS (despite the fact that two
others have ILS's) -- but an MDA of 287 ft AGL seems low for a non-precision
approach. Are there many similar examples out there?


All the best,


David

Not having access to the chart, I can only presume they got lower minimums with
a stepdown fix. The LOC trapezoids are quite narrow in close, so such a low MDA
is possible at a place where it is flat, close in. The MDA in theory could be
as low as 250 feet if there were no obstacles higher than the TDZ elevation and
the addition of the basic 230 feet of required obstacle clearance to the MSL
value of the TDZ results in a number ending in 20-foot increments so it doesn't
need to be rounded up.

David Megginson wrote:

I've just noticed in the latest CAP (Canadian approach plates) that the MDA
for the LOC(BC) 25 approach at Ottawa/CYOW has been lowered from 800 ft (427
AGL) to 660 ft (287 AGL). I can see how it makes operational sense -- it is
the approach runway usually named in the ATIS (despite the fact that two
others have ILS's) -- but an MDA of 287 ft AGL seems low for a non-precision
approach. Are there many similar examples out there?

All the best,

David

On Sat, 22 Nov 2003 01:56:56 -0800, wrote:

Not having access to the chart, I can only presume they got lower minimums with
a stepdown fix. The LOC trapezoids are quite narrow in close, so such a low MDA
is possible at a place where it is flat, close in. The MDA in theory could be
as low as 250 feet if there were no obstacles higher than the TDZ elevation and
the addition of the basic 230 feet of required obstacle clearance to the MSL
value of the TDZ results in a number ending in 20-foot increments so it doesn't
need to be rounded up.


There's no stepdown fix inside the FAF. The FAF is at an NDB 4.1 miles
from the runway (MAP). The FAF altitude is 1500' (MSL). AGL at the FAF is
not charted (JEPP).

They do have HIRL, ALS and PAPI. Can you get lower minimums with the
addition of lighting?


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

wrote:

Not having access to the chart, I can only presume they got lower minimums with
a stepdown fix.

Yes, it's unfortunate that Canadian approaches cannot be published for free
online like US ones are. The airport recently installed a DME to replace
the old UUP TRACON, but it's not used in the approach except as an
alternative way of identifying the FAF (the OW NDB) -- there are no
step-down fixes past the FAF. Here's a summary of the approach, leaving out
published transitions and the missed approach instructions:

IAF: OW NDB
MSA: 2900 ft (N), 2100 ft (S), based on OW (MSA is operational in Canada)
PT altitude: 2500 ft
FAF: OW NDB
FAF crossing altitude: 1500 ft (was 1600 ft)
MAP: 4.1 nm past FAF (but not charted as a DME fix)
MDA: 660 ft MSL/287 ft HAT (was 800 ft MSL)

The LOC trapezoids are quite narrow in close, so such a low MDA
is possible at a place where it is flat, close in. The MDA in theory could be
as low as 250 feet if there were no obstacles higher than the TDZ elevation and
the addition of the basic 230 feet of required obstacle clearance to the MSL
value of the TDZ results in a number ending in 20-foot increments so it doesn't
need to be rounded up.

It's entirely possible that the MDA used to be this low a few years ago,
before I started flying. The airport recently finished construction of a
new terminal, and cranes (etc.) might have pushed up the MDA for a few years.

None of the other localizer-based approaches has such a low MDA. The
LOC-only 07 MDA is 388 ft HAT, the LOC-only 32 MDA is 429 ft HAT (both are
200 ft with the ILS, of course), and the LOC(BC)/DME or LOC(BC)/NDB 14 MDA
is 480 ft HAT. As I mentioned, the LOC(BC) 25 is the most important NPA
operationally, so they must have gone to extra trouble to ensure that there
were no obstructions. I'd love to know the history from anyone who has been
flying into CYOW longer than I have.


Thanks, and all the best,


David

Ron Rosenfeld wrote:

There's no stepdown fix inside the FAF. The FAF is at an NDB 4.1 miles
from the runway (MAP). The FAF altitude is 1500' (MSL). AGL at the FAF is
not charted (JEPP).

They do have HIRL, ALS and PAPI. Can you get lower minimums with the
addition of lighting?

I'd be surprised, simply because you can descend to 287 ft HAT *without*
seeing the PAPI, approach lights, or runway edge lights.

AGL at the FAF is not charted in the Nav Canada CAP either, but it would be
roughly 1200ft (the terrain is very level in that direction, and the three
nearest towers on the VNC confirm that the ground elevation is around 300 ft
MSL).


All the best,


David

Ron Rosenfeld wrote:

On Sat, 22 Nov 2003 01:56:56 -0800, wrote:

Not having access to the chart, I can only presume they got lower minimums with
a stepdown fix. The LOC trapezoids are quite narrow in close, so such a low MDA
is possible at a place where it is flat, close in. The MDA in theory could be
as low as 250 feet if there were no obstacles higher than the TDZ elevation and
the addition of the basic 230 feet of required obstacle clearance to the MSL
value of the TDZ results in a number ending in 20-foot increments so it doesn't
need to be rounded up.

There's no stepdown fix inside the FAF. The FAF is at an NDB 4.1 miles
from the runway (MAP). The FAF altitude is 1500' (MSL). AGL at the FAF is
not charted (JEPP).

They do have HIRL, ALS and PAPI. Can you get lower minimums with the
addition of lighting?

Lower visibility, but not lower MDA or DA/H.

David Megginson wrote:

wrote:

Not having access to the chart, I can only presume they got lower minimums with
a stepdown fix.

Yes, it's unfortunate that Canadian approaches cannot be published for free
online like US ones are. The airport recently installed a DME to replace
the old UUP TRACON, but it's not used in the approach except as an
alternative way of identifying the FAF (the OW NDB) -- there are no
step-down fixes past the FAF. Here's a summary of the approach, leaving out
published transitions and the missed approach instructions:

IAF: OW NDB
MSA: 2900 ft (N), 2100 ft (S), based on OW (MSA is operational in Canada)
PT altitude: 2500 ft
FAF: OW NDB
FAF crossing altitude: 1500 ft (was 1600 ft)
MAP: 4.1 nm past FAF (but not charted as a DME fix)
MDA: 660 ft MSL/287 ft HAT (was 800 ft MSL)

The LOC trapezoids are quite narrow in close, so such a low MDA
is possible at a place where it is flat, close in. The MDA in theory could be
as low as 250 feet if there were no obstacles higher than the TDZ elevation and
the addition of the basic 230 feet of required obstacle clearance to the MSL
value of the TDZ results in a number ending in 20-foot increments so it doesn't
need to be rounded up.

It's entirely possible that the MDA used to be this low a few years ago,
before I started flying. The airport recently finished construction of a
new terminal, and cranes (etc.) might have pushed up the MDA for a few years.


A long-term crane would make sense.


None of the other localizer-based approaches has such a low MDA. The
LOC-only 07 MDA is 388 ft HAT, the LOC-only 32 MDA is 429 ft HAT (both are
200 ft with the ILS, of course), and the LOC(BC)/DME or LOC(BC)/NDB 14 MDA
is 480 ft HAT. As I mentioned, the LOC(BC) 25 is the most important NPA
operationally, so they must have gone to extra trouble to ensure that there
were no obstructions. I'd love to know the history from anyone who has been
flying into CYOW longer than I have.

I can't speak for Canada but the FAA has limited authority over off-airport
obstacles. It is usually up to the airport authority and the community to prevent
obstacles that will cause havoc with IAPs.

On 2003-11-22 04:51:46 -0800, David Megginson said

The airport recently installed a DME to replace
the old UUP TRACON...

Something tells me you mean TACAN. DME might be helpful, but I'v
yet to have one give me a radar vector

--
Larry Fransso
Seattle, WA

Larry Fransson wrote:
On 2003-11-22 04:51:46 -0800, David Megginson said:


The airport recently installed a DME to replace
the old UUP TRACON....


Something tells me you mean TACAN. DME might be helpful, but I've
yet to have one give me a radar vector!

You're right. That was a funny slip, actually.


All the best,


David

David,

St. John's, Newfoundland (CYYT) LOC(BC) 34 has an MDA of 255 ft.
There are a few other non-precision ones with less than 300 ft. in the
Maritimes, mostly because the approach is over water, I suppose.
The highest approach I know of is Faimont Hot Springs, B.C. (CYCZ) NDB
A with an MDA of 6322 ft.

Gerd
T182 C-FDOW