Winds on approach

I flew yesterday and did some practice approaches, and the winds were
about 20 knots gusting to 26-28. I've flown almost all approaches so
far in a different 172 that had a 180hp conversion. Because of the
winds, I kept almost full cruising power on the descents to try and
maintain my normal 90 kts ground speed for timing and roughly 500fpm
for the ILS.

This plane did have an IFR GPS indicating ground speed, but the one
I've been using for all other approaches didn't, neither DME. The CFI
informed me I should have used known power settings. What are your
thoughts? I'm not sure how I would've known the right power setting,
unless I used what I normally do, and accept the lower ground speed,
then adjust my descent for the ILS to a much lower fpm descent?

On 03/29/07 12:59, kevmor wrote:
I flew yesterday and did some practice approaches, and the winds were
about 20 knots gusting to 26-28. I've flown almost all approaches so
far in a different 172 that had a 180hp conversion. Because of the
winds, I kept almost full cruising power on the descents to try and
maintain my normal 90 kts ground speed for timing and roughly 500fpm
for the ILS.

This plane did have an IFR GPS indicating ground speed, but the one
I've been using for all other approaches didn't, neither DME. The CFI
informed me I should have used known power settings. What are your
thoughts? I'm not sure how I would've known the right power setting,
unless I used what I normally do, and accept the lower ground speed,
then adjust my descent for the ILS to a much lower fpm descent?



I was taught that you should use the proper power settings during the
approach. I would not change these due to my expectation of ground
speed. However, with a higher than standard ground speed, you will
have to adjust your descent rate to maintain the proper glide path.

Here's a question for you to think about. If you have a tail wind which
results in a ground speed of 95 knots, do you need to use the category 'B'
approach minimums?


--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

I think I should clarify a couple things from the original post, it
was a headwind on the approach, and I also did a VOR, LOC, and GPS.

If I used the normal power settings, then on the ILS I could just
reduce my descent rate. After reading what you guys said, this should
be fine unless I'm told to fly it faster. But either way, on the ILS
if the needles are centered, you're good.

On the others though, if I kept power at the normal settings with the
headwind, I would've descended to the MDA further out... to me this
seems like an added risk... For timing these, if I didn't have an IFR
GPS or DME (they're new to me), how should I figure the ground speed
for timing?

On Mar 29, 1:16 pm, Mark Hansen wrote:
I was taught that you should use the proper power settings during the
approach. I would not change these due to my expectation of ground
speed. However, with a higher than standard ground speed, you will
have to adjust your descent rate to maintain the proper glide path.

Here's a question for you to think about. If you have a tail wind which
results in a ground speed of 95 knots, do you need to use the category 'B'
approach minimums?

On the others though, if I kept power at the normal settings with the
headwind, I would've descended to the MDA further out... to me this
seems like an added risk... For timing these, if I didn't have an IFR
GPS or DME (they're new to me), how should I figure the ground speed
for timing?

As long as you are above the minima, and past any stepdown fixes, you're
ok. (This is one reason localizer minima are higher.) And being down
early gives you a better chance to break out to visual, and maybe fly
around the one cloud that would otherwise be in the way.

To figure ground speed, subtract the headwind from the airspeed. It
will be close enough.

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.

Jose wrote:

As long as you are above the minima, and past any stepdown fixes, you're
ok. (This is one reason localizer minima are higher.) And being down
early gives you a better chance to break out to visual, and maybe fly
around the one cloud that would otherwise be in the way.

I agree. Don't change the power settings. The descent on a
non-precision approach for step downs is fairly rapid in all
circumstances. A headwind is usually less of a problem.
A tailwind may mean that you don't get to the MDA or stepdown
altitude in time.

The bigger is adjusting your times for things like the
distance from passing a fix before starting the PT and
the times flown in the PT's. With a tail wind you
can end up doing the PT uncomfortably close in if you
don't extend the time. Then add to that you are
being pushed down the final course rapidly, things
might happen too fast.

Admittedly the moving map is a big crutch not just
because it gives you the distances but it also gives
you the ground speed read out which lets you pick
the times more easily.

On Mar 29, 3:59 pm, "kevmor" wrote:
I flew yesterday and did some practice approaches, and the winds were
about 20 knots gusting to 26-28. I've flown almost all approaches so
far in a different 172 that had a 180hp conversion. Because of the
winds, I kept almost full cruising power on the descents to try and
maintain my normal 90 kts ground speed for timing and roughly 500fpm
for the ILS.

Why does ground speed matter? Why does the 500fpm matter?

This plane did have an IFR GPS indicating ground speed, but the one
I've been using for all other approaches didn't, neither DME. The CFI
informed me I should have used known power settings.

I agree.

What are your
thoughts? I'm not sure how I would've known the right power setting,
unless I used what I normally do, and accept the lower ground speed,
then adjust my descent for the ILS to a much lower fpm descent?

What's wrong with a much lower descent rate? All that matters is that
you keep your needles centered. Did you have faster traffic behind
you and you increased speed as a courtesy? I presume you wanted to
maintain 90 kts so that you could time the approach, but aside from it
being an ILS where it doesn't matter, your GPS could tell you where to
go missed if your glide slope goes TU.

It's probably a good idea to know the power settings for some high speed
descent/approach. Like if you are asked to do maximum speed on approach
or something like that. As long as you can handle it and can get the
time right then no problem.

kevmor wrote:
I flew yesterday and did some practice approaches, and the winds were
about 20 knots gusting to 26-28. I've flown almost all approaches so
far in a different 172 that had a 180hp conversion. Because of the
winds, I kept almost full cruising power on the descents to try and
maintain my normal 90 kts ground speed for timing and roughly 500fpm
for the ILS.

This plane did have an IFR GPS indicating ground speed, but the one
I've been using for all other approaches didn't, neither DME. The CFI
informed me I should have used known power settings. What are your
thoughts? I'm not sure how I would've known the right power setting,
unless I used what I normally do, and accept the lower ground speed,
then adjust my descent for the ILS to a much lower fpm descent?

What are your
thoughts? I'm not sure how I would've known the right power setting,
unless I used what I normally do, and accept the lower ground speed,
then adjust my descent for the ILS to a much lower fpm descent?

Exactly. Airspeed is what's crucial for aircraft control. Ground speed
is just used for timing. Adjust the timing. If it's gusty, you might
want a slightly higher airspeed, just like for VFR landings in gusty winds.

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.

You are timing your ILS approaches? Any reason for this? I can't find
anything in my 172P book that suggests 90 kts as an approach speed, even in
gusty winds. Seems fast to me.

Bob Gardner

"kevmor" wrote in message
ups.com...
I flew yesterday and did some practice approaches, and the winds were
about 20 knots gusting to 26-28. I've flown almost all approaches so
far in a different 172 that had a 180hp conversion. Because of the
winds, I kept almost full cruising power on the descents to try and
maintain my normal 90 kts ground speed for timing and roughly 500fpm
for the ILS.

This plane did have an IFR GPS indicating ground speed, but the one
I've been using for all other approaches didn't, neither DME. The CFI
informed me I should have used known power settings. What are your
thoughts? I'm not sure how I would've known the right power setting,
unless I used what I normally do, and accept the lower ground speed,
then adjust my descent for the ILS to a much lower fpm descent?

You are timing your ILS approaches? Any reason for this? I can't find
anything in my 172P book that suggests 90 kts as an approach speed, even in
gusty winds. Seems fast to me.

IF one times their ILS, and loses the glideslope, one can often convert
to a localizer approach easily. And approach plates give canned timings
for various speeds, 90 knots is probably the best of the bunch for a
172. Of course that's ground speed, not airspeed.

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.