"Roy Smith" wrote in message
...
The most critical airspeed in the pattern is your final approach speed.
Everything else is just executing a controlled transition from cruise
speed to final approach speed. For most light planes, if you fly base
10 kts faster than final, and downwind 10 kts faster than base, you
should be doing OK. This should give you a good target speed for
downwind.

Means and ends are in the eye of the beholder. The way I look at the
pattern, what's really important are airspeed and altitude. Power settings
allow me to adjust either, but once I've begun my descent (usually from
abeam the numbers, but not always depending on traffic concerns) power
settings are just a way to get the *altitude* I want, and the descent angle
I want. I use my pitch controls (elevator and elevator trim) to adjust
airspeed at that point.

Of course, they all interact. It's like asking "Bernoulli or Newton". But
don't discount someone else's mental paradigm just because it's different
from yours.

The point that started this whole subthread was simply that students (and
even full-fledged pilots for that matter) can fixate on setting a particular
RPM, when that's not really all that important. A particular RPM setting is
only going to work on a "standard pattern day" (i.e. no wind, no traffic,
exactly 800' or 1000' or whatever feet AGL you pick as standard, turns at
precisely 45 degrees and final, etc.).

Any variation from this standard is going to require adjustments to throttle
to maintain the desired performance for the conditions. So why waste time
and concentration getting the throttle at exactly some particular setting,
when getting it in the ballpark using muscle memory (i.e. general knowledge
of the "correct" position) and audible feedback (sound of the engine)?

I believe that Bob was saying just that, and I think his comment was right
on the mark. It's funny the turns this thread has taken, but I disagree
with Rob's attachment to precision in this case (even though I do generally
believe that precise control of the aircraft is very important), and I don't
understand what debating the *actual* specific RPM settings does to address
the original point.

The problem is, you can't set airspeed directly, you can only set power.

I beg to differ. I set the airspeed all the time. I can manipulate the
elevator directly to obtain the desired airspeed, and I can then set the
trim to allow the airspeed to remain at that desired.

So, it's a good idea to have a target power setting for downwind. For
most typical trainers, somewhere in the 1900-2100 RPM range is about
right, but ask your instructor for a good number to use for whatever
you're flying. You set that when entering the pattern (along with
whatever other configuration changes you're going to make, like gear and
flaps), and give the plane a little time to settle into a stable
airspeed. Then you can adjust the power if needed if you didn't get the
airspeed you wanted.

If you simply adjust power, you won't get the airspeed you want, ever (well,
not counting a sudden decelleration at the end of a descent induced by a
power reduction). You have to change your pitch in order to get a new
airspeed that will produce the performance you want at the new power
setting.

More relevant to where this subthread started, yes it's good to have a
target power setting for downwind, and for the descent as well. But there's
no need to spend 30 seconds (or whatever) fiddling with the throttle to get
the power setting "just so". You smoothly, calmly, and quickly set the
throttle to the general vicinity of the correct spot, and then make
adjustments as necessary during the approach. Adjustments you would have to
even if you managed to hit the exact throttle setting you had targeted.

Pete