Tweaking the throttle on approach

Is it normal to constantly fiddle with the throttle on an approach in a small
plane? I find myself frequently making small adjustments on most approaches
(unless I'm coming absolutely arrow-straight into the runway and there's no
wind). From videos I've seen, this happens in real aircraft, too, depending
on conditions. I was under the impression that a steady throttle is ideal,
but perhaps that is hard to achieve in a small aircraft.

I don't have a problem in large jets--they take forever to answer the
throttle, anyway.

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On Mar 4, 10:50 am, Mxsmanic wrote:
Is it normal to constantly fiddle with the throttle on an approach in a small
plane? I find myself frequently making small adjustments on most approaches
(unless I'm coming absolutely arrow-straight into the runway and there's no
wind). From videos I've seen, this happens in real aircraft, too, depending
on conditions. I was under the impression that a steady throttle is ideal,
but perhaps that is hard to achieve in a small aircraft.

I don't have a problem in large jets--they take forever to answer the
throttle, anyway.

A typical approach in my Cherokee includes at least a few minor power
adjustments after the main power reduction on downwind, abeam the
numbers. They are not usually large, probably +/- 100 rpm. I usually
attribute this to variable wind (speed and direction) between traffic
pattern altitude and ground. Some days, the wind varies considerably
on the way down, and larger, or more frequent power changes are
needed. On those rare wind-free days (i.e., from the surface up to
1000 AGL), I can set power at 1500 rpm on downwind, apply flaps in my
normal places in the pattern, and usually hit the runway nearly where
I want without any power adjustments.

writes:

A typical approach in my Cherokee includes at least a few minor power
adjustments after the main power reduction on downwind, abeam the
numbers. They are not usually large, probably +/- 100 rpm. I usually
attribute this to variable wind (speed and direction) between traffic
pattern altitude and ground. Some days, the wind varies considerably
on the way down, and larger, or more frequent power changes are
needed. On those rare wind-free days (i.e., from the surface up to
1000 AGL), I can set power at 1500 rpm on downwind, apply flaps in my
normal places in the pattern, and usually hit the runway nearly where
I want without any power adjustments.

The Baron has a CS prop so I can't watch RPM. I guess I could look at
manifold pressure. However, I've been going mostly by sound to determine how
much power I have applied. What surprises me is that I can tell what changes
to make at all, given that there is no sensation in simulation. But I guess
after a while looking out the window gives me enough clues--as well as
checking instruments, but often I'll adjust power before I see a change in the
instruments.

In some videos I've seen there is constant change in the power setting.
Granted, a lot of these seem to have been on windy days or in mountain
settings.

In big iron I've learned the hard way not to constantly move the throttles
forward and back. I have to just move them a little and be patient. Small
aircraft respond immediately, which is nice (but it spoils you if you like to
fly both aircraft).

I've read about being in a stable configuration on approach and that this is a
Good Thing, but I'm not sure if that applies across the board for all aircraft
and approaches, or just for straight-in approaches, or what. I think it would
be quite a feat to be able to fly a pattern and land without hardly ever
touching the throttles, except perhaps on the kind of windless day that only
occurs in simulators. I can get the aircraft into a stable configuration on
approach if the weather is good and I'm coming straight in, but doing it while
flying a pattern seems unattainably difficult at times.

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On Mar 4, 12:02 pm, Mxsmanic wrote:

The Baron has a CS prop so I can't watch RPM. I guess I could look at
manifold pressure. However, I've been going mostly by sound to determine how
much power I have applied.

I don't know what CS prop guys do, but in my fixed-pitch prop, I
always make my initial power reduction based on RPM, I set it to 1500
and then adjust from there, based on the resulting approach. I
suspect that with a CS prop, some initial RPM/Manifold Pressure
combination is selected.

I have found that flying a normal rectangular pattern in the sim is
significantly more difficult than in real flight. In the real plane,
I compare my actual position to my desired position by frequently
glancing at the desired touchdown point on the runway. I find this
very difficult to do in the sim, I think because of the difficultly in
getting realistic view of the runway from the various legs of the
pattern (?). However, once established on final approach, I think the
sim is quite good in reproducing the sight picture of the approach.
In a light plane, the standard technique is to hold airspeed constant
(usually by trimming to that speed), and then fine tune the flight
path angle with small power adjustments.

But I guess
after a while looking out the window gives me enough clues--as well as
checking instruments, but often I'll adjust power before I see a change in the
instruments.

In a normal approach, started from downwind in the traffic pattern,
once the initial power reduction is made, I make the rest of the
approach mostly without looking at the instruments, except for several
checks of airspeed. The descent to the runway is done visually.
Also, don't forget that in the real plane your attention will be
mostly devoted to looking for and avoiding other aircraft.

I've read about being in a stable configuration on approach and that this is a
Good Thing, but I'm not sure if that applies across the board for all aircraft
and approaches, or just for straight-in approaches, or what. I think it would
be quite a feat to be able to fly a pattern and land without hardly ever
touching the throttles, except perhaps on the kind of windless day that only
occurs in simulators. I can get the aircraft into a stable configuration on
approach if the weather is good and I'm coming straight in, but doing it while
flying a pattern seems unattainably difficult at times.

If you want to be realistic in the sim, then you should try to fly the
traffic pattern for most of your visual approaches. (This includes
instrument approaches to small airports in visual conditions; break
off the approach a few miles out and join the pattern normally.) I
agree about the difficulty of setting up a good approach from the
pattern in the sim. You need to find a set of zero-wind numbers that
works for your sim aircraft, e.g., power setting on downwind, initial
power reduction, time until you turn base, position where flaps are
applied, airspeed on final, etc. (Timing your turn to base may work
better for the sim than the real-life technique of waiting for 45
degrees from touchdown point). You may have to find them by trial and
error, but once you have them, they become your starting point for all
subsequent approaches; fly by those numbers, and then make adjustments
for wind, and other factors of the specific situation.

writes:

I have found that flying a normal rectangular pattern in the sim is
significantly more difficult than in real flight. In the real plane,
I compare my actual position to my desired position by frequently
glancing at the desired touchdown point on the runway. I find this
very difficult to do in the sim, I think because of the difficultly in
getting realistic view of the runway from the various legs of the
pattern (?).

I had tremendous trouble seeing the runway for a long time. Finally, when I
got a joystick with a twist axis, I eventually assigned the twist axis to the
pan function in MSFS, so that I can "look" in various directions by twisting
the throttle as I fly. It works pretty good, and I'm better now at patterns
than I used to be. I don't know how much of this modest improvement is due to
practice and how much is due to being able to "turn" my head, though.

However, once established on final approach, I think the
sim is quite good in reproducing the sight picture of the approach.
In a light plane, the standard technique is to hold airspeed constant
(usually by trimming to that speed), and then fine tune the flight
path angle with small power adjustments.

Unfortunately I tend to be impatient in the sim and I'm often still not
aligned even as I cross the threshold, unless I planned to land at that
airport well ahead of time. I usually come in fast because I'm making rather
risky turns on the approach and I don't want to come too close to a stall.

In a stabilized approach, though, I'm better.

How do you trim to a speed? Especially when you are adjusting power?

In a normal approach, started from downwind in the traffic pattern,
once the initial power reduction is made, I make the rest of the
approach mostly without looking at the instruments, except for several
checks of airspeed. The descent to the runway is done visually.
Also, don't forget that in the real plane your attention will be
mostly devoted to looking for and avoiding other aircraft.

What airspeed do you choose for landing?

If you want to be realistic in the sim, then you should try to fly the
traffic pattern for most of your visual approaches. (This includes
instrument approaches to small airports in visual conditions; break
off the approach a few miles out and join the pattern normally.) I
agree about the difficulty of setting up a good approach from the
pattern in the sim. You need to find a set of zero-wind numbers that
works for your sim aircraft, e.g., power setting on downwind, initial
power reduction, time until you turn base, position where flaps are
applied, airspeed on final, etc. (Timing your turn to base may work
better for the sim than the real-life technique of waiting for 45
degrees from touchdown point). You may have to find them by trial and
error, but once you have them, they become your starting point for all
subsequent approaches; fly by those numbers, and then make adjustments
for wind, and other factors of the specific situation.

Hmm ... I had not thought of working out numbers that I could reuse. Each
approach has been trial and error but I haven't been noting anything. I guess
I'll have to write stuff down (or at least try to remember it). I do have a
few things memorized for the Baron, after hundreds of hours in it, but not as
much as I probably need or could use.

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Mxsmanic wrote:

Unfortunately I tend to be impatient in the sim and I'm often still not
aligned even as I cross the threshold, unless I planned to land at that
airport well ahead of time. I usually come in fast because I'm making rather
risky turns on the approach and I don't want to come too close to a stall.

The benefit of your simulator is that it doesn't destroy the landing
gear on your sloppy landings and that is why it is nothing like real
life. It lets you get away with the most terrible landings... (It always
says excellent landing to me but that's not what my instructor ever says
-and he's right I'd give myself typically 5-8/10). Based on your
extolling the virtues of MSX I recently got the latest version and tried
it out with the aircraft I'm training on. Basically I'd have to say it
simulates a C172 very poorly and I'd say it's only use is for simulated
instrument flying. Even so, it's response does not mimic my aircraft
near the limits of the flight envelope -it behaves like a flying game
really. Red Bull flying race? What a pile!

Mark

Hi, just a couple of notes:

Unfortunately I tend to be impatient in the sim and I'm often still not
aligned even as I cross the threshold, unless I planned to land at that
airport well ahead of time. I usually come in fast because I'm making rather
risky turns on the approach and I don't want to come too close to a stall.


A good landing starts with a good approach. If you don't get your
approach sorted out you are almost certain to stuff the landing up.


What airspeed do you choose for landing?


A good airspeed for crossing the fence is VSo x 1.3. Find out what
your stall speed is, multiply by 1.3 and you have your speed at short
finals. You can add a bit for the early part of the approach, for a
172 you might use 70-80 kt on approach, reducing to 55 kt on short
finals. Whatever light aircraft you fly will be similar, can't speak
for the heavies though.. If you use much more than 80kt on approach
it can be difficult to get rid of the speed while still descending.

Stall speeds are affected by weight, so if you are heavy the 55kt will
become more like 66kt..

On Mar 5, 10:11 am, Mxsmanic wrote:
Unfortunately I tend to be impatient in the sim and I'm often still not
aligned even as I cross the threshold, unless I planned to land at that
airport well ahead of time. I usually come in fast because I'm making rather
risky turns on the approach and I don't want to come too close to a stall.

If not aligned at the threshold in a real plane, you should go around.
You should strive to become aligned with the centerline soon after
turning onto final, and then hold it there. It can be done with
practice. Don't forget you'll need a crab angle to take care of
crosswind.


How do you trim to a speed? Especially when you are adjusting power?

Don't try to do both at the same time. Hold power constant, and
adjust pitch with the yoke until you are at your desired airspeed,
then apply trim until you can release the yoke without the pitch
attitude (and therefore, airspeed) changing. Then with the airspeed
stabilized, adjust power to change the rate of descent, small changes
in power won't affect your airspeed.


What airspeed do you choose for landing?

You need the proper speed for your aircraft. If it's not available in
the Pilot's Operating Handbook, then use an old rule of thumb, set the
airspeed equal to 1.3 times the aircraft's stall speed. Your aircraft
should be slowed to this speed by the time you turn final, and then
hold it precisely at that speed. The normal way to hold airspeed is
by trimming to that speed in pitch.


Hmm ... I had not thought of working out numbers that I could reuse. Each
approach has been trial and error but I haven't been noting anything. I guess
I'll have to write stuff down (or at least try to remember it). I do have a
few things memorized for the Baron, after hundreds of hours in it, but not as
much as I probably need or could use.

You will not achieve consistent landings until you can fly a
stabilized approach. To do this, you need to discover the numbers for
your aircraft, and then use them. To find them, I suggest you conduct
some experiments in the sim. Set up your aircraft in level flight on
downwind, constant speed, gear down, at 1000 ft AGL, with a medium
power setting. When opposite the numbers, lower your flaps to their
first setting (or 10 deg) and reduce power until you stabilize at a
500 ft/min descent rate with the airspeed at 1.5 times stall speed.
Record the power setting and airspeed. Use those numbers for your
initial descent from the pattern. After 30 seconds, turn base and
lower flaps to the second setting and set pitch for airspeed = 1.4
times stall speed. Then turn final, lower flaps completely, and set
pitch for 1.3 times stall speed. Fly it like this until you hit the
ground. If you land long, then reduce power a little more next time.
If you land short, add a little power next time. Keep iterating until
you zero in on the right numbers.

On 5 Mar 2007 05:11:10 -0800, wrote:

On Mar 4, 12:02 pm, Mxsmanic wrote:

The Baron has a CS prop so I can't watch RPM. I guess I could look at
manifold pressure. However, I've been going mostly by sound to determine how
much power I have applied.

I don't know what CS prop guys do, but in my fixed-pitch prop, I

Depends on how well you know your plane.

always make my initial power reduction based on RPM, I set it to 1500
and then adjust from there, based on the resulting approach. I
suspect that with a CS prop, some initial RPM/Manifold Pressure
combination is selected.

With the Deb my initial power reduction is made well before I'm turned
down wind. I leave the RPM alone at 2400. The idea is to get slowed to
somewhat less than 140 (which is the maximum gear down speed) when I
straighten out and down to about 110 as I pass the end of the runway
outbound. Depending on temperature and particularly density altitude
the power settings can change quite a bit. Note, with the gear up the
glide ratio is about twice that of a 172. With the gear down it's even
steeper than a Cherokee 180 although it and the Cherokee have almost
the same wing loading. With the gear down you can pretty much think
of it as a big, heavy Cherokee that burns a lot of gas and isn't
nearly as forgiving.

In a stabilized pattern, which I seldom fly, I aim for 110 abeam the
numbers outbound, 90 on base and 80 on final slowing to 80 minus 1 MPH
for each 100# under gross. I run *about* 10-15 degrees of flaps down
wind, 20 to 25 on base, and 25 to 30 on final going to the full 40
when either needed or the runway is made.


I have found that flying a normal rectangular pattern in the sim is
significantly more difficult than in real flight. In the real plane,
I compare my actual position to my desired position by frequently
glancing at the desired touchdown point on the runway. I find this
very difficult to do in the sim, I think because of the difficultly in

The view in FSX is very realistic for the 172. OTOH you need a
state-of-the-art system to be able to run it. Development was started
before multi-core and multi-processors were even though of as becoming
popular. Hence it depends on raw horsepower to run things and gets by
with a fair to middlin graphics card. Not a cheap one, but you sure
don't need to go the big bucks for a top end DX-10 graphics card.
Anything much less than a top end machine will leave you CPU bound.
However even with SATA 3 drives it seems to take forever to load.

getting realistic view of the runway from the various legs of the
pattern (?). However, once established on final approach, I think the

I think this is the advantage FSX has over FS9. A flick of the "top
hat" gives you views that look pretty much normal.

sim is quite good in reproducing the sight picture of the approach.
In a light plane, the standard technique is to hold airspeed constant
(usually by trimming to that speed), and then fine tune the flight
path angle with small power adjustments.

But I guess
after a while looking out the window gives me enough clues--as well as
checking instruments, but often I'll adjust power before I see a change in the
instruments.


With the CS prop in the Deb I pretty much use the throttle to adjust
the aiming point and only reference the air speed to make sure it's
not drifting up or down.

The Deb takes a "light touch" on the controls so I set the trim and
then just sort of nudge it here and there.

Bumpy IFR in solid IMC it becomes a two finger control just nudging
the yoke


In a normal approach, started from downwind in the traffic pattern,
once the initial power reduction is made, I make the rest of the
approach mostly without looking at the instruments, except for several
checks of airspeed. The descent to the runway is done visually.
Also, don't forget that in the real plane your attention will be
mostly devoted to looking for and avoiding other aircraft.

Pretty much the same here whether IRL or sim.

I've read about being in a stable configuration on approach and that this is a
Good Thing, but I'm not sure if that applies across the board for all aircraft
and approaches, or just for straight-in approaches, or what. I think it would
be quite a feat to be able to fly a pattern and land without hardly ever
touching the throttles, except perhaps on the kind of windless day that only

I think I remember experiencing those a couple of times IRL.

occurs in simulators. I can get the aircraft into a stable configuration on
approach if the weather is good and I'm coming straight in, but doing it while
flying a pattern seems unattainably difficult at times.

And there in lies another difference between IRL and sim. If I were
flying into a big airport IRL I could pretty much set the power and
let it go, but the touch down point would vary over quite a distance.
As I normally fly into airports with 2500 to 3800 foot runways I don't
have that luxury so although I can fly a rectangular pattern and even
do each segment in the same place repeatedly It required adjustment of
power and flaps. Sometimes even a little slip is called for. :-)) On
really windy days it may call for substantial power on final.

If you want to be realistic in the sim, then you should try to fly the
traffic pattern for most of your visual approaches. (This includes
instrument approaches to small airports in visual conditions; break
off the approach a few miles out and join the pattern normally.) I
agree about the difficulty of setting up a good approach from the
pattern in the sim. You need to find a set of zero-wind numbers that
works for your sim aircraft, e.g., power setting on downwind, initial
power reduction, time until you turn base, position where flaps are
applied, airspeed on final, etc. (Timing your turn to base may work
better for the sim than the real-life technique of waiting for 45
degrees from touchdown point). You may have to find them by trial and
error, but once you have them, they become your starting point for all
subsequent approaches; fly by those numbers, and then make adjustments
for wind, and other factors of the specific situation.

Learn this first with the 172, then work with the bigger stuff.

Once lined up with the end of the runway add about half flaps and come
back on the power. Watch the touchdown zone. (white strips just down
the runway). If they are getting higher in the windshield add enough
power to stop them from moving up. If they are moving down, then
reduce the power. If they are still moving down, go full flaps. If
they are still moving up you are either too high, too fast, or both.
If you aren't going to be able to land in the first third of the
runway go around and try again. A good guide are the VASI lights with
the top ones being red and the bottom being white although IRL a lot
of pilots don't like to come in that shallow.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger writes:

Learn this first with the 172, then work with the bigger stuff.

I don't know if I can trust the sim's default version of the 172. The add-ons
I use have a reputation for extreme accuracy, so I can be reasonably confident
that they do just what the real aircraft does, but I don't know about the 172.
If I can find a reputable add-on C172, maybe I'll get that sometime. That's
the main reason I don't fly the 172 much.

I do have an A36 Bonanza, also by Dreamfleet, but the EHSI isn't Reality XP
(Reality XP is known for its 100% accurate instruments), and the EHSI on the
Baron is. I guess the EHSI wouldn't matter so much for pattern work, though.

Also I figure it's better to get good in a small number of aircraft than
mediocre in a large number, since in real life I probably wouldn't be flying
20 different aircraft, but just two or three at most.

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