Subject: Re: Learning to land
Original from: Borislav Deianov
Marc Chametzky wrote:
>
> On the good side, sometimes (maybe 1/4 of them so far) the landings
> have been decent, so there's some hope out there. What I really need
> to work on is A) learning how much to pull back on the yoke in order
> to get and maintain the right attitude before flaring, and B) using
> the rudder to stay lined up with the center line on the runway. I
> sure am glad that the runway I'm doing my practicing on is 10,000' x
> 180'!
Let me first describe the perfect landing. You are gliding down your
final approach at a steady speed which is a certain factor above stall
speed (say 1.3*Vso). At a certain altitude above the ground you start
pulling back on the yoke and continue to move it back smoothly and
continuously until three things happen simultaneously: 1) your
altitude AGL goes down to zero; 2) your descent rate is reduced to
zero; 3) your airspeed is down to your stall speed.
Pulling back on the yoke achieves two things: it slows your descent
rate and it reduces your airspeed. There is a limit to both effects
and the trick is to time everything so that you reach but not exceed
that limit.
Now let's see what are the various ways a landing can go wrong:
- Your altitude goes down to zero but you still have a substantial
descent rate, resulting in a hard landing. You didn't pull the yoke
back far enough or fast enough and 1) happened before 2). There's no
way to recover from this as you have already hit the runway.
- Your descent rate goes down to zero but you are still high above the
ground. You pulled the yoke too far back too soon and 2) happened
before 1). An extreme case of this is when your descent rate becomes a
climb rate - you balloon. Depending on your altitude and airspeed at
this point you may or may not be able to recover the landing but a
better plan is to just go around. The alternative is a likely stall
high above the ground and a hard drop to the runway.
- Your descent rate goes down to zero exactly when your altitude goes
down to zero but your airspeed is still well above stall. Your initial
approach airspeed was too high or you started the flare too late and
1) and 2) happened simultaneously but before 3). This situation is
actually not so bad, provided you have some runway available. Just
keep pulling back on the yoke flying level just above the runway
(altitude and descent rate practically zero) until your airspeed
bleeds off to stall speed. This is the situation that the often given
advice "don't let the plane land" applies to.
Note that nobody is perfect and when I say "zero" and "simultaneously"
above I really mean "small enough" and "more or less at the same
time". It's OK to still have a small descent rate at touchdown or to
stall it a few inches above the ground or to float down the runway for
a few seconds bleeding off airspeed. The problems come when the few
seconds become many or the inches become feet.
OK, so how do you make a perfect landing?
Let's first work and making 1) and 2) happen simultaneously (zero
descent rate at touchdown). No, staring at the altimeter and the VSI
is not going to work. You need to be able to visually judge your
altitude above the ground. This is done on a subconscious level (you
don't need to come up with a number) but you do need to give your
brain enough visual cues to work with. There are several ways to this
and depth perception (3-D vision) isn't one of them. It just doesn't
work very well beyond a few feet.
One way which does work is using the runway edges. Notice where the
runway edges intersect the sides of the windshield while the plane is
sitting on the runway before takeoff. This is the picture you'll have
at the moment of touchdown. The lower and closer together the edges
are in the windshield during the approach, the higher you are. They
start spreading out while you are descending. You can now stop
thinking about your altitude and just think about how far apart the
edges are.
Note that runway width matters here. If the runway is too wide, the
edges are practically at your eye level during the last few critical
feet at the descent and make it really hard to judge your altitude
accurately. A narrower runway will help a lot with this. Seriously! A
width of 50 to 75 feet seems to work well in most trainers. If you
have no choice but to practice on a 180' wide runway, a trick is to
use only half the width, using one edge and the center line as your
runway edges.
Fine, so now you can judge altitude without thinking too much about
it. Again, you don't need to be able to spit out numbers, just to be
able to say "still high", "getting close" and "touch down right about
now". Once you can do this, it's fairly easy to make your 1) and 2)
goal happen simultaneously. Just keep pulling back on the yoke so that
the closer you get to the ground, the slower you descend. If you
notice that you are descending very slowly but you are still high,
just pull a little less for a bit. If you are getting very close but
still descending fast, pull harder. Getting this process smooth (so
that you are pulling back on the yoke at a constant and continuous
rate) takes lots of practice but just getting to the point where 1)
and 2) happen together isn't too hard. It's necessary to learn to be
smooth. No jerks, even in the beginning.
You are now at the point where you can make a greaser every time. A
greaser is not necessarily a perfect landing. For a perfect one, you
need to touch down at stall speed, without much float.
Touching down at stall speed (basically as slow as possible) is always
a good thing - helps reduce the wear on the tires. Touching down
without much float is important on short field landing. The length of
runway you float over is wasted. For a normal landing on a long runway
you don't need to worry about the float. Just keep pulling the yoke
back and don't let the plane land. It'll land by itself when it's
ready - right at stall speed. In this case 3) happens after 1) and 2)
and that's OK.
On a short field landing making 3) happen at the same time as 1) and
2) becomes most important. You really can't afford to float down the
runway bleeding off airspeed if you don't have much runway to start
with. You can influence this in two ways: correct approach speed and
flare began at the correct altitude. That's why the recommended
approach speed for a short field landing is usually somewhat slower -
it allows you to flare normally but avoid the float. Alternatively,
you can start your flare sooner (higher), bleeding off more airspeed
in the process. Timing this perfectly takes practice.
Notice that in this whole discussion of the flare I didn't mention
pitch attitude once. You keep pitching up but it's not the attitude
you use to judge and execute the maneuver. Your final attitude is
actually important - you want to land on the mains first so that they
can absorb any residual descent rate before the weaker nose wheel hits
the ground. You'll find, however, that if you correctly execute the
flare as described above, you'll have a nice nose-high attitude at the
moment of touchdown. No need to worry about it separately.
In all this I'm assuming you are flying a nose wheel airplane. Landing
a taildragger is essentially the same but the description would be
slightly different.
Hope this helps :-)
Boris
-- end of forwarded message --
Best regards,
Jer/ "Flight instruction and mountain flying are my vocation!" Eberhard
--
Jer/ (Slash) Eberhard, Mountain Flying Aviation, LTD, Ft Collins, CO
CELL 970 231-6325 EMAIL jer'at'frii.com WEB http://www.frii.net/~jer
C-206 N9513G, CFII Airplane&Glider, FAA-DEN Aviation Safety Counselor
CAP-CO Mission&Aircraft CheckPilot, BM218 HAM N0FZD, 197 Young Eagles!