Power-out spot landing techniques?

ls wrote:

The cheezy way to do it is to just dive a bit until the
glideslope flattens a bit and then resume your approach airspeed (although
not cheezy in my aircraft type which is incapable of slips - that's pretty
much my only option). Don't do this on the checkride or even with the CFI
on board - they'll slap you upside the head and with good reason. The much
better way is to use a slip or, if you're sure you have it made, adding
flaps, to accellerate energy dissipation and get you on glideslope without
building up too much airspeed.

What about slowing below best glide, but (obviously {8^) above stall?


If, on the other hand, you're having to hold too low of an airspeed to
keep the landing point from moving up, you don't have enough energy to
make it there and you're going to come up short.

This I don't follow. If the spot is steady, you're going to make the spot
at your current speed (assuming you're holding that speed, of course).

- Andrew

Andrew Gideon wrote in message ...
ls wrote:

The cheezy way to do it is to just dive a bit until the
glideslope flattens a bit and then resume your approach airspeed (although
not cheezy in my aircraft type which is incapable of slips - that's pretty
much my only option). Don't do this on the checkride or even with the CFI
on board - they'll slap you upside the head and with good reason. The much
better way is to use a slip or, if you're sure you have it made, adding
flaps, to accellerate energy dissipation and get you on glideslope without
building up too much airspeed.

What about slowing below best glide, but (obviously {8^) above stall?

In the old days CFIs taught the students to enter spins, first one
way, then the other. Each spin was recovered after only about 45
degrees of rotation. The resulting maneuver looked like a falling
leaf, thus the maneuver was named the "falling leaf". You could
probably lose your CFI ticket for teaching that now.

-Robert, CFI

What about slowing below best glide, but (obviously {8^) above stall?

No reason why that wouldn't work either. A friend of mine uses this
technique in his Citabria from time to time. I don't like to do this in my
airplane, though, because roll control becomes very heavy and slow (due to
yaw stability) at low airspeeds.

If, on the other hand, you're having to hold too low of an airspeed to
keep the landing point from moving up, you don't have enough energy to
make it there and you're going to come up short.

This I don't follow. If the spot is steady, you're going to make the spot
at your current speed (assuming you're holding that speed, of course).

Right. But, as I said (look again at the paragraph above), if the spot is
moving up and you don't have the energy to keep it from doing so, you're
going to come up short.

LS
AC fun racer 503.

- Andrew

In rec.aviation.student Andrew Gideon wrote:
ls wrote:

The cheezy way to do it is to just dive a bit until the
glideslope flattens a bit and then resume your approach airspeed (although

What about slowing below best glide, but (obviously {8^) above stall?

Here is a page that discusses both of the above techniques (from John
Denker's excellent online book on aerodynamics):

http://www.av8n.com/how/htm/power.ht...-energy-stunts

Neither is usually the best method of glide path control but it never
hurts to have more tools in your toolbox.

Boris

Borislav Deianov wrote:

Neither is usually the best method of glide path control but it never
hurts to have more tools in your toolbox.

I recently took a club checkout with someone that didn't want me to slip a
172 at full flaps, even for a (simulated) emergency landing. That leaves
me looking for alternatives for the upcoming retest. The "slow below best
glide" occurred to me one day as I was practicing short field landings.

- Andrew

On Tue, 12 Aug 2003 14:34:23 -0400, Andrew Gideon
wrote:

Borislav Deianov wrote:

Neither is usually the best method of glide path control but it never
hurts to have more tools in your toolbox.

I recently took a club checkout with someone that didn't want me to slip a
172 at full flaps, even for a (simulated) emergency landing. That leaves
me looking for alternatives for the upcoming retest. The "slow below best
glide" occurred to me one day as I was practicing short field landings.

OK...I'm gonna try a different approach...and I hope it makes sense to
some one.

Remember flying and particularly landing is all about "energy
management"! Power out, "spot landings" build on all you have learned
before. So, for those who already know all this you can skip wayyy
ahead, but a little review never hurts. Plus this is a Generic and
over simplified approach.

Depending on where you are there is nothing that says you have to come
in at best glide. OTOH you do have to remember speed and altitude are
both energy available to use, or dispense with as you see fit.

Although speed is kinetic energy and altitude is potential energy in
this case they both equate to pretty much the same thing.

You can exchange altitude for speed. IE, turn potential energy into
kinetic and "up to a point" you can trade speed for altitude
up-to-a-point. Turn kinetic back into potential energy.

Sometimes you need to get rid of potential energy (altitude) without
gaining kinetic energy (speed) and sometimes you need to get rid of
speed without losing (or gaining) a lot of altitude.

It's that "up-to-a-point" where you have to be careful, or it can get
you into trouble
..
There are limitations to this. You can only spend so much kinetic
energy safely. So figure the lower limit is 1.3 Vso. (or thereabouts)
Now the same is true for too much kinetic energy. Vne is self
explanatory, but in the pattern just how fast is too fast. We can
lower the speed a bit by saying we certainly don't want to be above
the flap extension speed (if you have them)..or is best glide above
flap speed. OK, so at least in most trainers it's not and we can
*probably* say we don't want to exceed flap speed.

Now we also have potential energy which is altitude and in reality we
don't have to spend a lot of altitude to get quite a bit of speed.
Hence the old tale about being able to come down, or slow down, but
not both. Again, in a trainer this usually isn't a *big* problem
unless we make it one either intentionally or unknowingly. Trainers
and many light planes have lots of drag which *usually* prevents the
potential energy from becoming too much kinetic energy.

Rephrased: You *almost* have to try to try to get too much speed out
of too much altitude in a trainer, although someone usually manages to
do so on almost a daily basis. So we know it can be done!

Soooo...having a nice stabilized pattern is a good goal for starters.
It's the basic building block for good landings. You have to be good
at landings to eventually become good at landing on a specific spot.
(repeatedly) Every one of us gets lucky now and then. Now and I know
it ain't fair, but to get good at engine out, spot landings we need to
be good (and consistent) at regular landings first.

So we start out for the elusive stabilized pattern on a good day (IE,
the mythical no wind day, which was usually yesterday)
You need to learn your down wind altitude, speeds, flap settings,
power settings, and how far out you should be from the runway.

Now, where do you turn base? *Usually* we turn base when the threshold
is at a 45 degree angle to the rear.

That puts us on base. You do know your speed, flaps settings, rate of
descent and power settings if applicable? Remember that the base leg
should be perpendicular to down wind and final and on a no wind day
should require no wind correction.

Now the turn to final from base. You need to lead the turn (start
before you are straight out from the runway) so when you finish
turning 90 degrees you are lined up with the runway. Again, it's
speed, flaps, and power.

Now is where we look for that greasy spot in the windshield.
Some of us use the whole windshield...OK, so we need to wash it more
often....What we look for is whether the desired aiming point which
should be at least a 100 feet short of the desired landing point
(It'll vary with different airplanes), stays in the same position, or
moves up, or moves down in the windshield.

As many have already said...If the aiming point stays put..Yippi!
That's great. OTOH if it moves down in the windshield it means you are
going to land beyond the aiming point and need to slow a bit, or
steepen you angle of descent. Unfortunately steepening the angle of
descent *usually* means we are going to trade some altitude for speed.
Hence you can't just dive at the at the aiming point or you will gain
so much speed that when you level off you will just float and float
and float right on buy the aiming point, the landing point, and who
knows what else. He who forces the plane on before "it's ready" will
end up imitating a big fish called a Porpoise. This irritates the
living bejusus out of the FBO who rented the plane to you and also
brings out all the airport bums who are suddenly sporting big signs
grading your landings on a scale of 1 to 10...Nothing higher than a 3
will bring them out.

If the aiming point moves up, it means we are going to land short of
the aiming point and need to shallow the angle of descent, but if we
do that then we are going to slow down and that will cause the angle
of descent to increase which is what we didn't want.

Now if we have an engine we just add a bit of power which lets us
shallow the angle of descent without slowing. Unfortunately the goal
of the exercise is to do this without an engine.

Sooo...we now know that the aiming point moving up in the windshield
means were are not going to do well at all on this particular engine
out landing, but we can be thankful there is an engine up there to
prevent anything more than embarrassment.

But what about that moving down in the windshield and steepening the
angle of descent without gaining too much airspeed?

Flaps are wonderful things. They let you slow down AND increase your
rate of descent. (to-a-point) At least they do on most airplanes we
in this group can afford.

Slips (cross controlled flight do the same thing. Albeit without
adding any lift). Slips can let you lose a lot of altitude in a hurry
without gaining a lot of airspeed.

So, with careful planning, lots of practice, erring if any, on the
high side. Keep the "dirty spot" stationary in the window, and using
energy management you "land on the spot".


Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)

- Andrew

On Sun, 10 Aug 2003 19:04:36 GMT, (Richard
Thomas) wrote:

My instructor has me doing power out simulted emergency spot landings
in prep for my checkride. I've already had my checkride put back once
cause I'm not getting them right often enough. Did some more today but
still not 100%.

Does anyone ahve any tips? He wants me to land on the numbers. I can
sometimes do it 2 or 3 times in a row but next time, I'll be 100 ft
too high or just a little too low

Rich


FWIW, I just spent .9 practicing these and managed 11 decent landings
with two of them just a little long (but still allowing for stopping
before the 1000' markers). No go arounds or coming down short. Amazing
what a night's sleep will do.

Rich

Richard Thomas wrote:

Does anyone ahve any tips? He wants me to land on the numbers. I can
sometimes do it 2 or 3 times in a row but next time, I'll be 100 ft
too high or just a little too low

Don't use a lot of flaps.

George Patterson
They say that nothing's certain except death and taxes. The thing is,
death doesn't get worse every time Congress goes into session.
Will Rogers

On Sun, 10 Aug 2003 20:11:36 -0400, "G.R. Patterson III"
wrote:



Richard Thomas wrote:

Does anyone ahve any tips? He wants me to land on the numbers. I can
sometimes do it 2 or 3 times in a row but next time, I'll be 100 ft
too high or just a little too low

Don't use a lot of flaps.

Take several days off before you do any more. Give your crocodile
brain a chance to catch up with your ape brain.

Don

A previous poster mentioned airspeed, and he's right. Most of the
students I fly with have trouble nailing an airpseed and holding it.
For power-off approaches, use the best glide speed and then make
the approach just a bit high, applying flap as necessary to steepen
the glide to hit the spot. You can also reduce the approach speed a
bit to steepen a glide, but watch that you don't start such a serious
sink rate that you end up short without any flare speed. Reducing
glide speed 5 knots can make a big difference in the glide angle.
Diving at the spot is the wrong thing to do, as it increases airspeed
which will only cause float when you reach the surface.
I once read of the British training their recon pilots in spot
landings during the big war. They buried a 2x6 flush with the grass,
flat side up, and the pilots learned to touch down ON the board, in
that 5 1/2 inches, without bouncing and at a given airspeed. If they
could do it, so can we. We just don't care enough to get good at it.
Or, perhaps, we can't afford to get good at it.

Dan