Downwind Landings

What is your threshold for landing (or departing) downwind? Will you land
knowing you have a 5 knot tailwind? 10 knots? At what point will you
"flip" the pattern to takeoff or land into the wind?

Me? I'm a 5 knot kind of guy (but I fly a taildragger)...

I landed at 3 different fields today where the established pattern resulted
in a landing with a quartering 7 knot (or more) tailwind, with some mild
gusts thrown in for good measure.

At the first field, I was careless enough to assume the traffic was using
the runway facing the wind. The downwind landing came as a bit of a
surprise, then I looked at the wind sock - oops...

At the other two fields, I announced my position and intentions and waited
(360's on the downwind) until I could land into the wind without interfering
with aircraft already in the pattern.

And what is the correct radio phraseology to say: "Fellas, it is time to
reverse the pattern - you're taking off and landing downwind.." ?

On Sep 22, 11:01 pm, "Kyle Boatright" wrote:
What is your threshold for landing (or departing) downwind? Will you land
knowing you have a 5 knot tailwind? 10 knots? At what point will you
"flip" the pattern to takeoff or land into the wind?

Me? I'm a 5 knot kind of guy (but I fly a taildragger)...

I landed at 3 different fields today where the established pattern resulted
in a landing with a quartering 7 knot (or more) tailwind, with some mild
gusts thrown in for good measure.

At the first field, I was careless enough to assume the traffic was using
the runway facing the wind. The downwind landing came as a bit of a
surprise, then I looked at the wind sock - oops...

At the other two fields, I announced my position and intentions and waited
(360's on the downwind) until I could land into the wind without interfering
with aircraft already in the pattern.

And what is the correct radio phraseology to say: "Fellas, it is time to
reverse the pattern - you're taking off and landing downwind.." ?


One can easily do the math to get a ballpark figure. Landing distance
increases as the square of the approach ground speed. If the approach
speed is 60, and you have a 10 knot wind, your landing distance will
increase by 35%.For 20 knots it increases by 75%. For 30 knots, it
more than doubles. A 5 knot limit for short runways makes sense; 10
knots if you really know what you are doing. I would not atempt
anything higher unless it is a super long runway.

"Kyle Boatright" wrote in
:

What is your threshold for landing (or departing) downwind? Will you
land knowing you have a 5 knot tailwind? 10 knots? At what point will
you "flip" the pattern to takeoff or land into the wind?

It rather depends on the runway...

My threshold on a 3000' runway is smaller than my threshold on a 6000'
runway.

Kyle Boatright wrote:

And what is the correct radio phraseology to say: "Fellas, it is
time to reverse the pattern - you're taking off and landing
downwind.." ?

This is the part I'm interested in hearing comments on.

--
Oz Lander.
Straight and Level Forum.
http://z7.invisionfree.com/Straight_...ex.php?act=idx

The pilot in command is responsible for the safety of the flight. If I
arrive at a non towered field and notice the pattern doesn't reflect
the current winds I observe who was there first and in what order, I
then make a radio call announcing my intentions of reversing the
pattern, I let those before me to do whatever please and when its my
turn I fly the pattern that is best for my safety. I dread the thought
of sitting at an FAA/NTSB inquiry and stating the " yeah they were
landing downwind so I did it too" excuse....... Kinda likesaying" all
the others jumped off the cliff so I did it too".. :)..

Ben
N801BH
www.haaspowerair.com


On Sep 23, 5:26 am, "Oz Lander" wrote:
Kyle Boatright wrote:
And what is the correct radio phraseology to say: "Fellas, it is
time to reverse the pattern - you're taking off and landing
downwind.." ?

This is the part I'm interested in hearing comments on.

--
Oz Lander.
Straight and Level Forum.http://z7.invisionfree.com/Straight_...ex.php?act=idx

On Sat, 22 Sep 2007 23:01:54 -0400, "Kyle Boatright"
wrote in
:


What is your threshold for landing (or departing) downwind?

That is dependent on the length of the runway(s), its gradient/slope,
surface, and the performance of the particular aircraft.

And what is the correct radio phraseology to say: "Fellas, it is time to
reverse the pattern - you're taking off and landing downwind.." ?

The correct radio phraseology for operating at an uncontrolled field
is, Podunk airport traffic, Cessna 123 entering left downwind for
runway 18, Podunk traffic. Nothing changes. You self-announce your
intentions, keep your eyes open for conflicting traffic, and give
right of way in accordance with CFR 14 § 91.113 Right-of-way rules:
http://ecfr.gpoaccess.gov/cgi/t/text... .1.3.10.2.4.7

The tricky part of downwind landings is the necessity to extend your
traffic pattern's Downwind Leg (actually against the wind in the case
of a downwind landing) WELL BEYOND (perhaps double or more) what you
are accustomed to in a normal into-the-wind landing. If you fail to
do this, you will overshoot.

There's also the issue of whether to takeoff into or with the wind on
runways that aren't level....
http://groups.google.com/group/rec.a...5?dmode=source
An average force derivation gives the following formula for
the "breakeven headwind," i.e., the headwind of such speed that
it's a wash whether you take off into the headwind up hill or
take off with that tailwind down hill:

Vhw,breakeven = Slope in degrees * distance to lift off with
no wind, no slope / (5*speed at lift off in KTAS)

where Vhw,breakeven is in knots and the distance to lift off
is in feet.

With the same "constant" average force assumption the same
should be true for landing, making obvious changes. In actual fact
the above formula is a slight "simplification" of a somewhat more
complicated one.

The thing that messes up a lot of people is that you can have
three airplanes ready to take off on the same strip under the same
conditions and one of them (higher powered) is best off to go
uphill into the wind, one of them best off downhill with the wind,
and with the third it makes no difference (unless there are other
considerations like terrain clearance, etc.)

Hope this helps more than it confuses.
John T. Lowry

The tricky part of downwind landings is the necessity to extend your
traffic pattern's Downwind Leg (actually against the wind in the case
of a downwind landing) WELL BEYOND (perhaps double or more) what you
are accustomed to in a normal into-the-wind landing. If you fail to
do this, you will overshoot.


You are getting close to one of the answers.

Yes with a downwind landing you much more likely to overshoot. Since
you may overshoot you are much more likely need to Go Around. On the
Go around two more things happen. One, your climb out will climb out
at a much lower angle which may make it difficult or impossible to
clear obstacles. 2nd you will be close to the ground with a higher
than normal ground speed. The illusion of speed when combined with
approaching obstacles will make you want to climb a slower than normal
airspeed setting you up for a perfect Stall/Spin scenerio.

In fact I know of several Stall spins that have occurred exactly this
way.

One of my favorite demostrations is to simulate a power failure on a
windy day (and no one else in the pattern) when the only runway option
is the downwind runway. Once the student shown me they have they have
the runway made or they overshoot, (as they often do) I request a go
around so they can see how poor the climb angle really is when
departing downwind. With a 15 to 20kt tailwind in a C-150 or Tomahawk
this climbout can be impressively low.

Brian
CFIIG/ASEL

On Sun, 23 Sep 2007 19:37:38 -0700, Brian wrote
in . com:


The tricky part of downwind landings is the necessity to extend your
traffic pattern's Downwind Leg (actually against the wind in the case
of a downwind landing) WELL BEYOND (perhaps double or more) what you
are accustomed to in a normal into-the-wind landing. If you fail to
do this, you will overshoot.


You are getting close to one of the answers.

The answer to which question?

Yes with a downwind landing you [are] much more likely to overshoot.

Right. But I can't emphasize too much the necessity to extend the
"Downwind Leg" to WELL beyond the point where the runway threshold is
at a 45 degree angle to the aircraft's position on the Downwind Leg
(as would be normal for an into-the-wind landing approach), so that
there is enough time to descend on final approach without the wind
blowing the aircraft past the threshold while it is still too high to
touch down.

What do you teach as a rule-of-thumb to determine the point to turn
from Downwind Leg to Base Leg?

Since
you may overshoot you are much more likely need to Go Around. On the
Go around two more things happen. One, your climb out will climb out
at a much lower angle which may make it difficult or impossible to
clear obstacles.

Right. While the approach descent-rate can be increased by employing
a forward slip to increase the angle, unfortunately, there is no
reciprocal method available to increase the climb angle.

2nd you will be close to the ground with a higher
than normal ground speed. The illusion of speed when combined with
approaching obstacles will make you want to climb a[t] slower than normal
airspeed[,] setting you up for a perfect Stall/Spin scenerio.

Good point.

Fortunately, I haven't experienced a downwind go-around into rising
terrain, but wouldn't the orographic lifting of the wind against the
terrain produce some updraft (or vertical component) to assist in
increasing the rate of climb? Or is that just wishful thinking?

In fact I know of several Stall spins that have occurred exactly this
way.

The illusion is so strong, it's easy to understand how that might
happen if the pilot fails to monitor the airspeed indicator to
maintain Vx speed on climb-out.

One of my favorite demostrations is to simulate a power failure on a
windy day (and no one else in the pattern) when the only runway option
is the downwind runway. Once the student [has] shown me they have they have[sic]
the runway made or they overshoot, (as they often do) I request a go
around so they can see how poor the climb angle really is when
departing downwind. With a 15 to 20kt tailwind in a C-150 or Tomahawk
this climbout can be impressively low.

Brian
CFIIG/ASEL

I can see how that would be important.

On Sep 22, 8:01 pm, "Kyle Boatright" wrote:
What is your threshold for landing (or departing) downwind? Will you land
knowing you have a 5 knot tailwind? 10 knots? At what point will you
"flip" the pattern to takeoff or land into the wind?

Me? I'm a 5 knot kind of guy (but I fly a taildragger)...

I landed at 3 different fields today where the established pattern resulted
in a landing with a quartering 7 knot (or more) tailwind, with some mild
gusts thrown in for good measure.

Part of instrument training is to ensure students can land correctly
with a stiff tailwind (given a proper length runway). Instrument
approaches don't always line up with the wind.

-Robert, CFII

"Kyle Boatright"
What is your threshold for landing (or departing) downwind?

Runway length.
Jim