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davestapa
Joined: 13 Mar 2007
Posts: 30
Location: Woodstock, GA
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 Posted: Fri Jan 02, 2009 7:59 am Post subject: Ground Loop Instruction |
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The following humorous article on Ground loops is in EAA Chapter 105's
January newsletter. Below is text or go to:
http://www.eaa.org/ paste in browser window and click on newsletter Jan
09
David Estapa
Woodstock, GA
N97DE S5TD 912ULS
How To Groundloop Your Taildragger:
Judging by how frequently it is performed, the Ground-
loop is indeed a popular maneuver. The Groundloop is
an extreme low-level figure that is highly acrobatic in
nature, which may be executed in many exciting variations.
It is customarily performed as the last figure in a
sequence, but I have seen the Groundloop attempted as a
preliminary or warm-up maneuver.
It is rarely scored however, because it is most often performed
out of the Judges' line-of-sight. Also, the Ground-
loop is categorized as a surprise maneuver, and therefore
nobody is really prepared when it is executed. In fact,
the figure is not considered genuine unless Judges, spectators
and the pilot-in-command are all surprised! The
many interesting and dynamic variations do not have a
Degree of Difficulty or "K" attached, but rather are rated
on the International HC* scale. (*Holy Cow) and logged
under "Oops".
HISTORICAL PERSPECTIVE
The Groundloop is one of the earliest recorded aerobatic
figures. It was performed on virtually all of the taildraggers
dating back to Aviation's infancy. The maneuver
really came into its own during the Golden Era of the
Groundloop which was when the cross-wind landing
was invented. Previous to this, circular landing fields
were the norm and the pilot simply eye-balled the windsock,
and landed into wind. However, it was soon discovered
that a short, straight landing strip could be
plowed out, and now there would be lots of room for
hangars, clubhouse, and an expansive cocktail lounge.
Once everyone saw how much fun this new land-use
concept generated, it was adopted internationally. The
daily Groundloop displays were an instant hit, and
helped cast the new idea in tarmac.
ANALYSIS
Most Groundloops are weathercocking related phenomena.
This means that at least one main wheel must be
touching the earth, and a wind is blowing. Traditionally,
the maneuver is started in a cross-wind; during the landing
roll-out the tail is allowed to be blown down-wind.
At this point there are a variety of options that can be
exercised depending on your inputs, and the maneuver
can take off in almost any direction, and finish in a variety
of attitudes. Groundloops that occur under calm conditions
are more rare, and require vigorous control inputs,
to get them started in contrast to crosswinds where
you do nothing. Sometimes you really have to work at it
to get a decent one.
Groundloops can be generated anywhere from 5MPH to
flying speed. When executed at high speed, the figure
covers more territory and generally spawns the most
interesting variations.
High-wing taildraggers probably Ground loop the best
because the upwind wing is more exposed to the breeze.
The high-wing has less dihedral and also enjoys a longer
arm to really accelerate things once the maneuver starts.
If the airplane is designed with the wheels forming a
small triangle (short-coupled or narrow gear), and in the
hands of the right pilot, this could be a Groundlooping
champion.
ESSENTIAL BACKGROUND KNOWLEDGE
Avoid the study of the following subjects:
a) Cross-wind Landings and Take-offs.
b) Ground-Handling in winds.
Avoid seeking instruction on these subjects, for it will
greatly reduce your chances of producing a truly World-
Class Groundloop. Also, you might want to have a good
line ready in case someone raises one of these subjects in
conversation: "Cross-wind Landings, heck, wasn't that
about lesson 5 on your Private License? I'm way beyond
that.
PREPARATION
To be successful, we must prepare both pilot and aircraft.
PILOT
To perform good Groundloops, the best preparation is
no preparation.
AIRCRAFT
The aircraft can be prepared in a variety of ways to ensure
consistently good Groundloops. First of all, the
main wheels should be shimmed to a toe-in condition. If
the wheels are adjusted to track straight ahead or are
shimmed slightly toe-out, the tracking will be too stable
to assist your attempts at Groundlooping. Keep the tire
pressures different from one another. If you know the
direction of the cross-wind, reduce the pressure on the
up-wind tire before going flying. And remember, it isn't
necessary to change the tires until you can see the second
ply of fabric showing; a blow-out can be the start of a
dazzling Groundloop.
Avoid the hassle of taking off those trouble some wheel-
pants by putting a drop of Loc-tite on the screws. Now
you have a good excuse not to inspect the brakes. So,
when the pads get thin and the brake fails on one side or
the caliper locks up a rusted disc, you will enjoy a splendid
Groundloop.
At the back end, you can start by loosening the fitting
that holds the tail-wheel spring to the fuselage. Just back
the nuts off a few turns. Also back off the nut that attaches
the tail-wheel casting to the spring. Now, slack
off the steering springs a couple of links so the chains
sag. And while you're at it, cut off that lock wire that
some conscientious Engineer installed in case the chains
break. From time to time they break on landing and
produce a thrilling, and rakish Cramer-like lurch. Fantastic!
These simple mods will produce a delightfully loose
rear-end that feels like it's on ball-bearings.
The little tail-wheel is best left alone; over time it becomes
worn into an interesting cone-shape by the effects
of slipstream, P-factor and gyroscopic effect. These left-
turning forces create more wear on the starboard side of
the tire, and soon you have a beautifully unstable little
demon back there to really help you out.
Install the push-to-talk switch in a remote area of the
cockpit. When the tower talks to you on the roll-out, you
can look down into the cockpit to locate the button, and
when you look up, you may be treated to the wonderful
green-and-blue kaleidoscope of rotation about the vertical
axis.
TECHNIQUE (HOW-TO)
Once the pilot and aircraft are prepared, it's a little like
shooting fish in a barrel; there's really nothing to it.
There are several things you can do to get the Ground-
loop going, but really the best thing to do is nothing. Just
let it happen. If you are landing or fast-taxiing in a cross-
EAA Chapter 105 January 2009
wind and you want a Groundloop... you guessed it- do
nothing.
Taxi with abandon. As a pilot, you are a free-spirited
individual, and this can be best displayed by a carefree
jaunt down the taxiway. Just let go of the stick and use
the hands-free time to organize your maps and sequence
cards. If the tail-wheel comes off the ground, you're going
a little fast. Maybe you'll want to use the time to put
on your seatbelt, polish the inside of the canopy, re-tie
your shoelaces or perhaps light up a smoke. Taildraggers
have the right-of-way, so you won't have to stop
suddenly.
When cleared for take-off, start bringing the power up as
you swing out on to the runway. Of course you'll want
to shove the stick forward quickly to get that tail up (you
can't get it up too soon). If the plane will fly at 50, hold it
on until 65. This technique spreads out the landing gear
and brushes off some rubber, but everybody does it and
it looks cool. If you get rolling quickly, any cross-wind
won't matter. Now rotate as you would a 767. Haul
straight back and blaze into the blue. The right turn and
stall that follows will be sensational.
On the approach, keep it low and fast. If the airplane
lands at 50, cross the fence at 100. It's best not to have a
planned touchdown point because that can interfere
with the free-spirited nature of the flying event. Start
fanning the rudders through 500 feet, and keep it going
until you've cleared the runway. The fanning technique
is to confuse the airplane and let it know who's boss. Get
the plane down to the runway as soon as possible, and
force it to land with plenty of forward stick. The fast-
landing method is good for all weather conditions, especially
quartering tail-winds. Once the plane is firmly on
the ground, let go of the stick, but keep fanning the rudder
to cool the tail-wheel assembly. Taxi in as you taxied
out except don’t touch the stick.
VARIATIONS
1. 45-Degree Overland Express.
This one is best done at about 40 MPH. The airplane is
allowed to weathercock slightly, the upwind wing and
wheel are allowed to rise about 3O degrees and the plane
swings into the wind. At 45 degrees off the runway
heading, sharp downwind brake, full aft stick and aileron
into wind are added to stop the Groundloop. The
plane is now headed off overland. This is useful for taking
a short-cut to the washrooms after a long flight.
2. 90-Degree Quick Left Turn with Prop Curl.
With a left crosswind, use the same technique as above,
except at about 20 MPH. When you stomp on the downwind
brake, also shove the stick forward. Even though
you are traveling slower, the gyroscopic effect of shoving
the stick forward will give you that extra 45 degrees of
rotation. The tail will rise briskly. As soon as the prop
touches the runway, pull hard back on the stick and apply
both brakes. This was how the original Q-Tip Propeller
was invented. If you've done it just right, you'll
probably have a much more efficient prop.
The Prop Curl can also be done straight ahead. Taxi at
about 10 MPH while tucking in your shirt or cleaning
your sunglasses. Keep your hands off the stick and slam
on the brakes. Voila! Also try this while maneuvering the
tail-wheel over an obstacle. For a more dramatic Curl,
hold the stick forward and add a burst of power. You
don’t even need to be moving. Just keep your hands off
the stick and your eyes inside the cockpit while doing
your run-up.
3. Pitts Special Twin Arcs.
Start the Groundloop from the roll-out at about 25 MPH.
Remove all cross-wind inputs and allow the airplane to
weathercock. Move the stick forward to at least neutral
to lighten the tail-wheel and reduce its directional control.
The little biplane will rise upon the downwind
wheel and begin a concise pirouette.
The downwind wing-tip will hit the runway and begin
scribing an arc of red butyrate, Dacron and plywood.
Without hesitation slam in full upwind aileron, as if to
attempt to lift the lower wing. The downwind aileron
will shoot down and describe a beautiful red arc parallel
to that made by the wing-tip. Pull the stick full back,
push full downwind brake with full rudder and a burst
of power to erect the plane. These little red arcs are very
artistic and will attract a good crowd in the evening
following the days flying.
4. 180-Degree Pirouette with back-track
This one is best attempted in a light high-wing with narrow
bungee landing gear, a Cub will do. The maneuver
works best in a quartering tail-wind. This figure looks
difficult, but is really pretty simple. It works best if the
pilot is dyslectic.
Get the weather-cocking started in the usual manner.
Move aileron out-of-wind and push the stick forward to
get weight off the tail. 20 MPH is fine. As the up-wind
wing rises, the center of gravity swings as a pendulum
toward the lower wing. About the time the down-going
wing smacks the runway, the center of gravity will have
swung to the outside of the downwind wheel. Apply
this brake hard. Now it's as if you had two upwind
wheels because the center of gravity has migrated outside
via centrifugal force. So now it wouldn't matter
which brake you applied, the effect would be to increase
the rotation of the Groundloop.
As you come around into the wind the wing-tip lifts off
the tarmac, the brake completed a full 180-degree turn.
You are now rolling backwards down the runway. Release
the brakes and practice sailing like a Seaplane.
5. Groundloop with Bunt.
This is certainly one of the more dramatic figures in the
Groundloop family. You'll want to be traveling a little
faster to get this one. Say 35 MPH. The figure should
start slowly then get faster and tighter as rotation sets in.
A dry runway is necessary, and a quartering tail-wind
from the left is best. Once rotation starts, shove in full
down-wind stick and full forward elevator. This will
really tighten up the rotation. Now add full brakes and
full power. The tail will shoot upwards and the airplane
will do a kind of shoulder roll right on to its back. This is
really low-level inverted parking and you should ensure
that your belts are very tight. This figure should be reserved
for the last flight of the day.
CONCLUSION
The Groundloop has been around for almost a century
and I'm sure it will be with us forever. To keep it alive,
all we have to do is be a little complacent, a little cocksure
and in a little hurry. Most important, one needs a
thorough understanding of flying an Ercoupe’. Sounds
pretty easy to me.
____________________________________________________________
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_________________
C. David Estapa
Woodstock, GA
S5TD N97DE |
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davestapa
Joined: 13 Mar 2007
Posts: 30
Location: Woodstock, GA
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Paul A. Franz, P.E.
Joined: 02 Dec 2008
Posts: 280
Location: Bellevue WA
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| Posted: Fri Jan 02, 2009 9:40 am Post subject: Ground Loop Instruction |
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On Fri, January 2, 2009 7:57 am, C. David Estapa wrote:
clip clip
| Quote: | CONCLUSION
The Groundloop has been around for almost a century
and I'm sure it will be with us forever. To keep it alive,
all we have to do is be a little complacent, a little cocksure
and in a little hurry. Most important, one needs a
thorough understanding of flying an Ercoupe’. Sounds
pretty easy to me.
|
Excellent post Mr. Estapa!
I really found this one informative. Didn't some models of the Ercoupe’ completely
lack rudder controls?
--
Paul A. Franz
Registration/Aircraft - N14UW/Merlin GT
Engine/Prop - Rotax 914/NSI CAP
Bellevue WA
425.241.1618 Cell
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_________________
Paul A. Franz, P.E.
Registration/Aircraft - N14UW/Merlin GT
Engine/Prop - Rotax 914/NSI CAP
Bellevue WA
425.241.1618 Cell
425.440.9505 Office |
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davestapa
Joined: 13 Mar 2007
Posts: 30
Location: Woodstock, GA
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| Posted: Fri Jan 02, 2009 12:20 pm Post subject: Ground Loop Instruction |
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Paul, I know the first models did not have rudder pedals. My brother
owned one. Don't know about the last ones produced. I know many have been
converted to include rudder pedals.
David
Do not archive
On Fri, 2 Jan 2009 09:39:27 -0800 (PST) "Paul Franz - Merlin GT"
<paul(at)eucleides.com> writes:
| Quote: |
<paul(at)eucleides.com>
On Fri, January 2, 2009 7:57 am, C. David Estapa wrote:
>
<davestapa(at)juno.com>
|
| Quote: | I really found this one informative. Didn't some models of the
Ercoupe’ completely
lack rudder controls?
--
Paul A. Franz
Registration/Aircraft - N14UW/Merlin GT
Engine/Prop - Rotax 914/NSI CAP
Bellevue WA
425.241.1618 Cell
____________________________________________________________
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_________________
C. David Estapa
Woodstock, GA
S5TD N97DE |
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