3D Harrier: Throttle Technique

3D Harrier: Throttle Technique
3D Harrier: Throttle Technique
DAS
PARKFLY
The high alpha “harrier” pass is the corner stone of 3D flying.
A harrier pass consists of flying an airplane at a very high angle
of attack and a very low airspeed. In this position, it can be said
that the plane is flying on the prop instead of on the wing.
Control during a harrier is primarily maintained by propwash over the tail surfaces. Thus, as a 3D pilot,
you must start thinking of throttle as equating to “control”. However, if you tried to maximize control
by maintaining a higher throttle position, the airplane might climb or accelerate. On the other hand, if
you waited until the controls were no longer effective to start adding power, you may not recover control
in time to save the maneuver. Therefore, a 3D pilot smoothly pumps the throttle when flying on the prop
in order to maintain propwash over the tail surfaces without holding the higher throttle positions long
enough to cause the airplane to accelerate.
The objective is to pump the throttle throughout the harrier to maintain the same height, while adjusting
the elevator to maintain a very high angle of attack. At the instant the controls become ineffective or
the plane starts to descend, give the throttle a little extra boost. You will find that you are able to respond
to moments when more control is needed much faster when continually pumping the throttle, than if the
throttle had been stationary.
Throttle
Boost control or climb
Mean average to
maintain same altitude
Effect descent
To maintain the same height during a harrier, the amplitude or range of the throttle movements is
usually between 1/4 and 1/2 throttle with an airplane capable of hovering at half throttle. Note: if you
lose complete control at these very low airspeeds, often the only way to regain control and recover is
to quickly go to full power.
C-89
KPTR: Pump the throttle to maintain control authority without accelerating.
Vary the amplitude or range that you pump the throttle to control altitude.
3D Harrier Pass: Elevator Technique
DAS
The simplest way to enter a harrier is to slow down near stall speed. Then smoothly pull the nose up
to establish a very high angle of attack while simultaneously adding power to maintain the same height.
PARKFLY
Every airplane has a certain fuselage angle or “sweet spot” during the harrier that results in the least
amount of wing rocking. That angle is usually close to 45 degrees, and it usually takes about half
elevator to achieve that angle. You will then find that it takes constant elevator adjustments to maintain that angle due to the fact that airplanes are not designed to fly this way. Note: If you are late with
any of your elevator adjustments, it will take a much larger input to recover, thus increasing the
potential for over-controlling. Therefore, 3D pilots smoothly pump the elevator throughout the harrier
to keep their fingers nimble and ready to instantly respond to the needs of the moment. Inputting a
series of smaller adjustments, rather than waiting to respond with larger adjustments, also reduces the
potential for over-controlling.
45N
Seeking the sweet spot....
Lower nose
Mean average
to maintain 45N
attitude
Raise nose
KPTR: Seek to maintain an approx. 45 degree fuselage angle
during the harrier by smoothly pumping the elevator.
C-90
DAS
PARKFLY
3D Harrier Pass: Rudder and Aileron Applications
Rudder is used throughout the harrier to correct left and right deviations and to steer the airplane.
Coordinated aileron and rudder inputs are used to keep the wings level and prevent adverse yaw.
Airplanes are typically very unstable during high alpha flight, making it very easy to over-control.
Therefore, you must keep your rudder and aileron inputs very small and brief to avoid causing the
wings to rock uncontrollably.
Conventional flying experience teaches us to relax the elevator and lower the nose when the wings start
to rock during a stall. However, one must resist the urge to relax the elevator when the wings start
rocking during a harrier. Maintaining a high angle of attack can actually work to lessen wing rocking
by keeping both wings deeply stalled and therefore having as little aerodynamic influence on the
maneuver as possible. Put another way, when the wings start rocking, sometimes pulling more elevator
will lead to less wing rocking. You can also reduce wing rocking slightly by programming both ailerons
to deflect up 5-10N with up elevator.
C-91
KPTR: Use rudder to keep the fuselage pointed in the same direction, and
coordinate tiny aileron-rudder inputs to keep the wings level during a harrier.
3D Harrier Turns
DAS
Turning while in a harrier attitude consists of steering with the rudder, using the ailerons to keep the
wings level, and pumping the elevator and throttle to maintain the same fuselage angle and altitude.
PARKFLY
As unstable as an airplane is during a harrier, in order to turn without over-controlling you must limit
your rudder inputs to brief nudges every few moments. Note: Turning with rudder alone at this angle
of attack would lower the wing on the inside of the turn. Lowering a wing at such a low airspeed
could cause the airplane to drop sharply! Therefore, you’ll need to apply opposite aileron throughout
the turn to keep the wings level. Once the turn is finished, continue using the rudder to steer, but
switch to coordinating aileron and rudder in the same direction to keep the wings level. Remember, if
the wing on the inside of the turn drops, the plane can fall sharply toward the ground, so be ready
during a harrier to punch the throttle to full to help with the recovery.
Apply opposite aileron (cross-control) throughout the turn to keep the wings level.
Rudder alone!
Side note: If the plane behaves strangely, as if
it was responding to alien control inputs, most
likely the mix percentages you’re using are far
too highCwhich probably explains why odd
things happen during other maneuvers as well.
KPTR: Gently nudge the plane around the turn with rudder
while applying opposite aileron to keep the wings level.
C-92
3D Rolling Harrier Rudder Warmup
The next featured maneuver is the awesome rolling harrier pass.
The first phase of learning a rolling harrier is practicing consecutive
rolls using only the rudder to maintain altitude. The objective during this
exercise is to apply top rudder only during the segments of the rolls when
it is most effective at keeping the nose up, i.e., starting approx 45 degrees
before knife edge, through knife-edge and up to 45 degrees past knife edge.
PARKFLY
There won’t be enough time to try to manage the rudder by watching the
airplane. Instead, each time the wings approach knife-edge, commit to a
steady “in-out” rudder control input. Then quickly reflect on the result and
determine whether you need to change the size or pace of the subsequent
rudder inputs to effect better results.
For example: Start by positioning the throttle to approx. half. Pull the
nose up slightly and start rolling. If you are rolling to the right, smoothly
input top left rudder “in-out” when the wings approach knife-edge. If the
result is a heading change because the rudder input was too slow, i.e., held
in too long, determine to speed up the pace of the subsequent top right
rudder input. Or, if your first rudder input proved too small to prevent a
loss of altitude, increase the size of all subsequent rudder inputs.
Note: The most common rudder mistake during rolls is a weak “opposite”
rudder, i.e., when rolling right, pilots tend to input a deliberate left rudder
input, but the subsequent opposite right rudder inputs tend to be much
smaller. Therefore, determine to input the same amount of rudder in both
directions.
Left
C-93
Each control input during rolls can be
broken down into size and duration:
Duration (elapsed time)
In-out
Size
Rudder input
Maximum
rudder
Start rudder
KNIFE EDGE
DAS
In-out
Right
KPTR: Commit to deliberate “in-out” rudder inputs, triggered by seeing the wings approaching
knife-edge, then quickly reflect on the result and apply what you learned to the next rudder input.
Neutral rudder
3D Rolling Harrier Elevator Technique
Duration (elapsed time)
Size
In-out
Elevator input
Push elevator
INVERTED
Using rudder alone during the rolling harrier warmup may have PARKFLY
only raised the nose up about 20 degrees. During the second phase
of learning a rolling harrier, elevator will be added to help raise the nose
higher. The objective is to continue making the rudder inputs as before
while pulling and pushing the nose up during the upright and inverted
segments of the rolls. Once again, there won’t be enough time to try to
manage the elevator by watching the plane. Instead, each time the wings
approach level, commit to a steady “in-out” elevator input. Then quickly
reflect and apply what you learned to the subsequent elevator inputs.
Start by positioning the throttle to approx. half. Pull the nose up slightly
and start rolling. If you’re rolling right, apply top left rudder when the
wings approach knife-edge. When the plane approaches inverted, push
down elevator (in-out). When the plane approaches knife-edge, input top
right rudder. And when the plane approaches upright, pull up elevator.
Repeat as many times as you can, and control your altitude at this stage
by varying the size of your elevator and rudder inputs.
Maximum
elevator
Neutral elevator
Approaching 45N
Approaching 45N
In-out
Left....
In-out
push....
Approaching 45N
Approaching upright
Approaching inverted
Pull the nose up
and start rolling
DAS
In-out
In-out
right....
pull....
In-out
Left....
KPTR: Start rolling and think “left, push, right, pull (upright), left, push, right, pull (upright), etc., etc..”
C-94
Advanced 3D Rolling Harrier
DAS
Significant control deflections and the high angle of attack during a rolling
harrier create a lot of drag, thus, you will have to start pumping the throttle to
maintain altitude and optimal control: Start rolling with the throttle near half.
Adjust the rudder and elevator to maintain an approx. 30-45 degree fuselage
angle while pumping the throttle to maintain the same height. Note: The best
time to pump up the throttle is when the plane rolls through knife-edge, or
roughly corresponding with each left rudder input, for example.
PARKFLY
Prolong top rudder to
prevent adverse yaw
Rudder input
KNIFE EDGE
Maximum
rudder
Start rudder
Approx.
neutral
rudder
Approaching 45N
Approaching 45N
Approaching inverted
Left....
C-95
There tends to be significant adverse yaw at the start of a rolling harrier.
Here are two ways to initiate a rolling harrier without veering off course:
Option 1. Skip altogether or use very little top rudder through the first knifeedge and let adverse yaw raise the nose through the start of the first roll.
Option 2. If you are agile, briefly coordinate rudder in the same direction as
the aileron to prevent adverse yaw at the start of the roll, then quickly switch
to top rudder when the wings approach knife-edge. Note: The down aileron
will create so much drag that you’ll have to prolong your top rudder inputs
well past knife-edge and up to or slightly past wings level to prevent adverse
yaw. Finally, to stay on heading, make sure that you apply deliberate rudder
inputs in both directions!
push....
Approaching 45N
Approaching upright
right....
pull....
Approaching 45N
Approaching inverted
Left....
push....
Approaching upright
right....
KPTR: Use very little top rudder at the start, and prolong your top rudder inputs up to or slightly past wings level.
pull....
3D High Alpha Rolling Turns
High alpha rolling turns are arguably the most
impressive 3D maneuvers. The version featured
here is an “outside” roller, where the plane rolls
right while turning or circling left. Think of the
mechanics of a high alpha rolling turn as similar
to a rolling harrier pass, except the rudder and
elevator are applied a little earlier to induce a
turn as well as raise the nose.
A left to right “outside” roller starts with the
throttle near half. The nose is pulled up slightly,
then right aileron and left rudder are applied
to simultaneously start rolling and turning.
When the wings near knife-edge, down elevator
is applied to push the nose into the turn. Right
rudder is applied when the plane is inverted,
and then up elevator is applied near knife-edge
to pull the nose into the turn.
Start: Pull up slightly and
simultaneously roll right
while applying left rudder.
Upright
“Left....
push.... right....
pull....
left....
push....
Even tempo....
Upright
Knife edge
In-out
Left....
Inverted
In-out
push....
right...
On high rates, things will happen much too fast to try to base your inputs strictly on watching the wings.
Instead, the objective is to commit to a steady drum-beat of “left, push, right, pull, left, push, right, pull, etc..”
If the tempo is correct, you will be initiating left rudder at the same time the wings roll through level to start
another roll. If your tempo is too fast, the premature inputs will force the plane into a descent. If too slow or
late, the plane will roll without turning.
Altitude, fuselage angle, and rate of turn are controlled by varying the size of your rudder and elevator inputs
and pumping the throttle. For example, if you want to tighten the turn or raise the nose, increase the size of
your pushes and pulls. The best time to pump up the throttle is during a knife-edge segment, or corresponding
to each left rudder input, for example. Things happen fast, so be ready to boost the throttle at the instant the
controls become ineffective or the airplane descends. Note: The most common mistake is weak “opposite”
inputs, i.e, the initial rudder and push tend to be deliberate, but subsequent opposite rudder and pulls tend to
be much smallerCthus, determine to apply deliberate rudder and elevator inputs in both directions!
KPTR: Look to initiate each “left, push, right, pull” sequence as the wings are rolling through upright.
C-96
DAS
PARKFLY
3D Knife-edge
A maneuver that is not difficult, but always seems to impress spectators, is the slow speed
knife-edge pass at low altitude: Start with the throttle near half and roll into knife-edge while
raising the nose up to 45 degrees. Adjust the rudder to maintain that angle and pump the
throttle to hold the same altitude. (Note: While mixes can help make knife-edge flying easier,
due to the ever changing aerodynamic, propeller and wind effects, you’ll still need to constantly
correct roll and pitch deviations.)
Sink = Boost throttle
Adjust the rudder to maintain a 45 degree fuselage angle and pump the throttle to maintain altitude.
Knife-edge Loop
A variation on the knife-edge theme is the knife-edge loop.
First, establish knife-edge flight, then hold in full top rudder
while gradually applying full throttle to execute the knife-edge
loop. To exit, quickly throttle back and/or reduce rudder.
Note: The airplane will most likely try to roll upright during the
last quarter of the loop, therefore, be prepared to input opposite
aileron nearing the bottom of the loop to keep the wings vertical.
Also, if a lot of up elevator is mixed with the rudder, the plane
will tend to pitch toward the canopy as it picks up speed coming
down, thus be prepared to input down elevator to correct.
Opp. aileron
and push?
It’s easy to get confused or unnerved at the bottom of a knifeedge loop, so it’s important to initially practice this stunt high.
C-97
KPTR: Even with mixing, don’t be surprised when you have to keep making corrections to maintain knife edge.
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