Transcript Sport Pilot Training Program

Pre-Solo Training Program
Flight Briefing: Lesson 3
Slow Flight & Stalls
In cooperation with Mid Island Air
Service, Inc. Brookhaven, NY
(Michael Bellenir, CFI)
Lesson 3 Objectives
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During this briefing, you will review normal
and slow flight. You will learn the procedure
for performing intentional stalls including stall
aerodynamics, stall recognition, and stall
recovery procedures.
Upon completion of this briefing, you will
experience flight at various airspeeds, and
practice intentional stall entry and recovery.
Flight Briefing: Lesson 3
Definition
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In automotive parlance, a stall is an unintended
stopping of the engine.
An aerodynamic stall is another matter
altogether, and has nothing at all to do with the
aircraft’s engine. In fact, gliders that have no
engine can stall just the same as airplanes do.
In the context of aircraft, a stall is a maneuver
that causes the wing to no longer develop lift.
Flight Briefing: Lesson 3
Rationale
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You may have heard of accidents that occurred
when the airplane stalled out of control, and
may perceive stalls as an unsafe maneuver.
Some pilots think to avoid such accidents, by
saying “I’ll just never let the airplane stall.”
But, unless the wing eventually stops
developing lift, the plane can never land! So,
think of controlled stall practice as preparation
for learning how to land.
Flight Briefing: Lesson 3
Aerodynamics
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To know how a stall occurs, we must first examine how
a wing generates lift.
The wing’s shape causes air above the upper surface
of the wing to accelerate. This accelerating air
decreases in pressure. The pressure differential
between the upper and lower surfaces of the wing
cause the wing to rise. (Bernoulli’s Principle)
As the wing flies, it also deflects air downward. The
resultant force is such that the air pushes up on the
lower surface of the wing causing the wing to rise.
(Newton’s Third Law)
Flight Briefing: Lesson 3
Aerodynamics-How the wing lifts
Bernoulli’s Principle:
As the velocity of a fluid
increases, its pressure
decreases. The
accelerated air above
the wing exerts less
pressure on the wing
than the un-accelerated
air below it.
Flight Briefing: Lesson 3
Aerodynamics-How the wing lifts
Air flow over the wing
creates downwash, the
pushing of air down
creates a lifting force.
The direct deflection of air
downwards off of the lower surface
of the wing also creates a resulting
lifting force upward.
Flight Briefing: Lesson 3
Angle of Attack
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The larger the angle at which a wing is
presented to airflow, the more lift it generates.
This is because a larger angle increases the
effective curvature of the wing, as well as
increasing the amount of air deflected
downward off of the lower surface of the wing.
This angle is called the “Angle of Attack.”
The definition of angle of attack is: The angle
between the chord line and the relative wind.
Flight Briefing: Lesson 3
Angle of Attack
Flight Briefing: Lesson 3
Lift and Angle of Attack
As angle of attack
increases, the amount of
lift generated by the wing
increases, until the
airplane reaches the
maximum coefficient of lift.
Flight Briefing: Lesson 3
Stalls
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A stall occurs when the wing reaches its critical
angle of attack.
At the critical angle of attack, the wing structure
is presented at such a high angle to the relative
wind that the airflow no longer stays in contact
with the upper surface of the wing.
At the critical angle of attack, airflow separation
from the wing occurs, causing the airflow over
the wing to become turbulent.
Flight Briefing: Lesson 3
Stalling Aerodynamics
Flight Briefing: Lesson 3
Stalls
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When airflow separates from the top of the
wing, the amount of lift the wing produces is
drastically decreased. The result is called an
aerodynamic stall.
To recover from a stall, simply reduce the
angle of attack. This can be done by either
lowering the pitch, or by increasing speed.
To recover the quickest with minimal altitude
loss, lower the nose and add full power.
Flight Briefing: Lesson 3
Stalls
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Remember that an airplane always stalls at the
critical angle of attack. A stall can happen at any
altitude, airspeed, or in any flight attitude.
Ailerons change the position of the trailing edge on
the outboard sections of the wing. Therefore,
changing the position of the ailerons will change
each wing’s angle of attack. This makes it extremely
important to keep the ailerons neutral during a stall,
as different angles of attack on each wing will
aggravate the stall condition.
Flight Briefing: Lesson 3
Stalls
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Aileron deflection in the stall will cause one wing to
have a higher angle of attack than the other, causing
the wings to stall at different times. This will cause a
rolling tendency toward the wing that stalls first.
If aileron pressure is applied away from the dropping
wing (your natural instinct), the aileron on the dropping
wing will deflect downward. This will increase the
angle of attack on that side and deepen the stall; the
dropping wing will continue to drop.
Make sure to keep the ailerons neutral during stalls.
Flight Briefing: Lesson 3
Stalls
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Improper use of rudder can also aggravate a
stall.
If the airplane is not coordinated properly, the
wings will have slightly different relative
airspeeds, and therefore different angles of
attack.
Improper coordination will also cause one
wing to stall before the other, causing it to
drop first.
Flight Briefing: Lesson 3
Stalls
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If one wing does stall before the other, the
airplane will start to roll toward the stalled wing.
To recover, keep the ailerons neutral and use
rudder pressure away from the dropping wing
to prevent any further rolling.
By applying rudder pressure, you will speed up
the dropping wing and slow down the rising
wing. Rudder pressure will help restore the
wings to the same angles of attack and stop
the rolling.
Flight Briefing: Lesson 3
Stalls
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If a stall is entered without aileron input and
with proper coordination, the airplane will not
roll at all. Instead, it will simply pitch down
slightly as the wings lose lift.
Flight Briefing: Lesson 3
Flying into the Stall (Intentional Stalls)
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This airplane is inherently stable and will have gentle
stalling characteristics.
As the airplane slows down, you will notice that the
nose of the airplane will pitch down; this is the
tendency of the airplane to resist going into a stall (it’s
trying to recover before the stall even happens).
If you want the airplane to stall, you’ll have to apply
back pressure on the stick to hold the nose up.
As the airplane approaches the stall, you’ll feel a slight
shaking, or buffeting in the airframe. This is an
indication that the airflow is starting to separate from
the top of the wings, causing turbulence on top of parts
of the wing.
Flight Briefing: Lesson 3
Stall Progression
The stall starts at the wing root near
the trailing edge, and progresses
outward as the stall develops.
When the wing loses enough lift, the
nose will drop. Wings are designed
to stall this way in training aircraft so
that the ailerons will remain
effective as long as possible (but
remember that using ailerons can
aggravate the stall more).
Flight Briefing: Lesson 3
How To Enter a Stall
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To stall, we have to increase the angle of
attack to the critical angle of attack.
Remember that as we slow down, the angle
of attack has to increase to maintain a
constant amount of lift.
We will slow down with the power reduced,
and hold altitude as long as possible. This
will cause the angle of attack to increase.
Flight Briefing: Lesson 3
How To Recover From a Stall
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When the airplane stalls, the nose drops.
To recover from the stall, we simply reduce
the angle of attack.
Increase airspeed (reduce pitch) to decrease
angle of attack, add full power to recover lost
altitude, and climb out at best climb speed.
Try to lose as little altitude as possible (very
easy in this type of airplane)
Return to straight and level flight
Flight Briefing: Lesson 3
Different Types of Stalls
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Remember, the airplane can be stalled at any
airspeed, attitude, configuration, or power
setting.
You’ll practice basic stalls with the flaps at
different settings and at different power levels.
When practicing stalls with power applied,
remember that the engine and propeller create
left turning tendencies, thus requiring the use
of more right rudder.
Flight Briefing: Lesson 3
Why We Do Stalls
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One purpose of this training is to recognize
when the airplane is approaching a stall, so
that you don’t stall accidentally.
Pay close attention to what the airplane feels
like as it approaches the stall. You’ll notice
that the controls become significantly less
effective, that the airplane tries to pitch down,
and that you can feel the aerodynamic buffet
of airflow separation from the wings.
Flight Briefing: Lesson 3
Don’t Be Afraid!
(Easier said than done)
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It’s normal to have some apprehension of stalls (you should
keep some of this fear; unintentional stalls at the wrong time
or handled improperly can cause pilots to lose control!)
Don’t worry. When done properly, there’s really not much
that can go wrong in this type of training.
Generally, the worst thing that can happen is that because
of improper use of the controls, one wing will stall slightly
before the other.
Keep the stick neutral, and control direction in the stall with
rudder.
Your instructor won’t let you get into too much trouble!
Flight Briefing: Lesson 3
Weight and Balance
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Stall speed increases as the weight of the aircraft is
increased. An LSA must meet a 45 KCAS stall speed
limit, flaps up, at its maximum gross weight.
It is very important that the airplane be properly
loaded, with the CG within the acceptable limits, in
order to recover properly from a stall.
To calculate where the CG is, use the information in
the Pilot’s Operating Handbook (POH) or the Airplane
Operating Instructions (AOI). This will be covered in
detail in a later lesson.
Flight Briefing: Lesson 3
Review Questions
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Define “angle of attack.”
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As a fluid’s velocity increases, pressure:
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A stall occurs when the wing exceeds its:
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To recover from a stall with minimal altitude loss:
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Rolling in a stall should be controlled with:
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What happens to stall speed as the aircraft’s weight increases?
Write down your answers before
continuing to next slide
Flight Briefing: Lesson 3
Review Answers
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Define “angle of attack.”
– The angle between the chord line and the relative wind
As a fluid’s velocity increases, pressure:
– Decreases according to Bernoulli’s Principle
A stall occurs when the wing exceeds its:
– Critical angle of attack
To recover from a stall with minimal altitude loss:
– Lower the nose, steer with your feet, and add full power
Rolling in a stall should be controlled with:
– Rudder input and neutral ailerons
What happens to stall speed as the aircraft’s weight increases?
– It goes up.
Review any missed questions before
continuing to today’s flight.
Flight Briefing: Lesson 3
On Today’s Flight
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We’ll practice flying the airplane at different
speeds, including slow flight.
We’ll approach stalls in different
configurations (flaps up/down; power on/off).
We’ll practice recognizing the beginning of a
stall, and recovering to normal flight.
Flight Briefing: Lesson 3
In the Traffic Pattern
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Pay attention to how the airplane feels on
approach to landing, don’t let it stall before
getting to the ground!
Thanks to Mid Island Air Service, Inc.
Brookhaven, NY (Michael Bellenir, CFI)
Flight Briefing: Lesson 3