Page a8
Stall Origins
and Performance
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…Slow flight; ...Aircraft
stall factors; ...Desirable Stalls;
...Trim in the stall; ...Wings
in the Stall; ...Rudder in the stall;
...First stall instruction (Instructor);
...Stall Lesson; ...PTS
Stalls; ...Objectives of stall instruction;
...Clearing turns;
...Where to practice; ...Not
so Real Stalls; ...Stall exercises (Instructor);
...Stall avoidance Practice at slow airspeeds;
...Stall Recognition; ...Natural
Stall Warning; ...Generic stall Recovery;
...Secondary Stall ; ...Stalls
Down Low;
...Deep stall; ...Stall
Recoveries; ...Stall Proficiency (Instructor);
...Power-Off Stall; ...Power-on
stall (Partial power); ...Departure Stall;
...Approach Stall; ...Accelerated
Stall (Instructor); ...Accelerated
Stall Situations; …Cross-control Turn
Base to Final Stall; ....Unrecoverable stall;
...Trimmed go-around stall; ...Engine
Failure at Altitude; ...Takeoff Engine Failure
Stall; ...Engine Failure on Final Stall;
...Landing flare stall; ...Premature
flap retraction Stall; ...Go-around in
a Right Crosswind Stall; ...Slow Flight
in Pattern Stall; ...Short Field Takeoff
Stall; …Falling Leaf Stall; ...More on stalls; ...Stall
Review; ...Stalls in brief;
Slow Flight
Most any one can skate or ride a bike fast. It is at slow
speeds that true skill and control can be demonstrated. The same
is true about flying. When I first sought to be a flight instructor
an old time CFI took me out on his nickel and told me that we
would explore the outer limits of the aircraft's controllability.
Under his guidance I learned to fly. Prior to that I only had
control.
We would fly without flaps on heading and altitude with power as required to maintain level flight. We would fly slow, slower, and slowest. We flew well below the 10-knot margin given by the stall warner. A student is not expected to do this in any configuration. The PTS standards are to fly at Vs1 without flaps, with flaps, with partial flaps on heading and at altitude plus ten and minus five knots; within 100 feet of altitude and 10 degrees of heading. Then they add turns, climbs and descents with specified angles of bank.
Most any Vs1 slow flight can be performed in a ten degree bank. To the left just relax the rudder. To the right add rudder and opposite aileron. If you go beyond the 10-degrees you look forward to a cross-control stall. By adding some power you can make a 30 degree bank. Now the stall spin possibilities are increased. Time for a distraction to be introduced. Slow flight near the stall is called minimum controllable. The power of the rudder in controlling the stall and yaw is best demonstrated in this exercise. The rudder application is proven when the stall break is straight ahead without any wing drop. Any application of aileron will be counter productive by further stalling the wing and causing a more abrupt wing drop.
Aircraft
stall factors
Wilbur Wright used the word 'stall' in 1904 to describe how
in a turn Orville allowed the aircraft to pitch up too much and
stall. The potential of an aircraft to stall or spin is in its
design. A pilot's ability to detect and react to this potential
is a criteria of flying skill. When an airplane is flown at an
angle that exceeds the critical angle of attack, the airplane
will stall. In deliberate training stalls we decrease airspeed
and avoid the abusive control inputs that cause unusual attitude
stalls. Low speed is not the cause of the stall; the cause is
the angle of attack.
The pilot has control of the elevator. Pressures on the elevator determine if the wing will develop an angle of attack sufficient to stall. When the angular difference between where an airplane is pointed and the way it is going exceeds about 11 degrees to the wing's chord line a stall occurs. This is called the critical angle of attack. Exceeding the critical angle of attack of the wing with elevator inputs will cause the airflow to break from the upper wing surface. This break in air flow reduces the coefficient of lift, increases the coefficient of drag and transmits to the pilot a series of aerodynamic, mechanical and physiological cues.
Stall warners give a ten-knot warning of impending stalls as normally performed. The accidental inadvertent stalls that I have encountered occurred simultaneously with the sound of the horn. The same plane could stall at 40 knots when weighing 1600 pounds an at 30 knots weighing 1300 pounds. Of course, weight is always a factor in that a 20% weight increase will give 10% higher stall speeds. while a corresponding 20% reduction in weight will give a 10% lower stall speed. . The real objective is not so much performance as recognition by sight, sound, and feel.
The critical constant in stall speeds is weight. Book figures are based on gross weights. This provides most flight operations with a built in safety margin. This safety margin may be over-ridden by knowing that your actual weight is a certain percentage less than the gross. You can reduce your approach speed by a percentage that is half the percentage of lower weight. Some aircraft have critical approach airspeeds that do not follow the rule because of control and ability to go-around considerations.
For those who may be a little weak in doing the figuring, make
a proportion like this:
Difference between actual and gross = Percentage of gross
Gross weight 100
Cross multiply difference x 100 and divide product by gross weight
to get percentage of gross.
Take half of the percentage of gross as the percentage to reduce
your approach speed.
Example: 1600# C-150. Take out 200# instructor and figure reduction
of approach speed.
200# = % 200 x 100 = 12.5% Taking half leaves 6%
1600# 100 1600
6% of a 60 knot approach speed is about three knots. 60 - 3
= 57-knots
This example can be used as a basis for interpolation only for
the C-150.
When stalling speeds are determined for aircraft they are set at the most critical CG condition. Thus the speeds are set in the manual for "indicated" speeds with a forward CG position. This gives the highest stalling speed. Since training aircraft are seldom flown at the most forward CG the usual stall speed will be lower. This accounts for the book differences you should have noted. The way an aircraft behaves entering, during, and recovering from a stall is used to determine its stall characteristic. These characteristics are determined at the aft CG when stall speed is at its slowest.
Desirable
stalls
A "stall" occurs as a result of one of two events:
1. The wings can not support the load of the weight being carried.
2. The horizontal tail can not provide the pitching authority
needed to support the wing loading(tail stall)
The normal stall is when the wing stalls. When the tail stalls it is called a tail-stall. The tail stalls are very abrupt and the nose pitches down near the vertical. This stall increases the effective AOA of the tail. The stall can tuck the aircraft inverted with negative G-forces. The most desirable stall occurs when the wing root stalls first and moves outward to the wing tip. This desirable stall can be built into the wing by twisting the wing, adding slots to the wing tip, putting stall/spoiler strips to the leading edge of the root.
Every aircraft type and even aircraft of the same type will have stalling characteristics affected by weight distribution, wing loading, its critical angle of attack, control movement, configuration, and power. Higher powered aircraft can often be flown out of the stall by the addition of power. The purpose of such a stall recovery is to minimize any loss of altitude. This is a more aggressive stall recovery than the usual lower the nose technique.
The noise you first hear is the vibration of this erratic air hitting the tail surfaces. Aircraft type and even aircraft of the same type will have stalling characteristics affected by weight distribution, wing loading, its critical angle of attack, control movement, configuration, and power. Higher powered aircraft can often be flown out of the stall by the addition of power. The purpose of such a stall recovery is to minimize any loss of altitude. This is a more aggressive stall recovery than the usual lower the nose technique.
Stall characteristics are often 'discovered' after the aircraft has gone into production. The manufacturer-government license agreement requires that all production aircraft adhere to original construction so some modifications are incorporated. The most expensive fix is construction of a leading edge slot. A 'cuff' or drooped leading edge may be used, a series of protrusions on the upper wing surface may be used to direct air flow even to the extent of being full chord 'fences' to prevent spanwise flow. The addition of a small triangular strip on the leading edge of the wing can cause the airflow over the surface to break and burble sooner than otherwise. This, rather common, method, is the least expensive fix of all. The design should be such that the stall occurs progressively from root to tip. The tips have a lower angle of attack than the root. Recovery of a stall begins at the tips and proceeds to the root. This design allow ailerons to remain effective for longer periods.
Government stall tests are not made with slips or skids. While the old saw of slips being good and skids being bad may be true, it is only partially true. A stall that occurs in a slip or skid may occur at a higher speed than expected. Any deflection of the ailerons will increase the stall onset. Any aggravation of the stall by increasing the back pressure may result in sudden attitude changes due to turning and unequal wing speed. The attitudes resulting may be a combining of yaw, roll, and spin entry.
As the stall approaches the ailerons become ineffective first.
Elevators follow when the airflow from the wing becomes turbulent.
This turbulence is your natural stall warning. As the stall approaches,
students tend to under react with the required rudder pressure
to keep the wing speeds balanced. A more aggressive application
of students in the beginning is more desirable.
When the stall occurs that will kill you it won't be at 2500 feet
AGL….It won't be done intentionally.and you won't expect
it. It'll happen on short final, right after takeoff or on the
go around from that short strip you were looking at. You'll be
distracted (which is why you've allowed this to develop) and will
need to make an immediate and proper corrective action. The only
way to develop that reflex is with practice but not a low altitudes.
Trim in
the stall
Trim is not normally used to relieve pressure during the actual
performance of training stalls. However the new PTS (Practical
Test Standards) now calls for stalls to be made in a trimmed condition
with distractions. A no power recovery should occasionally be
called for. Any flaps more than 20 degrees should be taken off
at once. Less than 20 degrees of flaps should come off when climb
speed is attained. The apparent attitude of stalled aircraft with
flaps is quite flat. Holding pitch attitude of the aircraft correctly
while removing flaps is a must. No loss of altitude should occur
while removing flaps. A secondary stall during recovery is indicative
of failure.
Wings in
the Stall
The manner in which the stall cues are transmitted is dependent
upon wing shape, twist (washin/washout) and installed features
such as strips, slots or flaps. Together these cues provide the
pilot a warning of the stall onset. With washout the wing is mounted
in a jig and twisted to lower the angle of incidence at the wing
tip. Impact air on the bottom of the wing still provides some
residual lift but not enough to keep the airplane flying.
Ailerons in the stall will only aggravate it. Ailerons change
to chord line of the wing to create lift and movement along the
roll axis. When the aileron is stalled their movement causes roll
that is contrary to what you either want or expect. Once the recovery
is initiated with forward yoke and rudder the use of ailerons
may or may not be helpful depending on the aircraft. This difference
is aileron effectiveness is related to the washin/washout or twist
given to the wing progressively toward the tips. Tips stall last
and recover first in most modern aircraft due to a decreased angle
of incidence. Aircraft design determines the aircraft stall characteristics.
]
A stall progression, if the same on both wings, will result in
a straight ahead nose drop with no rotation about the roll axis.
Not all stalls are symmetrical and the pilot will experience an
abrupt drop of one wing or the other. The instinctive reaction
to this by the inexperienced will be a reaction to lift the fallen
wing by using the aileron. WRONG! Only the rudder can effectively
stop the rolling of the aircraft. The falling wing can be decisively
raised only with opposite rudder. This rudder causes the falling
wing to increase in speed by moving forward. You may still be
stalled but the rotation was caused by a non-symmetrical stall.
Rudder can make the stall symmetrical without the rolling.
When the angle of attack reaches a certain point the drag is so great that full power will be inadequate to maintain altitude. At this point you are flying 'behind the power curve'. In this condition your only recourse is to sacrifice altitude by lowering the nose. Without sufficient altitude to allow the aircraft to resume unstalled flight, this is not a viable option. This is the flight situation that arrives in entry to a full-power-on stall. With power full and stalled any misuse of the rudder or ailerons will precipitate a relatively quick spin entry.
Rudder
in the stall
A spin can be prevented even when aggravated by the ailerons
if the pilot maintains directional control through use of the
rudder. A spin can only occur with the addition of yaw in the
stall. The rudder can and should be used to prevent any yaw in
the stall and the recovery procedure. The correct use of rudder
in stalls is essential. The rudder controls the yaw which means
it can keep the speed of each wing the same or cause one to be
ahead (faster) than the other. The slower wing will stall first
and drop. Any effort to raise the wing with aileron will add drag
and deepen the wing's stall.
The rudder is the last control to lose effectiveness. Even in the stall if there is some forward momentum there is some degree of effectiveness. In a stall entry you first lose aileron control, then elevator and lastly rudder. On recovery, you gain rudder control first then elevator and lastly aileron. As the most effective control during slow speed maneuvers rudder, correctly applied, can compensate for the lost effectiveness of the ailerons. The rudder can be used to keep the wings level to the relative wind. Such level wings causes the stall break to be without a wing dropping. Keeping the ball of the inclinometer in the center gives assurance that the tail is following the nose. This is coordinated flight. If the heading indicator is held steady with a very gradual application of right rudder, little or no aileron movement will be required to keep wings level.
First
stall instruction (Instructor)
A student pilot's introduction to stalls will imprint his
entire flying career. Practically everything written on stalls
is inductive to terror. If the first stall is abrupt, violent,
and with sharp wing drop every instinctive reaction will aggravate
and prolong the student terror. Instead, the instructor should
put the student in charge and begin a slow smooth gentle entry
with rudder control closely monitored by the instructor. Very
gradually over the entire training period the stalls may/should
be aggravated. The student introduction to turbulence and weather
should be just as gradual both as to duration and severity. The
better a pilots knowledge of wind and weather patterns the better
able he will be to select desirable conditions. There is nothing
wrong with not enjoying either stalls or turbulence.
Stalls should be introduced on the second flight.... gently. After clearing turns expose the student to the nose drop that occurs on power reduction. Repeat the power reduction and have the student hold the nose level with the yoke. Have the student apply carburetor heat and reduce the power to off while holding the nosed to prevent loss of altitude. The yoke movement should initially be very gradual and increase logarithmically as speed decreases. The last few inches of yoke movement should be UP and back.
The recovery must be positive in reducing the angle of attack but not more than required to lower the nose to or slightly below the horizon. The abruptness of the recovery should be in direct proportion to the abruptness of the stall. Any recovery action in excess of what is needed to return the wing to an effective angle of attach can only delay the recovery and cause an excessive lost of altitude. At the same time, full power is applied to increase speed and thereby reduce the angle of attack. Some aircraft have sufficient power to literally fly out of a stall. The final recovery is to resume coordinated use of the flight controls.
Proficiency stalls are those stalls expected of the pilot applicants. Included in stall training will be such demonstration stalls as the accelerated stall and the oscillation stall which are not required except for flight instructor tests. Demonstration stalls are not part of the PTS but should be taught and demonstrated since they can occur when you least expect them.
Stall
Lesson
Introduce this lesson in slow cruise where you allow the student
to look to the wing tips and note that the rudder can be used
to make one wing move forward of the other. Knowing this, advise
the student that in a stall he should always step on the high
wing. Oscillation stalls are performed in a power-off and clean
configuration. The yoke is continuously held back from a gentle
and smooth entry. The rudder is used to raise any wing that should
drop and start a roll. Always step on the high wing. In a stall
use full rudder with rapid movement to catch a falling wing before
it gets down too far. Hold the yoke level to cockpit.
PTS Stalls
PTS wants 20-degree banks for power-on stalls and up to 30
degrees for power-off stalls. The stall recovery puts the nose
on or very slightly below the horizon. The pilot applies full
power and corrects for any stall-induced roll with the rudder.
Objectives
of stall instruction
The objective of stall practice is to develop awareness of
the mechanical and physiological cues that precede the stall along
with the appropriate reactions to effect recovery. We practice
intentional stalls so that we can react appropriately to the consistency
and predictability of a given aircraft. Instinctive control reactions
are both wrong and potentially dangerous. Modern aircraft have
opposite ailerons with differential travel to reduce but not prevent
the dangerous aspects. Appropriate reaction requires coordinated
used of the rudder and forward elevator to reduce the angle of
attack. Even the best combinations of these features can be offset
by weather (icing), weight, loading and power. The more violently
a stall is entered the more violent will be its break. Recognizing
the sight, sound and touch of a stall entry is to be followed
by an immediate reduction of pitch attitude.
There are three purposes for instruction in stalls, none of which
have to do with the actual stall performance. We want a pilot
to be familiar with the flight conditions most likely to precipitate
a stall. The second objective in stall instruction is for the
pilot to become familiar with the sight, sound and feel of an
approaching stall. The third, and last purpose, is that the pilot
take immediate and proper corrective action.
Knowing where stalls are likely to occur is the second awareness objective of practicing stalls. By practicing a variety of stalls at altitude you learn enough about your aircraft to know how much forward yoke movement is required for recovery along with how much altitude is required. The availability of power makes a significant difference in the recovery attitude and procedure. Some aircraft have sufficient power to effectively fly out of the stall; others do not. Know your airplane.
The reason for doing training stalls is to help the pilot overcome the dangerous instinctive reactions and to initiate an immediate stall recovery based on 'knowing' what to do. Proximity to the ground is an inhibiting factor that must be overcome. Regardless of altitude the elevator control must be moved forward to reduce the angle of attack, only then can the stall recovery be initiated.
Clearing
turns
There are certain aspects of training stalls that are the
same for all of them. Every stall should (must) be preceded by
90 degree clearing turns left and right. (The clearing turns should
be as precise as to amount of turn, angle of bank, altitude, and
heading as though they were part of the stall process.) The well
performed practice stall will result in an initial loss of 100'.
The actual stall may be called as incipient, partial, full, or
aggravated. The longer a stall is aggravated or held, the more
airspeed decreases. This means either more power or altitude will
be required during recovery. The recovery is always with full
power, no flaps, in a climb, and at best rate of climb speed (65
kts). An old FAA recommendation was that 300' be gained during
recovery but the time required is not practical in many cases.
Trim for any climb.
Where to
practice
One major problem of instruction is where to go to safely
practice stalls. Since you will be flying in all directions during
this period you want to be within 3000' of the earth's surface.
Avoid flight at altitudes where the hemispheric rule applies.
You try to find an area clear of an active fly way between airports
and preferably clear of any airways or vectoring routes. I have
found it best to operate over mountain ridges and plateaus which
allow legal operations at such altitudes as 4300' or 3800'. This
gives some additional glide range to the lowlands. I would avoid
any operations at thousands of feet as well as those at the 500s'
since you will be exposed to either IFR or VFR transient aircraft.
I have often utilized radar advisories where available during
these training operations.
On a particularly poor visibility and ceiling day, I obtained a Class Delta clearance to practice in the top 600' of their airspace. I was above arrival/departure traffic and any traffic 'should' obtain a clearance to get where I was. Just monitor the radio and have a good time right above the airport.
Not so real
Stalls
It is nearly impossible to create a 'practice' stall that
has all the qualities of an unintentional stall. However, the
recovery from both the intentional and unintentional stall will
be the same. Efforts to create the accidental or unintentional
stall may be so emotionally traumatic that the mere mention of
a stall causes an anxiety attack. The mental and emotional attitude
of the student toward a stall and the recovery is perhaps more
important that the actual performance.
The deliberate stall is an integral part of a normal landing.
The student should be talked through a landing to understand how
the aerodynamics of a stall with all of its control feel and sinking
sensations makes the
landing possible.
Power is not needed either to perform or recover from a stall. (Use a paper airplane to demonstrate) The use of power in the stall will make for a higher angle of attack and power in the recovery will reduce the loss of altitude. The essential of any stall recovery is to be decisive, deliberate and timely in the recovery.
Stall
Exercises
Select an altitude that is less than 3000' AGL over a single
hill that is not at an even thousand or five-hundred. In a C-150
make clearing turns. Apply carburetor heat and reduce power to
1500 and hold heading and altitude while airspeed decreases to
60 knots. Increase power to 2000 rpm. Trim for 60 knots. Have
the student slowly but constantly raise the nose to the first
whimper of the stall horn and then lower the nose to return to
original altitude at 60 knots. Use the rudder to maintain heading.
Do it again but get a more pronounced stall warner before recovering.
Do it again and reach the first aerodynamic signs of a stall before
lowering the nose and recovering. Continue into progressively
more deeply into the stall up to a full stall and recovery. All
of this maneuver can be performed within 100' of altitude with
no change in power setting.
Show that any 'wing drop' is due to a rudder problem and that
using the aileron will not solve the problem but rudder will.
Stall exercises (Instructor)
The great weakness in stall/spin training is that it is unsafe
to practice or simulate those situations that are most likely
to surprise a pilot. We can teach and train for:
Stall
Avoidance Practice at Slow Airspeeds
1. Hold heading and altitude while reducing power and trimming.
2. Hold heading and altitude with stall warner on.
3. Demonstrate elevator trim from neutral to full up.
4. Note left turning tendency and rudder effectiveness.
5. Demonstrate required right rudder.
6. Demonstrate rudder effect by releasing/applying.
7. Make right/left turns without rudder to show yaw.
8. Practice slow flight climbs, descents, turns.
9. Demonstrate flap extension/retraction at slow speeds to avoid
stall.
10. Distractions
11. Check altitude loss. Note airspeed loss in transition.
Stall
Recognition
The stall is because of the angle of attack not the airspeed
or attitude.
a. Mushy controls
b. Change in pitch of exterior air flow
c. Buffet, vibration, pitching, sounds
d. Stall warning
e. Body sensing
Natural
stall warning
Some older aircraft do not have stall-warners. The natural
stall warning is a first sensing of buffeting on the horizontal
tail surfaces. The usual stall-warners alerts you up to 10 knots
before the stall. The new FAR 23.207 prior warning but at no stated
point.
Generic
stall Recovery
At recognition reduce angle of attack. The quickness of the
yoke movement should correspond with the abruptness of the stall.
Apply smooth power and establish straight and level or climb as
required. A pilot must make significantly incorrect control input
during the stall to create an incipient spin. Instinctive reactions
are invariably, if not wrong, too much control application. Stall
and spin recoveries are intellectual; not instinctive.
Secondary
Stall
A secondary stall is a 'failure' during any flight test. The
secondary stall occurs when, during the recovery of an initial
stall, the pilot over-controls the recovery. At the slow speeds
involved there is greatly reduced stick forces. It all too easy
to apply enough back pressure to make the secondary stall both
abrupt and violent.
Stalls Down
Low
There is something about ground proximity and low altitude
turns that cause reactions leading to stalls. It could be that
more attention is being paid to the ground than to flying. Many
of the factors that are likely to increase stall speeds exist
close to the ground. Turbulence, increased bank angle, lack of
coordination, and low speeds are most likely.
The quality of the turn for a given angle of bank can make the turning stall either break ahead or create an abrupt wing break which if reacted to by aileron will only make things worse. The unstalled wing aggravates the drop by providing ever more lift. The nose will drop while following the dropping wing. The ground makes the pilot reluctant to lower the nose, even though this is the only possible solution. If power is increased at the turn entry, the increase in speed may be used to offset drag created by the turn. Power applied while in the turn is already too late. Stall speeds increase as the square root of the load factor. A 30-degree bank results in only .15 G increase in load factor. Banks beyond 30-degree can result in dramatic load factor increases as can turbulence. An aircraft at low speed will stall at a relatively small angle of bank. When stalls occur down low there is usually insufficient altitude for recovery regardless of proficiency.
Deep
stall
A deep stall can occur when the aircraft is in a very high
angle-of-attack and high drag configuration as in minimum controllable.
Airplanes, by design, will enter this undesirable mode only when
loaded outside weight and center-of-gravity limits. Recovery from
a deep stall may be possible only by changing the C. G. of the
aircraft. Don't do stalls if you don't know the status of your
C. G.
The deep stall occurs when the rearward center of gravity makes
it so that the nose cannot be lowered with full elevator deflection.
The stall angle of attack is exceeded by a margin well beyond
the normal angle. The pitch-up is rapid and uncontrollable. The
effectiveness of the horizontal stabilizer and elevator is dependent
on the flow of the relative wind over these tail surfaces. The
airflow over the tail surfaces is greatly reduced at slow speeds
and high angles of attack. The nose will remain high with a very
high rate of descent until the tail surfaces stall or until effectiveness
can be restored. The use of full flaps can precipitate this condition
in wind-shear conditions. T-tail aircraft are more prone, simply
because there is no prop-wash to augment any relative wind needed
to load the tail surfaces.
Stall
Recoveries
The better the stall recovery the less altitude lost provided
a secondary stall does not occur. Excess forward elevator in recovery
often leads to an excessive counter and the secondary stall. Any
misuse of the aileron can give a sideslip leading to a spin. The
inclinometer ball is the leading indicator of unbalanced flight.
The lead sentence of this item is correct only if the stall is
not prelude to a spin.
The amount of forward elevator must be referenced with the abruptness
of the stall and the degree of pitch up acquired. The recovery
initiated by the elevators must be correlated with the power/speed
increases. Any turning motion should be corrected after speed
has increased. Any bank should be controlled with the rudder only.
Especially at high angles of attack. Spins result from improper
stall recoveries and uncoordinated stalls. Power is not used if
an incipient spin entry occurs.
When the root of the wing is stalled the disrupted flow of air
over the wing affects the horizontal tail progressively as the
stall progresses toward the wing tip. You will feel the vibration
in the tail surfaces. Under the new PTS this is the time to initiate
your recovery.
Stall
Proficiency (Instructor)
Flight instruction over the years has led to a gradual decrease
in stall instruction and the complete demise of spin instruction.
The fact that a stall is a prelude to a good landing seems to
be beyond consideration. The stall is the point at which the smooth
flow of air over the wing ceases to the extent that the aircraft
is unable to sustain flight. This is the way to land an airplane.
The stigma of the stall began because early aircraft lacked flight
stability and stall predictability. Modern aircraft are, if anything,
too stable for good instruction and too predictable in the stall.
Every successive FAA test guide reduces the stall instruction
required.
Early on in your training you performed basic stalls. Now that
you are getting ready for the flight test you will perform proficiency
stalls. Proficiency stalls are those stalls expected of the pilot
applicants. Included in stall training will be such demonstration
stalls as the accelerated stall and the oscillation stall which
are not required except for flight instructor tests. Demonstration
stalls are not part of the PTS but should be taught and demonstrated
since they can occur when you least expect them.
One other thing that you might try is an oscillation stall to
get used to really using the rudder. Begin like a straight-ahead
power on stall with about 18-1900 rpm. Lift the nose slowly, very
slowly until a stall occurs. The slow wing will always stall first.
Do not correct by lowering the nose. Kick in full rudder to speed
up the trailing wing and break the stall. This will cause the
other wing to stall, kick in full opposite rudder. Do this rudder
work rapidly before the plane can break into a spin. The rudder
is your problem, not the stall.
Stall warners give a ten-knot warning of impending stalls as normally
performed. The accidental inadvertent stalls that I have encountered
occurred simultaneously with the warning. The real objective is
not so much performance as recognition by sight, sound, and feel
so that anticipatory corrections can be made. An imminent stall
is a pre-stall condition that is recovered from before the actual
stall occurs. Power alone may affect the recovery.
The amount of correction applied will vary with the aircraft and
the abruptness of the stall entry. A gentle stall can be recovered
gently. An abrupt stall requires a more positive recovery. Ground
proximity can influence your reaction. (Understatement) Excessive
negative load by excess force can delay the recovery. You want
to reduce the angle of attack the minimum amount required. Recovery
will require only that the nose be lowered to or slightly below
the horizon.
A departure stall should be performed so that the bank is not
allowed to exceed 20-degrees. This will require crossed controls.
A departure stall that allows the bank to increase beyond 20-degrees
has not corrected for the increased lift from the faster outside
wing. Usually the pilot fails to apply sufficient rudder and the
stall is climaxed by an abrupt wing drop which will be aggravated
by the pilot trying to raise the wing with the stalled elevator.
Voila' tout, a spin entry.
A full stall requires that an approach entry speed be used with
power off and configured for landing. Once established raise the
nose and hold heading with rudder. It can be performed in a constant
20-degree bank with coordinated rudder. Incorrect rudder results
in abrupt wing-drop. Full stall occurs when the elevator is full
back and up
Power-Off
Stall
Entry:
Clearing turns. Carb heat and power smoothly off. Hold heading
and altitude with yoke and rudder while aircraft decelerates.
It is important that the yoke be pulled smoothly and logarithmically
back and UP. (The unexpected sound of the stall warner often interrupts
the students use of the yoke. It should not.) A technique for
keeping the wings level is to maintain a constant heading on the
heading indicator. Use the rudder. The first sign of stall is
a slight tremor along the wing. This is the incipient stall. By
bringing the yoke back and up still more a more violent tremor
will we felt. This is the partial stall where the erratic airflow
over the wings reaches back to vibrate off the tail planes. The
tremor followed by a shudder, pitch and roll and nose or wing
drop is a full stall. If the yoke is held back even through the
nose or wing drop this is the aggravated stall. A spin will usually
follow if rudder is applied so as to lose directional control.
There are several common faults associated with the power off
stall. Most students have been influenced by certain texts into
scaring themselves doing the stall. They pull back too quickly
and push forward abruptly. If the yoke is brought back The violence
of stall recovery is proportional to the abruptness of the stall.
The more gentle the stall entry attained by holding altitude and
attitude the more gentle will be the stall.
Recovery:
Recovery is initiated by lowering the nose to or slightly below
the horizon, applying full power, leveling the wings as required,
removing any flaps and initiating a climb. Properly performed
power off stalls should be recovered with a loss of about 100'
before a positive climb rate is achieved.
Errors:
A gentle entry to the stall can be followed by a smooth gentle
recovery. Where the wing begins its stall at the wing root the
turbulence makes it possible to feel the turbulence vibration
as it affects the horizontal tail surfaces. Some students sense
this as the stall, whereas it is an incipient phase likely to
be followed by the tip stall. The abrupt wing drop occurs with
a tip stall where rudder is not applied to cause both tips to
stall at the same time. It ideal stall break is straight ahead.
It can only be achieved when the rudder is properly used.
A variation of the power off stall is sometimes called a 'characteristic
stall'. In this instance the stall is performed with the power
off but the recovery is also accomplished with power off. This
is the stall situation that would occur where an engine failure
exists and the pilot tries to stretch the glide.
Power-on
stall (Partial power)
Entry;
Clearing turns, CH, power 1500, hold heading and altitude while
slowing to 60-kts. Power 2000 rpm or full, hold heading with rudder
as plane climbs and slows. Increase back and up pressure until
stall, relax pressure and allow nose to fall to or slightly below
horizon. Full power and climb at 65-kts. With power at 1300 RPM
this stall is used in making full flaps soft field landing.
Recovery:
Recovery is made by lowering the nose to or slightly below the
horizon and at the same time applying full power and rudder to
maintain heading. Level the wings and initiate a Vy climb.
Density Altitude Recovery:
Lowering the nose to or slightly below the horizon makes the recovery
and power is NOT changed while an effort is made to climb. This
demonstrates the very real problem of a departure stall made at
altitude where additional power may not be available.
Departure
Stall
First you must know what you are trying to simulate. Visualize
a situation where you have just reached rotation speed when a
stopped gasoline truck pulls on to the runway about 500 feet a
head of you. Without thinking, you will pull back on the yoke
and turn to go over and avoid the truck.
Preliminary exercise is to go into slow flight. Look down the
leading edge of the left wing and hit the right rudder. You will
see the leading edge speed up. Relax the rudder and it will fall
back. Once wing, the slowest wing, will stall any time the wings
are not 'flying' at the same speed. Now you know why the wing
drops and how to stop it.
An additional exercise is to slow to 60 knots with power at ~1900
rpm. Very slowly raise the nose to the stall. Hold head with rudder.
make recovery only by lowering the nose to or very slightly below
the horizon. Do not change power as with normal recovery. Leave
the power alone and do a series of stalls one after the other.
You should be able to enter the stalls and make the recovery within
100 feet of altitude. If a wing drops, raise it with rudder not
yoke.
In this particular stall a series of them can be made within a
100' altitude range just be making a smooth recovery and then
slowly enter the stall again. Leave the power alone. Doing several
of these will make you more aware of the variable rudder force
changes required to get a smooth stall break without wing drop.
A rudder exercise can be performed while doing this stall. You
can perform an oscillation stall by 'walking" the rudder
to bring up any wing that drops. How far into the stall you are
into the stall will determine the amount of rudder input required.
In the introduction to this the student should be shown that application
of right rudder causes the left wing to move forward. The trailing
wing will always stall first. Ailerons should be neutral.
When you have solved the rudder problem you can go to banks. Banks
should not exceed 20 degrees regardless of power. The step by
step additions of power in 200 rpm increments should proceed as
before until you get to full power. The geometry of your arm and
hand on the yoke in all stalls is important. You should be able
to pull and LIFT the yoke with only two fingers. This will help
you avoid increasing any bank beyond 20 degrees. If you are flying
and using a full grip on the yoke...stop it now.
I have, for years, used this stall as a confidence maneuver for
students. With power at 2000 and kept there, a repeated series
of stalls can be performed within 100 feet of altitude. Student
just lowers nose to regain flying speed that then enters another
stall. Misuse of the rudder causes a wing to drop. Then the wing
must be raised only after the nose is lowered and flying speed
regained. The cause of a wing dropping can be shown by observing
the leading edge of a wing as it reacts to rudder application.
Whenever a wing has dropped in stall, the stall should be repeated
with corrective rudder applied.
Entry:
First step is to slow the aircraft down at altitude. there would
be nothing wrong to getting down to 55 knots or even 50 knots.
The slower you go the less the nose will pitch up. Since rudder
seems to be a problem you should practice with less than full
power more than a few times. Begin with only 2000 rpm until you
get the rudder so that you break straight ahead. Do the first
series straight ahead with no turns. the higher the nose and power
the more rudder. Keep the heading indicator still with the rudder
and your wings will be level. Try some of these under the hood.
Summary:
Clearing turns, CH, power 1500, hold heading and altitude while
slowing to 60 kts. Power 2000 rpm or full, enter 20 degree bank
as plane climbs and slows. Increase back pressure until stall.
If done properly nose will fall forward. Wing drop or yaw indicates
improper use of rudder. At stall lower nose to or slightly below
horizon, level wings while applying power, raise nose, climb at
65-kts. This stall is best avoided by maintaining correct climb
speed and never banking over 30 degrees in the pattern.
Approach
Stall
This stall is best avoided by maintaining approach speed and limiting
banks to 30 degrees. Failure to maintain ground-track in reference
to runway and wind effect is a common cause leading to this stall
situation.
Entry:
Clearing turns, CH, power 1500, at white arc put in full flaps
while holding heading, altitude and maintaining airspeed at 60-kts.
If done correctly full flaps and 60-kts occur simultaneously.
Enter 20 degree bank and hold altitude until stall.
Recovery:
If nose properly falls forward, apply full power and raise flaps
20 degrees. Initiate climb at 65 kts and bring up rest of flaps.
The yoke pressures change continuously from forward to back as
the flaps are removed. Wing drop is indicative of improper rudder
pressure.
Accelerated
Stall (Instructor)
(No longer FAA required but exposure needed.)
There is an airspeed at which a wing will stall at 1 g in level
flight. This is calculated at gross weight using an airspeed selected
by the manufacturer. You will find this at the bottom of the green
arc on the ASI (Vs1) . With gear and flaps the bottom of the white
arc is Vso. The accelerated stall is a stall that occurs at a
wing loading over 1 g.
There is a portion of any airplane's flight envelope where
the addition of a load factor above 1 g will produce a stall at
a higher airspeed than Vs1 and not hurt the airplane. You will
find this
portion of the flight envelope between Vs1 and Va, which is the
maneuvering speed for that airplane. Within this area we can define
the accelerated stall. Not above Va, because above Va, structural
damage to the airplane has occurred before the accelerated stall
has occurred.
The one common denominator in all stalls is the critical angle of attack. Every stall is a function of angle of attack and not airspeed or load factor, even though these factors are present in the accelerated stall. You can stall an airplane at various airspeeds and load factors, but at only one angle of attack. Angle of attack is the key to understanding stall, especially the accelerated stall.
This stall is unique in that the ailerons are used for the
recovery. It is called accelerated because the stall occurs at
relatively high speeds while the aircraft is subject to greater
than normal G-forces. The factor that causes this is the high
wing loading due to a steep bank. Any steep bank with abrupt yoke
pressure to hold altitude can lead to this stall.
Entry
Make clearing turns at cruise. Enter a 45 degree steep bank at
level altitude and cruise speed. Hold that altitude and bank while
applying carburetor head and smoothly-gradually reduce power to
OFF. Increase back pressure to prevent ANY loss of altitude. If
the back pressure is abruptly applied any stall will be rapid
and severe. If VSI goes down you will go down shortly thereafter.
It this happens, start procedure over again. Yoke must come full
back and up to get stall. The resulting centrifugal forces will
increase the wing loading. The plane will stall at a higher speed
because of the excessive maneuvering loads. Any descent will void
entire procedure. Practice at altitude and keep your turns coordinated
If you have the yoke all the way back and the power is off, you have done as much as you can to make it stall. Try doing the maneuver a bit faster and you may get the break you are looking for. This stall is unique in that the ailerons remain effective so it can be quickly broken just be leveling the wings.
Recovery:
Since stall occurs at a higher speed, ailerons will still be effective
and recovery may be initiated by leveling wings and using rudder.
The accidental entry can occur from any steep bank done with abrupt
yoke pressure while endeavoring to hold altitude. This is the
only stall that does not require the nose to be lowered and in
which the ailerons remain effective. Failure to initiate stall
recovery can result in a power-on spin. Uncoordinated rudder will
give a spin entry. (see spins)
My personal belief is that this particular stall should
have remained as part of the PTS because of the smoothness required
for proper performance and recovery. This is the stall that is
apt to occur when you are turning base to final and you have over-shot
the runway. You increase the bank angle and pull back on the yoke
to hold the nose up. The g-load increases and you do not have
altitude to recover if a spin results. The difference here has
to do with the use of rudder and existence of yaw. Uncoordinated
you get the spin entry, coordinated you get an accelerated stall.
I suggest that you limit your practice of this stall if you are subject to hemorrhoids.
Another opinion:
The real value in learning accelerated stalls is that no other
maneuver so clearly illustrates to the student the relationship
between angle of attack and the stall. Simply performing stalls
with no loading caused pilots to incorrectly relate stall to airspeed
and not attitude..
The accelerated stall is sometimes called the 'moose stall' since
it often occurs when Alaskan pilots attempt to circle a moose.
The steep turn, low altitude, inattention, distraction, abrupt
control movement when mixed with ignorance and overconfidence.
The accelerated stall, correctly performed below Va and accompanied
by a complete explanation by a competent instructor, leaves no
doubt whatever in the mind of the student that any airplane can
be stalled at any airspeed and
at any angle of flight, if critical aoa is reached.
Accelerated
Stall Situations
To unload the wing you "step on the blue" along with
forward yoke to break the stall and lower the load factor. Then
use top rudder to initiate the recovery. Very often in an unusual
attitude, the pilot will pull back on the yoke. The unusual attitude
requires that the angle of attack be lowed and the stall broken.
It is the instinctive response to the unusual attitude that makes
breaking the stall difficult to achieve. Attempting to level the
wings with the ailerons will produce extreme attitude changes
unless the stall is broken first.
If the aircraft is trimmed for an approach speed, a spiral dive derived from an unusual attitude may increase the speed so that leveling the wings will tear the aircraft apart. Excessive load must be reduced by pushing forward on the yoke.
Cross
Control Turn Base to Final Stall
The cross-control stall occurs when the pilot reacts to a
high ground speed due to a tailwind as indicative of a need to
reduce airspeed while on base. This sensed need for speed reduction
occurs just after the pilot notices a turn is required. Then the
pilot realizes that the turn cannot be completed in a normal bank
so more rudder is used to speed up the turn. This then requires
'up' elevator to keep the nose from dropping.. This slows the
aircraft even more and the lower wing stalls and tucks under and
straight down. With less than a thousand feet, no recovery is
possible.
This entire cross-control scenario can be avoided by planning
to fly any downwind leg that is being blown into the runway at
twice the distance away from the runway as a normal downwind.
The benefit compounds by giving a longer base leg with more time
to plan and make the turn to final. It is too bad, even sad, that
the FAA landing booklets only address the problem in their presentation
diagrams. What is needed is a few solutions diagrams that show
how the situation can be avoided.
Things that can help deflect the situation:
1. Diagram the ATIS or AWOS to show both the runway and the wind
velocity/direction vector. This will dramatically show when the
need for a wider downwind leg is required.
2. At a controlled airport you have the option to request a
pattern that gives a headwind rather than a tailwind on base.
The aggravated cross-control stall uses full right aileron and
full left rudder will be totally uncoordinated. The use of full
power into this stall will cause the aircraft l to snap over in
a New York Minute. Aircraft will go inverted if the stall is not
broken immediately.
The deadliest stall is the cross-control stall that occurs
in the landing pattern during a turn from base to final. The precipitating
factor in the stall is in a tailwind on the base leg. The pilot
may have failed to adequately correct for the crosswind on the
downwind leg. The aircraft has drifted into the runway. This makes
the base leg not only short but relatively fast. The speed both
real and by illusion may cause the pilot to overrun the final
approach course, raise the nose to reduce the speed, make a steeper
than normal bank, or worse add top rudder to get the nose around
more quickly. The slightest inattention or distraction will not
catch the resultant nose drop, stall, and the snap roll toward
the low wing will be an unrecoverable spin entry due to lack of
altitude. Although the recovery may be impossible, the prevention
lies in awareness as to how crosswinds tend to reduce the base
leg. With the awareness comes flying a pattern flight path that
will give a longer leg which, even at a higher speed, will allow
a planned normal turn to the final approach course.
Entry:
#1 Usually results from a skidding turn to final where the pilot
overshoots of final makes a steeper bank, uses too little rudder,
nose goes down, and sink rate increases. The pilot tries to raise
the nose with elevator. You have an accelerated stall, spin, and
crash. This stall/spin is major fatality problem because it occurs
too low to make a spin recovery possible.
Avoidance
The skidding turn, ball to the outside of the turn, is the opening
for a spin. NEVER use the rudder to increase the turn rate. The
uncoordinated turn is region where this stall and spin accident
occurs. In crosswinds that are blowing you into the runway double
your perception of the usual distance away from the runway.
Entry:
#2 Aircraft is close to ground so pilot is reluctant to lower
wing into bank. Instead tries to execute turn using excessive
rudder. Excess rudder causes plane to bank into the turn and the
nose to pitch down. Pilot applies opposite aileron to raise wing
and nose up elevator. Attempting to raise a 'dropped' wing by
applying opposite aileron increases the effective angle of attack
and will induce or aggravate a stall. Inside wing will drop and
roll aircraft inverted after accelerated stall.
Avoidance
Fly the correct altitude, pattern size and airspeed for the wind
conditions and you will not have a problem.
Unrecoverable
stall
Entry
The base turn in a following crosswind creates a problem with
holding airspeed. This turn makes the existing crosswind into
a tailwind and the pilot's peripheral vision will detect an increase
in ground speed. If the turn makes the existing crosswind into
a headwind the eye will detect a decrease in ground speed. This
conscious or unconscious perception of speed may and often does
cause the pilot to make unintentional changes in the airspeed.
A constant airspeed is essential for all landings.
The base leg perception of ground speed and maintenance of a single
indicated air speed (IAS) is essential for making the turn to
final. If wind, illusion, or inattention positions your plane
too close to the runway on downwind your base leg will be short.
This most often occurs at night and at small unfamiliar fields.
Students will turn too early with the headwind and too late with
the tailwind. Being too late means that the student has overshot
alignment with the runway. The result is that procedures become
hurried and airspeed unstabilized. Both these problems are made
worse if the downwind leg is flown to give a short base leg. The
dangerous part of this is that the pilot may have slowed below
the proper airspeed. Normal reaction to overshooting is to make
the turn steeper to regain alignment. The combination of slow
and steep is the introduction of a stall spin accident. Abort
the approach and GO-AROUND. Never exceed a 30 degree bank in the
pattern and use sound as indicative of airspeed changes.
A high proportion of accidents seem to result from these improperly
performed turns at low altitudes. Low airspeeds combined with
steep turns result in stress and instinctive reactions. I would
think that the mere factor of ground presence causes excessive
distraction. The making of turns at low altitudes is not a common
general aviation procedure. The distraction of rapidly moving
ground at unfamiliar angles is unavoidable. There are illusions
which result in inappropriate control application. The nose will
always drop toward the low wing.
The pilot who normally flies solo or at less than gross weights
must be prepared for higher stall speeds and load factors when
fully loaded. As a reminder a 20% increase in weight will give
a 10% increase in stall speed. The combination of all factors
result in an unexpected stall followed by a spin entry. The usually
safe 30 degree bank can give a 50% higher stall speed if it is
performed in moderate turbulence. Most of our low level turns
in training are performed at much less than gross weights. Once
out of training our aircraft weights get much closer to gross.
Now we have set the scenario for a stall spin accident that beings
at low altitude. Wings tend to stall always at the same angle
of attack. We can increase the load factor by making a steeper
bank. Being at gross weight frames the picture. Gross weight,
higher load factor and at the stall angle of attack. Now comes
the surprise. Add just one good shot of turbulence. The stall
onset arrives and it happens at a much higher airspeed. The pilot
has never stalled at such a high speed before. The pilot feels
deceived by his plane and instruction in the final moments. It
was not supposed to happen this way.
Trimmed
go-around stall
The elevator trim stall is illustrative of what can happen when
full power is applied for a go-around with full nose-up trim.
Full power application under such conditions can cause abrupt
pitch up such that any rudder use may provide a spin entry, surprise
and over-power the pilot's ability to hold the yoke forward. Can
be prevented if sufficient control force is applied to prevent
pitch up before clean up. A pilot who does not keep track of his
trim can get into stall trouble. Sudden application of power with
pilot not expecting need for extra right rudder application due
to P-factor .
Entry:
Landing approach configuration trimmed for speed. Partial power
with little elevator or rudder pressure +distraction. The stall
is initiated with partial power partial to full flaps and trimmed
for approach speed. When full power is applied the nose will pitch
high and to the left.
Recovery:
If the pilot does not counter the forces and remove the trim he
can be physically overcome. In an actual go-around situation the
altitude loss required could be below ground level. (understatement)
At stall, recover to normal climb. Stress attitude, control pressures,
and trim during go round.
Errors:
While in full flap stall with full flap attempted climb. likely
secondary stall. Full flap stall with rapid removal of flaps to
produce secondary stall. Accidents occur most often by failure
to initiate go-around before ground obstacles become a factor.
To simulate an accidental stall the instructor must get the student
totally focused on an unrelated factor. The easiest factor is
altitude. Demand that throughout the following maneuver that the
altitude must not be allowed to vary. Heading may be used alone
or in conjunction with altitude as the concentration factor. Eliminate
an essential element from being able to hold altitude (power)
or heading (rudder). The clock can be used as a focus item as
by having the student call out the number of seconds every seven
seconds or even every four seconds. What we are doing is setting
up a mental set that eliminates flying the aircraft as a factor.
Now we can get the accidental stall.
Regardless of the stall type being performed, it is vital that
the rudder be used during entry and recovery. In the absence of
yaw a spin will not occur.
Engine
Failure at Altitude Stall
Entry:
As always, clearing turns. Carburetor heat and power to idle.
Retain altitude and turn immediately toward possible landing area.
Trim for best glide speed. If in doubt trim all the way back.
Use your checklist. Make your field selection early and stay with
your choice.
Changing your mind should be only as a last resort. If you have
some power available you can approach at a lower touch down speed.
Flaps only when field is certain. You and the aircraft can bear
horizontal impact better than vertical impact. An impact below
45 knots is both survivable and likely non-injury.
Takeoff
Engine Failure Stall
The standard emergency for engine failure on takeoff is to land
ahead into the wind. Make no more than 30 degrees of heading change
to locate the best landing place. An emergency landing into a
10 kt wind at a full flap stall speed of 35 kts gives you a survivable
ground contact speed of 25 kts. However, there is another option
possible if sufficient altitude has been gained before failure.
(A good reason to always takeoff and climb at best rate, Vy) To
determine this altitude it is necessary to practice at altitude.
Entry:
At altitude initiate climb at best angle of climb (Vx) on a North
heading, pull power and hold pitch attitude to simulate engine
failure. Repeat exercise but lower nose to get best glide speed.
Have the student execute a right turn in a 30 degree bank to 240
degrees. Note the altitude loss. Do the same 240 degree turn to
the left. Note the altitude loss. Now do both turns with 45 to
60 degree banks. and note altitude lost. Add 50% to the altitudes
as a fudge factor for actual use. From these turns you should
decide that the steep turn loses the least altitude. Having determined
this we now can add some factors for returning to a runway. If
there is any crosswind always make the turn into the wind since
it will bring you back to the runway. If there are parallel runways
turn to the parallel since only 180 degrees of turn will be needed.
Crossing runways may even need less turn.
If the tailwind is 10 kts it will double the required runway for
landing. If takeoff is into relatively strong head wind the ground
speed of the turn will increase dramatically. The increased ground
speed decreases the time available to complete the turn. Turn
errors multiply if the pilot slows the aircraft in an effort to
slow the ground speed.
Recovery:
Instinctive and most likely fatally incorrect effort is to turn
back. Lower nose to best glide attitude. Landing attitude under
control assures survivable ground contact. This is the best 'every
time' solution until you have determined your personal 'turn back'
limits with a fudge factor.
Engine
Failure on Final Stall
There is always an instinctive effort to maintain 'correct' relationship
of runway to nose of aircraft. Desire to keep from losing altitude.
Entry:
Simulate power loss on final in full flap landing configuration.
Student is to avoid losing over 100 feet in next 20 seconds while
calling out every five seconds on clock. Using elevators to keep
from losing altitude for 20-30 seconds. Stretching glide fails
as ever increasing pitch results in stall as aircraft runs out
of airspeed and altitude at the same time.
Recovery:
Bring up all flaps to extend glide. Maintain glide speed. No heading
changes beyond 30 degrees. Accept altitude loss while bringing
up flaps. Fly in ground effect. Trim.
The correct procedure for this can be easily practiced. On short
final at about 400', simulate the loss of power, have the student
immediately remove all flaps while maintaining approach speed.
Accept the immediate loss of altitude as it is traded off for
up to 1/2 mile of glide range. Try it.
Landing
Flare Stall
There are pilots who use trim is make the flare to landing. This
is a trim practice not uncommon among Piper pilots. Piper's become
quite heavy in the flare and pilots often use trim to ease the
load. An aircraft trimmed in this manner during a go-around can
give an extreme nose-high pitch attitude and a stall or spin.
This is especially true in higher powered aircraft. This should
be simulated only at altitude. It is, also, an excellent demonstration
that the application of only power causes a decrease in airspeed
When level but at a pitch attitude beyond the stall angle of attack,
any movement along the roll axis will make the rising (outboard)
wing to decrease its angle of attack while the descending (inboard)
wing will increase its angle of attack. The rolling and turning
of the aircraft is caused by the differing lift and drag of the
two wings. Encountering a cross wind when trimmed for short field
approach while not applying enough forward yoke pressure to maintain
airspeed during the 1/2 Dutch roll cross control descent.
Entry:
Enter into fully trimmed slow flight both with and without flaps.
Demand that your student immediately slow an additional 10 kts
due to imaginary intruding traffic. Or, have student do this while
getting a pencil from between his feet. Distract, give problems
which will cause student to enter stall situation.
Recovery:
Initiate go-around immediately. Lower nose and get into ground
effect while applying full power. If the nose-wheel hits continue
the go-around and avoid moving the yoke from level flight position.
(See nose-wheel landings)
Premature
Flap Retraction Stall
Entry:
Initiated at altitude from full flaps descent and level off to
below full flap stall speed. Apply full power and make most rapid
retraction of flaps. Results in full/partial stall. In a steep
climb the use of right aileron and no rudder to keep the flight
path straight will cause a spin entry. The left wing will drop
and roll, the power will give yaw and a left spin is entered without
the use of rudder.
Recovery:
Milk flaps at least half of flaps off on any go-around until Vx
is reached and climb initiated.
Go-around
in a Right Crosswind Stall
Entry:
Simulate slipping approach to the right with proper airspeed and
trim. Right aileron and left rudder. Full power go-around and
set pitch without neutralizing rudder.
Recovery:
Don't exceed level attitude in go-around until control and airspeed
are obtained.
Slow
Flight in Pattern Stall
Attention diverted from flying to traffic. This may result in
loss of altitude on downwind and a corresponding low-altitude
base leg turn.
Entry:
In simulated traffic pattern at altitude, reduce power and increase
pitch. Continue to slow down and increase pitch then create diversion
of attention to prevent notice of near stall condition.
Recovery:
Lower nose, trade altitude for speed if necessary. Full power.
Clean up and go-around.
Short Field
Takeoff Stall
The short field takeoff requires that the pilot set the pitch
attitude so that the POH Vx speed will allow the aircraft to perform
at its maximum level for obstacle clearance. Pilot control must
be positive, precise, and coordinated.
Entry:
Premature rotation before Vx with inadequate rudder control. Insufficient
rudder often cause aileron use to create a slipping turn to the
right. From right turn stall/spin caused by excessive right aileron.
At stall spin is very abrupt, "over the top", and to
the left. From left turn 'P-factor" gives nearly correct
coordination and spin entry is slower.
Recovery:
Abrupt lowering of the nose to trade any altitude for airspeed.
Full power. Get into ground-effect. Get speed before climbing.
Abort if space permits.
Falling Leaf
Stall
You can do a falling leaf stall by doing a straight-ahead
power-on stall and hold the nose straight by using the rudder
to prevent wing-drop. This is a great rudder exercise and confidence
builder.
More
on Stalls
Ground school and flight school presentations of stalls are defensive
measures and both act as stall awareness insurance. The instructional
purpose of these stalls is to emphasize the importance of maintaining
coordination in takeoffs and landings. The total actual stall
performance time probably does not exceed 30 minutes for any given
pilot. This would indicate that we do not spend enough time refining
the stall prevention/recover reflex. After certification very
little review of the stall phases occurs. Flights seldom include
any stall awareness practice.
Best awareness review is to set up stall situation where an uncoordinated
rudder condition will exist. The critical angle of attack can
be exceeded from any flight condition. Even the nose below the
horizon can cause the wing to exceed the critical angle of attack.
One practice exercise of the stall can be directed toward the
endurance speed of the airplane. At altitude reduce power while
holding altitude and a Vref indicated airspeed which can be maintained
at the lowest power. Once the minimum power and speed combination
that maintains altitude has been attained, you are at the endurance
speed/minimum sink speed. The minimum sink speed is a glide speed
that, through the use of power can be used to exceed any maximum
glide range. Trim for hands-off.
From this configuration lower the nose slightly and wait for the
plane to recover back to its level flight condition. Next apply
back pressure to lower the speed by up to 10 knots and hold the
airspeed constant with only yoke pressure. After an initial climb
the aircraft will begin to lose altitude. You have placed the
aircraft 'behind the power curve' for this particular configuration.
The nose must be lowered for any recovery to be possible. This
same procedure can be configured for full power operation with
the nose so high that altitude is barely maintained. Any additional
raising of the nose will cause a descent even with full power.
Induced drag is greater than any lowering of parasitic drag. Only
a lowering of the nose and a loss of altitude will permit a return
to normal flight.
Any flight in this area of reversed command requires the pilot
to recognize the condition and do the exact opposite to what works
on the front side of the power curve. The most common occurrence
of the reversed command situation occurs when the pilot uses yoke
and power in combination of a constantly decelerating landing
approach. From a slightly low long final a bit of power is used
to raise the nose. After a few seconds the apparent glide path
again becomes slightly low. A bit more power is added for another
apparent correction. What is not noted, is that the airspeed has
dropped with every bit of additional power. This time the plane
drops more quickly below the glide path. More power is added to
maintain the glide path but now the power increase does not solve
the glide path problem. You are now in the area of reverse command
and only a lowering of the nose will resolve the problem. The
determining factor now becomes one of available altitude. With
available altitude a recovery is possible by lowering the nose.
Without available altitude no recovery is possible. This is why,
any time you are low on the approach glide path, an application
of full power while retaining airspeed is the best, safest, and
only appropriate correction. Power for altitude, pitch for airspeed
rides again.
Stall
Review
If a pilot can avoid those distractions caused by not keeping
ahead of the airplane he has eliminated most of the precipitating
causes of accidental stalls. Once out of those woods, however,
you must watch for a alligators hiding in the grass. Those little
surprises that always occur at the most inappropriate moments.
These distractions will affect your aircraft control over speed,
altitude, and heading. Any distraction be it malfunction, traffic,
or radio that reduces basic aircraft control is a probable cause
for an accidental stall. An abrupt full stall can put your nose
straight down. Even then, your trained reflex should make you
put the yoke forward to break the stall. Panic reactions in crises
situations are more likely to kill you than trained reflex.
Stall spin accidents are still occurring at a rate of one-per-day
as they have for many years. The cause is usually a distraction,
followed by lack of recognition which is followed by delayed recovery.
Delayed recovery is usually due to instinctive rather than trained
reactions to seeing the ground over the nose. Instincts will inhibit
recovery action. The hazards of unintentional stalls can be avoided
by:
1. Avoidance of low and slow flight.
2. Limiting pattern banks to 30^
3. Keeping some power on until just before touchdown.
4. Keeping your hand on the throttle
5. Using carburetor heat prior to power reduction.
6. Avoiding a pitch attitude that covers the horizon.
7. Don't look backwards to see the ground.
8. Always fly with a trimmed airplane.
9. Don't carry on conversations during critical flight maneuvers.
10. Let discrepancies wait for resolution on the ground.
Ask a student how high the nose is above the horizon when practicing
stalls and the handee you get will be between 20 and 30 degrees.
Fact is it is less than half that without flaps and very near
level when with full flaps. No flap power-on stalls will be less
than 15 degrees unless entered at higher speeds. The usual stall
attitude is the same as when a tail-wheel aircraft sits on level
ground.
At altitude slow to 1.5 of clean stall speed and do some turns
at 30-degree while holding altitude. Now, reduce the speed by
10 knots and do the same. Notice the change in control feel and
response. Try it again still slower and note that only by the
addition of power can you maintain altitude and that little margin
above stall remains. Learn the sounds and feel of near-stall flight.
Stalls
in Brief
C-150
POWER-OFF STALL........ POWER-ON STALL ........DEPARTURE STALL
CLEARING TURNS ..........CLEARING TURNS......... CLEARING TURNS
CARB HEAT ......................CARB HEAT .....................CARB
HEAT
PWR TO OFF ....................PWR TO 1500 ...................PWR
TO 1500 HOLD
HDG. & ALT..................... HOLD HDG. & ALT. .........HOLD
HDG. & ALT.
R-RUDDER AS REQD.......R-RUDDER AS REQD ......R-RUDDER AS REQD.
BUFFET OR STALL .........SLOW TO 55 KTS ............SLOW TO 55
KTS
YOKE RELAX ..................FWARD PWR UP ............. PWR UP
2000/FULL
NOSE TO/BLOW HRIZN R-RUDDER ........................20 DEGREES-CENTER
BALL LEVEL WINGS
BUFFET OR STALL .........BUFFET OR STALL ..........FULL POWER-CLIMB
65 KTS
YOKE FORWARD ...........YOKE FORWARD ............YOKE FORWARD
R-RUDDER/HOLD HDG. .NOSE TO/BELOW HRIZN NOSE TO/BELOW HORIZON
LEVEL WINGS .................LEVEL WINGS ..................LEVEL
WINGS
F-POWER-CLIMB ...........65K F-POWER-CLIMB .....65K CLIMB
R-RUDDER FOR HDG. ....R-RUDDER TO HOLD HDG.
APPROACH STALL............... .....ACCELERATED STALL ..........FULL
FLAP GO-AROUND
CLEARING TURNS .....................CLEARING TURNS ................FULL
POWERCARB HEAT
......................................................45 DEGREE
STEEP TURN ......HOLD NOSE LEVEL
PWR TO 1500 CARB HEAT/.......YOKE BACK R-RUDDER-......HOLD HDG.
HOLD HDG. & ALT. ...................REDUCE PWR/YOKE BACK...FLAPS
UP 20
WHITE ARC REDUCE PWR/......YOKE BACK...........................
.MILK BELOW 50KTS
FULL FLAPS REDUCE PWR/.....YOKE BACK 60-65 KTS.........HOLD HDG.
& ALT.
PWR OFF/.....................................YOKE FULL BACK...
.............FLAPS UP20 DEGREE ........
.L-R BANK ..................................IF ANY LOSS OF ALT.
CLIMBHOLD ALTITUDE ...........START OVER R-RUDDER-......HOLD HDG.
BUFFET OR STALL BUFFET OR STALL
YOKE FORWARD .....................USE AILERONS TO LEVEL......
LEVEL WINGS FULL POWER
FULL POWER R-RUDDER TO HOLD HDG.
FLAPS UP TO 20 DEGREES (Not FAA required)
CLIMB SPEED 60-65 KTS
FLAPS UP
CLIMB 65 KTS
R-RUDDER TO HOLD HDG.
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Continued on Carburetor
Ice and Heat