Since stalls are the cause of
much concern among student pilots and the non-flying public, we will discuss them
here. We mentioned that an airplane must attain flying speed in order to take
off. Sufficient airspeed must be maintained in flight to produce enough lift
to support the airplane without requiring too large an angle of attack. At a
specific angle of attack, called the critical angle of attack, air going over a
wing will separate from the wing or "burble" (see figure 1 ), causing the wing
to lose its lift (stall). The airspeed at which the wing will not support
the airplane without exceeding this critical angle of attack is called the
stalling speed. This speed will vary with changes in wing configuration (flap
position). Excessive load factors caused by sudden manoeuvres, steep banks, and
wind gusts can also cause the aircraft to exceed the critical angle of attack
and thus stall at any airspeed and any attitude. Speeds permitting smooth flow
of air over the airfoil and control surfaces must be maintained to control the
Flying an airplane, like other
skills that are learned, requires practice to remain proficient. Professional
pilots for the major airlines, military pilots, and flight instructors all
return to the classroom periodically for updating their skills. Good judgment
must be exercised by all pilots to ensure the safe and skilful operation of the
airplanes they fly.
fig 1 airfoil approaching and entering a stall
Stalls can be practised both
with and without power. Stalls should be practised to familiarize the student
with the aircraft’s particular stall characteristics without putting the
aircraft into a potentially dangerous condition. A description of some different
types of stalls follows:
(can be classified as power-on stalls) are practised to simulate
takeoff and climb-out conditions and configuration. Many stall/spin accidents
have occurred during these phases of flight, particularly during overshoots. A
causal factor in such accidents has been the pilot’s failure to maintain
positive pitch control due to a nose-high trim setting or premature flap
retraction. Failure to maintain positive control during short field takeoffs
has also contributed towards accidents.
(can be classified as power-off stalls or reduced power stalls) are
practised to simulate normal approach-to-landing conditions and configuration.
Simulations should also be practised at reduced power settings consistent with
the approach requirements of the particular training aircraft. Many stall/spin
accidents have occurred in situations, such as crossed control turns from base
leg to final approach (resulting in a skidding or slipping turn); attempting
to recover from a high sink rate on final approach by using only an increased
pitch attitude; and improper airspeed control on final approach or in other
segments of the traffic pattern.
can occur at higher-than-normal airspeeds due to abrupt and/or excessive
control applications. These stalls may occur in steep turns, pull-ups, or
other abrupt changes in flight path. For these reasons, accelerated stalls
usually are more severe than un-accelerated stalls and are often unexpected.
The key factor in recovery from
a stall is regaining positive control of the aircraft by reducing the angle of
attack. At the first indication of a stall, the wing angle of attack must be
decreased to allow the wings to regain lift. Every aircraft in upright flight
may require a different amount of forward pressure to regain lift. It should be
noted that too much forward pressure could hinder recovery by imposing a
negative load on the wing. The next step in recovering from a stall is to
smoothly apply maximum allowable power to increase the airspeed and minimize the
loss of altitude. As airspeed increases and the recovery is completed, power
should be adjusted to return the aeroplane to the desired flight condition.
Straight and level flight should then be established with full co-ordinated use
of the controls. The airspeed indicator or tachometer, if installed, should
never be allowed to reach their high-speed red lines at anytime during a
If recovery from a stall is not
made properly, a secondary stall or a spin may result. A secondary stall is
caused by attempting to hasten the completion of a stall recovery before the
aircraft has regained sufficient flying speed. When this stall occurs, the
elevator back pressure should again be released just as in a normal stall
recovery. When sufficient airspeed has been regained, the aircraft can then be
returned to straight-and-level flight.
Students are taught to avoid
steeply banked turns at low altitude. If you overshoot the extended centreline
on a turn from base to final, there is a tendency to “cheat” by applying inside
rudder to increase the rate of turn — which requires opposite aileron to
maintain the bank angle. The skidding turn tends to make the nose drop requiring
back pressure on the control column.
In an extreme case, the result
can be a full back control column with full opposite aileron and full inside
rudder. The inside wing will stall first resulting in a sudden incipient spin.
This is sometimes referred to as an “under the bottom stall”.
A top-rudder stall or “over the
top stall” can occur when the aircraft is slipping. The aircraft should roll
towards the higher wing at the point of stall.
More on Stalls
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.
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 proper 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
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
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
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 (POH)
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 difference. Some aircraft have critical approach airspeeds that do
not follow the rule because of control and ability to go-around considerations.
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.
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)
3. 1 and 2 have to do with an aircraft that has exceeded its critical angle of
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. The noise
you first hear is the vibration of erratic air hitting the tail surfaces.
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.
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 span-wise 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. This is a defence against the
rudder-shy pilot who reacts with aileron for a wing drop rather than rudder..
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
rudder 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 a short strip 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.
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
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 while being
built.. 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 un-stalled 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 manoeuvres 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 centre
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
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.
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. Avoid any operations at even thousands of feet as well as
those at the 500s' since you will be exposed to either IFR or VFR transient
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
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.
As such, the procedural "stall"
we learn, practice, and mimic for the examiner bears little-to-no resemblance
whatsoever to real-life inadvertent stall/spin scenarios--the stuff we as pilots
must be on guard for and be prepared to deal with. In fact, one Princeton
University study revealed the following about stall-only (no spins!) fatal
60 percent of the cases,
turning flight preceded the fatal stall accident.
Turning and/or climbing flight preceded 85 percent of the fatal stall
Only 15 percent of fatal stall
accidents involved neither turning nor climbing prior.
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.
11. Check altitude loss. Note airspeed loss in transition.
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 requires 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.
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.
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 un-stalled 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.
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 centre-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 centre 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.
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.
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 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.
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
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)
For propeller-driven aircraft it makes a
difference; with power off stalling speed is somewhat below the power-on
stalling speed, because with power on the speed of the air just behind the
propeller is above the IAS. So for a given angle of attack there is a somewhat
greater lift with power on.
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 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.
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. One wing, the slowest wing,
will stall first 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 heading 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 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.
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.
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.
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.
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
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.
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
manoeuvring 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.
Make clearing turns at cruise. Enter a 45 degree steep bank at level altitude
and cruise speed. Hold that altitude and bank while applying carburettor 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 manoeuvring 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 manoeuvre 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 levelling
Since stall occurs at a higher speed, ailerons will still be effective and
recovery may be initiated by levelling wings and using rudder. The
accidental entry can occur from any steep bank done with abrupt yoke pressure
while endeavouring 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)
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.
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 lowered 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 levelling 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 few hundred feet of altitude, 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:
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.
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 to snap over instantly. 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.
#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.
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.
#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.
Fly the correct altitude, pattern size and airspeed for the wind conditions and
you will not have a problem.
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 un-stabilized. 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
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 .
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.
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.
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 manoeuvre 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
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.
at Altitude Stall
As always, clearing turns. Carburettor 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
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.
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. Consider a crossing taxiway.
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.
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.
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.
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.
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
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.
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.
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)
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.
Milk flaps at least half of flaps off on any go-around until Vx is reached
and climb initiated.
a Right Crosswind Stall
Simulate slipping approach to the right with proper airspeed and trim. Right
aileron and left rudder. Full power go-around and set pitch without
Don't leave level attitude in go-around until control and airspeed are
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.
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.
Lower nose, trade altitude for speed if necessary. Full power. Clean up and
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
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.
Abrupt lowering of the nose to trade any altitude for airspeed.
Full power. Get into ground-effect. Get speed before climbing. Abort if space
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.
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-degrees
3. Keeping some power on until just before touchdown.
4. Keeping your hand on the throttle
5. Using carburettor 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.
8.5 When distracted, you should be able to fly the plane with rudder alone, no
9. Don't carry on conversations during critical flight manoeuvres.
10. Let discrepancies wait for resolution on the ground.
Stall strips are put on the leading edge
of an aircraft wing is designed and placed to prevent an abrupt wing-tip stall,
but instead to allow any stall to move gradually out from the fuselage to the
wing tip. The stall strip's purpose is to cause a stall before any part of the
outboard part of the wing stalls. This means a decreased abruptness of any wing