Flight Performance Factors
TORQUE EFFECT ON AEROPLANE
https://www.youtube.com/shorts/EzrGIpN3c-4
UNDERSTANDING TORQUE AND EQUAL & OPPOSITE REACTION IN
FLIGHT https://www.youtube.com/shorts/ECr9ANUwIns
The propeller usually rotates clockwise, as seen from the pilot's seat. The reaction
to the spinning propeller causes the aeroplane to rotate counterclockwise to the left.
This left turning tendency is called torque. The designer of the aeroplane
compensates for torque in cruising flight by building a slight right turning tendency
into the aeroplane. For example, the left wing may have a slightly greater angle of
incidence than the right wing. Aileron trim tabs also are used to compensate for
torque.
On take-off, torque affects directional control. Use of right rudder during the take-off
roll corrects this condition.
ASYMMETRIC THRUST
WHAT IS P-FACTOR? ASYMMETRIC THRUST AND LEFT TURNING
TENDENCIES EXPLAINED SIMPLY
https://www.youtube.com/watch?v=x9499KVu2kQ
WHAT IS P-FACTOR? | T HE ASYMMETRIC BLADE EFFECT
https://www.youtube.com/watch?v=zwd9I_fIVZc
Another left turning tendency is the result of asymmetric thrust, or P Factor. At high
angles of attack and high power settings, such as during take-off, the descending
blade of the propeller (on the pilot's right) has a greater angle of attack than the
ascending blade. This situation produces more lift from the right side of the
propeller with a consequent yawing to the left. Right rudder pressure compensates
for this tendency. Asymmetric thrust is significant only at high angles of attack. In
level flight, both blades of the propeller meet the relative airflow equally and
produce equal thrust.
On a twin-engine aircraft where both engines turn clockwise, losing the left engine is
more critical to flight than losing the right, as far as P Factor is concerned.
In a conventional twin, P-factor shifts both engine’s center-of-thrust to the right,
resulting in a significant left yawing tendency. The distance (arm) between the
center of thrust to the center of the aircraft's CG is greater on the right engine than
on the left engine. Therefore, a failure of the left engine will result in a more severe
yawing tendency than the failure of the right engine.
The asymmetrical disk loading (downward-moving blade) on the right engine
propeller, being further from the aircraft's C.G. than that for the left engine
propeller, gives greater leverage to the right engine. Such a resulting scenario
increases the aircraft's minimum single-engine control speed (V MC) when the left
engine is out.
With counter-rotating propellers, the left engine turns clockwise and the right turns
counterclockwise. The leverage effect is then minimized.
PRECESSION
The spinning propeller of an aeroplane acts like a gyroscope. One of the
characteristics of a gyroscope is rigidity in space; that is, the rotating gyro tends to
stay in the same plane of rotation and resists any change in that plane. If forced to
change, precession results.
If an aeroplane changes suddenly from a nose-up to a nosedown position, as is the
case during the take-off roll in a tailwheel aeroplane, the aeroplane will yaw sharply
to the left as the pilot shoves the wheel forward to raise the tail. The application of
right rudder compensates for the precession tendency.
Gyroscopic Effect on Aeroplane #flightclub
https://www.youtube.com/shorts/sPbJidqQ-to
SLIPSTREAM
The air pushed backward by a revolving propeller has a corkscrew motion. This
causes an increased pressure on one side of the tail unit and a decreased pressure
on the other side. The tail is consequently pushed sideways from the high pressure
side towards the low, causing the aeroplane to yaw. The condition is corrected by
offsetting the fin, or by offsetting the engine thrust line, or by fitting trim tabs on
the rudder, or by a combination of two or all of these methods. In some aeroplanes,
the rudder trim is adjustable by a control in the cockpit. In this way, the pilot is
better able to compensate for the changes in pressure on the rudder as the
aeroplane changes from climbing power, to cruise, to gliding.
The revolving slipstream from the propeller causes an aeroplane, especially
tailwheel aeroplanes, as the throttle is opened to commence the take-off roll, to yaw
to the left. As the airspeed increases, the tendency is less pronounced. Right rudder
compensates.
It may be of interest at this point to mention the relative effects of the slipstreams
of pusher and tractor type propellers. The tractor type of propeller located at the
nose of the aeroplane pushes high speed turbulent air back over the aeroplane,
thereby increasing considerably the drag of the fuselage and wing root sections. A
pusher type of propeller, located at the rear of the aeroplane, allows better high
speed performance due to the reduction of this drag. Because the tractor propeller
bites into “clean" air, its efficiency is good whereas the pusher propeller bites into
disturbed air. Nevertheless, from the standpoint of overall efficiency, the pusher
propeller configuration is considered to have more to offer in performance benefits.
CLIMBING
The engine produces the energy that keeps an aeroplane flying. The throttle
controls the output of this energy. It is the function of the elevators to divide the
energy, produced by the engine in the form of thrust, into speed and altitude. The
elevator does this by controlling the angle of attack of the wings. If, with no change
in the thrust, the angle of attack is decreased, less energy is required to maintain
the lift and more of the total energy output is utilized to produce an increase in
speed. If the angle of attack is increased, more energy is required to maintain lift
and less energy is available for speed. If the pilot puts some back pressure on the
control column (with no change in throttle setting), the aeroplane will climb and lose
airspeed. Conversely, if the pilot puts some forward pressure on the control column
(with no change in throttle setting), the aeroplane will descend and build up
airspeed.
During level flight, the engine must produce a thrust equal to the drag of the
aeroplane for the aeroplane to be in a state of equilibrium. If the power is increased,
the pilot can maintain level flight at an increased speed by putting the nose down
slightly (i.e. decreasing the angle of attack). If the pilot does not change the angle
of attack, the aeroplane will begin to climb as a result of the increased thrust, since
the increased speed of the relative airflow over the airfoil will produce more lift. By
adjusting power (i.e. choosing any setting between that needed for normal, straight-
and-level cruise and full power) and by varying the angle of attack, the pilot can
flatten or steepen the angle of climb and the airspeed in the climb.
Once established in a steady state of climb condition, the aeroplane is again in a
state of equilibrium. In the climb attitude, the aeroplane is inclined away from the
horizontal and, as a result, part of the weight acts rearward and combines with
drag. Thrust, therefore, equals drag plus a component of weight, and lift equals
weight less that component of weight that is acting rearward.
The ability of an aeroplane to climb is dependent on the extra power that is
available from the engine. At ever increasing altitudes, the density of the air
decreases and the power of the engine drops off. The climb, therefore, becomes
increasingly more shallow as greater altitudes are reached until further climbing is
impossible. The aeroplane has then reached its absolute ceiling.
Every aeroplane has a best rate of climb (V Y). This is the rate of climb which will
gain the most altitude in the least time. For every aeroplane there is an airspeed at
a given power setting which will give the best rate of climb. The best rate of climb is
normally used on take-off (after any obstacles are cleared) and is maintained until
the aeroplane leaves the traffic circuit.
The best angle of climb (V X) is the angle which will gain the most altitude in a given
distance. It is valuable in climbing out of restricted areas over obstacles. The
airspeed for the steepest angle of climb is somewhat lower than the speed at which
the best rate of climb is obtained. Because the airspeed for the best angle of climb
is relatively slow, there is less air circulating around the engine to provide cooling
and engine overheating is possible. The best angle of climb, therefore, should be
maintained only until obstacles are cleared and then the nose of the aeroplane
should be lowered to pick up the best rate of climb airspeed.
Every pilot should determine the airspeed for best rate of climb and for best angle
of climb for the particular aeroplane they are flying. These airspeeds are usually
given in the Pilot's Operating Handbook. However, it is necessary to bear in mind
that these speeds will vary according to the gross weight of the aeroplane.
The rate of climb is not affected by the wind, since it is a vertical measurement of
aeroplane performance and is not in any way related to groundspeed.
The angle of climb, on the other hand, is appreciably affected by the wind. When
climbing into wind, the aeroplane moves over the ground at a lower speed and
therefore takes longer to cover a given forward distance. The stronger the wind, the
slower the ground speed, the steeper the angle of climb.
Normal climb is a rate of climb that should be used in any prolonged cruise climb.
The airspeed for normal climb is always indicated on the Pilot's Operating
Handbook. It is a speed that is usually 5 to 10 knots faster than the airspeed for
best rate of climb and as such provides better engine cooling, easier control and
better visibility over the nose.
GLIDING
In gliding, there is no power from the engine and the aeroplane is under the
influence of gravity. Of the four forces, thrust is now absent and a state of
equilibrium must be maintained by lift, drag and weight only.
In Fig.2.37. Forces in a Glide, R represents the total reaction, i.e. resultant of lift and
drag. This is equal and opposite to weight.
The angle at which the pilot chooses to glide determines the airspeed in the glide.
The steeper the angle, the faster the airspeed; the shallower the angle, the slower
the airspeed. At too fast an airspeed, structural damage to the airframe could
result. At too slow an airspeed, the aeroplane could stall. The pilot must, therefore,
choose a gliding angle that maintains an airspeed that is sufficient to maintain flight
but not too fast to be unsafe.
When gliding with the power off, the aeroplane will tend to glide about 20% farther
if the propeller is stopped than if it is windmilling. The stopped propeller produces
drag that is equal only to the parasite drag of its configuration. The propeller that is
spinning acts as a windmill driving the engine, but without producing power. The
power required to rotate the propeller and consequently the engine of the aeroplane
is derived from the airflow and is about 10% of the rated power of the engine. The
energy required to drive the propeller that is not producing positive thrust is
therefore negative thrust or drag. Windmilling the propeller is like coasting an
automobile in gear. The windmilling propeller in a tractor engine configuration
directs disturbed air back over the lifting surfaces, inhibiting lift and creating drag.
When gliding with the engine off, an aircraft can glide approximately 20% farther if
the propeller is fully stopped compared to when it is windmilling. A stopped
propeller creates only parasite drag from its physical shape, while a windmilling
propeller consumes energy from the airflow to rotate both itself and the engine—
about 10% of the engine’s rated power—without producing any thrust. This results
in negative thrust, or drag. Additionally, in a tractor configuration (propeller at the
front), the spinning propeller disturbs the airflow over the wings, reducing lift and
increasing drag, much like coasting a car in gear.
Feathering Propellers:
Function: Feathering propellers allow the blades to be rotated to an angle
nearly parallel to the airflow (or water flow for boats), minimizing drag when
the engine is not providing power.
Use Cases:
Aircraft: Feathering is crucial in multi-engine aircraft for reducing drag from a
failed engine, improving performance and glide ratio.
Boats: Feathering propellers are used on sailboats to reduce drag when under
sail, allowing for better speed and fuel efficiency.
Advantages: Reduced drag in non-powered situations, improved gliding
distance for aircraft, better sailing performance, increased efficiency.
Disadvantages: More complex and expensive than non-feathering propellers,
require more maintenance.
Non-Feathering Propellers:
Function: Non-feathering propellers have fixed blades, meaning they maintain
the same angle to the airflow or water flow regardless of engine power.
feathering of propeller #aircraft #propeller
https://www.youtube.com/shorts/UaHM9MR0-Sc
Stopping a non-feathering propeller in flight should be done only in the event of an
engine failure when there is no chance of restarting the failed engine. The process
of raising the nose and stopping the propeller takes skill and should be attempted
only if you are confident of your ability to perform the procedure.
