What is the purpose of counterweights in aircraft?
Counterweights are used to balance control surfaces about the axis of the hinge to avoid potentially dangerous control flutter. This balance is very important. Pilots typically check for counterweight structural security in preflight where able.
What are counterweights used for in piston engines?
Counterweights are used in piston engines for both static and dynamic balancing. Excessive vibration in an engine not only results in fatigue failure of the metal structures, but also causes the moving parts to wear rapidly. In some instances, excessive vibration is caused by a crankshaft which is not balanced.
What is a constant speed propeller used for?
A constant speed propeller is a propeller that is designed to automatically change its blade pitch to allow it to maintain a constant RPM, irrespective of the amount of engine torque being produced or the airspeed or altitude at which the aircraft is flying. How does a propeller feather?
What is the purpose of a propeller in an airplane?
But the purpose of an airplane propeller is to make more or less thrust (driving force) at different points of a flight (during takeoff, for example, or steady cruising). The angle of a propeller's blades and its overall size and shape affect the thrust, and so too does the speed of the engine.
How do counterweight propellers increase blade angle?
The hydraulic counterweight propeller consists of a hub assembly, blade assembly, cylinder assembly, and counterweight assembly. The counterweight assembly on the propeller is attached to the blades and moves with them. The centrifugal forces obtained from rotating counterweights move the blades to high angle setting.
What do the flyweights do in the prop governor?
Flyweight force exceeds governor spring force, lifting the pilot valve and allowing high-pressure oil to enter the propeller. This increases the propeller pitch and brings the engine rpm back to the selected value. As engine and governor rpm decrease the governor returns to the ON SPEED condition.
Why do we need to synchronize the propellers?
Propeller synchronization serves mainly to increase the comfort of crew and passengers, since its primary purpose is to reduce the “beats” generated by propellers that are turning at slightly different speeds. These beats can become very irritating to persons inside the aircraft after a time.
What happens when you feather a propeller?
The inflight feathering of the propeller, on an engine that has failed or has been intentionally shut down, greatly reduces the drag that would occur with the blade pitch in any other position.
How do flyweights work?
The "L" shaped flyweights, which spin around in a circle, are connected to the engine through gears. They're also connected to the pilot valve, which they move up and down. When the engine speeds up, the weights spin faster and fly out due to centrifugal force, lifting the pilot valve up.
What is the purpose of the governor pilot valve?
[Figure 7-16] It consists of a gear pump to increase the pressure of the engine oil, a pilot valve controlled by flyweights in the governor to control the flow of oil through the governor to and away from the propeller, and a relief valve system that regulates the operating oil pressures in the governor.
When should I turn on my prop sync?
The prop sync should always be off for takeoff, landing, and single-engine operation. The AFM/POH should be consulted for system description and limitations. A variation on the propeller synchronizer is the propeller synchrophaser.
What is synchronizing and Synchrophasing?
Synchrophasing allows the pilot to adjust the phase angle between the propeller on the various engines to reduce the noise and keep vibration to a minimum.
How do you balance a propeller?
0:596:48How To Balance A 2-Blade Propeller | Quick Tip | Motion RC - YouTubeYouTubeStart of suggested clipEnd of suggested clipAll the way you're going to place your prop. And you want to center that as best you can. And thenMoreAll the way you're going to place your prop. And you want to center that as best you can. And then just screw this back on. And it just thumb tightens. But once you get there you'll see.
What is the purpose of small holes at the tip of wooden propellers?
Since moisture condenses on the tipping between the metal and the wood, the tipping is provided with small holes near the blade tip to allow this moisture to drain away or be thrown out by centrifugal force. It is important that these drain holes be kept open at all times.
How do feathering propellers work?
Feathering propellers have a mechanism to change the pitch to an angle of approximately 90 degrees. Usually, a propeller is feathered when the engine fails to produce the power needed to turn the propeller. By angling the propeller parallel to the direction of flight, the drag on the aircraft reduces.
Why is a propeller blade twisted?
Propeller Design There is a twist along the length of a propeller blade because the blade speed is much higher at the tip than it is at the root. The twist is necessary to maintain a more or less constant angle of attack along the length of the blade.
Why are counterweights used in propellers?
Counterweights are used in some constant speed propeller designs to increase the pitch of the propeller blades. Engine oil pressure is used to overcome the force of the counterweights to move the propeller blades back to fine pitch.
Why do manufacturers use counterweights?
Why is the use of weight necessary? Supposedly aircraft should be made as light as possible, and counterweight is just dead weight without any function.
What is ballast used for?
Both concepts involve mass used to balance, dampen, or adjust forces about a rotational axis. While ballast could also be described as a type of counterweight, it is best understood as working within the frame of reference of the entire aircraft since it adjusts the aircraft Center of Gravity (CG). Conversely, counterweights can be understood to work within a frame of reference that is smaller than the aircraft as a whole, such as an engine or a control surface.
How does centrifugal force affect propeller blades?
The centrifugal force, due to rotation of the propeller tends to move the counterweights into the plane of rotation, thereby increasing the pitch of the blades.
How does a governor feather work?
This is done by pulling the governor pitch control back to the limit of its travel. which opens up a port in the governor allowing the oil from the propeller to drain back into the engine. The time necessary to feather depends upon the size of the oil passage from the propeller to the engine, and the force exerted by the spring and counterweights.
What is ballast in aviation?
While ballast could also be described as a type of counterweight, it is best understood as working within the frame of reference of the entire aircraft since it adjusts the aircraft Center of Gravity (CG).
Why use counter weights in flight controls?
2. Counter Weights are used to provide offset forces in the flight controls. This provides controls with better "feel" and "feedback" forces as well as reducing the required pressure to move the controls. This is also done with "tabs" that use air pressure for the similar reasons.
What position is propeller control?
For maximum takeoff power, the propeller control is moved all the way forward to the low pitch/high r.p.m. position, and the throttle is moved forward to the maximum allowable manifold pressure position
Why is a propeller more efficient than other propellers?
More efficient than other propellers because it allows selection of the most efficient engine RPM for the given conditions
What is the tachometer on a propeller?
In a fixed-pitch propeller, the tachometer is the indicator of engine power [ Figure 2] Calibrated in hundreds of RPM giving a direct indication of the engine and propeller RPM. The RPM is regulated by the throttle, which controls the fuel/air flow to the engine.
How do propellers change pitch?
On some constant-speed propellers, changes in pitch are obtained by the use of an inherent centrifugal twisting moment of the blades that tends to flatten the blades toward low pitch, and oil pressure applied to a hydraulic piston connected to the propeller blades which moves them toward high pitch
How to reduce power for climb or cruise?
To reduce power for climb or cruise, manifold pressure is reduced to the desired value with the throttle, and the engine r.p.m. is reduced by moving the propeller control back toward the high pitch/low r.p.m. position until the desired r.p.m. is observed on the tachometer.
What is an adjustable pitch propeller?
The adjustable-pitch propeller was the forerunner of the constant-speed propeller. It is a propeller with blades whose pitch can be adjusted on the ground with the engine not running, but which cannot be adjusted in flight. It is also referred to as a ground adjustable propeller.
When the forward motion of an airplane is at low speeds and when maximum power and thrust are required, what is the answer?
During takeoff, when the forward motion of the airplane is at low speeds and when maximum power and thrust are required, the constant-speed propeller sets up a low propeller blade angle (pitch)
What are the indicators on propellers?
These indicators may include individual channel fail indicators, dual channel fail indicators, and/or maintenance indicators. Specific flight crew procedures based on these different indicators vary widely across the various fleets equipped with electronically-controlled propellers. Refer to the AFM and manufacturer recommendations for specific configuration and procedural information. Loss of the operation of a single channel in these systems typically does not limit the operation of the propeller system during flight, landing or ground handling.
How does a propeller speed sensing governor work?
Propellers have a speed-sensing governor that controls oil pressure on a piston attached to the blades by a mechanical linkage. If the pilot commands a change in propeller RPM, or if flight conditions (engine power or airspeed) change, the propeller speed-sensing governor adjusts the oil pressure, changing the pitch of the blades. It does this to maintain the speed of the propeller as set by the pilot. If the propeller is turning too quickly, the blade pitch is automatically changed to take a bigger bite out of the air, creating more torque and slowing the propeller RPM. If the prop is turning too slowly, the blade angle is decreased to take smaller bites, producing less torque and allowing propeller RPM to speed up. The speed-sensing governor continually adjusts the oil pressure to keep the propeller at the commanded RPM at constant speed.
What happens when an airplane's pitch is changed?
While the pitch is changing, the thrust may increase and then decrease rapidly. The airplane will have asymmetric thrust. The pilot will need to control the airplane and then shut down the engine. The high torque may cause engine and propeller damage, but it will not, if properly handled, cause loss of control of the airplane.
What happens if a propeller governor fails?
Failure of the main propeller governor will result in the activation of the propeller overspeed governor. The NP gage will typically be steady at 103 to 105%. The noise in the cabin will be increased because the RPM is higher than normal and the synchronizer/syncrophaser will not be functioning (because the other propeller is turning at a normal RPM). The RPM will not decrease or increase when commanded by the condition lever or a speed-selection device. Operating on the overspeed governor typically means that reverse thrust operation is not available, although flat-pitch operation on the ground may be available. Each installation is different, and the AFM instructions should be used.
What happens if a propeller surges?
Depending on the severity of the surge, there may be insufficient time for the propeller system to react to the event. If the event is prolonged, a drop in propeller torque might be observed. If the engine does not recover, the propeller will react as in the flameout case, and may require similar action.
What is feathering in aviation?
In feathering, the blades are turned so that the leading edges are pointed essentially in the direction of flight. In this position, the aerodynamic forces on the propeller result in a low drag condition.
How to maintain constant speed?
To maintain constant propeller RPM, you must adjust the pitch of the propeller blades as you change airspeed and/or engine power. The pitch is adjusted by rotating the whole blade on a bearing in the hub using an actuator that is linked to the control system. When you change the pitch, you change the "bite" that the blades make with the wind. This, in turn, increases or decreases the aerodynamic load on the propeller.
What is a hydraulically controlled propeller?
A powerplant using a hydraulically controlled constant-speed propeller is operating within the propeller's constant-speed range at a fixed throttle setting. If the tension of the propeller governor control spring (speeder spring) is reduced by movement of the cockpit propeller control, the propeller blade angle will.
What is grease used for in propellers?
11. Grease used in aircraft propellers reduces the frictional resistance of moving parts and is easily molded into any form under pressure. This statement defines
What is propeller synchrophasing?
9. A propeller synchrophasing system allows a pilot to reduce noise and vibration by
What is the flat side of a propeller called?
The flat side of the propeller is called. Blade edge. The angle between quarter of a plane and the plane of rotation is called. Blade angle. The force that tries to been the proper blade in the opposite direction as the direction of rotation is called.
Where are propellers mounted on a conventional airplane?
Propellers mounted on the front of the driveshaft of a conventional airplane are. Tractor propellers. Why are pusher type propellers often mounted above and behind the wings. To prevent damage to the prop from the wheels throwing Debris. Which is the most common would use and propeller construction. Birch.
What is the critical operating range of an aircraft propeller engine?
What is meant by the "critical operating range" of an aircraft propeller engine combination. The range at which vibrations are the most and you can only stay in the range long enough to pass through it. The angle at which the relative when strikes the propeller blade is called. Angle of attack.
What is the force that tries to decrease blade angle called?
Aerodynamic twisting moment. The force that tries to decrease blade angle is called. Centrifuge twisting moment. What would be the result of allowing the aerodynamic and mechanical forces which causes a propeller blade to vibrate to go uncontrolled.