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Propellers
O&P(P)
| Question | Answer |
|---|---|
| Why do some aircraft engines have a critical range of operation | The engine and prop combination have a resonant frequency problem in which excessive vibration can occur in a certain range of RPM. The tach for an aircraft with this limitation is marked with a red arc. When necessary to pass through must be done quickly |
| Does centrifugal twisting moment on a prop blade tend to move the blades toward high pitch or toward low pitch | Toward low pitch |
| Do the counterweights on a propeller tend to move the blades toward high pitch or toward low pitch | Toward high pitch |
| What is the function of the accumulator used with some McCauley feathering props | The accumulator stores oil under pressure when the engine is operating normally. This oil is used to help the propeller blades move toward low pitch when the propeller is being unfeathered |
| What is meant by the alpha range of operation of a turboprop propeller | This is the in-flight mode of operation from takeoff to landing |
| Should an adjustable pitch prop be in high pitch or in low pitch for takeoff | In low pitch |
| What can be done to prevent the front cone from bottoming when installing a prop on a splined shaft | Install a spacer behind the rear cone to move the prop forward on the shaft |
| Why is a prop indexed to the engine cramkshaft | The relationship between the prop and engine crankshaft is chosen to produce the minimum vibration |
| What is the function of the snap ring inside the hub of a propeller that is mounted on a tapered or spline shaft | The snap ring allows the propeller to be pulled off of the shaft when the retaining nut is backed off |
| What materials are propeller blades made from | Wood, aluminum, composite construction |
| What are the basic types of propellers | Fixed pitch, ground adjustable, constant-speed non-feathering, and constant-speed feathering |
| What is adjusted inside the governor for a constant-speed propeller to change the speed at which the propeller is operating | The compression of the speeder spring |
| What is done to cause a McCauley propeller to feather | Oil is allowed to drain out of the propeller |
| What keeps a McCauley feathering propeller from feathering when the engine is shut down on the ground | A spring loaded latch mechanism prevents the blades moving into the feather position when the engine is shut down |
| What is done to cause a hydromatic propeller to feather | High pressure engine oil is directed into the propeller through the governor |
| What does the pilot do to change the RPM of an equipped with a constant-speed propeller when it is operating within constant speed range? | The pilot moves the prop pitch control. This changes the compression on the speeder spring inside the governor which moves the pilot valve. The change in pitch change the air load on prop which changes RPM |
| What is the difference between a controllable propeller and a constant-speed propeller? | A controllable pitch propeller uses a manually operated oil valve to control the pitch, And a constant speed propeller uses a governor to control the valve |
| When making a magneto check on an engine equipped with a constant speed propeller, should the propeller control be in the low pitch or the high pitch position? | It should be in the low-pitch, high RPM position |
| What is meant by the beta range of operation of a turboprop propeller | This is the mode of ground operation, and it includes starting, taxiing, and ground reverse operation |
| What controls the blade angle of a propeller when operating in the beta range | When operating in the beta range, blade angle is controlled by the position of the power lever |
| Where do you find a list of the lubricants that are approved for use in a constant speed propeller? | In the maintenance manual for the propeller |
| What is the extent of the repairs a mechanic with a Powerplant rating can make to a propeller? | Only minor repairs or minor alterations |
| Where can examples of acceptable repairs to aluminum alloy propeller blades be found? | In AC 43.13-1B, Chapter 8, Section 4, and in the propeller manufacturer's service manuals |
| Is it permissible to cold straighten a damaged aluminum alloy propeller blade to facilitate shipping is to a repair station? | No, this could cause hidden damage that may render the blade nonrepairable |
| What would be classification of maintenance for shortening a propeller blade? | Major repair |
| May transverse cracks in a metal propeller blade be repaired? | No, transverse crack of any size is reason for rejecting the blade |
| What damage to an aluminum alloy propeller blade can be repaired by mechanic holding a Powerplant rating? | Small roughness, nicks, and scratches in the leading edge of the blades |
| How are small nicks removed from the leading edge of a propeller blade? | File them out with a fine file or stone, leaving a smooth contour. |
| How can you determine that a surface scratch in an aluminum alloy propeller blade is not actually a crack? | Clean crack, then spray with dye-penetrant. Allow time to seep into cracks if any, then wipe all of the liquid off the surface. Spray area with developer, If the damage is actually a crack, the developer will pull the penetrant out and will form a line. |
| Who, or what facility, is authorized to perform major repairs to a propeller? | An FAA- approved propeller repair station that is authorized for the specific propeller |
| What checks and maintenance is a mechanic with a Powerplant rating allowed to make on a propeller? | -Check the track of the propeller blades -Remove small nicks and scratches from the blades -Check the dynamic balance of a propeller -Lubricate the propeller |
| What adjustment can a mechanic with a Powerplant rating make to a propeller governor? | Adjust the maximum RPM stop |
| What instrument is used to measure the blade angle of a propeller? | A universal propeller protractor |
| Where is the propeller protractor placed to measure the propeller blade angle? | At a distance from the center of the propeller hub. The distance is specified in the propeller maintenance manual in terms of propeller blade stations. |
| What are the basic steps of removing a typical propeller | - Remove spinner and remove safety wire from mounting bolts - Support prop with a sling and mark alignment between prop and engine flange - Unscrew mounting nuts and protect threads of studs - Place prop on cart for transport |
| What alignment method is used to align a propeller to the engine in a position that reduces operating vibrations | Special studs or dowel pins align the propeller to the engine in the proper orientation |
| Who is allowed to reduce the diameter of a type certificated propeller | An FAA- certificated propeller repair station with approval for the particular propeller |
| Which type certificate data sheets (aircraft, engine, or propeller TCDS) specifies that a propeller can be installed on the aircraft in question | The aircraft TCDS specifies which propellers are approved for installation |
| What is meant by a slave engine with regard to propeller synchronization | This is the engine in a multi-engine airplane whose RPMs follow those set on the master engine |
| How are propellers on a twin engine airplane synchronized | The prop gov of the master engine is set to a desired RPM. A signal from the engine gov is sent to the control box which sends a signal to a stepping motor. The motor adjusts the prop gov and fuel control of the slave engine causing it maintain exact RPM |
| How is ice prevented from forming on propeller blades | A chemical anti icing system is used. A mixture of isopropyl alcohol and ethylene glycol is pumped into a slinger ring on the back of the prop hub. From the centrifugal force slings it out along the blades. Ice cannot form on the resulting slick surface |
| How is ice removed from propeller blades | An electrical heating elements are embedded in rubber boots that are bonded to the leading edges of the blades. Low voltage DC flows from the prop deicer control through brushes and slip rings of the heating elements. |
| How can you determine that the electrically heated deicer boots on the propeller blades are working as they should | Observe the loadmeter or ammeter to see if the proper current is flowing, and follow the sequence of boot heating by feeling with your hands to see which one is heating. The boots should all have a similar heat rise in the same length of time |
Created by:
tbarth
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