Midterm Flashcards
How much brake horsepower is converted to thrust horsepower?
85%
How much can propeller efficiency vary by?
50-87%
What factors does the amount of thrust depend on?
- angle of attack
- speed
- shape of airfoil
- propeller efficiency
How are propellers classified?
-according to position on aircraft and pitch
What is mach 0.87?
565 knots
What is mach 0.85?
prop efficiency begins to decrease dramatically when tip velocity approaches or exceeds this
Explain thrust bending force
- caused by thrust loads
- compression and tension acting upon blades
- bends blades forward in line of flight
Where do blades try and stay in the centrifugal twisting moment?
-try to stay in parallel rotation to the propeller plane of rotation
What 3 forces cause the propeller to vibrate when a propeller is connected to an engine
- thrust
- aerodynamic
- mechanical
What is the resonant frequency?
The frequency of which the system will vibrate if it is excited by a single pulse
What are the hardwoods used to manufacture aircraft propellers?
- birch
- ash
- maple
- cherry
- oak
- black walnut
In wooden propellers, all types and laminations must be free of
- grain irregularities
- knots
- air pockets
- Insect damage
How many layers are wooden propellers fabricated from?
5-10
What do laminated layers glued together form?
blank
the rough cut and allowed to season
Dimensions, pitch and shape are milled from the laminated wood using
airfoil jigs and blade station measurements
In some cases the last —- inches of the blade has a fabric covering to reinforce the thinner section of the propeller tip
12-15
What is applied to wooden propellers to prevent moisture ingress?
Clear water proof varnish
What colour paint is used on the tip of wooden propellers?
Red or white
In model number 70D42, what is 42?
Geometric pitch as 75% radius station
Which direction are wooden propellers stored?
horizontally
for even moisture distribution - prevents warping
Aluminum round tip
- large arc
- no advantage for tip disturbances
aluminum Square/klip tip
- shorter than round
- lower rpm, quieter
aluminum Scimitar sweptback
- reduces tip vortices
- higher speed
aluminum q tip
- 90 degree bend at tip towards face
- quieter
- reduces tip vortices
What are the three mount types of aluminum propellers
- splined shaft
- tapered
- flange
Aluminum propellers Field Repair of Aircraft Propellers Part _ Standard _ Appendix _
Part 5 Standard 571 Appendix D
How are aluminum propellers balanced?
Vertically and horizontally
When you paint an aluminum propeller, what does the paint further protect it from?
corrosion and FOD
What materials can be used in composite?
- core of wood, honeycomb or rigid foam and reinforcing shank
- fiberglass or carbon fibre and aramid fibre
In composite propellers, wear occurs from what?
- high rpm in rain or sandy areas
- fod on taxis and runways
- delamination when damage is left unrepaired which allows moisture to enter
How are composite propellers balanced (direction)?
Statically in the horizontal plane
How (method) are composite propellers balanced?
-by adding lead wool to centrally located balance tube in metal blade shank
On a composite propeller, what does a finish covering of polyurethane paint protect the blade against?
erosion and uv damage
What is the constant speed range of a constant speed propeller determined by?
the high and low pitch stops
For constant speed propellers, the throttle can be placed anywhere between the min and max setting based on the required ——-
manifold pressure
What are the 3 main functions of the governor?
- boosts engine oil pressure
- senses rotational speed of engine
- controls the amount of oil to the propeller hub
Engine oil is boosted in the governor by an _____ which is geared to the engine
integral gear type pump
What is the normal engine oil pressure and what does it increase to?
normal 60, increase to 180 to 300
What is the name of the thing that senses engine speed in constant speed propeller>
propeller governor
The propeller governor oil is controlled by the _____
pilot valve
The governor is operated by the pilot with the ______ in the flight deck
propeller lever
A combination of ___ and ____ in the hub allowed the propeller to maintain a constant speed for constant speed propeller
speeder spring and oil pressure
THe ____ regulates the flow of oil based on the position of the flyweights
governor
There is a failsafe incorporated into the governor in the form of a
return spring
What is the RPM time for initial climb
the time to bring the rpm back from peak to around max continuous rpm
