17.2* Flashcards
What do wooden propellers consist off?
Several (at least 5) layers of wood bonded with a waterproof resin glue - aero glue
What is the most common wood used?
Birth
What is the minimum amount of layers of wood to be laid down?
5 layers
On wooden props a cotton fabric sheathing is applied where?
To 12-15 inches of the outer tip to reinforce the strength of the tip
In a composite prop where is the heating boot?
On the inner 1/3;
On a composite prop what is the surface protected by?
By a coat of conducting polyurethane paint that protects against erosion and prevents the blade from becoming statically charged
On a composite props what is bonded to the leading edges?
Nickel or stainless steel erosion shields to protect from damage
What type of aircraft are metal propellers used on?
Engines with greater engine power
What are metal props constructed from?
Aluminium alloy or steel
What is the construction of steel blades normally, and what is the advantage of this?
Steel blades are normally on a hollow construction and foam filled
. This reduces the weight
What is the most common finishing process used in metal props?
Anodising
How can you measure the propeller master reference station?
A distance measured from the centre of rotation where all measurements are taken from
Where is the master reference point on a fixed pitch prop?
75% from the centre of rotation
Where is the master reference point on a variable pitch prop?
50- 75% from the centre of rotation
What is the propeller blade angle?
The angle between the blade chord line and the plane of rotation
What is the propeller face?
The flat thrust producing side of blade
What is the propeller back?
The curved side of blade facing the flight
What is the propeller base butt?
The base of prop blade where root ends
Can you change the pitch on a fixed pitch prop?
No
What power and speeds are fixed pitch props used in?
200kW (250hp) and region of 250km/h (160mph)
For a fixed prop blade, the blade angle is set for its intended purpose. When would you need a fine vs coarse blade angle?
. Fine (low) = steep clim and towing
. Coarse (high) = cruising flight
On a fixed pitch prop, when is maximum RPM a viable?
When the angle of attack is set too it’s optimum 4 degrees
What are ground adjustable propellers designed for?
. Used on older aircraft of low - moderate performance. Blade angles can be adjusted on the ground to give the desired performance
. Take off - low/fine
. Cruise - high/coarse
What is the angle range of ground adjustable props?
7-15 degrees
