17.3 PROPELLER PITCH CONTROL Flashcards
Moving cylinder applications are generally used on what type of aircraft
Small aircraft propellers
Explain disc braking
- Propellers move blades to a very fine pitch
- causes negative AOA and then braking force
-(like engine braking)
Explain single acting propellers for single engine
- Oil pressure moves to high (coarse pitch)
- Spring moves to low (fine pitch)
In the event for engine shutdown for single acting propeller for single engine aircraft what blade angle is used
Put it at low blade angle
In single acting propeller used on multi engine aircraft
- Oil pressure moves blades in direction of low (fine) pitch
- spring moves to high (coarse) pitch
In single acting propeller used on multi engine aircraft
- Oil pressure moves blades in direction of low (fine) pitch
In single acting propeller for multi engine aircraft what happens if engine failure
Blades move in high (coarse) pitch
What is double acting propellers
Oil pressure leads to pitch change in both directions
What is a propeller governor
Engine RPM sensing device and high pressure oil pump
What is fitted at the top of governor so in the event of a control lever failure
Safety spring
What does the manual feathering system consist of
- feathering pump
- reservoir
- feathering time-delay switch
- propeller feathering light
How does manual feathering work
- moving the control in the cockpit against low-speed stop
How is manual feathering accomplished
- by pulling engine emergency shutdown handle
- switch to shutdown position
What is automatic (auto-coarsening) feathering
- provides automatic operation during take off and cruise
In automatic (auto-coarsening) feathering what occurs in the event of an engine failure
Centrifugal flyweights are automatically overridden and electric feathering pump runs
What is up trim
When one engine loses power, other engine compensates and increases power by 10%
Up trim is triggered when
- torque of local engine falls below 25%
- rotational speed indicated by torque sensor falls below 80%
When is a unfeathering accumulator used
Provide a reserve of pressure
What is the primary propeller also known as
Constant speed unit
Constant speed unit (propeller governor) works to control any propeller over speed up to approx
102%-103%
If propeller speed exceeds value from approx 104 to 106%, propeller over speed governor operates and returns oil from propeller dome back into reduction gearbox
True
