multi flying in the DA42 Flashcards
What are the 3 assymetries when OEI
- lift
- drag
- thrust
what is the main control problem when OEI?
Yaw
what are the 3 factors affecting control OEI?
- speed
- drag on dead engine
- thrust on live engine
what are light twins not required to have by law in the event of an engine failure?
positive rate of climb
what is the purpose of a propellor?
to convert engine power into thrust
what is disc-ing?
when drag from the prop affects forward speed
what is the angle between the chord line and plane of rotation on a prop?
incidence angle
what is the angle between the chord line and the relative airflow?
angle of attack
what is the angle between the relative airflow and the plane of rotation?
angle of advance
what is propellor torque?
the combination of the drag vector and the lift opposed to the plane of rotation
where does lift act from the propellor?
at 90 degrees to the aerofoil. drag acts at 90 degrees to the lift
when will a propellor run at constant speed?
when propellor torque matches torque from the engine
what happens to AOA on a fixed pitch prop as forward speed increases?
AOA reduces
what is fixed on a fixed pitch prop?
angle of incidence
what is the most efficient prop AOA?
2-4 DEGREES
what happens to AOA as prop rotation speed increases?
AOA increases
what happens to a fixed pitch prop when the nose is raised?
RPM reduces because the AOA and propellor torque is increased
what happens to RPM as forward speed increases?
RPM increases as the torque reduces.
why is washout used?
speed of the propellor increases from root to tip. without washout the AOA and difference would lead to unbalanced lift and drag from root to tip
how does washout work?
chord length and thickness is reduced progressively from root to tip, to ensure equal thrust along the blade. the blade is coarse at the root and fine at the tip/
how will asymmetric blade effect make the aircraft yaw when pitched up?
the down going blade has further to travel meaning the RAF encountered is faster which increases the lift and thrust from the blade. this yaws the aircraft. (greater the angle of the prop axis from the horizontal, the greater the yaw)
what is the effect of aerodynamic moments on a prop?
aerodynamic moments create most lift from the base of the prop, forward of the centre of rotation. meaning it has a tendency to coarsen the blade. A negative AOA will cause the opposite effect (windmilling)
what is the effect of centrifugal force on a prop?
twisting moments about the centre of rotation that want to fine off the prop
what force is used to assist fining a prop on a VP propellor?
centrifugal force
what needs to be considered if full rudder deflection can’t be achieved?
a higher critical speed
on a multi-lever ME aircraft, how would we carry out a CSU RPM check?
with relatively high power, bring the rpm lever back until there is an RPM drop of about 200, the advance back to full RPM. do this 3 times, but not too far as to not overload the engine.
on multi lever ME aeroplanes, how would we carry out a feather check?
choose a low power setting then pull the RPM lever fully back to observe a large drop in rpm. do not hold the lever back for to long other wise the feathering locks may move into place.
on multi lever ME aeroplanes, why is the RPM pushed all the way forward for takeoff?
in order to allow maximum power without overloading the engine
what causes roll in asymmetric flight?
- loss of lift behind the failed engine
- secondary effect of yaw
- the failed side being lower than the live side, exacerbating the roll
where is the relative airflow from in uncorrected asymmetric flight?
the live side
what forces assist the pilot in asymmetric flight?
fin side force (lift) and fuselage drag
why do we bank into the live engine?
the lift vector is tilted to produce a sideways component of life to oppose the yaw. if banked too far the fin could stall however.
recite the standard control recovery for an engine failure
- rudder to prevent yaw
- aileron to level the wings
- pitch as necessary to maintain speed
what opposes the rudder force in stable asymmetric flight?
- fuselage sideforce
- yaw from asymmetric thrust
- drag from dead engine
why is the rudder less effective in stable asymmetric flight?
the RAF is on the dead side, meaning the angle of attack of the Raf acting on the rudder is less
what effect do leg/rudder forces have in stable asymmetric flight?
they increase the AOA of the fuselage in relation to the RAF, creating a greater drag force as the aircraft is pushed into the RAF. this further reduces the speed
how does power affect asymmetric flight?
the more thrust from the live engine, the greater the yawing moment will be towards the dead engine. rudder should be applied or reduced in line with power changes on the same side.
how do we check the yaw situation when maintain stable asymmetric flight?
the heading and slip ball
when is the rudder least effective?
high power/low IAS
what is critical speed? (Vmc)
the lowest speed at which multi-engine aeroplane at constant asymmetric thrust and at a particular configuration can be kept under control by a particular pilot
what are the conditions for Vmca?
- MTOM
- Max take off power
- critical engine windmilling
- most aft CG
- gear up, flap T/O
- 5 degrees bank into live engine
