Systems Flashcards
What are the conditions that certificated Vmc? 23.149
SMACFUM
Vmc certification requirements 23.149
S - Standard day at sea level
M - Max power w/ one engine opertating
A - Aft CG
C - Critical engine windmilling
F - Flaps up/gear up
U - Up to 5° bank
M - Most unfavorable weight
S - Standard day at sea level
air is more dense, allowing for engine to perform better, increasing thrust, causing a greater force toward the dead engine, requiring more rudder to overcome that force.
(BAD for VMC)
M - Max power w/ one engine opertating
Max power means more performance & more yaw towards inoperative engine. This requires more rudder input, to counteract yaw. This increases VMC, which is bad b/c we want to maintain control at lowest speeds
(BAD for VMC)
A - Aft CG
Aft CG means less arm, less arm means less leverage for rudder to counteract yaw. Less rudder authority means VMC increases.
(BAD for VMC)
C - Critical engine windmilling
Critical engine windmilling causes more drag than if it was feathered. More drag on the inoperative engine means more yaw toward the inop engine. Therefore more rudder is needed to counteract this yaw. Therefore VMC increases
(BAD for VMC)
F - Flaps up/gear up
Flaps up/Gear up means less drag, which you would think is good for VMC, but really it is bad for VMC. Flaps help stabilize a/c and reduce stalling speeds. Gear down gives the a/c a
“keel effect”, which helps keep it straight, just like a kayak in the water. Therefore flaps up & gear up negatively affects our vmc speed
(BAD for VMC)
U - Up to 5° bank
provides a zero side slip condition, a/c creates less drag when banked into the operative engine.
(split the ball and bank 5° into operating engine). This brings VMC down which is GOOD
(GOOD for VMC)
M - Most unfavorable weight
Vmc increases as weight decreases, therefore the lightest legal weight is unfavorable.
(BAD for VMC)
What is the critical engine?
the engine that if failed, would cause the most trouble to the pilot. The engine that if failed, adversely affects the aircraft the most. For a conventional twin, the LEFT is the most critical.
What is the critical engine for the C-130H?
The furthest LEFT engine
PAST: Understanding which engine is critical and understand which engine creates the most adverse effect and why.
P - P factor (yaw)
A - Accelerated Slipstream (roll)
S - Spiraling Slipstream (yaw)
T - Torque (roll)
P - P factor
failure of the left engine will cause MORE loss of directional control, than the loss of the right engine b/c of the LONGER ARM of the right (operative) engines arm’s thrust causing a/c to yaw.
A - Accelerated Slipstream
propwash from the descending blade going over the wing results in lift, causing a/c to roll; bigger roll from right engine.
S - Spiraling Slipstream (yaw)
Descending blade causes more thrustin turn causing LOW PRESSURE,
Ascending blade causes high pressure; High pressure always wants to go to low pressure.
Spiraling slipstream goes towards the right b/c high to low pressure.
Spiraling slipstream on the left engine contacts the rudder which gives us more rudder authority,
counteracting yaw towards inoperative engine.
T - Torque (roll)
Newton’s third law: for every action, there is an equal and opposite reaction.
If the right engine fails, this left roll tendency will help us maintain control and resist the roll towards the right, inoperative engine, caused by asymmetric thrust. If the left engine fails, the left roll tendency by torque will add to the left turning force caused by asymmetric thrust into the inoperative engine. This makes it much more difficult to maintain directional control, making the left engine the critical engine.
PA 44-180 Seminole Engine (LHAND)
L - Lycoming (O-360, 4 cylinder, 360 cubic inch)
H - Horizontally opposed (pistons oppose each other)
A - Air cooled
N - Normally Aspirated (No turbo or supercharger)
D - Direct Drive (crank shaft connected directly to the propeller)
When does Carburetor Icing occur?
1) Visible moisture (clouds)
2) -5° to 20° C or (20° to 70° F)
What causes carburetor icing and what is the solution?
Cause = high air velocity through the venturi and the absorption of the heat from this air by vaporization of the fuel
Solution = turn on carburetor heat and adjust mixture for maximum smoothness
What is propeller underspeed?
when climbing, if you don’t adjust your engine controls, and you pitch the airplane up, your engine has to work harder and it will start to slow down. This situation is called underspeed.
But you’re airplane is smart. As soon as this happens, the flyweights begin to wall inward b/c they slow down as well. When this happens, the pilot valve moves down and oil flows out of the propeller hub, reducing the pitch of the blades.
What is propeller overspeed?
When you pitch the airplane down, the governor takes over again. By pitching down and not touching the engine controls, the engine will start to speed up, and the flyweights will fly outward, due to centrifugal force. As soon as that happens, the pilot valve will raise, oil will flow into the prop hub, and the pitch of the blades will increase, slowing the engine to your set speed.
What happens when you go FULL FWD on the Blue prop lever?
For example when you’re coming in to land
Low pitch/High RPM setting
By moving the lever forward,it turns the screw to the right and increases the pressure on the speeder spring, thus causing the flyweights to fall in and raise the pilot valve, allowing oil to escape the prop hub and go back into the sump, allowing prop to go into the low pitch/High RPM setting.
Practically, you give yourself more ‘instantaneous’ power, because the engine doesn’t need to work as hard to turn the prop, it takes smaller “bites” of air. That’s something that’s useful if you need to go-around.
What happens when you bring the the Blue prop lever aft?
For example when you’re at cruise altitude prop goes to 2300 rpm
High pitch/Low RPM setting
When you bring the prop lever aft, the screw will turn left, releasing tension on the speeder spring. This will cause the flyweights to fly out b/c of the less spring tension, lifting the valve and pumping oil into the prop hub, allowing prop to go into the High pitch/Low RPM setting
Practically, you adjust to prop to take a bigger ‘bite’ of air, in turn, increasing the torque required of the engine to swing the prop around.
With that increase in torque, the engine slows down, which in cruise flight is a good thing. It means your engine isn’t spinning as fast, your fuel efficiency is increased, and the engine parts won’t wear down as quickly. Think of it kind of like switching to a higher gear on your bike. You need to push a little harder with your legs, but you don’t need to pedal nearly as fast.
PA-44-180 Fuel diagram
PA44-180 Electrical System
How does the vacuum system work?
Outside air is brought in through the filter, passes through the gyroscopic instruments, passes through the manifold check valve (pressure is measured at this time w/ the vac indicator), then moves down through the regulator (if pump is pulling too much suction, regulator will pull in air to keep pressure at 4.8-5.2” Hg), then through the pump and out.
