Preflight Preparation Flashcards
Why is having good systems knowledge essential for pilots?
In order to troubleshoot effectively in the event of a system malfunction or failure. The stakes are high when things break in airplanes. In a car you can just pull over to the side of the road - you can’t pull over to the side of the sky, though.
What are your aircraft’s primary and secondary flight controls?
Primary: ailerons, rudder, elevator. Secondary: flaps, trim.
How are the yoke and rudder pedals linked to their associated flight control surfaces?
Through cables, pulleys, bellcranks, and pushrods.
When you turn the yoke to the left, which direction does each aileron move?
Left aileron up, right down.
When you turn the yoke to the left, aerodynamically, how does this cause the plane to roll left?
The right aileron that drops has the effect of increasing its wing’s camber, thus increasing the speed of the airflow over the top of its wing and increasing lift. The left wing’s aileron goes up, decreasing camber, decreasing lift.
Around what axis does the airplane roll?
Longitudinal.
What type of ailerons does your plane have?
Differential, frise.
Describe the purpose and function of each of those features.
Differentia l ailerons counteract adverse yaw. During a turn to the left, the right wing creates more lift and rises, but it also creates more induced drag, causing the nose of the airplane to yaw away from the direction of the turn toward the raised wing. To negate this, the left wing’s aileron sticks up high (higher than the right wing aileron’s downward deflection) in order to create additional parasite drag and help the plane yaw properly in the direction of the turn. Further helping to counteract this adverse yaw is the frise feature of the ailerons. Sticking with the left-turn scenario, when the trailing edge of the left wing’s aileron goes up, the leading edge of that aileron deflects downward below the wing in order to create additional drag and prevent the plane from yawing in the opposite direction. The frise feature also allows airflow beneath the wing to join and re-energize the airflow on the top surface of the aileron in order to increase its effectiveness (same idea behind slotted flaps).
What type of horizontal tail surface does your plane have?
Elevator (attached to the back of the fixed horizontal stabilizer).
How is this different from a stabilator?
With a stabilator, the entire horizontal tail surface moves as one slab, pivoting from a central hinge point (like on the PA44).
When you pull the yoke back/pitch up, which direction does the trailing edge of the elevator deflect?
up
Aerodynamically, how does pulling the yoke up cause the plane to pitch up?
When the trailing edge deflects upward, it sticks up into the relative wind, pushing the tail of the airplane down, raising the nose into a pitch-up attitude. Also, when the trailing edge deflects upward, more camber is created on the bottom of the horizontal tail surface, generating more negative lift to push the tail down and the nose up.
Around what axis does the airplane pitch?
Lateral.
When you step on the left rudder pedal, which direction does the trailing edge of the rudder surface deflect, and what effect does this have on the plane’s orientation? Why?
The rudder surface deflects to the left and the plane yaws to the left. The rudder is like a wing
on its side - when it deflects to the left, the camber on the right side is increased, accelerating air faster over that side, increasing the rightward horizontal lift produced by the rudder, causing the tail to swing right and the nose left. In addition, when the rudder deflects to the left, the relative wind strikes it, pushing the tail to the right and the nose left.
What function(s) does the rudder serve?
Primarily the rudder exists to counteract adverse yaw (slips), as well as to counter any unwanted yaw tendencies, such as the left-turning tendencies. The rudder is also used to intentionally create more parasite drag during forward slips to land, to maintain longitudinal alignment during crosswind landings, and to help maintain directional control after engine failures in multi-engine airplanes. Lastly, the rudder can be used to turn the airplane in the event that the ailerons malfunction.
Around what axis does the rudder cause the plane to yaw?
Vertical.
All the primary flight controls utilize balance weights (aka counterweights) located toward the front of the control surfaces. What is the purpose of these weights?
Primarily to decrease control surface flutter at higher airspeeds. The weights also have the effect of reducing pilot control forces.
At slow airspeeds, would you expect your flight controls to be more or less effective? Why?
Less, due to the reduced airflow over the control surfaces.
Let’s say I trim the plane nose down, i.e. roll the trim wheel from bottom to top. What effect will this have on the trim tab?
The trailing edge of the trim tab will deflect upward.
And how does this cause the airplane to maintain its nose-down pitch attitude?
With the trim tab up and into the airstream, the airflow over the horizontal tail surface tends to force the trailing edge of the elevator down. This causes the tail of the aircraft to move up and the nose to move down.
What is the primary purpose of trim?
To relieve control pressure.
Does the 172 have a servo or anti-servo trim tab? What’s the difference?
Servo, which means the tab deflects in the opposite direction as the elevator’s movement in order to increase control sensitivity, i.e. make the elevator more controllable. Anti-servo tabs are typically found on planes with stabiliators; because the whole control surface moves and therefore deflects a relatively large amount of air, stabilators are generally outfitted with anti-servo tabs in order to decrease control sensitivity, thereby preventing over-controlling the airplane and overstressing the airframe.
Does your rudder have trim? If so, what kind?
Yes, it has a ground-adjustable trim tab - basically a piece of metal that can be bent manually on the ground.
Can pilots adjust the ground adjustable rudder trim tab, or just certified mechanics?
Yes pilots can adjust the rudder trim, although ATP wants maintenance to handle rudder trim adjustments.
What kind of flaps does your aircraft have?
Electrically operated, single-slot type flaps, with detents at 0, 10, 20, and 30 degree positions.
Where is the flaps motor located? In
the right wing, a couple feet outboard of the cabin.
What are some of the purposes of flaps?
1) Flaps produce more lift for any given angle of attack, permitting a lower landing speed,
2) flaps produce greater drag, permitting a steeper descent angle without airspeed increase, and
3) flaps reduce the length of the
landing roll.
Which flap settings increase lift, and which increase drag?
The AFH says that, generally, the first 15 degrees of flaps primarily produces lift, whereas any flap deflection beyond 15 degrees generates large increases in drag.
How does the slot in the slaps aid in producing lift?
When the slotted flap is lowered, high energy air from the lower surface of the wing is ducted to the flap’s upper surface. The high energy air from the slot
1) accelerates the upper surface boundary layer and
2) delays airflow separation.
The metal skin of all the control surfaces - primary and secondary - is bent. What’s this bent metal called, and why is it designed this way?
It’s called “corrugation.” It increases the structural strength of the metal.
What are some of the various functions of the engine?
Provides the power to turn the prop, generates electrical power, provides a vacuum source, provides a source of heat for the cabin.
Reciprocating engines operate on what basic principle?
They convert chemical energy (fuel) into mechanical energy.
How is this done? How do we go from fuel inside the cylinders, to a spinning prop creating thrust?
The sparks generated from the spark plugs ignite the fuel, causing controlled explosions that push the pistons inside the cylinders down. These pistons are connected to the crankshaft, causing the crankshaft to rotate. The rotating crankshaft is directly connected to the propeller, causing the prop to rotate at the same speed as the crankshaft. As the prop spins it throws back air, and the equal/opposite reaction to this air being thrown back is called thrust.
Tell me about your aircraft’s engine.
It’s a Lycoming, 4-cylinder, normally-aspirated, fuel-injected, 360 cubic inch, horizontally opposed, air-cooled, direct-drive IO-360-L2A engine.
What is its horsepower rating, and at what RPM?
180 horsepower at 2700 RPM.
What do the “I,” “O,” “360,” and “L2A” represent?
“I” means that the engine is fuel injected (as opposed to carbureted). “O” stands for Opposed, as in the cylinders are positioned such that they horizontally oppose each other. “360” means 360 cubic inches of air displacement, meaning that the total space inside the engine’s 4 cylinders adds up to 360 cubic inches - the more space, the more fuel/air can be burned so the more power the engine can produce. The “L2A” is the engine model.
What does horizontally opposed mean, and what makes horizontally-opposed engines so popular?
This refers to the layout of the cylinders - they horizontally oppose one another with 2 cylinders on one side of the crankshaft, and 2 on the other. These engines are popular because they tend to be lighter as well as more compact/streamlined, minimizing drag.
What does direct drive mean?
This means that the propeller is directly connected to the crankshaft - if the engine (the crankshaft) is spinning at 1,000 RPM, the prop is spinning at 1,000 RPM. Some aircraft with more powerful engines and/or longer props use gear reduction boxes to keep their props spinning at lower RPM than the engine in order to prevent the prop tips from achieving supersonic speeds.
Take me through what is going on internally during the ignition process for your aircraft, from battery master on to the engine running on its own. Feel free to reference your checklist.
Turn on the battery to supply electricity to the starter and the auxiliary fuel pump. Crack open the throttle, turn the aux fuel pump on, and push the mixture in to allow fuel to flow into the cylinders - i.e. prime the engine. Then pull the mixture back to cut-off and turn the aux pump off to avoid over-priming/flooding the engine. Press and hold the starter, which contains a spinning gear that now protrudes out a bit and links up with the flywheel’s gear, causing the fly wheel to spin. The flywheel is attached to the crankshaft, which is geared to the magnetos. Now the magnetos are operating, providing electricity for the spark plugs to start firing off sparks inside the cylinders. There is already fuel inside the cylinders from the initial priming, so now there is combustion. At this point engine operation has become self-sustaining, so the starter can be released. The rapid opening and closing of the cylinders spins the crankshaft, which is directly connected to the propeller, causing it to spin.
What happens if you turn off the master switch after ignition, why?
Nothing, the engine would continue to run because the engine drives the engine-driven magnetos, which generate the electricity to produce sparks, causing the fuel in the cylinders to burn, causing the engine to keep running, causing the magnetos to keep running…it’s a self-sustaining process.
Explain how a magneto works.
Inside a magneto there is a magnet, geared to the engine, spinning rapidly in close proximity to a coil of copper wires. This generates and harnesses electricity for the spark plugs.
Where are the magnetos located?
On the accessory case - the back of the engine.
What’s the function of the Impulse Coupler?
When the starter is engaged, the engine RPM are too low for the mags to generate sufficient electrical current for the spark plugs. So to generate that high amount of initial electrical current despite low RPM, one of the mags has something called an impulse coupler attached to it. The impulse coupler is a coiled spring that winds up real tight at first, then snaps, causing the magnet inside to spin really fast and generate a lot of electricity for its spark plugs.
How many magnetos does your plane have, and why?
2, for redundancy, as well as for more even burning of the fuel (better performance).
How many spark plugs are connected to each magneto, and where do those plugs go?
Two spark plugs in each cylinder 8 total. 4 from each mag
During the run-up, you check the left mag and the engine quits. What’s the problem?
Mag failure.
During the run-up, the engine feels rough and there’s a 200RPM drop. What’s the problem?
Fouled spark plug(s).
What causes fouled spark plugs?
Usually running the engine with the mixture full rich at low RPM, i.e. running the engine too cold. If the engine runs too cold, lead and carbon don’t burn off completely and end up in the form of deposits of the plug heads.
What’s the remedy for fouled spark plugs?
Follow the checklist to run the engine hot and burn off the lead and/or carbon deposits, then do the mag check again to verify smooth operation.
Say during the right mag check the RPM drop is normal, but there is no drop when you check the left mag? What is likely the issue?
The right mag isn’t grounding.
How do you verify if the right mag isn’t grouding?
Turn the mags to OFF. If the engine continues to run then the right mag is clearly still operating, meaning it isn’t grounding.
Take me through each step of your aircraft’s air induction system.
The engine air induction system receives ram air through an intake on the lower front portion of the engine cowling. The intake is covered by an air filter which removes dust and other foreign matter from the induction air. Airflow passing through the filter enters an air box, which is equipped with a spring-loaded alternate air door. If the air induction filter should become blocked, suction created by the engine will open the door and draw unfiltered air from inside the lower cowl area. After passing through the air box, induction air enters a fuel/air control unit under the engine, and is then ducted to the engine cylinders through intake manifold tubes. Once burned, the exhaust gas is ducted out of the airplane through the exhaust pipe.
Approximately how much power loss should be expected when the engine operates off of
unfiltered alternate air?
10%.
What does “normally (or naturally ) aspirated” mean? As opposed to what?
It means that the engine’s air intake does not utilize a forced induction system such as a turbo or supercharger - rather it depends solely on ambient atmospheric pressure.
What does “air cooled” mean? As opposed to what?
This means that the relative wind flowing over the engine is primarily what cools it - as opposed to using some other cooling system like a radiator or heat exchanger or water cooling system.
How can the relative wind adequately cool the cylinders when they are largely confined within the cowling and therefore not exposed to the outside air?
This is where the cooling fins and baffles come in. The heat from the cylinders transfers to the cooling fins, which are exposed to the relative airflow, allowing the heat to dissipate. The baffles are positioned to guide the airflow to where engine cooling is needed, namely over the cooling fins/cylinders.
What else cools your engine besides air?
Oil.
What are the 3 ways to cool an engine in flight?
Decrease throttle, increase airspeed, enrichen the mixture
How many strokes does your plane’s engine use? Describe each stroke.
It’s a 4-stroke engine.
1) The intake stroke begins as the piston starts its downward travel. When this happens, the intake valve opens and the fuel-air mixture is drawn into the cylinder.
2) The compression stroke begins when the intake valve closes, and the piston starts moving back to the top of the cylinder. This phase of the cycle is used to obtain a much greater power output from the fuel-air mixture once it is ignited.
3) The power stroke begins when the fuel-air mixture is ignited. This causes a tremendous pressure increase in the cylinder and forces the piston downward away from the cylinder head, creating the power that turns the crankshaft.
4) The exhaust stroke is used to purge the cylinder of burned gases. It begins when the exhaust valve opens, and the piston starts to move toward the cylinder head once again.
What do the throttle and mixture lever control in a fuel injection system?
Increasing throttle opens up a butterfly valve to allow more air through the induction system; the fuel/air control unit senses this air increase and allows more fuel to mix with the increased volume of air in order to keep the overall fuel-to-air ratio unchanged. So ultimately, opening the throttle has the effect of allowing more of the fuel/air mixture to enter the cylinders, i.e. more combustion/power. Enrichening the mixture lever, on the other hand, causes the fuel/air control unit to add more fuel to the fuel/air mixture…without adjusting the amount of air, resulting in a more fuel-rich mixture. This may or may not have a small effect on overall power, depending on whether the mixture was originally too lean (not enough fuel in the mixture) or too rich (too much fuel in the mixture).
List off the specs for your plane’s propeller.
It’s a two-bladed, fixed pitch, one-piece, 76-inch propeller made out of aluminum alloy, manufactured by McCauley.
Say there’s a half-inch knick at the top of the propeller blade. Would maintenance be able to shave that down?
Yes, as long as the blade’s diameter doesn’t dip below 75 inches, which is the minimum permitted by section 2 of the POH/AFM.
Explain how the blade is twisted, and why?
The outside of the blade spins significantly faster than the inside due to the fact that the tip is traveling a longer distance in the same amount of time as the hub. If the blade had the same angle of incidence (aka pitch) throughout its length, the blade tip would produce more thrust than the blade hub. To prevent this, the blade is designed such that the tip takes a relatively small bite of air (has a low pitch), whereas the hub takes a large bite (high pitch). This allows the blade to produce uniform lift - or rather, thrust, because it’s directed forward - throughout its length.
What does “fixed-pitch” mean?
This means that the blade angle (or pitch) is set by the manufacturer and cannot be changed.
What are the two types of fixed-pitch propellers? Describe each.
Climb and cruise . A climb prop utilizes a low pitch, meaning that the blade spins through the air like a knife (from the perspective of the blade’s plane of rotation), rotating rapidly but taking small bites of air. A cruise prop uses a high pitch, meaning the blade spins through the air more like a paddle, rotating slowly but taking large bites of air.
What are the benefits and drawbacks to each type of fixed pitch propeller?
The climb prop’s low, knife-like pitch translates to less drag as the blade slices easily through the air, allowing it to spin at higher RPM and produce more horsepower. This increases performance during takeoffs and climbs, but decreases efficiency during cruising flight because the high RPM means more fuel burn. The cruise prop’s higher pitch/low RPM prop configuration doesn’t provide good climb performance, but it is more efficient for cruise flight due to the reduced RPM and therefore lower fuel burn.
Which type of fixed pitch propeller does your aircraft use?
The 172 uses a compromise of the two, a middle pitch.
What kind of landing gear does your plane have?
Tricycle type, with a steerable nose wheel and two main wheels. Shock absorption is provided by the tubular spring steel main landing gear struts and the air/oil nose gear shock (oleo) strut.
How do the tubular spring main gear struts work to absorb shock in our landing gear?
They ration the shock of the touchdown throughout the plane’s airframe.
How does the oleo strut work in our landing gear?
The exposed portion of the strut that we check for proper extension during preflight is a piston that has oil or some sort of hydraulic fluid inside it. During landing, when the tire hits the ground, the piston gets pushed up into the cylinder (upper chamber) above it, which contains compressed air or nitrogen. When the hydraulic fluid pushes against the air, it cushions the blow on the nose gear.
What is the purpose of the torque link, aka scissor?
The bottom section of the torque link is attached to the piston, while the upper torque link is attached to the cylinder (aka upper chamber). By locking firmly onto both the piston and the cylinder, the torque link prevents the piston from rotating inside the cylinder.
What landing gear feature prevents the nose wheel from vibrating excessively during higher speed ground operations?
Shimmy damper.
How does the Shimmy damper work?
There is hydraulic fluid inside the tiny horizontal cylinder. When you turn the nose wheel wheel at slower speeds, the fluid can easily get pushed around from side to side, so the turning is easy. At faster speeds, though, like on takeoff or landing roll-out, if the nose wheel starts turning too rapidly, the fluid can’t get through as fast, causing the damper to resist movement/vibration.
How is the nose wheel linked to the rudder pedals?
Through a spring-loaded steering bungee.
While on the ground, up to how many degrees each side of center does your plane turn, with the rudder pedals as well as with differential braking? 10
degrees with the rudder pedals alone, 30 degrees with differential braking.
Describe your aircraft’s brake system.
The airplane has a single-disc, hydraulically-actuated brake on each main landing gear wheel. Each brake is connected by a hydraulic line (looks like a hose) to a master cylinder attached to each of the pilot’s rudder pedals.
So how many master cylinders for the brakes are there in total on the plane
2
How is the co-pilot able to brake if there are no cylinders behind the right-seat pedals?
The right seat’s brake pedals are mechanically linked to the left seat’s pedals, which press down on the master cylinders.
Take me through what happens internally in the brake system after the pilot presses on the brake pedals.
Pressing on a brake pedal has the effect of pushing down on the piston in the master cylinder located just behind the brake pedal. The piston pushes the hydraulic fluid in the master cylinder through the hydraulic line into the brake assembly. Here, the fluid pushes against another piston which causes the brake pads to clamp down against the steel wheel disc that spins with the wheel. This creates friction and slows the plane.
What color is hydraulic fluid, and why is this important to know?
It’s a light reddish color. Knowing the color of the plane’s operating fluids makes troubleshooting leaks easier.
Where is the hydraulic fluid reservoir for the brake system located?
As mentioned earlier, the hydraulic fluid for the brake system is located in the master cylinders themselves, the ones behind the pilot-side rudder pedals.
What are some of the symptoms of an impending brake failure?
Gradual decrease in braking action after brake application, noisy or dragging brakes, soft or spongy pedals, and excessive travel and weak braking action.
If the brakes feel spongy and unresponsive on your landing roll-out, what are you going to do to get the plane stopped?
Pump the pedals in order to build up pressure in the brake lines.
What is the procedure for applying the parking brake ?
Hold the brakes firmly, then pull the barking brake lever out and rotate the handle 90 degrees down in order to lock in the hydraulic pressure.
Why do engines have oil systems?
1) Lubrication of the engine’s moving parts,
2) cooling of the engine by reducing friction,
3) removing heat from the cylinders,
4) providing a seal between the cylinder walls and pistons, and
5) carrying away contaminants.
What type of oil is approved for your aircraft?
Aviation Grade with Ashless Dispersant.
Say you need to add oil to an unfamiliar aircraft, how would you go about verifying the required oil type and quantity?
Check the POH/AFM.
What are your aircraft’s oil quantity limitations?
5 - 8 quarts.
What type of oil sump does your engine use?
Wet.
