Oral P.O.H Sect 7 Flashcards
What is the airframe?
It is an all metal, four place, high wing, single engine airplane equipped with a tricycle landing gear.
What is the construction of the Fuselage?
Semimonocoque: the internal structure of the fuselage, layered with stressed skin, stringers and sheet metal
What is the skin of our plan made of?
Corrugated aluminum skin
How are the flight controls powered?
Pulleys and wheels and cables
What are the primary flight controls?
Ailerons
Rudders
Elevator
Stabilator
What are the secondary flight controls?
Flaps
Rudder Trim
Elevator Trim
Anti-Servo Tab
What Kind of Breaks are on the Cessna 172?
Single Disk, Hydraulically Actuated
What kind of flaps does the Cessna 172 have?
Single slotted with Fowler type characteristics
Slotted: One single slot, delays airflow separation
Fowler: Multiple Slots
What type of Trim does the Cessna 172 have?
Manual Trim
Differential Trim: the trim functions opposite
Nose up: Trim Down
Nose Down: Trim Up
What is the attitude indicator?
Shows the airplanes orientation relative to the horizon, based on the planes pitch and bank angles
What Instrument would you lose if the Pitot Static Tube became clogged?
Air Speed Indicator
What are the 4 stages to our engine?
- Intake: brings air and fuel in
- Compression: the valve closes and and the mixture in compressed
- Combustion: the spark plug ignites the mixture (piston) creates mini explosion
- Exhaust: the spring release and exhaust is vented out
How many cylinders does the Cessna 172 have?
4
What are the advantages to a Fuel Injected engine?
Precisely meters fuel to each cylinder ⇒ increased performance/fuel economy
• Eliminates the hazard of icing over
How is our engine air cooled?
It uses cooling fins and baffling to redirect airflow between the cylinders this prevents hot spots from forming
Describe how Air is Induction works.
The air intake is located below the engine cowling
1) Uses air filter to remove contaminants before flowing to the fuel/air control unit.
2) If air intake became clogged
• Alternate air door would automatically open by suction
Engine experiences 10% power loss (Unfiltered)
Explain the Oil System.
It is a wet sump system (gravity fed back to the
sump located at the bottom of the engine)
1)Strainer
• Located inside sump; remove solid particles before pump
2)Pump
• Toothed gears driven by crankshaft, pressurizes oil
3) Bypass
• Cold oil ⇒ straight to filter
• Hot oil ⇒ oil cooler
4) Oil Cooler
• Matrix that spreads out oil allowing it to be cooled
• Cooling dependant on airflow
5) Filter
• Removes small contaminants
• If clogged
6) Spring-loaded relief valve back to sump
o Then lubricates engine components before returning to sump
What is the purpose of oil?
Cools, lubricates, prevents corrosion and carries away contaminants
What does the Nose Wheel have?
a shimmy damper which limits oscillations
What are symptoms for break failure?
What is the solution?
Gradual decrease in braking action
• Noisy or dragging brakes
• Soft or spongy pedals
• Excessive travel and weak braking action
Solution:
• Let up on pedals, then apply heavily (restore hydraulic pressure)
GET SERVICED!
Explain the Magnetos.
Self-contained engine-driven generator producing high voltage for spark to ignite fuel/air
(engine must be running)
o 4 cylinders
• 2 spark plugs/cylinder fed by independent magnetos (redundancy)
• More complete burn ⇒ better performance
o Impulse coupling [engine starting]
• Spring inside magneto winds up when engine rotates at low speeds
• When spring unwinds
Spins rotating magnet at high speed generating a sudden high voltage for
spark plugs (engine start)
• Engine starts: centrifugal force inside magneto disengages impulse coupling
o Turning ignition switch OFF grounds primary circuit (shuts off spark)
• If engine does not shut off
Defective switch, loose ground ⇒ “hot” magneto
Engine could start if propeller turned rapidly
Explain the Starting system.
o Master – ON connected to boost pump
o Ignition – START
• Closes circuit – energizes starter relay
• Current flows to starter motor
o Electro-mechanical solenoid connects bendix gear to the engine flywheel
• Begins rotation of the propeller[impulse coupling helps start]
The flywheel then connects to the crankshaft and that beings to turn the piston starting the 4 cylinder cycle and starting the engine
Explain the fuel system.
The fuel system consists of two vented integral fuel tanks, a three-position fuel selector, auxiliary
fuel pump, fuel shutoff valve, fuel strainer, engine driven pump, fuel/air control unit, fuel
distribution valve, and fuel injection nozzles
Explain the Exhaust System.
Exhaust gas is directed through a muffler on the right side of cowling this Reduces noise and directs exhaust gas away from aircraft.
Air is routed under the engine to the hot muffler shroud then fed to the cabin for heat
Fuel Indicators
(Only reliable when empty)
• Electrical resistance sensors.
• Low resistance – full fuel
• High resistance – low fuel
• Low Fuel light at 5 +/- 1 gallons
• Ranges 0-24 gallons [per side], rest is unreadable
When can you use fuel from either the left or right tank on your aircraft?
Only in cruise.
FAA Regulation about fuel tanks?
23.951
1 tank per engine
We get around the his by having a fuel reservoir underneath the floor of the copilot seat
The fuel return line
Prevents vapor lock (fuel vaporizing in the lines)
Fuel Shutoff Valve
Mechanical linkage in case of an emergency can be pulled by the pilot to entirely shut off fuel flow to the engine.
Tell me about our 2 Fuel Pumps
Auxiliary fuel pump located under copilot floorboard [priming/redundancy]
• Engine-driven fuel pump
Constant fuel supply from strainer to fuel/air control
Fuel Air Control Unit
• precisely meters the amount of fuel going into the engine based on the volume of air going passed the throttle
• fuel control unit
mechanically linked mixture control valve [amount of fuel]
Fuel Distribution
(Spider)
Located above the engine
Evenly distributes fuel to the fuel injector nozzles (introduced for combustion)
When is it best to refuel the plane?
At night, (warmer temperatures expand fuel)
Summarize our electrical system
28V DC system; 2 batteries, 1 alternator (charges batts/powers all buses if batts charged
Standby Battery
24-volt battery
powers only essential bus
located behind PFD, cooled by fan
last 30 mins if charged
@ 20V shuts off
Explain the Vacuum System
(The standby altitude indicator relies on this)
Air is brought in by an engine driven pump
And a regulator is used to provide constant pressure.
Explain the Pitot Static Tube
[airspeed, altimeter, vertical speed indicator]
• Three sources: Pitot tube + static source + alternate static source
• Airspeed Indicator: Dynamic pressure (pitot) – Static pressure (static) = airspeed
o Dynamic pressure enters diaphragm expands/contracts against static pressure
o Types of airspeed (ICE-T)
Indicated: read on instrument
Calibrated: IAS corrected for installation errors
True: CAS corrected for non-standard temp and altitude
Explain the Altimeter
Aneroid wafer (sealed) expands/contracts with decrease/increase in static press.
o Types of altitude (ITA-PD)
Indicated: read on instrument
True: MSL
Absolute: AGL
Pressure: height above SDP
Density: Pressure alt corrected for non-standard temp (performance)
Explain the Vertical Speed Indicator
Measures differential pressure [trend of pressure = climb/descent]
o Current static press enters diaphragm
Pitot Static Blockages will cause what reaction?
Pitot tube only = airspeed “0”
• Pitot tube + drain hole = airspeed as altimeter
What will happen if the static source opening becomes blocked?
Static source
o Airspeed: climb: lower than normal, descend: higher than normal
o Altimeter: freeze
o VSI: “0”
What happens when the alternate static source is pulled?
Alternate static (lower static pressure inside cabin)
o Airspeed: higher
o Altitude: higher
o VSI: momentary climb
