01-G: Operation of systems

Knowledge

K1: Airplane systems, including

K1a: Primary flight controls

K1b: Secondary flight controls

• Flaps
  • Flaps 10: adds lift with minimal drag
  • Flaps 20 and more: adds drag with mininmal lift

K1c: Powerplant and propeller

• piston engine

  • four strokes in a piston engine (mnemonic: Suck, Squeeze, Bang, Blow)
    • intake
    • compression
    • combustion/power
      • failure modes
        • detonation
          • caused by
            • lower than specified fuel grade
            • high manifold presssure with low RPM
            • high power setting with excessively lean mixture (i.e., too little fuel for cool down)
            • lack of airflow that could cool the engine, due to steep climbs or extended ground operations
          • procedures
            • ensure proper fuel grade
            • enrich mixture
            • increase airspeed while reducing power (reduced climb rate)
            • full-open cowl flaps
        • preignition
          • caused by
            • cracked spark plug insulators
            • damaged cylinder that are heated up
          • procedures
            • reduce power
            • reduce climb rate
            • enrich mixture
    • exhaust (expelling most heat of the combustion)
  • reciprocating engines
    • are less expensive and
    • simpler in design than other engine types
  • mixture
    • excessively rich mixture causes spark plug fouling due to incomplete fuel combustion, i.e., leading to carbon buildup on the spark plug in turn leading to engine roughness
  • dual ignition system
    • purposes
      • redundancy
      • improved engine performance through more efficient burong of the fuel/air mixture through dual flame fronts within the cylinder
    • "hot mag" problem
      • we cannot really switch off a magneto because it is self-powered and a closed circuit by itself
      • instead, when putting the switch to off, we ground the circuit via the grounding wire called p-lead (fail safe)
      • if the p-lead is broken, the magnet stays hot and generates sparks whenever the prop turns
      • only way to turn off the negine is to starve the engine by setting the mixture to cut-off
  • prevent overheating during a climb
    • by lowering the nose and thus reducing rate of climb (to reduce load on the engine)
    • increasing airspeed (to cool the engine with oncoming air)
    • by increasing the mixture (to cool the engine with cold, superfluous fuel)
  • hand-propping requires a compotent pilot at the controls of the cockpit to hold the breaks and avoid aircraft run-away
  • cooling
    • primary mechanism: exhaust
    • secondary mechanism:
      • oil circulation
      • air directed around the engine using engine baffles (Umlenkbleche)
  • engine start
    • immediately after engine start
      • adjust for proper RPM
      • check for desired indications on the engine gauges
        • oil pressure should rise as the oil pump begins circulating oil
  • alternator
    • produces alternating current (AC) which is then converted to direct current (DC)
    • electrical output of an alternator is more constant throughout a wide range of engine speeds

• constant-speed (i.e., variable pitch) propeller

  • principle
    • the throttle controls power output as reigstered on the manifold pressure gauge
    • the the propeller control regulates engine RPM as registered on the tachometer
    • despite its name, the prop control lever still controls RPM, but for a given RPM the governor will find the most efficient blade pitch angle
  • properties
    • constant-speed (i.e., variable pitch) propeller is more efficient than constant-pitch (i.e., variable RPM) propeller as it allows the most efficient engine RPM for the given conditions
    • high manifold pressure settings with low RPM should be avoided (high pressure with high RPM is usually acceptable)
      • think: avoid full gas pedal with low RPM in a car
    • low pitch results in high RP

• left-turning tendencies:

  • a decrease in pitch attitude results in a yawing moment to the left around the vertical axis

K1d: Landing gear

• main gear
  • tubular spring steel
  • disc-type brakes
• nose gear
  • olear strut
    • pneumatic-hydraulic system filled with air and hydraulic fluid
  • direct linage to the rudder pedals
    • spring-loaded push-pull rod turns the nosewheel
  • +/- 10 degrees turn
  • differential braking for tighter turns
  • towbar
    • pulling: can pull and steer by the bolt to which the towbar is clipped on
    • pushing: steer by towbar, push on prop

K1e: Fuel, oil, and hydraulic fluid

• hydraulic fuel

  • mineral-based hydraulic fluid
  • MIL-H-5606
  • dyed red

• engine oil

  • circulation of oil
    • in normal operation ensures
      • cooling (by reducing friction and circulation)
      • cleaning
      • lubrication
    • low oil pressure
      • leads to higher temperatures due to lack of lubrication and cooling
      • can be caused by a leak in the oil system

• fuel system

  • fuel tanks:
    • filling the fuel tanks after the last flight of the day prevents moisture condensation by replacing potentially moist air with fuel in the tanks
    • fuel vents
      • principle
        • allow air to enter as fuel is consumed to maintain atmospheric pressure inside the tank, thus preventing the formation of a vacuum
      • components
        • primary vent: J-tube below the left wing (connecting the left tank to the right tank)
        • backup vent: valves integrated into the fuel caps
      • blockage
        • results in engine stoppage from fuel starvation (as the forming vacuum prevents the fuel nozzle from extracting further fuel from the tank)
        • this is better than crumpling wings
  • fuel injection system
    • engine-driven fuel pump
      • provides pressurized fuel to the fuel/air control unity
      • aux or boost fuel pump used as backup for the engine-driven pump
    • fuel manifold valve
      • distributes fuel to the individual fuel discharge nizzels
    • discharge nozzles
      • located in each cylinder head to inject fuel/air mixture at the precise time

  • carbureted system

    • venturi
      • think of a car with an open passenger window
      • while the car is standing the air on the outside of the car has a static pressure
      • as soon as the car starts moving the air will suck stuff out of the car, i.e., pressure is higher on the inside of the car than outside
      • the flow of air around the car decreases relative pressure
    • carburetor
      • routes intake air through a venturi
      • the lower pressure in the venturi pulls fuel from the fuel nozzle and evaporates it into the air
      • evaporation leaves the fuel with lower energy state behind, thus reducing its temperature by as much as 20 to 30 °C
      • thus icing can develop downstream at the throttle plate restricting the flow of enriched air into the cylinder
      • the nozzle pulls its fuel from the float chamber which is a small buffer area between the tank and the nozzle
      • the float chamber should contain constant amount fuel (if it were directly to pull fuel from the tank, the pressure would be high at full tank and low at near empty tank)
      • to maintain the same fuel amount in the float chamber a floating ball (the float is connectied to the fuel inlet)
      • as the fuel amount gets low, the float sinks connected via a rod to the inlet opens a valve letting in more fuel
      • as the fuel amount rises from inflowing fuel, the float lifts and closes the valve
    • carb heat
      • principle
        • blocks the air from the air intake and re-routes it by the exhaust manifold to warm it up first
        • sends the warm air into the cylinders instead
        • thus reduces the density of the air entering the cylinder
        • thus creates a loss of air in the fuel/air ratio
        • thus corresponds to enriching the fuel/air mixture
        • thus generally decreases engine performance
      • conditions
        • temperature between 20 and 70 °F (as evaporation brings the temperature in the carburator down to below freezing)
        • visible moisture or high humidity (i.e., moisture in the air that turns into ice as temperature drops behind the venturi)
      • carb icing
        • sequence
          • loss of RPM
          • engine roughness
          • engine stoppage due to lack of air
        • prior to stoppage, the presence of carburator ice in an aircraft equipped with a fixed-pitch properller can be verified by applying carb heat and noting
          • first, a decrease in RPM (as usual when carb heat is applied and fresh air is diverted from the engine intake)
          • second, an increase in RPM (as the ice melts, potentially also leading to engine roughness as water enters the air/fuel mix)

  • fuel

    • AvGas:
      • most common: 100LL (LL = low-lead), light blue
      • 100UL, yellow
      • 100LL + 100 UL blended: green (https://www.aopa.org/news-and-media/all-news/2022/november/pilot/unleaded-fuels-gami-gets-stc)
    • octane rating = fuel grade
      • measures a fuel's ability to resist knocking (premature combustion), i.e., ignite from heat through compression only instead of awaiting the spark plug-induced ignition
      • lower than recommended fuel grade leads to
        • detonation/knock (uncontrolled, explosive ignition) causing
          • overheating (elevated cylinder head temperatures)
          • power loss
          • piston failure
        • preigntion (early burn of the fuel but not explosively)
        • thus increasing cylinder head temperature
    • refuelling procedure: https://www.takeoffjunkie.com/how-to-refuel-an-airplane/
    • piston engine will start on jet fuel, but run into detonation and overheating
  • mixture control
    • controls the air fuel ratio (AFR) in terms of mass (not volume)
    • regulates the ratio of gasoline to air entering the fuel distribution system
    • leaning:
      • adjusting the fuel/air mixture at altitude to decrease the fuel flow in order to compensate for decreased air density
      • leaning technique (above 3000 ft density altitude) 1) turn knob in leaning direction carefully until engine runs rough (flaky tach needle) 2) enrich again until engine runs smooth again
      • if forgotten, the mixture becomes too richer

K1f: Electrical

• electrical system

  • alternator provides
    • 60 amp
    • 28 volt
    • direct current
  • 24 volt battery
    • higher voltage output of the alternator ensure lower voltage battery can be charged
  • powers
    • avionics
    • turn coordinator
    • fuel gauges
    • oil temperature gauge
    • pitot heat
    • lights
    • flaps
    • electrical fuel pump
  • voltage regulator
    • ensure alternator output is at 28 +/- 0.5 volts
  • ammeter
    • measure the net current in amps
      • 0 A: no net current into or out of the battery (alternator supplies all energy needed)
      • +10 A: battery is charged at 10 amps
      • -10 A: battery is discahrged at 10 amps
    • test procedure:
      • apply flaps (can be specifically tested in the run-up if concerned about functionality of the ammeter)
    • indication sequence
      • normal sequence
        • pre-starting:
          • negative indication as we draw energy from the battery
        • shortly after starting:
          • positive indication to replenish battery
        • in flight:
          • zero
      • non-normal sequence and procedure
        • inflight charge: overcharging due to a broken voltage regulator with explosion potentially
          • turn off alternator and pull circuit breaker (to avoid standby battery drain)
          • save energy and terminate flight
        • inflight discharge: broken alternator
          • reset alternator circuit breaker
          • turn off alternator and pull circuit breaker (to avoid standby battery drain)
          • save energy and terminate flight
  • voltmeter
    • 24 V: battery only
    • 28 V: alternator online

• glass cockpit

  • air data computer
    • failure leads to loss of the airspeed indicator
  • artificial horizon spans the entire width of the display
  • increased situational awareness

K1g: Avionics

K1h: Pitot-static, vacuum/pressure, and associated flight instruments

• altimeter

  • in Figure 3:
    • understanding the needles
      • shortest altimeter needle is the most significant digit (i.e., 10'000 needle)
      • can be cross checked by seeing that the shortest needle is constrained to the area less than 2 while thick middle needle and thin long needle are all over the place
    • resulting reading
      • Figure 3.1: 10'500
      • Figure 3.2: 14'500
      • Figure 3.1: 9'500

• six-pack / steam gauges

  • pitot-static system
    • airspeed indicator [ASI]
      • holes
        • big front hole: pitot/ram air/impact pressure inlet
        • tiny underside hole: drain hole
        • big side hole:
          • no one seems to know
          • https://www.boldmethod.com/learn-to-fly/systems/what-happens-when-your-pitot-tube-ices-over-failure-scenarios/
            • either unconnected static port or
            • drain hole
      • principle:
        • compares static/ambient and dynamic/impact pressure
        • ram air builds pressure in the pressure chamber
        • pressure is transmitted from air-filled pitot-tube into the inside of the diagraphm in the instrument case
        • static port transmits pressure into instrument case outside of the diaphragm
        • diaphragm expands or contracts, driving the gears and needle
      • only instrument that is affected from pitot tube blockage
      • blockage types
        • pitot hole blocked and drain hole open
          • drain neutralizes pitot tube to outside air
          • no difference between pitot tube pressure and static port, thus 0
        • pitot hole and drain hole blocked
          • traps the current pressure
          • static port open
            • becomes an altimeter
          • static port blocked
            • current setting is locked in
        • static port blocked, pitot pressure and drain hole open
          • inverse altimeter
      • airspeed types
        • indicated airspeed (IAS):
          • airspeed readable from the instrument
          • exact measure of lift
        • calibrated airspeed (CAS)
          • IAS correect for installation and instrument error
        • true airspeed (TAS)
          • airspeed corrected for air density = corrected for pressure and temperature = corrected for altitude and temperature
      • errors
        • density error (IAS diverges from TAS at high low densities)
        • position error (sideslip, slipstream)
        • compressibility error (air compression at high airspeed)
    • altimeter [ALT]
      • disassembly:
        • https://www.askacfi.com/1201/inside-an-altimeter.htm
      • principle:
        • compares static port with reference pressure
        • aneroid wafer, calibrated to standard pressure 29.92, expands and retracts in comparison to the static pressure provided by the static port, driving the gears
      • increasing the altimeter setting in the Kollsman window, increased the indicated altitude (and vice versa)
      • limitations:
        • on warm days, pressure levels expand, so altimeter senses a pressure higher than expected, so will indicate lowwer than true
        • on cold days, pressure levels contract, so altimeter sense a pressure lower than expected, so will indicate higher than true (dangerous!)
    • vertical speed indicator [VSI]:
      • principel: compares static port pressure with lagging pressure in that port
      • can be adjusted via a screwdrive by the pilot in the cockpit if it does not read zero
  • vacuum suction system
    • system principel
      • engine-driven pump pulls air through the instrument case
      • rotates the rotors (rotating part of the gyro) at 10k to 20k RPM to produce rigidity in space
    • attitude indicator [ATT]
      • usage
        • the only instrument that provides instantaneous pitch and bank information
        • determine the direction of bank by the relationshp of the miniature airplane to the deflected horizon bar
    • heading indicator [HI] / horizontal situation indication [HSI] / directional gyro [DG] / direction indicator [DI]
      • limitations:
        • Heading indicator must be periodically realigned with the magnetic compass as the gyro precesses
  • electrical system
    • turn and slip coordinator [TC] with inclinometer and standard turn indicator
      • provides information about yaw (vertical) and roll (longitudinal) axis
      • electically driven gyroscope
    • most other gauges

• slips vs skids

  • principle
    • e.g., left turn needs left rudder, but not too much: 1) apply left aileron; left wing goes down, right wing goes up 2) right wing going up means right wing produces more lift, means it produces more drag 3) right wing producing more drag means the aircraft will yaw to the right, producing a slipping uncoordinated flight, where the airplane flies in a circle but the nose points outward the circle right of the turn's tangent 4) yawing to the right means we need to step on the left rudder to counteract (we know we always "step on the ball", i.e., we know the inclinometer shows the ball to the left), re-establishing coordinated flight 5) exaggerating left rudder means the nose will point inward the circle of the turn, producing skidding uncoordinated light, with the right high-wing blanketing the elevator, esp. dangerous on final (low airspeed, close to the ground, accelerated stall, erroneous tendency to pull on the elevator to steepen the turn to make the turn in time when overshooting final)
  • consequences
    • left turn induces slip with left deflection of the inclinometer ball

• usefulness

  • forward slips are a useful maneuver to lose altitude, and we induce a forward slip by using aileron to the left and rudder to the right (and vice versa)
  • skids are dangerous as they blanket the elevator

• speeds:

  • V_NE
    • name: never-exceed speed
    • indication: upper limit of the yellow range
    • protection: any excess will cause structural damage (think: a wing tears off)
  • V_NO
    • name: maximum structural cruising speed
    • indication: lower limit of the yellow range
    • protection: staying below protects us from structural damage due to significant turbulence
  • V_A:
    • name: (design) maneuvering speed (sometimes misnamed as turbulent or rough airspeed, which leads to confusion with the maximum structural cruising speed, so to be avoided)
    • indication: placard somewhere on the dashboard
    • protection: staying below protects us from damage due to high-load maneuvers (plane rather stalls than breaks)
  • V_FE:
    • name: max flap extended speed
    • protection: staying below with flaps down protects us from damage due to flap overspeeding
  • V_S1:
    • name: stall speed with flaps retracted
    • indication: lower limit of the green range
    • protection: staying above when flaps are up keeps us from stalling (BUT NOT IN ACCELERATED STALL CONDITIONS, e.g., turns, or any other elevator backpressure)
  • V_S0:
    • name: stall speed with flap extended
    • indication: lower limit of the white arc
    • protection: staying above with flaps keeps us from stalling (BUT NOT IN ACCELERATED STALL CONDITIONS, e.g., turns, or any other elevator backpressure)
  • V_LO:
    • name: maximum landing gear operating speed
    • protection: staying below during landing gear lowering and rectraction protects it from structural damage though flying at higher speeds with already extended landing is permissible
  • V_LE:
    • name: maximum landing gear extended speed
      • protection: staying below while flying with extended landing gear ensure the landing gear mechanism is not damaged
• arc:
  • yellow arc:
    • name: smooth air speed range
    • lower limit: maximum structural cruising speed (V_NO)
    • upper limit: never-exceed speed (V_NE)
  • green arc:
    • name: normal operating speed range
    • lower limit: clean configuration stall speed (V_S1)
    • upper limit: maximum strcutural cruising speed (V_NO)
  • white arc:
    • name: flap operating range
    • lower limit: flap-extended stall speed (V_S0)
    • upper limit: maximum flap-extended speed (V_FE)

K1i: Environmental

• cabin temperature is controlled by mixing
  • cabin fresh air
  • cabin heated air
• cabin heat
  • craeted by routing fresh air by the exhaust shroud

K1j: Deicing and anti-icing

• anti-icing equipment
  • prevents ice from forming
    • pitot tube
    • carb heat
• de-icing equipment
  • remove already formed ice
    • pneumatic boots (inflatable ballons break off accummulated ice)
• despite anti-icing and de-icing equipment, flight into icing conditions is usually not approved by the POH

K1l: Oxygen systems

• supplemental oxygen
  • must be provided and used above 12'500 ft MSL (91.211) by the flight crew for any time beyond 30 minutes
  • must be provided and used above 14'000 ft MSL (91.211) by the flight crew for any flight above 14'000 MSL
  • must be provided above 15'000 ft MSL (91.211) by the passengers

K2: Indications of and procedures for managing system abnormalities or failures

• altimeter error

  • temperature-variational error
    • altimeter mapping is engineering assuming the standard model (ISA) at 15 °C
      • on cold days, the pressure levels are compressed and the indicated altitude is higher than true altitude (watch out for terrain!)
      • on warm days, the the pressure leves are raised and the indicated altitude is lower than true altitude
    • error approximation:
      • rules of thumb:
        • standard lapse rate: 2 °C per 1000 ft
        • standard error: 4 ft per 1000 ft per °C deviation from standard condition (https://aviation.stackexchange.com/a/37790)
      • example calculation
        • 5500 ft true on a standard day (15 °C): true 5500 ft, indicated ft
        • 5500 ft true on a cold day (-20 °C):
          • temperature deviation: 35 °C
          • thousands: 5.5
          • 35 * 5.5 * 4 = 770
          • => true 5500 ft, indicated 4730 ft
        • 5500 ft true on a warm day (30 °C):
          • temperature deviation: 15 °C
          • thousands: 5.5
          • 5.5 * 15 * 4 = 330
          • => true 5500 ft, indicated 5830 ft
  • pressure-variational error
    • from low to high, eyes to the sky
      • altimeter indicates lower than you are (problematic for airspace clearance!)
    • from high to low, watch out below
      • altimeter indicates higher than you are (danger!)

• preheat the cabin in cold weather to prevent instrument stick

• high-elevation airport needs leaning, esp. if the engine runs rough after startup or during the carb heat check

Risks

R1: Detection of system malfunction or failures

R2: Management of a system failure

R3: Monitoring and management of automated systems

Skills:

S1: Operate at least three of the systems listed in K1 through K1l appropriately

S2: Complete the appropriate checklists