Aircraft Engines, Systems and Emergencies

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Commercial Ground School AVF 221

Aircraft Engines and Systems

P-51 Engine
Rolls-Royce Merlin
12 cylinders
Gear reduction
1,750 hp
Often referred to as the engine that won the war
Merlin Engine
Packard built Rolls Royce Merlin engine

Injected opposed 520 cubic inches
285 horsepower
6 cylinder
12 quarts of oil


12 or 24 volts

4 components:
Rotor – basically a rotating magnet, induces electrical flow in the stator
Stator – coils that are stationary around the rotor, they produce the electricity
Diodes – these are a one way check valve for electric current, turn AC into DC
Voltage regulator – senses the need for current and varies the feed to the rotor

Fuel injection for most airplanes is of the continuous flow variety
So named because the flow is not timed to valve or crankshaft position
This means fewer moving parts
No complicated spring loaded injector nozzles or timing mechanisms
There are 2 primary types:
Bendix Fuel Servo (Lycoming)
Continental uses RPM for fuel metering
The more rpm the more fuel
Bendix system uses delta pressure across a diaphragm
The more venturi pressure, the more fuel

Component parts:
Fuel pump
Fuel control unit
Throttle body
Fuel manifold unit (spider valve)
Injector lines
Fuel pressure or fuel flow gauge
Associated fuel lines, returns, screens, adjustment mechanisms, idle cutoff and pressure relief valves

Fan driving a fan
Exhaust side
Intake side
Operational Rules:
Smooth steady throttle to prevent over-boosting
Watch the blue lines on the manifold pressure gauge for limits at altitude
Let the turbo cool at idle for 3 to 5 minutes after landing before shutting down
Tip Flings, Turbine Kissing, Coking, FOD, Metal Contamination

There are 5 forces on the prop
Centrifugal force
Thrust bending force
Torque bending force
Aerodynamic twisting moment
Centrifugal twisting moment
As V increases alpha on the prop decreases
Wouldn’t it be cool if we could somehow change the angle of the prop blade to get a better alpha?

The governor sends high pressure oil (400-500 psi) to the prop hub
Low pitch – high rpm
High pitch – low rpm
3 conditions of the governor
No exchange of oil to or from the pitch change mechanism
Diverts oil into the pitch change mechanism
Lets oil out of the pitch change mechanism

Pilot valve
Speeder spring
High pressure oil pump
Relief valve

Non counter weight propellers
This is the type on the bonanza
It takes oil pressure to move the blade to a high pitch low rpm condition
A spring and centrifugal twisting moment move it back to low pitch high rpm
Counter weight propellers are generally found on twins featuring full feathering props
They operate exactly backwards and you can learn about them in your multiengine class

The Bonanza has electric gear
The Seminole has hydraulic
Hydraulic pressure is used to keep the landing gear retracted
Emergency gear extension

An electric motor causes push pull tubes to move the gear up and down
The hand crank is for emergency gear extension


A shock strut is constructed of two telescoping cylinders or tubes that are closed on the external ends.
The upper cylinder is fixed to the aircraft and does not move.
The lower cylinder is called the piston and is free to slide in and out of the upper cylinder.
The lower chamber is always filled with hydraulic fluid and the upper chamber is filled with compressed air or nitrogen.
An orifice located between the two cylinders provides a passage for the fluid from the bottom chamber to enter the top cylinder chamber when the strut is compressed.
The metering pin is tapered to decrease fluid flow as the strut is compressed
Some use a metering tube instead of a pin
Holes in the metering tube provide the same function as the pin

Up locks keep the weight of the gear off the motor and retraction mechanisms
Down locks do the obvious
Geometric over center lock
Gear safety switches

Dampens nose wheel shimmy
Hydraulic fluid is forced through a small orifice which restricts movement of the nose wheel
Hydraulically steerable nose wheels generally don’t have these

Current – the movement of electrons along a conductor (measured in Amps)
Voltage – the electromotive force of push or pressure from one end of a conductor to other (measured in volts)
For example a voltage meter will measure a force of 12 or 24 volts across the positive and negative terminals of a battery
Resistance – in any electrical circuit when voltage is applied the conductor will resist the flow (measured in Ohms)
The greater the resistance, the less current flow
Since metals have the highest number of free electrons, they have the least resistance
Good conductors – Silver, copper, gold, aluminum
Poor conductors – Rubber, glass, ceramics, plastics
Watts – measurement of electrical power (work/time) or Voltage x Amperage
Ohm’s Law
Current (I) = Voltage (V) or (E) / Resistance (r)

To help visualize what is happening with the electron flow we can think in terms of a water system
The water pressure in the tower is like voltage
Not all the water can flow at once because of the restriction of the size of the pipe (resistance)
The flow rate through the pipe is like amperage
If we could increase the pressure in the tank, the flow rate would increase and more water would come out of the pipe
Increasing voltage will make more current flow
What if we put a larger size pipe on the tank?
Decreasing the resistance would increase voltage
If we increase the pressure on the wheel we can lift more (wattage)
If we increase the flow rate on the wheel we can lift more (wattage)

Components include
Circuit breakers/fuses
Switches, relays and solenoids
Remote control electromagnetic switch

Engines need 3 things to run:
When suffering from engine troubles, these three should be examined first
Our emergency checklists revolve around these 3
Carburetor ice
Lack of air
Mixture/Fuel management
Lack of fuel
Magneto check
Lack of spark

Loss of oil pressure
Corroborated by high oil temperature
Keep it cool – throttle back, cowl flaps open, mixture rich, land with power
Electrical – isolate problem circuit
Strong smell of burning wire insulation
Fuel – turn off fuel, initiate emergency descent if judgment dictates
Engine fires are usually well developed by the time they are detected
Oil fires are accompanied by thick bla
ck smoke
Fuel fed fires are accompanied by orange flames
Consider severe structural damage in any on board fire
Cabin fires – 3 primary causes
Careless smoking on board
Electrical system malfunctions
Heating system malfunctions

3 Types:
Forced landing
Remember energy to be dissipated goes up at the square of the airspeed so gear down, touch down slowest controllable speed BUT STILL FLYING!
Use normal pattern to enhance touchdown accuracy
Use all the tricks – slips, s-turns, flaps
Precautionary landing
Used when further flight is not practical
Fuel shortage, weather, lost, gradual engine trouble
Parallel to the waves
Psychological hazards
Reluctance to accept the emergency situation
Desire to save the airplane
Undue concern about getting hurt

A pilot’s choice of emergency landing sites is governed by:
The route selected
The height when engine failure occurs
Excess airspeed
Planning the approach is governed by 3 factors:
Wind direction and velocity
Dimensions and slope of the landing spot
Obstacles in the final approach path
Terrain types
Confined area
Shy away from steep descents to reach a small open area
Approach into the wind
Make nose high contact with tree tops
Avoid tree trunks
Free fall from 75 feet = 40kts
Try for symmetrical contact

Glassy water approach may loose depth perception
On low wing use intermediate flaps to prevent asymmetrical flap failure
Gear up
Deep snow
Same as ditching procedure
Engine failure after takeoff
Altitude available is the controlling factor
4 second reaction delay is typical, (usually 7-10 seconds in my experience)
Be sure to account for radius of turn if you’re doing a 180
Use a 45° bank if possible

Loss of elevator
Loss of one of the cables doesn’t result in total loss of control
It may be possible to trim against the control you still have
Loss of up elevator
Apply considerable nose up trim
Push to obtain desired attitude
Increase forward pressure to lower the nose, relax to let the nose up
Release forward pressure on flare
Loss of down elevator
Apply considerable nose down trim
Follow same steps as above only reversed
In any loss of primary flight control find out what minimum speed you still have control
Use this speed as your minimum touchdown speed

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