Fuel Injection Systems + Pressure Carbs Flashcards
Advantages of fuel injection systems over predecessors:
1) Better control of fuel economy and vaporization.
2) Evenly distributes fuel.
3) Eliminates carburetor icing.
Basic methods of fuel injection:
1) Direct injection
2) Continuous-Flow Injection
The most commonly used type of fuel injection system:
Continuous-flow injection.
______ fuel injection systems spray high pressure fuel into the cylinder itself.
Direct.
______ fuel injection systems premix the fuel and air in the intake port on each cylinder.
Continuous-flow
Two types of continuous flow injection systems:
1) Precision Airmotive RSA
2) Teledyne-Continental System
The basic components of an RSA injection system:
1) Venturi housing
2) Fuel Metering Unit
3) Fuel Regulator
4) Fuel Divider & Nozzles
The throttle lever in the cockpit controls what two valves of a RSA fuel injection system?
1) Throttle valve
2) Fuel metering idle valve
The RSA fuel metering unit includes what two valves?
1) Mixture control valve
2) Idle valve
Which valve includes the enrichment metering jet in a RSA fuel metering unit?
Idle valve
The three settings of the RSA mixture control valve:
1) Idle cutoff
2) Lean
3) Full Rich
The three settings of the RSA idle valve:
1) Idle power
2) Cruise power
3) Full power
The amount of fuel allowed through the idle and mixture control valves of an RSA fuel metering unit depends on the position of their ______ ______.
Valve plates
The RSA fuel regulator uses the ____________ and the ____________ to schedule fuel to the engine.
1) Air metering force
2) Fuel metering force
The air metering force is developed by the __________.
Venturi housing.
The Fuel metering force in an RSA fuel regulator is developed by the _______ and ________.
Ball valve.
Fuel metering unit.
T/F
Fuel required for idling is supplied by the constant effort spring in the fuel regulator.
False
Constant Head Idle Spring
In an RSA fuel regulator, the ____________ is used to smooth the transition between idle and cruise power.
Constant effort spring.
The constant effort spring is used to provide a smooth transition between ______ and ______ power.
Idle.
Cruise.
Metered fuel is distributed to each cylinder from the ________.
Fuel divider (RSA)
Fuel manifold valve (Teledyne)
Fuel flow to the cylinders is measured in ________.
Gallons per hour.
The stamped letter on the nozzle body references _________.
Metering orifice diameter.
T/F
The air metering force of a Teledyne Continental injection system is used with the fuel metering force to schedule fuel to the engine.
False.
Teledyne Continental injection systems use fuel metering force only
Basic components of a Teledyne Continental injection system:
1) Engine driven pump
2) Fuel/air control unit
3) Fuel manifold valve
4) Injector nozzles
The functions of the Manifold valve:
1) Even fuel distribution to cylinders.
2) Provides positive fuel shutoff.
3) Is a point for fuel flow readings to be taken.
T/F
Mechanics are not allowed to overhaul RSA or Teledyne Continental systems.
True
________ use the pressure difference between Venturi and impact air to produce a fuel metering force.
Pressure carburetors.
Pressure carburetors use the pressure difference between ________ and ________ to produce a fuel metering force.
Venturi air.
Impact air.
Pressure carburetors overcame what problems with float carburetors?
1) Carburetor icing.
2) Sensitivity to abrupt flight maneuvers.
3) Increasingly rich air/fuel mixtures at high altitudes.
Pressure carburetors inject fuel _________ (before/after) the throttle valve.
After.
T/F
The pressure carburetor mixture control system leans the fuel-air mixture with a needle valve which restricts fuel flow into the D chamber.
False.
The needle valve allows air to bleed between chambers A and B, lowering the air metering force and closing the poppet valve.
In a pressure carb, metered fuel is held at a constant pressure by the _________________.
Spring loaded discharge nozzle.
The device that automatically adjusts the fuel-air mixture ratio to keep it constant as altitude changes:
AMC (automatic mixture control)
When performing an idle adjustment, always adjust the _______ first, followed by the ___________.
RPM (speed).
Idle mixture.
When performing an idle adjustment, if the RPM increase is more than the specified amount when the mixture control is moved to IDLE CUTOFF, the mixture is ________.
Too rich.
The fuel control unit monitors what parameters of a turbine engine?
1) Power lever position.
2) Inlet temp and/or pressure.
3) Compressor speed.
4) Burner air pressure.
5) Turbine inlet temps.
An air-fuel mixture ratio of 6:1 will lead to a __________.
Rich blowout.
An air-fuel mixture ratio of 19:1 will lead to a ________.
Lean die-out
Types of fuel control units:
1) Hydromechanical
2) Hydropneumatic
3) Electronic engine control
The types of electronic engine controls:
1) Supervisory EEC
2) Full authority digital engine control (FADEC)
Basic components of a turbine engine fuel system:
1) Fuel tanks
2) Shut off/selector valve
3) Auxiliary and engine driven pumps.
4) Filters and low point drains
5) Fuel heat exchangers
The FCU maintains an air-fuel ratio of ______.
15:1
What controls the turbine engine acceleration and deceleration rates?
Fuel control unit. (FCU)
In a turbine engine the fuel control unit mixes fuel with _____ of the total air entering the engine.
25%
The air that mixes with the fuel in a turbine engine is called ________.
Primary air
When advanced, the power lever for a turbine engine compresses the _______.
Speeder spring.
As RPMs of a turbine engine increase, the _______ tilt _______.
Flyweights.
Out.
If RPM is constant and the speeder spring pressure is reduced, the flyweights tilt _____.
Out.
If flyweight forces and speeder spring pressure are equal, it is considered ________.
On-speed.
vs over speed and under speed
In a Hydromechanical FCU, _______ and _______ are used to control turbine engine acceleration and deceleration rates.
1) Differential relief valve
2) Burner pressure sensor valve.
The process of connecting engine controls and adjusting linkages:
Rigging
The adjustment of the FCU to the engine to develop correct RPM, EPR and EGT.
Trimming
Trimming the engine to the FCU is intended to develop the correct ______, ______ and ______.
EGT.
EPR.
RPM.
Techs must have accurate readings of what to perform engine trimming?
Temperature and air pressure.
If fuel types are to be changed, what settings of the FCU may need to be changed too?
Specific gravity.
Major categories of fuel nozzles:
1) Vaporizing.
2) Atomizing.
Types of atomizing fuel nozzles:
1) Simplex
2) Duplex
Primary functions of the P&D valve:
1) Supply fuel to the manifold and nozzles at correct pressure.
2) Dump fuel from nozzles and manifold to aid in rapid shut down and prevent fuel from evaporating and dripping into combustion chamber.
P&D stands for what?
Pressurization and Dump valve
Used to to change the spray pattern of the fuel nozzles:
Pressurization and Dump valve.
T/F
The FCU of a turbine engine does not have a mixture control.
True
Allowable maintenance for RSA and Teledyne Continental fuel systems:
1) Nozzle inspection/cleaning.
2) Idle speed and mixture adjustments.
3) Low/High fuel pressure checks.
Modern turbine FCUs maintain ________ and vary _______ with changing atmospheric conditions.
TIT. RPM.
