Lecture 24 Flashcards
What fuel was used in turbine engines in early days?
Why was it an issue?
Kerosene
Difficult cold-weather starting (primary issue with straight kerosene)
What fuel is used in turbine engines today?
Kerosene Type Fuel (additives blended into kerosene)
Blended Type Fuel (gas and kerosene)
What is the freeze point of Jet A fuel? How about Jet A-1?
Is Jet A fuel interchangeable with Jet A-1 fuel?
Jet A starts to freeze at -40°F
Jet A-1 starts to freeze at -58°F (same freeze point as avgas)
In a Jet A engine, you can use Jet A-1
In a Jet A-1 engine, you cannot use Jet A
What is the freeze point of Jet B fuel?
What is it a combination of?
Jet B starts to freeze at -60°F
Combo of Jet A and AVGAS
How much does kerosene weigh per gallon?
How much does avgas weigh per gallon?
6.7 pounds per gallon (required weight)
Aviation gasoline weighs 6 pounds per gallon (average, there is no required weight)
Can you use avgas when turbine fuel is not available?*
Should you use avgas all the time?*
Yes
No
Tetraethyl Lead (TEL) in AVGAS causes deposits to form on the turbine blades
Avgas does not lubricate as well as kerosene and causes excessive wear
Why does jet fuel viscosity cause issues?*
Jet fuel is more viscous than gasoline causing contaminants and water to take a long time to settle
What is scum?*
How can you prevent it?
Microscopic organisms living and multiplying at the interface between water and fuel
Additives such as Prist or other biocides to help prevent scum NOT remedy it
What additional precautions are taken with jet fuel to avoid microbial growth?
Protection against water contamination
-Fuel storage facilities
-Fuel delivery trucks
-Underground fuel hydrants
Fire Hazard
-Static Electricity produced as fuel flows at a high rate
-Fuel truck and delivery hose must be grounded
-Aircraft structure must be connected to the fuel hose with a low-resistance ground wire
What is the function of turbine engine fuel systems?
Under all operating conditions, provide the fuel control with the correct amount of clean fuel, free from vapor and at the correct pressure
What are the components of the fuel system?
Fuel Pumps
Fuel Strainers
Fuel Controls: Hydro-mechanical (older) and FADEC (newer)
Fuel Flowmeter
Fuel-Oil Heat Exchanger
Fuel Nozzles
Pressurizing and Dump Valve
What do fuel nozzles do?*
What are the two types?
What type of nozzles is more commonly used?
Atomize the fuel at the end of the fuel system to mix with air and form a combustible mixture
Simplex
Duplex
Atomizing nozzles
What is the equivalent of a throttle in a turbine engine?
Thrust lever
Why is it bad to be a “throttle jockey” in a turbine engine?
In a piston engine, throttle is instantaneous
In a turbine engine, you have to wait for thrust lever input to take effect
What are the two types of fuel control?
Which are you more likely to encounter?
Hydro-mechanical type (old)
Electronic type
Electronic
What is FADEC?
How does it control engine power?
Full-Authority Digital Electronic Control (FADEC)
Controls all engine functions and eliminates the need for a backup hydro-mechanical control
Controls engine power through direct control of the EPR (Engine Pressure Ratio)
What are the advantages of FADEC?
No manual engine adjustments or tuning required
Improved engine starts
Constant idle speed
Saves fuel
Automatically limits critical engine pressures and speeds, reducing wear and possible damage
What happens if both channels of FADEC fail?
All actuator motors are spring loaded to fail-safe positions
Fuel flow goes to minimum flow
Stator vanes will fully open
Air-oil cooler will fully open
ACC will shut off
What is BITE?
How can an issue be identified by utilizing BITE?
Built-in test equipment (BITE)
FADEC uses it to perform self-test routines
Detects and isolates faults
Use a maintenance monitor to turn fault codes into English messages and identify the faulty line-replaceable unit (LRU)
