M15.3 Flashcards
What is total head pressure?
Pressure of the air when brought to rest in front of the wing and intakes
Where does air enter from?
The engine air intake
What is it called when an inlet duct gets wider?
A divergent duct
What does having a divergent duct do to the airflow?
The static pressure increases (Bernoulli’s principle)
Why does air need to be smooth when entering the engine?
To be as efficient as it can
What can cause air disturbance?
Damage inlet, damaged nose, ice build up, crosswinds at low speeds
What is the first component of the gas turbine to contribute to generation of thrust?
The air inlet duct
What should the air velocity be at the compressor inlet?
Mach 0.4-0.7
What are air inlets designed to do?
Decelerate the airflow by converting kinetic energy to pressure energy
What would poor air pressure and velocity distribution result in?
A compressor stall
What may air from behind the intake lip suffer from?
Flow separation due to extreme local acceleration
How would you reduce the risk of flow separation at the intake lip?
Have well rounded intake lips
What are blow-away jets used for?
To blow away vortexes in front of the engine
How would you overcome crosswind?
You would restrict from applying full power until a specific speed is reached
What speed range is pitot type intake used for?
Low supersonic 1.5 Mach
What is critical condition?
When the intake cross section must be efficient for maximum airflow
What are the three types of shock waves at supersonic inlet ducts?
- normal or perpendicular
- oblique
- bow wave
What does most of the energy turn into on a normal shockwave?
Unusable heat
What speed range does a normal shockwave happen?
Low supersonic
When would a oblique shockwave happen?
When the airflow is forced to change direction
When a oblique shockwave happens how fast is the air going after the wave?
Supersonic
When would a bow shockwave occur?
If the speed drops or flow deviation exceeds a maximum angle
When would a normal shock diffuser inlet be used?
At low supersonic speeds where the normal sock wave isn’t too strong
How does a oblique shock inlet work?
It uses oblique shockwaves before using a normal shockwave
How does a multiple oblique shock inlet work?
It uses multiple oblique shock waves
Why are small shockwaves used in front of large ones?
To waste less energy and have a high pressure recovery
How does a variable supersonic inlet work?
It’s a equipped with an actuator operated panel to change the number of shock waves
What happens when a variable supersonic inlet is at a flight speed below Mach 1?
It will be fully open with a high angle of attack
What happens when a variable supersonic inlet is at a flight speed above Mach 1?
It will operate the panel actuated to adjust angles to get multiple shock waves
What happens when a variable supersonic inlet is at a flight speed of Mach 1?
It only produces a single normal shockwave
What two problems does ice cause on the inlet?
Flow distribution and pieces of ice going in the engine
What would tell you the operating conditions in cold icy weather?
The maintenance manual
What is the most common type of ice protection?
Thermal systems
What is the thermal system for ice protection split into?
Bleed air and electrical heating
Which heating sub-system can do the nose spinner?
Bleed air
What can be used to protect the nose spinner from ice build up?
- bleed air
- hot oil
- rubber spike
When would bleed air be used for ice protection?
It’s used on engines with high mass airflow
Where does the bleed air for ice protection come from?
The high pressure compressor which gets passed through the pressure regulations bleed valves
If bleed air is used in the nose cone where does the air go afterwards?
Either overboard or into the low pressure compressor
What does pressing the engine anti-icing switch energies?
The thermal anti-icing valve
What does the engine anti-ice system use?
Pneumatic air or bleed air
What part of the structure does the anti-ice system protect?
The leading edge of the wing
Where is electrical ice protection normally used?
On turbo-prop engines
What type of flow would the electrical ice protection come in?
AC and DC
How many amps is used in the continuous electrical ice protection?
18 amps
How many amps is used for the cycling electrical ice protection?
29 amps
What determines fast or slow on the electrical ice protection system?
The outside air temperature
At what temperatures would you select fast cycle on the electrical ice protection system?
Between -6C and +10C
At what temperatures would you select slow cycle on the electrical ice protection system?
Below -6C
How is cycling from the electrical ice protection system indicated?
A light will be glowing bright then dim
How would over heating be indicated on a heater mat?
Splits, wrinkling, tears, and discolouration
