ATK Flashcards
- At ISA -9 what will your altimeter read:
a. Over read. Note: Pressure is lower due to the lower temperature so the altimeter will be over reading
- What happens to the ETP if you have a headwind component on the outbound leg?
a. The ETP will move towards the aerodrome of destination.
The position of the ETP will always move into wind, away from the mid point.
- What is EAS corrected for?
a. Indicated
Position/pressure
Calibrated
Compressibility
Equivalent
Density
True
- What happens to the difference between IAS and TAS with an increase in altitude?
a. Increase
- Equivalent still air distance formula
ESAD (nm)=Total dist/GS x TAS
(Think of the V=d/t formula. Time is represented by GS x TAS)
- What happens to TAS if climbing at a constant M. no.?
a. If an aircraft maintains Mach number, TAS reduces when an aircraft climbs. This is because air density (and consequently, the speed of sound) decreases with altitude. Therefore, Mach number, being the same part of a now lower value, is reached.
- If you climb at a constant IAS, your limiting speed will eventually be
c. MMO, Limiting mach number.
Maximum Mach Number (MMO): Preventing Your Wing From Going Supersonic.
As you climb, the true airspeed to reach MMO decreases. In sub-sonic jets, MMO prevents you from reaching your critical mach number. That’s the speed where some air flowing over your wings begins traveling at the speed of sound.
- Aircraft maintains a constant IAS in the climb, what happens to TAS & LSS (Local speed of sound)?
a. Constant IAS – TAS will increase & LSS will decrease
- How does temperature affect the speed of sound?
a. The speed of sound is directly proportional to the square root of the absolute temperature (the speed of sound will increase with an increase in temperature).
LSS = 38.94√K
At sea level ISA: LSS = 661kts.
At 35,000’ ISA: LSS = 575kts.
- Airspeed in the climb – at a constant TAS / IAS / Mach No. what do each do?
a. Constant IAS – Both TAS & Mach No. increase
Constant Mach No – Both IAS & TAS decrease
Constant TAS – Mach No. increases, IAS decreases
- Cruise Mach No. is more limiting when
The higher the aircraft flies
- What happens to the speed of sound with altitude / temperature
a. LSS reduces with altitude and with cooling temperatures
- What errors does a Mach Meter NOT suffer from?
a. Density error & Compressibility error.
- The two capsules in a Mach Meter are what?
a. Airspeed
Altitude calibration.
- MFS is
b. Free stream Mach number – airflow unaffected by the aircraft
- Ml is
a. Local Mach number – is the speed of air relative to the Local Speed of Sound measured at a point on the aircraft
- In a single spool turbine, what is the RPM compared to turbine speed?
a. Same
- In a single spool turbine engine, the speed of the compressor and turbine rotate at?
a. Same speed as turbine
- Compressor stall / surge is
a. A reverse flow of air through the engine caused by unstable air
- Symptom of compressor surge
d. An engine popping or banging noise and/or vibration
Rapidly rising turbine temperature
Fluctuating engine rpm,
Fluctuating fuel flow,
Engine thrust will rapidly decrease.
- What does N1 mean?
a. “N” followed by a number is the rotational speed and number in the sequence of a spool.
- What does TOT mean?
a. Turbine outlet temperature
- What does ITT mean?
a. Interstage turbine temperature
- What does TET or TIT mean?
a. Turbine entry temperature, turbine inlet temperature.
Regarding turbine engines, the LP compressor is connected to the …?
a. The LP compressor is connected to the LP turbine (fan)
- On a 3 spool gas turbine engine, the N1 is referred to as the;
a. RPM of the low pressure compressor fan.
- What is the advantage of the 3 spool engine?
It has greater efficiency over a wider range of operating conditions.
Each spool can be rotated at its optimum design speed. It is also less noisy and easier to start.
The front spool sections rotate slower and thus achieve better reliability.
Improved stall/surge characteristics, better response, more exact rpm control, and higher compression ratios.
- What are the symptoms of a hung start?
Engine rpm does not increase at a normal rate, and/or engine fails to reach idle rpm.
You will see an EGT (exhaust gas temp) rise, but the rpm will hang.
A hung start is normally due to a start generator malfunction, such as cutting too early, to insufficient fuel flow, or to some malfunction of the compressor inlet guide vanes or bleed valves, leading to excessive back pressure through the compressor stages.
- A constant speed drive does what?
a. Mechanical gearbox that takes an input shaft rotating at a wide range of speeds, delivering this power to an output shaft that rotates at a constant speed, despite the varying input. Keeps electrical output at X amount and constantly despite varying input rpm.
A CSD runs off the accessory case and drives the AC generator at a constant RPM regardless of engine RPM. CSDs ensure that all generators are producing acceptable outputs of constant frequency, voltage, and phase, and allows each generator to be paralleled and to share the aircraft’s electrical load.
- What is bypass ratio?
a. It is the ratio of air that does not enter the turbine section of the engine to the ratio that does. I.e, if 10 parts of air does not enter the engine and 1 part does, the engine has a 10:1 bypass ratio.
- Why are high bypass engines more efficient then low bypass engines?
High bypass engines moves a large mass of air and accelerates it to a reasonably high speed. This is most efficient up to quite high mach numbers.
Low bypass engines move a smaller amount of air but accelerate it to a lot high speed. This is only efficient at very high mach numbers.
The high bypass engine is thus more efficient and achieves a lower Specific Fuel Consumption (lb of fuel / lb of thrust / per hour)
Also high bypass engines are less noisy.
- Engine bleed air has what effect?
a. EPR decreases (engine pressure ratio)
EGT increases
Thrust decreases
- What is cabin differential pressure?
a. Difference between ambient pressure and cabin pressure
- If an aircraft is cruising at FL300 and the Cabin Altitude is increased from 4000ft to 6000ft. What is the effect on pressure differential?
a. Decreases
- Cabin pressure is controlled by?
a. Outflow valve.
Airplanes control their cabin pressure via an outflow valve. This valve helps keep the incoming air inside the cabin and then releases it at a rate that is regulated by pressure controllers.
- Cabin pressure reaches max differential, what happens if the aircraft climbs?
a. The cabin will climb
- ASI requires what input?
a. Pitot and static
- If you are in a climb and your static ports become blocked, what will your altimeter do
P S
C O U
D U O
a. Under read
- Pitot tube is blocked in cruise, aircraft enters a descent what happens to ASI
P S
C O U
D U O
a. under read
- Blocked pitot tube on your ASI in the climb, will it overread or underread
P S
C O U
D U O
a. ASI will over read
- What is Gyro wander?
a. Due to the gyros rigidity, the spin axis of a perfect gyro should continue in a fixed direction. Any movement away from this direction is known as gyro wander.
- What is real wander?
a. Is the wander caused by the movement of the spin axis due to imperfections and friction
- What is apparent wander?
a. Is due to the apparent movement of the gyro axis due to the rotation of the earth. Corrected for by a drift nut/latitude rider.
- What is a space gyro
a. Free to move in all planes
- What is a tied gyro
a. A space gyro with freedom of movement in three planes, but tied to one reference. Used in the direction indicator.
- What is an earth gyro?
a. Spin axis is perpendicular to horizon. Used in artificial horizon
- What is a rate gyro?
a. Freedom of movement in only one plane, used in turn coordinator
- How is hydraulic fluid pressurised (I don’t recall this being on cram)
?
- What is the function of a hydraulic accumulator?
a. To store hydraulic fluid under pressure