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121 Prep > Turbine > Flashcards

Turbine Flashcards

1
Q

Mach Number

A

ratio of airspeed to speed of sound

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2
Q

High Speed Buffet

A

aircraft accelerates into transonic region (.75- mach 1.2), shock wave generated on wing travels aft, causes airflow separation, ultimately this disturbed air affects horizontal stabilizer causing HIGH SPEED BUFFET

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3
Q

Mach Tuck

A

wing center of pressure moves aft as its speed approaches the sound barrier.

Farther back it moves, greater pitch down moment generated by wing –> airspeed continues to climb increaseing effects of shock wave and mach tuck

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4
Q

Critical Mach Number

A

speed at which airflow over any portion of upper wing surface becomes supersonic

(NOT A LIMITATION but simply the speed at which shock wave develops over the wing)

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5
Q

Limiting Mach Number

A

highest speed before aircraft becomes noticeably uncontrollable

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6
Q

Maximum operating speed

A

Mmo - max speed relative to speed of sound - displayed by barber pole

Pole adjusts for density & altitude

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7
Q

Coffin Corner

A

Stall speed increases as function of altitude
Mmo decreased with altitude

The two speeds converge at specified altitude creating the coffin corner

any increase leads to high speed buffet
decrease in speed results in stall buffet

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8
Q

Vne v. Mmo

A

Vne is structural limitation

Mmo is aerodynamic limitation

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9
Q

Buffet Margins

A

airspeed range between stall buffet and high speed buffet

Improve buffet margins - restrict aircraft altitude by weight

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10
Q

Swept Wing Pros & Cons

A

Pros:

  • increase Critical Mach - allows for faster flight
  • Less sensitive to turbulence
  • Increase lateral stability

Cons:

  • Produce less lift - issue at low airspeeds - addressed by use of LEDs & Trailing Edge Flaps
  • Tendency to stall tip first - addressed with aerodynamic twist in wings - wing tip lower AOA than root
  • Predisposition towards dutch roll
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11
Q

How does Swept Wing produce less drag?

A

Delays peak effects of drag to higher airspeeds

How? Reduce component of air that flows directly aft or “chordwise”

Creates Spanwise Flow - lower velocity than chordwise flow - increases critical Mach number allowing for faster flight

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12
Q

Dutch Roll

A

tendency of an aircraft to roll when it yaws

Sideslip (uncoordinated) - change wing effective wingspan - greater wing span = more lift - causes a roll - more lift means more drag on high wing - yaw towards that wing

Yaw dampers - auto rudder inputs to counteract yaw

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13
Q

Winglets

A

restricting airflow around wing tips - improve effective span of wing and therefore lift

Without winglets - air tends to flow from underwing high pressure to top wing low pressure - results in downwash –> increased drag & reduced lift

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14
Q

Tailets

A

vertical surface mounted on horizontal stabilizer

additional directional stability (especially on T-tail aircraft at low airspeeds and high AOA when airflow may be blocked by wing)

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15
Q

Vortex Generators

A

create small vortices that direct airflow to prevent airflow separation (at low and high speeds)

Can be mounted on wings, tail, elevator, engine pylon, fuselage

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16
Q

Vortilons

A

mounted on underside of wing by ailerons

basically large vortex generators designed to control turbulent airflow

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17
Q

Mmo indications

A 
barber pole (adjusts with altitude)
aural overspeed warning - often called the clacker
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18
Q

AC v. DC Power

A 
AC
Current flow changes
current can travel farther
Less expensive & lighter weight
often drive high draw items

DC
linear electrical current - constistant power delivery
general use items
some instruments require DC Power

AC to DC TRU
DC to AC Inverter
more consistent voltage

19
Q

Turbofan

A

Turbojet core with shrouded fan at front of engine
more fuel efficient, quieter

Fan - moderate acceleration to large volume of air

Highspeed/altitude advtanges of jet
Lowspeed/altitude advantages of prop

20
Q

High Bypass

A

5:1 ration

80% of thrust from bypass at low altitudes

21
Q

Normal Start

A

Start switch - ON
Engine turning- drawn through compressor section where compressed
Enter combustion chamber
10-12% N1 - fuel introduced & igniters light off
Rpm accelerates & stabilizes at normal idle speed

22
Q

Hot Start

A

Temps exceed limitations during start
too much fuel too early OR insufficient airflow
Cut off fuel supply, continue motoring

23
Q

Hung Start

A

light off occurs but engine stabilizes (hangs) at low rpms

insufficient airflow, inefficient compressions, low starter rpms

24
Q

N1

A

low pressure compressor speed

25
Q

N2

A

high pressure compressor speed

26
Q

EPR

A

Engine pressure ration- ration of exhaust to intake pressure

27
Q

EGT

A

Exhaust Gas Temperature

main engine temp guage

28
Q

TOT

A

Turbine Outlet Temp

29
Q

ITT

A

Interstate Turbine Temp

measured between compressor and power turbines

30
Q

TIT

A

Turbine Inlet Temp

31
Q

Igniters

A

spark plug like devices - light fire during starting

used during takeoff, landing, cruise in heavy precip

32
Q

Starter/Generator

A

spins engine for starting

once light off - electric motor reverts to generator

33
Q

Pneumatic Starter/ air turbine starter

A

low-pressure air motor

uses air from APU or GPU or other engine to spin starter turbine

34
Q

Bleed Air

A

tapped from engine compressor section

used for pressurixation, AC, anti-ice

35
Q

Compressor Stall

A

rotor blades fail to pass air smoothly
no longer able to force air through engine front to rear
high pressure air escapes from front & rear
occur in axial flow compressor

36
Q

Inverter

A

convert DC to AC

37
Q

AC Power

A

alternating current

used in larger jets to save weight and power loss due to long lengths of wiring

38
Q

TRU - Transformer Rectifier Unit

A

convert AC to DC

39
Q

Circuit breaker

A

automatically opens electrical circuit when an excess of current occurs

40
Q

APU

A

Auxiliary Power Unit
small gas turbine engine
supplemental source of electrical power

41
Q

Hydraulic Accumulator

A

stores hydraulic pressure

Piston Cylinder - pressurized one side with nitrogen, the other side with hydraulic pressure

42
Q

Flight Control Terminology

A

Primary - elevator, ailerons, rudder
Secondary - trim tabs
Auxiliary - wing flaps, LEDs, slats, spoilers, speed brakes

43
Q

Balanced Field Length

A

rwy needed to accelerate to V1 & stop if engine failure before V1
OR continue takeoff climb to 35 AGL if failure happens after V1

44
Q

V1

A

Decision speed - to fly or not to fly after engine failure

121 Prep (3 decks)

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