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Airplane Flying Handbook > Ch. 15 Transition To Jet Powered Airplanes > Flashcards

Ch. 15 Transition To Jet Powered Airplanes Flashcards

1
Q

How does a jet engine create thrust?

A

accelerating a relatively small mass of air to very high velocity (15-2)

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2
Q

In both jet and piston engines how is the engine cycle’s efficiency increased?

A

by increasing the volume of air taken in and the compression ratio. (15-2)

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3
Q

One of the advantages of a jet engine at higher altitudes and speeds is:

A

capability of producing much greater amounts of thrust horsepower. (15-2)

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4
Q

Turbojet efficiency increases with

A

Speed and altitude (15-2)

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5
Q

What type of engine was created to mitigate initial thrust output of the jet engine on takeoff being relatively lower and not reach peak efficiency until the higher speeds.

A

Turbofan. (15-2)

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6
Q

The part of the engine that produces the hot, high-velocity gases.

A

Gas generator. (15-2)

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7
Q

The air that after split bypasses the core.

A

Bypass air. (15-2)

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8
Q

The air that after split passes through the core.

A

Core air (15-2)

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9
Q

The amount of air that bypasses the core compared to the amount drawn into the gas generator.

A

Bypass ratio. (15-2)

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10
Q

Low-velocity bypass air produces what percentage of the thrust produced by a turbofan engine.

A

30-70%. (15-2)

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11
Q

Ratio of the fuel used by an engine and the amount of thrust it produces.

A

Specific fuel consumption. (15-3)

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12
Q

In a jet engine, thrust is determined by:

A

The amount of fuel injected into the combustion chamber. (15-3)

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13
Q

The thrust lever is linked to a fuel control and/or electronic engine computer that meters fuel flow based upon:

A

Revolutions per minute (rpm), internal temperatures, ambient conditions, and other factors. (15-3)

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14
Q

Gauge that monitors the low-pressure compressor section and/or fan speed in turbofan engines.

A

N1 (15-3)

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15
Q

The gas generator section may be monitored by what gauge?

A

N2 (15-3)

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16
Q

Each engine section rotates at many thousands of rpm. Their gauges therefore are calibrated in:

A

Percent of rpm rather than actual rpm, for ease of display and interpretation. (15-3)

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17
Q

Name the temperature of the exhaust gases as they enter the tailpipe after passing through the turbine.

A

Exhaust Gas Temperature (EGT). (15-3)

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18
Q

Name the temperature of the gases from the combustion section of the engine as they enter the first stage of the turbine.

A

TIT- turbine inlet temperature (15-4)

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19
Q

Name the highest temperature inside a gas turbine engine and is one of the limiting factors of the amount of power the engine can produce.

A

Turbine Inlet Temperature (15-4)

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20
Q

TIT is difficult to measure. What’s usually measured instead and is closely related?

A

EGT. (15-4)

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21
Q

The temperature of the gases between the high-pressure and low-pressure turbine wheels.

A

ITT- interstage turbine temperature. (15-4)

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22
Q

Name the temperature like EGT, taken aft of the turbine wheel(s).

A

TOT- turbine outlet temperature. (15-4)

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23
Q

In order to avoid the possibility of engine flameout from the above conditions, or from other conditions that might cause ingestion problems, such as heavy rain, ice, or possible bird strike, most jet engines are equipped with:

A

Continuous ignition system. (15-4)

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24
Q

Most jet engine ignition systems consist of two:

A

Ignitor plugs. (15-4)

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25
Q

Because of low temps at altitude, what are jets equipped with to prevent fuel from freezing?

A

Fuel heaters. (15-4)

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26
Q

The difference between turbine discharge pressure and engine inlet pressure. It is an indication of what the engine has done with the raw air scooped in. (can be thought of manifold pressure gauge on piston engines)

A

EPR- engine pressure ratio. (15-4)

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27
Q

What provides a secondary thrust indication, and cross-checking this can help in spotting a faulty N 1gauge.

A

Fuel flow meter. (15-5)

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28
Q

The rule is: movement of the thrust levers must be stopped and power set at whichever limits are reached first?

A

EPR, RPM, or temperature. (15-5)

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29
Q

On a jet engine, thrust is proportional to:

A

rpm (mass flow), temperature (fuel/air ratio), and further by compressor efficiency at varying RPM. (15-5)

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30
Q

Whereas piston engines normally operate in the range of 40 percent to 70 percent of available rpm, jets operate most efficiently in the

A

85 percent to 100 percent range. (15-5)

31
Q

The range from 90 percent to 100 percent in jets may produce as much thrust as the total available at:

A

70%. (15-5)

32
Q

At a low rpm, sudden fullpower application tends to over fuel the engine resulting in possible

A

Compressor surge, excessive turbine temperatures, compressor stall and/or flameout. (15-6)

33
Q

How are the problems with low rpm and sudden large power increases mitigated?

A

Various limiters, such as compressor bleed valves, are contained in the system and serve to restrict the engine until it is at an rpm at which it can respond to a rapid acceleration demand without distress. (15-6)

34
Q

Engine acceleration is initially very slow, but can change to very fast after about:

A

78 percent rpm is reached. (15-6)

35
Q

Jet powered airplanes are minus two assets that a propeller powered airplane has by using a sudden blast of power. What are they?

A
  1. No sudden lift change.
  2. No reduction in stall speed.

(15-7)

36
Q

If an increasing sink rate develops in a jet, the pilot must remember two points in the proper sequence:

A
  1. Increased lift can be gained only by accelerating airflow over the wings, and this can be accomplished only by accelerating the entire airplane.
  2. The airplane can be accelerated, assuming altitude loss cannot be afforded, only by a rapid increase in thrust, and here, the slow acceleration of the jet engine (possibly up to 8 seconds) becomes a factor.

(15-7)

37
Q

The main advantage of when a jet is reduced to idle is that the jet pilot is no longer faced with a:

A

potential drag penalty of a runaway propeller or a reversed propeller. (15-7)

38
Q

The disadvantage of reducing a jet to idle is:

A

The “freewheeling” effect forward thrust at idle has on the jet. (15-7)

39
Q

maximum operating speed expressed in terms of knots.

A

Vmo. (15-7)

40
Q

maximum operating speed expressed in terms of a decimal of Mach speed.

A

Mmo. (15-7)

41
Q

What is the problem with exceeding Vmo or Mmo?

A

The handling qualities in a jet can change drastically when the maximum operating speeds are exceeded. (15-7)

42
Q

The Mach speed at which some portion of the airflow over the wing first equals Mach 1.0 is termed:

A

Mcr- Critical Mach number. (15-8)

43
Q

What is the primary indication of thrust on most turbofan engines?

A

Fan speed (N1). (15-5)

44
Q

As rpm increases, mass flow, temperature, and efficiency also:

A

Increase. (15-5)

45
Q

Flight idle rpm is usually what percent N1?

A

50-60% (15-5)

46
Q

What happens to specific fuel consumption of jet engines as the outside air temperature decreases for constant engine rpm and TAS?

A

Decreases (15-6)

47
Q

Why are jet engines typically operated at higher altitudes?

A

Cruise is usually very close to RPM or EGT limits. (15-6)

48
Q

What causes the nose-down tendency or “tuck” near Vmo?

A

With increased speed and aft movement of the shock wave, the wing’s center of pressure also moves aft, causing the nose-down tendency. (15-8)

49
Q

What is the term for when the center of pressure moves so far aft that there is no longer enough elevator authority available to counteract it, and the airplane can enter a steep, sometimes unrecoverable dive?

A

Mach Tuck (15-9)

50
Q

The most powerful forces causing Mach Tuck are a result of what?

A

The buffeting and lack of effective downwash on the horizontal stabilizer because of the disturbed airflow over the wing. (15-9)

51
Q

What was the primary reason for developing the T-tail configuration on some jet airplanes?

A

To place the horizontal stabilizer as far as practical from the turbulence of the wings. (15-9)

52
Q

What should be the response to an overspeed condition?

A

Immediately slow the airplane by reducing power to flight idle, and slightly raise the pitch attitude to help dissipate speed. (15-9)

53
Q

Can you use speed brakes to help slow down from overspeeding?

A

Yes. However, if the nose-down stick forces have progressed to the extent that they are excessive, speed brakes will tend to aggravate the nose-down tendency. (15-9)

54
Q

A last resort option for slowing down would be to do what?

A

Extend the landing gear. (15-9)

55
Q

The most likely situations that could cause the low-speed buffet would be when?

A

When an airplane is flown at too slow of a speed for its weight and altitude, causing a high AOA. (15-9)

56
Q

What has the greatest effect on inducing the Mach buffet?

A

AOA. (15-10)

57
Q

The point where the high-speed Mach indicated airspeed and low-speed buffet boundary indicated airspeed merge is the airplane’s what?

A

Absolute or aerodynamic ceiling. (15-10)

58
Q

The envelope where if an airplane flew any slower it would exceed its stalling AOA and experience low-speed buffet, and if it flew any faster it would exceed Mmo?

A

Coffin Corner. (15-10)

59
Q

How does increasing weight or load factor affect low-speed buffet speed?

A

Increase it. (15-10)

60
Q

How does increasing weight or load factor affect high-speed buffet speed?

A

Decreases it. (15-10)

61
Q

The speed that gives the greatest margin between high and low-speed buffets, and may be considerably higher than design maneuvering speed.

A

Gust Penetration speed. (15-10)

62
Q

As a jet is slowed toward its minimum drag speed (Vmx or L/Dmax), total drag increases at a much greater rate than changes in lift, resulting in:

A

A sinking flightpath. (15-10)

63
Q

What are two ways that sink rate can be arrested?

A
  1. Pitch attitude reduced to reduce AOA and accelerate above Vmd.
  2. Thrust increased to accelerate airplane to a speed above Vmd.
    (15-11)
64
Q

In a jet airplane, where is the flight area of Vmd?

A

1.5-1.6Vs. (15-11)

65
Q

What is the problem in a jet of getting below Vmd?

A

Lack of speed stability- decrease in speed leads to an increase in drag which leads to a further decrease in speed and hence speed divergence. (15-11)

66
Q

What are the two main differences in stall characteristics between a straight wing/low tailplane (non T-tail) and a sweptwing T-tail?

A
  1. Basic pitching tendency of the airplane at a stall.

2. Tail effectiveness in stall recovery.
15-11

67
Q

Why is there a nose-up pitch tendency with a T-tail stall?

A

Spanwise airflow of the sweptwing causes the tips to stall first. This causes the center of lift to move forward, causing a nose up pitch. (15-13)

68
Q

Why does can the tail lose effectiveness in a stall on a T-tail plane?

A

The T-tail can become immersed in the wing wake reducing its effectiveness. Also, if the AOA increases further, the slow air behind the wing may sweep across the tail and the tail itself could stall. (15-13)

69
Q

Why can a T-tail bring itself into a deeper stall?

A

Near the critical-AOA the tail is still out of the wake behind the wings, maintaining effectiveness. This allows the plane to pitch up to higher AOA at the stall. (15-13)

70
Q

Proper stall recovery

A
  1. nose-down input (until stall warning stops)
  2. Wings rolled level
  3. Adjusting the thrust for normal flight
    (15-14)
71
Q

The primary purpose of spoilers

A

Spoil lift. (15-15)

72
Q

What is the real value of spoilers on landing?

A

Transferring the weight from the wings to the wheels for braking. (15-15)

73
Q

The primary purpose of speed brakes

A

Produce drag. (15-15)

Airplane Flying Handbook (9 decks)

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