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Cathay > Interesting Questions > Flashcards

Interesting Questions Flashcards

1
Q

Describe the drag curve and importance of Vimd

A

Vimd is the speed for max range due to minimum drag

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2
Q

What are winglets and how do they work?

A

Winglets are aerodynamic efficient surfaces located at the wing tips. They are designed to reduce induced drag. They dispense the spanwise airflow from the upper and lower surface often at different points, depending on the particular design, thus preventing the intermixing of these airflows that otherwise would create induced drag vortices.

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3
Q

What causes/are wing-tip vortices?

A

Wing-tip vortices are created by spanwise airflow over the upper and lower surfaces of a wing/aerofoil that meet at the wing tips as turbulence and therefore induce drag, especially on a swept wing.

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4
Q

If you were loading an aircraft to obtain maximum range, would you load it with a forward or aft center of gravity (forward or aft cargo hold)? An aft center of gravity position/hold

B

A

Aft C of G as this will allow a natural nose up pitching moment allowing the stabilizer to remain neutral reducing the need for downforce and reducing Induced Drag therefore increasing range

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5
Q

How does C 0f G effect VMCA?

A

Rear C of G = VMCA increases

Forward C of G = VMCA decreases

This is due to the moment arm from the C of G to the tailplane, shorter it will require more force, therefore a greater speed in order to overcome the turning moment

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6
Q

In the event of an engine failure during a crosswind which is the most favourable engine to fail?

A

DOWNWIND ENGINE

This is due to the crosswind compenent assisting the vertical stabilzer in correcting the yawing motion

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7
Q

What is SFC

A

Specific fuel consumption

Ratio of fuel burnt over engine thrust

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8
Q

What is the compression ratio of a Gas turbine engine?

A

Ratio of compressed air between the inlet and outlet of each compressor stage

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9
Q

What are the advantages of a wide cord fan engine?

A

Weight

Noise

Fuel

Thrust

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10
Q

Describle tripple spool fan engine?

A

N1 - Front turbofan (Compressor) - not restriced in size due it having its own turbine, allows increase bypass ratio (LP)

N2/3 - More efficiant as they can run at optimal performance due to each seciton having its own turbine

Higher engine thrust

Easier to start because you only need to start 1 spool

Easier maintenance as its in 3 seperate sections

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11
Q

Why do Jets fly as high as possible?

A

BEST SFC beacuse you fly at a constant MACH NO, so TAS and EAS reduce, drag is directly proportional to EAS and therefore reduces, increasing endurance leading to increased SFC

Turbine’s operate most efficiantly at high RPM 90-95% N1, this is not achievable at low altitudes due to increased air density which will over torque the engine

The higher the ALT the greater the TAS for a constant IAS therefore leading to greater RANGE

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12
Q

How does flying LRC increase range?

A

Fly at constant Mach No as altitude increases TAS decreases and therefore GS decreases and range decreases

By increasing the Mach No slightly the TAS/GS/Range will increase but this will have a negative effect on endurance

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13
Q

Why must EPR be set as quickly as possible?

A

Initial setting there will be a reduction in EPR due to lag, inlet Pressure increases and Exaust pressure remains constant

So Pilot is not chasing the RAM rise

Adequate aircract acceleration to achieve V1 and VR in the TORR (take off run required)

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14
Q

What are lines that run from Pole to Pole?

What is Departure?

A

Meridians - Lines of Longitude

Greenwich - Prime Meridian

Distance along a Paralell of Latitude other than the equator - D = change of Long x Co sin of lat

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15
Q

How Does INS work?

How does it find true North?

A

Measure’s your great circle track from the position of departure through the use of acclerometers, gyroscopes and a postion computer

By g

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16
Q

Describe GPS?

A

American satellite system for world navigation

24 minimum satellites

21 operational at one time

6 orbital planes 3-4 per plane at 55 degrees in 12 hours

4 satelites in range to obtain a fix - 3 for positon and 1 for altitude

5th satellite for RAIM

Calculates postion by time radio singals converted to a distance to obtain a fix

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17
Q

Disadvantages of GPS

A

US Military can downgrade system and accurracy

System errors - Receiver error

Clock Bias

Signal jamming

Satellite geometry

Ionispheric errors

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18
Q

How does a VOR work?

A

VHF omdi directional range

Transmits a VHF signal over 360 degrees which has an FM reference singal phases and AM varible phase signal which varies at a constant rate allowing a unique signal for each degree

108mhz-118mhz

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19
Q

What is an Isobar and Isotherm?

A

Lines of equal pressure

Lines of equal temperature

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20
Q

How are clouds formed?

A

Lifting action of air

Frontal

Orthographic (Hills/Mountains)

Convection

Turbulane

21
Q

How is cloud base calculated?

A

temperature dewpoint spilt x 410

22
Q

Different types of Fog?

A

Radiation - Convection terrestrail radiaiton

Advection - Advection warm air over cold surface

Frontal - Liftng

23
Q

Describe formation of a thunderstorm?

When is lightening most likely to occur?

A

High Moisture content, Lifting action, Adiabatic cooling, Highly unstable air

Developing, Mature and dissapating stages

+10 to -10 and in mature stage of thunderstorm

24
Q

Describr Upper Winds?

Jetstreams?

Wind direction wtih altitude?

Trade winds?

A

Caused by differential temperature at high altitude (Thermal Gradient)

Narrow bands of upper thermal winds

1500nm long, 200nm wide, 12000ft depth, greater than 60kts, CAT, speed is directly proportional to thermal gradient

Polar front Jetstream

Intertropical front Jetstream

Back in N.H and Veers in the S.H

Light winds blow from Subtropical High to Equatorical Low (ITCZ)

25
Q

Why does a warm front move slower than a cold front?

Warm and cold front winds?

A

Cold air is more dense and pushes under warm air whereas warm air has to rise above the colder air

Warm Front - Wind Veer’s N.H backs in S.H

Cold Front - Wind Veer’s N.H Backs in S.H

26
Q

Where do you find Windshear?

How do you detect windshear?

Microburst?

A

Below 3000ft, Frontal Passage, Microburst, Hills and moutains, approach over water, elevated threshold, Thunderstorms/CB clouds

Pilot reports, lydar, doppler shift, aircraft warning system associated with GPWS

Severe downgraughts and windshear found below mature CB, may not be associated with rain, last up to 10min, diameter 1-5nm, if encountered TOGO!!

27
Q

Tropical Revolving Storms

Typhoon’s, hurricanes, cyclones

What is a Typhoo ?

A

Cyclonic Storm with gale force winds (above 34kts)

Formed along the ITCZ

Form over warm oceans and need at least 27 degrees

Die out over land

Do not form on Equator as there is no Coriolis force

Unstable air mass

Convective lifting through trade winds

Typhoon season is June-October

28
Q

Monsoons

A

Seasonal change in wind direction

Basically a massive Land/Sea Breeze

Summer - April to September

Heavy rainfall, warm moist air blows from Southern eastern indian ocean

Blows from Ocean to Land

Winter - October -April

Blows from Land to Ocean

Hot and dry, less powerful, Himilaya mountains prevent wind and moisture reaching the coast

29
Q

How is Windshear detected?

A

LLWAS - Low level wind shear detetion system

Aircrafts can be fitted with a system which uses AOA, airspeed and acceleration sensors to compare aircrafts actual performance to what it should be under in existing circumstances

Lydar - Unique to Hong Kong, Doppler Radar by laser light up to 12km away from the airport

30
Q

If you increase weight what happens to descent?

A

The glide distance remains the same but an increase in weight leads to increase in lift required, leads to increase in ROD so you will get the faster

Increase weight - Start desent earlier to account for increase in ROD

31
Q

Effect of C of G on stall

A

Forward C of G increase stall speed

Due to tailplane having a greater downforce action required to maintan S and L and therefore incease the amount of weight the tail has to support leading to higher indicated airspeed required to maintain the extra lift and INCREASING the stall speed

32
Q

Factors Increase Tip Stalling?

Factors reducing tip stalling?

A

Power/slipstream on during stall re-engergising the boundary layer

Flaps increasing camber at the wing root

Swept wing aircrafts

REDUCE

Washout (incidence)

Change of aerofoil section (Camber)

Root Spoiler (disturbs airflow at root)

33
Q

Why does swept wing aircraft still at a higher AOA

A

Low aspect ration leads to increased downwash which effectively reduces the apparant angle of attack and increases stall angle

34
Q

Typers of flaps

Trailing Edge?

Leading Edge?

A

Double/Slotted Flap - Increase camber and re-engergize boundary layer

Fowler Flap - Slotted flap which increases camber, increases wing surface area and re-engergizes boundary layer

Leading edge

Slats - extend from top of wing, increase camber and slot re-engergizes wing

Drooping leading edge - The whole leading edge deploys and increases camber

Kreuger Flap - Deploys from underneath the wing…same theory as slats but The advantage is when retraced the leading edge radius is thinner and more aerodynamic for high speed flight

35
Q

Factors that reduce Adverse Aileron Yaw

Control Balancing

A
  1. Frise Ailerons (hinged to the rear so small peice is deflected into airflow creating profile drag)
  2. Differential Ailerons (upgoing deflects more)
  3. Spoilers - Deploy on upgoing wing creating drag

Control Balancing

Horn Balance - small horn sticks out in airflow creating drag

Setback hinge

Tab balance (Piper 180 on elevator)

36
Q

Varible Incidence Tailplane

A

Controlled by trim tab

By Auto pilot servo’s

Acts as a Mach Trimmer

37
Q

Mfs

Local Mach No.

Mcrit

Mdet

Mmo

Mcdr

A

Free stream mach No of the aircraft throught the air

Mach no at a particular point on the wing

The critical Mach no is where the first evidence of supersonic flow is found

Detachment Mach no is where the bow wave attaches to the leading edge (compresibility)

Critical Drag rise is observed

38
Q

Why does Cathay use the RB211 524HT engine

A

Reduced SFC by 2%

800lb weight saving per engine

Environmentally friendly

39
Q

Take off climb segments

A

1 - 35ft (Screen Height) to gear up @ V2

2 - Gear up to 400ft @ V2 - 2.4% // 1.5%

3 - Acceleration segment - 400ft to flap retraction - Level V2+30 to V2+50

4- Level off height to 1500ft at constant V2+50

40
Q

What is the Difference betweent the CFM 56 5C4 engine and the RR RB211 524HT

A

The CFM is a twin spook design where as the RB 211 is a tripple spool design

41
Q

What happens to Brake Temperatures after wheel retraction

A

Brake temperatures decrease but tyre temperatures increase due to convection

42
Q

TAT

SAT

A

Total air temperature

Static air temperature

43
Q

Why does the 747 classic not have winglets

A

The structural requirements for adding winglets large enough to be worth it in the cruise are far to great to be economically feasible

44
Q

What is the difference between an INS and an IRS?

A

An INS is a collection of components that together provide a system that is able to provide navigation computations and solutions. An IRS is different in that it is a single box that contains an Inertial Reference Unit [IRU] and a computer to produce reference information. This information is then provided to numerous other aircraft systems and displays.

45
Q

What do you know about the Trans-Polar routes Cathay Pacific is pioneering?

A

The first commercial trans polar flight [from Toronto to Hong Kong] was operated on May 18th 2000 by a Cathay A340-300, with a flying time of 14hrs 59mins.

Cathay stands to benefit a great deal from the new routes as they dramatically reduce flight times [between 2 and 3 hrs], which make them more attractive to passengers [no stop over in Anchorage].

Some problems operating at high latitudes include:

Low fuel temperature [Jet A1 freezes at around -50ºc]
Communications are solely by HF [Satcom stops working around 85ºN]
Exposure to increased levels of cosmic radiation [magnetic field]

46
Q

Iso Counter Radar

A

Weather detection, sends out pulses of radio waves which bounce back off precipitation

47
Q

Larger flap setting, how does it affect take-off roll, screen height?

A

Larger flap settings will decrease the landing roll but reduce the climb gradient

48
Q

The 3 laws of fly by wire

A

Normal - Hard Protection (Pilot cannot override)

Soft Protection - Pilot can override

Direct - Sidestick is used directly to determine position of the flight controls (No Autotrim)

49
Q

Advantages of Free Turbine

A

Greater propeller range of operating speeds

Lighter

Less drag due to no shaft or gearbox

easier to shutdown, no excess heat trapped in the hot section

Cathay (5 decks)

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