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Heavy Aircraft Performance > Enroute Limitations and Cruise > Flashcards

Enroute Limitations and Cruise Flashcards

1
Q

What is the standard procedure for engine failure over mountainous terrain during climb or cruise?
Explain this procedure?

A

DRIFT DOWN procedure;
CONTROL aeroplane;
Selecting MCT on remaining ENGINES;
DECELERATING to GREEN DOT SPEED (BEST L/D);
CLIMBING or DESCENDING at GREEN DOT SPEED until reaching DRIFT DOWN CEILING (LEVEL OFF)

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2
Q

What is the definition of gross drift down flight path?

What are the conditions of it?

A

ACTUAL PATH flown after ENGINE FAILURE must be determined at any selected speed with MOST UNFAVOURABLE CoG (FORWARD due to DRAG) and CRITICAL ENGINE INOPERATIVE

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3
Q

What is the definition of net drift down flight path?

What are the conditions of it?

A

GROSS path MINUS a MANDATORY REDUCTION;
2 ENGINE: 1.1% for 1 ENGINE OUT;
4 ENGINE: 1.6% for 1 ENGINE OUT and 0.5% for 2

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4
Q

With an engine failure in the takeoff phase and landing requirements not met at the departure airport what are the minimum requirements for that aeroplane?

A

2 ENGINE: 1 HOUR FLIGHT time at 1 ENGINE INOPERATIVE CRUISING SPEED in STILL AIR;
4 ENGINE: 2 HOUR FLIGHT time at 1 ENGINE INOPERATIVE CRUISING SPEED in STILL AIR

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5
Q

During an enroute phase with one engine inoperative what lateral clearance must the aeroplane maintain from terrain?

A

JAR: 2 and 4 ENGINE EITHER SIDE 5nm or 10nm if NAV ACCURACY does NOT meet 95% CONTAINMENT LEVEL;
FAR: EITHER SIDE 5sm

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6
Q

During an enroute phase with one engine inoperative what vertical clearance must the aeroplane maintain from terrain?

A

The GRADIENT of NET path must be POSITIVE at atleast 1000ft ABOVE ALL TERRAIN and OBSTRUCTIONS;
If this CANNOT be met due to WEIGHT NET path must allow cruise to AERODROME where landing can be made, CLEARING TERRAIN and OBSTRUCTIONS by AT LEAST 2000ft

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7
Q

What options must always be available at the most critical area enroute?

A

TURN BACK, DIVERT or CONTINUE;

Either option must ensure AT LEAST 200ft CLEARANCE from TERRAIN/OBSTRUCTIONS

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8
Q

If an alternate is selected during enroute phase, what performance and runway conditions must it meet for landing to be made?

A

Net path have POSITIVE GRADIENT at 1500ft ABOVE AERODROME;
PERFORMANCE requirements AT EXPECTED landing MASS are met;
WEATHER REPORTS/FORECASTS or COMBINATION and FIELD CONDITION reports INDICATE SAFE LANDING can be made at ETA ie: Weather MINIMA for approach CAT

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9
Q

For aeroplanes with 4 engines inoperative what is the enroute vertical clearance and performance requirements when diverting to another aerodrome?

A

NET path CLEAR of TERRAIN/OBSTRUCTIONS within route corridor by AT LEAST 2000ft;
Net path have POSITIVE GRADIENT at 1500ft ABOVE AERODROME

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10
Q

What is the altitude limit for a pressurised aeroplane?

How can this limit be extended?

A

10000ft;

SUPPLEMENTAL OXYGEN equipment is provided

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11
Q

What is the assumption that is made following a cabin pressurisation failure?

A

CABIN PRESSURE ALTITUDE is the SAME as AIRCRAFTS PRESSURE ALTITUDE UNLESS it can be DEMONSTRATED UNLIKELY

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12
Q

How is the descent profile determined following a pressurisation failure?

A

The aeroplane is limited by the OXYGEN PROFILE therefore the PERFORMANCE profile must remain BELOW it;
The PERFORMANCE profile CANNOT match the OXYGEN profile so will remain below by ASSUMING EMERGENCY DESCENT can be made at Mmo/Vmo with AIRBRAKES EXTENDED to INCREASE RoD and CRUISES at MAX SPEED (limited to Vmo)

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13
Q

`What are the lateral and vertical clearance limits for IFR in designated mountainous zones?

A

2000ft ABOVE HIGHEST OBSTACLE, within 5nm from CENTRE of intended ROUTE

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14
Q

What are the vertical clearance limits for a cabin pressurisation failure?

A

DESCENT PROFILE must CLEAR any OBSTACLE by 2000ft;

A NET path is NOT REQUIRED as the aeroplane can fly without problems as ALL ENGINES are still OPERATIVE

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15
Q

For the purpose of planning where are failures expected to occur?

A

At the MOST CRITICAL POINT

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16
Q

What are the equations for specific ground and air range?

A

SR (GROUND) = GS/FF(kg/hr)

SR (AIR) = TAS/FF

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17
Q

What are the 3 main factors that determine specific range?
How does an increase in each of them affect specific range?
What is the equation?

A 
SR = (ao x AREDYNAMICS)/(ENGINE x WEIGHT);
INCREASE AERODYNAMICS (MACH x L/D) INCREASES SR;
INCREASE ENGINE (SFC/√T/T0) DECREASES SR;
INCREASE WEIGHT (m x g) DECREASES SR
18
Q

What is the advantage of a Mach number at a given weight and altitude that gives a max specific range?
What is it called?

A

MAX RANGE MACH number Mmr;

Gives MAX DISTANCE for given FUEL QUANTITY;

19
Q

How does Mmr change over the course of the flight when altitude is kept constant? DRAW
How does Mmr change when weight is kept constant? DRAW

A

WEIGHT of aeroplane DECREASES as FUEL is BURNT causing SR INCREASE but Mmr DECREASES and must change throughout flight;
PRESSURE ALTITUDE INCREASE causes INCREASE in Mmr

20
Q

How do we achieve greater economic efficiency over a long flight in regards to specific range?

A

LONG RANGE CRUISE MACH number Mlrc;

For a 1% DECRESE from MAX SR a much GREATER Mach number may be achieved which compensates for the decrease

21
Q

How does Mlrc change over the course of the flight when altitude is kept constant? DRAW
How does Mlrc change when weight is kept constant? DRAW

A

DECREASE in WEIGHT causes DECREASE in Mlrc;

INCREASE in PRESSURE ALTITUDE causes INCREASE in Mlrc

22
Q

How do we achieve a minimum direct operating cost?

What is the equation for DOC?

A

ECONOMIC MACH number;
DOC = FIXED Costs (Cc) + (Cost of FUEL UNIT (Cf) x TRIP FUEL (△F)) + (TIME related COSTS per FLIGHT HOUR (Ct) x TRIP TIME (△T)

23
Q

How does Mecon change over the course of the flight when altitude is kept constant?
How does Mecon change when weight is kept constant?

A

DECREASE in WEIGHT causes DECREASE in Mecon;

INCREASE in PRESSURE ALTITUDE causes INCREASE in Mecon

24
Q

What is the Mecon value mainly dependant on?

How does it relate to this? Use equations?

A

COST INDEX;
INCREASE CI, INCREASES Mecon;
CI = Cost of TIME/Cost of FUEL

25
Q

What are the 2 extreme values of CI?

What does this mean for the speeds that are used?

A 
CI = 0: Flight TIME costs are NULL so Mecon = Mmr;
CI = MAX: Flight TIME costs are HIGH and FUEL costs are LOW so Mecon = MAX SPEED ie: Mmo - 0.02 or Vmo - 10kts
26
Q

What does it mean if a cost index is 30 kg/min?

A

Cost of 1 FLIGHT MINUTE is SAME as cost of 30kg of FUEL

27
Q

Why do we not fly at a constant Mach number at a given altitude?

A

As WEIGHT DECREASES the MOST EFFICIENT MACH number DECREASES for a given ALTITUDE this will INCREASE the GAP between Mmr and FUEL CONSUMPTION is beyond OPTIMUM

28
Q

To fly at a constant Mach number what must happen?
Does having a greater constant Mach change anything?
Include any relevant equations?

A

The OPTIMUM ALTITUDE must be flown which INCREASES with DECREASE in WEIGHT, it is flown at the MAX L/D for the selected MACH number;
INCREASING MACH DECREASES MAX L/D;
WEIGHT/Ps = CONSTANT

29
Q

For a given pressure altitude how does a decrease in weight change optimum altitude and specific range?

A

INCREASES OPTIMUM ALTITUDE;

INCREASES SR

30
Q

How does wind affect specific ground range and Mmr for a given altitude and weight?

A

TAILWIND: INCREASES SR(ground), DECREASES Mmr;
HEADWIND: DECREASES SR(ground), INCREASES Mmr

31
Q

Is there ever circumstances when there is a better altitude to fly at other than the ‘optimum altitude’

A

Usually LOWER altitude DECREASES SR, when there is a FAVOURABLE WIND at a LOWER altitude SR may INCREASE

32
Q

What mach number is an aerolane limited to when considering the limited max cruise rating at a given altitude?
How does this change with temperature and weight?

A

LIMIT MACH number which depends on MAX TEMPERATURE the TURBINES can sustain;
CONSTANT WEIGHT and INCREASING TEMP: DECREASE LIMIT MACH
CONSTANT TEMP and INCREASING WEIGHT: DECREASE LIMIT MACH

33
Q

What is the definition of maximum cruise altitude?

How does it change with an increase in each of weight, temperature and mach number?

A

For a GIVEN WEIGHT is the MAX ALTITUDE aeroplane can MAINTAIN at MAX CRUISE THRUST when MAINTAINING FIXED MACH number;
DECREASES with ALL 3

34
Q

What is the definition of the lift limit?

What is the equation?

A

When CL = CL MAX, any INCREASE in AoA causes STALL;

mg = 0.7 x S x Ps x CLmax x M^2

35
Q

What does the lift range graph show? DRAW

A

CLmax x M^2 (Ps or PA) vs MACH number
FLYABLE AREA for a given WEIGHT at any ALTITUDE up to LIFT CEILING where a DECREASE in MACH will cause SEPARATION STALL and an INCREASE in MACH will cause SHOCK STALL

36
Q

What are the equations associated with load factor?
What does the buffet limit graph show? DRAW
What is the relationship between values when n = n max?

A

n = L/W
n = 1/(cos(Bank angle))
FLYABLE AREA for a given WEIGHT and PA at any LF up to MAX LF where a DECREASE/INCREASE in MACH outside of curve will cause a BUFFET;
Mmin = Mmax

37
Q

How does an increase in pressure altitude change n max and lift range?

A

DECREASES BOTH

38
Q

In order to maintain minimum margin against buffeting what must be established?
How does this change with an increase in weight?

A

OPERATING limitation of LOAD FACTOR LIMIT generally 1.3 ie: ALTITUDE where it is possible to bear 1.3g LOAD;
Called 1.3g BUFFET LIMITED altitude or BUFFET CEILING;
BUFFET CEILING DECREASES

39
Q

What factors determine the maximum recommended altitude?

A 
The LOWEST of:
MAX CERTIFIED altitude;
MAX CRUISE altitude;
1,3g BUFFET LIMITED altitude;
CLIMB CEILING
40
Q

What is a step climb?

Why is this preferable for cruise?

A

When WEIGHT DECREASES, OPTIMUM altitude INCREASES so the aeroplane must CLIMB in order to maintain an OPTIMUM CRUISING LEVEL;
ATC do NOT allow CONTINUOUS CLIMB so aeroplane must fly SEGMENTS CLOSE to OPTIMUM usually +/- 2000ft gives SR >/= 0.99SRmax;
To comply aeroplanes CLIMB in steps of 2000ft in RVSM or UNDER FL290 and 4000ft ABOVE FL290

Heavy Aircraft Performance (7 decks)

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