En-Route Phase Flashcards
What is a drift down ceiling?
- The max altitude that can be maintained with one engine INOP when other is sex at MCT and IAS is at green dot
- Does not necessarily mean the aircraft is drifting down if the engine failure occurs at a low altitude it can be a climb
What is gross drift down flight path vs net drift down flight path? What is the reduction/buffer for a twin?
Gross: Actual path followed by a/c after engine failure
Net: Gross flight path minus a mandatory reduction
1.1% reduction
What is the time limitation for a twin aircraft for a departure alternate? What conditions?
1 hour at 1 engine INOP cruise speed
Still air
What lateral deviation must be accounted for when conducting obstacle surveys? FAA vs JAR?
FAA: 5 STATUTE miles always
JAR: 10nm unless a/c can meet RNAV 95% requirement then it becomes 5nm
What vertical clearance shall be considered when determining if a route is suitable? How should en-route net flight path be determined and the effect of ice?
-margin between the net flight path and obstructions
- Net fp: from aircraft flight manual, with account for prevailing temp and winds
- Addition consideration shall be taken if anti ice systems are expected to be used
Describe each fo the two conditions for obstacle clearance margins in the en route phase after an engine failure?
Condition 1:
-Maintain positive gradient at least 1000ft above all terrain/obstacles in the corridor
Condition 2: (If condition 1 too limiting to not possible)
- Drift down procedure determined where net flight path clears all obstacles by 2000ft between from cruise to adequate landing
- Must always be possible to escape while maintaining 2000ft vertical clearance by either Turing back, diverting or continuing
Describe the gradient of the net flight path at the aerodrome where landing is assumed to occur after engine failure? If dumping fuel able to be considered?
Net flight path must have a positive gradient at 1500ft AGL at AD of intending landing
Dumping fuel may be considered if available
Why does an aircraft have to descend to different levels after a depressurisation?
- Due to the oxygen profile of the system
- Oxygen is limited and will flow at different rates depending on altitude
What must the relationship between the oxygen profile (altitude/time or distance) relate to the aircraft performance profile?
Aircraft performance profile must always be below the oxygen profile
-If O2 can reduce flow at 10,000fpm and the aircraft can only do 8,000fpm the descent to remain below must start slightly earlier.
What sort of descent should be carried out for an emergency descent on oxygen?
- Speed is V(mo) or M(mo)
- Speed brakes can be used
What is the min flight altitude above mountainous terrain?
FAA: 2000ft within 5 sm corridor
JAR: MOCA (min obstacle clearance altitude), MEA (min safe en-route altitude), MGA (min safe grid altitude), above 10,000ft min is 2000ft above obstacles
Is a net flight path required for a cabin depressurisation?
No - only required when when there is a risk aircraft cannot maintain expected descent performance (engine failure)
In a depressurisation with all engines what is the standard descent path obstacle clearance buffer?
Descent profile must clear all obstacles by 2000ft
During route studies simultaneous engine and pressurisation failures are not considered. What must limiting profile be based on?
- The most penalising descent profile
- If possible the same critical points and escape route should be defines for both (to reduce error and complexity)
What costs does direct operating costs include?
- Fixed costs
- Flight time related costs
- Fuel consumption related costs
What is specific range? definition and equation?
-Distance covered per unit of fuel
Specific ground range = groundspeed ÷ fuel cons per hr
SGR=Gs/ff
What things will increase the specific ground range?
- Flying at a higher mach number/TAS
- Flying at a better Lift/Drag ratio
What is M(mr)? Definition?
Maximum range mach number
- min fuel cons for given distance
- max range for a given fuel quantity
What is the relationship between mach number and specific range?
-SR increases as M increase to max at M(mr) and then decreases as M increase
How does M(mr) change as weight decreases (fuel is burnt) for a given altitude? How does SR change with weight at a given altitude?
M(mr) will decrease linearly
SR will increase
How does M(mr) and SR change with increasing altitude at a given weight?
M(mr) will increase
SR will increase
What is M(LRC)? Definition?
Long-Range cruise mach number
- SR corresponds to 99% of max specific range, but offers a significantly higher cruise mach number
- By decreasing SR by 1% gives large increase in cruise mach number
How does M(LRC) change a weight decreases at a given altitude?
Decreases non linearly
What is M(Econ)? Definition?
Economic mach number
-best cruise mach number considering all direct operating costs
What is cost index? Equation?
-time and fuel cost ratio
CI = Cost of time ÷ Cost of fuel
What happens to M(Econ) if CI increases or decreases? Think about the equation
Increase CI: M(Econ) increases
Decrease CI: M(Econ) decreases
What does it mean if CI is at it maximum or minimum values? What speeds are best?
Ci Max: flight time costs are higher and fuel costs low - fly at M(mo)-0.02 or V(mo)-10kts
Ci min: flight time cost are null and/or fuel costs are high - fly at M(mr)
When flying at a fixed mach number how will fuel consumption change as weight decreases for a given altitude?
It will increase away from the optimum
When flying at constant mach, how is the aircraft operating at the optimum altitude? What is the L/D ratio
At the max lift to drag ratio for than mach number
What are the variables when an aircraft is cruising at the optimum altitude for a given mach number? remember CL is fixed and corrosponds to (CL/Cd)max
What is the equation to represent it?
Weight
Outside static pressure
Weight ÷ Static pressure = Constant
What is the relationship between weight and optimum altitude for a given mach number?
-As weight decreases optimum altitude increases
How does M(mr) and SR change with a headwind vs tailwind?
Tailwind: SR increases, M(mr) decreases
Headwind: SR decreases, M(mr) increases
*Speed changes because you want to fly in tailwind for longer and headwind for shorter time
What is the max engine limited mach number for a constant altitude and weight determined by?
The EGT
The engines have limited max cruise rating, depending on OAT.
What is the max CRUISE altitude for a given weight determined by?
The max altitude an aircraft can maintain, at max cruise thrust, when the pilot maintains a constant mach number
How does increased mach, weight and temperature affect max cruise altitude?
Increasing all will decrease max cruise altitude
What will happen to the range of available speeds at the lift ceiling? What is this sometimes called?
There is only one speed that won’t cause a mach stall or low speed stall
Also called coffin corned
How does increasing pressure altitude affect max load factor (n(max)) and lift range?
Decreases n(max) Decreases lift range
What value is the load factor buffet limit?
1.3, below load factors of 1.3 buffet should never occur
How does the buffet ceiling change as weight decreases?
1.3g buffet ceiling increases as weight decreases
Overall what is the max recommended altitude based on?
The lowest of:
- Max certified altitude
- Max cruise altitude
- 1.3g buffet limited altitude
- Climb ceiling
What percentage does the actual specific range of an aircraft vary in a stepped climb compared to one doing a cruise climb?
varies by about 1%
What are the general characteristics of an engine failure drift down procedure?
- Decelerate to green dot (an remain at green dot)
- Thrust is MCT on live engine
- Clean configuration
- Obstacle clearance is from net flight path (1000/2000ft)
- No time limit to get down
- Max altitudes single engine ceiling
What are the general characteristics of a depressurisation procedure?
- Immediate descent
- Flight idle thrust
- Fly at Vmo/Mmo
- Speed brakes deployed
- Obstacle clearance is from gross flight path
- Time limited by crew Oxygen availability
- 10,000ft/14,000ft ceiling limited by pax/crew O2
