PERFORMANCE Flashcards
Cruise ceiling
Altitude at which the max rate of climb capability at max continuous power and best CLB speed is 300ft per min
Service ceiling
Altitude at which max rate of climb capability at max continuous power and best climb speed is 100ft per min
VT/VF
Specific range. Is TAS/Total FF, OR nm per pound of fuel
VT/VF MAX
The max Value of specific range for a given weight & altitude
99% VT/VF MAX
The value of specific range resulting from increasing TAS from the speed at VT/VF MAX, to give a value of specific range which is 1% less than VT/VF max
Long range cruise
Term that identifies flight at the speed of 99% VT/VF MAX
VH
Structurally limited max level flight speed (recommended limit speed)
Normal bleed
When compressor bleed air is used to operate the aircon & pressurisation system
(800”lbs extra TQ)
All bleed
When compressor bleed air is used to operate the engine & wing/tail surface anti ice systems as well as the normal bleed functions
(extra 1200”lbs)
Drag index
that is proportional to drag change asssociated with a change in aircraft configuration
What advantage do props have over jet engines
advantage in power/weight ratio over jet engines at speeds up to about 350 k
What is the general power utilization of a turboprop
Over 90% of the energy is extracted by the turbines to drive the compressor(s) and the propeller; the remaining energy appears in the jet exhaust as thrust
What are the four factors affecting power output AND specific fuel consumption
- Forward speed
- Temperature
- RPM
- altitude
How does temperature affect power output?
An increase in intake temperature = an expansion of air particles. This will reduce power output because the mass flow through the engine will be reduced due to reduced air density.
How does altitude affect power output
At a constant TAS, power output falls with increase in altitude due to the decrease in air density. This is mitigated however by a decrease in air temp = increased air density
How does forward speed affect power output?
As forward speed increases, ram effect increases air pressure at the intake, increasing power output (up to about 400kts)
Define specific fuel consumption
The measurement of fuel used/hr/kW (power)
How does RPM affect SFC
Turboprop engines are designed to operate most efficiently at Max continuous RPM. For the minimum (best) SFC, engines should be operated at this at all times
How does temperature affect SFC
SFC improves in cold air because of the increased thermal efficiency of the engine.
How does altitude affect SFC
No direct effect as fuel control unit will reduce fuel consumption as air density decreases.
How does forward speed affect SFC
Shaft power increases with speed because of the improved mass flow through the engine. The GFC will be higher overall.
Summarise the best configuration for minimum SFC (max efficiency)
a. At MCrpm.
b. At high altitude (better thermal efficiency in colder air).
c. At a TAS between 300 kt and 400 kt, so that advantage may be taken of ram effect while the
propeller efficiency is still high.
define specific air range
defined as air distance travelled per unit quantity of fuel
Power required is a product of?
TAS and drag
Where does the maximum TAS/power ratio occur?
At the minimum drag speed (Vimd)
What is power required a product of
Drag & TAS
How does altitude affect TAS/power ratio
As altitude increases, TAS increases, however the power required also increases. Thus the ratio is unaffected
How does wind affect TAS/power ratio
Should be a ground speed/power ratio
Tail wind: a speed less than Vimd can be flown
Head wind: a speed more than Vimd should be flown
What are the two reasons aircraft should be flown at a speed slightly more than Vimd
- The variation of TAS/power at speeds near VIMD is negligible and a slightly higher speed will allow a faster flight without undue loss of range.
- When flying at VIMD, any turbulence or manoeuvres will cause a loss of lift and height. which can only be regained by the application of more power and consequent fuel wastage.
Describe the conflict when flying for endurance between flying for airframe and flying for engine efficiency
- Airframe demands least power at minimum power speed,
plus about 10 kt for control, at as low an altitude as possible = minimum fuel flow. - Flying for engine efficiency: engines are most efficient at MCrpm,at a high altitude (cold temperature) and a high TAS (around 300 kt).
How to fly the aircraft for both max endurance AND engine efficiency
At a medium altitude where an airframe speed in the region of VIMD is maintained by throttling the engines
How to achieve maximum range in a turboprop
- cruise climb using MCrpm and an IAS slightly above VIMD.
During the cruise climb, SAR improves as both drag and SFC fall.
What do temps colder than ISA cause (3)
(1) The aircraft to fly higher.
(2) A slight increase in TAS.
(3) An increase in SAR.
How to achieve Maximum endurance in a turboprop
achieved at a medium altitude where the engines are throttled to produce an IAS of about VIMD.
STEP-CLIMB cruise profile (process)
Recommended step is 2000ft
1) determine AUW
2) determine cruise ceiling
3) Select desired alt below cruise ceiling
4) Use range summary charts to get cruise speed, FF & TQ
5) Set recommended power & adjust as AUW decreases.
what to do if HWC is >70kts
increase TAS by 4kts for every 10kts above 70.
What is driftdown
due to failure of 1 or 2 engines, it may be necessary due to loss of power, to descend to a lower alt.
What is the driftdown procedure
1) maintain the recommended driftdown airspeed until ROD decreases to 100FPM.
2) maintain 100FPM ROD until reaching service ceiling altitude (= max height for terrain clearance with some sacrifice in range)
OR until reaching cruise ceiling.
What are the 5 climb speeds & when would you use them
1) Normal speeds (not international & fuel not critical, good to reduce floor angle)
2) Four engine climb speeds: when a/c is climbing to cruise alt/for oceanic legs
3) High speed climb (medium heights/is light - 210kts)
4) Max angle
5) Best RoC
When is a climb possible?
- Once the engines have been throttled back to 930 deg
- Or if employing 970deg cruise, once TAS has increased to 304kts
Cruise climb procedure?
- Once at cruise ceiling, request a block from ATC
- Set 970deg or 1010 & maintain LRC speed
- Accept a constant climb
Long range cruise - when would you use it?
- when fuel becomes a consideration
When using LRC speesds, when would a setting of 1010 be justified
If large headwinds dictate a large correction to the LRC speed, 1010 will be more efficient.
When would a reduction in LRC speeds be required
in Tail winds in excess of 100kts
LRC procedure
1) determine initial cruise ceiling with current AUW
2) Use specific range graph with current AUW & correct altitude
3) Determine TAS to fly using LRC on graph
What are the 6 TOLD GECs
- Full TQ?
- Vmcg dry?
- Vmcg wet
- Vrot limited by?
-Vmcg IGE/OGE?
- Dump time rqd?
- full TQ is available up to & incl 21deg C
- vmcg dry should always be in the 80s
- vmcg wet is +/- 18kts faster
-Vrot is limited by Vmca IGE at weights <120k, limited by Vto >120k - Vmcg IGE is always. 6-7kts less than Vmca OGE
-Dump time required when >120k lbs & more than 10,000lbs of fuel
Max endurance definition
Speed that results in min FF for a given weight, altitude and temp.
How would you prove LRC formula using the specific range chart
LRC SAR/MAX SAR = 99%
Relationship between weight & Vimd
Vimd is proportional to AUW, as weight decreases, power must be reduced to fly best range speed
Why do we set 300KTAS as a general rule of thumb?
- As this is a ballpark number that is the closest to LRC for most given weights and altitudes.
- Usually works out a bit faster than our actual LRC, with little to no effect on fuel consumption.
If our TAS is 290, and we are struggling to get to 300KTAS, are we underperforming?
- No, LRC is generally around 285-295KTAS, so we are actually more efficient at this speed than we would be at 300KTAS. Use book to find “top of curve” if rqd
- Only if time is an issue would you necessarily need to look at speeding up.
Considerations when climbing above F300:
- RVSM asx: can CLB into, however ATC must be told “negative RVSM” and will then provide 2000ft vertical sep rather than standard 1000ft for RVSM equipped a/c
- OXY: above FL300, all crew must have access to quick don oxy masks (Must have <10 POB as only 10 regulators are available)
What is IGE?
In ground effect, where the AC is flown half a wingspan (66ft) above the runway, reduction of induced drag, as well as air compression between the wing and the ground at low level allows acceleration to climb speed.
Why is VMCA IGE a lower speed than OGE?
Flying just above the runway causes compression of air between the wings and the ground, providing a higher level of controllability, therefore reducing VMCA compared to OGE
How does a wing work?
What is Vcef
Critical engine failure speed. (speed a/c can accel to, abort or continue T/O)
How to calculate slope
difference between the two ends (opposite threshold - THRS of RWY the slope is being calculated for), divide by RWY distance, multiply by 100.
HWC & TWC RoT when using graphs
EXCEPT ACCEL CX TIME (100% WIND);
Apply 50% of HWC & 150% TWC to all takeoff & landing distances being calculated
Do not apply head winds for CLB % or terrain clearance calcs
How to calc PA
Pressure Altitude: (QNH-1013, x diff by 30ft & TAKE from aerodrome elevation)
How to calc DA
(PA + 120 then multiply this by (TEMP- ISA TEMP))
How to work out VMCG/V1 split?
Take 15kts off of VMCG (wet) = min V1, work V1 chart backwards
RCRs; Dry & wet for:
Concrete, sand, ice
Concrete/Bitumen: 23 dry, 12 wet
Sand: 12 dry/8 wet
Ice: 8 Dry/5 wet
What is TASing out?
outperforming, opting to bring powers back to 932 TIT & let the a/c speed up without climbing.
Quantify by using the range summary fuel flow charts & extrapolate between 300KTAS & 310KTAS.
Define SGR
number of nm per pound of fuel consumed. The higher the SGR, the more efficient you are as you are covering more miles per pound of fuel.
What is a gangstart, our role, why do we do it?
Starting of no. 1&2 engines at the same time. Saves 1.5 mins & cannot be first flight of the day
Nav Duties: Time both 1 & 2 starts individually from “turning” until 60% RPM or the starter is released, note
Why: To monitor starter cycles
Define VMCG
Ground minimum control speed: the minimum airspeed at which the a/c can lose an outboard engine and maintain directional control during the takeoff ground roll.
(calculate using top graph - W/OUT NWS)
VMCG assumptions (7)
- No 1 engine inop & windmilling on NTS
- Max pwr on all operating engines
- Zero bleed
- Flaps 50 & 3000psi rudder boost
- Max available rudder deflection
- Max dev from Centreline of 30ft
- Wings level
Define VMCA1
VMCA1 is the minimum control speed in the air after failure of 1 outboard engine that must be maintained at or higher to maintain lateral directional control (prevent yawing from increased drag & therefore uncontrollability using max rudder)
VMCA1 assumptions (7)
- No 1 engine inop & windmilling on NTS
- Max pwr on all operating engines
- Zero bleed
- Flaps 50
- Max available rudder deflection
- 5 to the live
- LDG gear down
Define VMCA2
VMCA2 is the minimum control speed in the air after failure of TWO engines on the same side, that must be maintained at or above to maintain lateral directional control (prevent yawing from increased drag & therefore uncontrollability using max rudder)
VMCA2 assumptions (7)
- No 2 engine inop & feathered
- No 1 engine inop & windmilling on NTS
- Utility Hyd system inop
- Max pwr on 2 operating engines
- All bleed off
- Max available rudder deflection
- 5 to the live
Define V1
Refusal speed: is the maximum speed at which the aircraft can accelerate to with engines at takeoff power and then stop with the remainder of the RWY available.
V1 assumptions
assumes T/O power set on brakes, 4eng accel then abort, two engines in reverse, one in ground idle, and one prop windmilling on NTS, with maximum brakes.
Define OCL
Obstacle clearance SPEED,
Provides the speed the aircraft can climb at for its given weight & atmospherics.
What does the Take off gross weight limited by 3 eng CLB graph give us
Provides the rate of climb (fpm) the aircraft can climb at for its given weight & atmospherics.
Define critical field length
Is the greater of the total distance required (out of balanced or unbalanced CFL calculations) to accelerate on all 4 engines, experience a failure of the most critical engine and then either continue the T/O or stop.
What is balanced CFL?
Note?
When the distance required to continue the takeoff from engine failure (at Vcef) is equal to the distance required to stop (on 3 engines).
NOTE: the runway must at least be as long asthe balanced CFL
What is UNbalanced CFL?
When the accelerate-STOP distance from the lesser of VMCG or Vrot is greater than the accelerate-GO distance. (I.e. more distance is required to stop than to take off after a failed engine)
When do we use the Landing Dist over 50ft Obstacle graph, what do we do if the obstacle is higher than 50ft?
Standard landings/3 & 2eng out calculations for the day’s conditions & config, PLUS 500ft
Add extra distance: 20x additional obstacle height above 50ft
When do we use the landing ground roll graphs
To be used for MAX EFFORT landings only. NOTE: ADD 500FT IAW AVOs
Min RWY length for max effort takeoff
The greater or either 3000ft or ground roll plus 500ft (calculated using critical field length graphs)
Min RWY length for ME takeoff
The greater of either 3000ft or ground roll plus 500ft (to be calculated using LANDING GROUND ROLL graph with 2 eng in GI, 2 in REV)
When does an MTOW NOT need to be created (5)
- CofG is within limits & will remain for entire flight
- MAUW for T/O, LDG & ground movement is not exceeded
- Total FOB is <35000lbs
- There is no cargo
- Only operating crew to be carried (10 max)
When should a ditching/jettison plan be created
If a flight exceeds >2hrs over water
Whizz wheel 4x12 =?
=48
Place the last number ABOVE the 1.0
Find the first number BELOW the answer.
Whizz wheel 15/3 = ?
=5
Place the first number ABOVE the second number
Find the answer ABOVE 1.0.
What order is the T/D/V triangle?
D
V T
D = VxT
V = D/T
T= D/V
SGR calculation
GS/FF
Min SGR calculation
DTG/(FOB-Arrival mins)
Altitude definitions;
Indicated alt
Calibrated alt
Pressure alt
Density alt
True alt
- Indicated Alt: the altitude shown on an altimeter when QNH is entered
- Calibrated Alt: Indicated altitude corrected for instrument & position error
- Pressure Alt: Altitude shown when 1013.25hpa is entered
- Density Alt: A measurement of pressure altitude corrected for non-standard temperature
- True Alt: Altitude corrected & calibrated for temperature & pressure
Calc DA for 5000ft and 30deg using CR computer
Align P.A. & temp in the window BELOW the DA scale. The DA arrow will then identify the current density alt (8000ft)
Calculate TAS using whizz wheel for;
CAS (210kts), Pressure alt (7000ft), true air temp (20deg)
Place CAS (long window) above PA (scale)
Using the moving clear cursor, place on TAT line (big window), the scale underneath gives TAS.
(238KTAS)
Calculate CAS using whizz wheel for;
TAS (245kts), Pressure alt (10,000ft), true air temp (15deg)
Line up TAS scale & Temp (big window) (use moving clear cursor to help).
Find PA (10k ft on the scale underneath the CAS window) & obtain CAS from the number above (208kts)
Why are VMCG limited takeoffs dangerous?
Dangerous as when VMCG is higher than V1, the possibility of an engine failure after takeoff occurs whilst still below the speed where directional control can be maintained.
How does nose wheel steering affect VMGC
Steering avlble provides additional directional control which therefore reduces VMCG by 20kts
How does nose-wheel steering effect VMCG;
- When to use NWS Not available graphs?
Graphs to be used when there is likely to be reduced control on the ground due to wet/icy/sandy runway conditions
What is driftdown based on? (4 & NOTE)
- Prop feathered
- Set 1010deg C
- Decelerate to driftdown airspeed (Best Lift:Drag - sep flashcard)
- Automation: IAS until 100fpm, then VS
NOTE: 3eng cruise ceiling increases as fuel is burnt
Define Vrot?
RoT?
- Speed at which the aircraft will have sufficient acceleration capability to achieve Vto over time interval during which it is rotated to pitch attitude required for T/O.
- 5kts below Vto or Vmca (the higher)
What Weight/Speed is Vrot based on?
- Either Vto or VMCA1 IGE - 5kts (whichever is higher)
- At approx 120,000lbs it changes from being based off of VMCA1 IGE to Vto
What are the GECs you can used for climb speeds (when calculating for 5,10,15,20,25k)
- 4 engine climb: -4kts per 5000ft
- 10,000ft climb speed is more or less equal to 3 engine climb speed
Landing performance numbers;
THRS speed
1.35 x power off stall speed
Landing performance numbers;
Max effort THRS speed
1.28 x power off stall speed
Landing performance numbers;
Touchdown speed
1.2 x power off stall speed
Landing performance numbers;
Min THRS speed
106.5kts
Landing performance numbers;
Appch speed
THRS speed + 10kts
IAS - TAS pnuemonic & meaning
- ICE T is a Pretty Cool Drink
IAS - CAS: Pressure error
CAS - EAS: compressibility error
EAS - TAS: Density error
Rules when accounting for wind?
- 50% HWC
- 150% TWC
- EXCEPT ACCEL CHECK TIME
ROT for RCR <23
Use charts without nosewheel steering
ROT for objects higher than 50ft
Every 1ft, add 20ft to distance
EAS to TAS
EAS x SMOE
Define Vto
Safe flying speed based on a/c weight.
1.1x power OFF stall speed
Normal flap retraction?
Vto +20kts
Minimum flap retraction?
Max effort?
OCS
OCS50 +10kts
Best angle climb?
OCS
Excess thrust vs. drag
1.2x power OFF stall speed
Best rate of climb?
3ENG (for 3 & 4 eng)
Best lift:drag
Rough RoT 4kts decrease per 5000ft
Max recommended XWC?
35kts dependant on weight & RCR
What is takeoff performance predicated on?
3 sec to initiate gear UP
6 sec to initiate prop FX
Takeoff distance required? (TODR)
Distance required to accelerate and climb to 50ft AGL (4eng)
Max effort T/O speeds:
Vto
OCS
Vto: 1.2 x power ON stall speed
OCS: 1.3 x power ON stall speed
Acceleration check time
Calculate when V1 is within 10kts of Vr
Pilot to maintain NWS until rotate
3kts ASI tolerance
Calculating stall speeds RoT?
120k lbs;
114kts, 94kts, 84kts.
Vs decreases by 1kt per 2000lbs AUW
GFC?
Gross fuel consumption
= fuel/time
SFC?
Specific fuel consumption
= GFC/Power
Maximum endurance vs. Optimum endurance
Maximum: Speed that results in min fuel flow for a predetermined altitude, config, atmospheric cdxns, AUW.
Optimum: Speed AND altitude that results in min FF for given config, atmospheric cdxns, AUW.
Penetration descent
Flight idle
Best lift vs. drag to FL200
Then Vh
Rapid descent (configured)
145kts, 1.1nm/1000ft
Turb penetration
Vs + 65 up to max 180kts
Landing performance based on? (5)
- 3deg profile
- 50ft over THRS
- Flt idle & F100 at THRS
- antiskid operational (2030psi)
- 1sec b/t touchdown & nose on RWY.
Full reverse
LDG Dist: obstacle over 50ft RoT?
20x additional obstacle height (above 50ft) gets added to field length.
Min LDG dist required RoT?
ME ground roll
- landing dist over 50ft obs +500ft (2in rev, 2 in GI)
- Landing ground roll +500ft
Max RoD landing
Limits?
Normal?
540ft/min
Must be <130K AUW, max 6600lbs in outboards, externals empty
Otherwise max 300ft/min
