Aircraft Take-Off Performance Flashcards
Flat rated Temps
Assumed temperature cannot be lower than the flat rated temp of the engine or the OAT. Also assumed temperature cannot be higher than the temperature which results in a 25% reduction of full rated take off thrust.
GE90-85B/-115B : 30 deg C
Trent 895 : 25 deg C
Assumed temperature not permitted if:
1) Card notes or perf manual take off page prohibit assumed temp thrust reduction on that specific runway.
2) Runway has degraded braking action or is contaminated.
3) DDG requires full thrust.
4) Particular windshear conditions exist.
What is Assumed Temperature?
For a given aircraft weight, it is the maximum temperature (corrected for QNH and air conditioning packs) at which take-off would be permitted.
Take-Off Performance Options
Options to increase TOPL and or allow a higher assumed temperature thrust reduction:
1) Selecting Air con packs off.
2) Improved climb (take off data pages and perf requests are always based on improved climb - this cannot be deselected)
3) Alternate forward centre of gravity. - Reduces trim drag. Only available on B777-200.
Temperature Inversion
If a significant temperature inversion is forecast or there is reasonable evidence of its presence due to conditions (I.e. clear, calm conditions at night ) and the temperature is above ISA+15, then 3 deg should be added to the report tower temperature prior to calculating TOPL.
DDG Performance Corrections
DDG performance corrections for operations with degraded / missing equipment are normally applied to the TOPL (unless otherwise specified)
Vmcg
Vmcg is the minimum airspeed during the take-off run at which, if the critical engine suddenly fails, it is possible to maintain directional control using ONLY aerodynamic controls.
Vmcg tables can be found in the take-off section of the perf manual.
If a V1 is entered into FMC below Vmcg the FMC will advise the Vmcg value.
Ballpark figures : with OAT of 20 deg - 123 kts for B772 and 129 kts for B773
ETPs
Terrain clearance is generally not assessed beyond end of SID. Crew must ensure relevant MSA is achieved before continuing beyond end of SID.
An ETP which deviates from the SID will be published when terrain clearance is not achieved on the SID track with one-engine inoperative.
Standard ETP construction assumes take-off at max take-off weight with an engine failing at the most critical point of the take-off. Other performance limiting factors such as gear / flaps failing to retract are not considered.
ETPs are NOT generally shared with authorities therefore crew need to advise ATC of what they’re doing at earliest opportunity.
An ETP will not be published when terrain clearance is achieved on the SID track with one eng Inop, however this does not mean published ATC altitude constraints will be met (probably won’t with 1-eng inop) and crew must inform ATC of this.
Take-off data pages
Take-off data pages are provided as a backup when Lido performance is not available. If both Lido performance and take off data pages are not available then contact flight dispatch at LHR (Acars : .FCB) or telephone.
Taking Off From Contaminated or Degraded Braking Runways
DO NOT base assessments solely on a reported Runway Condition Code or reported braking action, these should be considered along with all other available information when assessing what level of performance should be used.
Use Flow Chart to decided which data (Contaminated or Degraded) is most appropriate to use when taking off from a runway that is NOT dry or wet.
(Precipitation on ground or falling or ‘Braking action MEDIUM OR WORSE’ or ‘RWY PROMULGATED SLIPPERY WHEN WET’ should make you start thinking about this)
Observe following limitations:
1) If there is any doubt about the condition of snow especially when OAT is above -5 deg C TREAT IT AS SLUSH. (C)
2) A mixture of snow and slush MUST BE TREATED AS SLUSH. (C)
3) Check Max Crosswind Limitations! (C)
4) Reduces thrust take off NOT PERMITTED. (C & D)
5) No deficiencies in braking systems. I.e. Speedbrake, Reverse Thrust, wheel brakes and anti-skid. (C & D)
6) Use maximum runway distance available. (C & D)
7) Must consider: Nature and consequences of overrun and possible weather changes since last report. (C & D)
8) Visual guidance for take-off must be available from any of the following- Runway centreline lighting / markings, Runway edge lighting / markings. (C)
9) Minimum cleared width of 40m and symmetrical about centreline. (C)
10) PACKS may be ON or OFF. (C & D)
NOTE: Take-off with tailwinds greater than 5kts is NOT recommended. (C & D)
Note: performance data for contaminated runways assumes a uniform depth of contaminant along the entire length and width of the runway which is an unlikely situation.
Note: performance data for degraded braking action runways assumes the runway is NOT contaminated and has a uniform braking action along the entire width and length, which is an unlikely situation.
Contaminated Runway Definition
A runway is considered contaminated when a significant portion of the runway surface area (whether in isolated areas or not) within the required length and width being used is covered by one or more of the following: MORE THAN 3 mm of water/wet snow/ dry snow / slush, compacted snow or ice.
Note: for depths of 3 mm or less the runway is NOT considered to be contaminated and WET runway data should be used.
Runway Condition Definitions
DRY - surface free of visible moisture and not contaminated within the area of intended use
WET - surface covered by any visible dampness or water up to and including 3mm deep within the area of intended use.
CONTAMINATED - significant portion of its surface area (whether in isolated areas or not) within the length and width being used is covered by one or more of: MORE THAN 3 mm of water/wet snow/dry snow/slush, compacted snow or ice.
DEGRADED BRAKING ACTION - covered by compacted snow or ice or a runway that is reported to be slippery when wet. A reported braking action is usually given for such runways.
SLIPPERY - A runway having a theoretical aircraft braking coefficients of 0.05 mu.
Note - Landing on a slippery / icy runway is NOT RECOMMENDED as stopping the aircraft presents a significant problem.
