1. Flight Operations Web Conference – 05 May 2009
RTOW charts, Frequently Asked Questions

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3. RTOW charts, Frequently Asked Questions
Thierry PAYA-ARNAUD
Performance Training manager
Presented by:
RTOW charts, Frequently Asked Questions

4. FAQ about takeoff charts - Content
Minimum speeds
Acceleration altitudes
V1 evolution
Speeds checks
Limitation Codes
Flex corrections
TMAX, TFLEXMAX

5. FAQ about takeoff charts - Min Speeds
VMC, VMU…

6. FAQ about takeoff charts - Min Speeds
What is the meaning of the grey bar ?

7. FAQ about takeoff charts - Min Speeds
What is the meaning of the grey bar ?
A grey bar indicates that a takeoff speed is close to a VMC limitation. This limitation can be :
V1 limited by VMCG
V2 limited by VMCA
This indication is given so that the pilot pays particular attention to the aircraft control at these low speeds.

8. FAQ about takeoff charts - Min Speeds
How come V1 can be lower than the minimum V1 given at the bottom of the chart ?

9. FAQ about takeoff charts - Min Speeds
How come V1 can be lower than the minimum V1 given at the bottom of the chart ?
Minimum V1 given at the bottom of the chart is calculated by adding
the maximum VMCG on the global set of points (Complete chart) +
the maximum (V1-VEF) (Complete chart)
For a given point, V1 can be less than this minimum value if (VEF = VMCG) and (V1- VEF) is less than max (V1 - VEF)

10. FAQ about takeoff charts - Acceleration altitudes

11. FAQ about takeoff charts – Acceleration altitudes
Why are there stars in place of the min and max acceleration altitudes ?

12. FAQ about takeoff charts – Acceleration altitudes
Why are there stars in place of the min and max acceleration altitudes ?
Minimum acceleration altitude is calculated as the MAXIMUM of the ‘min acc. Altitude’ values on the global set of points
Maximum acceleration altitude is calculated as the MINIMUM of the ‘max acc. Altitude’ values on the global set of points
It may then happen that the min acc. altitude is higher than the max acc. altitude : in this case, stars are displayed in the chart and the min and max acc. altitude values must be read in a specific chart.

13. FAQ about takeoff charts – Acceleration altitudes

14. FAQ about takeoff charts - V1 evolution

15. FAQ about takeoff charts - V1 evolution
How come V1 can increase
while the weight decreases ?

16. FAQ about takeoff charts - V1 evolution
How come V1 can increase
while the weight decreases ?
In this example, we are Obstacle and Brake energy limited.
To reduce TOD, it may be interesting to increase V1 but V1 is limited by Max Brake Energy speed
The brake energy limitation depends on weight and the thrust
When OAT increases, the Weight decreases and the thrust decreases
When OAT increases, Max V1 limited by Max brake energy speed increases.

17. FAQ about takeoff charts – Speeds checks

18. FAQ about takeoff charts – Speeds checks
When applying influence corrections, do I have to check the speeds against the minimum values given at the bottom
of the chart ?

19. FAQ about takeoff charts – Speeds checks
When applying influence corrections, do I have to check the speeds against the minimum values given at the bottom
of the chart ?
Yes, when
More than one correction is applied
If no correction or only one correction is applied, the speeds are OK. No speed Check against ‘min speeds’.

20. FAQ about takeoff charts – Limitation CodesV1 V2

21. FAQ about takeoff charts – Limitation Codes
On a weight chart, can I interpolate between 2 weights with different limitation codes ?

22. FAQ about takeoff charts – Limitation Codes
On a weight chart, can I interpolate between 2 weights with different limitation codes ?
Yes, because
the automatic temperature chart used to build the weight chart is accurate enough (slight trend below Tref, step of 2°C above Tref)

23. FAQ about takeoff charts – Flex corrections

24. FAQ about takeoff charts – Flex corrections
When applying corrections on TFlex for QNH or bleeds, why isn’t there a correction on the speeds ?

25. FAQ about takeoff charts – Flex corrections
When applying corrections on TFlex for QNH or bleeds, why isn’t there a correction on the speeds ?
The speeds are directly linked to the takeoff weight for a given runway length and braking capability of the aircraft
In case of QNH or bleed correction, the only affected item is the engine thrust

26. FAQ about takeoff charts – Flex corrections
When applying corrections on TFlex for QNH or bleeds, why isn’t there a correction on the speeds ?
Weight
Thrust
Flat rated Thrust
Bleeds correction
Actual TOW
Needed
Thrust
EGT Limit
ΔTFlex Temp
correction
Flex Temp
Bleeds ON
Flex Temp
full Thrust
OAT

27. FAQ about takeoff charts – Flex corrections
When applying corrections on TFlex for QNH or bleeds, why isn’t there a correction on the speeds ?
The flex temperature correction is calculated so that the thrust after TFlex and Bleeds correction is equal to the thrust needed without bleeds.
As the aircraft braking capability is not degraded, the speeds don’t need to be modified.

28. FAQ about takeoff charts – TMAX, TFLEXMAX
Why do I have temperatures above the TMAX indicated on the bottom of the chart ?

29. FAQ about takeoff charts – TMAX, TFLEXMAX
TMax is the MAX certified OAT For dispatch
The RTOW chart is used for MTOW determination and for FLEX computation
The range of temperature covers OAT up to TMax AND temperature Above Tmax, Up to TflexMAX
Why do I have temperatures above the TMAX indicated on the bottom of the chart ?
Last value of OAT for Dispatch
Temperature for Flex only 54

30. FAQ about takeoff charts – TMAX, TFLEXMAX
I received new charts for a new aircraft .
Why is the max temperature displayed on the chart much higher than before

31. FAQ about takeoff charts – TMAX, TFLEXMAX
To improve customers operations, The maximum Thrust reduction has been increased
This is available as ‘Extended Flex’ option
On this example, the TFlexMax is increased from ISA + 43°C to ISA + 72°C
The new charts computed for aircraft equipped with Extended flex option will provide temperature much higher than before
I received new charts for a new aircraft .
Why is the max temperature displayed on the chart much higher than before

32. Questions
Questions?

33. Questions
Question: For the same conditions, if there is the same TOW for CONF 2 and CONF 3, which one is more favorable?
Answer: According to FCOM, use the configuration that gives the highest flex. If both of them provide the same level of flex thrust or if you cannot flex, use the one with the highest flaps setting. This may change in specific conditions. Please refer to FCOM P2.

34. Questions
Question: I understand that when the code changes between 2 boxes, one can interpolate between the take off weights. But can we also interpolate for the speeds, which at times change dramatically?
Answer: Yes. Interpolation shall be done for all parameters (weight and speeds).

35. Questions
Question: Sometimes, ATC requires the aircraft to enter the runway using alternate runway entrance. The take off runway distance available is then reduced. And the crew needs to update the take off speeds accordingly. How can we handle this?
Answer: There is no simple way to handle that with paper RTOW charts. A specific chart may be used for a very often used taxiway, but that increases the number of charts. The use of LPC (software on board) allows this type of computation.

36. Questions
Question: I've checked the landing distance performance of our A using the FOVE landing module. The difference between normal landings distance vs. abnormal, especially on contaminated runways seem to be negligible.
Answer: The impact of failure during the flight depends on the failure case. This impact is given in the QRH with failure coefficients. Some of them are low (1.1 or 1.2) because the failure only requires higher speed and has no effect on braking capability of the aircraft. In any case, keep in mind that the distances given by the QRH or the LPC are reference landing distances and that the crew shall retain a runway with sufficient margins.

37. Questions
Question: Similar for takeoff, how do you calculate MIN ACC ALT and MAX ACC ALT for go-around with Engine Out?
Answer: There is no MIN ACC ALT or MAX ACC ALT definition for go-around. What has to be checked in case of a go-around is that the aircraft remains above the plane (i.e. surface) defined by the missed approach gradient. You can refer to the presentation held in Paris Conference this year for more details on go-around procedure check.

38. Questions
Question: Why has the Bleed corrections to Flex increased a lot recently?
Answer: The Anti-ice corrections increase is linked to an Octopus change. You can refer to PEP 4.4 reasons for change. The principle of anti-ice corrections on takeoff charts have been modified: the reduced temperatures list (below 10°C OAT) is used only to determine weight and speed corrections, the complete temperatures list is used for flex temp correction. The same principle is used in the FCOM. As a consequence, Flex corrections for anti-ice may have been updated in the FCOM and takeoff charts corrections must be recomputed.

39. Questions
Question: With TmaxFlex of ISA+75, for sure you would go below 25% max legal thrust reduction? Can you explain?
Answer: Airbus re discussed this 25% max reduction and obtained a new certification from authorities for this modification. Keep in mind that it was already possible for other manufacturer to go beyond 25% using Flex on Derate.

40. Questions
Question: Can you please discuss Airbus philosophy for operations with the A320 on runways with a width less than 45 meters?
Answer: Operating on a runway with a width lower than 45 m implies an increase in VMCG to be able to control the aircraft inside the limits of the runway as described in the regulation. This VMCG increment is automatically taken into by the software provided the runway width has been correctly entered.

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