RTOW charts are computed for each runway using approved Airbus performance software called Performance Engineering Program (PEP). They optimize takeoff performance and aim at obtaining maximum performance limited takeoff weight or optimum takeoff thrust for a given weight. The following parameters can be optimized:

1. Aerodynamic Configuration (selection of flaps)
2. Air conditioning (Packs On or Off takeoff)
3. Thrust setting (TOGA/FLEX/Derated levels)
4. Takeoff speeds (This has largest effect on the gain of takeoff weight. The range of optimization varies from 0.84 to 1.0 for V1/VR ratio and from 1.13 to 1.4 for V2/VS1G ratio)

TREF, TMAX and TVMC values are given on RTOW chart.

T FLEX MAX

TFLEX MAX is temperature at which maximum thrust reduction allowed by regulation is reached.

For most of the MSN numbers flex takeoff with maximum thrust reduction of 25% is allowed (with few exceptions where 40% thrust reduction is also allowed).

This value is not given on RTOW charts are RTOW charts are designed keeping these restrictions in mind.

GREY BAR

A grey bar signifies that the takeoff speed is approaching the Vmca limit. V1 is constrained by Vmcg, while V2 is constrained by Vmca. This indication is given so that the pilot pays particular attention to the aircraft control at these low speeds.

GRAD CORRECTION

GRAD Correction is applicable when OAT is below the flex temperature specified with maximum weight. Grad 1 applies when the temperature is less than TREF, and Grad 2 applies when the temperature is higher.

Grad correction is given in Kg per deg C. It may not be applicable for all charts.

Maximum thrust begins to decrease during Grad 2. It is applied only when OAT is less than flex temperature mentioned with maximum weight. This is generally used to find out MTOW. Speeds remain same after Grad 1 and Grad 2 corrections to weight.

If OAT and TREF both are less than lowest temperature given in applicable wind and configuration column, both GRAD 1 and GRAD 2 corrections are required.

DRY CHECK

A dry check involves comparing weights to those on a wet runway, as wet conditions may allow for higher weights due to reduced screen height (15 feet) and credit for reversers. To avoid this situation, lower weight is taken for all TOW references.

Additional Notes:

• As per regulations, Takeoff performance is calculated without considering the benefit of thrust reversers.
• Effect of thrust reversers may be considered for WET and CONTAMINATED runway but in doing so no MTOW cannot be higher than calculated DRY runway.
• All performance data is given on concept of balanced field length.

RTOW FAQs

Reference: https://www.scribd.com/presentation/379851293/Webconference-01-Rtolw-Faq-Takeoff

1. What is the Airbus philosophy for operation with A320 on runways with width less than 45 meters?
   Operating on a runway with a width lower than 45 m implies an increase in Vmcg to control aircraft. This is automatically taken care by software as long as runway width has been correctly entered.
2. With T MAX FLEX of ISA+75, thrust will go below 25% of maximum legal thrust reduction. Is this allowed?
   New certification from authorities has been obtained. It was a regular practice by other manufacturer to go beyond 25% using flex or derate.
3. How to calculate minimum and maximum acceleration altitude for go-around with engine out?
   There is no minimum and maximum acceleration altitude definition for go-around. Only climb gradients need to be met.
4. For the same conditions, if there is the same TOW for CONF 2 and CONF 3, which one is more favorable?
   Use the configuration that gives the highest flex. If both of them provide same flex, use the one with the highest flaps setting.

Limitations display of RTOW charts

Nature of takeoff weight limitation is always indicated in takeoff charts (RTOW charts). Following is the list of codes assigned to different limitations.

• OEI – One Engine Inoperative
• AEO – All Engine Operative

Limitations display on EFB program

In EFB Airbus is using Flysmart+ program for take-off and other performance calculations. Limitation codes are not application to this as same is displayed in textual format.