On the Takeoff page on the MCDU, the takeoff configuration is entered into the FMS. This takeoff configuration comprises settings such as takeoff flaps, horizontal trim setting, FLEX TO temp, and V-speeds (V1, VR, V2).
On the R3 section of the MCDU, there is an option for FLAPS/THS. This is short for Flaps/Trimmable Horizontal Stabilizer.
This section allows for takeoff flap entry and horizontal stabilizer trim setting.
All required entries are inputted via the scratchpad found on the MCDU, followed by being confirmed by pressing the pertinent L/R key on the correct entry field of the MCDU.
Airbus Flaps/THS Setting
During the pre-flight phase, calculations in relation to aircraft weights are made via the EFB and the flight plan load sheet. Upon entering the Zero Fuel Weight (ZFW), Block Fuel and Gross Weight (GW) of the aircraft, the appropriate takeoff flap setting, and trim position will be calculated.
FLAPS/THS field can be filled in using the following format: F/TRIMX.X.
If Flap 1 and trim up position of 0.2 has been calculated, 1/UP0.2 will be entered.
Upon entering this information, the automatic pitch trim system of the aircraft will set the trim setting specified in the MCDU.
This automatic trim system can be manually overridden by the flight crew if required.
The trim position of the horizontal stabilizer can be verified on the lower ECAM screen by selecting the F/CTL (Flight Control) page.
This along with looking at the trim wheel can be used to verify the correct position of the trim. These checks form part of the flight control check performed prior to departure.
On the trim wheel of the aircraft, the flight crew must first verify that the trim is within the green band followed by ensuring the exact trim position is set.
Also Read: Airbus Engine Mode Selector Crank
How to Calculate Flaps THS
The appropriate Flaps/THS settings can be calculated after aircraft weights have been determined. These weights include Block Fuel, Zero Fuel Weight (ZFW), and most importantly the Center of Gravity (C.G) of the aircraft.
The C.G and weight distribution calculated will determine the specific trim setting for the aircraft.
Flap settings for takeoff are calculated based on a number of factors:
- Runway Length
- T/O Thrust setting
- Weather conditions
- Takeoff weight
After entering the takeoff settings into the FLAPS/THS field and setting TO FLEX thrust, the takeoff V-speeds can then be calculated on the left portion of the MCDU.
The calculated V-Speeds are dependent on:
- Takeoff Flap Setting
- Takeoff Trim Setting
- Departure Runway
- Takeoff Weight
- FLEX TEMP Setting
Upon calculation, the V-speeds will be displayed on the speed tape found on the Primary Flight Displays (PFDs).
Also Read: Airbus Detents and Autothrust (A/THR) System