Airbus TOS ( TAKE-OFF Securing) surveillance system

TOS Is a function that provides an additional safety net able to detect some of the human errors regarding erroneous take-off parameters and operations .

The objective is to help pilots in identifying abnormal situations before taking off .

Three types of errors can be made during the take-off preparation by the pilot’s entail of the computation of the weight by ( ZFW ,CG position and the calculation of V1,VR, V2.

• the data entry process into the flight management system ( FMS) may be incorrect ( stress,distraction ,,,etc)
• parameters entered into the tables or into EFB programs may be wrong ( runway length , outside temperature , etc)
• computations may be inaccurate ( wrong interpretation of chart , bug in the software ,,,etc) .

consequences of these types of errors on the take-off speeds:

• A too low V2 plus one engine out condition this may lead to not clearing the obstacle path .
• A set of too high Take-off speeds may lead to a runway overrun or too high energy to rejected takeoff .
• A too low VR may lead to a tail strike .
• An error on the A/C configuration at takeoff ) CONF/TRIM) setting may lead to an auto rotation ( nose heavy) .
• A WRONG THRUST rating may result in a tailstrike , a runway overrun or climb path shift .

• A TAKE-OFF from a different runway or intersections may lead to :

1. A collision with another aircraft or vehicle on ground .
2. A collision in the air with an obstacle .
3. An overrun at the end of the runway due to high or low energy.

The TOS function is available from the flight preparation to the takeoff it activates only if an abnormal data entry by informing the flight crew with a type and level of alert, has been designed into two steps :

TOS 1 is designed to detect speed consistency error with aircraft takeoff configuration in FMS (V1,VR and V2 ) .

TOS 1 alerts are first triggered at FMS scratchpad during takeoff data insertion . This check prevents mainly the tail strikes.

Tos1

TOS2 is designed to detects operational aircraft position errors in preflight and takeoff by :

• Lift off distance compatibility with runway being used is also performed at takeoff , considering current aircraft parameters such as current GPS position current thrust, this may cause ECAM alert .
• Aircraft position check is performed at takeoff power to avoid takeoff from non-planned runways or takeoff from taxiways to cause an ECAM alert
• Lift off distance compatibility with runway used is checked in preflight considering data inserted in the FMS including takeoff shift , flap settings,Takeoff weight, flex temperature, TORA .

TOS2 function alerts the pilots as soon as possible in order to Reject the takeoff under 100 knots if an issue is detected . Note: no alert after 80 knots.

TOS2

Associated Alerts :

NAV NOT ON FMS RUNWAY (Amber ) when the Aircraft is not on the runway and when the thrust lever are set to or above the CLB detent

NAV ON TAXIWAY (RED) when the aircraft is not on the runway and when the thrust levers are set to or above the CLB detent .

T.O RWY TOO SHORT (Red) come when the liftoff distance is more than the available runway length and when engines are set to takeoff power

T.O RWY TOO SHORT (AMBER ) come when the liftoff distance is more than the available runway length and when the flight crew press the T.o CONFIG pb.

By captain Ahmed shebl

Airbus 320/321/330/300/310 captain and faa flight instructor , MBA aviation management