The main reasons why runway excursions occur during rejected takeoffs can be categorised as: However, any decision to reject a takeoff in excess of the speed cross check call which is not mandated in the applicable SOPs should be taken only when there are clear indications that the safety of the flight is at risk if a takeoff is continued. One aircraft manufacturer, Airbus, has made a generic recommendation that, for a single tyre failure with no evidence of collateral damage, the takeoff be continued if the speed is greater than V1 minus 20 knots. It also has the potential to lead to additional tyre failure if a high speed rejected takeoff is then made due to the brake temperatures which a high energy stop will create. Failure of a tyre will result in a longer than calculated stopping distance due to the loss of braking force on the associated wheel. Tyre failure during the takeoff roll has been the cause of inappropriate decisions to reject a takeoff. However, speeds in this range will usually be well below the applicable Vmcg - the speed at which sufficient rudder authority to maintain directional control is available and so it is important for a pilot carrying out any low speed rejected takeoff to be ready to make any necessary control inputs to the nose gear steering system via the tiller provided. Within this lower speed range, it is likely that directional control will be largely dependent on use of the nose gear steering system. Prior to the prescribed speed check call, it is envisaged that the takeoff will normally be rejected for any significant malfunction or abnormal situation. In many modern aircraft types, the annunciation of non-critical alerts during the high speed part of the takeoff roll and in initial climb is inhibited to preclude unnecessary distraction. Therefore, once at high speed, it is usually specified that the takeoff will only be rejected for major malfunctions such as an engine failure or fire - or at the discretion of the pilot in command in the event that a similarly serious situation is perceived. Whilst a successful rejection of takeoff from V1 is achievable in all but exceptional and very specific cases (see below), it is universally recognised that the closer the speed gets to V1, the greater the risk involved in a decision to stop. The fact that this call also functions as a validation that both pilots have similar airspeed indications and as a pilot incapacitation check means that the determination of the speed takes all three purposes into consideration. The prescribed speed has to be called out by PM from their own airspeed indication and the call must receive a prompt response from the PF. This speed is usually in the vicinity of the speed where directional control using the rudder becomes effective. Most aircraft manufacturers specify an airspeed - usually 80 knots or 100 knots - which defines the transition between the low speed and the high speed part of a takeoff roll and represents a change in the expected use of a "stop" call. The Significance of Speed in respect of the decision to reject a take off In this case there is no option but to reject the take off despite the likelihood that a runway overrun of some sort will result. However, there are certain situations (see below) where it may be found at Vr that it is simply not possible to get airborne and there is no effective solution available. This explicitly covers the case of a single engine malfunction or failure up to V1 provided that the prescribed crew actions in respect of that failure are correct. Once a correctly calculated V1 has been exceeded, the takeoff must be continued and should allow the aircraft to get safely airborne and climb away. However, in some cases, the actions following such a call will be only for the pilot in command to take, regardless of which pilot is PF. After V1, a reject should only be considered if there is a strong reason to believe that the aircraft will not fly.ĭepending on Operator SOPs, a call of "STOP" ("ABORT', "REJECT") to reject a takeoff, based on stated criteria, will usually be able to be made by either pilot. In the event of an engine malfunction, the recognition of a significant abnormality, or an ATC instruction to stop the aircraft during the take off roll, transport aircraft in Performance Category ‘A’ should be able to safely reject the take off if the decision to do so is made at a speed not greater than the correctly calculated decision speed ( V1).Ī successful rejection should be achieved if the response is immediate and is completed in accordance with prescribed procedures ( SOPs). The actions taken when it is decided to abandon the takeoff and stop an aircraft during the takeoff roll.
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