Rejected Take Off
From SKYbrary Wiki
- 1 Description
- 2 The Go/Stop Decision
- 3 Continuing the Take Off after V1
- 4 The Significance of Speed in respect of the decision to reject a take off
- 5 High Speed RTO
- 6 Low Speed RTO
- 7 Tyre Failure on the Takeoff Roll
- 8 Rejected Takeoffs and Runway Excursions
- 9 Solutions
- 10 Application of SOPs
- 11 Simulator Training
- 12 Accident and Incident Reports
- 13 Related Articles
- 14 Further Reading
The situation which follows when it is decided to stop an aircraft during the take off roll.
The Go/Stop Decision
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).
A successful rejection should be achieved if the response is immediate and completed in accordance with prescribed procedures (SOPs). After V1, a reject should only be considered if there is a strong reason to believe that the aircraft will not fly.
Depending on Operator SOPs, a call of "STOP" to reject a take off based on stated criteria will usually be able to be made by either pilot. However, in some cases, the action following such a call will be only for the pilot in command to take, regardless of which pilot is PF.
Continuing the Take Off after V1
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. 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. 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. 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.
The Significance of Speed in respect of the decision to reject a take off
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. This speed is usually in the vicinity of the speed where directional control using the rudder becomes effective. 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. 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.
High Speed RTO
Whilst a successful rejection of take off 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 it, the greater the risk involved in a decision to stop. 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. In many modern aircraft types, the annunciation of non-critical alerts during the high speed part of the take off roll and in initial climb is inhibited to preclude unnecessary distraction.
Low Speed RTO
Prior to the prescribed speed check call, it is envisaged that the takeoff will normally be rejected for any significant malfunction or abnormal situation. Within this lower speed range, it is likely that directional control will be largely dependent on use of the nose gear steering system. 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 take off to be ready to make any necessary control inputs to the nose gear steering system via the tiller provided.
Tyre Failure on the Takeoff Roll
Tyre failure during the takeoff roll has been the cause of inappropriate decisions to reject a take off. Failure of a tyre will result in a longer than calculated stopping distance due to the loss of braking force on the associated wheel. It also has the potential to lead to additional tyre failure if a high speed rejected take off is then made due to the brake temperatures which a high energy stop will create. 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. However, any decision to reject a take off 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 take off is continued.
Rejected Takeoffs and Runway Excursions
The main reasons why runway excursions occur during rejected take offs can be categorised as:
- the decision to reject the take off is made after V1 and there is insufficient runway length left to come to a stop on it.
- the flight crew actions required to achieve a rejected take off are not carried out in a sufficiently prompt and/or comprehensive manner.
- stopping devices are not used to their full capacity.
- directional control is not maintained during the take off roll.
- it is found at Vr that it is impossible to achieve rotation.
The V1 call must be made in such a manner that the verbalisation is complete as the speed is achieved. Stopping action must be initiated promptly (within 2 seconds) of the reject decision. Stopping devices must be used to their full capability until such time that it is certain that the aircraft will stop before the end of the runway. Unless there is a clear indication that the aircraft will not fly, a reject must not be initiated after V1.
However, for large aircraft, there is usually a significant gap between V1 and Vr so that if, at Vr, it is found impossible to physically achieve rotation, there may be no alternative but to reject the take off. It is this scenario, on limiting runway lengths, which accounts for many of the most serious runway excursions arising from rejected take offs. Often, the problem with rotation is attributed to aircraft total weight or Centre of Gravity being different to that understood by the flight crew, due to differences in the distribution or weight of the actual load and that indicated on the certified load and trim sheet. A similar circumstance may result from take off using incorrect aircraft performance calculations or ASI speed bug settings, although a viable flight crew emergency response to these cases may be available by means of a prompt increase to maximum available thrust/power.
Aircraft Loading procedures must be properly specified, and there must be checks that the aircraft has been loaded in accordance with the documentation supplied to the flight crew. Particular care in is required where the provision of this service is by a contractor and especially so where such a contractor supplies equivalent services to other operators using the same staff, since the contractual requirements of all operators may not be the same. Where flight crews use electronic flight bags (EFBs) to calculate take off performance, special attention should be given to the applied SOP and to crew training to ensure that both crew fully understand EFB use.
Application of SOPs
All the relevant Flight Crew SOPs must be clearly specified and applied, particularly:
- Cross checking take off performance calculations and the corresponding setting of ASI speed bugs.
- Both flight crew must be fully satisfied that the prevailing runway surface conditions correspond to the assumptions which have been made in their take off performance calculations.
- There must be unambiguous requirements governing crew calls of abnormal conditions during the take off roll and the degree to which the aircraft commander then has the discretion to reject or continue the take off.
- There must be accurate calls of standard speeds during the take off by PM and a check that both principal ASIs are indicating the same figure at the designated check speed (usually 80 KIAS or 100 KIAS).
Once robust flight crew SOPs are in place, the most effective way for an Operator to ensure that flight crew are likely to respond to a rejected take off decision and its execution in the expected way is practice. This means ensuring that the plan for both initial and recurrent aircraft type simulator training and assessment includes unexpected scenarios in which a rejected take off may be the only expected response or a judgement call. Both stop-go take off decisions and the response to stop decisions should be covered. These unexpected events should include evidence of malfunctions other than total engine failure - as examples, a transient aberration in the operation of a single engine combined with tyre failure and loss of directional control, unexpectedly slow aircraft acceleration and ATC instructions given after reaching high speeds. The ability to made prompt and rational decisions on stop-go should be trained and validated - evidence of indecision should an indication that more training is required. The 'unable to rotate at Vr' case should also be included, with the cause being variously the wrong take off speeds or thrust set, the effect of a microburst or of the effect of a mis-loaded aeroplane.
Accident and Incident Reports
Runway Excursion Accidents and serious incidents which include Runway Excursion (Overrun on Take Off) as an outcome:
- Runway Excursion
- Rejected Take Off: ATC Considerations
- Engineered Materials Arresting System
- European Action Plan for the Prevention of Runway Excursions (EAPPRE) Edition 1.0, January 2013.
Airbus Flight Operations Briefing Notes
Flight Safety Foundation
- Reducing the Risk of Runway Excursions - Report of the Runway Safety Initiative
- Runway Excursion Risk Assessment Tool
- Rejected Takeoff (OGHFA SE)
- Takeoff Weight Entry Error and Fatigue (OGHFA SE)
- ALAR Briefing Note 8.4 - Braking Devices
- ALAR Briefing Note 8.5 - Wet or Contaminated Runways
Ohio State University