Rejected Take Off (RTO)
Description
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 if an
aeroplane is to be able 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 it 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 which 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.
Solutions
Runway Excursions
arising from Rejected take offs can therefore usually be avoided if Operating Procedures for
the loading
and take off of aircraft are robust and rigorously applied.
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:
•
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).
Simulator Training
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 - for example a
transient aberration in then operation of a single engine and tyre failure as
well as 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.
Related Articles
Runway Excursion
Accident and Incident
Reports
Runway Excursion
Accidents and serious incidents which include Runway Excursion (Overrun on Take
Off) as an outcome:
•
A345, Melbourne
Australia, 2009 (RE HF) (On 20 March 2009 an Airbus
A340-500, operated by Emirates, commenced a take-off roll for a normal
reduced-thrust take-off on runway 16 at Melbourne Airport. The attempt to get
the aircraft airborne resulted in a tail strike and an overrun because
insufficient thrust had been set based upon an incorrect flight crew data
entry.)
•
B703, Sydney
Australia, 1969 (BS RE) (On 1 December 1969, a Boeing 707-320 being
operated by Pan Am and making a daylight take off from Sydney, Australia ran
into a flock of gulls just after V1 and prior to rotation and after a
compressor stall and observed partial loss of thrust on engine 2 (only), the
aircraft commander elected to reject the take off. Despite rapid action to
initiate maximum braking and the achievement of full reverse thrust on all
engines including No 2, this resulted in an overrun of the end of the runway by
170m and substantial aircraft damage. A full emergency evacuation was carried
out with no injuries to any of the occupants. There was no fire.)
•
B732, Pekanbaru
Indonesia, 2002 (RE HF AW) (On 14 January 2002, a
Boeing 737-200, operated by Lion Air, attempted to complete a daylight take off
from Pekanbaru, Indonesia without flaps set after a failure to complete the
before take off checks. The rejected take off was not initiated promptly and
the aircraft overran the runway. The take off configuration warning failed to
sound because the associated circuit breaker was so worn that it had previously
auto-tripped and this had not been noticed.)
•
B737, Southend
UK, 2010 (RE HF) (On 21 Nov 2010, a Boeing 737-700
being operated by Arik Air on a non revenue positioning flight from Southend to
Lagos with only the two pilots on board carried out a successful take off in
daylight and normal ground visibility from runway 06 but became airborne only
just before the end of the runway.)
B738, Manchester
UK, 2003 (GND RE HF) (On 16 July 2003, a Boeing
737-800, being operated by Excel Airlines on a passenger flight from Manchester
to Kos began take off on Runway 06L without the flight crew being aware of work
in progress at far end of the runway. The take off calculations, based on the
full runway length resulted in the aircraft passing within 56 ft of a 14 ft
high vehicle just after take off.)