2.0	 Introduction................................................................................................................... 2.1

2 .1	 Objectives...................................................................................................................... 2.1

2.2	 “Successful Versus Unsuccessful” Go/No Go Decisions.............................................. 2.1

2.2.1	 An In-service Perspective On Go/No Go Decisions................................................. 2.2

2.2.2	 “Successful” Go/No Go Decisions........................................................................... 2.3

2.2.3	 RTO Overrun Accidents and Incidents..................................................................... 2.4

2.2.4	 Statistics.................................................................................................................... 2.5

2.2.5	 Lessons Learned ....................................................................................................... 2.6

2.3	 Decisions and Procedures—What Every Pilot Should Know....................................... 2.7

2.3.1	 The Takeoff Rules—The Source of the Data ........................................................... 2.8

2.3.1.1	 The “FAR” Takeoff Field Length........................................................................ 2.8

2.3.1.2	 V1 Speed Defined.................................................................................................... 2.10

2.3.1.3 Balanced Field Defined ..................................................................................... 2.11

2.3.1.4	 (Not Used)......................................................................................................... 2.12

2.3.2 Transition to the Stopping Configuration ............................................................... 2.12

2.3.2.1	 Flight Test Transitions....................................................................................... 2.12

2.3.2.2	 Airplane Flight Manual Transition Times......................................................... 2.12

2.3.3	 Comparing the “Stop” and “Go” Margins.............................................................. 2.14

2.3.3.1	 The “Stop” Margins........................................................................................... 2.15

2.3.3.2	 The “Go” Option ............................................................................................... 2.16

2.3.4	 Operational Takeoff Calculations........................................................................... 2.18

2.3.4.1	 The Field Length Limit Weight......................................................................... 2.18

2.3.4.2	 Actual Weight Less Than Limit Weight ............................................................ 2.19

2.3.5	 Factors that Affect Takeoff and RTO Performance................................................. 2.19

2.3.5.1	 Runway Surface Condition ............................................................................... 2.20

2.3.5.1.1	 Hydroplaning............................................................................................... 2.21

2.3.5.1.2	 The Final Stop .............................................................................................. 2.22

2.3.5.2	 Atmospheric Conditions.................................................................................... 2.22

2.3.5.3 Airplane Configuration...................................................................................... 2.23

2.3.5.3.1	 Flaps.............................................................................................................. 2.23

2.3.5.3.2	 Engine Bleed Air .......................................................................................... 2.23

2.3.5.3.3	 Missing or Inoperative Equipment .............................................................. 2.23

Pilot Guide to Takeoff Safety

Table of Contents

Section Page

SECTION 2

2

2.i
2.3.5.3.4	 Wheels, Tires, and Brakes............................................................................ 2.25

2.3.5.3.5	 Worn Brakes................................................................................................. 2.27

2.3.5.3.6	 Residual Brake Energy ................................................................................. 2.28

2.3.5.3.7	 Speedbrake Effect on Wheel Braking........................................................... 2.28

2.3.5.3.8	 Carbon and Steel Brake Differences ............................................................ 2.30

2.3.5.3.9	 High Brake Energy RTOs............................................................................. 2.31

2.3.5.4	 Reverse Thrust Effects ...................................................................................... 2.32

2.3.5.5	 Runway Parameters........................................................................................... 2.33

2.3.5.6	 (Not Used)......................................................................................................... 2.34

2.3.5.7	 Takeoffs Using Reduced Thrust ........................................................................ 2.34

2.3.5.8	 The Takeoff Data the Pilot Sees........................................................................ 2.34

2.3.6	 Increasing the RTO Safety Margins........................................................................ 2.35

2.3.6.1	 Runway Surface Condition ............................................................................... 2.35

2.3.6.2	 Flap Selection.................................................................................................... 2.35

2.3.6.3	 Runway Lineup ................................................................................................. 2.36

2.3.6.4	 Setting Takeoff Thrust....................................................................................... 2.36

2.3.6.5	 Manual Braking Techniques.............................................................................. 2.37

2.3.6.6	 Antiskid Inoperative Braking Techniques......................................................... 2.38

2.3.6.7	 RTO Autobrakes................................................................................................ 2.38

2.3.6.8	 (Not Used)......................................................................................................... 2.39

2.3.6.9 	 The V1 Call........................................................................................................ 2.39

2.3.6.10	 Crew Preparedness............................................................................................ 2.40

2.4	 Crew Resource Management ...................................................................................... 2.40

2.4.1	 CRM and the RTO................................................................................................. 2.40

2.4.2 The Takeoff Briefing............................................................................................... 2.40

2.4.3	 Callouts................................................................................................................... 2.41

2.4.4	 The Use of All Crew Members............................................................................... 2.41

2.4.5	 Summary................................................................................................................. 2.42

Section Page

2.ii

SECTION 2
2.0 Introduction

The Pilot Guide to Takeoff Safety is one

part of the Takeoff Safety Training Aid. The other

parts include the Takeoff Safety Overview for

Management (Section 1), Example Takeoff

Safety Training Program (Section 3), Takeoff

Safety Background Data (Section 4), and an

optionalvideo.The subsectionnumberingused

in Sections 2 and 4 are identical to facilitate

cross referencing. Those sub sections not used

in Section 2 are noted “not used”.

The goal of the training aid is to reduce the

number ofRTOrelated accidents by improving

the pilot’s decision making and associated

procedural accomplishmentthroughincreased

knowledge and awareness of the factors

affectingthe successfuloutcomeofthe “Go/No

Go” decision.

T he educat ional mater ial and the

recommendations provided in the Takeoff 

Safety Training Aid were developed through an

extensive review processto achieve consensus

of the air transport industry.

2 .1 Objectives

The objective of the Pilot Guide to Takeoff

Safety is to summarize and communicate key

RTO related information relevant to flight 

crews. It is intended to be provided to pilots

during academic training and to be retained

for future use.

2.2 “Successful Versus Unsuccessful” Go/

No Go Decisions

Any Go/No Go decision can be considered

“successful” if it does not result in injury or

airplane damage. However, just because it was

“successful” by this definition, it does not mean 

the action was the “best” that could have been

taken. The purpose of this section is to point

out some of the lessons that have been learned

through the RTO experiences of other airline

crewssince the 1950s, and to recommendwa

of avoiding similar experiences by the pilots of

today’s airline fleet.

Pilot Guide to Takeoff Safety

Takeoffs, RTOs, and Overruns 

Through 2003 Typical Recent Year 

Takeoffs 430,000,000 18,000,000

RTOs (est.) 

RTO Overrun 

Accidents/Incidents

143,000 6,000

97 4*

• 1 RTO per 3,000 takeoffs

• 1 RTO overrun accident/incident per 4,500,000 takeoffs

*Accidents/incidents that would occur if historical rates continue.

Figure 1

Takeoffs, RTOs, 

and Overrun 

Statistics

2.1

SECTION 2

2
2.2.1 An In-service Perspective On Go/No Go 

Decisions

Modern jet transport services began in the

early 1950s and significantly increased later 

that decade after introduction of the Boeing

707 and the Douglas DC-8. As shown in

Figure 1, the western built jet transport fleet 

has accumulated approximately 430 million

takeoffsbythe endof2003.Recentlytherehave

beennearly18milliontakeoffsina typicalyear.

That’s approximately34takeoffs everyminute,

every day!

Since no comprehensive fleet-wide records 

are available, it is difficult to identify the total 

numberofRTOsthathaveoccurredthroughout

the jet era. However, based on those events

whichhavebeendocumented,ourbest estimate

is that one in 3,000 takeoff attempts ends with

an RTO. At this rate, there will be nearly 6000

RTOs during a typical year. That means that

every day, 16 flight crews will perform an RTO. 

Statistically, at the rate of one RTO per 3000

takeoffs, a pilot who flies short haul routes and 

makes80departurespermonth,willexperience

one RTO every three years. At the opposite

extreme, the long haul pilot making only eight

departures per month will be faced with only

one RTO every 30 years.

Theprobabilitythat apilotwill everbe required

to perform an RTO from high speed is even

less, as is shown in Figure 2.

Available data indicates that over 75% of all

RTOs are initiated atspeeds of 80 knots orless.

TheseRTOs almost neverresult in an accident.

Inherently, low speed RTOs are safer and less

demanding than high speedRTOs. At the other

extreme, about 2% of the RTOs are initiated

at speeds above 120 knots. Overrun accidents

and incidents that occur principally stem from

these high speed events.

What should all these statistics tell a pilot?

First, RTOs are not a very common event. This

speaks well of equipment reliability and the

preparationthatgoesintooperatingjettransport

airplanes. Both are, no doubt, due in large part

to the certification and operational standards 

developedbytheaviationcommunityovermany

yearsofoperation.Second,andmoreimportant,

the infrequency of RTO events may lead to

complacencyaboutmaintainingsharpdecision

making skills and procedural effectiveness. In

spite of the equipment reliability, every pilot 

must be prepared to make the correct Go/No 

Go decision on every takeoff-just in case.

SECTION 2

2.2

Figure 2

Distribution of 

RTO Initiation 

Speeds











KNOTS

ORLESS

TO

KNOTS

TO

KNOTS

!BOVE

KNOTS

0ERCENT

OFTOTAL





 

24/OVERRUN

ACCIDENTS

PRINCIPALLYCOME

FROMTHEOFTHE

24/STHATARE

HIGHSPEED
2.2.2 “Successful” Go/No Go Decisions

As was mentioned at the beginning of Section

2.2,thereismoretoa“good”Go/NoGodecision

than the fact that it may not have resulted in

any apparent injury or aircraft damage. The

following examples illustrate a variety of

situations that have been encountered in the

past, some of which would fit the description 

of a “good” decision, and some which are, at

least, “questionable”.

Listed at the beginning of each ofthe following

examples is the primary cause or cue which

prompted the crew to reject the takeoff:

1.	Takeoff Warning Horn: The takeoff

warning horn sounded as the takeoff roll

commenced. The takeoff was rejected

at 5 knots. The aircraft was taxied off

the active runway where the captain

discovered the stabilizer trim was set

at the aft end of the green band. The

stabilizer was reset and a second takeoff

was completed without further difficulty.

2.	Takeoff Warning Horn: The takeoff was

rejected at 90 knots when the takeoff

warning horn sounded. The crew found

the speed brake lever slightly out of

the detent. A normal takeoff was made

following a delay for brake cooling.

3.	Engine Power Setting: The throttles were

advanced and N1 increased to slightly

over 95%. N1 eventually stabilized

at 94.8% N1. The target N1 from the

FMC Takeoff Page was 96.8% N1. The

throttles were then moved to the firewall 

but the N1 stayed at 94.8%. The takeoff

was rejected due to low N1 at 80 knots.

4.	Compressor Stall: The takeoff was

rejected from 155 knots due to a bird

strike and subsequent compressor stall

on the number three engine. Most of the

tires subsequently deflated due to melted 

fuse plugs.

5.	Nose Gear Shimmy: The crew rejected

the takeoff after experiencing a nose

landing gear shimmy. Airspeed at the

time was approximately Vl

-10 knots. All

four main gear tires subsequently blew

during the stop, and fires at the number 3 

and 4 tires were extinguished by the fire 

department.

6.	Blown Tire: The takeoff was rejected at

140 knots due to a blown number 3 main

gear tire. Number 4 tire blew turning

onto the taxiway causing the loss of both

A and B hydraulic systems as well as

major damage to flaps, spar, and spoilers.

These examples demonstrate the diversity of

rejected takeoff causes.All oftheseRTOswere

“successful”, but some situations came very

close to ending differently. By contrast, the

large number of takeoffs that are successfully

continued with indications of airplane system

problemssuch as caution lightsthat illuminate

at high speed or tires that fail near V1, are

rarely ever reported outside the airline’s

own information system. They may result

in diversions and delays but the landings are

normally uneventful, and can be completed

using standard procedures.

This should not be construed as a blanket

recommendation to “Go, no matter what.” The

goal of this training aid is to eliminate RTO

accidents by reducing the number of improper

decisions that are made, and to ensure that the

correct procedures are accomplished when

an RTO is necessary. It is recognized that the

kind of situations that occur in line operations

are not always the simple problem that the

pilot was exposed to in training. Inevitably,

the resolution of some situations will only

be possible through the good judgment and

discretion of the pilot, as is exemplified in the 

following takeoff event:

After selecting EPR mode to set takeoff

thrust, the right thrust lever stuck at 1.21

EPR, while the left thrust lever moved to

SECTION 2

2.3
the target EPR of 1.34. The captain tried to

reject the takeoff but the right thrust lever

could not be moved to idle. Because the

light weight aircraft was accelerating very

rapidly, the Captain advanced the thrust on

the left engine and continued the takeoff.

The right engine was subsequently shut

down during the approach, and the flight 

was concluded with an uneventful single

engine landing.

The failure that this crew experienced was not

a standard training scenario. Nor is it included

here to encourage pilots to change their mind

in the middle of anRTO procedure.It issimply

an acknowledgment of the kind of real world

decision making situationsthat pilotsface.It is

perhaps more typical of the good judgements

that airline crewsregularlymake, but theworld

rarely hears about.

2.2.3 RTO Overrun Accidents and Incidents

The one-in-one-thousand RTOs that became

accidents or serious incidents are the ones

that we must strive to prevent. As shown in

Figure 3, atthe end of 2003,recordsshow57 inserviceRTO overrun accidentsforthe western

built jet transport fleet. These 57 accidents 

caused more than 400 fatalities. An additional

40 serious incidents have been identified which 

likely would have been accidentsifthe runway

overrun areas had been less forgiving. The

following are brief accounts of four actual

accidents.Theyare real events.Hopefully,they

will not be repeated.

ACCIDENT: At 154 knots, four knots after

V1, the copilot’s side window opened, and the

takeoff was rejected. The aircraft overran,

hitting a blast fence, tearing open the left wing

and catching fire.

ACCIDENT: The takeoff was rejected by the

captain when the first officer had difficulty 

maintaining runway tracking along the 7,000

footwetrunway.Initialreportsindicate thatthe

airplane had slowly accelerated at the start of

the takeoff roll due to a delay in setting takeoff

thrust. The cockpit voice recorder (CVR)

readout indicates there were no speed callouts

made during the takeoff attempt. The reject

speed was 5 knots above V1. The transition to

stopping was slower than expected. This was

to have been the last flight in a long day for the 

crew.Both pilotswere relatively inexperienced

in their respective positions. The captain had

about 140 hours as a captain in this airplane

type and the first officer was conducting 

0

5

10

1960 1965 1970 1975 1980

Year

1985 1990 1995 2000

Number 

of events 

per year

Figure 3 

97 RTO overrun 

accidents/incidents 

1959-2003

SECTION 2

2.4
his first non-supervised line takeoff in this 

airplane type.The airplanewasdestroyedwhen

it overran the end of the runway and broke

apart against piers which extend off the end

of the runway into the river. There were two

fatalities. Subsequent investigation revealed

that the rudder was trimmed full left prior to

the takeoff attempt.

ACCIDENT: A flock of sea gulls was

encountered “very near V1.” The airplane

reportedly had begun to rotate. The number

one engine surged and flamed out, and the 

takeoff was rejected. The airplane overran

the end of the wet 6,000 foot runway despite a

good RTO effort.

ACCIDENT: At 120 knots, the flight crew noted 

the onset of a vibration. When the vibration

increased, the captain elected to reject and

assumed control. Fourto eightseconds elapsed

between the point where the vibration was first 

noted and when the RTO was initiated (just

afterV1).Subsequentinvestigationshowedtwo

tires had failed. The maximum speed reached

was 158 knots. The airplane overran the end of

the runway at a speed of 35 knots and finally 

stoppedwith the nose in a swamp.The airplane

was destroyed.

These four cases are typical of the 97 reported

accidents and incidents.

2.2.4 Statistics

Studies of the previously mentioned 97

accidents/incidents have revealed some

interesting statistics, as shown in Figure 4:

• Fifty-five percent were initiated at speeds 

in excess of V1.

•	 Approximately one third were reported as

having occurred on runways that were wet

or contaminated with snow or ice.

Both of these issues will be thoroughly

discussed in subsequent sections.

An additional, vitally interesting statistic

that was observed when the accident

records involving Go/No Go decisions were

reviewed, was that virtually no revenue

flight was found where a “Go” decision

was made and the airplane was incapable

of continuing the takeoff. Regardless of the

ability to safely continue the takeoff, as will be

seen inSection 2.3, virtually any takeoff can be

“successfully” rejected, ifthe reject isinitiated

early enough and is conducted properly. There

is more to the Go/No Go decision than “Stop

before V1” and “Go after V1.” The statistics of

the past three decades show that a number of

jet transports have experienced circumstances

near V1 that rendered the airplane incapable of

being stopped on the runway remaining.It also Figure 4

Major factors 

in previous RTO 

incidents and 

accidents

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SECTION 2

2.5
must be recognized that catastrophic situations

couldoccurwhichrenderthe airplane incapable

of flight.

Reasons why the 97 “unsuccessful” RTOs

were initiated are also of interest. As shown

in Figure 5, approximately one-fifth were 

initiated because of engine failures or engine

indication warnings. The remaining seventynine percent were initiated for a variety of

reasonswhichincludedtire failures,procedural

error, malfunction indication or lights, noises

and vibrations, directional control difficulties 

and unbalanced loading situations where the

airplane failed to rotate. Some of the events

contained multiple factors such as an RTO on

a contaminated runway following an engine

failure at a speed in excess of V1. The fact that

the majority of the accidents and incidents

occurred on airplanes that had full thrust

available should figure heavily in future Go/No 

Go training.

2.2.5 Lessons Learned

Several lessons can be learned from these

RTO accidents. First, the crew must always

be prepared to make the Go/No Go decision

prior to the airplane reaching V1 speed. As

will be shown in subsequent sections, there

may not be enough runway left to successfully

stop the airplane if the reject is initiated after

V1. Second, in order to eliminate unnecessary

RTOs, the crew must differentiate between

situationsthat are detrimental to a safe takeoff,

and those that are not. Third, the crew must be

prepared to act as a well coordinated team. A

good summarizing statement of these lessons

is, as speed approaches V1, the successful 

completion of an RTO becomes increasingly 

more difficult.

A fourth and final lesson learned from past 

RTO history isillustrated in Figure 6. Analysis

of the available data suggests that of the 97

Figure 5

Reasons for 

initiating the RTO 

(97 accidents/

incident events)

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SECTION 2

2.6
RTO accidents and incidents, approximately

82% were potentially avoidable through

appropriate operational practices. These

potentially avoidable accidents can be divided

into three categories.Roughly 15% oftheRTO

accidents ofthepastwere the resultofimproper

preflight planning. Some of these instances 

were caused by loading errors and others by

incorrect preflight procedures. About 15% of 

the accidents and incidents could be attributed

to incorrect pilot techniques or procedures in

the stopping effort. Delayed application of the

brakes, failure to deploy the speedbrakes, and

the failure tomake amaximumeffortstop until

late in the RTO were the chief characteristics

of this category.

Review of the data from the 97 RTO accidents

and incidents suggests that in approximately

52% of the events, the airplane was capable of

continuing the takeoff and eitherlanding at the

departure airportordivertingtoanalternate.In

other words, the decision to reject the takeoff

appears to have been “improper.” It is not

possible,however,topredictwithtotal certainty

whatwould have happened in every eventifthe

takeoff had been continued. Nor is it possible

for the analyst of the accident data to visualize

the events leading up to a particular accident

“through the eyesofthe crew”,includingallthe

otherfactorsthat were vying fortheir attention

at the moment when the “proper” decision

could have been made. It is not very difficult 

to imagine a set of circumstances where the

only logical thing for the pilot to do is to reject

the takeoff. Encountering a large flock of birds 

at rotation speed, which then produces loss of

thrust on both engines of a two engine airplane,

is a clear example.

Although these are all valid points, debating

them here will not move us any closer to

the goal of reducing the number of RTO

accidents.Severalindustrygroupshaverecently

studied this problem. Their conclusions and

recommendations agree surprisinglywell.The

areas identified as most in need of attention are 

decision making and proficiency in correctly 

performing the appropriate procedures. These

are the same areas highlighted in Figure 6.

It would appear then, that an opportunity

exists to significantly reduce the number of 

RTO accidents in the future by attempting to

improve the pilots’ decision making capability

and procedure accomplishment through better

training.

2.3 Decisions and Procedures—

What Every Pilot Should Know

Therearemanythingsthatmayultimatelyaffect

theoutcomeofaGo/NoGodecision.Thegoalof

theTakeoffSafetyTrainingAid isto reduce the

number ofRTO related accidents and incidents

by improving the pilot’s decision making and

associatedprocedure accomplishmentthrough

increased knowledge and awareness of the

related factors. This section discusses the

rules that define takeoff performance limit 

weights and the margins that exist when the

actual takeoff weight of the airplane is less

Figure 6

82% of the RTO 

accidents and 

incidents were 

avoidable



"YBETTERPREFLIGHT

PLANNING



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TECHNIQUES

SECTION 2

2.7
than the limit weight. The effects of runway

surface condition, atmospheric conditions, and

airplane configuration variables on Go/No Go 

performance are discussed, as well as what the

pilot can do to make the best use of any excess

available runway.

Although the information contained in this

section has been reviewed by many major

airframe manufacturers and airlines, the

incorporation of any of the recommendations

made in this section is subject to the approval

of each operator’s management.

2.3.1 The Takeoff Rules —

The Source of the Data

It is important that all pilots understand the

takeoff field length/weight limit rules and the 

marginsthese rulesprovide.Misunderstanding

the rules andtheir applicationtotheoperational

situation could contribute to an incorrect

Go/No Go decision.

The U.S. Federal AviationRegulations(FARs)

have continually been refined so that the details 

of the rules that are applied to one airplane

model may differ from another. However,

these differences are minor and have no effect

on the basic actions required of the flight 

crew during the takeoff. In general, it is more

important for the crew to understand the basic

principles rather than the technical variations

in certification policies.

2.3.1.1 The “FAR” Takeoff Field Length

The “FAR” Takeoff Field Length determined

from the FAA Approved Airplane Flight

Manual (AFM) considers the most limiting of

each of the following three criteria:

1) All-Engine Go Distance: 115% of t

actual distance required to accelerate,

liftoff and reach a point 35 feet above

the runway with all engines operating

(Figure 7).

2) Engine-Out Accelerate-Go Distance:

The distance required to accelerate with

all engines operating, have one engine

fail at VEF at least one second before V1,

continue the takeoff, liftoff and reach a

point 35 feet above the runway surface

at V2 speed (Figure 8).

3) Accelerate-Stop Distance: The distan

required to accelerate with all engines

operating, have an engine failure or

other event at VEVENT at least one

second before V1, recognize the event,

reconfigure for stopping and bring 

the airplane to a stop using maximum

wheel braking with the speed brakes

extended. Reverse thrust is not used

to determine the FAR accelerate-stop

distance (Figure 9), except for the wet

runway case for airplanes certified under 

FAR Amendment 25-92.

FAR criteria provide accountability for

wind, runway slope, clearway and stopway.

FAA approved takeoff data are based on the

performance demonstrated on a smooth, dry

runway. Recent models certified according to 

FARAmendment25-92alsohaveapproveddata

based on wet, and wet skid-resistant runways.

Separate advisory data for wet, if required, or

contaminatedrunwayconditions arepublished

in the manufacturer’s operational documents.

These documents are used by many operators

to derive wet or contaminated runway takeoff

adjustments..

Other criteria define the performance weight 

limitsfortakeoff climb, obstacle clearance,tire

speeds and maximum brake energy capability.

Any of these other criteria can be the limiting

factorwhichdeterminesthemaximumdispatch

weight.However,theFieldLengthLimitWeight

and the amount ofrunway remaining at V1 will

be the primary focus of our discussion here

since they more directly relate to preventing

RTO overruns.

SECTION 2

2.8
!CTUAL$ISTANCE

TIMESTHEACTUALDISTANCE

sFEET

s6TOKNOTS

sFEET

s6

SECONDMINIMUM

6%& 62 6,/&

6

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SECTION 2

2.9

Figure 7

All-engine go 

distance

Figure 8

Engine-out 

accelerate-go 

distance

Figure 9

Accelerate-stop 

distance

24/TRANSITION

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2.3.1.2 V1 Speed Defined

V

1

What is the proper operational meaning of the

key parameter “V1 speed” with regard to the

Go/No Go criteria? This is not such an easy

question since the term “V1 speed” has been

redefined several times since commercial jet 

operations began more than 30 years ago and

there is possible ambiguity inthe interpretation

of the words used to define V1.

Paragraph 25.107 of the FAA Regulations

defines the relationship of the takeoff speeds 

published in the Airplane Flight Manual, to

various speeds determined in the certification 

testing of the airplane. For our purposes here,

the most important statement within this

“official” definition is that V1 isdeterminedfrom

“...the pilot’s initiation of the first action to stop 

the airplane during the accelerate-stop tests.”

One common and misleading way to think of

V1 is to say “V1 is the decision speed.” This is

misleading because V1 is not the point to begin

makingtheoperationalGo/NoGodecision.The 

decision must have been made by the time the 

airplane reaches V1 or the pilot will not have

initiated the RTO procedure at V1. Therefore,

by definition, the airplane will be traveling at 

a speed higher than V1 when stopping acti

is initiated, and if the airplane is at a Field

Length Limit Weight, an overrun is virtually

assured.

Another commonly heldmisconception: “V1 is

the engine failure recognition speed”,suggests

that the decision to reject the takeoff following

engine failure recognition may begin aslate as

V1. Again, the airplane will have accelerated to

a speed higher than VI before stopping action

is initiated.

The certified accelerate-stop distance calculation 

is based on an engine failure atleast one second

prior to V1. This standard time allowance1

has been established to allow the line pilot

to recognize an engine failure and begin the

subsequent sequence of stopping actions.

InanoperationalFieldLengthLimitedcontext,

the correct definition of V1 consists of two

separate concepts:

First, with respect to the “No Go” criteria,

V1 is the maximum speed at which 

the rejected takeoff maneuver can 

be initiated and the airplane stopped 

within the remaining field length under 

the conditions and procedures defined 

1

	The time interval between VEF and Vl is the longer of the flight test demonstrated time or one second. Therefore, in determining 

the scheduled accelerate-stop performance, one second is the minimum time that will exist between the engine failure and the

first pilot stopping action.

SECTION 2

2.10
in the FAR’s. It is the latest point in 

the takeoff roll where a stop can be 

initiated.

Second, with respect to the “Go” criteria,

V1 is also the earliest point from which 

an engine out takeoff can be continued 

and the airplane attain a height of 35 

feet at the end of the runway. This aspect

of V1 is discussed in a later section.

The Go/ No Go decision must be made before

reachingV1.A “No Go” decision after passing 

V1 will not leave sufficient runway remaining 

to stop if the takeoff weight is equal to the 

Field Length Limit Weight.Whentheairplane

actual weight is less than the Field Length

Limit Weight, it is possible to calculate the

actualmaximumspeed fromwhich the takeoff

could be successfully rejected. However, few

operators use such takeoff data presentations.

Itistherefore recommendedthatpilots consider

V1 to be a limit speed: Do not attempt an RTO

once the airplane has passed V1 unless the

pilot has reason to conclude the airplane is

unsafe or unable to fly. This recommendation 

should prevail no matter what runway length 

appears to remain after V1.

2.3.1.3 Balanced Field Defined

The previous two sections established the

general relationship between the takeoff

performance regulations and V1 speed. This

section provides a closer examination of how

the choice of V1 actually affects the takeoff

performance in specific situations.

Since it is generally easierto change the weight

of an airplane than it is to change the length

of a runway, the discussion here will consider

the effect of V1 on the allowable takeoff weight

from a fixed runway length.

The Continued Takeoff—After an engine

failure during the takeoff roll, the airplane

must continue to accelerate on the remaining

engine(s), lift off and reach V2 speed at 35 feet.

The later in the takeoff roll that the engine

fails, the heavier the airplane can be and still

gain enough speed to meet this requirement.

Forthe engine failure occurring approximately

one second prior to V1, the relationship of the

allowable engine-out go takeoff weight to V1

would be asshown by the “ContinuedTakeoff”

line in Figure 10.The higherthe V1, the heavier

the takeoff weight allowed.

TheRejected Takeoff— On the stop side ofthe

equation, the V1/weight trade has the opposite

trend. The lower the V1, or the earlier in the

takeoff roll the stop isinitiated, the heavier the

airplane can be, as indicated by the “Rejected

Takeoff” line in Figure 10.

Thepoint atwhichthe “ContinuedandRejected

Takeoff” linesintersect is ofspecial interest. It

defines what is called a “Balanced Field Limit” 

Figure 10

Effect of V1 speed 

on takeoff weight 

(from a fixed 

runway length)

Continued

takeoff

Rejected

takeoff

Airplane

weight

V speed 1

Increasing

Increasing

Field limit weight

Balanced field

Limit V speed 1

SECTION 2

2.11
takeoff. The name “Balanced Field” refers to

the fact that the accelerate-go performance

required is exactly equal to (or “balances”)

the accelerate-stop performance required.

From Figure 10 it can also be seen that at the

“Balanced Field” point, the allowable Field

Limit Takeoff Weight for the given runway is

the maximum. The resulting unique value of

V1 is referred to as the “Balanced Field Limit

V1 Speed” and the associated takeoff weight

is called the “Balanced Field Weight Limit.”

This is the speed that is typically given to flight 

crews in handbooks or charts, by the onboard

computer systems, or by dispatch.

2.3.1.4 (Not Used)

2.3.2 Transition to the Stopping Configuration

In establishing the certified accelerate-stop 

distance, the time required to reconfigure the 

airplane from the “Go” to the “Stop” mode

is referred to as the “transition” segment.

This action and the associated time of

accomplishment includes applying maximum

braking simultaneously moving the thrust

levers to idle and raising the speedbrakes.

The transition time demonstrated by flight 

test pilots during the accelerate-stop testing

is used to derive the transition segment times

used in theAFMcalculations.The relationship

between the flight test demonstrated transition 

times and those finally used in the AFM is 

anotherfrequentlymisunderstood area ofRTO

performance.

2.3.2.1 Flight Test Transitions

Several methods of certification testing that 

produce comparable results have been found to

beacceptable.Thefollowingexampleillustrates

the intent of these methods.

During certification testing the airplane is 

accelerated to a pre-selected speed, one engine

is “failed” by selecting fuel cut off, and the

pilot flying rejects the takeoff. In human 

factors circles, this is defined as a “simple task” 

because the test pilot knowsin advance that an

RTO will be performed. Exact measurements

of the time taken by the pilot to apply the

brakes, retard the thrust levers to idle, and to

deploy the speedbrakes are recorded. Detailed

measurements of engine parameters during

spooldown are also made so that the thrust

actually being generated can be accounted for

in the calculation.

The manufacturer’s test pilots, and pilots

from the regulatory agency, each perform

several rejected takeoff test runs. An average

of the recorded data from at least six of

these RTOs is then used to determine the

“demonstrated” transition times. The total flight 

test“demonstrated”transitiontime,initialbrake

application to speedbrakes up, is typically one

second or less. However this is not the total

transition time used to establish the certified 

accelerate-stop distances. The certification 

regulationsrequire that additional time delays,

sometimesreferred to as “pads”, be included in

the calculation of certified takeoff distances.

2.3.2.2 Airplane Flight Manual Transition 

Times

Although the line pilot must be prepared for

an RTO during every takeoff, it is fairly likely

that the event or failure prompting the Go/No

Go decision will be much less clear-cut than

an outright engine failure. It may therefore be

unrealistic to expect the average line pilot to

perform the transition in aslittle as one second

in an operational environment. Human factors

literature describes the line pilot’s job as a

“complex task” since the pilot does not know

when an RTO will occur. In consideration of

this “complex task”, the flight test transition 

times are increased to calculate the certified 

accelerate-stop distances specified in the AFM. 

These additional time increments are not 

SECTION 2

2.12
intended to allow extra time for making the 

“Go/No Go” decision after passing V1. Their

purpose is to allow sufficient time (and distance) 

for “the average pilot” to transition from the

takeoff mode to the stopping mode.

The first adjustment is made to the time required 

to recognize the need to stop. During the RTO

certification flight testing, the pilot knows 

that he will be doing an RTO. Therefore, his

reaction is predictably quick. To account for

this, an event recognition time of at least one

second has been set as a standard for all jet

transport certifications since the late 1960s. 

V1 is therefore, at least one second after the

event. During this recognition time segment,

the airplane continues to accelerate with the

operating engine(s) continuing to provide full

forward thrust. If the event was an engine

failure, the “ failed” engine has begun to spool

down, but it is still providing some forward

thrust, adding to the airplane’s acceleration.

Over the years, the details of establishing the

transition time segments after V1 have varied

slightlybuttheoverall concept andthe resulting

transition distances have remained essentially

the same. For early jet transport models, an

additional one second was added to both the

flight test demonstrated throttles-to-idle time 

and the speedbrakes-up time, as illustrated

in Figure 11. The net result is that the flight 

test demonstrated recognition and transition

time of approximately one second has been

increased for the purpose of calculating the

AFM transition distance.

In more recent certification programs, the AFM 

calculation procedure was slightly different.

An allowance equal to the distance traveled

duringtwosecondsatthespeedbrakes-upspeed

was added to the actual total transition time

demonstrated in the flight test to apply brakes, 

bring the thrust levers to idle and deploy the

speedbrakes, as shown in Figure 12. To insure

“consistent and repeatable results”, retardati

forces resulting from brake application and

speed brake deployment are not applied

during this two second allowance time, i.e. no

deceleration credit is taken. This two second

distance allowance simplifies the transition 

distance calculationandaccomplishesthe same

goal as the individual one second “pads” used

Figure 11

Early method of 

establishing AFM 

transition time

!&-TRANSITION

COMPLETE

&LIGHTTEST

%NGINE

&AILURE

!&-EXPANSION

&LIGHTTESTDEMONSTRATEDTRANSITIONTIME

!&-TRANSITIONTIME

!&-

SECOND

MINIMUM

SEC SEC

2ECOGNITION

6

"RAKESON

4HROTTLESTOIDLE

3PEEDBRAKES

SECTION 2

2.13
for older models.

Even more recently, FAR Amendments 25-42

and 25-92 have revised the way in which the

two second distance allowance is calculated.

Regardless of the method used, the acceleratestop distance calculated for every takeofffrom

theAFMistypically400to600feetlongerthan

the flight test accelerate-stop distance. 

These differences between the past and present

methodology are not significant in so far as 

the operational accelerate-stop distance is

concerned.The keypoint is that the time/distance 

“pads” used in the AFM transition distance 

calculation are not intended to allow extra time 

to make the “No Go” decision. Rather,the “pads”

provide an allowance that assures the pilot has

adequate distance to get the airplane into the

full stopping configuration.

Regardlessofthe airplanemodel,the transition,

or reconfiguring of the airplane for a rejected 

takeoff, demands quick action by the crew to

simultaneously initiate maximum braking,

retard the thrust leversto idle and then quickly

raise the speedbrakes.

2.3.3 Comparing the “Stop” and “Go” 

Margins

When performing a takeoff at a Field Length

Limit Weight determined from the AFM, the

pilot is assured that the airplane performance

will, at the minimum, conform to the

requirements of the FARs if the assumptions

of the calculations are met. This means that

following an engine failure or event at VEVENT,

the takeoff canbe rejectedatV1 andthe airplane

stoppedatthe endofthe runway,orifthe takeoff

is continued, a minimum height of 35 feet will

be reached over the end of the runway.

Thissectiondiscussestheinherentconservatism

of these certified calculations, and the margins 

they provide beyond the required minimum

performance.

Figure 12

More recent 

method of 

establishing AFM 

transition time

!&-TRANSITION

COMPLETE

&LIGHTTEST

!&-EXPANSION

&LIGHTTESTDEMONSTRATEDTRANSITIONTIME

!&-TRANSITIONTIME

!&-

SECOND

MINIMUM

&4

DEMO

SEC

2ECOGNITION

6

"RAKESON

4HROTTLESTOIDLE

3PEEDBRAKES

3ERVICEALLOWANCE

%VENT

SECTION 2

2.14
2.3.3.1 The “Stop” Margins

From the preceding discussion of the

certification rules, it has been shown that at 

a Field Length Limit Weight condition, an

RTO initiated at V1 will result in the airplane

coming to a stop at the end of the runway. This

accelerate-stop distance calculation specifies an 

engine failure or event at VEVENT, the pilot’s

initiation of the RTO at V1, and the completion

of the transition within the time allotted in the

AFM.If any ofthese basic assumptions are not

satisfied, the actual accelerate-stop distance 

may exceed the AFM calculated distance, and

an overrun will result. 	 	

The most significant factor in these assumptions 

is the initiation of the RTO no later than V1.

Yet as was noted previously, in approximately

55%oftheRTOaccidentsthe stopwasinitiated

afterV1.At heavyweights nearV1, the airplane

is typically traveling at 200 to 300 feet per

second, and accelerating at 3 to 6 knots per

second. This means that a delay of only a

second ortwo in initiating theRTOwillrequire

several hundred feet of additional runway to

successfully complete the stop. If the takeoff

was at a Field Limit Weight, and there is no

excessrunwayavailable,the airplanewillreach

the end of the runway at a significant speed, as 

shown in Figure 13.

The horizontal axis of Figure 13 is the

incremental speed in knots above V1 at which

a maximum effortstop isinitiated. The vertical

axisshowstheminimum speedinknots atwhich

the airplane would crossthe end ofthe runway,

assuming the pilot used all of the transition

time allowed in the AFM to reconfigure the 

airplane to the stop configuration, and that a 

maximumstoppingeffortwasmaintained.The

data in Figure 13 assumes an engine failure not

less than one second prior to V1 and does not

include the use of reverse thrust. Therefore, if

the pilot performs the transition more quickly

thantheAFMallottedtime, and/orusesreverse

thrust,the line labeled“MAXIMUMEFFORT

STOP” would be shifted slightly to the right.

However, based on the RTO accidents of the

past, the shaded area above the line shows what

is more likely to occur if a high speed RTO is

initiatedatorjustafterV1.Thisisespeciallytrue

if the RTO was due to something other than an

engine failure, or if the stopping capability of

the airplane is otherwise degraded by runway

surface contamination, tire failures, or poor

technique.The data inFigure 13 are typical of a

large, heavy jet transport and would be rotated

slightly to the right for the same airplane at a

lighter weight.	

In the final analysis, although the certified 

accelerate-stop distance calculations provide

Figure 13

Overrun Speed for 

an RTO initiated 

after V1













!BORTINITIATIONSPEEDABOVESCHEDULED6KNOTS	

3PEEDOFFENDOF -AXIMUMEFFORTSTOP

RUNWAYKNOTS	

3HADEDAREAINDICATESDEGRADED

STOPPINGPERFORMANCE

s#ONTAMINATEDRUNWAY

s0ILOTTECHNIQUE

s3YSTEMFAILURES

 

SECTION 2

2.15
sufficient runway for a properly performed 

RTO, the available margins are fairly small.

Most importantly, there are no margins to

account for initiation of the RTO after V1 or

extenuating circumstances such as runway

contamination.	

2.3.3.2 The “Go” Option

FARrulesalsoprescribeminimumperformance

standardsforthe “Go” situation.Withanengine

failedatthemost criticalpoint alongthe takeoff

path, the FAR “Go” criteria requires that the

airplanebe able tocontinue toaccelerate,rotate,

liftoffandreachV2 speedatapoint35feetabove

the endofthe runway.The airplanemustremain

controllable throughoutthismaneuverandmust

meet certain minimum climb requirements.

These handling characteristics and climb

requirements are demonstrated many times

throughout the certification flight test program. 

While a great deal of attention is focused on

the engine failure case, it is important to keep

in mind, that in over three quarters of all RTO 

accident cases, full takeoff power was available. 

It is likely that each crew member has had a

good deal of practice in engine inoperative

takeoffsin priorsimulator or airplane training.

However, it may have been done at relatively

lighttrainingweights.As a result,the crewmay

conclude that large control inputs and rapid

response typical of conditions near minimum

control speeds (Vmcg) are always required in

ordertomaintain directional control.However,

at the V1 speeds associated with a typical

Field Length Limit Weight, the control input

requirements are noticeably less than they are

at lighter weights.

Also, at light gross weights, the airplane’s

rate of climb capability with one-engine

inoperative could nearly equal the all-engine

climb performance at typical in-service

weights, leading the crew to expect higher

performance than the airplane will have if the

actual airplane weight is at or near the takeoff

Climb Limit Weight. Engine-out rate of climb

and acceleration capability at a Climb Limit

Weightmay appearto be substantially lessthan

the crew anticipates or is familiar with.

Theminimumsecondsegment climbgradients

required in the regulations vary from 2.4%

to 3.0% depending on the number of engines

installed. These minimum climb gradients

translate into a climb rate of only 350 to 500

feet per minute at actual climb limit weights

and their associated V2 speeds, as shown in

Figure 14. The takeoff weight computations

performed prior to takeoff are required to

account for all obstacles in the takeoff flight 

path. All that is required to achieve the

anticipated flight path is adherence by the flight 

crew to the planned headings and speeds per

their pre-departure briefing.

Consider a one-engine-inoperative case

where the engine failure occurs earlier than

the minimum time before V1 specified in 

the rules. Because engine-out acceleration is

less than all-engine acceleration, additional

distance is needed to accelerate to VR and,

as a consequence, the liftoff point will be

moved further down the runway. The altitude

(or “screen height”) achieved at the end of the

runway is somewhat reduced depending on

how much more than one second before V1 the

engine failure occurs. On a field length limit 

runway, the height at the end of the runway

may be less than the 35 feet specified in the 

regulations.

Figure 15 graphically summarizes this

discussion of “Go” margins. First, let VEF

be the speed at which the Airplane Flight

Manual calculation assumesthe engine to fail,

(a minimum of one second before reaching

V1). The horizontal axis of Figure 15 shows

the number of knots prior to VEF that the

SECTION 2

2.16
engine actually fails instead of the time, and

the vertical axis gives the “screen height”

achieved at the end of the runway. A typical

range of acceleration for jet transportsis 3 to 6

knots persecond,so the shaded area showsthe

range in screen height that might occur if the

engine actually failed “one second early”, or

approximately two seconds priortoV1.In other

words, a “Go” decision made with the engine

failure occurring two seconds prior to V1 will

result in a screen height of 15 to 30 feet for a

Field Length Limit Weight takeoff.

Figure15alsoshowsthatthe “Go”performance

margins are strongly influenced by the number 

of engines. Thisis again the result of the larger

proportion of thrust loss when one engine fails

on the two-engine airplane compared to a

-20 -16 -12 -8 -4 0

0

10

20

30

40

(35)

(150)

One-engine inoperative 

All engines 

2-engine airplane 

Height at end 

of runway, ft 

Speed at actual engine failure 

relative to VEF, knots 

V2 + 10 to 25 knots 

V2

+4 +8

Typical 

V1 range 

One second 

minimum

4-engine airplane 

3-engine airplane 

&0-AT6 ^KNOTS

&0-AT6 ^KNOTS

&0-AT6 ^KNOTS

-INIMUM

GRADIENT

REQUIRED


ENGINE 


ENGINE 


ENGINE 

4YPICALRATEOFCLIMB


DEGREEBANKTURNWILLREDUCETHESE

CLIMBRATESBYAPPROXIMATELY&0-

Figure 14

“GO” perfomance 

at climb limit 

weights

Figure 15

Effect of engine 

failure before VEF

on screen height

SECTION 2

2.17
three or four-engine airplane. On two-engine

airplanes, there are still margins, but they are

not as large, a fact that an operator of several

airplane types must be sure to emphasize in

training and transition programs.

It should also be kept in mind that the 15

to 30 foot screen heights in the preceding

discussion were based on the complete loss

of thrust from one engine. If all engines are

operating, as was the case in most of the

RTO accident cases, the height over the end

of the Field Length Limit runway will be

approximately 150 feet and speed will be

V2+10 to 25 knots, depending on airplane

type. Thisis due to the higher acceleration and

climb gradient provided when all engines are

operating and because the required all engine

takeoff distance is multiplied by 115%. If the

“failed” engine is developing partial power,

the performance is somewhere in between,

but definitely above the required engine-out 

limits.

2.3.4 Operational Takeoff Calculations

As we have seen, the certification flight testing, 

inaccordancewiththe appropriategovernment

regulations, determines the relationship

between the takeoff gross weight and the

requiredrunwaylengthwhichispublishedinthe

AFM. By using the data in the AFM it is then

possible to determine, for a given combination

of ambient conditions and airplane weight, the

required runway length which will comply

with the regulations. Operational takeoff

calculations, however, have an additional and

obviously different limitation. The length of

the runway is the Limit Field Length and it is

fixed, not variable.

2.3.4.1 The Field Length Limit Weight

Instead of solving for the required runway

length, the first step in an operational takeoff 

calculation is to determine the maximum

airplane weight which meets the rules for

the fixed runway length available. In other 

words, what is the limit weight at which the

airplane:	 	

1) Will achieve 35-ft altitude with all

engines operating and a margin of 15 %

of the actual distance used remaining;

2) Will achieve 35-ft altitude with the

critical engine failed one second prior

to V1;

3) Will stop with an engine failure or other

event prior to V1 and the reject initiated

at V1;	

...all within the existing runway length

available.

The result of this calculation isthree allowable

weights.These threeweightsmayormaynotbe

the same,butthe lowestofthe threebecomesthe

Field Length Limit Weight for that takeoff.

An interesting observation can be made at this

point as to which of these three criteria will

typically determine the Takeoff Field Limit

Weight for a given airplane type. Two-engine

airplanes lose one-half their total thrust when

an engine fails. As a result, the Field Length

LimitWeightfortwo-engineairplanesisusually

determined by one of the engine-out distance

criteria. If it is limited by the accelerate-stop

distance, there will be some margin in both

the all-engine and accelerate-go distances. If

the limit is the accelerate-go distance, some

margin would be available for the all-engine

go and accelerate-stop cases.

By comparison, four-engine airplanes only

lose one-fourth of their takeoff thrust when an

engine failssotheyare rarelylimitedbyengineout go performance. The Field Length Limit

SECTION 2

2.18
Weight for a four-engine airplane is typically

limitedbythe115%all-enginedistance criteria

or occasionally by the accelerate-stop case. As

a result, a slight margin frequently existsin the

engine-out go and accelerate-stop distances on

four-engine airplanes.

Three-engine airplanes may be limited by

engine-outperformance,orforsomemodels,by

a more complex criterion wherein the rotation

speed VR becomes the limiting factor. Since

the regulations prohibit V1 from exceeding

VR, some tri-jets frequently have V1=VR, and

a small margin may therefore exist in the

accelerate-stopdistance.Two-engine airplanes

may occasionally be limited by this V1=VR

criterion also.

The possible combinations of airport pressure

altitude, temperature, wind, runway slope,

clearway, and stopway are endless. Regardless

of airplane type, they can easily combine to

make any one ofthe three previously discussed

takeoff field length limits apply. Flight crews 

havenoconvenientmethodtodeterminewhich

of the three criteria is limiting for a particular

takeoff, and from a practical point of view, it

really doesn’t matter. The slight differences

that may exist are rarely significant. Most RTO 

overrun accidents have occurred on runways

where the airplane was not at a limit takeoff

weight. That is, the accidents occurred on

runwaysthat were longer than required for the

actualtakeoffweight.Combiningthishistorical

evidencewiththedemandingnatureofthehigh

speed rejected takeoff, it would seem prudent

that the crew should always assume the takeoff

is limited by the accelerate-stop criteria when

the takeoff weight is Field Length Limited.

2.3.4.2 Actual Weight Less Than Limit 

Weight

Returningtotheoperationaltakeoffcalculation,

the second step is to then compare the actual

airplane weight to the Field Length Limit

Weight. There are only two possible outcomes

of this check.	

1) The actual airplane weight could equal or

exceed the Field Length Limit Weight, or

2) The actual airplane weight is less than the

Field Length Limit Weight.	

The first case is relatively straightforward, 

the airplane weight cannot be greater than the

limit weight and must be reduced. The result

is a takeoff at a Field Length Limit Weight as

we have just discussed.The second case,which

is typical of most jet transport operations, is

worthy of further consideration.	

By far, the most likely takeoff scenario for the

line pilot is the case where the actual airplane

weight islessthan any limit weight, especially

theFieldLengthLimitWeight.It alsoispossibly

the most easily misunderstood area of takeoff

performance since the fact that the airplane is

not at a limit weight is about all the flight crew 

candeterminefromthedatausuallyavailableon

the flight deck. Currently, few operators provide 

anyinformationthatwillletthe crewdetermine

how much excess runway is available; what it

means in terms of the V1 speed they are using;

or how to best maximize the potential safety

margins represented by the excess runway.

2.3.5 Factors that Affect Takeoff and RTO 

Performance

Both the continued and the rejected takeoff

performancearedirectlyaffectedbyatmospheric

conditions, airplane configuration, runway 

characteristics, engine thrust available, and

by human performance factors. The following

sections review the effects of these variables

on airplane performance. The purpose is not

to make this a complete treatise on airplane

performance. Rather, it is to emphasize that

changes in these variables can have a significant 

impact on a successful Go/ No Go decision. In

many instances, the flight crew has a degree of 

direct control over these changes.

SECTION 2

2.19
2.3.5.1 Runway Surface Condition

The condition of the runway surface can have

a significant effect on takeoff performance, 

since it can affect both the acceleration and

deceleration capability of the airplane. The

actualsurfaceconditioncanvaryfromperfectly

dry to a damp, wet, heavy rain, snow, or slush

covered runway in a very shorttime.The entire

length of the runway may not have the same

stopping potential due to a variety of factors.

Obviously, a 10,000-ft runway with the first 

7,000 feet bare and dry, but the last 3,000 feet

a sheet of ice, does not present a very good

situation for a high speed RTO. On the other

hand, there are also specially constructed

runways with a grooved or Porous Friction

Coat (PFC) surface which can offer improved

braking under adverse conditions. The crews

cannot control the weather like they can the

airplane’s configuration or thrust. Therefore, to 

maximize both the “ Go” and “ Stop” margins,

they must rely on judiciously applying their

company’swetorcontaminatedrunwaypolicies

as well as their own understanding of how the

performance of their airplane may be affected

by a particular runway surface condition.

The certification testing is performed on a 

smooth, ungrooved, dry runway. For airplanes

certified under FAR Amendment 25-92, testing 

is also performed on smooth and grooved wet

runways.Anycontaminationnot coveredinthe

certification data which reduces the available 

frictionbetweenthe tire andthe runwaysurface

willincrease the required stopping distance for

an RTO. Runway contaminants such as slush

orstanding water can also affect the continued

takeoff performance due to “displacement

and impingement drag” associated with the

spray from the tires striking the airplane.

Some manufacturers provide advisory data for

adjustment of takeoff weight and/or V1 when

the runway is wet or contaminated. Many

operators use this data to provide flight crews 

with amethod of determining the limit weights

for slippery runways.

Factors that make a runway slippery and how

theyaffectthe stoppingmaneuver arediscussed

in the following sections.

SECTION 2

2.20
2.3.5.1.1 Hydroplaning

Hydroplaning is an interesting subject since

most pilots have either heard of or experienced

instances of extremely poor braking action on

wetrunways during landing.The phenomenon

is highly sensitive to speed which makes it an

especially important consideration for RTO

situations.	

As a tire rolls on a wet runway, its forward

motion tends to displace water from the tread

contact area. While this isn’t any problem at

low speeds, at high speeds this displacement

action can generate water pressures sufficient 

to lift and separate part of the tire contact area

fromthe runway surface.The resulting tire-toground friction can be very low at high speeds

but fortunately improves as speed decreases.

Dynamic hydroplaning is the term used to

describe the reduction of tire tread contact

area due to induced water pressure. At high

speeds on runways with significant water, 

the forward motion of the wheel generates a

wedge of high pressure water at the leading

edge of the contact area, as shown in Figure

16A. Depending on the speed, depth of water,

and certain tire parameters, the portion of the

tire tread that can maintain contact with the

runway varies significantly. As the tread contact 

area is reduced, the available braking friction

is also reduced. This is the predominant factor

leading to reduced friction on runways that

have either slush, standing water or significant 

water depth due to heavy rain activity. In the

extreme case, total dynamic hydroplaning can

occur where the tire to runway contact area

vanishes, the tire lifts off the runway and rides

on the wedge of water like a water ski. Since

the conditions required to initiate and sustain

total dynamic hydroplaning are unusual, it

is rarely encountered. When it does occur,

such as during an extremely heavy rainstorm,

it virtually eliminates any tire braking or

cornering capability at high speeds.

Another form of hydroplaning can occur

where there is some tread contact with the

runway surface but the wheel is either locked

or rotating slowly (compared to the actual

airplane speed). The friction produced by

the skidding tire causes the tread material to

become extremely hot. As indicated in Figure

16B, the resulting heat generates steam in the

contact area which tends to provide additional

upward pressure on the tire. The hotsteamalso

starts reversing the vulcanizing process used

in manufacturing the rubber tread material.

The affected surface tread rubber becomes

irregular in appearance, somewhat gummy in

nature, and usually has a light gray color. This

“reverted” rubber hydroplaning resultsin very

low friction levels, approximately equal to icy

runway friction when the temperature is near

the melting point. An occurrence of reverted

rubber hydroplaning israre and usually results

from some kind of antiskid system or brake

malfunction which prevented the wheel from

rotating at the proper speed.

Figure 16A

Dynamic Hydroplaning

Figure 16B

Reverted Rubber Hydroplaning

&LOODEDRUNWAY ,OCKEDTIRE

3TREAMPRESSURE

SECTION 2

2.21
In the last several years, many runways

throughout the world have been grooved,

thereby greatly improving the potential wet

runway friction capability. As a result, the

numberofhydroplaningincidentshasdecreased

considerably.Flighttestsofonemanufacturer’s

airplane on a well maintained grooved

runway, which was thoroughly drenched with

water, showed that the stopping forces were

approximately 90% of the forces that could be

developed on a dry runway. Continued efforts

togroove additionalrunways ortheuseofother

equivalent treatments such as porous friction

overlays, will significantly enhance the overall 

safety of takeoff operations.	

The important thing to remember about wet

or contaminated runway conditions is that for

smooth runway surfacesthere is a pronounced

effect of forward ground speed on friction

capability, aggravated by the depth of water.

For properly maintained grooved or specially

treated surfaces, the friction capability is

markedly improved.	

2.3.5.1.2 The Final Stop

Areviewof overrun accidentsindicatesthat,in

many cases, the stopping capability available

was not used to the maximum during the

initial and mid portions of the stop maneuver,

because there appeared to be “plenty ofrunway

available”.In some cases, lessthan fullreverse

thrustwasusedandthebrakeswere releasedfor

a period of time, letting the airplane roll on the

portionofthe runwaythatwouldhaveproduced

good braking action.When the airplanemoved

onto the final portion of the runway, the crew 

discovered that the presence of moisture on the

top of rubber deposits in the touchdown and

turnoff areas resulted in very poor braking

capability, andthe airplane couldnotbe stopped

onthe runway.WhenanRTOisinitiatedonwet

or slippery runways, it is especially important

to use fullstopping capability untilthe airplane

is completely stopped.

2.3.5.2 Atmospheric Conditions

Ingeneral,the liftthewingsgenerate andthrust

the engines produce are directly related to the

airplane’sspeed through the air and the density

of that air. The flight crew should anticipate 

that the airplane’stakeoff performance will be

affected by wind speed and direction as well

asthe atmospheric conditionswhichdetermine

air density. Properly accounting forlastminute

changesinthesefactorsiscrucialtoasuccessful

Go/No Go decision.

The effect of the wind speed and direction on

takeoffdistance isverystraightforward.At any

givenairspeed, a10-knotheadwindcomponent

lowers the ground speed by 10 knots. Since

V1, rotation, and liftoff speeds are at lower

ground speeds, the required takeoff distance

is reduced. The opposite occurs if the wind

has a 10-knot tailwind component, producing

a 10-knot increase in the ground speed. The

requiredrunwaylengthisincreased, especially

the distance required to stop the airplane from

V1. Typical takeoff data supplied to the flight 

crew by their operations department will

either provide takeoffweight adjustmentsto be

applied to a zero wind limit weight or separate

columns of limit weights for specific values 

of wind component. In either case, it is the

responsibility of the flight crew to verify that 

lastminute changesinthe towerreportedwinds

are included in their takeoff planning.

The effectof airdensityontakeoffperformance

is also straight forward in so far as the crew

is normally provided the latest meteorological

information prior to takeoff. However, it is the

responsibility of the crew to verify the correct

pressure altitude and temperature values used

in determining the final takeoff limit weight 

and thrust setting.

SECTION 2

2.22
2.3.5.3 Airplane Configuration

The planned configuration of the airplane at the 

timeoftakeoffmustbe takenintoconsideration

by the flight crew during their takeoff planning. 

This should include the usual things like flap 

selection, and engine bleed configuration, as 

well as the unusual things like inoperative

equipmentcoveredbytheMinimumEquipment

List (MEL) or missing items as covered by

the Configuration Deviation List (CDL). This 

section will discuss the effect of the airplane’s

configuration on takeoff performance capability 

and/or the procedures the flight crew would use 

to complete or reject the takeoff.	

2.3.5.3.1 Flaps

The airplane’s takeoff field length performance 

is affected by flap setting in a fairly obvious way. 

For a given runway length and airplane weight,

the takeoff speeds are reduced by selecting a

greater flap setting. This is because the lift 

required for flight is produced at a lower V2

speed with the greater flap deflection. Since the 

airplanewillreachtheassociatedlowerV1 speed

earlier in the takeoff roll, there will be more

runwayremainingfor apossible stopmaneuver.

On the “Go” side of the decision, increasing

the takeoff flap deflection will increase the 

airplane drag and the resulting lower climb

performance may limit the allowable takeoff

weight. However, the takeoff analysis used by

the flight crew will advise them if climb or 

obstacle clearance is a limiting factor with a

greater flap setting. 

2.3.5.3.2 Engine Bleed Air

Wheneverbleedairis extractedfromanengine,

and the value of the thrust setting parameter

is appropriately reduced, the amount of thrust

the engine generatesisreduced. Therefore, the

use of engine bleed air for air conditioning/

pressurization reduces the airplane’s potential

takeoff performance for a given set of runway

length, temperature and altitude conditions.

When required, using engine and/or wing

anti-ice further decreases the performance

on some airplane models. This “lost” thrust

may be recoverable via increased takeoff

EPR or N1 limits as indicated in the airplane

operating manual. It depends on engine type,

airplane model, and the specific atmospheric 

conditions.

2.3.5.3.3 Missing or Inoperative Equipment 

Inoperative or missing equipment can

sometimes affect the airplane’s acceleration

or deceleration capability. Items which

are allowed to be missing per the certified 

Configuration Deviation List (CDL), such 

as access panels and aerodynamic seals, can

cause airplane drag to increase. The resulting

decrements to the takeoff limit weights are,

when appropriate, published in the CDL.

With these decrements applied, the airplane’s

takeoffperformancewillbewithinthe required

distances and climb rates.

Inoperative equipment or deactivated systems,

as permitted under the Minimum Equipment

List (MEL) can also affect the airplane’s

dispatched “Go” or “Stop” performance.

For instance, on some airplane models, an

inoperative in-flight wheel braking system may 

require the landing gear to be left extended

during a large portion of the climbout to

allow the wheels to stop rotating. The ‘Go”

performance calculationsfor dispatch must be

made in accordance with certified “Landing 

Gear Down” FlightManual data.The resulting

SECTION 2

2.23
new limit takeoff weight may be much less

than the original limit in orderto meet obstacle

clearance requirements, and there would be

some excess runway available for a rejected

takeoff.	

An MEL item that would not affect the “Go”

performance margins but would definitely 

degrade the “Stop” margins is an inoperative

anti-skidsystem.Inthisinstance,notonlyisthe

limitweightreducedbythe amountdetermined

from the AFM data, but the flight crew may also 

be required to use a different rejected takeoff

procedure in which throttles are retarded first, 

the speedbrakes deployed second, and then

the brakes are applied in a judicious manner 

avoid locking the wheels and failing the tires.3

The associated decrement in the Field Length

Limit Weight is usually substantial.

Other MEL items such as a deactivated brake

may impact both the continued takeoff and

RTO performance through degraded braking

capability and loss of in-flight braking of the 

spinning tire.

The flight crew should bear in mind that 

the performance of the airplane with these

types of CDL or MEL items in the airplane’s

maintenance log at dispatch will be within the

certified limits. However, it would be prudent 

for the flight crew to accept final responsibility 

to assure that the items are accounted for in

the dispatch process, and to insure that they,

as a crew, are prepared to properly execute any

revised procedures.

3

UK CAA procedure adds “...apply maximum reverse thrust.”

SECTION 2

2.24
2.3.5.3.4 Wheels, Tires, and Brakes

The airplane’s wheels, tires, and brakes are

another area that should be considered in light

of the significant part they play in determining 

the results of a Go/No Go decision.	

One design feature which involves all three

components is the wheel fuse plug. All jet

transport wheels used for braking incorporate

thermalfuseplugs.Thefunctionofthefuseplug

istopreventtireorwheelburstsbymeltingifthe

heat transferred to the wheels from the brakes

becomes excessive. Melting temperatures of

fuse plugs are selected so that with excessive

brake heat, the inflation gas (usually nitrogen) 

is released before the structural integrity of

the tire or wheel is seriously impaired. Both

certification limitations and operational

recommendations to avoid melting fuse plugs

are provided to operators by the manufacturer,

as is discussed in Section 2.3.5.3.6 under the

heading, Residual Brake Energy.

While fuse plugs provide protection from

excessive brake heat, it is also important to

recognize thatfuseplugs cannotprotect against

all types of heat induced tire failures. The

location ofthe fuse plug in thewheel isselected

to ensure proper response to brake heat. This

location in combination with the inherent low

thermal conductivity of tire rubber means that

the fuse plugs cannot prevent tire failuresfrom

the rapid internal heat buildup associated with

taxiing on an underinflated tire. This type of heat 

buildup can cause a breakdown of the rubber

compound,plyseparation, and/orruptureofthe

plies. This damage might not cause immediate

tire failure and because it is internal, it may

not be obvious by visual inspection. However,

the weakened tire is more prone to failure on a

subsequent flight. Long taxi distances especially 

at high speeds and heavy takeoff weights can

aggravate this problem and result in a blown

tire. While underinflation is a maintenance 

issue, flight crews can at least minimize the 

possibility of tire failures due to overheating

by using low taxi speeds and minimizing taxi

braking whenever possible.

SECTION 2

2.25
Correct tire inflation and fuse plug protection 

are significant, but will never prevent all tire 

failures. Foreign objects in parking areas,

taxiways and runways can cause severe cutsin

tires. The abrasion associated with sustained

lockedorskiddingwheels,whichcanbe caused

byvariousantiskidorbrakeproblems,cangrind

through the tire cords until the tire is severely

weakened or a blow out occurs. Occasionally,

wheel cracks develop which deflate a tire and 

generateanoverloadedconditionintheadjacent

tireonthesameaxle.Someoftheseproblemsare

inevitable. However, it cannot be overstressed

that proper maintenance and thorough walk

aroundinspections arekeyfactorsinpreventing

tire failures during the takeoff roll.	

Tire failures may be difficult to identify from the 

flight deck and the related Go/No Go decision 

is therefore not a simple task. A tire burst may

be loud enough to be confused with an engine

compressor stall, may just be a loud noise, or

may not be heard. A tire failure may not be

felt at all, may cause the airplane to pull to one

side, or can cause the entire airplane to shake

and shudderto the extent that instruments may

become difficult to read. Vibration arising out of 

failure of a nosewheel tire potentially presents

another complication. During takeoffrotation,

vibration may actually increase at nosewheel

liftoff due to the loss of the dampening effect

of having the wheel in contact with the runway.

A pilot must be cautious not to inappropriately

conclude, under such circumstances, that

another problem exists.	

Although continuing a takeoff with a failed

tire will generally have no significant adverse 

results, there may be additional complications

as a result of a tire failure. Failed tires do not

inthemselvesusuallycreatedirectional control

problems. Degradation of control can occur,

however, as a result of heavy pieces of tire

material being thrown at very high velocities

and causing damage to the exposed structure

of the airplane and/or the loss of hydraulic

systems. On airplanes with aft mounted

engines, the possibility of pieces of the failed

tire being thrown into an engine must also be

considered.

An airplane’s climb gradient and obstacle

clearance performance with all engines

operating and the landing gear down exceeds

the minimum certified engine-out levels that 

are used to determine the takeoff performance

limits. Therefore, leaving the gear down after

a suspected tire failure will not jeopardize the

aircraftif all engines areoperating.However,if

the perceived tire failure is accompanied by an

indicationofthrustloss,orif anengineproblem

should develop later in the takeoff sequence,

the airplane’s climb gradient and/or obstacle

clearance capability may be significantly

reduced ifthe landing gearis notretracted.The

decision to retract the gear with a suspected

tire problem should be in accordance with the

airline’s /manufacturer’s recommendations.

If a tire failure issuspected atfairly lowspeeds,

it should be treated the same as any other

rejectable failure and the takeoff should be

rejected promptly. When rejecting the takeoff

with a blown tire, the crew should anticipate

that additional tires may fail during the stop

attempt and that directional control may be

difficult. They should also be prepared for the 

possible loss of hydraulic systems which may

cause speedbrake or thrust reverser problems.

Sincethestoppingcapabilityoftheairplanemay

be significantly compromised, the crew should 

notrelax fromamaximumeffortRTO until the

airplane is stopped on the pavement.

Rejecting a takeoff from high speeds with

a failed tire is a much riskier proposition,

especially if the weight is near the Field Limit

Weight.Thechancesofanoverrunareincreased

simply due to the loss of braking force from

one wheel.If additional tiresshould fail during

the stop attempt, the available braking force is

evenfurtherreduced.Inthis case,itisgenerally

better to continue the takeoff, as can be seen

in Figure 17. The subsequent landing may take

advantage of a lower weight and speed if it is

possible to dump fuel. Also, the crew will be

SECTION 2

2.26
better prepared for possible vibration and/or

control problems. Most important, however, is

the fact that the entire runway will be available

for the stop maneuver instead of perhaps, as

little as 40% of it.

As can be seen from this discussion, it is

not a straightforward issue to define when a 

takeoff should be continued or rejected after

a suspected tire failure. It is fairly obvious

however, that an RTO initiated at high speed

with a suspected tire failure is not a preferred

situation. McDonnell Douglas Corporation,

in an All Operator Letter4

, has addressed this

dilemma by recommending a policy of not

rejecting a takeoff for a suspected tire failure

at speeds above V1−20 knots. The operators 

of other model aircraft should contact the

manufacturer for specific recommendations 

regarding tire failures.

2.3.5.3.5 Worn Brakes

The investigation of one recent RTO incident

which was initiated “very near V1”, revealed

that the overrun was the result of 8 of the 10

wheel brakes failing during the RTO. The

failed brakes were later identified to have been 

at advanced states of wear which, while within

accepted limits, did not have the capacity for a

high energy RTO.	 	

This was the first and only known accident in 

thehistoryofcommercialjettransportoperation

that canbe traced tofailure ofthebrakes during

anattemptedRTO.TheNationalTransportation

SafetyBoard (NTSB)investigated the accident

andmadeseveralrecommendationstotheFAA.

The recommendations included the need to

require airplane and brake manufacturers to

verify by test and analysis that their brakes,

when worn to the recommended limits, meet

the certification requirements. Prior to 1991, 

maximumbrake energylimitshadbeenderived

from tests done with new brakes installed.

Virtually all brakes in use today have wear

indicator pins to show the degree of wear and

when the brake must be removed from the

!VAILABLE2UNWAY

• 3AMEINITIALCONDITIONS

s4AKEOFFFLAPS

s#ERTIFIEDPERFORMANCE

s$RYRUNWAY

s&IELDLENGTHLIMITWEIGHT

s,ANDINGFLAPS

s#ERTIFIEDPERFORMANCE

 LESSBLOWNTIREEFFECTS

s4AKEOFFWEIGHTMINUS

 BURNOFFANDFUELDUMPOPT	 FT

3TOP

ZONE

2EJECT

'O

6

4RANSITION

COMPLETE

4RANSITION

COMPLETE

62

6%&

62

6

FT

2EJECT

'O

TO

KTS

TOFT

OVERRUN

%NGINE

FAIL

4IRE

FAIL

TO -ARGIN

TO

!PPROX

FT

2EDUCEDBRAKING

CAPABILITYPLUSALL

ENGINEREVERSE

&ULLSTOPPING

NOREVERSE

Figure 17

Margins associated 

with continuing or 

rejecting a takeoff 

with a tire failure

4

McDonnell Douglas All Operators Letter FO-AOL-8-003, -9-006, -10-004, -11-015, Reiteration of Procedures and Techniques 

Regarding Wheels, Tires, and Brakes, dated 19 AUG 1991

SECTION 2

2.27
airplane. In most cases, asthe brake wears, the

pin moves closer to a reference point, so that

when the end of the pin is flush with the reference 

(with full pressure applied), the brake is “worn

out”.As oflate 1991, tests have been completed

which show that brakes at the allowable wear

limit can meet AFM brake energy levels. As

a result, “wear pin length” is not significant 

to the flight crew unless the pin indicates that 

the brake is worn out and should be removed

from service. There are no changes to flight 

crew or dispatch procedures based on bra

wear pin length.

2.3.5.3.6 Residual Brake Energy

After a brake application, the energy which the

brake has absorbed isreleased as heat and until

this heat is dissipated, the amount of additional

energy which the brake can absorb without

failure isreduced. Therefore, takeoff planning

must consider the effects of residual brake

energy (or brake temperature) if the previous

landing involved significant braking and/or the 

airplane turnaround is relatively short. There

are two primary sources of information on

thissubject.The brake temperature limitations

and/or cooling chartsin the airplane operating

manual provide recommended information on

temperature limitations and/or cooling times

and the procedures necessary to dissipate

various amounts of brake energy. In additio

the Maximum Quick Turnaround Weight

(MQTW) chart in the AFM is a regulatory

requirement that must be followed. This chart

shows the gross weight at landing where the

energy absorbed by the brakes during the

landing could be high enough to cause the

wheel fuse plugs to melt and establishes a

minimumwaiting/coolingtime forthese cases.

The MQTW chart assumes that the previous

landingwas conductedwithmaximumbraking

forthe entire stopanddidnotuse reverse thrust,

so for many landings where only light braking

wasusedthere issubstantial conservatismbuilt

into the wait requirement.

2.3.5.3.7 Speedbrake Effect on Wheel 

Braking

While jet transport pilots generally understand

the aerodynamic drag benefit of speedbrakes 

and the capability of wheel brakes to stop an

airplane, the effect of speedbrakes on wheel

brake effectivenessduringanRTOisnot always

appreciated. The reason speedbrakes are so

critical is their pronounced effect on wing lift.

Depending on flap setting, the net wing lift 

can be reduced, eliminated or reversed to a

down load by raising the speedbrakes, thereby

increasing the vertical load on the wheels

which in turn can greatly increase braking

capability.

Speedbrakes are important since for most

braking situations, especially any operation

on slippery runways, the torque output of the

brake, and therefore the amount of wheelbrake

retarding force that can be developed is highly

dependent on the vertical wheel load. As a

result, speedbrakes must be deployed early in

the stop to maximize the braking capability.

During RTO certification flight tests, the 

stopping performance is obtained with prompt

deploymentofthespeedbrakes.Failure to raise 

the speedbrakes during an RTO or raising 

them late will significantly increase the 

stopping distance beyond the value shown 

in the AFM.

Figures 18 and 19 summarize the effect of

speedbrakes during an RTO. For a typical

mid-sized two-engine transport, at a takeoff

weight of 225,000 lb, the total load on the main

wheels atbrake releasewouldbe approximately

193,000lb.Asthe airplane accelerates alongthe

runway, wing lift will decrease the load on the

gear, and by the time the airplane approaches

V1 speed,(137 knotsforthis example),themain

gear load will have decreased by nearly 63,000

lb. The data in Figure 19 graphically depicts

how the forces acting on the airplane vary with

airspeed from a few knots before the RTO is

initiateduntilthe airplane isstopped.Whenthe

pilotbeginstheRTObyapplyingthebrakes and

SECTION 2

2.28
4OTALSTOPPINGFORCECAPABILITY



INCREASE

$RAG

"RAKES

$RAG

,OADON

WHEELS

,IFT

"RAKES

&ORWARDMOTION

2OLLING

"RAKE

TORQUE "RAKINGFORCE

"RAKINGFORCEBRAKINGFRICTIONXLOADONTIRE	



"RAKETORQUENOTLIMITING

3PEED


BRAKES

DOWN

3PEED


BRAKES

UP

3PEEDBRAKEPOSITION

$OWN 5P

$IFFERENCE

SPEEDBRAKEUP

$RAG

,IFT

.ETLOADONWHEELS

-AXBRAKINGFORCE

-AXSTOPPINGFORCE

BRAKESANDDRAG	

LBS

LBS







LBS





















7EIGHT

ONTIRE Figure 18

Effect of 

speedbrakes on the 

stopping capability 

of a typical midsize two-engine 

transport

Figure 19

Summary of forces 

during a typical 

mid-size twoengine airplane 

RTO
























    

3PEED+4!3

2ETARDING

FORCELB

  

"RAKINGFORCEWITHSPEEDBRAKESUP

"RAKINGFORCEWITHSPEEDBRAKESDOWN

4WO
ENGINEREVERSETHRUSTFORCE

!ERODRAGWITHSPEEDBRAKESUP

!ERODRAGWITHSPEEDBRAKESDOWN

SECTION 2

2.29
closing the thrustlevers,the braking force rises

quickly to a value in excess of 70,000 lb. The

nearly vertical line made by the braking force

curve in Figure 19 also showsthat the airplane

began to decelerate almost immediately, with

virtually no further increase in speed.	

The next action in a typical RTO procedure

is to deploy the speedbrakes. By the time this

action is completed, and the wheel brakes

have become fully effective, the airplane will

have slowed several knots. In this example of

an RTO initiated at 137 knots, the airspeed

would be about 124 knots at this point. The

weight on the main gear at 124 knots would be

approximately 141,600 lbwith the speedbrakes

down, and would increase by 53,200 lb when

the speedbrakes are raised. The high speed

brakingcapability issubstantially improvedby

this38%increase inwheelloadfrom141,600to

194,800 pounds, which can be seen by noting

the increase in braking force to 98,000 pounds.

In addition, the speedbrakes have an effect

on aerodynamic drag, increasing it by 73%,

from 8,500 to 14,700 pounds. The combined

result, as indicated by the table in Figure 18,

is that during the critical, high speed portion

of the RTO, the total stopping force acting on

the airplane is increased by 34% when the

speedbrakes are deployed.

Since both the force the brakes can produce

and the aerodynamic effect of the speedbrakes

vary with speed, the total effect for the RTO

stop is more properly indicated by averaging

the effect of the speedbrakes over the entire

stoppingdistance.Forthis example,theover all

effect of raising the speedbrakesis an increase

of14%inthe average totalstoppingforce acting

throughout the RTO.

One common misconception among pilots

is that the quick use of thrust reversers will

offset any delay or even the complete lack of

speedbrake deployment during an RTO. This

is simply not true. On a dry runway, delaying

the deployment of the speedbrakes by only

5 seconds during the RTO will add over 300

ft. to the stop distance of a typical mid-sized

two-engine jet transport, including the effects

of engine-out reverse thrust. As a worst case

illustration, if reverse thrust was not used

and the speedbrakes were not deployed at all,

stopping distance would be increased by more

than 700 ft. Although the exact figures of this 

example will vary with different flap settings 

and from one airplane model to another, the

general effect will be the same, namely that

speedbrakes have a very pronounced effect on

stopping performance.

2.3.5.3.8 Carbon and Steel Brake Differences

Recent emphasis on the apparent tendency for

carbon brakes to wear out in proportion to the

total number of brake applications, as opposed

to steel brakes which wear out in proportion to

energy absorbed by the brakes, has generated

interest in other operational differences

between the two types of brakes. While the

emphasis on wear difference is necessary,

since the economics of brakemaintenance isso

significant, for most other operational aspects 

the two brakes can be considered equivalent.

Asfar asRTOcapability is concerned, the type

of brake involved does not matter since each

brake installation is certified to its particular 

takeoff energy capability. This means that

either carbon or steel brakes, even fully worn,

will be able to perform the maximum certified 

RTOcondition applicable to that installation in

a satisfactory manner.

Onedifferencebetweensteel andcarbonbrakes

that is often claimed is an increased tolerance

to thermal overload. To understand this in

properperspective,recognize that althoughthe

friction elements in a carbon brake (rotating

and stationary disks) are made of carbon

material, which has good strength and friction

characteristics at high temperatures, the brake

structure, brake hydraulics, the wheel, and

the tire are essentially the same as used for an

equivalent steel brake. Within the limitations

SECTION 2

2.30
representedbythisnon-carbonequipmentthen,

an overheated carbon brake will continue to

function reasonably well in situations where

an equivalent steel brake with its metallic

disks might not. An overload condition could

be caused by excessive taxi braking, riding the

brakes,orinappropriate turnaroundprocedures

after landing. In this type of situation, carbon

brakeswillgenerallydemonstratebetterfriction

characteristics and therefore develop more

torque and stopping force than equivalentsteel

brakes.	

The difficulty with this carbon brake thermal 

advantage isthatitis nearlyimpossible to judge

the extra amount of braking that could be done

before affecting the ability of the non-carbon

componentstoperforminanRTOsituation.This

is because the thermal effects on the limiting

hardware are so highly time and ambient

condition dependent. For instance, whether an

airplane has carbon brakes or steel brakes will

not matter if enough time has elapsed after a

heavybrake applicationsuchthatthewheelfuse

plugs release before the airplane can complete

the next takeoff or a subsequent RTO attempt.

Pilots should concentrate on proper braking

proceduresrather than attempt to capitalize on

any extra carbon brake advantage. Attention

to the brake cooling chart recommendations

will avoid these thermal problems and ensure

that the airplane stopping performance can be

achieved regardless of whether steel or carbon

brakes are installed.

The increased thermal overload capability of

carbon brakesis closely related to the idea that

carbonbrakesdonot“fade”.Inotherwords,they

always produce the same torque throughoutthe

stop even as the brake temperature increases.

Although many carbon brakes do develop

nearly constanttorque,some fade considerably

in certain conditions. On the other hand, some

steel brakes do not fade very much at all,

depending to a large extent on the degree of

conservatismbuiltintothebrake.Ineither case,

brake fade is taken into account in the AFM

performance, for the specific brake installed on 

each particular airplane. Therefore, brake fade

does not need to be an operational concern to

the flight crew. 

Asecondfactorwithsteelbrakesisthepotential

loss of structural strength of the rotors and

stators at the extreme operating temperatures

associated with limiting energy values. This

could cause a structural failure of one or more

brake stators near the end of the stop. In this

case the brake will continue to function but

with reduced torque capability. The remaining

components, which are common to carbon and

steel brakes, are less likely to be affected.

An RTO from at or near the brake energy

limits can also mean that after stopping on

the runway, the brakes may not be capable of

stopping the airplane again, even fromlowtaxi

speeds. This is especially true for steel brakes

due tothe increasedchanceofstructuralfailure.

Therefore,itisimportantthatthe crewconsider

the probable condition of the airplane wheels,

brakes, and tires after completing a high speed

RTO before attempting to move the airplane

from the runway.

One other difference between carbon and steel

brakesthatmight be evidentin certain RTOs

brakewelding.Steelbrakes,whichusuallyhave

rotors of steel and stators of a copper-iron mix

(with a number ofspecial ingredients) canweld

together,preventingfurtherwheelrotation.This

can even happen before the airplane comesto a

full stop, particularly in the last several knots

where the antiskid system is not effective.

2.3.5.3.9 High Brake Energy RTOs

Brake rotor and statortemperatures associated

with RTOs which involve brake energies

at or near certified maximum values, reach 

approximately 2000 °F for steel brakes, and

2500 °F for most carbon brakes. These high

temperatures may, in some situations, ignite

certain items in the wheel, tire, and brake

assembly. While considerable design effort is

SECTION 2

2.31
made to preclude fires whenever possible, the 

regulations recognize the rarity of such high

energy situations and allow brake fires after a 

maximum energy condition, provided that any

fires that may occur are confined to the wheels, 

tires andbrakes, anddonotresultinprogressive

engulfment of the remaining airplane during

the time of passenger and crew evacuation.It is

important then, for flight crews to understand 

the nature of possible fires and the airplane 

takeoff parameters that could involve these

very high brake energies.	

There are two primary combustibles in the

assembly, namely the tire, and brake grease.

Brake hydraulic fluid will also burn if there 

is a hydraulic leak directed at a very hot

brake disk. Tire fires can occur if the rubber 

compoundtemperature exceeds approximately

650 °F. Tire fires usually burn fairly slowly 

for the first several minutes when started by 

brake heat. Grease fires are even less active, 

typically involving a small, unsteady, flickering 

flame, sometimes with considerable smoke. 

The probability of a crew experiencing a brake

fire at the conclusion of an RTO is very low, 

considering brake design factors, the dispatch

parameters, and service history.

In terms of practical guidelines for flight 

crews, takeoffs at or near VMBE are normally

encountered at high altitude airports or at

very hot temperatures. An RTO from close to

V1 speed under these conditions will require

the brakes to absorb a significant amount of 

energyduring the stop.Flight crews canuse the

Brake Cooling Chart of the airplane operating

manual to determine brake energy values if

the situation warrants such a review. In cases

where an extremely high brake energy might

be encountered, the possibility of a brake fire 

should therefore be considered by the flight 

crew during the pre-takeoff briefing. If a high 

speed RTO is subsequently performed, the

tower should immediately be advised that the

airplane isstill on the runway, that a high brake

energy stop was made, and that emergency

equipment isrequested to observe the tires and

brakes for possible fires.

2.3.5.4 Reverse Thrust Effects

Most ofthe takeoffs planned in theworld do not

include reverse thrust credit. This is because

the rejected takeoff certification testing under 

FAA rules does not include the use of reverse

thrust, except for the wet runway case for

airplanes certified under FAR Amendment 25-

92. An additionalstopping margin is produced

by using maximum reverse thrust. We stress

the word “maximum” in relation to the use of

reverse thrust because of another commonly

held misconception. Some pilots are of the

opinion that idle reverse is “equally or even

more” effective than full or maximum reverse

thrust for today’s high bypass ratio engines.

This is simply not true. The more EPR or N1

that is applied in reverse, the more stopping

force the reverse thrust generates. The data

Figure 20

Effect of engine 

RPM and airspeed 

on reverse thrust 

of a typical high 

bypass engine





















     



+NOTS4!3







 

.ETREVERSE

THRUSTFORA

TYPICALLB

THRUSTENGINE

LBPERENGINE

0ERCENT.

SECTION 2

2.32
shown inFigure 20 istypicalfor allhighbypass

engines.	

On wet or slippery runways, the wheel brakes

arenot capableofgeneratingashigha retarding

force astheyareonadrysurface.Therefore,the

retardingforceofthereversersgeneratesalarger

percentage of the total airplane deceleration.

2.3.5.5 Runway Parameters

Runway characteristics which affect takeoff

performance include length, slope, clearway

and/or stopway. The effect of runway length

is straightforward, however, slope, clearway,

and stopway deserve some discussion.

A single value of runway slope is typically

chosen by the operator to perform takeoff

analysis calculations. This single value is

usually taken from information published by

the navigation chart services or the airport

authorities.Oncloserinspectionhowever,many

runways are seen to have distinct differences

in slope along the length of the runway.

The single published value may have been

determined by a variety of methods, ranging

from a simple mathematical average of the

threshold elevations,to someweighted average

methods proposed by ICA0 in an advisory

publication5.

As a simple example, consider a runway

which has only one slope discontinuity. The

first two thirds of the runway has an uphill 

slope of +2% and the last third has a downhill

slope of −2%. The equivalent single slope for 

this runway, as determined from the ICAO

Circular methods, could vary from +1.3% to

−0.3%. When the takeoff analysis is made 

for this runway, the limit weights will be the

same as would be determined for an actual

single slope runway. However, as the airplane

commencesatakeoffonthe2%upsloperunway,

it will accelerate more slowly than it would on

any of the equivalent single slope runways,

which will result in its achieving V1 speed

further along the runway than was planned.

If no event occurs which would precipitate an

RTO, the final acceleration to VR and liftoff

will be higher than planned and the overall

performance will probably come out close to

what was scheduled.

Ontheotherhand,if aneventworthyof anRTO

should occur just prior to the airplane reaching

V1, most, if not all of the stop maneuver will

have to be carried out on a 2% downhill slope

surface instead of the equivalent single slope

value, and the RTO will have been initiated

with lessrunway remaining than was assumed

in determining the limitweightforthattakeoff.

There is little the crew can do in this type of

situation, other than in the vein of situational

awareness, emphasize in their briefing that 

an RTO near V1 for anything other than a

catastrophic event is not advisable.

A clearway is an area at least 500 ft wide

centered about the extended centerline of

the runway with a slope equal to or less than

1.25%. This area is called the clearway plane.

No obstructions, except threshold lights,

can protrude above this clearway plane. The

acceleration toV2 and 35 feet is completed over

the clearway. The use of clearway to increase

takeoff weight “unbalances the runway” and

results in a lower V1 speed. The maximum

clearwayusedtocalculate takeoffperformance

is restricted by the regulations to one half the

demonstrated distance from liftoff to 35 ft.

A stopway is an area at least as wide as the

runway and centered about the extended

centerline. It must be capable of supporting

the weight of the airplane without causing

damage. Use of stopway also “unbalances the

runway” resulting in a higher takeoff weight

andincreasedV1 speed.AnRTOinitiatedatthis

V1 will come to a stop on the stopway. For the

sake of completeness, it should be pointed out

that not allstopways will qualify as clearways,

nor will a clearway necessarily qualify as a

stopway. The specified criteria for each must 

be met independently before it can be used for

5

ICAO Circular 91-AN/75, The Effect of Variable Runway Slopes on Take-Off Runway Lengths for Transport Aeroplanes,

dated 1968.

SECTION 2

2.33
takeoff performance calculations.

The use of clearway and/or stopway does not

necessarilyofferanyadditionalmarginforRTO

stopping.Inbothcases,thetakeoff performan

is “unbalanced” by adjusting V1 speed to plan

that the stop will be completed by the end of

the paved surface.

2.3.5.6 (Not Used)

2.3.5.7 Takeoffs Using Reduced Thrust

There are twomethodsofperforminga reduced

thrust takeoff. The first is to use a fixed derate of 

the engine toa lowerthrust rating.For exampl

a JT9D-7F engine operated at a JT9D-7 rating,

or a CFM56-3C-1 engine operated at 20,000 lb

of thrust (-B1 rating) instead of the full 23,500

lb rating. When a fixed derate is used, the engine 

EGT and RPM limits are reduced and the crew

are not to exceed the reduced limits in normal

operation. As a result of the lower limit thrust

with a fixed derate, the minimum control speeds 

Vmcg and Vmca are also reduced. Since the

choiceofderatethrustlevelsisusuallyrestricted

to one or two preselected values, it is rare that

the takeoff performance at the derated thrust

would be reduced to field length limit levels.

The second way of reducing takeoff thrust is

to use the Assumed Temperature Method. The

fundamental difference between fixed derates 

and the Assumed Temperature Method is that

theoperatinglimitsoftheenginearenotreduced

when using Assumed Temperature Method

reduced thrust. The flight crew may increase 

the thrust to the full engine rating at any time

during the takeoff if it is deemed appropriate.

For instance, British CAA Flight Manuals

include a recommendation to increase thrust

on the operating engines to the full rating in

the eventthat anengine failsduringthe takeoff.

As a result, the Vmcg and Vmca speeds are not

reducedbelowthe fullratingvalueswhenusi

the Assumed Temperature Method.

Fixed derates and the Assumed Temperature

Method also differin terms ofthe performance

margins that are inherent to their use. As was

previouslymentioned,atlimitweights,atakeoff

performed using a fixed derate takeoff thrust 

will conform to the minimum performance

levels of the regulations, just as a limit weight

takeoff would when using full rated takeoff

thrust. The associated V1 speed provides the

standard certification “margins” of a 35 foot 

screen height or a stop at the end of the runway

in the event of an engine failure.

WhenusingtheAssumedTemperatureMethod,

additional “margins” are created in both the

“Go” and “Stop” cases. As the name implies,

the techniqueusedtocalculate theperformance

with the Assumed Temperature Method is to

assume that the temperature is higher than it

actually is, and to calculate takeoff thrust and

speeds at the higher temperature.

TheprimaryreasonthattheuseoftheAssumed

Temperature Method results in performance

margins is that the true airspeed of the

airplane is lower than would be the case if the

actual temperature were equal to the assumed

temperature.

2.3.5.8 The Takeoff Data the Pilot Sees

The typical takeoff data table (sometimes

referred to as runway analysis or gross weight

tables) shows the limit takeoff weight for

a specific runway over a range of ambient 

temperatures.Theremayalsobe correctionsfor

wind, pressure altitude, bleed configurations, 

and runway surface conditions. Each table

usually shows the limit weights for only one

flap setting. Some airlines show the takeoff 

speeds and the takeoffthrust EPRor N1 setting

along with the limit weights. The tables can	

display limit weights for Field Length, Climb,

Obstacle Clearance, Tire Speed and Brake

Energy, andtellwhichfactorislimitingfor each

wind and temperature. This tabular display of

the takeoff data has become the standard tool

SECTION 2

2.34
for using the assumed temperature method to

reduce the takeoff power setting and thereby

improve engine life.	

Thistakeoff data issome ofthemost important

data used on any flight. It is essential that 

flight crews know their actual takeoff weight 

and that they use the proper takeoff speeds.

It is equally important that the flight crew be 

aware of their proximity to the limit weights

for that takeoff’s ambient conditions. These

limit weights and speeds are more than just

numbers. They represent the maximum certified 

takeoffperformanceoftheairplane.Iftheactual

takeoff weight is equal to or near the runway

limit weight, the crew should note that fact

and be extra alert that a reject from near or at

V1 will require prompt application of the full

stopping capability of the airplane to assure

stopping on the runway.

If the actual airplane weight is less than the

limitweight,the crewshould treatthe normally

obtained V1 speed as a “limit speed” unless

their operations department has provided them

with a specific method of unbalancing the V1

speed to utilize the excess runway available.

The operator should assure that a suitable,

non-ambiguous method of presenting the V1

speed is chosen, whether it is a balanced or

unbalanced speed.

2.3.6 Increasing the RTO Safety Margins

There are a number of choices and techniques

thecrewcanmakeandpracticethatwillincrease

the RTO margins for takeoff. Some involve

airline policy and require the publication of

additional data (such as multiple flap setting 

takeoff weight and speed data) and some are

just good personal technique.

2.3.6.1 Runway Surface Condition

The crew cannot control the weather like

they can the airplane’s configuration or

thrust. Therefore, to maximize both the

“Go” and “Stop” margins, they must rely on

judiciously applying their company’s wet or

contaminated runway policies as well as their

own understanding of how the performance of

their airplane may be affected by a particular

runway surface condition.

2.3.6.2 Flap Selection

Often the RTO safety margin can be increased

by selection of an alternative takeoff flap setting. 

Consider for example, the effect of takeoff flap 

selection on the performance limit weights of

a typical large two engine airplane, as shown

in Figure 21.

8,700 ft runway

Sea Level

37° C

Flap setting

1 5 15 20

Runway limit weight, 

lb (kg)

358,300

(162,494)

374,200

(169,705)

389,000

(176,417)

393,600

(178,503)

Climb/Obstacle limit 

weight, lb (kg)

414,100

(187,800)

407,300

(184,717)

393,600

(178,503)

383,000

(173,696)

Figure 21

Typical large 

two-engine jet 

transport takeoff 

performance

SECTION 2

2.35
If a flight requires the absolute maximum 

takeoff weight, the above weight limits would

dictate choosing Flaps 15 since 389,000 lb is

the highest weight allowed. Flaps 20 is Climb/

Obstacle limited to a lower weight and Flaps

1 and 5 are Runway limited to lower weights.

If the actual takeoff weight desired is equal

to the maximum limit weight, there is no flap 

selection option. The takeoff will need to use

Flaps 15.	

More typically, however, the airplane’s actual

takeoff weight is well below the maximum.

There are then two viable ways to improve

RTO stopping distance margin: either by flap 

selection or by reduced V1 techniques.	

If the flight’s actual takeoff weight was 374,200 

pounds, investigating the above table indicates

Flaps 5, Flaps 15, or Flaps 20 are all acceptable.

Flaps 5 is runway limited so it offers no

additionalRTOmargin.However,Flaps 15 and

Flaps20bothofferanopportunityforadditional

stopping distance margin. These additional

stopping margins have been calculated for this

example and are shown in Figure 22.

Thus, if there are no other constraints such as

obstaclesor criticalnoise abatementprocedures

that would prevent the selection of a greater flap 

setting, the crew could give themselves 1000

feet of extra stopping distance in case an RTO

was required on this takeoff.

Remember that there are some disadvantages

to selecting a higher flap setting. These

disadvantages include diminished climb

performance and slightly more fuel consumed

due to the higher drag configuration and the 

additional flap retraction cleanup time that will 

be required.

2.3.6.3 Runway Lineup

Positioning the aircraft on the runway in

preparation fortakeoffis an important element

inmaximizingtheamountofpavementavailable

for a possibleRTOmaneuver.Correction to the

available runway length can be made to the

takeoff analysis on those runways where it

is not possible to position the airplane at the

beginning of the published distance.

Correctrunwaylineuptechnique shouldalways

be practiced regardless of whether or not there

is excessrunwayavailable.Evenif anallowance

has been made, it is up to the crew operating

the flight to align the airplane on the runway 

using the shortest possible distance. If they

can do it in a shorter distance than taken into

account by their company, then there is that

much extra margin for the takeoff.

2.3.6.4 Setting Takeoff Thrust

At takeoff thrust settings, gas turbine (jet)

engines operate at very high RPM. It typically

takesseveralsecondsforthe enginestospoolup

from a low idle or taxi thrust to takeoff power

after the thrust levers are advanced. During

this time, the aircraft is not accelerating at

full potential because the engines are not yet

developing full power.

The demonstrated takeoff distance is achieved

when the takeoff thrust isset prior to releasing

the brakes, but this technique is often not

practical in line operations due to expedited

Flap setting 5 15 20

Stopping margin Zero 850 ft 1,000 ft

Figure 22

Effect of flap 

selection on RTO 

stopping margins

SECTION 2

2.36
takeoff clearances, engine FOD hazards, and

passengercomfort.Asaresult,mosttakeoffsare

performed as “rolling takeoffs”,with the thrust

being set asthe airplane beginsthe takeoffroll.

However,thistechniquemust be accomplished

promptly to avoid compromising the takeoff

performance. A delayed application of takeoff

thrust will increase the time and distance to

reachV1 speed.Consequently,lessrunwaywill

be left to stop the airplane should an RTO be

necessary. The thrust should be set promptly,

according to the airframe manufacturer’s

recommendations. The non-flying pilot or 

flight engineer then typically makes any final 

adjustments and monitors the engines for any

abnormalities.

On airplanes equipped with autothrottles, an

additional item to be aware of is that some

autothrottle systems incorporate “Thrust

Hold” features which will stop advancing

the thrust levers after the airplane reaches a

predetermined threshold airspeed value. A

delay in engaging the autothrottle can result in

the thrust stabilizing below the takeoff target

setting and the initial acceleration being less

than required.

The engine instruments should be monitored

closely for any abnormal indications. Past

RTO accidents have occurred after an engine

problem was identified early in the takeoff roll, 

but no action was initiated until the airplane

had reached or exceeded V1.

Company operations manuals or training

manuals contain correct proceduresforsetting

takeoff thrust. Observing these procedures

assures efficient engine acceleration and, as 

a consequence, proper aircraft acceleration

throughout the entire takeoff roll.

2.3.6.5 Manual Braking Techniques

Modulation of brake pressure or “pumping the

brakes” was the way most people were taught

to apply automobile brakes when braking

conditions were less than favorable. This

preventedsustainedskidsandthereforeafforded

both better braking and directional control.

Both benefits occur because a skidding tire 

produces less frictional force than a tire which

continuestorotate.Flightdeckobservationand

simulator testing, however, both indicate that

thistechniquehasattimesbeencarriedoverinto

the cockpit of jet transports. With the antiskid

control systems in jet transport airplanes this

technique is not only unnecessary, it results

in degraded stopping capability and therefore

excessive stopping distance especially for

adverse runway conditions. Proper braking 

technique in an RTO is to apply full brake 

pedal force (“stand on it”) and maintain full 

brake pedal force until the airplane comes 

to a complete stop.

The pilot’s foot position relative to the rudder

pedal canalsohave aneffectonthe achievement

of full brake pressure. It was noted during a

study conducted by the Training Aid Working

Group6 thatfootposition duringthe takeoffroll

tendstobeanindividualpreference.Somepilots

prefer to have their feet “up on the pedals” to

be ready to apply full brakesif required. Pilots

who prefer this technique also noted that their

toes are “curled back” to avoid unwanted brake

applications when applying rudder. The other

technique is to rest the heels on the floor during 

the takeoff roll, and then raise them to be on

the pedal to apply full braking. No problems

were noted with either technique.	

One technique which did not work well was

also noted.It is not possible to apply maximum

brake pedal deflection, and hence full brake 

pressure, if the heel of the foot is left on the

floor, unless the pilot has very big feet. In an 

RTO stop maneuver, the feet should be up on

the rudder pedals and steady, heavy pressure

applieduntilthe airplane is completelystopped.

Pilots should develop a habit of adjusting their

seat and the rudder pedals prior to leaving the

gate.The abilitytoapplymaximumbrakepedal

force as well as full rudder should be checked

by both pilots.

6

The Training Aid Working Group is the industry and regulatory team that developed the Takeoff Safety Training Aid.

SECTION 2

2.37
The importance of maintaining maximum

braking and full reverse thrust during an RTO

until the airplane “rocks to a stop” cannot be

over-stressed. During a reject from V1, the

goal is safety, not passenger comfort. The

amount of distance required to decelerate from

a given speed at the high weights associated

with takeoff is significantly greater than from 

the same speed at a typical landing weight. If

the pilot tries to judge the amount of runway

remaining against the current speed of the

airplane,the visual perception thatthe airplane

will stop on the runway (“we’ve got it made”),

will prompt a decrease in the stopping effort.

It is precisely at this point in the RTO that the

difference between a successful Go/No Go

decision and an accident can occur. The brakes

may be nearing their energy absorption limits

and the airplane may be entering a portion of

the runwaycontaminatedwithrubberdeposits,

which can be very slick if wet. In several of

the RTO accidents and incidents of the past,

there was excessrunway available to complete

the stop, but the premature relaxation of the

stopping effort contributed to an overrun.

An additional consideration in completing a

successfulRTOisthatthecrewshouldassessthe

conditionofthe airplane afterit comestoa stop.

If there is evidence of a fire or other significant 

hazard to the passengers, an evacuation on the

runway is definitely preferable to “clearing 

the active.” Every second counts in an actual

emergency evacuation. In at least one RTO

accident, many of the fatalities were caused by

delaying the evacuation until the aircraft was

clear of the runway.

2.3.6.6 Antiskid Inoperative Braking 

Techniques

Antiskid inoperative dispatches represent a

special case for brake application techniques.

In this situation the pilot executing the RTO

should apply steady moderate pedal pressure

consistent, in his judgement, with runway

conditions, airplane dispatch weight and the

available runway length. Full brake pressure

should not be applied with the antiskid system

inoperative due to the risk of tire failure. To

minimize the possibility of skidding a tire,

which can lead to a blowout, the speedbrakes

should be deployed before brakes are applied.

This providesthe highest possible wheel loads

to keep the wheels rotating with the forward

motion of the airplane.	

2.3.6.7 RTO Autobrakes

Autobrakesystemfunctionsandcrewactionsto

initiate these functions vary from one airplane

model to another. For example, some systems

include automatic spoiler extension, others do

not.Therefore,traininginuseofthesystemmust

be tailored to the particular system installed.

The followingdiscussionillustratesthegeneral

intent of autobrake systems.

Brake application is an immediate pilot action

when initiating an RTO, and this application

should be of maximum effort. An automatic

brake application system called “RTO

AUTOBRAKES”isbeinginstalledonmoreand

more airplanestoday to insure that this critical

step is performed as rapidly as possible when

an RTO isinitiated. Thissystem is designed to

automatically apply maximum brake pressure

if during the takeoff roll, all the thrust levers

are retarded to idle, and the aircraft speed is

above a specified value (usually 85-90 knots). 

RTO Autobrakes therefore, achieve the same

airplane stopping performance as a proper,

manual application of full foot pedal braking.

NotimedelaysarebuiltintotheRTOautobrakes

such as are used in some landing autobrake

settings.

The use of “RTO AUTOBRAKES” eliminates

any delay in brake application and assures

that maximum effort braking is applied

promptly. Possible application delays arising

from distractions due to directional control

requirements in crosswinds, or application of

lessthanmaximumbrake force, are completely

SECTION 2

2.38
eliminated. The results of a simulator study

conducted by the Training Aid Working

Group also suggest that, on the average,

those RTOs performed with RTO autobrakes

ARMED resulted in more runway distance

remaining after the stop than did the RTOs

performed using manual braking only. This

result is more significant because few pilots 

left the autobrakes engaged for more than

a few seconds before overriding them and

applying full manual braking. The difference

in stopping performance is attributed to the

first few seconds of high deceleration with the 

autobrakes at full pressure.

When the RTO autobrakes are ARMED for

takeoff, the pilot not flying must monitor the 

system and advise the pilot flying if a DISARM 

condition occurs. The pilot flying should also 

monitor the deceleration of the airplane for

acceptability and be prepared to apply manual

braking if required or, the pilot performing

the reject procedure should apply maximum

manual braking during the RTO. In this latter

case arming the RTO autobrake function only

serves as a backup if for some reason manual

braking is not applied.

The brake pedal forces required to disarm the

autobrakes may vary significantly between 

the landing autobrake settings and the RTO

autobrakesettingofanygivenairplane,between

one airplane model and another of the same

manufacturer, as well as between the various

manufacturers’ airplanes. It is not surprising

that this point is not fully understood in the

pilot community. It is important that pilots be

made aware of howthe details of any particular

airplane’s autobrake system might affect RTO

performance andthattheyobtainthenecessary

information from their training department.

2.3.6.8 (Not Used)

2.3.6.9 The V1 Call

One importantfactorin avoidingRTO overrun

accidentsisfor the crew to recognize reaching

V1whentheairplanedoes,infact,reachV1—not

after. The airplane’s stopping performance

cannot match that specified in the Airplane 

FlightManualifthe assumptionsusedtoderive

that performance are violated, knowingly or

inadvertently. Operationally, careful attention

to procedures and teamwork are required to

match the human performance recognized by

the AFM.

Basic operating procedures call for the pilot

flying the airplane to include airspeed in his 

instrumentscan during the takeoff ground roll.

Hence he is always aware of the approximate

speed. The pilot not flying monitors airspeed 

in more detail and calls out “Vee One” as a

confirmation of reaching this critical point in 

the acceleration.	 	

The pilot flying cannot react properly to V1

unlessthe V1 call ismade in a timely, crisp, and

audiblemanner. Onemethod of accomplishing

this by amajorU.S. carrieristheir adoption of a

policy of “completing theV1 callout by the time

the airplane reaches V1.” This is an excellent

example of the way airlines are implementing

proceduresto improve RTO safety. It is a good

procedure and it should preclude a situation

where the “No Go” decision is inadvertently

made after V1. However, the success of such

a policy in reducing RTOs after V1, without

unduly compromising the continued takeoff

safety margins, hinges on the line pilot’s

understanding of the specific airplane model’s 

performance limitations and capabilities.

Another proposal for calling V1 is to use a call

such as “Approaching V1” with the V1 porti

occurring asthe airspeed reaches V1. Either of

theseproposals accomplishthe taskof advising

the flying pilot that the airplane is close to the 

speedwhere anRTOfor all butthemostserious

failures is not recommended.

SECTION 2

2.39
A frequently cited factorinRTO accidentsthat

occurred when the First Officer was flying is the 

lack of any airspeed calls by theCaptain during

the takeoff.Thistypeofpoor crewcoordination

may be overcome by the use of automated

“V1” and “Engine Failure” calls which will

eliminate much of the variability experienced

in today’s operations. Even with an automated

call system however, an “Approaching” call

by the non-flying pilot would still seem to be 

an appropriate method of ensuring airspeed

situational awareness for both pilots.

2.3.6.10 Crew Preparedness

Important crew factors directly related to

eliminating RTO overrun accidents and

incidents are:

-	 Brief those physical conditions which

might affect an RTO that are unique to

each specific takeoff.

-	 Both pilots must be sure to position the

seat and rudder pedals so that maximum

brake pressure can be applied.

-	 Both pilots should maintain situational

awareness of the proximity to V1.

-	 Use standard callouts during the takeoff.

-	 Transition quickly to stopping

configuration.

-	 Don’t change your mind. If you have

begun an RTO, stop. If you have reached

V1, go, unless the pilot has reason to

conclude that the airplane is unsafe or

unable to fly.

-	 Use maximum effort brake application.

-	 Assure deployment of speedbrakes.

-	 Use maximum reverse thrust allowable.

The accidentrecordsfrequently showthatslow

or incomplete crew action was the cause of,

or contributed to, an RTO overrun event. The

crew must be prepared to make the Go/ No Go

decisiononeverytakeoff.If a “NoGo”decision

is made, the crew must quickly use all of the

stopping capability available. Too often, the

recordsshowuncertaintyinthedecisionprocess

and a lack of completeness in the procedures.

Be ready to decide and be ready to act.

2.4 Crew Resource Management

Crew Resource Management (CRM) is a term

that can mean many things. In this context it

is simply intended to encompass the factors

associatedwithhavingthe crewmemberswork

effectively together to make optimal Go /No

Godecisions andeffectivelyaccomplishrelated

procedures. It is recognized that the content of

aCRMdiscussiononGo/NoGodecisionsmust

reflect the needs and culture of each individual 

operator. Therefore, the material contained in

this section is provided only as an example of

the type of CRM information which could be

provided to the line pilot.	

2.4.1 CRM and the RTO

EffectiveCRMcanimprove crewperformance

and in particular, decision making during

takeoff. Often, Go/ No Go decisions must be

made “instantaneously” and as a result, the

significance of CRM is not readily apparent. 

However,the factthat a criticaldecisionmustbe

made andimplementedusingrapidlychanging,

often incomplete information in a dynamic

environment in which the time available

decreases as the criticality of the decision

increases, is reason for effective CRM. Some

aspects of CRM are especially important with

respect to the Go/ No Go decision.

2.4.2 The Takeoff Briefing

Crew members must know what is expected

of them and from others. For optimum crew

effectiveness, they should share a common

perception — a mental image — of what is

happening and what is planned. This common

perception involves a number of CRM areas:

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2.40
communications, situational awareness,

workload distribution, cross-checking, and

monitoring.

A variety of means are used to achieve this

common perception. This begins with airline

standard operating policies(SOPs) that clearly

define captain and first officer as well as pilot 

flying and pilot not flying responsibilities and 

duties.Trainingreinforcesthecrew’sknowledge

and skill, while standardization insures

acceptable, consistent performance, across all

fleets and cultures within an airline. 

A takeoff briefing is another means of

improving the crew’s awareness, knowledge,

and team effectiveness, especially when

special circumstances or conditions exist.

The briefing is not necessarily a one-way 

process. In fact, asking for clarification or 

confirmation is an excellent way to insure 

mutualunderstandingwhenrequired.Asimple,

“standard procedures” takeoff briefing might 

be improved by adding “I’m not perfect, so

back me up on the speedbrakes and my use

of the RTO autobrakes” or, “if we’re not sure

of an engine failure 5 knots before V1, we’ll

continue the takeoff andI’llstate ‘CONTINUE

TAKEOFF”’. These briefings can improve team 

effectiveness and understanding of the Go/No

Go decision planning and communications to

be used. Such additions might be especially

appropriate on the first segment of a flight with 

a relatively new first officer or a crew’s first 

flight of the month.

A review of actionsfor a blown tire, high speed

configuration warning, or transfer of control 

are examples of what might be appropriate

for before takeoff (or before engine start)

review. Such a briefing should address items 

that could affect this takeoff, such as runway

contamination, hazardous terrain or special

departure procedures. The briefing should not 

be ameaninglessrepetition of known facts, but

rather a tool for improving team performance,

that addresses the specific factors appropriate 

to that takeoff.

2.4.3 Callouts

Meaningful communication, however brief,

regarding a non-normal situation during

takeoff andRTO can oftenmean the difference

between success and disaster. For this reason,

communications must be precise, effective,

and efficient. Standard callouts contribute to 

improvedsituationalawareness.Thesecallouts,

coupled with all crewmembers being aware

of airspeed, maximize the opportunity for a

common understanding of what actions are

proper in the event of a non-normal situation.

The crewmember noting a problem should

communicate clearly and precisely without

inferring things that may not be true. For

example, the loss of fuel flow indication alone 

does not necessarily mean an engine failure.

Use of standard terms and phraseology to

describe the situation is essential. The pilot

tasked tomake theRTOdecision should clearly

announcethisdecision,whetheritbetocontinue

or reject.	

2.4.4 The Use of All Crew Members

It’s important to understand that all crew

members on the flight deck play an important 

role in the Go/No Go decision and RTO

maneuver. Company policies shape these

roles. However, how the team is organized for

each takeoff can make a difference in team

performance. Knowing your own capabilities

and that of the other crewmembers is part of

situational awareness and should be used in

planning for a given takeoff. Although it’s “the

first officer’s leg”, it might not be an effective 

plan to task an inexperienced first officer with 

amarginal weathertakeoff when weight is also

limited by field length. Consider the possibility 

of an RTO when assigning takeoff duties.

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2.4.5 Summary

Each airline approaches CRM in a slightly

different manner, but the goal of effective

teamworkremainsthe same.Thismaterialis an

example of the type of CRM information that

could be used to promote a common perception

of RTO problems and actions.

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