Consideration of Brakes and Reverses

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CONSIDERATIONS ON BRAKES AND THRUST

REVERSER USAGEGiuliana Fonseca

EMBRAER - Flight Operations Liasion


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THIS INFORMATION IS EMBRAER PROPERTY AND CANNOT BE USED OR REPRODUCED WITHOUT WRITTEN AUTHORIZATION

Considerations on Brakes and

Reversers usage

Agenda Introduction

Some facts

Some numbers

Case studies

Final considerations


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Reversers usage

Agenda Introduction

Some facts

Some numbers

Case studies



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Reversers usage

IntroductionUsually, landing performance do not take into

account the use of TRs

TRs are a bonus for increased safety marginsOn the other hand, carbon

brakes are more efficient

under certain conditionsTRs and Brakes operating

policies vary from an

operator to another...


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Reversers usage

So, whats the best option???Should T/Rs be used on all landings?

Or should they be used only on

restricted/contaminated runways?How can I save my (expensive)

carbon brakes?

Can I combine Autobrake with T/Rs?


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Reversers usage

Agenda Introduction

Some facts

Some numbers

Case studies



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Reversers usage

Facts about reversers

TRs are more effective at high speeds;

Its use below 60 kt increases the chances of foreign object

ingestion by the engine;

TRs are stopping devices

that do not depend on runway

condition, but its importance

increase on slippery runways;Costs of TRs usage are difficult

to determine since maintenance

is usually part of agreements

with engine manufacturer.


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Reversers usage

Facts about carbon brakes

Brake wear is far more related to

the number of applications than to

the energy applied

Braking performance can beoptimized by applying maximum

continuous pressure on the brake

pedals. The ANTI-SKID system will

modulate the brakes if required

Pedals should not be pumped!!!


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Reversers usage

Facts about carbon brakes

(Cont.)

Test results show brakes wear is

minimized around 200C

Carbon brakes wear faster when

they are cool

Costs of brakes usage are (also)

difficult to be determined due toparticular

agreements with the brakes

supplier


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Reversers usage

Facts about performance...

Autobrake system works aiming a deceleration target:

a) LO mode: - 4 ft/s2

b) MED mode: - 8 ft/s2

c) HI mode: -13 ft/s2.

Brakes applied as required to reach

target deceleration level

Deceleration is affected by three factors: Aerodynamic drag

Wheel brakes

Reverse thrust


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Reversers usage

Facts about performance (Cont.)...In a nutshell, if the braking coefficient is good,

the thrust reversers will not help the landing

performance

Time

Deceleration

Total Deceleration

Brakes Deceleration

Reversers Deceleration

Autobrake Target


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Reversers usage

Facts about performance (Cont.)...but, if the braking coefficient is NOT good, the

thrust reversers could help achieve the

maximum deceleration

Total Deceleration

Brakes Deceleration

Reversers Deceleration

Autobrake Target

Time

Deceleration


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Reversers usage

Agenda Introduction

Some facts

Some numbers

Case studies



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Reversers usage

Carbon Brakes Assembly Replacement

Reason: Worn to limits, damaged, inop, leakage, cycle limit, etc.

EJETS - SCHEDULED REMOVALS RATE L12M

BRAKE ISSUES

0,000

0,050

0,100

0,150

0,200

0,250

0,300

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D

2007 2008 2009

Ratep

er100

S.F

E-Jets - Brake Removals


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Reversers usage

MLG Tire / Wheel Assembly Replacement

Reason (Worn to limits, damaged, time limit, etc.)

EJETS - SCHEDULED REMOVALS RATE L12M

TIRE AND WHEEL ISSUES

0,000

0,500

1,000

1,500

2,000

2,500

3,000

3,500

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D

2007 2008 2009

Rate

per100S.F

E-Jets - Wheel and Tire Removals


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Reversers usage

So what??

On the previous plots there is no clear correlation

between brake wear and wheel/tire

replacements...

so, best practices for saving brakes do not

necessarily mean that there will be more wear on

wheels and tires!


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Reversers usage

So what?? (Cont.)

As a reference, a 500 cycles increase in brakes life

represents a reduction of about 6 USD/FC on brakes

cost (USD 12.000,00 considering a 2000 cycles per

acft/yr average utilization)

Using TRs for 15 sec per flight increases fuel

consumption by about 20lbs per landing (USD

10.000,00 acft/yr considering TRs always used,

2000 cycles per acft/yr average utilization and fuel

@ USD 2/Gal)


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Reversers usage

Agenda Introduction

Some facts

Some numbers

Case studies



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Reversers usage

Case studies

Operators in Americas, Europe, Middle East and

Asia Pacific were asked about their policies for

brakes, autobrakes and TRs utilization

Environmental conditions and severe winter do

have an effect on brakes life...

...but most of all, good practices do make thedifference!


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Reversers usage

Case studies TRs used on all landings;

TRs always deployed but used only

on short, wet or contaminated

runways;

TRs used as required being:

limited to idle reverse on normal

landings

Mandatory on contaminated

runways

Rational utilization of TRs and

autobrakes during landing, taxi and

parking. Brake wear reductionpolicies are adopted and spread

between pilots.

Using an average overhaul cost,

each variation of 0,100 means

~USD 33,00 per FC.


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Reversers usage

Agenda Introduction

Some facts

Some numbers

Case studies



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Reversers usage

What have we seen so far

...on Brakes: Carbon brakes wear is much more a function of number of

applications than of the energy applied. Then its not a good ideato pump the pedals

Brakes wear is greater when they are cool (


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Reversers usage

and on Reversers

If the autobrake is set to LO, reversers should not be used as thesystem will disengage brakes anytime the target deceleration issensed

Whenever the airplane braking coefficient is good and autobrakesare used (any setting), the T/Rs will not improve the landingperformance

For expected braking coefficient medium or poor, the use of thrustreversers could increase the airplane deceleration, decreasing thelanding distance

The T/R should only be used when the pilots judgment says to doso, according to the airplane speed, weight, weather conditions,etc.


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Reversers usage

Remember our initial questions:

How can I save my expensive carbon brakes?

Should TRs be used on all landings?

Can I combine Autobrake with TRs?

Now we should be able to get them

answered


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Reversers usage

and dont forget:

Safety and passenger comfort come first!


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Reversers usage

THANK YOU

Documents

Consideration of Brakes and Reverses