Lecture 07   Aircraft Brakes System
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Lecture 07 Aircraft Brakes System

September 8, 2019


so we have seen the different types of landing
gears the types of wheel assemblies installed in the landing gear the different types of
tires tubes another part of the landing system a very important part is the aircraft brake
system the brakes as we all know in all automobiles brakes are an essential component in any vehicle
similarly in aircrafts also brakes are a very important part so in this module we will see the different
types of brakes we will be starting with the basic types of brakes and then we will see
how different types of brakes are installed so the brakes slow the aircraft and stop it
in a reasonable amount of time we all know that brakes the what is the basic purpose
of the brakes they slow the aircraft and stop it in a reasonable amount of time they hold
the aircraft stationary during engine run up and in many cases steer the aircraft during
taxi in typical brake system mechanical linkages
or hydraulic linkages to the rudder pedals allow the pilot to control the brakes pushing
on top of the right rudder pedal activates the brakes on the right main wheel and pushing
on the top of the left rudder pedal operates the brakes on the left main wheel so basically
the ra the rudder pedals are depressed on the top for the right brake system the right
pedal is depressed and for the left brake the left pedal is depressed the basic operation of brakes involves converting
the kinetic energy of motion into heat energy through the creation of friction so basically
the mo kinetic energy is being created is being converted into heat energy through friction
modern aircraft is mainly using disc brakes the size weight and landing speed of the aircraft
influence the design and complexity of the disc brake system so depending on the aircraft type the size
of the aircraft the weight of the aircraft the landing speed of the aircraft accordingly
the design and complexity of the brake system is designed so the different types of brakes
they may be single dual or multiple disc brakes as we a mentioned earlier mainly the aircrafts
are using disc type brakes depending on the aircraft design depending on the type of aircraft
the brakes may be either of single disc brakes dual disc type or multiple disc type segmented rotor brakes are also used on large
aircraft bigger aircrafts segmented rotor brakes are used and in older aircrafts the
expanded tube brakes were being used as the sophistication is increasing as we are getting
better materials now a days the use of carbon discs is increasing in the modern aviation
fleet now coming to single disc brakes so how a
disc brake works you can see in the diagram this is your hub assembly this your wheel
wheel now this rotor you can see here rotor this is the disc which is attached to the
wheel hub on both sides of the disc you can see here these are the brake pads or we call
them the brake lining this is the fixed these brake linings you can see this is fixed one
is on the other side this is the piston and you getting the hydraulic pressure from the
side so small light aircraft typically achieve
effective breaking using a single disc keyed or bolted to each wheel so you can this rotor
or a disc is keyed to the wheel assembly as the wheel turns so does the disc since this
disc or this rotor is keyed to the wheel assembly as the wheel turns the dis will also turn braking is accomplished by applying friction
to both sides of the disc so braking is accomplished by applying friction to both sides of the
disc you can see you have the brake pads or the brake linings on both sides of the disc
due to which the friction is created these brake liners or the brake pads they are fixed
in a unit called a caliper they a they are mounted here in the caliper and are which
are bolted to the landing gear axle flange you can see this your landing gear axle flange
here they are bolted to this place pistons in the caliper housing under hydraulic
pressure this is the piston this is coming under the hydraulic pressure the your hydraulic
pressure is coming from this side this forces wearable brake pad these brake pads they are
wearable they get worn out or linings against the disc when the brakes are applied so when
the brakes are applied by pressing the rubber pedals by pressing the top the rudder pedals
in the cockpit hydraulic pressure is created from this side this hydraulic pressure forces the piston
when this piston is supposed this will push these brake linings against the disc as a
result friction will be created and braking action will happen hydraulic master cylinders
connected to the rudder pedals supply the pressure when the upper hubs on the rudder
pedals are pressed so your rudder pedals are connected to the two hydraulic master cylinders the hydraulic master cylinders they supply
the pressure when the upper half of the rudder pedals are pressed so as the aircraft sizes
became larger single disc brakes were not effective so there was a necessity to have
brakes which could provide more braking action so dual disc brakes were design dual disc
brakes are used on aircraft where a single disc on each wheel does not supply sufficient
braking friction in this dual disc brakes there are two discs you can see in the diagram there are two discs this is one disc this
is another disc these two discs are key to the wheel instead of one so these two discs
they are key to the wheel a center carrier is located between the two discs this is your
center carrier you can see this this is your center carrier this is located between the
two disks it contains linings on each side so on each side you can see these linings
this is the lining there is one lining here on both sides of the disc one lining here
on both sides of the disc one lining on this side one lining on on the
other side of the disc similarly on this disc you can see there is one lining here and on
the other side also you can see there is one lining so on both sides of the disc there
are brake linings the center carrier is located between the two discs this is the center carrier
this is located between the two discs it contains linings on each side so you have the linings on each side that
contact each of the discs so these linings will contact the discs when the brakes are
applied so basic principle is the same as the single disc a brakes but in this you have
two discs the caliper mounting bolts are long and mount through the center carrier these
are the mounting bolts they are long and they mount through the center carrier as well as
the black plate this is the black plate this bolt goes through the black plate and the
center carrier and it bolt the housing assembly in this diagram you can see two discs are there your braking
is happening due to the friction between the brake linings and the discs the brake linings
are there on both sides of the disc and these brake discs they are attached to the center
carrier so these discs they are mounted to the wheel hub when the wheel rotates the discs
will also rotate these linings will provide friction to the rotating discs and the braking
will happen now another complex type of brakes is the multiple disc brakes we have seen the single disc brake we have
seen the dual disc brake now this is multiple disc brakes large heavy aircraft require the
use of multiple disc brakes multiple disc brakes are heavy duty brakes designed for
use with power brake control walls or power boost master cylinders so as we have mentioned
earlier depending on the type of aircraft depending on the size of the aircraft the
brakes are designed so for large and bigger aircrafts multiple disc brakes are required they are heavy duty brakes designed for use
with power brake control walls or power boost master cylinders so in this diagram you can
see there are various discs various rotors here you can see these are the rotors this
is the rotor one two three four so you can see there are four rotors here status you
can see this is one two and three three status so rotor stator rotor stator rotor stator
rotor and then you have the back plate at the end on one side you have the back plate
and on the other side you have the pressure plate so you the pressure plate then you have the
rotor then stator rotor stator rotor stator rotor and then the back plate so this is the
multiple disc break it supports the various break parts including an annular cylinder
and piston here you can see this is the piston this is the piston a series of steel discs
alternating with copper or bronze plated discs so these discs or the rotors they may be copper
made of copper material or bronze then there is a back plate and a back plate retainer
so it supports the various brake parts including an annular cylinder and piston
this is your annular piston series of steel discs alternating with copper or bronze plated
discs a black plate and a back plate retainer in the diagram this diagram you can see this
is one type there one type of multiple disc brakes there may be other types of multiple
disc brakes with different materials also the steel status the steel status are key
to the bearing carrier these these steel status they are keyed to the bearing carrier this
is your bearing carrier these stators are key to the bearing carrier and the copper
or bronze plated rotors that stators are of steel the rotors may be
of copper or bronze and these rotors are key to the rotating wheel so the stators are key
to the bearing carrier and the copper or brass plated rotors are key to the rotating wheel
hydraulic pressure applied to the piston now hydraulic pressure is applied to this piston
it causes the entire stack of stators and rotors to be compressed so when the hydraulic pressure is applied
to the piston that hydraulic pressure via the piston will cause the entire stack of
stators and rotors to be compressed this creates enormous friction and heat and slows the rotation
of the wheel so due to the hydraulic pressure it it compresses the stack of stators and
rotors this creates enormous friction and heat and eventually slows the rotation of
the wheel so this is about the multiple disc brakes
we have seen the single disc brake we have seen the dual disc brake and we have seen
the multiple disc brakes now another type of brakes where we have segmented rotors so
the discs they are of discs they are of disc disc type only but the discs are segmented
the large amount of heat generated while slowing the rotation of the wheels on large and high
performance aircraft is problematic and due to friction large amount of heat is generated
and this large amount of heat can be of problem so to minimize this problem segmented rotor
brakes were designed to better dissipate this heat you can see in the diagram these are
your rotors one two three and you can see these rotors they are all segmented the rotors
are segmented then you have the status you can see these are your status means the this
is the stator plate stator then you have the back plate here then the pressure plate on
the other side so in this you can see there is a pressure plate then you have the rotor you have the stator
rotor stator rotor and back plate so it is almost the same type as the multiple disc
brake the difference is that the rotors they are segmented to better dissipate the heat
generated due to friction segmented rotor disc brakes are heavy duty brakes they are
heavy duty brakes specially adapted for use with high pressure hydraulic systems or power
brake systems so they are used with high pressure hydraulic
systems or power brake systems braking is accomplished by means of several sets of stationary
high friction type brake linings that make contact with the rotating segments so similarly
as in the multiple disc brakes braking is accomplished by means of several sets of stationary
high friction type brake linings that make contact with the rotating segments the rotors are constructed with slots you
can see the rotors they are constructed with slots or in sections with space between them
so there is space between the sections which helps dissipate heat and give the brake its
name so these plots are designed in the rotors which helps them to dissipate heat so that
is why they are called segmented rotor brakes segmented rotor multiple disc brakes are the
standard brakes used on high performance and air carrier aircrafts now another type of
brakes carbon brakes it is currently found on high performance
and air carrier aircrafts carbon brakes are so named because carbon fiber materials are
used to construct the brake rotors carbon brakes are approximately forty percent lighter
than conventional brakes the carbon fiber discs are noticeably thicker than sintered
steel rotors but are extremely light so you can see in the diagram there are carbon brakes
they are found on high performance and air carrier aircraft they are so named because the carbon fiber
materials are used to construct the rotors in this the rotors are made of carbon material
they are carbon brakes are approximately forty percent lighter than the conventional brakes
the carbon fiber discs are noticeably thicker than the sintered standard steel rotors but
are extremely light these carbon brakes they are able to withstand temperatures fifty percent
higher than the steel component brakes so one of the advantages of the carbon brakes
they are able to withstand temperatures like fifty percent higher than the steel brakes
the maximum designed operating temperature is limited by the ability of the adjacent
components to withstand the high temperature so the components which are there in the surrounding
adjacent components they should be able to withstand the high temperatures generated a carbon rotor maintains its strength and
dimensions at high temperatures so the carbon rotor will maintain its strength and dimensions
at high temperatures moreover carbon brakes last twenty to fifty percent longer than the
steel brakes which redue results in reduced maintenance so we have seen the advantages
of carbon brakes as with passage of time we are getting better materials so we are able
to get better brakes where we are a finding to have better qualities and reduced maintenance
so the different type of brake actuator systems there are mainly three types of basic actuated
systems one is the independent system booster system power brake system again depending
on the type of brakes type of aircraft the brake actuating systems are designed the independent
system is not part of the aircraft main hydraulic system that is an independent system as its name suggests booster system uses the
aircraft hydraulic system intermittently when needed and the power brake system only uses
the aircraft main hydraulic system as a source of pressure so three types of system independent
system which is not part of the main hydraulic system booster system that uses the aircraft
hydraulic system intermittently and the power brake system that uses the aircraft main hydraulic
system as a source of pressure independent master
cylinders this is basically the independent type of brake actuating system which has got
independent brake master cylinders in the diagram you can see these are your rudder
pedals these are your master cylinders these master cylinders have a reservoir fluid reservoir
then these are your brake linings this is your brake lining this your brake assembly
here and this is your wheel in this lining you can see there is a wall
called a marking brake wall similarly on the other line also you have the parking brake
wall and this is connected to a brake unit here is the brake unit this is a very basic
type of a brake system small light aircraft and aircrafts without hydraulic systems use
independent braking systems so very small aircrafts light aircrafts aircrafts which
do not have a hydraulic system they use independent brake system
an independent brake system is not connected in any way to the aircraft hydraulic system
since as the name suggests this is an independent system the independent brake system is in
no way connected to the main aircraft hydraulic system so this system can be used on aircrafts
which do not have the hydraulic system since this is of independent type master cylinders
are used to develop the necessary hydraulic pressure to operate the brakes these are the master cylinders these are the
master cylinders which are used to develop the necessary hydraulic pressure to operate
the brakes in most brake actuating systems the pilot pushes on top of the rudder pedals
so pilot will push on top of the rudder pedal to apply the brakes a master cylinder for
each brake so this is the master cylinder for this line for right line and this is the
master cylinder for the left line a master cylinder for each brake is mechanically connected
to the corresponding rudder pedal so this master cylinder is mechanically connected
to the rudder pedal that is right main brake to the right rudder pedal and left main brake
to the left rudder paddle when the pedal is depressed now when this pedal is depressed
a piston inside a sealed fluid filled chamber in the master cylinder in this master cylinder
there is a piston here and there is a chamber which is filled with fluid so when the pedal
is depressed piston inside a sealed fluid filled chamber this chamber is sealed and end the is filled
in this chamber forces hydraulic fluid through a line to the piston in the brake assembly
so when the pedal is depressed this piston will force the hydraulic pressure to move
from this line to the brake assembly so this brake assembly we have earlier seen that it
also has a piston so this hydraulic pressure will push the piston here and this piston
will push the disc will provide friction via the brake linings pressure is increases throughout the entire
brake system and against the rotor as the pedal is pushed harder so when this hydraulic
pressure is applied the brake piston will push the brake linings this brake pressure
will push the brake linings against the brake rotor against the brake disc to create friction
that slows the wheel rotation so this hydraulic pressure will push the brake linings against
the disc or the rotor and it will create friction that will slow the wheel rotation pressure is increased throughout the entire
brake system and against the rotor as the pedal is pushed harder so this is the independent
brake system a very basic type of brake system now boosted brakes boosted brake actuating
systems augment the force developed by the pilot with hydraulic system pressure when
needed so as the name suggests this boosts the brake the force developed by the pilot
this will boost the force developed by the pilot with hydraulic system pressure when
it is required the boost is only during heavy braking it
results in greater pressure applied to the brakes that the pilot alone can provide so
this provides a boost to the pressure which is created by the pilot it results in greater
pressure applied to the brakes that then the pilot alone can provide boosted brakes are
used on medium and large aircraft that do not require full power brake actuating since
system a boosted brake master cylinder for each brake
is mechanically attached to the rudder pedal so the master cylinder for this boosted brakes
is of a special type and is mechanically attached to the rudder pedal however the boosted brake
master cylinder operates differently a master cylinder for a boosted brake system augments
the foot pedal pressure with aircraft system hydraulic pressure during heavy braking so
foot pedal pressure is augmented with the aircraft hydraulic system pressure
during heavy braking another type of brakes the power brake large and high performance
aircraft are equipped with power brakes to slow stop and hold the aircraft so power brakes
are used on high performance aircrafts to slow stop and hold the aircraft power brake
actuating systems use the aircraft hydraulic system as the source of power to apply the
brakes so this type of brake system this these type of brakes they use the aircraft hydraulic
system pressure as the power as the source of power to apply the brakes the pilot presses on top of the rudder pedal
for braking as with the other actuating systems in this type of system also pilot will press
the rudder pedals here you can see these are the rudder pedals these rudder pedals they
are mechanically linked here these are the brake metering balls this is the brake metering
wall and you have an alternate brake metering valve also and you can see similarly on the
right side this is the rudder pedal brake metering valves on this then you have
the anti skid balls the fuses the shuttle valve and these are the wheels this is a more
complex system we will not go in detail for this system just giving you a b basic idea
about what power brake is so power brake control wall or brake metering wall these are the
brake metering wall receives the brake pedal input these walls will receive the brake pedal
input either directly or through linkages the valve meters hydraulic fluid to the corresponding
brake assembly so this the purpose of this brake metering valve is to meter the hydraulic
fluid to the brake assembly in direct relation to the pressure applied to the pedal so the
pressure which is applied to the pedal direct in direct proportion to that pressure applied
the hydraulic fluid is metered and sent to the wheel assembly now parking brakes parking brakes they are
a very important part of the brake system the parking brake system function is a combined
operation so this is the diagram for in this stop diagram you can see this is the diagram
where you can see the brake pedals here these are the reservoirs now master cylinders in
the master cylinders you have the fluid reservoir also this is your brake line this is the brake unit and this is the your
wheel assembly and the tyre so in this brake lining there is a parking brake valve the
brakes are applied with the rudder pedals and a ratcheting system holds them in place
when the parking brake lever on the flight deck is pulled so the brakes are applied with
the rudder pedals so when you activate the parking brake you have to press the rudder
pedals and pull this lever in this bottom diagram
you can see this is your parking brake lever here and this is a ratcheting system this
is mechanically connected so in order to activate the parking brake you have to press the rudder
pedals you have to press the rudder pedals and simultaneously pull this handle the brakes
are applied with the rudder pedals and a ratcheting system holds them in place when the parking
brake lever on the flight deck is pulled this traps the fluid in the brakes holding
the rotor stationary so this when you activate these parking brakes when the parking brakes
are activated this will hold the hydraulic pressure in the brake line this will trap
the fluid in the brakes and will hold the rotors stationary depressing the pedals further
releases the pedal ratchet and opens the return line ball so when you depress the pedals further
this will release the pedal ratchet and will open the return line ball so this was a brief
idea about the parking brakes now what are the inspections we carry out
on the brake system what are the services we are carrying out brake inspection and service
is important to keep these critical aircraft components fully functional at all times brake
system must be inspected in accordance with the manufactures instructions as is as it
is the case with all the systems same with the brake system also manufacturers will issue
various instructions in the maintenance manual and from time to time various inspections
will be mentioned by the manufacturer so the brake system has to be infe inspe inspected
accordingly some common inspection items include brake lining wear air in the brake system
fluid quantity le level and leaks so some of the common inspections in the brake system
the brake lining where we have to be very careful about the brake lining due to friction
the brake linings will wear out and we have to continuously during the pre flight inspections
also we have to continuously look for the brake linings
the air in the brake system in case you find there is air in the brake system you find
the brakes spongy the basic pub the basic reason is air in the brake system and the
fluid quantity levels and leaks in the brake lines lining wear brake lining material is
made to wear as it causes friction during application of the brakes this wear must be
monitored to ensure it has not worn beyond limits and sufficient lining is available
for effective braking so as i just mentioned that brake lining is
a very important component we have to be careful we have to check the brake lining material
as so that it has not worn beyond limits and sufficient lining is available for effective
braking now air in the brake system as i just mentioned in case there is air in the brake
system what will happen you will feel that the brakes are spongy so how to remove air
in from the brake system the presence of air in the brake system fluid
causes the brake pedals to feel spongy the air can be removed by bleeding to restore
from brake pedal so in order to remove the air from the system you need to carry out
brake bleeding brake systems must be bled according to the manufactures instructions
so depending on the manufacturers instructions the brake system bleeding has to be carried
out basically there are two methods of doing the brake bleeding one is the gravity method and the other is
the pressure method so gravity bleeding or the pressure bleeding now pressure bleeding
you can see in the diagram this is the pressure pot here this is your brake unit this is your
brake line this is your master cylinder from the master cylinder this is the brake reservoir
and from the brake reservoir and from the brake reservoir you have a container which
has got the hydraulic fluid so to pressure bleed a brake system from the
bottom up in the pressure system we are bleeding the brake system from the bottom to the upside
a pressure pot is used this is a portable tank that contains our supply of brake fluid
under pressure so this is a portable pot or a portable tank which is having hydraulic
fluid under pressure this will supply brake fluid under pressure when depressing fluid from the tank when depressing
fluid from the tank pure air free fluid is forced from the at the bottom of the tank
by the air pressure above it so air free pure fluid is forced from this tank to the brake
unit the outlet hose that attaches the bleed port so there is a bleed port in the brake
unit this hose will attach to the bleed port on the brake assembly and it also contains
a shut off valve so this portable tank this supplies hydraulic pressure and a fluid to
the brake unit here this pressure pot or a tank this can be substituted
by a hand pe pump type unit found in some of the hangars so the basic idea is to supply
fluid under pressure so when you are supplying hydraulic fluid under pressure from this side
from the bottom the hydraulic fluid and the pressure will force the hydraulic fluid from
the bottom to the up and whatever air is there in the system this will be bled out so the
air in the system will come out in the form of bubbles here in the hydraulic fluid so in the pressure bleeding you are bleeding
it from the bottom to the top another method called the gravity bleeding same thing you
can see here this is your brake reservoir you are pouring in fluid hydraulic fluid in
the brake reservoir from the brake reservoir it is coming to the master cylinder from the
master cylinder via the brake linings it is coming to the brake unit at the brake unit
there is a bleeder port a hose is attached to the bleeder port and this hose is inside
a container having hydraulic fluid a clear hose attached a clear hose to the
brake bleed port fitting on the brake assembly to there is a brake bleed port on the brake
assembly you have to attach a clear hose and immerse this hose the other end of the hose
in a container of clean hydraulic fluid when the bleeder wall was open when the bleeder
wall opens you carefully apply the brakes to allow the aircraft hydraulic fluid to enter
the brake system so you have to open the bleeder valve here and have to carefully apply the
brakes so that the hydraulic fluid enters your brake system
when you apply the brakes the hydraulic fluid will flow to the brake linings and the bleeder
port is opened and this will come out the air in the system will also come out in the
form of bubbles the fluid expels the fluid contaminated with air out of the bleed hose
into the container when air is no longer visible in the hose close the bleed wall and restore
the hydraulic system to normal operation so in the gravity method you can see the hydraulic
fluid is being forced from top to bottom in the pressure system the hydraulic fluid under
pressure was being sent from the bottom to the top now a fluid quantity and type it is
imperative that the correct hydraulic fluid is used in each brake system so we have to
be careful that the correct type of hydraulic fluid as suggested by the manufacturer has
to be used in the brake system seals in the brake system are designed for
a particular hydraulic fluid so the reason that you need to use the specific type of
the suggested type of hydraulic fluid is because of the seals the material of the seals so
seals in the brake system they are designed for a particular hydraulic fluid deterioration
and failure occurs when they are exposed to other fluid mineral based fluids such as mill
h five six zero six should never be mixed with phosphate ester based synthetic hydraulic
fluid such as skydrol so as we have mentioned earlier that the two
types of two different types of hydraulic fluids should not be mixed with each other
contaminated brake hydraulic systems must have all of the fluid evacuated and all the
seals replaced before the aircraft is released for flight so in case if the hydraulic fluid
in the hydraulic system or the brake system is contaminated then we need to evacuate all
the fluid from the system replace all the seals before the aircraft is released for
for the flight inspection for leaks aircraft brake systems
should maintain all fluid inside lines and components and should not leak so the brake
systems should maintain all the fluid inside the lines and components and there should
not be any leak any evidence of a leak must be investigated for its cause it is possible
that a leak is a precursor to more significant damage that can be repaired thus avoiding
an incident or accident so any indication of a leak in the brake line
it must be investigated and rectified before any flight brake malfunctions and damage aircraft
brakes operate under extreme stress and varied conditions they are susceptible to malfunctions
and damage overheating when while aircraft brakes slow the aircraft by changing kinetic
energy into heat energy overheating of the brakes is not desirable so the brakes are
converting the kinetic energy into heat energy but still overheating of the brakes is not
desirable excessive heat can damage and distort brake
parts weakening them to the point of failure when an aircraft is involved in an aborted
takeoff the brakes must be removed and inspected to ensure they withstood this high level of
use so the basic idea is that the brakes should not be exposed to overheating because in case
if they are exposed to overheating it will damage and distort the brake parts and will weaken them and that can result in
failure so in case an aircraft is involved in an aborted takeoff the brakes must be removed
thoroughly inspected and they must be ensured that they are able to withstand high level
of use further use chattering or squealing brakes may chatter or squeal when the linings
do not ride smoothly and evenly along the disc so in case when the linings are not riding
smoothly or evenly along the disc it may result in chattering or squealing a warped disc in a multiple brake disc stack
produces a condition wherein the brake is actually applied and removed many times per
minute this causes chattering and at high frequency it causes squealing so this is about
a multiple disc brake where warped disc will produce a condition where brakes are actually
applied and removed many times per minute this will result in chattering and squealing
any misalignment of the disc stack out of parallel causes the same phenomena so we have
to be careful while using multiple disc brakes warped discs you you have seen can result
in chattering and squealing any misalignment of the disc stack will also cause the same
chattering and squealing dragging brake drag is a condition cause by the linings not retracting
from the brake disc when the brakes are no longer being applied so when the brakes are no longer being applied
still the linings have not retracted then it may result in brake drag it can be caused
by several different factors like excessive lining wear and overheating leading to the
damage to the disc when the return mechanism is not functioning properly this could be
due to a weak return spring so in case the return mechanism is not functioning properly it may be due to a weak return spring that
means your brake linings are have not returned when the hydraulic pressure is removed when
the hydraulic pressure has is been removed basically the brake linings should retract
they should be clear from the brake discs in case if they are not returning they are
not clear of the brake discs they are still touching the brake disc then it may be result
in brake dragging and this may be due to a weak return spring
an overheated brake that has warped the disc also causes brake drag air in the brake fluid
line can also cause brake drag so there are various reasons for brake dragging it may
be air in the brake sys brake fluid line it may be overheated brakes it may be weak return
springs so you have seen different reasons for brake dragging so in any case before further
flights the system must be thoroughly inspected and this brakes the faulty brakes may be removed thank you

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  1. 13:50 by any chance do you know what manufacturing process the torque tube goes through? I'm guessing it's through a casting method. It's for a project I'm working on

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