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fatfallenleafElectronics - Devices

Nov 15, 2013 (3 years and 11 months ago)

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JET PROPULSION

Part
9


Thrust Reversers

Thrust Reversers

What
are they?

Thrust Reversers redirect the gas flow

from a rearward direction

(which provides normal forward thrust)

to a forward direction,

providing reverse thrust

(using the power as a decelerating force)


It is operated by the pilot on landing.

Thrust reversers

reduce the landing roll out.

In civilian aircraft this is primarily

to save wear and tear on the brakes,

to clear busy runways and to achieve

quick turn
-
rounds, i.e. keeping passenger

delays to a minimum.

In military aircraft the above can apply,

and also to give shorter landings for tactical reasons,

i.e. the aircraft can land and unload supplies quickly,

thus minimizing any risk in hostile environments.

Reverser Effects

Shorter Landing Roll
-
out

Divert some or all of the rearward directed jet

in an almost forward direction,

providing a reverse thrust.

The gas stream should be directed

in a completely forward direction;

this is not possible
(except with reverse pitch propellers)

due to aerodynamic reasons.

An angle of 90
o

to 45
o

forward is common,

giving reverse thrust up to 50% of forward thrust.

Reverser Effects

Reverser Effects

Thrust Reversers

Translating Cowl Type

Normal Forward Thrust

BLOCKER
DOORS

BLOCKER
DOOR LINK

TRANSLATING
COWL

TRANSLATING
COWL

Reverse Thrust

CASCADES

Used on


The Tri
-
Star and C17
(illustrated)

The C17 deployment is extremely unusual

in that it can deploy the thrust reversers in flight

for a tactical descent from high altitude,

thereby minimising the threat of

anti
-
aircraft fire etc in a hostile area.

Thrust Reversers

Pivoting Door Type

Normal Forward Thrust

Reverse Thrust

PIVOTING
DOOR

PIVOTING
DOOR

SENTINEL LANDING



THRUST
REVERSERS DEPLOYED

Used on


The RAF Sentinel R17
(illustrated)

It comprises of two doors on this system,

but multi door systems are replacing

the translating cowl designs

on high by
-
pass fan engines.

This is a relatively simple system,

with much less working parts

than the translating cowl design.

The full sequence is controlled by the

Engine Electronic Control unit (EEC),

to ensure the system will not actuate

unless safe to do so.

Thrust Reversers

Clam Shell Door Type

Normal Forward Thrust

CLAM SHELL
DOOR

CLAM SHELL

DOOR

Reverse Thrust

CLAM SHELL
DOOR

CLAM SHELL

DOOR

VC10 LANDING


THRUST REVERSERS DEPLOYED

Used on


The VC 10
(illustrated)

All four engines have the reverser fitted,

but on RAF aircraft, the two inboard

reversers have been inhibited

because the jet blast from all four

created too much buffeting

on the fin and elevator.

TARGET DOOR

TARGET DOOR

Thrust Reversers

Target Door Type

Normal Forward Thrust

Reverse Thrust

Used on


The Tornado
(illustrated)

This system does redirect

the jet thrust slightly forward,

witness the exhaust staining

on the aircraft fuselage and tail.

Thrust Reversers

Other Methods

Reversing the pitch of the

propeller blades, sends the thrust

in a totally forward direction.



Used on Hercules

REVERSE PITCH PROPELLER

Parachutes can be deployed which

increase the drag and increase the

deceleration of the aircraft.



Used on Vulcan

DROGUE PARACHUTE

Thrust Reversers

Translating Cowl Type

The Tri
-
Star and C17

Pivoting Door Type

The Sentinel R17

Clam Shell Door Type

The VC 10

Target Door Type

The Tornado

Thrust Reversers

Selection, Sequencing & Safety Features

There are two types of throttle mechanism.

The Hydro Mechanical Control System

and

The FADEC System

(Full Authority Digital Electronic Control)
.




Thrust Reversers

Selection, Sequencing & Safety Features

Electro/Hydro

Mechanical
Control System

Main
Throttle
Lever

Piggy
-
back
Lever

Reverse
Idle

Maximum
Reverse Thrust

Forward
Idle

Throttle
Cam

Maximum
Forward Thrust

Reverse thrust is controlled

by a mechanical cam,

fixed to the throttle assembly.

The throttle has to be

in the forward idle position

to select deployment,

via the piggy
-
back levers.

Lifting the piggy
-
back lever

moves the main throttle

rearwards,

deploying the reverser.



Thrust Reversers

Selection, Sequencing & Safety Features

FADEC Control System

Maximum
Reverse
Power

Select
Reverse
Thrust
Power

Reverse
Idle
Power

Select
Reverse
Deployment

Piggy
-
back
Lever

Main Throttle
Lever

Forward Idle
Power

Maximum
Forward Thrust

The FADEC System is similar

to the previous one.

With this system

reverse thrust

can be selected

at any time in the flight.

But the engine controller

should not allow deployment

unless certain conditions

are met ,

involving speed and RPM.

Check of Understanding

What is thrust reversing?

Driving the aircraft wheels backwards

Turning the engine to point
in the opposite direction

Making the engine shaft

rotate in the opposite direction

Redirecting the engine exhaust

in a forward direction

Thrust reversers generally fall into four types,

what are these types?

Transmission cowl, pilot doors,

crab shell doors and bucket doors

Translating cowl, balanced doors,
clamshell doors and target doors

Translating cowl, pivot doors,
clamshell doors and target doors

Transmission cowl, pilot doors,
clamshell doors and target doors

Check of Understanding

Check of Understanding

Which type of thrust reverser

is shown in the illustration?

Target door

Translating cowl

Pivot door

Clamshell door

How is thrust reverser deployment

commanded?

By command from the control tower

Automatically on landing

By engine power on touch down

By the pilot on landing

Check of Understanding

Check of Understanding

Which type of thrust reverser

is shown in the illustration?

Target door

Translating cowl

Pivot door

Clamshell door

Which of the following aircraft

use the pivoting door system?

Tristar

Tornado

VC 10

Sentinel R17

Check of Understanding

Which of the following systems

can be deployed in flight?

The drogue parachute

The pivoting door

The translating cowl

The clam shell door

Check of Understanding

Check of Understanding

Which type of thrust reverser

is shown in the illustration?

Target door

Pivot door

Clamshell door

Translating cowl

What is the common angle range

for redirecting the gas stream forwards?

25
o

to 75
o

45
o

to 90
o

45
o

to 75
o

25
o

to 60
o

Check of Understanding

Check of Understanding

Which type of thrust reverser

is shown in the illustration?

Target door

Pivot door

Clamshell door

Translating cowl

Which of the following aircraft

use the target door system?

Tristar

Tornado

Hercules

Vulcan

Check of Understanding

Which type of thrust reverser

is used by the Vulcan

Check of Understanding

Target door

Drogue parachute

Clamshell door

Reverse pitch propeller

Check of Understanding

Which type of thrust reverser

is shown in the illustration?

Target door

Pivot door

Clamshell door

Translating cowl

Reheat can be up to what percentage higher

than basic engine power?

90%

60%

80%

70%

Check of Understanding

JET PROPULSION

End of Presentation