ejection system in an airplane......!!! the technology

7/28/2019 Ejection system in an airplane......!!! The Technology

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Knowledge ofEjection Seat Systems


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Introduction

" Aviat ion in i tsel f is no t

inherent ly dangerous. But to an

even greater degree than thesea, i t is terr ib ly un forg iv ing o f

anycarelessness , incapac i ty, o rneglect"


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SAFETY CONSIDERATIONS

Human Behavior Considerations

Risk Involved - Confidence In Machine

Economical Considerations


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TYPES OF SAFTY SYSTEMS

ESCAPE SYSTEMS

EW

ECM

MAWS(MISSILE APPROACH WARNING

SYSTEM)

WEATHER RADAR

COLLISION AVOIDENCE


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TYPES OF ESCAPE SYSTEMS

Over Side Bail Out

Personal Chute Sys

Ejection Seat Sys

Jettisonable Nose Escape

Ejection Seat Capsule Escape

Ejectable Cockpit Capsule


6/70

NEED FOR ESCAPE AID SYS

At speeds of 400 km/h or more dynamic force of

air is very high (windblast)

Overcoming this force and abandoning aircraft not

possible

At such high speeds little time for manual actions

Also speed of aircraft is so high that chances of

collision between ejecting pilot and aircraft tail isvery high

High g forces immobilize aircrew

Thus development of ejection seats


7/70

EJECTION SEAT An ejection seat is a system designed to

rescue pilot or other crew of an aircraft

(usually military) in an emergency.

In most designs, seat is propelled out of

the aircraft by an explosive charge

carrying pilot with it


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Ejection seats are one of most complex

pieces of equipment on an aircraft, and

some consist of thousands of parts

Purpose of ejection seat : To lift pilot

straight out of aircraft to a safe

distance, then deploy a parachute toallow pilot to land safely on ground

EJECTION SEAT


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EJECTION SEAT

It is meant to save life of pilot

It must help pilot to clear aircraft

It must get stabilized in air

It must permit quick separation of pilot

from seat

Parachute must deploy at a set height


10/70

Ejection seats:

may be

gas powered

rocket powered

may remove:

a single seat

two seats

a complete module

EJECTION SEAT


11/70

Ejection-seat Terms Bucket - This is the lower part of

ejection seat that contains survival

equipment

Canopy - This is the clear cover that

encapsulates cockpit of some

planes; it is often seen on military

fighter jets

Recovery sequencer- This is

electronic device that controls

sequence of events during ejection

Drogue parachute - This small

parachute is deployed prior to main

parachute; it designed to slow

ejection seat after exiting aircraft


12/70

Ejection-seat Terms

Catapult - Most ejections are

initiated with this ballistic

cartridge

Rocket catapult - This is a

combination of a ballistic

catapult and an under seat rocket

unit Egress system - This refers to

the entire ejection system,

including seat ejection, canopy

jettisoning and emergency life-support equipment

Environmental sensor- This is an

electronic device that tracks the

airspeed and altitude of the seat.


13/70

Face curtain - Attached to the top of

seats, pilots pull this down to cover face

from debris. This curtain also holdspilot's head still during ejection

Underseat rocket - Some seats have a

rocket attached underneath to provideadditional lift after the catapult lifts the

crewmember out of the cockpit

Vernier rocket - Attached to a seat, this

rocket is mounted to the bottom of theseat and controls the seat's pitch

Zero-zero ejection - This is an ejection

on the ground when the aircraft is at

zero altitude and zero airspeed

Ejection-seat Terms


14/70

EJECTION SEAT- HISTORY First ejection seats were developed during

World War II by HEINKEL (Ger) and SAAB.

Early models were powered by

compressed airand first aircraft to be

fitted with such a system was theHEINKEL He 280 prototype JET ENGINE

FIGHTER in 1940

First live flight test of the Martin-Bakersystem took place on 24 July 1946, when

fitter Bernard Lynch ejected from a

METEOR MKIII JET


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Types of Acceleration

Linear Accelerationreflects a change of speed in

a straight line. This type of acceleration occursduring take-off, landing, or in level flight when a

throttle setting is changed.

Radial Accelerationis the result of a change in

direction such as when apilot performs a sharp

turn, pushes over into a dive, or pulls out of a

dive.

Angular Accelerationresults from a

simultaneous change in both speed and direction,

which happens in spins and climbing turns.


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F G


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g-Forces - Gx

Gx is described as force acting on body from

chest to back + Gx is experienced during take-off roll as

throttle is advanced.

This is force that pushes pilot back into seat

as aircraft accelerates.

Gx is described as force from back to

chest It is encountered during landing as throttle

is closed.

This force pushes the pilot forward into

shoulder strap.


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Gy - is a lateral forc e that acts fr om shou lder to shou lder,

It is encountered during aileron rolls. Aerobatic pilots routinely encounter this type of G force

and can still safely and precisely maneuver their aircraft.

Gz - is a g ravi tat ional force that is appl ied to the vert ical

axis of th e body.

+Gz(po sit iv e) . It is experienced from head to foot

This happenswhen a pilot pulls out of a dive or pulls into

an inside loop.

Gz (negative)travels from foot to head, and it is

experienced when a pilot pushes over into a dive.

g-Forces - Gy and Gz


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ESCAPE AID SYS: PHYSIOLOGICAL LIMITATIONS

Human body is a heterogeneous sys of solids,

liquids & viscous elastic components

Each component has different response to

acceleration forces

Hence max tolerance to g load dictated by

component most severely affected

Limits of accn load MAX OF 5 g IN FIRST 0.1 s of ejection

PEAK VALUE OF 25 g FOR 0.01 s

RATE OF CHANGE OF ACCN NOT TO EXCEED 300 g/s


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Factors which limit tolerance level

Magnitude of accn Rate of change of accn

Duration of high accn

Direction of accn - Linear accn imp because high magnitude:

may exceed skeletal structure limits

Air blast effect

Force directly proportional to square of vel

At 434 kts pr is 600 lbs/sq ft. Unprotected face canwithstand this pr only for very short pd. Tear in facial

tissues, numbing, etc will result



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High accn rate (say, 100g/s) even if acting for short time

(say, 0.1sec) in axial dirn can cause skeletal damage

Statistics

Total successful ejections in IAF - 171 (plus)

Spinal injury cases - 30%

Other injuries - 24.6%

Without injury - 45%

Success rate of ejection below 500 ft - 9%

Important aspects during ejection Pilots posture

Nature of seat, survival pack,

Wind blast

Seat stabilization



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Peak acceleration should not exceed 21 g

and that this peak should not be held forlonger than about 1/10th of a second

Onset, or rate of rise of g should not be

greater than 300 g per second

In sustaining this acceleration, the body

should be held in a position to ensure thatadjacent spinal vertebrae are square to each

other.



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To ensure that g came on relatively slowly and did not

exceed first two conditions, a two-cartridge gun was

designed, in which first cartridge started seat rising

smoothly and second cartridge was fired by flame when

uncovered by moving piston , building up pressure

gradually to maximum required

To cater for third condition, sitting posture in seat wasaltered by rearranging footrests and by adoption of face

screen method of firing seat

In this method, firing handle was positioned above

occupants head and attached to handle was a screen

which, when handle was pulled forward and downward,

completely covered occupants face. Advantage of scheme occupant automatically assumed correct attitude by straightening

his back and squaring up his spinal vertebrae,

Screen afforded protection to face from air blast as seat leftaircraft.


REQMT OF EJECTION SEAT


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Peak acceleration should not exceed 21 gand that this peak should not be held for

longer than about 1/10th of a second

Onset, or rate of rise of g should not begreater than 300 g per second

In sustaining this acceleration, the bodyshould be held in a position to ensure that

adjacent spinal vertebrae are square to

each other.

PHYSIOLOGICAL



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REQMT OF EJECTION SEAT Complete sequence should be automatic

Design sys should be safe through out fltenvelope of a/c

System should have very high reliability to

ensure crew confidence Size and wt of sys, in addn to thrust

consideration must meet limitation of cockpit

and allowable wt

Suitable auto restraint sys to ensure correct

posture of pilot

Avoid high accn

Economical


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Seat must be stable in airstream over its

entire speed range of op To avoid limb injuries due to wind blast at

high fwd speed seat must have effective leg

and arm restraint mechanism

Must have sensing devices to prevent untimely

seat-man separation and dply of parachute

Seat must cater for oxygen supply for high alt

ejection

Seat structure should have adequate strength

to withstand loads



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Escape sys should incorporate canopy

jettisoning sys with means for adequateseparation between seat and the canopy at all

speeds

Must clear pilot off airplane without entangling in

tail

Should be adjustable to cater for varying pilot

height

Should provide adequate comfort and mobility to

pilot during normal flying

Must be easy to service and maintain


HUMAN BEHAVIOUR


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HUMAN BEHAVIOUR

Emergency understood but too many choices to

decide

Once an emergency is perceived it is to be

evaluated

Various options evaluated

Decision taken as quickly as possible, more so

at lower alt.

Cases are on record, a pilot having declared an

emergency, took considerable time before

resorting to ejection.

HUMAN BEHAVIOUR


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HUMAN BEHAVIOUR

Recog of Emergency

Not an easy task

Control panel has a lot of instruments and gauges giving

various data

A continuous perception and integration of this info and a

precise manipulation imposes heavy stresses on pilots

Pilots attention may be concentrated on his task and

ignores warning signals Actual perception of emergency situation is delayed

That may prove to be critical in ejection


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HUMAN BEHAVIOUR

Selection of choice based on personal experience

Tendency to overcome a sit by adopting a familiar choice

rather than correct choice. (Knowledge Based Errors)

i.e. In event of eng flameout , ejection may be preferable at

times to relight


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HUMAN BEHAVIOUR

ZEAL TO SAVE

Pilot no doubt has great onus to save a/c

But once he decides to eject, he must completely give up

idea

In his strong motivation to ctrl a/c upto last moment, he

loses his life also

Also trying to manoeuvre a/c out of inhabited area willonly divert his concentration on overcoming emergency


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HUMAN BEHAVIOUR

Professional pride

Having known emergency and aware of drill to

overcome, a pilots ego interferes with quick

decision and action

This attitude is more with senior pilots who

have long experience on type of a/c

An overconfidence or complacency in his own

ability is one of causes of failure to eject

MECH MALFUNCTIONING


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This is involved in entire system and its

subassemblies

It may be a case of failure of

Canopy to open or

Main cartridge not firing or

Pilot could get entangled due to improper

strapping

A thorough servicing standards will only

reduce failures

MECH MALFUNCTIONING

HUMAN BEHAVIOUR


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FEAR OF UNKNOWN.

Pilot feels more comfortable in cockpit.

Due to poor indoctrination pilot is greatly biased

on not resorting to ejections where he hasmisapprehensions on cartridge firing, parachute

opening and ultimate location by rescue party.

Besides adm repercussions he has to face, he isworried that adm action is primarily meant to find

someone to blame rather than in fault finding.

HUMAN BEHAVIOUR

H i bilit


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Aircraft in Spin

Pilot is unable to recover from spin, or he may try toeject when Aircraft is spinning.

Carbon Monoxide Poisoning

When ac is on fire, gases enter cockpit that may leadto suffocation of pilot.

Disorientation

This phenomenon occurs usually in night flying orwhen pilot has to fly in clouds with no visible ground

marks for identification.

Human inability

H i bilit


36/70

Pilot in Panic

Fear and anxiety are main cause of faulty ejection

procedure

Poor estimation of time by pilot leading to redundant or

unnecessary actions.

Adverse G Loads

This occurs when aircraft is under heavy g loads.

Pilot is unable pull main firing handle and in choosing to

pull alternate firing handle, he may omit certain basic

precautions.

G LOC

Pilot Incapacitated

This may be due to bullet hits under enemy fire or bird hit

or canopy inadvertently opening there by exposing pilot to

intense air blast.

Human inability

Measures to reduce ejection failures


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Measures to reduce ejection failuresA review of the ejections reveals that human factor is responsible for

50% of unsuccessful ejections. It is also obs that chances of

successful ejection below 500 ft is only 9%. Following measures will

improve rate of success

Conditioning of aircrew for early ejection. Each case is unique in itself.

It must be realised that if a/c is crippled its loss is inevitable, but not

that of pilot. It is purely prevailing cockpit conditions (of which the pilot

is best judge) that decides issue. Hence early decision is required.Man vs machine aspects. Each a/c system has its own way of rescuing

pilot. Seat is last resort, that too under most adverse conditions, hence

it must be fully reliable, easily maint and simple in ops. System can be

maint by thorough service standards. Suitable mods can be made if

need be, with knowledge of past cases of ejection.

A better educative programme. Pilot must have sound practice on

correct ejection drill. A realistic ejection trg can be given in a suitable

rig, at regular intervals. Repetition of same sequence of acts makes

response pattern relatively permanent.

Modes of operation


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Modes of operation

Modes of operation


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Modes of operationMode 1 operation

Low Speed Low altitude

Very critical

Time available very less

Main parachute deployed

imdlyMode 2 operation

High speed

Main parachute may break

Drogue deployed imdt

Speed reduced before

depy of main parachute

Modes of operation


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Mode 3 operation

High altitude ejection

Drogue deployed to

stabilize seat

Main deployed only after

reaching 1000ft

Event

Time

Sequence

Modes of operation


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PARTS OF

EJECTION SEAT
http://www.martin-baker.com/getdoc/19158240-fcfb-41f5-b294-bb1f72bd7264/Type-US16LA-JPATS_popup.aspx


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http://www.martin-baker.com/getdoc/19158240-fcfb-41f5-b294-bb1f72bd7264/Type-US16LA-JPATS_popup.aspx


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DROGUE GUN


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This line has attachment points on both sides of

headrest which pull out a pair of clips. These clips

release face curtain and parachute box retaining lines.

Then the chute extraction line pulls out the main chuterip cord pins allowing pack opening spring to force

flaps of parachute box open and launch parachute out

to inflate.

Drag from parachute overcomes friction of rest of

connections between the crewmember and seat(all the'hard' connections are released by the TRM) and pulls

the crewmember off the seat.

Parts such as the parachute container box, face curtain

and overhead handle, and parachute box retaining

straps, as well as seat itself continue on their merryway towards ground

DROGUE GUN

DROGUE GUN


45/70

It is designed with a simple clockwork to fire

after a second or two of delay from first seat

motion to allow seat to clear structure andmake sure drogue could be launched into

clear air.

After delay, drogue gun fires a slug of metal

that weighs about one pound into air with acartridge. This physically, and violently rips

drogue chute from its pack in headrest.

Drogue chute inflates rapidly and slows seats

forward motion, while stabilizing it vertically.

Once TRM functions, drogue shackle which is

attached to drogue chute lines is freed and

pulls the main chute extraction line.

DROGUE GUN

Ejection Gun and Guide Rail


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j

Assembly


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Time Release Mechanism (TRM
http://www.ejectionsite.com/ejctpic/mk5trm.jpghttp://www.ejectionsite.com/ejctpic/mk5trm.jpg


49/70

TRM was designed to do several functions in

two simple co-joined motions. It also functions

with a basic clock mechanism that also has a

short delay initiated by a trip rod attached tocockpit bulkhead second delay in it

This timer can be delayed by two possible

mechanisms. One is a simple weight and

spring mechanism that prevents it from

functioning while the seat is decelerating too

rapidly. In other words in a high speed ejection

the timer delays activation for a fraction of

time while the seat slows slightly.

Then barostat inhibiter comes into play.Barostat is mounted on side of unit and by

pressure differential determines if seat is

above a preset altitude such as 10000 feet.

This is to prevent seat separation to allow

crewmember to descend to a warm, thicker

atmosphere.

(

Time Release Mechanism (TRM
http://www.ejectionsite.com/ejctpic/mk5trm.jpghttp://www.ejectionsite.com/ejctpic/mk5trm.jpghttp://www.ejectionsite.com/ejctpic/mk5trm.jpg


50/70

Then clockwork timer begins to work.

Upon its expiration, strong springs drive a

rod in the downward direction. Top portion

retracts to release a 'scissor shackle'

which releases drogue shackle and allows

it to do its job.

Lower end drives downward and releases

by means of a torque tube inertial reel

harness

It also by a set of turnbuckle like links on

torque tube releases seat kit and harness

connections for lap belt as well as LEG

RESTRAINERS

(

Barostatic Time Release Unit Barostatic Time Release Unit
http://www.ejectionsite.com/ejctpic/mk5trm.jpghttp://www.ejectionsite.com/ejctpic/mk5trm.jpg


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2- DROGUE GUN 3- EJECTION GUN


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2 DROGUE GUN 3 EJECTION GUN

WORKING OF EJECTION GUN


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54/70


Canopy Jettison


55/70

Canopy Jettison

Canopy jettison equipment consisted of

a unit bolted to rear of ejection seatguide rail and containing a canopy

jettison breech, together with a one

second delay mechanism.

On pulling ejection seat firing handlesear of canopy jettison gun was

withdrawn, cartridge detonated and

gases passed through piping to the two

canopy jettison jacks.

Expanding gases forced pistons of

jacks upward, first operating canopy

locks and then raising canopy for

airstream to carry it clear of aircraft.

Canopy Jettison


56/70

Canopy Jettison

Under certain, it was possible canopy

might not leave aircraft cleanly, eventhough it had been unlocked.

This could give rise to ejected seat

colliding with canopy and becoming

entangled with it. By providing an explosive canopy

jettison system powerful enough to

force canopy clear under all

conditions, and by linking itsoperation to ejection seat firing

handle,

DROGUE& MAIN PARACHUTES


57/70

SNUBBING UNIT & RESTRAINT MECHANISM


58/70

SEQUENCE OF OPERATION


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Pre-ejection

Pilot Leaving Aircraft

Seat Stabilization and Pilot leaving

seat Deployment of Main Parachute,

safe Descent and landing



60/70

SEQUENCE OF OPERATION Pilot recognizes emergency

Weighs his options and Decides to eject

Pulls firing handle

Harness power retraction sys operates

(Pilot in correct position for ejection)

Canopy jettisoning gun fires next Ejection gun fires after a delay of approx 0.3 s

Seat ascends rails, occupants leg pulled back

Seat-a/c connections separated, drogue gun &BTRU sears withdrawn

Emergency oxy sys and IFF txn automaticallyswitched on in emergency mode

Leg restraint end rivets snap free



61/70

If canopy jettisoning fails, canopy breakers fitted on seatwill break canopy for through canopy ejection

Further movement of seat through static lines will initiateremote rocket pack which will augment upward thrustinitially generated by ejection gun

After a predetermined delay drogue gun fires andcontroller drogue is dply which in turn pulls out and dplymain drogue, reducing fwd speed and stabilizing seat

When ejection takes place above 6000 m a steadied free

fall occurs At 6000 m BTRU op and after a delay of approx 2.0 s

drogues, leg lines and harness are released from seat

As drogue is pulled away it draws and dply main

parachute and pilot safely descends onto ground --CONTD


OPERATING SEQUENCE OF Mk.4 SEAT


62/70

1-Preparing to eject 2. -Face screen pulled to commence

ejection sequence

Q



63/70

3- Canopy jettisoned

Q



64/70

4- Seat commences to eject, legs retracted, sear withdrawn from drogue gun.

5- Simultaneously the firing pin is withdrawn from time-release unit.

6- Half a second after ejection the drogue gun fires and the piston is ejected.

7- The line attached to the piston withdraws the drogues from the container.



65/70

8- Stabilize seat and reduce its

forward speed9- When below 10,000 ft. and speed

reduc ed su ff iciently, time-release unito erates and scis so r shackle o ens.



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10- Pul l of drogues is transferred to

l i f t ing l ines and face screen andarachu te are released from s eat.

11- The combined harness and leg

cords are released from the seat.



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12- Drogues deploy parachute occupant

is lifted out of seat, seat falls freely.

13- Occupant makes a normal

parachute descent



68/70

6

5

4

3 2

1

7

FIRING HANDLE PULLED

HARNESS POWER RETRACT

SYS OP

PILOT POSTURE CORRECTED

CANOPY JETTISONING GUN

FIRES

EJECTION GUN FIRES

SEAT ASCENDS ON RAILS

LEG RESTRAINTS OP

DROGUE GUN & BTRU

SEARS WITHDRAWN

EMERGENCY OXY & IFF OP

LEG RESTRAINT CORD END

RIVETS SNAP FREE

IF CANOPY JETTISONING

NOT OP BREAKERS COME

INTO PLAY

ROCKET PACK INITIATED

DROGUE GUN FIRES CONTROLLER DROGUE

DPLY

SEAT STABILISATION

STARTS

CONTROLLER DROGUE PULLS

OUT MAIN DROGUE

FWD VEL ARRESTED SEAT STABILISED

AT 6000 M BTRU OP

LEG LINES, HARNESS &

DROGUE LINES RELEASED

FROM SHACKLE SEAT-MAN SEPARATION

MAIN PARACHUTE DRAWN

OUT


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CONCLUSION


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ejection system in an airplane......!!! the technology

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