Jaguar XJ (2008 year). Service manual — part 18

73

Occupant Protection

R

Air bag deployment

To do their life-saving job, air bags must
inflate rapidly and with considerable
force. There is therefore a risk of death or
serious injuries such as fractures, facial
and eye injuries or internal injuries,
particularly to occupants who are not
properly restrained by seat belts or sitting
correctly when the air bag deploys.

The risk of injury from a deploying air bag
is greatest close to the trim covering the
air bag.

The whole sequence of events from
sensing the impact to full inflation of the
bag takes place in a fraction of a second.

The noise and gas associated with the
deployment of the air bags is not injurious
to health.

After air bag deployment, it is normal to
notice a smoke-like, powdery residue or
smell the burnt propellant. This may
consist of cornstarch, talcum powder or
sodium compounds that result from the
combustion process that inflates the air
bag.

Small amounts of other chemicals may be
present which may irritate the skin and
eyes, but none of the residue is toxic.

While the system is designed to help
reduce serious injuries, it may also cause
minor burns, abrasions, swelling or
temporary hearing loss.

!

WARNING:

Safety experts recommend a minimum
distance of at least
254 mm (10 inches) between an
occupant's chest and a front air bag.

!

WARNING:

No objects whatsoever should be
attached to the centre cover of the
steering wheel, the passenger facia
panel, the sides of the front seats or the
interior trim immediately above the
door openings. Do not put anything on
or over the air bag inflation area.
Placing objects on or over the air bag
inflation area may cause those objects
to be propelled by the air bag into your
face and torso causing serious injury.

!

WARNING:

Do not try to put an adult seat belt
around two children.

!

WARNING:

Children 12 years old and younger can
be killed or seriously injured by the air
bag. The rear seat is the safest place
for children.

!

WARNING:

Several air bag system components
get hot after inflation. Do not touch
them after they have deployed.

!

WARNING:

If an air bag is inflated, the air bag will
not function again and must be
renewed immediately. If a new air bag
is not fitted, the unrepaired area will
increase the risk of injury in a collision.

Occupant Protection

74

L

Air bag deployment effects

!

WARNING:

When an air bag inflates a fine powder
is released. This is normal, and not an
indication of a malfunction. However,
the powder may cause irritation to the
skin, and should be throughly flushed
from eyes, and any cuts or abrasions.

!

WARNING:

After inflation some air bag
components are at high temperatures.
To prevent injury, do no touch the air
bag components until they have
cooled.

!

WARNING:

In order to react with sufficient speed,
air bags are deployed by an explosive
charge. Consequently air bag
deployment is accompanied by a very
loud noise which may cause
discomfort and temporary loss of
hearing.

Front protection

With a front impact of sufficient force, the
restraints system will trigger the front air
bag(s) and seat belt pretensioners, which
immediately tighten the seat belts.

For front occupants, the seat belt then
slackens with increasing chest load,
allowing the head and chest to more
gradually come into contact with the
inflated air bag. The air bag absorbs the
remaining energy of the impact and then
deflates rapidly via vent holes.

Front air bags are designed to inflate in
frontal and near-frontal collisions, not low
speed impacts, roll-over, side impact or
rear impact.

JAG0633

75

Occupant Protection

R

Side protection

The side protection system utilizes four air
bags: Two mounted in the front seats, and
two curtain air bags located just above
the front and rear door openings, under
the headlining trim.

When the seat mounted thorax and pelvis
air bag inflates upon a vehicle side
impact, it breaks through the seat bolster
stitching, protecting the side of the rib
cage and pelvis of the driver or front seat
passenger.

When the curtain air bag inflates upon a
vehicle side impact, it breaks through the
headlining and deploys downwards,
giving head protection to the front and
rear seat occupants on the impact side.

The curtain air bag on the front passenger
side is always deployed in a side impact
even if the front passenger air bags are
de-activated. This is to maintain
protection for a rear occupant.

Seat mounted thorax and curtain air bags
are designed to inflate in a side impact
collision, not roll-over, rear impact, frontal
or near-frontal collisions, unless the
collision causes sufficient lateral
deceleration.

The air bags, in combination with the seat
belts, can help reduce the risk of severe
injuries in the event of a significant side
impact collision.

Whiplash protection

Both front seats are equipped with Active
Head Restraints (AHR) which reduce the
risk of neck and spinal injury (whiplash) in
the event of a rear impact.
When activated, the head restraint moves
upwards and forwards, cushioning the
occupants’ head.

After activation, the whiplash protection
mechanism automatically resets and
does not require to be replaced.

JAG0813

Occupant Protection

76

L

!

WARNING:

For optimum protection, the driver and
passenger should sit in the centre of
the seat with the head as close as
possible to the head restraint.

!

WARNING:

Adjust the head restraint so that it is
just behind your head and never behind
your neck.

!

WARNING:

Do not wedge objects (e.g. luggage)
between the front seat backrest and
the rear seat cushion.

!

WARNING:

After a rear collision, the front seats
must be inspected by a Jaguar Dealer
even where there is no apparent
damage or change to the seat.

!

WARNING:

Do not attempt to service or tamper
with the seat recliner mechanism.

Occupancy sensing

The front passenger seat is monitored by
ultra-sonic sensors (shown above) and a
seat weight sensor to determine the
presence, weight and position of the front
passenger. In certain conditions, e.g.
where no passenger is present, the
appropriate air bags will be de-activated.
In a collision these air bags would not be
deployed.

The occupancy sensor operates as
follows:

Passenger
occupancy
status

Passenger
air bag
status

Indicator
lamp
active

Completely
empty

Deactivated

No*

Low weight
occupant/
object

Deactivated

Yes

Heavy
occupant/
object

Activated

No

Passenger
head too
close to air
bag door

Deactivated

Yes

JAG0635