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PIA TRAINING CENTRE (PTC)
Module 7 - MAINTENANCE PRACTICES
Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
MODULE 7
Sub Module 7.17
AIRCRAFT HANDLING AND STORAGE
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17
For Training Purpose Only
Rev. 00
Mar 2014
PIA TRAINING CENTRE (PTC)
Category – A/B1
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
Contents
AIRCRAFT HANDLING AND STORAGE .................................. 1
MOVING METHODS................................................................. 2
AIRCRAFT TOWING ................................................................ 2
AIRCRAFT TAXIING ................................................................. 2
PRECAUTIONS WHEN TOWING / TAXING AIRCRAFT .......... 3
AIRCRAFT JACKING................................................................ 4
JACKING PRECAUTIONS ........................................................ 7
PARKING AND MOORING AIRCRAFT .................................. 11
CHOCKING OF AIRCRAFT .................................................... 15
AIRCRAFT STORAGE............................................................ 16
AIRCRAFT FUELLING PROCEDURES .................................. 20
DEFUELLING ......................................................................... 22
DE-ICING/ANTI-ICING OF AIRCRAFT ................................... 23
GROUND ELECTRICAL SUPPLIES ....................................... 31
GROUND HYDRAULIC SUPPLIES ........................................ 33
GROUND PNEUMATIC SUPPLIES ........................................ 34
EFFECTS OF ENVIRONMENTAL CONDITIONS ON
AIRCRAFT HANDLING AND OPERATION ............................ 35
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - i
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PIA TRAINING CENTRE (PTC)
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AIRCRAFT HANDLING AND STORAGE
Aircraft need to be moved on the ground, between flights, for a
variety of reasons, which can include:



Moving aircraft into, or within hangars for maintenance
Re-positioning aircraft for ground running or storm protection
Emergency removal of aircraft from a taxi-way.
It is important that the aircraft be moved safely, using the
correct equipment, to avoid injury to personnel or damage to
aircraft. Small aircraft, generally require little preparation but,
with larger aircraft, some or all of the following points may be
relevant:
Preparation for the reception of the aircraft should be made in
advance of its arrival. There should be adequate space
available for the aircraft, with consideration given, as
appropriate, to clearances for jacking, access for cranes etc. All
equipment required for servicing should be available and
serviceable.
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
The members of the moving team should be fully conversant
with their assigned tasks. The person controlling the move
should adequately brief them all, as to their individual
responsibilities. This applies equally to the re-positioning a light
aircraft in a hangar or to the moving of a giant airliner around a
large, international airport.
The equipment and method of move should be as stated in the
relevant aircraft maintenance manual.
All towing limitations should be observed. These should be
stated in the maintenance manual under "Ground Handling".
Examples of limitations include minimum turning radii and
disconnection of nose-wheel steering system on certain aircraft.
Clearance from the local Air Traffic Control may be required for
the move.
The aircraft should be in a satisfactory condition to move. The
brakes should be serviceable and electrical power should be
available, if required, for lights and indications in dark or poor
light.
The route of the proposed move should be free from
obstructions, such as servicing platforms, passenger steps,
vehicles and any other servicing equipment. Consideration
should also be given to sources of F.O.D. along the route.
ISO 9001:2008 Certified
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7.17 - 1
For Training Purpose Only
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PIA TRAINING CENTRE (PTC)
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
MOVING METHODS
AIRCRAFT TAXIING
Normal moving methods of moving aircraft on the ground are by
means of:
When aircraft are to be moved under their own power, whether
for ground movements or prior to flight, a fully certified flight
crew must be on the flight deck and in command of the aircraft.
It is usual for the aircraft to have received a daily inspection
before the taxi operation, which ensures items such the oil and
fuel levels and brake pressures are sufficient for the task.



Hand: by pushing and using a steering arm
Tractor: using a bridle and steering arm or with a purposemade towing arm
Taxiing: moving the aircraft, using its own power.
When an aircraft has to be moved from one place to another,
either by man-handling, by the use of a tractor (also called a
towing ‘tug’) or by taxiing, there are a number of safety
precautions which have to be applied every time.
AIRCRAFT TOWING
This is the normal method used on large aircraft. The aircraft is
normally towed with a suitable tractor (or tug) and using the
correct, purpose-made towing arm for the specific aircraft. A
person familiar with, and authorised to operate, the aircraft
brake system should be seated in the cockpit (or on the flight
deck) to apply the brakes in an emergency. The brakes should
not normally be applied unless the aircraft is stationary.
The relevant maintenance manual will normally specify details
of the towing arm and any limitations on the towing procedure.
On many aircraft with nose-wheel steering, it is normal practice
to disconnect or depressurise the aircraft steering system
before towing.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 2
It will be necessary for a ‘Starter Crew’ to be present before
engine starting. This crew should include a supervisor (who will
be in visual and/or verbal communication with the aircraft crew),
a fireman with a suitable extinguisher and a tractor driver to pull
any ground power unit clear after engine starting.
Once the aircraft is moving under its own power, the flight crew
has responsibility for the safety of the aircraft. The ground team
should give assistance to the crew, via the intercom and/or
standard marshalling hand signals (refer again to the ‘FlightLine Safety’ section of the earlier Safety Precautions topic), until
the flight crew no longer require their services.
When approaching its parking spot, providing it is not using the
automatic parking indicating system, found on many parking
stands, the pilot may be dependent upon the ground team for
clearance indications and stopping cues.
Once stopped, the aircraft wheels must be chocked, given
ground power, if required, and generally taken control of, by the
engineers, prior to its next maintenance procedure.
For Training Purpose Only
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PIA TRAINING CENTRE (PTC)
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
PRECAUTIONS WHEN TOWING / TAXING AIRCRAFT
Towing speed should be kept to a safe level at all times
(walking pace is a safe limit).
A steering limit is often imposed, so that the radii of turns are
kept within specified limits, thus minimising tyre scrubbing and
reducing the twisting loads on the undercarriage. It is usual to
tow the aircraft forwards in a straight line after executing a turn,
in order to relieve stresses built up in the turn. The steering limit
is often shown by marks painted on the fixed part of the nose
leg, but may, sometimes, be overcome by the disconnection of
a pin, joining the torque links.
Suitably briefed personnel should be positioned at the wing tips
and tail when manoeuvring in or around confined spaces, so
that obstructions may be avoided.
Large, multi-engined aircraft will usually be towed with specialpurpose tug and a suitable towing arm that includes a shear pin,
designed to shear if a pre-determined towing load is exceeded.
In an emergency it may be necessary to move an aircraft from
the runway if it has one or more deflated tyres. Provided there is
one sound tyre on the axle the aircraft may be towed to the
maintenance area, but sharp turns must be avoided and towing
speed kept to a minimum.
If there are no sound tyres on an axle, the aircraft should only
be moved the shortest distance in order to clear an active
runway and serviceable wheels should be provided before
towing. After any tyre failure, the associated wheel and other
wheels on the same axle should be inspected for signs of
damage.
One person shall be supervising the aircraft movement (NOT
the tractor driver) and should be positioned so that all members
of the team can be observed.
Particular care should be given, when towing swept wing
aircraft, to "wing tip growth". This is the tendency of the swept
wing to "grow" in a turn and was discussed in ‘Flight-Line
Safety’, which is contained in the early topic concerning Safety
Precautions.
Before commencing the towing operation, the brake system
should be checked and the brake accumulator charged as
necessary. Brake pressure should be carefully monitored during
the move.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 3
For Training Purpose Only
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PIA TRAINING CENTRE (PTC)
Module 7 - MAINTENANCE PRACTICES
Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
AIRCRAFT JACKING
Aircraft may need to be jacked for a variety of purposes. These
may include component changes, retraction tests, weighing of
the aircraft and aircraft rigging checks. Care needs to be taken
when jacking, to avoid damage to aircraft or equipment.
Jacking points are provided in the wings and fuselage, at strong
points, to enable the whole aircraft to be lifted, and there are,
usually, other points, at the nose and main undercarriages, to
enable individual wheels to be changed (refer to Fig. 1).
Some aircraft require a jacking pad to be fitted to each jacking
point, while in some, the jacking pads are built into the structure.
Special jacking adapters and beams may be available to lift
individual axles.
Nose Jacking
Point (Offset)
Main Jacking
Points
In all instances, the Maintenance Manual should be consulted,
so that the correct equipment and procedures may be used.
Special Considerations
Because of the position of the jacking points, the C.G. of some
aircraft may be well behind, or in front of, the main jacking
points. It may be necessary to add ballast forward or rear of the
jacking points or to check the fuel load of the aircraft, to bring
the centre of gravity within safe limits as specified in the
Maintenance Manual.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 4
Nose Jacking
Point (Offset)
Typical Jacking Points
Fig.1
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PIA TRAINING CENTRE (PTC)
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Each jacking point may have a load limit which, if exceeded,
could result in structural damage. To avoid exceeding this limit it
may be necessary to install hydraulic or electric load cells. Any
special requirements should be listed in the Maintenance
Manual.
Micro-switches, attached to the undercarriage legs, and
operated by the extension of the shock absorbers (weight-on
switches), are used to operate various electrical circuits, This
operation may not be desirable, so circuits should be isolated,
by tripping circuit breakers or removing fuses as necessary.
Aircraft should always be as structurally complete as possible
before jacking, It is essential that any stressed panels which
have been removed are re-installed.
Failure to do this may result in distortion or failure of the
structure.
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
The Pillar hydraulic jack consists of a cylinder assembly, a fluid
container and a hydraulic pump which, when operated, forces
fluid from the container into the cylinder
and raises the ram. A release valve is provided which, when
opened, causes the fluid in the cylinder to return to the
container and the ram to descend.
Because of possible hydraulic failure, some jacks are provided
with a mechanical locking collar which, when wound down, will
prevent the jack from lowering. An air/filler valve, which vents
the return side to atmosphere, may also be provided. This
should always be open when the jack is operated.
Bipod, Tripod and Quadrupod jacks are used, to raise an
aircraft for various servicing operations. Their methods of
operation and hydraulic mechanisms are similar to the pillar
jack. They consist of a hydraulic unit, supported by the relevant
number of legs (two, three or four).
Aircraft jacks
Aircraft jacks are intended for raising and lowering loads and
should not be used for supporting the loads for long periods.
Where a load must remain raised for a long period, it should be
supported on blocks or trestles after it has been jacked to the
required height. The most common types of aircraft jacks are
the pillar, trolley, bipod, tripod and the quadrupod hydraulic
jacks. There are several sizes of jacks, with capacities ranging
from 4000 kg and greater.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 5
Because of the problems involved in raising an aircraft and to
avoid injury to personnel or damage to the aircraft, care should
be taken to use the correct type of jack as stated in the
Maintenance Manual. Each jack should be used with the correct
adapter head.
The tripod jack comprises a hydraulic unit with three equally
spaced legs. The jack is designed for a vertical lift only and not
for a lift involving lateral movement of the jack (such as when
raising one side of the aircraft for a wheel change).
For Training Purpose Only
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PIA TRAINING CENTRE (PTC)
Category – A/B1
The resulting side thrust may cause any one of the following:





Serious damage to the ram, due to the bending load
Distortion of the jack legs
Damage to the aircraft, due to the .jack head slipping
out of the jacking pad
Shearing of the jacking pad fastener
Dragging sideways of the serviceable tyre.
To change a single wheel, a pillar jack may be used, while two
tripod jacks may be used to raise the complete aircraft (or a
bipod jack may be used). The bipod arrangement overcomes
the limitations of the tripod jack for an 'arc' lift. On this type of
jack, two fixed legs provide the support and a third, trailing leg,
follows the lift and steadies the load during the lift. The
maximum angle of arc should not be more than 6º.
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
Jack Maintenance and General Notes
Aircraft jacks should always be positioned correctly and the load
raised and lowered gradually.
All jacks should be stored in the fully retracted position, kept
clean and free from corrosion. Moving parts should be
lubricated regularly and the jack should be exercised if it is not
used frequently.
Jack replenishment is usually through the air valve, up to the
level of the bottom of the air valve. Low oil level is indicated by
inability to lift to maximum height, whilst over-filling is indicated
by leakage of oil when the jack is fully extended.
The quadruped jack is used more commonly as it possesses
the advantages of both types of jack. Two legs are fixed and
two are adjustable. This jack may be used as a bipod jack, by
removing the adjustable legs, or as an adjustable, stable jack
with one extra leg added. All four legs may be locked solid, by
slight adjustment of both adjustable legs.
Transportation wheels are often permanently attached to some
jacks while they may be provided as detachable units on other
jacks. The wheels facilitate easy movement of the jacks that
would otherwise need to be dragged around the hangar. Jacks,
alternatively, can be dismantled for easier transportation.
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PTC/CM/B1.1 Basic/M7/04
7.17 - 6
For Training Purpose Only
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PIA TRAINING CENTRE (PTC)
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
JACKING PRECAUTIONS
As a safety precaution, small aircraft should normally be jacked
inside a hangar.
Larger aircraft may be jacked outside, provided they are
positioned nose into wind; the jacking surface is level and
strong enough to support the weight, and that any special
instructions, stated in the Maintenance Manual, are observed.
A maximum wind speed, stated for jacking outside, can also be
found within the Maintenance Manual. The aircraft to be jacked
should be chocked fore and aft and the brakes positioned to
OFF (brakes released). If the brakes are inadvertently left in the
ON position (brakes applied) stress could be introduced to the
landing gear or to the aircraft structure, due to weight redistribution as the aircraft is raised.
Checks should be made on the aircraft weight, its fuel state, and
centre of gravity, to ensure they are within the specified limits as
detailed in the Maintenance Manual. The aircraft should be
headed into wind (if it is in the open), the main wheels chocked
fore and aft, the brakes released and the undercarriage ground
locks installed.
It is vital that the earth cable be connect to the earth point on
the aircraft and it must be ensured that there is adequate
clearance above every part of the aircraft and that there is
clearance for lifting cranes or other equipment, which may be
required.
Jacking pads should be attached to the jacking points and
adapters provided for the jacks as required. Load cells may also
be included if needed.
Jacking Procedures
While the following procedures will, generally, ensure safe and
satisfactory jacking of most aircraft, precedence must always be
given to the procedures and precautions specified in the
relevant Maintenance Manual.
The jacks should be positioned at each jacking point and
checks made, to confirm that the jacks are adjusted correctly
(i.e. release valve closed, jack body vertical, weight evenly
distributed about the legs when the adapters are located
centrally in the jacking pads, and the weight of the aircraft is just
being taken by the jacks).
One person should co-ordinate the operation and one person
should control each jacking point. On larger aircraft a levelling
station will also need to be monitored and all members of the
team may need to be in radio or telephone communication with
the co-ordinator.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 7
For Training Purpose Only
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PIA TRAINING CENTRE (PTC)
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
Before jacking commences, the chocks must be removed and
then the aircraft should be raised slowly and as evenly as
possible. Whilst jacking is in progress, the locking collars should
be continually wound down, keeping them close to the body of
the jack. When the aircraft is raised to the correct height, the
locking collar should be fully tightened down.
The ‘Universal’ trestle is made up from lengths of angle iron,
bolts and nuts, and has two jacking heads. By using different
lengths of angle iron, trestles of various sizes can be produced.
The wooden beam across the jacking heads may be replaced
by a wooden former, which is cut to the curvature of the
component it supports.
When jacking is complete, then supports may be placed under
the wings and fuselage as indicated in the Maintenance manual.
Padding is normally attached to the former, to prevent damage
to the aircraft finish. The two jacking heads, which are handoperated screw jacks, enable the beam to be adjusted to suit
the angle of the component.
Note: As previously stated, a pillar (bottle) jack and an adapter
are often used for raising a single undercarriage for changing a
single wheel. Alternatively a trolley jack or stirrup jack may be
used. The remaining wheels should be checked to prevent
aircraft movement, and it may be specified that a tail support be
located when raising a nose undercarriage. The jack should be
raised only enough to lift the unserviceable wheel clear of the
ground.
Trestles
These are provided to support to aircraft structures (main
planes, fuselages etc.) and may also be used to support the
complete aircraft. Various types are available including plain
wooden trestles that are purpose-built and not adjustable.
Trestles should only be used at designated strong parts of the
structure. It will normally be shown in the Maintenance Manual
where they should be positioned. Lines are often painted on the
aircraft to show where the trestle beam is positioned.
ISO 9001:2008 Certified
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7.17 - 8
Although the trestles have ‘jacking heads’, they should only be
used for supporting a load, and not for attempting to raise parts
of the aircraft. Damage may be caused to the aircraft if attempts
are made to do any more than support the structure.
The ‘Tail’ trestle is not suitable for heavy loads and must only be
used for supporting a load vertically. Adjustment in height is
made by a screw thread. In the same manner as a universal
trestle, the beam can be made in the same shape as the
contour of the aircraft.
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PIA TRAINING CENTRE (PTC)
Module 7 - MAINTENANCE PRACTICES
Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
Lowering Aircraft off Jacks
Slinging
Before lowering the aircraft to the ground, all equipment,
trestles, work stands etc. should be moved clear of the aircraft,
to prevent collision or contact with the aircraft structure. The
wheels should be rotated by hand, to ensure the brakes are off.
The jacks should be lowered together, by opening their
respective release valves, and the locking collars (if used)
unscrewed (but kept close to the jack body), whilst the jacks are
lowered. The jacks should be fully lowered after the aircraft is
resting on its wheels and the release valves then closed.
Slings may be required for lifting various parts of an aircraft
during maintenance, repair, dismantling and assembly.
Sometimes a complete aircraft may need to be lifted for
transportation or to clear a runway quickly.
On no account should the top of the jacks be handled until the
jack is clear of the aircraft. It is common for the aircraft shock
absorbers to stick and to suddenly collapse, resulting in damage
to equipment or serious injury to parts that might be between
the aircraft and jack.
After the aircraft is lowered and the jacks removed, the jacking
pads and adapters should be removed and the chocks placed in
position.
Any fuses or circuit breakers should be re-set in their correct
position.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 9
The use of the correct equipment for lifting aircraft parts will
minimise the risk of damage to the aircraft and personnel. A list
of special equipment is usually in the front of the Maintenance
Manual. This list will usually include special slings to be used on
the aircraft and any other special equipment or tools required.
Slings may be of the three-point type, as used for lifting-main
planes, while other types, used for lifting engines, fuselages or
other large items may be provided with spreader bars or struts.
Before removing a main plane, the opposite main plane must be
supported with trestles. To attach a sling, some aircraft have
special slinging points with threaded holes in the airframe,
which are used to accommodate the eye or fork-end bolts of the
sling. These holes are normally sealed, with removable plugs,
when not in use. As an alternative to screw-in devices, some
slings are used in conjunction with strong straps that pass under
the component to be lifted.
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Lifting Tackle
The following is a list of safety precautions that must be used
when using lifting tackle:








Do not exceed the safe working load of the lifting devices
Do not leave a suspended load unattended at any time
Do not walk or work under a suspended load
Do not tow the hoist at greater than walking pace
Do not tow the hoist, other than by hand, when a load is
suspended from the lifting hook
Do not allow the load to swing, especially when it is being
hand-towed
Do not using a hoist or crane on soft ground
Do not use a crane or hoist if the lifting tackle shows signs of
damage.
Wire rope, chain or fibre rope may be used for lifting purposes.
Before use, the tackle should be inspected to ensure that it is
serviceable, is of the correct type and, when used, that the Safe
Working Load (SWL) is not exceeded. The SWL should be
stated on an identification plate, attached to the lifting sling, and
should never be removed from the sling.
Wire Rope is used with cranes, hoists, gantries and various
slings. Before use, the wire rope, splices and attachments
should be inspected for damage such as wear, corrosion and
broken wires.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 10
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
In use, care should be taken that the rope does not kink under
load. Before multiple leg wire rope slings are used, they should
be laid out on the floor to ensure shackles are correctly attached
and the fittings are not twisted. Knotting of ropes, to shorten
them, is prohibited.
Wire rope slings may be treated against corrosion by immersion
in oil and the surplus oil wiped off, but this treatment must not
be applied to slings used for oxygen cylinders. They must
always be free from oil or grease.
Chains are used with cranes and various types of sling. Before
use, all chains must be inspected for damage such as cracks,
distortion, excessive wear and ‘socketing’.
Socketing is the name given to the grooves, produced in the
ends of links, when the links wear against each other. Any
reduction in diameter will render the chain unserviceable.
Fibre rope slings may be used for lifting lighter components, and
are made from natural fibres such as sisal, hemp or nylon
fibres. They must be inspected for frayed strands, pulled
splices, excessive wear and deterioration.
When not in use, fibre rope slings should be hung on pegs, in a
sheltered position, and free from dampness. Immediately before
use, the rope should be opened up, by slightly untwisting the
strands, to ensure they are not damaged or mildewed internally.
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A damaged or mildewed fibre rope sling should not be used,
and it must be destroyed, by cutting into small, unusable
sections, before final disposal.
In addition to before-use checks on the rope, all loaded
components such as pulley blocks, shackles, pins, spreader
bars and hooks are to be inspected for excessive wear, cracks
and flaws. Moving parts must be lubricated periodically.
PARKING AND MOORING AIRCRAFT
When an aircraft is out of service and in the open it should be
secured against inadvertent movement and protected against
adverse weather conditions. The operations recommended in
the relevant Maintenance Manual depend on the type of aircraft,
the length of time it will be out of service and the prevailing or
forecast weather conditions.
Parking
Between flights it is usually sufficient to apply the parking
brakes, lock the control surfaces and chock the wheels but, in a
strong wind, light aircraft should be headed into the wind. Light
aircraft without wheel brakes should be headed into wind and
their wheels chocked front and rear.
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
A more positive method entails the use of external control
surface locks that prevent control surface movement and, thus,
prevent strain on the control system. All external locks should
have suitable streamers attached, to make them more visible.
If an aircraft is to be parked overnight or for longer periods in
the open, then additional precautions should be taken, to guard
against the effects of adverse weather.
The undercarriage ground locks should be fitted, and all
openings, such as static vents, engine and cooling air intakes,
should be blanked, to prevent ingress of dirt, birds, insects and
moisture. Items such as pitot head and incidence indicators
should also be covered.
When severe weather is anticipated it is recommended that
covers for cockpit, canopy and wheel are fitted if available.
Blanks and covers should not be left in position when the
aircraft is prepared for service. Servicing instructions should
include a pre-flight check to ensure that all covers etc, are
removed.
Flying controls, on many aircraft, are locked by movement of a
lever in the cockpit/cabin. The lever is connected to locking pins
at convenient positions in the control runs or at the control
surfaces. When this type of control lock is not provided, locking
attachments may have to be fitted to the control column and
rudder pedals.
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Module 7 - MAINTENANCE PRACTICES
Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
Mooring (Picketing)
In certain weather conditions, particular in high winds, it would
be recommended that the aircraft be parked in a hangar. If they
must be left outside, then smaller aircraft may need to be tied
down. The aircraft may be provided with picketing rings or
attachment points at the wings and tail or adjacent to the
undercarriage legs (refer to Fig. 2).
A
B
C
View A
View B
View C
Aircraft Picketing Points
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If outside, the aircraft should always be parked nose into wind
and secured, from the picketing points to suitable ground
anchor points such as heavy concrete blocks or specialised
screw pickets.
Cable or nylon rope of adequate strength should be used where
possible but, if a natural fibre rope is used (sisal or hemp), then
sufficient slack must be left to allow for shrinkage in damp
conditions.
Additional picketing from the undercarriage legs may be
recommended in strong winds and, if so, care should be taken
not to damage any pipelines or equipment attached to the legs
or wheels.
Typical Small Aircraft Procedures
When mooring small aircraft in the open, the aircraft, if possible,
should be parked head into the wind. The control surfaces
should be secured with the internal control lock and the brakes
applied.
Care must, however, be exercised in extremely cold weather
and parking brakes must not be set if there is a danger that
accumulated moisture may freeze the brakes. Another danger,
in cold weather, exists when the brakes are overheated,
because, if they are set in this condition, serious distortion and
cracking of the brake (and wheel) components can occur as
they cool down.
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
Ropes, cables, or chains should be attached to the wing
mooring (tie-down) points, and their opposite ends secured to
ground anchors. A tie down rope (no chains or cables) should
be fastened to the exposed portion of the engine mount and the
opposite end of the rope also secured to a ground anchor.
The middle of a rope should be attached to the tail tie-down ring
and each end of the rope pulled, at a 45º angle, and secured to
a ground tie-down point either side of the tail.
A control lock should be applied to the pilot’s control column. If
a control lock is not available, then the control may be tied back
with a front seat belt.
These aircraft are usually equipped with a spring-loaded
steering system that affords protection against normal wind
gusts. However, if extremely high winds are anticipated,
additional external locks may be installed.
Large Aircraft Procedures
These may only require picketing in very strong wind conditions.
The maximum wind-speed will normally be stated in the
Maintenance Manual (including gusting winds). The aircraft
should be headed into wind and the parking brakes applied.
For Training Purpose Only
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Mar 2014
PIA TRAINING CENTRE (PTC)
Module 7 - MAINTENANCE PRACTICES
Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
Cables or chains should be attached from the aircraft picketing
points to prepared anchorages. In some instances the picketing
cables are special components and include a tension meter that
is used to apply a pre-load to the cable.
If an aircraft is to be parked for a longer period, then additional
precautions must be taken. Landing gear down-locks must be
installed (if so equipped) and all openings such as static vents
and engine intakes should be covered or blanked off (refer to
Fig. 3) to prevent the ingress of dirt, birds, insects and all forms
of precipitation.
Intake Blank
Pitot-Static Blanks
Exhaust Blank
Nose Wheel Covers
Main Wheel Covers
Typical Aircraft Blanks
Fig. 3
ISO 9001:2008 Certified
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For Training Purpose Only
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
CHOCKING OF AIRCRAFT
When aircraft are parked, it is normal to place a chock ahead
and behind at least one wheel set. The parking brakes are
usually left in the ‘off’ position once chocks are in position, to
allow the heat, generated by the brakes, to dissipate evenly.
At high wind speeds, it is normal to chock all the wheels and
apply the brakes (if they have cooled). Some aircraft chocks can
be chained together, to give a more secure hold. During ground
runs (and especially those involving high power), it is common
sense to place chocks at the front of all main wheel sets, to
reinforce the parking brake.
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For Training Purpose Only
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Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
AIRCRAFT STORAGE
If an aircraft is de-activated for an extended time it will need to
be protected against corrosion, deterioration and environmental
conditions during its period of storage.
The following notes are based on the storage procedures
applicable to BAe 146 aircraft that have been de-activated for
periods in excess of 30 days and up to a maximum of 2 years. It
is not intended for the information given here to be complete,
but merely to give the student examples of some of the activities
performed. Specific details of an aircraft’s storage procedures
can be found in Chapter 10 of the relevant Maintenance
Manual.
Generally there would be an initial procedure, this being
repeated at specified intervals, as shown in Tables 1 (a) and 1
(b). If no repeat interval is given, then the item is only done
initially.
Once the aircraft has been prepared, there are routine, weekly
checks to keep it in good condition.
A list of equipment and materials is normally given. This will,
typically, include:




Hydraulic fluid and lubricating oils and greases
Specialised
water-displacing fluids
and
preventative compounds
Aircraft covers and blanks
Plastic sheeting and adhesive tape.
corrosion-
Prior to the storage period certain tasks are completed. These
may include replacing the tyres with ‘dummy’ tyres (those not
suitable for flight), or the raising of the pressures of the normal
ones. The various tanks are either filled (water), drained (toilet),
or part-filled (fuel). If the aircraft has propellers, they must be
feathered, to prevent them rotating in the wind. (they may also
be restrained by straps).
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7.17 - 17
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
For Training Purpose Only
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ISO 9001:2008 Certified
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
For Training Purpose Only
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To allow the circulation of air around the inside of the aircraft, all
the doors and curtains are fixed open, whilst all the external
doors and panels are shut. The battery will be removed from the
aircraft and kept in the battery bay.
More active checks might be done on the two-weekly checks.
These checks will probably involve re-installing the battery,
running the engines for a period and functionally testing a
number of the aircraft’s systems that require the engines
operating. The flight controls might require cycling throughout
their ranges and, if dummy tyres are not fitted, the aircraft must
be moved slightly to prevent ‘flat spots’ forming on the tyres.
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
All the tanks must be replenished to their correct levels and all
pressure vessels will require their gases charging to their
normal operating pressures. If the cabin furnishings, such as
seats, carpets and galleys have been removed, they are to be
inspected and, when serviceable, re-installed in the cabin.
As already stated, the foregoing summaries are only examples
of the form that a basic aircraft storage procedure might take. If
the aircraft is smaller or larger and more complex it will require a
different form of inspection and routine checking.
The correct storage procedures will be found in Chapter 10 of
the relevant aircraft’s Maintenance Manual.
In addition, when power plants are stored separately, their fuel
and oil systems must be inhibited and all their external
mechanisms protected with grease or other suitable
preservative. They must be stored in a clean, warm, dry
atmosphere with inspections at intervals to check for
deterioration. Some engines are stored in an airtight bag, which
has moisture-absorbent crystals (a desiccant) inside.
After the storage period all of the covers, blanks and
preservative compounds will need to be removed. All of the
systems will need to be restored to their original condition prior
to aircraft use. A further set of procedures will be followed,
similar to those previously discussed.
When the aircraft is to be returned to service, it is simply a case
of initially removing all covers, blanks and tie-downs. Once
access to the inside of the aircraft is obtained and the battery
re-installed, all of the systems must be checked and tested.
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Sub Module 7.17 - Aircraft Handling and Storage
AIRCRAFT FUELLING PROCEDURES
The use of the term ‘fuelling’ can include both refuelling and
defuelling procedures and these notes contain examples of the
essential points to be considered when refuelling and defuelling
aircraft.
There may, however, be some further, local instructions,
regarding the responsibilities of the various personnel involved
in fuelling procedures and these will always take precedence in
conjunction with the relevant Maintenance Manual.
Fuelling Safety Precautions
Particular care must be taken when fuelling aircraft, so that the
operation may be accomplished in the safest possible manner.
Whenever possible, aircraft should be fuelled in the open, and
not in a hangar (although this is, sometimes, necessary as part
of a maintenance programme). This will minimise the fire risk
from high concentrations of flammable vapours.
Fire appliances should be readily available during all fuelling
operations. Carbon dioxide, or foam, extinguishers are
recommended but, if there is a perceived increased fire risk,
then fire-fighting vehicles should be standing by.
Within the specified danger area, around an aircraft being
fuelled, no sources of ignition or sparks should be allowed and
no electrical power should be switched on or off during the
fuelling operation.
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It is vital that the correct type and grade of fuel is used for the
fuelling operation. Use of a turbine fuel in a piston aircraft will
certainly cause an engine malfunction, or failure, that could lead
to loss of an aircraft. The correct type and grade of fuel is
always detailed in the Maintenance Manual and marked
adjacent to the aircraft’s fuelling point(s).
Care should also be exercised so as to avoid contamination of
the fuel system with water or other contaminants. The fuel
supply should be regularly checked for water contamination and
a sample of fuel drained off after refuelling, so that a water
check may be done.
It will sometimes be necessary to filter the fuel during over-wing
refuelling, particularly in dusty climates.
Electrical bonding of the fuel system is vital during fuelling
operations, as when fuel flows through the refuelling hose, static
electricity may be generated. This may lead to potential
differences at adjacent metal parts and initiate a spark, fire or
explosion. To minimise this risk the following actions should be
completed before fuelling operations commence



The aircraft should be earthed
The refuelling tanker should be earthed
The nozzle of the fuel hose should be electrically
bonded to the fuelling point.
For Training Purpose Only
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PIA TRAINING CENTRE (PTC)
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
Refueling
When refuelling the AMM should always be consulted so that
the positions and capacities of the fuel tanks and also the type
of fuel, position of the refuelling point(s) and refuelling
procedures are known. There are two general re-fuelling
methods:


Gravity or over-wing refuelling: which is, essentially, the
same method as used to refuel a motor car (automobile),
with a similar type of refuelling hose being used. As the
name suggests, the filler points are, generally, on the upper
surface of the wing and the tank is open when refuelling is
done.
Pressure refuelling: in which the fuel may be pumped into
the aircraft via a pressure refuelling coupling at very high
rates. The refuelling pressures and the rates of fuel delivery
may be quite different for individual aircraft types, so great
care must be taken, to ensure no damage occurs to an
aircraft through incorrect refuelling settings.
The aircraft fuel gauges will normally be positioned on the flight
deck, but they can, on some aircraft, be duplicated at a fuelling
panel, adjacent to the pressure refuel coupling.
The Relative Density (RD) of fuel will vary with temperature and
so the weight of a certain quantity of fuel will also vary.
For example, ten gallons (Imperial) of fuel, with an RD of 0.8,
will have a weight of 80 lb, while ten gallons (Imperial) of fuel,
with an RD of 0.78, will weigh 78 lb.
It is crucial, for balance purposes, that the weight of fuel is
known and this is the reason why many aircraft fuel gauges are
calibrated in units of weight rather than in volume.
When fuelling aircraft, it is essential that the technician is aware
of the RD of the fuel, so that the necessary weight calculation
may be done, if necessary.
Checking fuel contents
This is normally done, using the aircraft fuel gauges, which may
be calibrated in kilograms (kg), gallons (Imperial or US) or
pounds (lb).
If a double check is required, then the contents may be
determined, on the ground, by using ‘dip sticks’ (installed into
the top of the tanks) or by ‘drip sticks’ (or magnetic ‘drop sticks’)
which are installed in the bottom of some aircraft tanks.
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
DEFUELLING
Occasionally, it is necessary to remove fuel from an aircraft, to
facilitate fuel tank maintenance, or because the aircraft is too
heavily loaded for the next flight.
Removing fuel from an aircraft can be accomplished by either
the gravity or by the pressure defuelling method.
The gravity method entails draining the fuel into a suitably
earthed container, and this is typical of light aircraft, which are
normally ‘gravity’ refuelled. The fuel removed must be disposed
of in the correct manner, with regard to local instructions and to
the environment.
Aircraft that are normally pressure refuelled are normally
equipped with a pressure defuelling facility. Pressure defuelling
is achieved by utilising a small negative pressure (suction),
which effectively draws the fuel out of the tank and returns it into
the fuel tanker (bowser).
Current rules will normally only allow the fuel, removed from an
aircraft, to be placed into a dedicated defueller vehicle and the
fuel will not be permitted to be used in another aircraft. This
ensures that any contamination such as water or debris will not
be transferred to other aircraft.
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
DE-ICING/ANTI-ICING OF AIRCRAFT
Ice Types
There are three main types of ice/frost that can affect an
aircraft’s performance, Hoar Frost, Rime Ice and Glaze Ice. The
temperature and weather conditions will determine the type of
ice that forms, but all three types can have a detrimental effect.
The Dew Point is the temperature at which moist air becomes
saturated and deposits dew if in contact with a colder surface or
the ground. Above ground, condensation into water droplets
takes place.
Hoar Frost is a deposit of ice crystals that form on an object
when the dew point is below freezing point. High humidity will
normally produce hoar frost, as these are similar to conditions
that produce dew. Hoar frost can form when the air temperature
is greater than 0°C, but the aircraft skin temperature is less than
0°C. This type of frost produces a very rough surface which
leads to turbulent airflow.
Glaze Ice can be either transparent or opaque and can form into
a glassy surface due to liquid water flowing over a surface
before freezing. It is the most dangerous type of ice found on an
aircraft and is dense, heavy and tough. It adheres firmly to a
surface, is difficult to shake off, and if it does breakaway, it does
so in large chunks.
During cold weather operations, it may be necessary to remove
ice and snow from the aircraft, while it is on the ground, and to
keep it clear long enough, to allow the aircraft’s systems to cope
with snow or ice removal. This may not occur until the aircraft is
flying.
Rime Ice is a light coloured opaque rough deposit that has a
porous quality. At ground level it forms in freezing fog from
water droplets with very little spreading. It adds very little weight
but it can disrupt the smooth flow of air over the wing, and block
pitot and static vents.
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Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
On the ground, the aircraft must be cleared of all snow and ice
from its wings, tail, control surfaces, engine inlets and other
critical areas (refer to Fig. 4) before the aircraft can take-off.
Ice formation on an aircraft on the ground may result from a
number of causes:



Direct precipitation from rain, snow and frost
Condensation freezing on external surfaces of integral tanks
following prolonged flight at high altitude
After taxing through snow or slush, ice may accumulate on
landing gear, forward facing surfaces and under-surfaces.
Rudder
Ailerons
VHF
Antenna
Elevator
TCAS
Antenna
Flaps
Pitot and
Static
Heads
Slats
Engine Nacelle
Critical Surfaces for De-icing and Anti-icing
Fig. 4
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Category – A/B1
The formation of ice on aircraft structures can produce many
adverse effects, and if allowed to remain may result in some or
all of the following:







Decreased aerofoil lift
Increased aerofoil drag
Increased weight
Decreased engine thrust
Freezing of moisture in control hinges
Freezing of micro-switches that affect systems such as the
landing gear retraction
Ingestion of ice into the engine.
Definitions
The terms ‘de-icing‘ and ‘anti-icing’ have specific definitions,
and it is essential to know the differences.


Sub Module 7.17 - Aircraft Handling and Storage
De-Icing and Anti-Icing Methods
The de-icing procedure for removal of ice, frost and snow from
an aircraft’s surface can be achieved by mechanical or chemical
methods. Mechanical methods use blowers, brushes and rubber
scrapers whilst chemical methods utilise de-icing fluids.
The anti-icing procedure provides protection against the
formation of ice, frost and snow on aircraft surfaces for a short
period known as the ‘Holdover Time’. This is achieved by
applying an anti-icing fluid, but the aircraft must be either clean
or de-iced prior to this anti-icing fluid application. There are two
ways of aircraft de-icing and anti-icing:


One Step Method
Two Step Method.
De-icing is the removal of ice that has already formed
Anti-icing is the prevention of initial ice formation.
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For Training Purpose Only
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Category – A/B1
The One Step method utilises hot fluid to de-ice the aircraft, and
this fluid remains on the aircraft surfaces to give a limited antiicing capability.
The Two Step method consists of two separate fluid application
procedures. The first step is the de-icing part and the second
step the anti-icing. This second step must be done within three
minutes of starting the first step, surface by surface if
necessary. The second anti-icing step protects the aircraft
surfaces for a holdover period.
Whilst the AMM will detail the exact areas for de-icing and antiicing, particular attention should be paid to areas around
probes, antennas, and pitot/static ports as well as control
surfaces, landing gear and inlets and exhausts.
Chemical De-Icing
Freezing Point Depressant (FPD) compounds are often used in
conjunction with mechanical methods, and there are two main
types of FPD compounds:

Sub Module 7.17 - Aircraft Handling and Storage
These fluids have a minimum glycol content of approximately
50%, and due to a thickening agent, are able to remain on the
aircraft surfaces for longer periods. The de-icing performance is
good and provides protection against re-freezing and/or build up
of further accretion, when exposed to freezing precipitation.
Treatment of Frost Deposits
Frost deposits are best removed by the use of a de-icing fluid
such as Kilfrost ABC (Aircraft Barrier Compound). These fluids
usually contain either:



ethylene glycol and isopropyl alcohol
di-ethylene glycol and isopropyl alcohol
propylene glycol and isopropyl alcohol.
This process is not lengthy and one application is usually
sufficient provided it is applied within two hours of flight. Only
fluids recommended by the manufacturer should be used and
any instructions for their use should be strictly observed. Use of
incorrect de-icing fluids may adversely affect glazed panels or
paint finish.
Type 1 (unthickened)
These fluids have a high glycol content and a low viscosity.
They provide good de-icing performance but only a limited
protection against re-freezing.

Type 2 (thickened)
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For Training Purpose Only
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PIA TRAINING CENTRE (PTC)
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Category – A/B1
Alcohol based de-icing fluids, may cause dilution or complete
removal of oils and greases from joints or bearings. This may
allow water ingress, which can subsequently freeze and jam
controls. De-icing spray nozzles should not be directed at
lubrication points or sealed bearings.
Hot air blowers may be used to remove snow, ice or frost, and
the liquid residue should be dried and not allowed to
accumulate in places such as hinges or micro-switches as any
re-freezing may cause damage.
Sub Module 7.17 - Aircraft Handling and Storage
Moderate to heavy ice deposits or residual snow should be
cleared with de-icing fluid applied by spraying. The two methods
of fluid spraying involve the:


Cold Fluid Spray
Hot Fluid Spray.
When using these sprays, it is necessary to observe certain
precautions, because of the risk of damage to the aircraft
structure and associated components. With this in mind it is
important to know that:
Removal of Ice and Snow Deposits

There are several methods of removing snow and ice from an
aircraft, prior to applying liquids if required.
Removal by hand can be accomplished by the use of soft
brooms, hand brushes or rubber scrapers. The aircraft can be
de-iced using cold air from a pressure supply unit, or by using
hot air from a hot air blower designed for the purpose.
Deep wet snow should be removed with a brush or rubber
scraper, taking care not to damage components such as aerials
and pitot probes, which may be covered in snow. The snow
should also be cleared from items like vents and control hinges.
Light dry snow should be blown off using a cold air blower. Hot
air is not recommended as it may melt the snow which may
accumulate and freeze requiring further treatment.
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



High-pressure sprays may cause damage to pitot-static
probes and other sensing devices
Covers and bungs should be fitted during de-icing
operations to prevent ingress of fluid into intakes and
exhausts
High-pressure sprays may cause erosion of the aircraft skin.
Consult the AMM for recommended maximum impingement
pressure
No attempt should be made to remove ice by using an
impact force to break the bond
De-icing should proceed symmetrically, to prevent excess
weight on one side of the aircraft.
The Cold Fluid Spray method is the simplest method of applying
de-icing fluid, but in severe conditions one application may not
be sufficient to remove all deposits. Brushing followed by a
second or third application may be required.
For Training Purpose Only
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PIA TRAINING CENTRE (PTC)
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
The Hot Fluid Spray method has been adopted specifically to
reduce turn-round time. The FPD fluid is mixed with water in
proportion to suit prevailing weather conditions, and heated to
between of 60ºC (minimum) and 85ºC (maximum).
The fluid is normally sprayed onto the aircraft at a pressure of
100 psi (689.5 kN/m2) by use of spray lances. The nozzle of the
lance is held close to the aircraft skin, to prevent heat losses.
The heat transfers to the skin of the aircraft, breaking the ice
bond, and large areas of ice may be flushed away by turning the
nozzle sideways. The fluid film remaining on the skin, has only
been slightly diluted beyond its original dilution and is effective
in preventing further ice formation.
Hot water de-icing is a method that must not be used below 70C and may need to be performed in two steps.


Step 1: Snow and ice are normally removed initially with a
jet of hot water not exceeding 95C
Step 2: If necessary a light coating of de-icing fluid is then
sprayed on immediately (within 3 minutes) to prevent refreezing.
On some aircraft, not equipped with aerofoil or propeller deicing systems, the use of a de-icing paste may be specified. The
paste is spread evenly, by hand, over wing, tail and propeller
leading edges. It provides a chemically active surface on which
ice may form but not produce a bond. Any ice, which forms, is
blown away by the airflow. The paste should be re-applied
before each flight in accordance with the AMM.
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Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
Hold Over Times
When used for anti-icing, the FPD fluid should be sprayed onto
the aircraft cold and undiluted, before the onset of icing or after
any hot de-icing. The fluid film will prevent ice and snow from
sticking to the aircraft skin and, given time, will melt any fresh
precipitation. Typical times for which the fluid remains effective
are known as the ‘Hold Over’ time (refer Table 2).
Under extreme cold conditions it may be necessary to heat the
fluid (60C max) to give it sprayability. No significant increase in
hold over time is achieved by strengthening the mix of type I
(AEA) fluids.
Stations using Kilfrost will normally provide a mix of 50/50 or
60/40. It may be difficult to get stronger mixes at short notice
unless the temperature conditions at the stations involved are
below limits for that mix.
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Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
Certain precautions should be observed when applying
chemical anti-icing fluids, and these are:

Anti-icing fluid must NOT be applied on top of a similar,
earlier coat
If possible, the engines or the APU should not be operated
during snow/ice removal
The fluid should not be sprayed directly onto windscreens,
windows, vanes, pitot heads or probes
The minimum quantity of fluid should be used in the air
conditioning intake areas
If possible the fluid should not be sprayed onto lubricated
parts, such as landing gear legs







Inspection after De-Icing/Anti-Icing Procedures


Tyres to ensure that they are not frozen to the ground. They
should be freed by the application of hot air to the ice (not
the tyre) and the aircraft moved to a dry area
Engine air intakes for ice and snow deposits
Gas turbine engines for freedom of rotation by hand.
Restriction may indicate icing in the compressor region and
the engine should be blown through with hot air immediately
before starting until the rotating parts are free
Shock absorber struts and hydraulic jacks for leaks caused
by contraction of seals and metal parts
Tyre pressures and shock absorber pressure and extension
Following the inspections an entry should be made in the Tech.
Log, indicating that the De-Icing/Anti-Icing procedure has been
completed.
The following inspections should be done on completion of a
de-icing procedure:





External surfaces, for signs of residual snow or ice,
particularly in the vicinity of control surface gaps and hinges
All protrusions and vents, for signs of damage
Control surfaces for full and free movement by hand. Where
this is not possible the pilot's controls should be used,
bearing in mind that power-operated controls exert large
forces and could cause damage if any part of the control
surface is frozen
Landing gear mechanisms, doors, bays and wheel brakes,
for snow and ice deposits
Up-locks and micro-switches, for correct operation
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 30
For Training Purpose Only
Rev. 00
Mar 2014
PIA TRAINING CENTRE (PTC)
Category – A/B1
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
GROUND ELECTRICAL SUPPLIES
Ground electrical supplies are normally limited to either 28 volts
dc or 115 volts ac, depending upon the systems of the aircraft.
Most modern aircraft have at least one 115 volt ac system (as
well as a 28 volt dc one), so they will normally be supplied with
115 volts ac from an external power supply.
The 115 volt ac connection has six pins, with four pins being
longer than the other two. The four longer pins provide the three
phases and the neutral connection whilst the short pins provide
the safety interlock.
Airfields normally supply electricity to aircraft through external
generators called Ground Power Units (GPUs), or have
underground supplies, which are connected to the aircraft via
the air-bridge, or from beneath the ramp surface.
When an external electric supply is required inside the hangar,
its generation will normally be through transformer rectifier units.
An external power control box may be installed on the hangar
wall and the required output for a particular aircraft can be
selected.
To prevent accidentally connecting-up of incorrect supplies, all
aircraft have separately-shaped plugs and sockets. The 28 volt
dc supply usually has a three-pin connection whilst the 115 volt
ac utilises a much larger, six-pin plug and socket (refer to Fig.
5).
The 28 volt dc connection has two pins which are longer than
the third. The longer pins are the supply connections whilst the
shorter pin acts as a safety interlock, to ensure that the power is
cut-off, if the cable is inadvertently pulled out without the power
being switched off first.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 31
For Training Purpose Only
Rev. 00
Mar 2014
PIA TRAINING CENTRE (PTC)
Module 7 - MAINTENANCE PRACTICES
Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
3 PIN EXTERNAL
POWER RECEPTACLE
EARTH
dc Power Socket and Receptacle
EXTERNAL
POWER
READY
LIGHT
SERVICE
INTERPHONE
CONNECTION
NOSE
WHEEL
WELL
LIGHTS
EXTERNAL
SUPPLY SOCKET
A.C. PHASE “A”
POSITIVE D.C.
A.C. PHASE “B”
3 PIN
PLUG
POSITIVE D.C.
ACCESS
DOOR
A.C. PHASE “C”
A.C. NEUTRAL
D.C.
ac Power Receptacle
Ground Electrical Supplies
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 32
Fig. 5
For Training Purpose Only
Rev. 00
Mar 2014
PIA TRAINING CENTRE (PTC)
Module 7 - MAINTENANCE PRACTICES
Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
GROUND HYDRAULIC SUPPLIES
Hydraulic test rigs are available, to supply aircraft with a source
of hydraulic power without the need for running the engines or
APU. These test rigs are normally powered either by internal
combustion, or by electric, motors. They must use the same
type of hydraulic pump and fluid as the aircraft under test, to
allow testing of items such as the timing of system operations.
The aircraft has an access panel, behind which are a set of
‘quick-connect’ couplings, allowing the rig hoses to be easily
connected to the aircraft’s system without the need for
‘bleeding’ the system of air. This is achieved by use of nonreturn valves, which only open when the couplings are fully
tightened.
Before connecting a hydraulic testing rig to an aircraft, it must
be ensured that all of the lines and couplings are thoroughly
clean, so that no dirt can get into the aircraft’s system.
Safety, Health and Servicing Precautions
Phosphate ester-based hydraulic fluids constitute a major health
risk. Extreme care should be taken when handling this fluid and
the following precautions should be taken:


Eye protection is essential when the possibility of atomised
spray exists. If fluid contacts the eyes, they should be
flushed with large quantities of clean/sterile water and
medical advice sought promptly

Hands must be washed thoroughly after working with these
fluids and particularly before eating or smoking

Hydraulic fluid must not be allowed to contact the skin for
excessive periods. Barrier cream and protective gloves must
be put on before starting work
Contaminated overalls should be changed as soon as possible
after contact with the fluid.
A typical hydraulic test rig might have a 75kW (100 hp) electric
motor, driving the pump through a gearbox, clutch and a flexible
coupling. The output could be in the region of 175 litres per
minute (38 gallons per minute) at 200 kPa (3000 psi).
The oil would be filtered to the standard required by the aircraft
system, typically, 3 microns.
A mask must be worn when the possibility of inhaling the
fluid in an atomised form exists. The fluid irritates the
respiratory passages and can cause sneezing and coughing
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 33
For Training Purpose Only
Rev. 00
Mar 2014
PIA TRAINING CENTRE (PTC)
Category – A/B1
Most hydraulic rigs have a small header tank of system oil. It
would utilise the aircraft’s oil for the majority of operations, with
the header tank keeping the system primed during coupling and
uncoupling operations.
The flow valves, which are often integral parts the rigs, must be
kept closed until all the hoses have been connected and the rig
is ready to run. The motor is started and once the operating
pressure is indicated on the rig gauges, the valves can be
opened and the rig then forms part of the aircraft system. This
will enable the functional testing of the aircraft’s hydraulic
systems using the aircraft’s selector valves.
The rigs may also be provided with special gauges, such as
flow meters, which will allow the testing for internal system
leakages.
Rig Maintenance
The rigs must have an equal or better filtration level than the
aircraft being serviced. Oil samples of the rig are taken on a
regular basis, and the following checks must be completed on a
regular basis:




Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
GROUND PNEUMATIC SUPPLIES
Pressurised aircraft usually require an adequate supply of lowpressure air, for such tasks as engine starting, ventilation,
heating and cooling, anti-icing and pressurisation testing. This
air supply is, normally, provided by the aircraft’s engine/s or
APU but, when these are unavailable, a ground supply unit can
be used.
Pneumatic units can supply air at the required pressure and
flow rate and are powered by turbine engines, diesel engines or
electrically powered units. The compressors used by these units
are normally axial flow, centrifugal flow, or of the screw or lobe
type.
Depending on the size of the aircraft being serviced and the air
requirements, the compressor can be mounted on a trailer
chassis or on a self-propelled vehicle.
To ensure the air produced is of a suitable quality, it is normally
filtered and cleaned before being fed to the external air supply
connection, which is located on the outside of the airframe.
The rig must be kept clean and all hoses blanked when not
in use
The filters must be changed or cleaned
All the gauges should be calibrated
Any electrical equipment on the rigs should be checked.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 34
For Training Purpose Only
Rev. 00
Mar 2014
PIA TRAINING CENTRE (PTC)
Module 7 - MAINTENANCE PRACTICES
Category – A/B1
Some aircraft have two separate connections for air supplies at
different points on the airframe. The forward connection may be
for low-pressure air, which is then fed directly to the conditioning
system, allowing testing of the air conditioning system and also
of the pressure hull. The aft connection may be for a higherpressure bleed air supply that is primarily used to start the
engines if the APU is unserviceable.
Whilst some units are dedicated air starter rigs, some can be
used both for starting and also for functional testing of the air
conditioning and de-icing systems. As with the electric and
hydraulic ground power supply rigs, the output of a pneumatic
unit must match the aircraft’s system for pressure and flow.
Sub Module 7.17 - Aircraft Handling and Storage
EFFECTS OF ENVIRONMENTAL CONDITIONS
AIRCRAFT HANDLING AND OPERATION
ON
Previous notes have mentioned a range of precautions that
need to be applied when the weather is anything less than
perfect. This section will cover actions that the technician will
need to take for prevailing situations when various weather
conditions exist.
Cold and Wet
When the ramp is cold and wet, the friction between the
aircraft’s tyres and the ramp can be reduced. This also applies
to all self-propelled vehicles and, hence, all movements on the
ramp should be at a slower speed than normal, with quick
access to chocks, in the event of an emergency.
During engine ground running, it is possible that there may be a
maximum power limitation if the ramp is very wet or flooded.
This will be covered in either the Airfield Operations Manual or
the Ground Handling Procedures Manual (as will most other
precautions and procedures).
If large amounts of protective clothing are worn on the ramp, it
is the technician’s responsibility to ensure that nothing can get
sucked into a running engine. Also, during ground running, it is
important that extra chocks are placed at the wheels of the
aircraft to prevent slippage at the higher power settings.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 35
For Training Purpose Only
Rev. 00
Mar 2014
PIA TRAINING CENTRE (PTC)
Module 7 - MAINTENANCE PRACTICES
Category – A/B1
Sub Module 7.17 - Aircraft Handling and Storage
Falling rain (and fog) will demand that more care be taken, due
to the reduced visibility, especially when towing is in progress.
The use of all normal lights, day or night, when moving vehicles
in rain, is most important.
Most airfields that operate continuously have a plan to deal with
excessive amounts of snow. This plan might include the
application of heater units or allowing APUs to run for extended
periods to keep the inside of the aircraft warm.
Where there is a risk of rain and the aircraft is to be parked,
then the appropriate aircraft blanks and covers must be used. It
is also inadvisable to re-fuel aircraft by the ‘open line’ (over
wing) method in rain, due to the high risk of water getting into
the tank whilst the filler cap is removed. Great care must be
taken, to protect the filler neck orifice, so that very little water
enters the tank.
For aircraft, which are to be left out on the ramp, in sub-zero
temperatures, it may be necessary to drain the potable water
tanks, to prevent them freezing overnight. This will involve some
care, as they should not be drained onto the ramp, due to the
risk of personnel slipping on the ice.
If a task needs to be completed on the upper surface of a wet
wing, it would be advisable to use a ‘safety raiser’ or ‘cherry
picker’. This mobile craning device will allow safe access to the
upper surfaces of a high wing and also provide the technician
with a safety device, to hook onto, should the need arise.
Snow and Ice
Other items of equipment that use water, such as heaters and
pipe-work, may also need protection in cold temperatures.
High Winds
High winds can cause loose objects to move across the ramp
and strike the aircraft. These can be light items such as twigs
and branches but, on occasions, heavy pieces of ground
equipment, that have not been secured correctly, have been
pushed into aircraft, causing major damage.
Many of the precautions, already mentioned, also apply in
conditions of snow and ice. Aircraft towing and taxiing may be
restricted until all standing precipitation has been cleared from
the area to be used.
During very high wind conditions, the smallest objects can be
lethal, due to the energy they contain.
The loss of visibility during falling snow can be severe,
especially at times of low light, so great care must be shown if it
is considered essential that an aircraft movement must take
place. This may require a larger than normal towing team and
the use of extra lights.
In certain environments, such as desert climates (or at airfields
near seashores), sand and dust, driven by the wind, can enter
small crevices, causing problems with aircraft systems and may
also block filters. Where extreme conditions exist, such as
during a sand storm, then the blanking of all orifices may have
to be augmented with tape or other methods, to prevent the
ingress of dust and sand.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 36
For Training Purpose Only
Rev. 00
Mar 2014
PIA TRAINING CENTRE (PTC)
Category – A/B1
Great care must be taken, to ensure suitable entries are made
in the Technical Log, for the complete removal of all blanking
material, after the storm has abated.
Module 7 - MAINTENANCE PRACTICES
Sub Module 7.17 - Aircraft Handling and Storage
This facility is known as the ‘Hotel Mode’ and, effectively,
enables an engine to operate in a similar manner to an APU,
without the need to carry extra weight.
High Temperature
Certain items of equipment are temperature-sensitive and,
when aircraft are operated in environments of extreme high
temperature (+55C), then several extra precautions have to be
taken.
Some form of cooling must be provided to ensue that the crew
does not suffer from heat exhaustion, and reduce their
efficiency. The operating temperature electronic equipment
must also be kept below a critical level, to ensure its continued
serviceability.
Most of the larger aircraft have an auxiliary power unit (APU),
which can provide a supply of bleed air to allow the air
conditioning system of the aircraft to operate on the ground.
If an APU is not available, then external air conditioning units
can be connected to the aircraft to keep the inside cool. These
cooling rigs should have an air conditioning unit of suitable
capacity for the size of the aircraft that requires cooling.
Some turbo-propeller passenger aircraft have the facility to run
an engine, without the propeller turning, to provide air
conditioning on the ground.
ISO 9001:2008 Certified
PTC/CM/B1.1 Basic/M7/04
7.17 - 37
For Training Purpose Only
Rev. 00
Mar 2014