unit-1
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UNIT-1 AIRCRAFT GROUND HANDLING AND SUPPORT EQUIPMENT
MOORING:
Aircraft “tie down procedure” with ground or any fixed space, after each flight (or) at the end of
the day of flying is known as “Mooring”. “Picketing” is the term used in Air Force.
Aircraft tie down is a very important part of aircraft ground handling.
The type of tie down will be determined by the prevailing weather conditions.
In normal weather a limited or normal tie down procedure is used, but when storm
conditions are anticipated a heavy weather or storm condition tie down procedure should
be employed.
Gale – strong wind – 55-75 km/h
Storm – violent wind - 75-130 km/h
Hurricane – violent wind storm - > 130 km/h
Normal tie down procedures (or) storm condition tie down procedures is different for different
aircraft and weather condition.
Light aircrafts
Medium aircrafts
Heavy aircrafts
Helicopters
Seaplanes & airplanes on skis (floats)
Civil / military use
Open tarmac / closed hangers
Blast pens(concrete roofing) / blast pens (iron roofing)
All with / without camouflaged coverings
Equipment:
Tie down requirements:
Location of the tie down point
Tie down anchors / picketing blocks
Tie down ropes /chains
Wheel chocks
Tie down anchors:
All aircraft parking areas should be equipped for 3 point tie downs.
In most of the airports tie down anchors are installed in concrete parking areas. Tie down anchors
are sometimes called “pad eyes” , are ring like fittings installed when the parking area is poured.
They are normally set flush with the surface of the concrete.
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There are several types of tie down anchors in use. The type selected is usually determined by the
material used in aircraft parking areas, since it may be a concrete paved surface, a bituminous paved
surface.
Location of tie downs is usually indicated by white or yellow paint markings or by surrounding the
tie down anchor with crushed stone.
Tie down anchors for small single engine aircraft should provide a minimum holding power
(strength) of approximately 3000 pounds each. Although this minimum can be achieved when stake-
driven tie downs are used in dry areas, such stakes will almost invariably pull-out when the ground
becomes soaked from torrential rains which accompany hurricanes and thunderstorms.
Tie down ropes / cables / chains:
Tie down ropes should be capable of resisting a pull of 3000 pounds (approximately) for light aircraft
tie down. Manila ropes (if used) should be inspected periodically for mildew and rot. Nylon or
Dacron tie down ropes are preferable for manila rope.
Tie down cables are used to secure large aircrafts. Cable tie downs are accomplished with some
form of tie down reels designed for rapid and reliable securing of all types of aircrafts.
Tie down chains are used for better and stronger tie down to secure the heaviest aircrafts. This tie
down assembly is composed of an all metal quick-release mechanism, a tensioning device, and a
length of chain with hooks.
PRECAUTIONS:
Points to be observed while securing light aircraft:
Light aircrafts are often secured with ropes. Hence no rope should be tied to a lift strut.
If manila rope is used, allow about 1” of slackness as it shrinks when wet. Too much slack will
cause the aircraft to jerk against the ropes.
Use slop knots to tie the rope at tie down anchors and at aircraft mooring points / rings.
(Remember that a tight tie down will impart inverted flight stresses)
Points to be observed while securing heavy aircrafts:
First of all, all the control surfaces of the heavy aircrafts should be locked using the
appropriate locking devices.
Head the airplane into prevailing wind whenever possible.
Install all control locks, all covers and guards.
Check all wheels fore and aft.
Attach tie down reels to airplane tie down loops and to tie down anchors (or tie down
stakes). If tie down reels are not available, ¼ inch wire cable or 1 ½ inch manila rope can be
used.
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Aircraft tie down for storm conditions:
Special points to be observed:
Know the local weather conditions because there is sufficient warning for the large and
heavy wind storms whereas the local ones build up quickly and give little warning of their
coming. Hence study of weather map and weather report from meteorological section to be
consulted.
The best protection against windstorm damage is to fly the aircraft out of the impending
storm area when there is sufficient time.
The next best protective measure is to secure the aircraft in a storm proof hanger.
The remaining alternative is to assure that the aircraft is tied down securely.
When securing the aircraft, fasten all the doors and windows properly, cover the engine
intakes and exhausts to prevent FOD entering into the openings; cover the pitot-static tubes;
lock the control surfaces.
Observe the minimum recommended strength for tie down ropes ( as given in the
manufacturer’s recommendations).
A single row of properly secured sand bags or spoiler boards ( 2’ x 2’) on the top of a wing’s
leading edge will serve as an effective spoiler and reduce the lifting tendency of the wings (
do not overload the wing with sand bags).
Partially disassembled aircrafts which are outdoors should be hangered as soon as storm
warnings are received.
Securing multiengine aircrafts:
The anchor should be capable of a holding of 400 pounds each for the lighter twin engine
executive aircraft. Much higher load capacity is required for the heavier transport aircraft.
Whenever the multiengine aircrafts are left unattended for some length of time, they are to
be properly tied down, chocked, gust locks for the control surfaces installed and landing gear
down lock safety pins installed.
Securing of helicopters:
Structural damage can occur from high velocity surface winds. Therefore, if at all possible,
helicopters should be evacuated to a safe area if tornados or hurricanes are anticipated. When
possible, helicopters should be secured in hangers. If not, they should be tied down securely.
Helicopters that are tied down can usually sustain winds up to approximately 65 miles per hour.
For added protection, move the helicopters to an open surface (no tree etc...).If high winds are
expected, tie down the rotor blades. Refer the maintenance manual. Wind chocks, control locks,
rope tie downs, mooring covers, tip socks, tie down assembles, parking brakes, and rotor brakes are
used to secure helicopters.
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PROCEDURE:
Normal tie down procedure:
Small aircraft should be tied down after each flight to prevent damage from sudden storms.
The direction in which aircrafts are to be parked and tied down will be determined by prevailing or
forecast wind direction.
Aircraft should be headed as nearly as possible, into the wind, depending on the locations of the
fixed, parking area tie down points.
Spacing of tied downs should allow for angle wing tip clearance.
After the aircraft is properly located, lock the nose wheel or the tail wheel in the fore and aft
position.
Typical mooring procedure for helicopters:
Head the helicopters in the direction from which the highest forecasted wind or gusts are
anticipated.
Spot the helicopter slightly more than rotor span distance from the other aircraft.
Place wheel chocks against ahead of and behind the wheels. On helicopters equipped with
skids, retract the handling wheels, lower the helicopter to rest on the skids, and install wheel
position lock pins.
Install a tie down assembly on the end of the blade and align the blade over the tail boom
and secure the tie down straps under the hubs of tail boom.
Fasten the tie down ropes or cables to the forward and aft landing gear cross tubes and
secure to ground stakes or tie down rings.
Securing seaplanes and aircrafts on skis:
Aircraft mounted on floats or skis should be secured to tie down anchors or “dead man”
sunk under the water or ice.
When warning of an impending storm is increased and if is not possible to fly the aircraft out
of the storm area, some compartments of the seaplane can be floated, partially sinking the
aircraft.
In addition, the aircraft should be tied down securely to anchors.
Seaplanes tied down on land have been saved from high wind damage by filling the floats
with water in addition to tying the aircraft in usual manner.
Operators of ski-equipped aircrafts sometimes pack soft snow around the skis, pour water
on the snow, and permit the skis to freeze to the ice.
This, in addition to the usual tie down procedures, aids in preventing damage from wind
storms.
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JACKING the aircraft:
Jacking the aircraft means, to raise the aircraft levelly with help of jacks (ex. Tripod jack).
The aviation technician must be familiar with the jacking of the aircraft in order to perform
maintenance and inspection. Since jacking procedures and safety precautions vary for different
types of aircrafts. We have to consult the applicable aircraft manufacturer’s maintenance
instructions for specific jacking procedures.Fig.1
Choosing jacks:
Tripod jacks are used when the complete aircraft is to be jacked.
A small single base jack is used when only one wheel is to be raised. Fig.2
Need of jacking the aircraft:
1. In order to perform maintenance and inspection.
2. Most specifically changing and checking the landing gear & wheel. Fig.3
Precautions:
Extensive aircraft damage and serious personal injury have resulted from careless or improper
jacking procedures.
1. As an added safety measure, Jacks should be inspected before use to determine,
1. the specific lifting capacity,
2. proper functioning of safety locks,
3. condition of pins, and
4. General serviceability.
2. before raising an aircraft on jacks, all work stands and other equipment should be removed from
under and near the aircraft.
3. No one should remain in the aircraft while it is being raised or lowered, unless maintenance
manual procedures requires such practice for observing levelling instruments in the aircraft.
4. The aircraft to be jacked must be located in a level position, well protected from the wind. A
hanger should be used if possible.
5. The manufacturer’s maintenance instruction for the aircraft being jacked should be consulted for
the location of the jacking points.
6. These jacking points are usually located in relation to the aircraft centre of centre of gravity so
that aircraft will be well balanced on jacks. However, there are exceptions to this. On some aircrafts,
it may be necessary to add weight to the nose or tail of the aircraft to achieve a safe balance.
Sandbags are usually used for this purpose.
7. The jacks used for jacking the aircraft must be maintained in good condition, a leaking or damaged
jack must never be used. Also each jack has a maximum capacity, which must never be exceeded.
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PROCEDURE:
Jacking the complete aircraft:
Prior to jacking the aircraft, an overall survey of the complete situation should be made to
determine if any hazards to the aircraft or personal exist.
Prior to jacking, determine if the aircraft configuration will permit jacking.
Jacking procedures and safety precautions vary for different types of aircrafts. We have to consult
the applicable aircraft manufacturer’s maintenance instructions for specific jacking procedures.
Tripod jacks of the appropriate for the aircraft being jacked should be placed under the aircraft
jacking points and perfectly centred to prevent them from cocking when the aircraft is raised.
The legs of the jacks should be checked to see that they will not interfere with the operations to be
performed after the aircraft is jacked, such as retracting the landing gear.
Considering Jacking points:
At least 3 places or points are provided on aircraft for jacking purposes; a fourth place on some
aircraft is used to stabilise the aircraft while if it is being jacked at the other 3 points.
The 2 main places are on the wings, with a smaller one on the fuselage near either the tail or the
nose, depending on the landing gear design.
Considering jack pads:
Most aircrafts have jack pads located at the jack points. Others have removable jack pads that are
installed into receptacles bolted in place prior to jacking. The correct jack pad should be used in all
cases. The function of jack pad is to ensure that the aircraft load is properly distributed at the jack
point and to provide a convex bearing surface to mate with the concave jack stem.
Considering stress panels:
There may be equipment or fuel which has to be removed if services structural damage is to be
avoided during jacking. If any other work is in progress on the aircraft, ascertain whether any critical
panels have been removed. On some aircraft the stress panels or plates must be in place when the
aircraft is jacked to avoid structural damage.
Extend the jacks until they contact the jack pads. A final check for alignment of jacks should be made
before the aircraft is raised, since most accidents during jacking are the result of misaligned jacks.
When the aircraft is ready to be raised, a man should be stationed at each jack.
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The jacks should be operated simultaneously to keep the aircraft as level as possible and to avoid
overloading any of the jacks. This can be accomplished by having the crew loader stand in front of
the aircraft and give instructions to the man operating the jacks.
Caution should be observed since on many jacks, the piston can be raised beyond the safety point
therefore; never raise any aircraft higher than is necessary to accomplish the job.
The area around the aircraft should be secured while the aircraft is on jacks.
Climbing on the aircraft should be held to an absolute minimum, and no violent movements should
be made by persons who are required to go abroad.
Any cradles or necessary supports should be placed under the fuselage or wings of the aircraft at
the earliest possible time, particularly if the aircraft is to remain jacked for any length of time.
On collets equipped jacks, the collets should be kept within 2 threads of the lift tube cylinder during
rising, and screwed down firmly to the cylinder after jacking is completed to prevent settling.
Before releasing jack pressure and lowering the aircraft, make certain that all cribbing, work stands
and persons are clear of the aircraft, that the landing gear is down and locked, and that all grand
locking devices are properly installed.
Jacking on wheel of an aircraft:
When only one wheel has to be raised to change a tire or grease wheel bearings, a low single
base jack is used.
Before the wheel is raised, the remaining wheels must be checked fore and aft to prevent
movement of the aircraft.
If the aircraft is equipped with a tail wheel, it must be locked.
The wheel should be raised only high enough to clear to concrete surface.
Hoisting the airplanes:
It is often necessary to hoist airplanes and helicopters in order to perform certain service
and maintenance operation.
When hoisting the entire aircraft or any of the airplane components, it is recommended that
hoisting slings, manufactured specifically for the airplane be used.
These slings are designed to lift the airplane or components from the approximate centre
of gravity.
Most fuselage hoist slings are adjustable to allow for different weight and centre of gravity
variations.
EQUIPMENT:
1. JACKS (ex. tripod jack, single pod jack). Mostly hydraulic operated. As prescribed by
manufacturer maintenance manual.
2. Work stand, cradles or necessary supports.
3. Jack pods.
4. Stress panels.
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5. Slings.
6. Crew members.
Levelling the aircraft:
Levelling the aircraft means to level the altitude of the aircraft, so that it is easy to do perform
maintenance operations.
The level altitude of the aircraft includes both a longitudinal level and a lateral level position once
the aircraft is level longitudinally and laterally, the components can be rigged.
The various aircraft manufacturers have devised several methods by which the technician can
establish the level altitude of the aircraft.
Need for Levelling:
When rigging an aircraft, it may be necessary to establish the aircraft in a level altitude prior
to checking and adjusting wings and control surfaces.
These operations are needed while calibrating the fuel gauge instruments and also while
harmonising the aircraft guns.
Levelling of aircraft is also needed while weighing the aircraft.
Precautions:
Extensive aircraft damage and serious personal injury have resulted from careless or improper
levelling procedures.
1. As an added safety measure, Jacks & levelling adjusters should be inspected before use. Example
1. the specific lifting capacity,
2. Proper functioning of adjuster, safety lockset.
3. General serviceability.
2. Before raising & levelling an aircraft, all work stands and other equipment should be removed
from under and near the aircraft.
3. No one should remain in the aircraft while it is being levelled, unless maintenance manual
procedures requires such practice for observing levelling instruments in the aircraft.
4. The aircraft to be levelling must be located in well protected from the wind. A hanger should be
used if possible.
5. The manufacturer’s maintenance instruction for the aircraft being levelled should be consulted for
the location of the inclinometers or sprit level.
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6. The levelling points are usually located in a structural member of fuselage or wing. On some
aircrafts, it may be necessary to add weight to the nose or tail of the aircraft to achieve a safe
balance. Sandbags & slings are usually used for this purpose.
7. The sprit level and other equipment used must be maintained in good condition.
8. Rigging the cables should be handled carefully and other possible operation on wings.
Procedure:
The various aircraft manufacturers have devised several methods by which the technician can
establish the level altitude of the aircraft.
Basic methods:
One method used on many light aircraft is to set a spirit level on a longitudinal structural member
to establish the longitudinal level position and another spirit level across the specific structural
member to establish lateral level position.
The same basic procedure is used in some aircraft by the installation of 2 nut plates on the side of
the fuselage. Screws can be placed in these nut plates, and longitudinal level is determined when a
spirit level placed on the extended screws is level.
Some aircrafts make use of a plump bob and a target to establish the aircraft level on both axes.
This is done as shown in below by suspending a plump bob from a specified structural member and
adjusting the aircraft until the plump bob is centred at the target.
Another method used is to attach a permanent spirit level to the aircraft for each of the 2 axes.
These levels are normally located in an equipment or a wheel well and may have an accuracy as
great as 1/8 ⁰.
If an aircraft is not level the aircraft may be levelled by the use of supports under the aircraft, such as
jacks or tail stands. The inflation of tires and struts can be adjusted as can the fuel loads in wings and
fuselage tanks.
1. Attach the jacks & extend the jacks until they contact the jack pads. A final check for
alignment of jacks should be made before the aircraft is raised.
2. A crew member must be there in front of an aircraft to identify and instruct the others to
level the aircraft.
3. A sprit level must be watched continuously , to instruct the crews to adjust which side to
adjust.
4. Initially longitudinal levelling is adjusted with help of jacks, slings, sand bags.
5. Now lateral levelling is checked and then adjusted.
6. Any cradles or necessary supports should be placed under the fuselage or wings of the
aircraft at the earliest possible time, particularly if the aircraft is to remain levelled for any
length of time.
7. Caution should be observed at all the time, when the aircraft is levelled.
8. No violent movement of personal or any other equipment near the aircraft.
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Note:
Levelling the aircraft to the desired angular displacement in either longitudinal axis or in
lateral axis may be achieved using appropriate inclinometers.
Equipment:
1. Sprit level
2. Plumb bob
3. Jack pods.
4. Slings.
5. Inclinometers.
6. Necessary supports, ropes,
7. Crew members.
Towing:
Movement of large aircraft on an airport and about the flight line and hanger is usually accomplished
by towing with a tow tractor (sometimes called a ‘mule’ or ‘tug’)
.In the case of small aircraft; most moving is accomplished by hand, by pushing on certain areas of
the aircraft surface. Aircraft may also be taxied about the flight line, but usually only by certain
qualified persons.
General precaution:
Towing aircraft can become a hazardous operation, causing damage to the aircraft and injury to
personnel, if done recklessly or carelessly.
The following outlines the general procedure for towing the aircraft; however specific instructions
for each model of aircraft are detailed in the manufacturer’s maintenance instructions and should be
followed in all instances.
Before the aircraft to be towed is moved, a qualified man must be in the cockpit to operate the
brakes in case the tow bar should fail or become unhooked; the aircraft can then be stopped,
preventing possible damage.
Some types of tow bars available for general use can be used for many types of towing operations.
These bars are designed with sufficient tensile strength to pull most aircraft, but are not intended
to be subjected to torsion or twisting loads.
Although many have small wheels that permit them to be drawn behind the towing vehicle going to
or from an aircraft, they will suffer less damage and wear if they are loaded aboard the vehicle and
hauled to the aircraft.
When the bar is attached to the aircraft, all the engaging devices should be inspected for damage
or malfunction before moving the aircraft.
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Some tow bars are designed for towing various types of aircraft; however, other special types can
be used on a particular aircraft only. Such bars are usually designed and built by the aircraft
manufacturer.
When towing the aircraft, the towing vehicle speed must be reasonable, and all persons involved in
towing must be alert.
When the aircraft is stopped, the brakes of the towing vehicle alone should not be relied upon the
shop of the aircraft. The man in the cockpit should co-ordinate the use of the aircraft brakes with
those of the towing vehicle.
The attachment of the tow bar will vary on different types of aircraft. Aircraft equipped with tail
wheels are generally towed toward forward by attaching the tow bar to the tow rings on the main
landing gear.
In most cases it is permissible to tow the aircraft in reverse by attaching the tow bar to the tail
wheel axle. Anytime an aircraft equipped with a tail wheel is towed, the tail wheel must be unlocked
or the tail wheel locking mechanism will be damaged or broken.
Aircraft equipped with tricycle landing gear are generally towed forward by attaching a tow bar to
the axle of the nose wheel. They may also be towed forward or backward by attaching a towing
bridle or specially designed towing bar to the towing lugs on the main landing gear. When an aircraft
is towed in this manner, a steering bar is attached to the nose wheel to steer the aircraft.
Towing and parking procedures:
Only competent persons checked out should direct an aircraft towing them.
The towing vehicle driver is responsible for operating his vehicle in a safe manner and
obeying emergency stop instructions given by any team member.
The person in charge should assign team personnel as wing walkers. A wing walker should
be stationed at each way wing tip in such a position that he can ensure adequate clearance
of any obstruction in the path of the aircraft. A tail walker should be assigned when sharp
turns are to be made, or when the aircraft is to be backed into position.
A qualified person should occupy the pilot’s seat of the towed aircraft to observe and
operate brakes as required. When necessary, another qualified person is stationed to watch
aircraft hydraulic pressure system and maintain if necessary.
The person in charge of the towing operation should verify that, an aircraft with a steerable
nose wheel, the locking scissors are set to full swivel for towing. The locking device must be
reset after the tow bar has been remoulded from the aircraft.
Under no circumstances should anyone be permitted to neither walk or ride between the
nose wheel of an aircraft and the towing vehicle, nor ride on the outside of the aircraft or on
the towing vehicles. In the interest of safety, no attempt to board or leave a moving aircraft
or towing vehicle should be permitted.
The towing speed of aircraft should not exceed that of the walking personnel. The aircrafts
engines are usually not operated when the aircraft is being towed into position.
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The aircraft brake system should be changed before each towing operation. Aircrafts with
faulty brake system can be towed with personnel walking side by and ready with chocks for
emergency use.
Close the entrance doors retract the ladders and install the gear down locks when towing.
Check all tyres and landing gear struts for correct pressure before towing any aircraft.
Avoid sudden starts and stops. As far as possible avoid applying aircraft brakes while towing.
Aircrafts are to be parked with enough space in-between to allow for the movement of air
field vehicles such as refuellers, fire tenders, starting trolleys etc.
Place the wheel chocks fore and aft of the main landing gear of the parked aircraft.
Internal and external control locks (gust locks) should be used while the aircraft is parked.
Contact the airport control tower on the appropriate frequency for clearance to proceed
further when the aircraft has to cross runways.
Aircrafts should be statically grounded when parked inside the hanger.
Engine starting procedures-piston engines:
Starting procedures:
Reciprocating engines are capable of starting in fairly low temperatures without the use of engine
heating or oil dilution, depending on the grade of the oil used.
The various covers protecting the aircraft must be removed before attempting to turn the engine.
External sources of electrical power should be used when starting engines equipped with electric
starters. This eliminates an excessive burden on the aircraft battery.
All unnecessary electrical equipment should be left off until the generators are functioning electrical
power to the aircraft power bus.
Before starting a radial engine that has been shut down for more than 30 minutes, check the ignition
switch for “off”, turn the propeller 3 or 4 complete revolutions with the starter, or it may be pulled
through by hand to detect a “hydraulic lock” ( oil draining into lower cylinder) if one is present.
Any liquid present in a cylinder is indicated
By the abnormal effort required to rotate the propeller, or by the propeller stopping abruptly during rotation.
Never use force to turn the propeller when a hydraulic lock is detected. (The force exerted on the
propeller may be felt on the crankshaft so that a connecting rod may bend or break if a lock is
present).
To eliminate a lock, remove either the front or rear spark plug from lower cylinders and pull the
propeller through. Never attempt to clear the hydraulic lock by pulling the propeller through in the
opposite direction to normal rotation. This tends to inject the liquid from the cylinder into intake
pipe. The liquid will be drawn back into the cylinder with the possibility of complete or partial lock
occurring on the subsequent start.
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Starting the engine:
Turn the auxiliary fuel pump on, if aircraft is so equipped.
Place the mixture control to the position recommended for the engine and carburettor
combination being started. As a general rule, the mixture control should be in the “idle cut
off” position for pressure type carburettors and in the “full rich” position for float type
carburettors.
Many light aircraft are equipped with a mixture control pull rod which has no detended
intermediate positions. When such controls are pushed in flush with the instrument panel,
the mixture is set in the “full rich” position. Conversely when the control rod is pulled all the
way out, the carburettor is in the “ideal cut off” or “full lean” position. Unmarked
intermediate positions between these 2 extremes can be selected by the operator to
achieve any desired mixture setting.
Open the throttle to a position that will provide 1000-2000 rpm.
Leave the pre-heat or alternate air (carburettor air) control in the “cold” position to
prevent damage and fire in case of backfire. These auxiliary heating devices should be used
after the engine warms up. They improve fuel vaporisation, prevent fouling of the spark
plugs, ice formation, and eliminate icing in the induction system.
Energize the starter; after the propeller has made at least 2 complete revolutions, then burn
the ignition switch ‘on’. On engines equipped with induction vibration, turn switch to the
“both” position. When starting an engine that uses an impulse coupling magneto, turn the
ignition switch to “left” position. Place the ignition switch to “start” when the magneto
incorporates a retard breaker assembly.
Do not crank the engine continuously with the starter for more than 1 minute. Allow 3 to 5
minute period for cooling the starter between successive attempts. Otherwise the starter
may be burned out due to overheating.
Move the primer switch to “on” intermittently, or prime with one to three strokes of
priming pump depending on how the aircraft is equipped. When the engine begins to fire,
hold the primer while gradually opening the throttle to obtain smooth operation.
After the engine is operating smoothly on the primer, move the mixture control to the “full
high” position.
Piston engine installations vary considerably and the method of starting recommended by the
manufacturer should always be followed.
Engine speed should be kept to a minimum until oil pressure has built up, and engine should be
warmed up to a minimum operating temperature before proceeding with the required tests.
High power should only be used for sufficient duration to accomplish the necessary checks, since
the engine may not be adequately cooled when the aircraft is stationary. After all the checks have
been carried out the engine should be cooled by running it the recommended speed for several
minutes, the magneto switches should be checked for operation and then the engines should be
stopped.
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Hand cranking:
Extreme care is essential when starting piston engines by hand swinging. Many accidents have
occurred in this way, and both pilots and technicians should be given demonstrations and be
checked out on this method of starting. The engine must always be treated “alive” and no part of the
arms, legs, or body should be moved into the propeller disc at any time. No attempt should ever be
made to start an engine without someone in the cockpit to operate the throttle or brakes assembly,
or without chocks placed in front of the wheels.
Sucking-in:
To prime the engine cylinders, when necessary, the ground crew should stand away from
the propeller, face to pilot and call “switches off, petrol on, throttle closed, suck in”. The
pilot should repeat these words, carrying out the appropriate actions at the same time. The
ground crew should then set the propeller to the beginning of a compression stroke and turn
the engine through at least 2 revolutions. The propeller must be swing smartly down and
across the body, turning away from the propeller and stepping away in the direction of the
movement of the aircraft.
Starting:
The ground crew should set the propeller at the start of a compression stroke, stand away
from the propeller, face the pilot and call “contact”. The pilot should set the throttle for
starting, switch ‘on’ the magnetos and repeat “contact”. The ground crew should then swing
the propeller. If the engine does not start, this ground crew should ensure that the
magnetos are switched off before re-setting the propeller, and switched ‘on’ again before
making another attempt to start the engine.
Blowing out:
If the engine fails to start through over-richness, the ground crew should face the pilot and
call “switches off, petrol off, throttle open, blow out”. The pilot should repeat these words,
carrying out the appropriate actions at the same time. The ground crew should then turn the
propeller several revolutions in the reverse direction of rotation to expel the mixture from
the engine. This will usually entail swinging the propeller up from the 6 o’ clock position,
using the opposite hand. The throttle should then be closed, the petrol turned ‘on’ and then
the observations for starting the engine are repeated.
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Engine starting procedures-turboprop engines:
Prestart procedures:
The various covers protecting the aircraft must be removed.
Engine tail pipes should be carefully inspected for the presence of fuel or oil.
A close visual inspection of all accessible parts of the engines and engine controls should be
made, followed by an inspection of all nacelle areas to determine that all inspection and
access plates are secured.
Sumps should be checked for water.
Air inlet areas should be checked for general condition and foreign material.
The compressor should be checked for few rotations, when the installation permits, by
reaching in and turning the blade by hand.
Starting procedures: Common
Turbo engines may be an electric motor or by an air turbine. Hence external electric power may be
needed to start the electrical starter motor or an external air pressure trolley may be needed to start
the air turbine starter. In multi-engine aircrafts where air turbine starters are used, use an external
air pressure trolley to start on engine and then the bleed air from the started engine can be used to
start the other engine starters.
While starting the engine, always observe the following:
Never energize (electrical) the starter when engine is rotating.
Do not move the power lever of any engine while it is being bled for cross-bleed starting.
Do not perform a ground start if turbine inlet temperature is above that specified by the
manufacturer.
Do not uses bleed air from an engine that is accelerating.
Procedure:
Place the “start selector switch” to the desired engine and the “start arming switch” (if so
equipped) to the “start” position.
Turn the aircraft booster pumps “on”.
Place the fuel and ignition switch “on”.
Position the low rpm switch in low or normal (high).
Make sure that the power lever is in the “start” position. If the propeller is not at the “start”
position, difficulty may be encountered in making a start.
Depress the “start” switch and, if priming is necessary, depress the priming button.
Make sure the fuel pump parallel light corners on at, or above, 2200 rpm and remains “on”
up to 9000 rpm.
Check the oil pressure and temperature. Maintain the power lever at the “start” position
until the specified minimum oil temperature is reduced.
Disconnect the ground power supply.
If any of the following conditions occur during the starting sequence, turn off the fuel and ignition
switch, discontinue the start immediately, make an investigation and record the findings.
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Turbine inlet temperature exceeds the specified maximum (record the observed peak
temperature).
Acceleration time from start of propeller rotation to stabilised rpm exceeds the specified
time.
There is no oil pressure indication at 5000 rpm (for either the reduction gear or the power
unit).
Torching (visible burning in the exhaust nozzle other than normal enrichment) or excessive
smoke is observed during initial fire up.
The engine fails to ignite by 4500 rpm or maximum motoring rpm (whichever is first) and
rpm stagnates or begins to decay.
Abnormal vibration is noted or compressor surge occurs (indicated by backfiring).
There is fuel spewing from the nacelle drain, indicating that the drip valve did not close.
Fire warning bell rings (this may be due to either an engine fire or failure of an anti-icing shut
off valve to close).
Engine starting procedures-turbojet engines:
Pre-flight operations:
Unlike reciprocating engine aircraft, the turbojet powered aircraft does not require a pre flight rump
unless it is necessary to investigate a suspected malfunction.
Before starting, all protective covers and air inlet duct covers should be removed. If possible the
aircraft should be headed into the wind to obtain better cooling, faster starting, and smoother
engine performance. It is especially important that the aircraft be headed into the wind if the engine
is to be trimmed.
The rump area around the aircraft should be cleared of both personnel and loose equipment.
Care should also be taken to ensure that the temperature is clear of all items such as nuts, bolts,
rocks, rags or other loose debris.
A great number of very serious accidents occur involving personnel in the vicinity of turbojet engine
air inlets. Extreme caution should be exercised when starting turbojet aircraft.
The aircraft fuel sumps should be checked for water & ice and the engine air inlet should be
inspected for general condition and the presence of foreign objects. The forward compressor blades
and the compressor inlet guide vanes should be visually inspected for nicks and other damages.
If possible, the compressor should be checked for free rotation by turning the blades by hand. All
engine controls should be operated and engine instruments should be checked for proper operation.
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Starting procedures:
Most of the gas turbine engines are having built-in air turbine starters or combustion type (micro
turbo) starters. Air turbine starters make use of an external source of compressed air to start them
and then rotate the aircraft engine. Combustion type starters make use of either air bottles (built-in)
or electrical motor to start themselves and then rotate the aircraft engine.
If an air turbine starter is used, the engine should start or “light up” then approximately 20 seconds
after the fuel is turned ”on”. If this time limit exceeded, the start should be discontinued and the
trouble should be analysed and removed. If it is micro turbo start, the 20 second interval need not
be observed, since starter operation will discontinue automatically after predetermined time
interval.
Procedure:
Move power lever to ‘opp’ position unless the engine is equipped with thrust reverser. If the
engine is so equipped, place the power lever in the “idle” position.
Turn “on” electrical power to engine.
Turn fuel system shut off switch to fuel “on” position.
Turn fuel booster pump switch “on”.
A fuel inlet pressure indicator reading of 5 psi ensures fuel is being delivered to engine fuel
pump inlet.
Turn engine starter switch “on”. When engine begins to rotate, check for oil pressure rise.
Turn ignition switch “on” after the engine begins to rotate.
Move throttle to “idle” (if engine is not equipped with thrust reverser).
Engine start (light up) is indicated by a rise in exhaust gas temperature.
After engine stabilises at idle, ensure that none of the engine limits are exceeded.
Turn the engine starter switch to “off” position after start.
Turn ignition switch “off”.
Unsatisfactory turbo starts:
Hot start:
Engine starts but the exhaust gas temperature exceeds specified limits. Caused by excessive
rich fuel / air mixture. The fuel to the engine should be shut off immediately.
False or Hung start:
Engine starts normally but the rpm remarks at some low value. The result of insufficient
power to the starter or the starter cutting off before the engine starts self-accelerating –
shut down the engine.
Engine will not start at all:
Engine does not start within prescribed time limit-caused by lack of fuel / insufficient
electrical power / malfunction of ignition system etc. –shut down the engine.
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Engine Fire Extinguishing:
What is ‘fire’?
Fire results from the chemical reaction that occurs when oxygen combines rapidly with fuel to
produce heat and light.
The essentials of fire are
Fuel – a combustible gas, liquid or solid
Oxygen – sufficient in volume
Intensity to raise the temperature of fuel to its ignition point
Kindling point.
Types of fire:
There are 4 classes of fire, each determined by what is burning.
Class ‘A’ fire:
The most common fire that occurs in ordinary combustible materials such as wood, cloth,
paper, upholstery materials, rubbish, etc.
Class ‘B’ fire:
Fire in combustible (inflammable) liquids such as gasoline, alcohol, oil, greases, solvents,
paints etc.
Class ‘C’ fire:
Fire involving energised electrical equipments such as fuse boxes, switches, electrical
appliances, motors or generators.
Class ‘D’ fire:
Fires those are of high intensity that may occur in certain metals such as magnesium,
sodium, potassium, titanium, and zirconium. The greatest hazard occurs when these metals
are in a molten state or in finely divided forms of dust, chips, turnings or shavings.
Caution: (for aviation technicians)
As there may be spontaneous ignition caused by the lubricant and solvents that are used in
maintaining the aircraft, certain materials such as rags soaked with oil or solvents should be
disposed of in airtight cans as these soaked rags are capable of generating sufficient heat to cause
‘combustion’.
Fire extinguishment:
It takes 3 things to start fire: oxygen, heat, fuel.
3 elements of fire: oxygen, heat, fuel.
Principles of extinguishing fires:
Based on the principle of fire triangle, there are 3 ways to extinguish fires. They are
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Cooling the fuel below its ignition (kindling) point
Excluding the oxygen supply
Separating the fuel from the oxygen.
Fire extinguishing agents:
Class ‘A’ fires respond best to water or water type extinguishers which cool the fuel below
combustion temperatures. Class B and C extinguishers are effective but not equal to the cooling /
wetting action of the class ‘A’ extinguisher.
Class ‘B’ fires respond to carbon-di-oxide ( CO2 ), halogenated hydrocarbons (halons) and dry
chemicals all of which displace the oxygen in the air, thereby making combustion impossible. Foam
is effective, especially when used in large quantities. Water is ineffective on class ‘B’ fire and in fact
will cause the fire to spread.
Class ‘C’ fires involving electrical wiring, equipment or current respond best to carbon-di-oxide (
CO2 ) which displaces the oxygen in the atmosphere, making combustion impossible. The CO2
extinguisher must be equipped with non-metallic horns (outlet horns) to be approved for use on
electrical fires.
The reasons for this requirement are:
(i). The discharge of CO2 through a metal horn can generate static electricity which could reignite the
fire
(ii). The metallic horn, if it comes in contact with the electric current would transmit the current to
the extinguisher’s operator.
Halogenated hydrocarbons which are called as “Halons” are very effective on class ‘C’ fire. Carbon
tetrachloride, chlorobronomethane, dibromodifluromethane, bromochloro difluromethane,
bromotrifluoromethane are some of the halons available. The vapours react with the flame to
extinguish the fire. Dry chemicals are effective but have the disadvantage of contaminating the local
area with powder. Also, if used on wet and energized electrical equipment, they may aggravate
current leakage. Water or foam is not acceptable agents for use on electrical equipment as they also
aggravate current leakage.
Class ‘D’ fires respond to the application of dry powder which prevents oxidation and the resulting
flame. The application may be from an extinguisher, soap, or a shovel. Special techniques are
needed in combating fires involving metal.
Manufacturer’s recommendations should be followed at all times. Areas which could be subjected
to metal fires should have the proper protective equipment installed. Under no conditions should a
person use water on a metal fire. It will cause the fire to burn more violently and can cause
explosions. Some of the dry chemicals used are sodium bicarbonate, ammonium phosphate,
potassium bicarbonate etc.
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Extinguishing agents that are not recommended for aircraft use:
Dry chemical extinguisher is very effective in class B and C fires but they leave a residual
dust or powder. This obstructs vision, is difficult to clean up and causes damage to
electronic equipment.
Carbon tetra chloride is no longer approved as a fire extinguishing agent. It produces a
poisonous gas (phosgene) when in contact with hot metals. Soda acid and foam are toxic to
a certain degree and can be corrosive to adjacent materials.
Methyl bromide is more toxic than CO2 and cannot be used in confined areas. It is also very
corrosive to Al alloy, Mg and Zn.
Chloro-bromo-methane, although an effective extinguishing agent, is toxic.
Air borne fire extinguisher that are not recommended to be carried:
Common aerosol can type extinguisher are not acceptable as hand type extinguisher
because they are likely to explode and also inadequate to combat even the smallest fire.
If dry chemical type extinguishers are mounted near the heater vents of the aircraft, they
may also explode if inadvertently exposed to heat.
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Ground Power Units
Introduction:
There are many ground support equipment needed for the operation of the aircraft on the ground.
When the aircraft engines are not operating, there are ground power units to provide pneumatic /
air power, electrical power or hydraulic power to the aircraft either to start the engines of the
aircraft or to carry out functional checks on the aircraft system.
In order to be available for instant use, the ground power units are to be inspected and serviced
periodically and kept in good working condition.
There may be a separate maintenance crew to maintain these ground equipment and ground power
units belonging to electrical, electronic and mechanical stream. It is essential to check the condition
of internal combustion engines so that the sparks or flames are not emitted from their exhausts. In
some power units, the use of flame damped exhausts is recommended.
.Air Starting Trolley
Air starter units are designed to start aircraft engines which are equipped with air turbine
starters.
They can also be used in checks on auxiliary systems, for limited air-conditioning or for de-
icing.
The unit generally consists of a turbo-charged diesel engine, driving a single stage
compressor, mounted on a truck chasses and enclosed by a suitable canopy.
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The compressor delivers a continuous flow of warm, oil-free compressed air.
The engine is completely self-contained and has its own electrical system, starting system
and fuel supply.
A regulating valve controls the delivery of air pressure from 35-45 psi.
A safety valve operates at approximately 50psi.
All instruments, controls and warning lamps are grouped on a control panel.
Operating procedures:
Operating procedures for air starter units will vary according to the particular design, and the
manufacturer’s instructions and recommendations should always be followed. The following
practices would be typical:
Before starting, the unit should be placed on firm, level ground, and the boding lead should
be connected to the aircraft.
After starting the engine, it should be ensured that oil pressure is building up and that all
warming lights are extinguished. The engine should be allowed to warm up for several
minutes.
When the engine has warmed up, the throttle should be opened to check that air pressure
build up to normal operating pressure.
During an aircraft starting operation a consultant check should be kept on the air pressure
gauge, and the starter unit throttle should be adjusted as necessary to maintain operating
pressure without exceeding the maximum permissible starter unit engine speed.
Maintenance:
A record should be kept of engine running hours and engine starting cycles, and maintenance should
be carried out in accordance with a schedule drawn up for the particular equipment.
A daily inspection should include the topping-up of fuel, coolant and oil systems, and a check for
damage, leaks and security of components.
The air delivery hose is generally seamless and lined with silicon rubber and normally has low
temperature flexibility and high resistance to abrasion. However, the rubber will eventually
deteriorate, particularly at the ends; shortening the ends by a small amount (say 2 inches) may
rectify this, but other cracking or damage will necessitate replacement. The life of a hose can be
prolonged by exercising reasonable care in its use, and by avoiding sharp bends, tautness and
twisting.
Inspection of an air delivery hose should be carried out after approximately 50 hours of operation or
600 aircraft starts.
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.Electrical starting trolley
Battery cart or trolley:
Electrical power for lighter aircraft is usually supplied by means of a battery cart.
Such carts contain one or more storage batteries connected to supply 12 volts, 24 volts or 28.5 volts
d.c and having sufficient capacity (ampere hours) to provide several engine starts before recharging.
Battery carts should be kept clean and fully charged. Since they are not used on regular basis, they
are often overlooked and not properly cared for. It is good practice to schedule a regular time for
checking and servicing ground power batteries.
When a battery cart is to be used, the technician must determine that the voltage and capacity of
the unit is compatible with the system voltage of the aircraft being serviced. A 12 volt power supply
cannot service a 24 volt system and a 24 volt supply will severely damage to a 12 volt system if
connected.
A specially designed receptacle is usually installed in the aircraft system to make it impossible to
connect the power supply with wrong polarity (i.e. +, -).
The plug on the power supply cable cannot be inserted into such an aircraft receptacle unless the
polarity is correct. In all cases, the master switch in the cockpit must be off whenever the battery
cart is being connected to the aircraft.
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Mobile Electrical Power Unit (GPU):
All large aircrafts, such as commercial airliners require electrical power when in flight and when in
the ground preparing for flight. The power supplies usually needed is 28 volts d.c and 115/120 volts
400 c/s a.c the required electrical power supply to these large aircrafts either to start up or to check
the systems on ground can be provided by the following 3 methods:
1. APU:
Part of auxiliary power system which are small gas turbine engines that drive generators
(alternators) and also supply bleed air for engine starting and air-conditioning. These units are
expensive to operate and hence the need for other sources.
2. Mobile Power Unit:
Consists of a diesel engine driven or turbine engine driven alternator to produce 115 volts 400 c/s 2
φ or 200 volts 400c/s 3φ a.c power supply. The unit has its own rectifier board to convert and then
regulate this a.c supply into 28 volts d.c. Hence both a.c as well as d.c power supplies are available to
the aircraft from these GPU’s. They are easy to be carried from place to place and aircraft to aircraft.
However, the disadvantages are: it causes air pollution; it produces noise; it also contributes to the
cluster of ground equipment around the aircraft.
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3.Fixed Power Supply Points:
They are at the gate of the airport available to each aircraft. Most large airports are now equipped
with a single, central power station, and electrical power is delivered through cables to the various
terminals on the airport. While transmitting 400 Hz a.c, the line losses are heavy. It is found that a
high voltage of 4160 volt can transmit a 400 c/s supply to a distance of 2-3 miles (3-5 kms) without
serious power losses. This 4160 volt or 400 c/s is reduced to 115 /200 v at the terminal by means of
transformers. Multiple cables are used to deliver this reduced power supply to the aircrafts.
As many smaller airports do not have centralised power stations, the commercial aircrafts have to
make use of either APU’s or Mobile power units. APU’s being expensive, mobile power units are
preferred and they are of immense use in field operations.
Operating procedure & maintenance of GPU’s:
Place GPU firmly on the level ground & apply the parking brake.
Establish the bonding connection between aircraft and GPU.
Start the engine, check oil pressure, check for warnings and then connect the power supply
cable to the aircraft.
Follow the manufacturer’s instruction to supply a.c or d.c to the aircraft.
Before connecting or disconnecting the power lead ensure that the output is switched off to
the power lead.
Maintenance:
GPU’s are inspected daily to check the oil level, coolant level and battery electrolyte level
levels, serviceability of lamps and indicators, and for leaks and security of attachments.
At monthly intervals on electrical quality check to test the voltage and frequency protection
units, phase rotation polarity at the output sockets, and current overload to be carried out.
A record should be kept for these inspections and checks and also a record of GPU running
times.
------------------------------------------------
.Hydraulic test rig or trolley:
The testing of aircraft hydraulic systems requires a controlled and filtered supply of hydraulic fluid at
high pressure and this is normally provided by this special trolley.
A typical hydraulic test rig would have a 100HP (75 kW) electrical motor operating from a 380/440
volt 3 φ power supply. The motor drives a variable delivery hydraulic pump through a gearbox,
clutch and flexible coupling. The output from the rig is about 175 litres/minute at 20MN/m2 (or 38
gallons/minute at 3000 psi), with a filtration of 3 microns.
The hydraulic circuit would function by drawing fluid from the aircraft system through a heat
exchanger and low pressure filter, and returning it to the aircraft system through suitable flow
control valves and flow meters and a high pressure filter; self-sealing, quick disconnect couplings
installed in the aircraft, permit the connection of flexible hoses from test rig to the aircraft system.
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Operating procedure:
The operating instructions printed on the plate attached to the trolley (or contained in a manual
booklet) to be followed carefully.
Before starting the rig, all valves should be closed, and where applicable the aircraft
hydraulic reservoir air pressure is to be checked.
The caps fitted to the outlet points of the hoses to be removed only just before connecting
and to be put immediately when they are disconnected.
After starting the electrical motor, the pump can be brought into operation by operating the
clutch and read the pressure on the pressure gauge of the rig. When the main rig flow
control valve is opened, the rig will form part of the aircraft system. Now tests can be carried
out on aircraft hydraulic system.
Maintenance:
Carry out regular quality check of the fluid samples to prevent the contaminated fluid being
circulated.
The rig should be kept clean and free from leaks.
The filter should be cleaned or removed regularly.
All gauges must be periodically calibrated.
The condition and functioning of all electrical equipment should be checked.