Chapter 1 Flashcards
What are the sources of aircraft power?
- Batteries fitted to the aircraft
- Batteries connected on the ground
- AC generators
- Ground power generators
What are batteries primary and secondary function on an aircraft?
- Primary function: is to provide power when the generators aren’t operating
- Secondary function: are for maintenance such as refuelling and engine starting.
What are secondary cells in batteries?
Chemical changes in batteries can be reversed, the reversing is known as charging enabling the battery to be used again.
What are primary cells in batteries?
Will discharge electrical energy only once, battery cannot be used when the life is drained.
What is the nominal output for a battery in an aircraft?
24v DC
When are primary and secondary cell batteries used on aircraft?
(Primary are rarely used, they are used on items that are on the aircraft for a short time.)
(Secondary cells supply high currents for things such as starting the aircraft.)
What are the 2 types of secondary cell batteries?
Lead acid cell - rarely used anymore Nickel cadmium (alkaline) - popular for aircraft
What is the main benefit of a nickel cadmium battery?
Can be left discharged, or partially charged without causing damage
What are the colour codes for alkaline and acid batteries?
Alkaline - light blue
Acid - pink or green
What are the potential hazards for batteries?
- Electrolytes are highly reactive and corrosive
- Can give off hydrogen which is explosive
- Rise to high temperatures or fire
What are the maintenance tasks on a battery?
- Voltage checks
- examination
- replacement
When should a battery be replaced?
- Damaged -State of charge is poor -after a pre determined time
What are 5 tasks which should be carried out before transportation?
- Examine for damage or leaks, -Terminals are protected. -device is firmly attached. -Correct lifting techniques. -Correct document set
What are the 2 most common electrolytes in batteries?
Potassium hydroxide (alkaline) Sulphuric acid
What are the dangers with battery electrolytes?
Chemical burns to skin
Dangerous to eyes
Destroy clothing
The steps for alkaline and acid spills are very similar, Describe the steps?
Neutralise the electrolyte, clean up the activity, restore surface protection and carry out a final inspection.
What electrolytes are used to neutralise acid and alkaline spills?
Acid spill - bicarbonate of soda
Alkaline spill - chromic acid
Why are on-aircraft voltage checks carried out on aircraft?
Because there constant use poses a drain on the charge so they need to be checked
Why do batteries experience thermal runaway?
- Separator breakdown from ageing
- Constant loss of electrolyte
- internal short circuiting
- overcharging
What are the points in the thermal runaway diagram?
A decrease in resistance leads to a increase in current, this leads to an increase in temperature which leads to a further drop in resistance and so on
What are the 5 types and bus bar and what is each used for?
- battery bus bar is used for battery connection
- vital bus bar is used for emergency stuff like fire extinguishers
- essential bus bar is used for fuel pumps
- non-essential bus bar is used for things that’s aren’t essential
- main AC bus bar is used for powering most of the aircraft
What is used to stop people inserting another fuse when you remove one to carry out maintenance?
Yellow dummy fuse provides warning
How can circuit breakers have circuits isolated during maintenance?
They can be manually tripped, also they can be held open with coloured clips, ty wraps or tags to warn that maintenance is being carried out
What are the 3 primary power sources for aircraft?
- aircraft generators
- ground powered units (GPU) or wall mounted external power
- APU
What does a Generator control unit (GCU) do?
Regulates output voltage and monitors output for fault conditions
What faults are monitored by the Generator control unit (GCU)?
- over voltage
- under voltage
- over frequency
- under frequency
What are secondary power sources on aircraft?
- Transformers
- Transformer rectifier units (TRU)
- Inverters
What are the 2 types of inverters?
- Rotary (gives 3 phase ac output)
- static ( gives single state output)
What is load shedding?
An emergency distribution system which ensures only vital and important loads are powered, can be done manually or automatically.
What systems are used as an emergency power supply system?
- Main battery
- Emergency battery
- static inverter
What are the 4 types of ground power units?
- petrol engines
- Diesel engines
- Electric/electrical GPU
- trolley accumulator
What would the warning be when an electric/electric GPU is in use?
DISCONNECT AIRCRAFT EARTH LEAD BEFORE APPLYING GPU
What is primary bonding?
Primary bonding is when one piece of metal is attached to another which bonds the system.
What are secondary bonds?
Similar to primary but are used for surfaces which don’t normally carry current
What are the 4 categories of internal lighting?
- Cockpit
- cabin
- servicing
- emergency
What is a GTLS and why is it dangerous?
Gaseous tritium light source is an emergency light and is radioactive and therefore is a hazard
What are the 5 types of external lighting?
- Navigation lights
- Anti collision lights
- formation / station keeping lights
- search / landing / taxi lights
- downward identification light
What colour lights are fitted to the port, starboard, tail. And what are the angles of each light?
- port (red), 110 degrees
- starboard (green), 110 degrees
- Tail (white), 140 degrees
How are the navigation lights used to tell the direction an aircraft is flying?
A maximum of 2 lights are visible at any angle so the direction is obvious to tell even at night
What are the 3 states of the downward identification light?
STEADY/OFF/MORSE
Why is MORSE used on downward identification lights?
Used to communicate with people on the ground in morse code.
