Skyhawke Hanger Flashcards
What is the purpose of a large a/c electrical system?
Generate, regulate and distribute electrical power, same as a light a/c.
What differences are there between light and heavy a/c electrical systems?
More than one system (for redundancy) and can be a mixture of AC/DC circuits.
AC more common, largely due to lightweight alternator attached to each engine and greater power demands. They also have smaller gauge wire.
What purposes are fuses, CB and overload switches?
Prevent current overload.
Fuses melt, CB pop (reset once), overload switches are on/off switches.
What is an essential bus?
System where electrical power supply is routed through a common bar, which is attached to various electrical components.
Purpose is so that electrical systems are broken down into channels and therefore prioritised in case of reduced supply of power.
What 3 types of bus bar are there?
Parallel, split or split-parallel.
What use is DC power? What is the major problem with DC power in a/c?
Is the way batteries are charged, but also powers some components. However, AC power is supplied so is rectified by using full wave rectifier.
DC circuits have own bus bar so can be isolated from AC circuits.
Is AC possible from DC?
Yes, if necessary can be done by operating a static inverter from DC battery.
What must be done before AC generators can be connected in parallel?
Output voltage, frequency and phase of rotation of all generators are the same.
Will an emergency lighting system work in case of electrical failure?
Yes, needs to be armed and is auto activated.
What purpose is a CSD?
A constant speed drive is required to produce a constant frequency power supply of approx 400hz.
An alternator output frequency is determined by rotation of armature which is driven by the engine, which does not operate at a constant speed. Hence the need for a CSD (works of CFF flyweights balanced by springs).
What is the most common CSD used?
Hydro mechanical.
Mechanical governors maintain rotation speed for this type.
What should happen in case of generator/gearbox malfunction? (In terms of CSD)
Disconnect engine drive from CSD by pulling “GEN DISC” switch. Once disconnected can’t be reset.
Side note) pull switch activates solenoid which pulls dog clutch switch open, breaking connection.
What is the CSD/generator combo called on Airbus/Boeing?
Integrated drive generators (IDG) Boeing.
Integrated constant speed drive (ICSD) Airbus.
Purpose of aircon and pressurisation system?
Is cargo compartment pressurised?
Supply conditioned air for heating/cooling of cockpit/cabin & a safe/comfortable environment.
Some compartments (avionics) require aircon to prevent condensation from heat build up.
Cargo compartments are usually pressurised (but not always air conditioned). Can be air conditioned for animals.
What is the approx cabin altitude? What is the issue with this?
How is the cabin pressurised? At what rate?
8000ft.
Pressure differential between cabin and outside pressure altitude. As 8000ft is standard, further a/c climbs the greater the differential.
Cabin air outflow (outflow valve centrally located in cabin) less than air con inflow (usually from engines— air con unit) until they match at desired cabin pressure. This is normal ops. Can’t be excessive so that passengers feel uncomfortable (cabin pressure controller… determined by rate controller).
0.26PSI/min climb, 0.16PSI/min descent.
To certify, cabin PD max must be doubled without failure.
What is the target PD?
What happens if over pressurisation occurs?
What about if cabin px
8.9PSID.
A positive pressure relief valve opens automatically at a predetermined value set on the ground so cabin pressure never exceeds a given value.
This is not allowed to happen so a negative pressure relief valve is set at 0.5PSI so cabin pressure is never below the outside pressure.
These are located at the rear of the a/c.
What is a dump valve? Where is it located?
What components make up the safety valve?
Dump valve drops any residual pressure on landing, activated by landing squat switch (WOW) but can be manually activated too. Located front of a/c. X3 Dump (emergency depressurisation), negative/positive pressure relief valve.
What can be selected on the cockpit environmental system panel?
Simple as OFF, NORMAL, RAM.
Can set different temperatures in cockpit/cabin sections.
Cabin pressure controller, rate selector, landing altitude selector, baro pressure selector, emergency controls and warning lights in conjunction with CWP.
If APU a an operate the panel this option will be available.
Describe how a refrigerant works to cool a cabin
Heat can be added/removed from a refrigerant without changing its temperature during a state change.
As a refrigerant turns from a liquid to vapour in doing so requires heat energy so absorbs this heat from the cabin. This gas then turns back into a liquid, giving off heat but outside the a/c cabin and returns to the a/c cabin to absorb more heat in a continuous cycle.
Name the most common refrigerant used in a/c. Why is this the most common?
R-12 (AKA Freon-12, Genetron-12, Isotron-12, Ucon-12).
It is a stable compound at low and high temperatures and does not react with any substance in the air con system (ie rubber for hoses/seals). Is colourless and basically odourless.
Note: is a different substance if the number is different.
What two types of O2 systems are available in an emergency?
Give a brief explanation of both
Continuous flow is the simplest. Flow is immediate and continuous.
Pressure demand has a diluter-demand regulator which provides O2 but only as person breathes in, prolonging duration of O2 supply. It also dilutes the O2 with suitable amounts of atmospheric air at all altitudes below 34000ft further prolonging supply.
Where is the diluted-demand system more commonly found?
What should the O2 system be set to in case of smoke/contaminate in the cockpit?
On the flight deck as prolonged supply is more beneficial until a suitable altitude has been reached. Continuous for PAX.
Should be set to 100% O2.
What are the advantages/disadvantages of a chemical O2 system?
What about a gaseous?
A: Lightweight, less maintenance, less equipment (less space consumed)
D: Greater fire risk, not tamper proof, won’t turn off
Gaseous are the opposite.
What systems are onboard to protect against fire?
Overheat, smoke and fire protection systems.
Where fire protections can be broken into detection and extinguishing systems.