AVIATION SAFETY By Umar Sharif

CONTENTS PAGE

Pages 3 7: Fire Protection Pages 8 - 13 : Aircraft Pressurisation Pages 14 17: Emergency Evacuation & Seating Pages 18 22: Fuel Tanks Pages 23 27: Flight Management Computer & Components Page 28: Bibliography Page 29: Tips & Useful Resources

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FIRE PROTECTION- INTRODUCTION

In this topic we will be covering some of the devices and safety components which help make a aircraft safe from fires but also systems which are used in the even of a fire such as: Automatic fire extinguishers Two shot systems Fire Wire and Overheat detection wire Cargo Bay Fire Protection

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AUTOMATIC FIRE EXTINGUISHER A example of a automatic fire extinguisher is the fire extinguisher in the toilet waste bin. The reason for a fire extinguisher being there is in case some one smokes or puts something that may cause a fire in to a toilet waste bin. If there is something in the waste bin which may cause a fire the fusible tip will break allowing the fire extinguisher to release its content which should extinguish the fire. However the crew are still notified of the fire and will attend with a fire extinguisher to be sure that the fire has been put out completely. On the right is a picture of a fire extinguisher from a Boeing 777

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TWO SHOT SYSTEM The two shot system is a system which allows the crew to have two chances to extinguish a fire. The system is very simple and depending on the aircraft may either have a rotating knob or handle which allows the crew to use it. For example if it is a knob the crew would rotate it either clockwise or anti-clockwise first this will release the first shot of extinguisher if this fails to put out the fire the crew would then rotate the switch in the other direction to allow the second shot hence the name two shot system. Depending on what aircraft you mostly have a two shot system on each engine but on some aircraft you may find both engines sharing the same two shot system so if the crew uses both shots on one engine and the other engine sets on fire they will not have any shots left.

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FIRE WIRE AND OVERHEAT DETECTION WIRE Fire wire and overheat detection wire are the same type of wire both are filled with a chemical and when the resistance of the wire changes due to heat the alarm will trigger.

The two loop fire wire system is a simple system in which where ever there is one fire wire another is ran parcel to it this is to ensure that the crew are not given a false alarm due to a faulty wire. If only one wire has a change in resistance the crew will receive a amber light in the flight deck but if both wires have a change a red light and a alarm will sound on the flight deck.

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CARGO BAY FIRE PROTECTION The cargo bay of a aircraft is one of the more likely areas of there being a fire due to the things people may put in there luggage. All cargo bays have fire detection systems these work in the way where a source will emit light then when the light is reflected on to the photo electronic cell if there is a fire the fumes will have disturbed the light and the reflectors will pick it up if all the light is reflected clearly on to the photo electronic cell there will be no alert.

In the case of there being a disturbance to the light due to the fumes a alarm and light will sound in the flight panel to notify the crew of the issue.

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AIRCRAFT PRESSURISATION

Aircrafts are pressurised to provide passengers and crew with air to breathe when at high altitudes due to the air being a lot thinner higher up in the atmosphere we would struggle to breathe. In the next few pages we will be covering how an aircrafts pressurisation system works. Some of the topics we will cover are: Environmental Control System Engineering Panel Distribution System Human Ear Depressurisation

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ENVIRONMENTAL CONTROL SYSTEM The environmental control system works in the way when the air comes in to the system some of it goes in to the heat exchanger and some bypasses to the cabin temp control valve. They are two heat exchangers both located on in a ram air exhaust inlet the air is passed through the heat exchanger the second heat exchanger is only used if the air is to hot the air then goes to the air cycle machine which is capable of cooling the air to 2 degrees Celsius it then goes to a water separator which removes moisture from the air the air is then passed on to the mixing chamber.

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ENGINEERING PANEL The engineering panel allows us to see the temperature of the ducts and the zones of the aircraft. An aircraft is usually divided into four zones. The duct an zone sensors then provide feedback to the control unit which then adjusts the temperature VIA the conditioned air manifold and the trim air to get the temperature required.

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DISTRIBUTION SYSTEM This system mixes the air and releases it in to the fuselage this is done by two duct pipes which both run alongside the fuselage to the top where the recycled air is mixed with conditioned air in the zone distribution manifold which releases the air in to the fuselage the air then travels to floor which has floor vents or dado grills the air is then either recirculated into the system or released through the freight hold VIA pressurisation outflow valves.

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HUMAN EAR The human ear is a sensitive and vital part of the human body to allow us to hear. It can be damaged very easily and can also be affected by sudden pressure change which is why aircrafts take off quicker then they land this is to ensure minimal or no damage is done to the ear.

When taking off an aircraft can cover 600 F.P.M but when landing the figure is halved to 300 F.P.M to ensure no damage is done.

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DEPRESSURISATION Aircrafts are pressurised to a great extent and if they are not depressurised when they have landed and someone opens the door it will blow open and may cause damage therefore on the landing gear there are sensors which tell the aircraft if it is on the ground the aircraft then depressurises itself and the doors can be open.

This is due to the pressure difference of the aircraft to the pressure outside it is also known as differential pressure.

On the right is a picture of a aircraft which decompressed suddenly.

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EMERGENCY EVACUATION & SEATING

In this topic we will cover how to evacuate a aircraft in an emergency and the harness aircrafts have and who for. The following subjects will be covered in this section: Emergency Slide Crew Harness Passenger Harness

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EMERGENCY SLIDE A emergency slide also known as a evacuation slide is a requirement for all commercial aircrafts if the door height is 1.8M or 6 Feet above ground level the purpose of the slide is to allow quick and safe evacuation in a emergency. The slide is inflated with air when it is needed the FAA state that the aircraft has to be completely evacuated within 90 seconds and by only using 50% of available exits so a slide needs to deploy and inflate within 10 seconds. On B747 a slide can be deployed and inflated within 5 7 seconds depending on the conditions (temperature and wind).

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CREW HARNESS The flight crew have a 5 point harness to ensure that they are held in during a emergency or any problems during flight the flight crew also have electrically moving chairs to allow easy access to the chair and also have a guide on where to position your chair for the best view of surroundings.

The cabin crew how ever have a 4 point harness and a folding chair this is to save space and allow room to move in the aircraft it is usually located near a emergency exit.

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PASSENGER HARNESS The passengers harness is just a single belt which runs along the waist of the passengers the reason for there being such a basic belt for passengers is due to weight as if all passengers had 4 point belts this would dramatically increase the weight of the aircraft.

Before flight passengers are shown how to brace and prepare themselves in a emergency to ensure there safety different airliners have different videos. The cabin crew will also assist passengers in emergency and instruct passengers on what to do.

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FUEL TANKS

In this topic we will be covering the different type of fuel tanks and the perks the system has. The following subjects will be covered

Integral Fuel Tank Flexible Fuel Tanks or Cells Pilots Fuel Management Panel Vent Flow Valve Cross feed & Refuel System

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INTEGRAL FUEL TANKS Integral fuel tanks are designed to be part and support the structure of the aircraft they are then sealed in to hold fuel. Due to them being part of the structure they can never be removed for inspection or repairs of even for servicing the tank.

Therefore panels have to be provided to allow inspection or repairs to these fuel tanks.

Most fixed wing aircrafts usually store the fuel in the wings and some long haul aircraft may even store fuel in the belly and tail plane.

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FLEXIBLE FUEL TANKS OR CELLS Flexible fuel tanks are also known as fuel cells they are usually reinforced rubberized bags and are installed in the structure to accommodate for the weight of the fuel.

These types of fuel tanks are usually used in fighter jets. However through use of these tanks the material may crack.

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PILOTS FUEL MANAGEMENT PANEL The pilots fuel management panel allows the pilot to see the level of the fuel and if the boost pumps are functioning correctly it also allows the pilot to cross feed the fuel which we will cover on the next page. The panel also shows if there is any fault with the engine and allows to shut the engines off.

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CROSS FEED & REFUEL SYSTEM Aircraft tanks are not able to transfer fuel during flight but if one tank is overloaded and the other running low the pilot can allow the system to cross feed what this means is that engine one can accept fuel from engine 2s tank but the fuel cannot shift tanks during flight.

The refuel system is simple for example on the ground if the aircraft has had 100 litres in one tank 120 litres in the other and the pilot wants to level it out to 110 litres in each simply the pilot just has to set the under loaded tank to refuel set the amount and then either by him self or by a colleague switch on the boost pumps the fuel will then transfer and level out.

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FLIGHT MANAGEMENT COMPUTER AND COMPONENTS

In this topic we will summarize what the flight management computer is and what components it uses to function. Below are some of the components we will discuss: Flight Management Computer Navigation Database Flight Plan Position Determination

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FLIGHT MANAGEMENT COMPUTER The flight management computer also known as the (FMS) is a very important system in airliners avionics it is a computer that completes many of the tasks of the flight crew easing off the workload on the flight crew it covers various tasks. One of the primary tasks of the FMS is to manage the flight plan it is able to do this by using various sensors such as GPS or IRS which is often backed up by radio navigation.

The FMS is controlled by a control display unit which is a small screen with a keyboard or touch screen.

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NAVIGATION DATABASE All FMS contain a navigation database (NDB) this database consists of various elements from which thee flight path is produced. The database is usually updated every 28 days in order to make sure it is up to date and all elements are and contents are current.

Some of the contents a NDB consists of are: Waypoints/Intersections Airways

Airports Runways Holding Patterns

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FLIGHT PLAN The flight plan is usually calculated on the ground by either the pilot or professional dispatcher. It is entered by using the control display unit by either typing it in or by using a saved library of flight plans.

Before flight other data is inputted into the FMS such as gross weight, fuel weight and centre of gravity.

Then the pilot may adjust the flight plan for varied reasons VIA the FMS. The flight plan generally appears as a line with other airports and waypoints displayed.

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POSITION DETERMINATION Once the aircraft is in flight the FMS has a task of to calculate where the aircraft is and the accuracy of the position. Depending on the FMS of the aircraft old simple FMS only use one sensor which is GPS more modern FMS use more sensors in fact as many as possible these may consist of GPS, IRSs, VORs and more.

The FMS continually cross checks with various sensors to determine a single position and accuracy of the aircraft.

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BIBLIOGRAPHY

http://en.wikipedia.org/wiki/Evacuation_slide#Inflation_systems http://www.boeing.com/commercial/aeromagazine/articles/2011_q4/4/ http://en.wikipedia.org/wiki/Fuel_tank Class handouts and notes. Please note I do not own any pictures and do not mean to breach any copyrights.

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TIPS & USEFUL RESOURCE Tips to help pass assignments are to revise what you learnt every day before going to sleep also to sketch all drawing and look over them every night and on the morning of your assignment. The most useful resource are your class notes followed by your class handouts so ensure you take down as many notes as possible also avoid using the internet to revise as most sites are made by someone and the information may be incorrect or irrelevant. Finally best of luck with all assignments and I hope this book has served its purpose of helping you pass your assignments.

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Aviation safetyContents pageFire protection- introduction Automatic fire extinguisherTwo shot systemFire wire and overheat detection wireCargo bay fire protection Aircraft pressurisation Environmental control system Engineering panelDistribution systemHuman earDepressurisation Emergency Evacuation & SeatingEMERGENCY SLIDECrew harnessPassenger HarnessFuel tanksIntegral Fuel TanksFlexible fuel tanks or cellsPilots Fuel management panelCross feed & refuel systemFlight management computer and componentsFlight Management ComputerNavigation DatabaseFlight PlanPosition Determination BibliographyTips & useful resource