IntergratedSecondary Flight Display (iSFD) is an instrument developed by MEGGIT Avionics, comprisingsolid-state sensors and micro-processor system, which are design to measure anddisplay critical flight information such as attitude, altitude, airspeed andheading of the aircraft using a single 3ATI display unit. iSFD is installed in cockpit to serve as a backupnavigation instrument in the event of glass cockpit instrument system failuredue to faulty equipment or loss of aircraft electrical power. iSFD installationeliminate the need to use multiple electromechanical cockpit standby instrumentwhich is prone to mechanical failure. iSFD application include in commercial,military and rotary wing platform REFUsuallyiSFD will be powered by aircraft auxiliary power unit (APU) in the event of permanentor partial loss of primary power source in aircraft. Due to economical purpose,concern has arisen in aviation customer, demanding iSFD to provide its ownauxiliary power unit in the future.
Previous year student group have been requestedby MEGGIT Avionics to design an external battery module which will be used topower up iSFD in the event of power loss. However, there are certain limitationin achieving objective of this project. Startingas proof of concept, this project is continued to further develop and evaluate theexternal battery module for iSFD.Inthis report, adaptation of various part of the external battery module designand future improvement on design are recorded and discussed in details.
Batterieshave been widely used in aviation industry since the beginning of planehistory. During earlier age of aviation, electricity was mostly used to ignitethe airplanes engine. As technology progress, more advanced airplanes and jet aredeveloped and equipped with a sophisticated electrical system. While enginesable to serve as generator and provide electricity, batteries are required toprovide electricity before the engine started and serve as a part of ignition systemin the engine.
This battery also serves as backup power in the event of enginefailure. Battery used for these purposes are called main battery. In most ofthe advanced airplanes, another battery usually installed to serve as auxiliarypower unit (APU).
The fundamentalin batteries operation is converting chemical energy to the electrical energy.This process occurs through electrochemical discharge of the reactant. However,they are limited time in converting this energy since reactant can be depletedand unable to supply electron. Batteriesthat unable to restore their reactant are called primary batteries. Some of thebatteries have the capability to restore their reactant to its initial state bycharging it through direct current. These batteries are called secondary batteries.In airplanes, secondary batteries are widely used as it able to be usedmultiple time through a cycle process of charge and discharge.
Thechemistry of the battery used in airplanes are usually lead acid, nickel cadmiumor lithium. The battery used are big in nature since its consisted of multiplecells connected in a series-parallel connection to give desired operationrequirement. Batteries are rated based on their nominal voltage and capacity.
Battery with 1000mAh capacity will have a runtime of 1 hour before completelydischarge when discharge with 1A. This discharge rate is equivalent to 1C. Subjectingbattery to a discharge rate of 2C means battery are discharge with 2A and willhave a runtime of 30 minutes before it is completely discharge.
High rate cell canbe achieved by minimizing the internal resistance of the cell which highlydependent on the internal construction of the cell itself. Theuse of lithium ion battery in aviation is quite popular due to energy densitythat it can offer. Higher energy density means, more power can be supplied witha smaller battery. Space required for battery installation is small as some ofthe battery size can be similar to the size of car battery. Total weight of theaircraft can be reduced leading to reduce in airplanes fuel consumption. Lithiumion battery also have excellent life cycle, faster recharge time and require minimalmaintenance compared to nickel-cadmium battery.
Boeing,an airplanes manufacturing company have been knowingly used lithium ion batteryin their airplanes, B787. However, due to accident of thermal runaway of the B787battery in 2013, concern regarding the safety of using lithium ion battery in aviationarises, making Airbus to drop the use of lithium ion in their A350 fleet. Immaturetechnology of lithium ion lead to further development in minimizing the risk ofthermal runaway in battery as year progress. Saft, a battery-maker company has succeededin developing more stable lithium-ion battery, making Airbus to deliver their firstA350 equipped with lithium ion battery in 2016.