B1-05.13 SOFTWARE MANAGEMENT CONTROL

• Software is used to provide programming information in all computer-based aircraft systems.

Software Use Examples

• Engine control systems
• Bleed air control systems
• Power generation/control systems
• Fire protection systems
• Aircraft instrument displays
• Software controls navigation/flight management systems, requiring continuous updates due to changing navigational needs like airline routes, air traffic control, and waypoints.
• Aircraft's Built-In Test Equipment (BITE) uses software to communicate with other systems for testing and problem identification.
• Multifunction Control Display Unit (MCDU) is programmed with software to communicate with multiple systems to update data, test, and identify faults

Software Control: Software Levels

• Software is assigned a level (A-E) based on its potential for safety-related failures and must meet specifications based on the assigned level.
• Software levels align with DO-178C criteria, "Software Considerations in Airborne Systems and Equipment Certification", jointly prepared by RTCA SC-167 and EUROCAE WG-12.

Software Level Examples

Level A - Catastrophic:

• Failure prevents safe aircraft operation/landing, with a probability of failure less than 1 in 10⁻⁹/flight hour.
• Affected systems include flight control computers, fly-by-wire, full authority digital engine control, flight displays, and air data systems.

Level B - Hazardous:

• Failure results in serious/fatal injuries with a probability of failure less than 1 in 10⁻⁷/flight hour
• Affects autopilot, autothrottle, ice protection, standby flight displays, instrument landing system, and landing gear control.

Level C - Major:

• Failure results in discomfort/injuries with a probability of failure less than 1 in 10⁻⁵/flight hour.
• Affects navigation systems (GPS), yaw damper, and environmental control systems.

Level D - Minor:

• Failure results in inconvenience with a probability of failure less than 1 in 10⁻³/flight hour.
• Affects the flight data recorder, data acquisition system, and cabin lighting.

Level E - No Effect:

• It has no effect with no specified probability of failure.
• Deals with in-flight entertainment.
• Most software is treated like an aircraft component for certification, defect investigation, and control procedures.

Software Types

• Two main types of aircraft software exist: Field-Loadable Software (FLS) and Preloaded/Resident Software.

Field-Loadable Software (FLS)

• It is used to describe software rather than its medium.
• It includes data tables which can be loaded by maintenance staff without system removal

FLS Characteristics

• Has its own unique part number
• May be an aircraft part
• Part number is verifiable by electronically accessing hardware memory
• Does not change target hardware part number
• Is uploaded regardless of current software state and can overwrite previous versions.

Preloaded or Resident Software

• Cannot be changed without system or component removal from the aircraft.
• Software or programming updates require unit removal and workshop reprogramming.
• Certain aircraft components/computers have no software changes for long periods.
• Some manufacturers may not want the information released.

Loadable Software Aircraft Part (LSAP)

• It is software considered part of the approved aircraft design, requiring documentation like EASA Form 1 or FAA 8130-3.

Non-Loadable Software Aircraft Part or Aeronautical Database

• It is field-loadable software not part of the certified configuration, used for navigation, flight planning, etc.
• Updated without modification approval or STC but requires rigorous configuration control.

Databases

• There are 2 significant types of databases: those that are aircraft parts (LSAP) and those which are Aeronautical Databases
• The distinction between the two does not lie in the technologies and loading methods used, ut in their regulatory status:

Types of Databases

• Model/Engine Database (MEDB) is LSAP software defining a customized performance database for navigation.
• It includes performance values like fuel flow, drag factor, manoeuvre margin, minimum cruise time, and climb rate.
• Aeronautical Database (ADB) is not classified as an aircraft part and is referred to as non-LSAP.
• Navigation Database (NDB) provides navigation and route information for the FMS.
• The NDB is replaced every 28 days, containing current and previous databases.

Operator Modifiable Software (OMS)

• OMS consists of User-Modifiable Software (UMS) and User-Certifiable Software (UCS).
• It allows operators to modify a system function to suit preferred operational or local conditions.
• A UMS partition is provided within the software.

User Modifiable Software (UMS)

• Software is modified by the aircraft operator without certification authority or manufacturer review.
• Modifications can include data and/or executable code changes for systems like ACARS, ACMS, SATCOM, and IFE.

User-Certifiable Software (UCS)

• Operators or designated parties modify UCS software according to approved guidelines.
• Changes to UCS need certification approval.

Operational Program Software (OPS)

• Contains program instructions for a Line-Replaceable Unit (LRU), with each version having a unique software part number.

Operational Program Configuration (OPC)

• OPC is software that determines the function of the LRU and eliminates the need for pin programming.

Aircraft Configuration List (ACL)

• It is a list of modules/LRUs using LSAPs applicable to a specific aircraft, found in various documents or tracking systems.

Software Media

• It transports/distributes software for user equipment installation.
• It comes in forms like discs, memory cards, tapes, or via the internet and may contain numerous LSAPs/Aeronautical Databases.

Software Version

• Specifies the software item at a revision status, with major and minor version designations like A.BB, where A is the major version and BB is the minor.

Target Hardware

• Identifies hardware (LRUs/modules) for loading new FLS.
• Examples include Enhanced Ground Proximity Warning System (EGPWS), Flight Control Computer (FCC), and Flight Management Computer (FMC).

Target Hardware for LSAP

• Display Electronics Unit (DEU)
• Flight Management Computer (FMC)
• Flight Control Computer (FCC)
• Digital Flight Data Acquisition Unit (DFDAU)
• Digital Flight Data Acquisition Management Unit (DFDAMU)
• Auxiliary Power Unit (APU) and Electronic Control Unit (ECU)
• Electronic Engine Control (EEC).
• Software updates like NDB, TDB, and MEDB should come from a source acceptable to the Target Hardware Manufacturer.
• Transport Storage Media should identify the modified software, originator, and quality markings.
• Operators are responsible for confirming software authenticity, performance, and accuracy, with a recommended "confidence" check.

Software Data Loading with Data Loaders

• Software updates and data loading requires a data loader.
• In ROM, PROM and EPROM systems are not capable.
• Data loaders connect to the FMC system or a data bus coupler and may be portable or integrated into the avionics system.

Data Loaders

• ADLs (airborne data loaders)
• PDLs (portable data loaders)
• Portable Maintenance Access Terminals (PMATs), which also provide data loading and fault-recording capability.
• Software is downloaded into aircraft systems using a data loader, offering high-speed transfer via 3.5-in. disc (1.44 MB) or CD-ROM (700+ MB).
• Data loaders can be permanently fitted or external devices and are typically used with the FMC.
• Loading software into an aircraft always requires following procedures defined by the operator and the Aircraft Maintenance Manual.
• Correct loading is important.

FLS Loading and Certification

• FLS is loaded using a PDL, ADL, or workshop data loader.
• Software is verified onboard.
• FLS loading should be recorded in the Aircraft Configuration List (ACL).
• A Certificate of Release to Service by an authorized Line/Base Maintenance Certifying Staff is required after LSAP loading.

Electronic Distribution of Software (EDS)

• FLS moves from the producer/supplier to a remote site (operator) without physical media.
• Has advantages like speed and removal of physical media.
• A "confidence" check is recommended to ensure that changes satisfy their intended use.

Field-Loadable Software Procurement and Documentation

• LSAP, databases, and UMS come with the new aircraft in target hardware and media sets.
• Target hardware part number does not indicate the loaded software part number when replacing LRUs.
• Procured LSAP is obtained from an approved source using the specified part accompanied by a JAA Form 1 or FAA 8130-3.

FLS Storage Media Handling

• Storage media should be sealed in dust- and lint-free material in a closed box, clearly labelled as containing software media, and avoid:

• moisture, dust, and airborne contaminants

• magnetic fields

• direct sunlight

• temperature change greater than 20 °C/hr

• temperatures outside -20 to +50 °C

• X-ray

• magnetic/electromagnetic sources

• Defective FLS/storage media should be quarantined for disposal.

Replication of FLS

• LSAP copies are made using the aircraft Type Design Organisation-approved FLS storage media replication process.
• It is recorded in an Aircraft Software Replication Register and traceable to the original source.
• A copy of the release documentation should accompany all LSAP storage media.
• Operators must have procedures to determine the equipment/software configuration of each aircraft.
• Operators involved in FLS procurement, modification, and embodiment should produce a documented procedure within their company procedures, Maintenance Management Exposition (MME), or equivalent describing their compliance means.
• The procedure should cover the complete cycle, from procurement to subsequent testing/release to service which should be included in the internal audit program.

Case Study

• Changing aircraft software can affect the operating characteristics of the aircraft.
• It may affect engine, navigational, and flight control systems.