Software Management Control Quiz

Software Management Control (5.13)

• Restrictions apply to software management and control (Level 2)
• Airworthiness requirements for software management and control (Level 2) are described
• Possible catastrophic effects of unapproved changes to software programs (Level 2) are described

Classification of Aircraft Software Systems

• Software is used in aircraft systems to provide programming information to computers
• Software is used by all computer-based systems: Engine control systems, bleed air control systems, power generation and control systems, fire protection systems, aircraft instrument displays.
• Aircraft rely heavily on computer software for navigation and flight management systems requiring continuous updates
• Changes to airline flight routes, air traffic control, and waypoint positions drive need for updates

Multifunction Control Display Unit (MCDU)

• Programmed with software to update or input data and test/identify faults
• Software also communicates with multiple systems

Software Control

• Aircraft equipment requiring software is assigned a level based on the severity of potential software errors (affecting safety, crew, and passengers)
• Software levels are assigned using DO-178C Software Considerations in Airborne Systems and Equipment Certification jointly created by RTCA SC-167 and EUROCAE WG-12
• Factors to consider regarding Software and Data inclusion regarding design, production, flight and maintenance

Software Levels

• Software is assigned a level (A, B, C, D, or E) based on potential safety-related failures and strict specifications for probability of failure
• Danger levels are associated with catastrophic failure (<1 in 10-9/flight hour), hazardous failure (<1 in 10-7/flight hour), major failure (<1 in 10-5/flight hour), minor failure (<1 in 10-3/flight hour), no effect (n/a)
• Different systems are affected by these levels (flight control computers, autopilot, navigation systems, flight data recorders, etc.)

Flight Software Design Assurance Levels

• Most software is treated like an aircraft component for certification and control
• Five levels of certification: level A (catastrophic failure), level B (hazardous failure), level C (major failure), level D (minor failure), level E (no effect)
• Examples of systems controlled by software: flight control computer, fly-by-wire, full authority digital engine control, flight displays, air data systems

Software Types

• Two main types: Field-Loadable Software (FLS) and Preloaded or Resident Software
• FLS can be updated without removing the system or equipment
• FLS and parts are identified by unique part numbers and can be verified electronically
• FLS is not dependent on current software state and doesn't prevent overwrite of prior versions
• Preloaded software needs the system or component removed to be updated

Preloaded or Resident Software

• Cannot be changed without physically removing the system or component
• Updates require sending the unit to a workshop for reprogramming
• Reasons include: the component not needing software changes, and inaccessible/highly contaminated components.
• Software may not be released to prevent changes

Loadable Software Aircraft Part (LSAP)

• Software considered part of certified aircraft design
• Associated documentation is required (EASA Form 1, FAA 8130-3)

Non-Loadable Software Aircraft Part or Aeronautical Database

• Field-loadable software not part of the certified configuration or Aeronautical Database (ADB)
• Used for navigation, flight planning, and terrain awareness
• Rigorous configuration control is required

Databases

• Two types: Model/Engine Database (MEDB) and Aeronautical Database (ADB)
• MEDB is LSAP-related, and a customised performance database
• ADB is often replaced regularly (e.g., every 28 days), containing current and previous database information

Operator Modifiable Software (OMS)

• OMS consists of User-Modifiable Software (UMS) and User-Certifiable Software (UCS)
• Permits modifications for preferred procedures, operational infrastructure, or local conditions.
• UMS modification by aircraft operators without certification authority review. UMS may include modifications to data and executable code affecting target hardware like: ACARS, ACMS, SATCOM, IFE systems

User-Certifiable Software (UCS)

• Operators choose modifications that are acceptable to the operator's regulatory authority.

Supplier Controlled Software (SCS)

• Operational Program Software (OPS) contains program instructions for a Line-Replaceable Unit (LRU)
• Each version of OPS has a unique software part number

Operational Program Configuration (OPC)

• Software that determines the function of the LRU
• It enables or disables optional functions of the OPS
• Eliminates the requirement for pin programming of the LRU

Aircraft Configuration List (ACL)

• List of modules, including LRUs, using LSAPs for a specific aircraft

Software Media

• Means of transporting and distributing software into equipment. Various forms including discs, memory cards, tapes, and the internet
• Physical media should be stored in a dust and lint-free environment protected from moisture, magnetic fields, and direct sunlight

Software Version

• Specific software item with a designated revision status.
• Versions typically use a major version and a minor version designation (e.g., A.BB)

Target Hardware

• Identifies the hardware for new FLS loading
• Target hardware includes: Enhanced Ground Proximity Warning System (EGPWS), Flight Control Computer (FCC), Flight Management Computer (FMC).

Sourcing Software

• Updates such as NDB, TDB, and MEDB should be obtained authentically, documented correctly on media, and meet required standards

Software Data Loading (Data Loaders)

• Means to load software and data updates is necessary for all computer systems
• Data loaders allow software/data updates to be added to programmable computer systems

Portable Maintenance Access Terminal (PMAT)

• Used to download loadable software into aircraft systems

Electronic Distribution of Software (EDS)

• Process to move software from the producer/supplier to remote sites (operators) without physical media

Field-Loadable Software Procurement and Documentation

• LSAP, databases, and UMS are first delivered with new aircraft and are located within target hardware
• LSAPs must be obtained from an approved source with associated documentation (FAA 8130-3, JAA Form 1)

FLS Storage Media Handling

• Avoid moisture, dust, airborne contaminants, magnetic fields, direct sunlight, rapid temperature changes, X-rays, and electromagnetic sources when handling FLS storage media.

Replication of FLS

• Recorded copies of FLS should be made using the aircraft's Type Design Organisation approved processes
• Traceable to original source for audit purposes
• Documentation of accepted release data should accompany LSAP storage media copies

Procedures

• Operators need procedures for determining the specific software and equipment configurations
• Documented procedure guidelines for compliance that cover procurement, distribution, receipt, inspection, assessment, embodiment, testing and release to service.

Case Study: Changing Aircraft Software

• Aircraft software changes affect operating characteristics.
• Affected areas include: Engine systems, Navigational systems, Flight control systems.

Air New Zealand Flight 901 - Mt Erebus Disaster

• Example case showing catastrophic effects of using unapproved software