Aircraft Systems Integration of Air-Launched Weapons

Keith A. Rigby, Peter Belobaba, Jonathan Cooper, Roy Langton, Allan Seabridge

• Editorial: Wiley
• Año: 2013
• ISBN:
  9781118519172
• Edición: 1
• Categoría: Technology & Engineering
• Categoría: Aeronautic & Astronautic Engineering

From the earliest days of aviation where the pilot would drop simple bombs by hand, to the highly agile, stealthy aircraft of today that can deliver smart ordnance with extreme accuracy, engineers have striven to develop the capability to deliver weapons against targets reliably, safely and with precision.

Aircraft Systems Integration of Air-Launched Weapons introduces the various aspects of weapons integration, primarily from the aircraft systems integration viewpoint, but also considers key parts of the weapon and the desired interactions with the aircraft required for successful target engagement.

Key features:

• Addresses the broad range of subjects that relate directly to the systems integration of air-launched weapons with aircraft, such as the integration process, system and subsystemarchitectures, the essential contribution that open, international standards have onimproving interoperability and reducing integration costs and timescales
• Describes the recent history of how industry and bodies such as NATO have driven the needfor greater interoperability between weapons and aircraft and worked to reduce the cost andtimescales associated with the systems integration of complex air-launched weapons withaircraft
• Explores future initiatives and technologies relating to the reduction of systems integrationcosts and timescales

The systems integration of air-launched weapons with aircraft requires a multi-disciplinary set of engineering capabilities. As a typical weapons integration life-cycle spans several years, new engineers have to learn the skills required by on-the-job training and working with experienced weapons integrators. Aircraft Systems Integration of Air-Launched Weapons augments hands-on experience, thereby enabling the development of subject matter expertise more quickly and in a broader context than would be achieved by working through the life-cycle on one specific project. This book also serves as a useful revision source for experienced engineers in the field.

1

Introduction to Weapons Integration

1.1 Introduction

One of the key differences between civilian and military aircraft is that many military aircraft have the ability to carry and release weapons. From the earliest days of aviation where the pilot would drop simple bombs by hand, engineers have striven to develop the capability to accurately deliver weapons against targets reliably and safely. Today, for a successful target engagement, it is essential for the aircraft and weapon to be integrated such that the full ­capabilities of the weapon can be exploited. The release of a weapon whether it is a forward-fired missile or a downward ejected store such as a fuel tank, from either an externally mounted pylon or from an internal bay, creates issues such as the ability to achieve safe separation and the ability of the aircraft structure to withstand the imparted loads. The complexity of weapons integration is increased when the requirements for priming and aiming are considered. The integration of weapons onto aircraft therefore requires a multi-disciplinary set of capabilities within the integration organisation.

The generic term for any mission payload carried on an external pylon or an internal bay on a non-permanent basis is a ‘store’. The family of stores includes weapons, fuel tanks, ­countermeasure pods and so on. Whilst many of the stores would only be released from the aircraft under emergency conditions (e.g. in the event of an engine failure during take-off), weapons are designed to be released as a matter of course.

This book gives an introduction to the subject of weapons integration, primarily from the viewpoint of aircraft electrical and computing systems integration, and explores the systems integration problem space, outlining the importance of systems integration and the ­contribution of industry standards in achieving an integrated aircraft and weapons capability.

The following sections outline the contents of the main chapters of this book and then ­introduce the various aspects of weapons, the subsystems they employ and the contributions these make to a successful target engagement. By gaining an understanding of weapons, the subject of their integration with the launch platform can be explored.

1.2 Chapter Summaries

1.2.1 The Systems Integration Process

As with any system design, a structured, top-down approach is essential. However, for ­weapons integration, the higher level requirements will also include aeromechanical aspects such as the desired release envelope, carriage life, the number of weapons that can be carried, influences of other weapon and store types to be carried on the same sortie, and so on. In a series of chapters, the book will outline the basic systems engineering process employed in a typical weapons integration programme. This will include the definition of an appropriate set of requirements and their partitioning to subsystems, through systems implementation, to qualification and certification. The types of requirements that should be considered will be discussed and the benefits of minimising the number of initial requirements and the need to avoid ‘over engineering’ of requirements will be explained.

The need to consider safety from the outset and its place in the overall systems integration process will also be covered as will the individual responsibilities of the aircraft and weapon design organisations (WDOs).

Once the top-level integration requirements have been defined, there is a need to ­decompose these into more detailed requirements and to then partition these to the aircraft subsystems. This segmentation process may use software-based requirements management tools as these will, in due course, assist in the validation and verification of the system implementation against the requirements. This partitioning exercise depends on the actual aircraft system ­architecture and will therefore differ between aircraft, with the requirements being partitioned to individual aircraft subsystems, which could be implemented in both hardware and software. Each requirement placed on the aircraft’s subsystems will need to be proven for correct ­implementation, and the subsystems will then be progressively built up into an overall ­integrated system that provides the required military capability. This will include the testing of the system and its components in a Systems Integration Laboratory (SIL). Employing either weapon simulators or inert weapons with operational electronics, integration testing will test that all the aircraft subsystems are working together to control the weapon. Any problems which are identified would then need to be corrected during an iteration of the system design and implementation.

The typical individual responsibilities of the aircraft and WDOs will also be discussed.

1.2.2 Stores Management System Design

The first electrical systems to control the release of stores were based on relays that when energised would switch the current to the bomb rack, causing it to open. The relays were operated by the Bomb Aimer pressing the release button, thereby routing a current to the relay coils. From a safety and certification viewpoint, it is essential that an aircraft only releases a store when intended. This appears to be an obvious requirement, but it is the primary driver in the design of the armament system of an aircraft.

This requirement forced the design of systems with multiple breaks in the bomb rack firing chain such that a single failure, on its own, could not cause weapons to be released ­inadvertently. This basic principle is often referred to as the ‘no single failure’ criteria as no single failure can cause an unintended release of a store when not intended. A second ‘availability’ principle is often also quoted such that no single failure shall prevent a release when intended.

In a modern military aircraft, the simplicity of the first electrical systems has been replaced by a subsystem in its own right which is generally referred to as the Stores Management System (SMS). The SMS manages the weapon load-out and controls the safe arming, release, jettison and operation of any store loaded on the aircraft, including the generation of the ­high-integrity data messages required by modern smart weapons to ensure their safe ­operation. This increased level of functionality and the need to ensure that weapons are only released or jettisoned when required are the primary drivers in SMS design, adding complexity to the hardware implementation and introducing the need for embedded safety critical software. Chapter 4 will explore the SMS design considerations and outline common system ­architectures that are found in modern military aircraft. Design considerations for aircrew training for ­Air-to-Ground weapons delivery will also be discussed.

1.2.3 The Global Positioning System

The accuracy to which weapons can be delivered on target is a key requirement of most new weapon programmes. Since the first Gulf War in 1991, there has been an increased use of navigation technology such as the United States’ Global Positioning System (GPS) to assist in the terminal guidance of weapons. This increased use of GPS receivers in guided weapons has enabled the continued potency of legacy aircraft. The integration of such so-called smart weapons brings with it special problems for the aircraft systems integrator. Chapter 4 will also outline the basic operation of GPS and discuss a number of aircraft system design issues that need to be considered when integrating such weapons.

1.2.4 Weapon Initialisation and Targeting

Different weapons demand different methods of targeting. Targeting a weapon, be it an Air-to-Ground weapon or an Air-to-Air missile, can be very complex and place great demands on the performance of the aircraft systems. For the accurate targeting of a smart weapon, it is ­essential that the aircraft and weapon axis reference systems are initialised to provide a common ­reference, thereby removing position and velocity errors. The chapter on weapon initialisation and targeting will discuss weapon initialisation and examine the different ways in which weapons are targeted covering the accurate delivery of ballistic bombs, the flexibility of ­targeting for smart weapons and the sensor types and target prosecution strategies of Air-to-Air missiles. Training for the delivery of Air-to-Air missiles will also be discussed.

1.2.5 The Role of Standardisation in Weapons Integration

From the earliest days of guided weapons, weapon designers have defined their interfaces to optimise the requirements against technologies that have been available. This has led to a plethora of different interfacing systems existing on aircraft.

In a modern aircraft/store integration programme, technical standards play a significant part in improving interoperability and reducing integration costs and timescales. For example, standards such as Military Standard 1760 (MIL-STD-1760) have sought with some success to reduce the number and variation of interfaces and thereby improve interoperability of ­different weapons across many platforms. With the success of interfacing standards, the weapons ­integration community has also developed standards that ease other areas of integration such as protocol standards that facilitate greater interoperability in aircraft computing systems. The chapters covering standardisation will review a number of important weapon interfacing standards including MIL-STD-1760 (Aircraft-Store Electrical Interconnection System), the Miniature Mission Store Interface Aerospace Standard (AS5725) and the standard for the Interface for Micro Munitions (AS5726).

Other important industry technical standards such as the Generic Aircraft-Store Interface Framework, the Mission Data Exchange Format and the Common Launch Acceptability Region Approach will also be covered.

1.2.6 Interface Management

Weapons integration programmes require the aircraft design organisation and the WDO to collaborate. The interface between the aircraft and the weapon must therefore be agreed by the two parties and documented in an Interface Control Document (ICD). The ICD defines all information relevant to the integration such as mechanical attachments, electrical signal sets, data structures, timeline (a detailed temporal sequence of data and state transitions required for the aircraft to operate the weapon), environmental data, aerodynamic data and so on. Negotiation of the ICD can be a significant activity, particularly when a new weapon is being developed in parallel with its integration with the platform.

The chapter on interface management (Chapter 8) will give an overview of the type of ­information that has to be agreed in an ICD but will also detail the differing approaches between the United States and Europe in controlling the interface data and managing the process to agree the ICD. Where a weapon is to be integrated across a number of platforms, there may be a need for several programmes to develop and agree ICDs simultaneously. This provides a significant organisational challenge. Strategies such as the need for an Interface Control Plan and multi-programme Interface Control Working Groups will also be ­considered. Chapter 8 will also discuss an effective management process for controlling and reducing integration risk.

1.2.7 A Weapons Integration Scenario

Having covered the various aspects of aircraft systems integration of air-launched weapons, two chapters will draw together all the proceeding chapters and consider how they would contribute to a ‘real’ weapons integration programme (albeit, based on a hypothetical weapon). The first chapter (Chapter 9) identifies example specifications and features for some aspects of the weapon and the aircraft which will be used to illustrate elements of the system’s ­integration, by considering the activities relating to the design implementation. In order to aid the understanding of the scenario, a typical weapon loading (to the aircraft) to dispersion (safe separation from the aircraft) sequence will also be discussed.

Chapter 10 will continue to draw together the proceeding chapters of the book and expand on other areas of the integra...