International Civil Aviation Organization
WORKING PAPER / ACP-WGW2/WP-11
21 April 2008
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
SECOND MEETING OF WORKING GROUP W
Montreal, 21-25 April 2008
The Technical Characteristics and Performance objectives for installed Wireless Avionics Intra-Communications (WAIC) systems.
(Prepared by Aerospace Vehicle Systems Institute)
SUMMARYThis paper presents aspects of on-board wireless communications systems for avionics applications, a subject recently introduced to the telecommunications spectrum regulatory community. The paper results from the outcome of discussions from the ITU-R Working Party 5B (WP 5B)meeting held in February 2008. Two documents addressingthe technical characteristics, performance objectives, and potential spectrum requirements for installed Wireless Avionics Intra-Communications (WAIC) systems were considered.
It is anticipated that due to the increasing demand, more wireless technologies will be used for future aircraft systems, including those that impact the safety and regularity of flight. Therefore, determining whether and the amount of additional dedicated spectrum, for systems impacting the safety and regularity of an aircraft’s flight, is required and extremely important to the aviation industry. Other international standards for WAIC systems may also be required.
ACTION
WG-W is invited to consider this paper in the context of dedicated aviation spectrum requirements for WAIC systems, and for requirements for international standards for WAIC systems. Members are encouraged to participate in the work of ICAO ACP WG-F and through ITU-R WP5B to obtain a new ITU-R study question and eventual ITU-R Recommendation on this matter, and are also invited to support ICAO in developing potentialstandards and recommended practices (SARPs) necessary for WAIC systems.
1. Background
At the last WG-F meeting in Nairobi during September 2007, a presentation was made introducing a new subject to the group with regards to replacing cables and wiring within the aircraft with wireless links which would considerably reduce the aircraft weight and ease aircraft configuration. During the presentation it was stated that currently it is only possible to replace non-safety cable systems with wireless technology, because such applications utilize frequency bands designated for Industrial, Scientific and Medical (ISM) applications and are therefore not suitable for operations impacting the safety and regularity of flight. The group noted that dedicated spectrum may need to be secured before these safety applications can be migrated to wireless. It was agreed that updates on this subject will be presented at future sessions of WG-F.
2. Introduction
At the ITU-R WP 5B meeting in February 2008, the US and Canada submitted separate documents proposing a Preliminary Draft New Questions (PDNQ) requesting the ITU-R to study the technical characteristics and operational requirements of aircraft wireless systems that impact the safety and regularity of flight, as well as a working document to begin those studies. These systems were later named Wireless Avionics Intra-Communications (WAIC) systems.[1] The meeting considered the PDNQ titled “Technical Characteristics and Operational Requirements for Wireless Avionics Intra-Communications (WAIC)” addressing the technical characteristics and operational requirements of aircraft wireless functions that impact the safety and regularity of flight (Annex 8 to Document 5B/45), in order to determine the appropriate protection criteria when sharing with other applications or radio services. The PDNQ also asks the ITUR to study the potential spectrum requirements for WAIC applications. Further,the PDNQ asks the ITU-R to seek input from ICAO and administrations regarding the wireless WAIC application(s) envisioned to be installed on board aircraft. AVIS’sgoal is to obtain approval of the PDNQ at the next meeting of ITU-R WP 5B.
The working document titled “Working document on technical characteristics and performance objectives for installed Wireless Avionics Intra-Communications (WAIC)” was also considered at the meeting and carried forward to the next meeting for continuation of the WAIC studies. Additional contributions are anticipated from the U.S. and Canada, as well as other interested administrations to progress the work. This document provides preliminary information about WAIC potential applications and benefits. It alsobegins the process of studying the operational and technical characteristics of WAICs so as to help the aviation industry progress in deriving the benefits of wireless technology; andwill be used as a resource for answering the questions in the PDNQ.
Installed Wireless Avionics Intra-Communications (WAIC) systems are envisioned to provide communications between two or more points on a single aircraft that may include integrated wireless components (such as flight-deck headsets or crew microphones) and/or installed components of the system. In all cases those communications are assumed to be part of a closed exclusive network required for operation of the aircraft. WAIC systems may not be limited to the interior of the fuselage, depending on the type of aircraft. For example, sensors mounted on the wings or engines could communicate with systems within the airplane. WAIC systems do not provide air-to-ground or air-to-air communications. They also do not include communications with consumer devices, such as Radio Local Area Network (RLAN), devices that are brought on board the aircraft by passengers.
WAIC systems offer commercial aircraft designers and operatorsthe potential opportunity to improve flight safety and operational efficiency. Wireless systems are currently utilized on commercial aircraft for non-safety related applications. The aviation industry is constantly designing new and redesigning current aircraft that will be safe while reducing costs. The ability to use the same type of installed wireless avionics communications systems globally is extremely important to the commercial aviation industry, given the international nature of aircraft use; but accomplishing such is a significant challenge. Because WAIC applications would be installed on many types of aircraft that would cross national borders, the ITU-R should lead the effort to study the technical and operational characteristics, performance and protection criteria when sharing the same radio frequency spectrum with other applications or radio services, taking into account the efficient use of the radio frequency spectrum.
This paper is intended to provide the same information that has been provided to ITU-R WP 5B about potential WAIC applications and the benefits that can be derived from such applications, to bring the PDNQ to the attention of ICAO, and to begin discussion within ICAO regarding developing the appropriate communication requirements andtechnical characteristics of WAIC systems in order to begin the process of developing the ICAO Standards and Recommended Practices (SARPs). This paper also encourages ICAO to support the ITU-R effort.
3.Discussion
WAIC systems are envisioned to provide communications over short distances between points on a single aircraft. WAIC systems are not intended to provide communications, in any direction, between points on an aircraft and another aircraft, systems on the ground or satellite. WAIC systems are intended to support voice and data communications between: the aircraft and those operating it; flight crew; operational crew, and aircraft systems. It is also envisioned that wireless sensors located at various points on the aircraft will be used to monitor the health of the aircraft structure and its critical systems, and communicate information within the aircraft to those who can make the best use of such information.
Points of communication may include integrated wireless components (such as flight-deck headsets or flight and cabin crew microphones) and/or installed components of the system. In all cases communication between two or more points on a single aircraft is assumed to be part of a closed, exclusive network required for operation or evaluation of the aircraft. WAIC systems are not intended to provide air-to-ground or inter-aircraft communications. They are also not intended to include communications with consumer devices, such as Radio Local Area Network (RLAN) devices that are brought onboard the aircraft by passengers.
WAIC systems are envisioned to offer aircraft designers and operators many opportunities to improve flight safety and operational efficiency while reducing costs to the aviation industry and the flying public. Development and implementation of such WAIC systems, including those that may improve flight-safety or safety-related services are now being pursuedby the commercial aerospace industry., subject to the completion of the necessary technical and compatibility work to answer the questions in the PDNQ within ITU-R WP 5B and the development of appropriate ITU-R Recommendations and/or Reports, as well as ICAO standards, including ICAO SARPs, that will facilitate theaircraft certification of these new WAIC systems.
Because WAIC systems are located on an aircraft, they are inherently transient, crossing national boundaries.
3.1Benefits of wireless
WAIC systems are envisioned to provide significant benefits to all who use the sky to travel. Some of the areas that WAIC may benefit are described below:
3.2Cost reductions through the substitution of wiring
Cabling and wiring present a significant cost to the aircraft manufacturer, airline operator, and ultimately the flying public. Costs include the design of sensor sizing and wiring routing, wiring harness designs, labor-intensive cable fabrication, reliability and replacement costs of connectors, as well as the associated operating costs of the wiring and connectors that represent approximately 2-5% of an aircraft’s weight.
Wireless products offer solutions that can reduce the time and costs associated with wiring design and build time. Wiring harness design is one of the critical factors in determining the time required to design a new aircraft. Engineers must specify and determine the routes for miles of cabling, including providing separate routing paths for redundant wiring, so that a single point failure does not affect redundant circuits. Engineers must also design wiring in order to minimize thepotential electromagnetic interference from both internal electrical systems as well as external sources such as lightning.
As an airframe is utilized during its lifetime, it may be necessary to install new sensors to monitor portions of the aircraft structure or aircraft systems. On current aircraft, adding new sensor systems is very expensive due to the requirements to install wiring, connection to the central processing system, and software modifications. WAIC networks could allow new sensors to be mounted with much less difficulty and expense, and enable easier modification of systems and structural monitoring throughout the life of the aircraft which is typically about 25 years.
3.3Enhanced reliability
Wiring is a significant source of field failures and maintenance costs. It is extremely difficult to troubleshoot and repair such failures in aircraft system wiring which occur at interface points, where connectors, pins, and sockets come together. A wireless system may significantly reduce electrical interfaces and thus increase system reliability.
By having fewer wires on an aircraft, the need for wire maintenance to remediate chafing conditions, aging wiring and associated hazards is reduced, thereby improving aircraft safety and reliability. Wireless technologies are also intended to offer the means to implement reliability-enhancing systems. Adding new sensors on an aircraft to monitoraircraft functions, such as equipment cooling status,to better report and enable adjustment of those functions, also have the potential to improve the reliability of aircraft. The introduction of these additional sensors has been limited due to weight and cost impact. However, they might be implemented using wireless technology. Aircraft data networks could also take advantage of redundant communication paths offered via mesh networks, which are not cost-effective in hard-wired form.
3.4Additional functions
Wireless technologies are also envisioned to provide new functionalities to aircraft manufacturers and airline operators. Currently, there are few dedicated sensors for monitoring the health of aircraft systems as the aircraft ages. Wireless technologies could provide additional opportunities to monitor and control more systems without increasing the aircraft’s weight. In addition, wireless technology could provide more adaptive cabin configurations and potentially more customized “plug and play” subsystems.
4.Categorization of WAIC Systems
Future wireless aircraft systems can be categorized into those that will replace existing wired systems and those that can provide new functionalities because of the wireless technology.
It is necessary to identify the communication requirements and the necessary technical characteristics of the WAIC application, such as, the data rate, spectrum bandwidth, link distance, and radio path. The type of aircraft also plays a role in determining the technical characteristics because link distances, power, and data path can vary based upon the type of aircraft.
4.1Types of aircraft
The type of aircraft on which the WAIC system is installed may impact the requirements for the system. Typical types of aircraft include regional, business, wide-body, and two-deck aircraft, as well as helicopters. These different aircraft types may place different communication requirements and, in turn, different technical and performance criteriaon the WAIC systems; and may also impact the type of propagation path between the WAIC transmitter and receiver.
Also, some transmissions may not be limited to the interior of the fuselage, depending on the type of aircraft. For example, sensors mounted on the wings or engines could communicate with systems within the airplane.
4.2Communication requirements
To analyze the suitability of converting wired systems to wireless, candidate data links should be characterized by their communication characteristics, including data rates in bits per second (instantaneous and average), acceptable limits on data latency, data criticality, link distance, and characteristics of the probable radio path such as fading and multi-path effects.
The “criticality” of an application is a measure of the risk to the safe operation of an aircraft and its passengers. The intent of aircraft airworthiness certification is to assure safety. Design Assurance Level (DAL) is directly “proportional” to the criticality of a failure of a device. Therefore, when adevice can have different failure modes whose consequences on the safe flight of an aircraft are more severe (i.e. risk augmenting), the device must be designed according to aeronautical certification rules corresponding to a higher DAL. DAL requirements may prove useful in evaluating whether a particular function supported by the WAIC system is safety-related.
Furthermore, international, regional and national aviation authorities will be involved in determining the performance objectives for WAICsystems providing safety services.
Representative aircraft systems currently wired that may provide excellent opportunities to utilize wireless technology are listed below:
–Crew communication: contained within the cabin, active in all flight phases.
–Cabin lighting control: contained within the cabin, active in all flight phases.
–Cabin pressure: contained within the cabin, active in all flight phases.
–Transmitting Sensor data:
–Proximity sensors: located throughout the aircraft, active in all flight phases.
–Smoke sensors: inside fuselage, active in-flight.
–Engine sensors: located in the wing, active in all flight phases.
–Fuel tank/line sensors:located in the wing and fuselage, active in-flight.
–Air data sensors: located outside of aircraft, active in-flight.
–Temperature/humidity and corrosion detection sensors: located throughout the aircraft, active in all flight phases.
–Structural sensors: located throughout the aircraft, active in all phases of flight.
–Position sensors for doors, valves and other mechanical moving parts: located throughout the aircraft, active in all phases of flight.
–Mechanical component health monitoring and diagnostics: accelerometers monitoring vibration, located throughout the aircraft, active intermittently when commanded by the data acquisition engine.
–Landing gear wheel speed: outside of fuselage, active on ground, during take-off, landing.
–Landing gear steering feedback: outside of fuselage, active on ground, during take-off, landing.
–Ice detection: outside of fuselage, active in all flight phases.
–Flight-test Instrumentation: located throughout the aircraft, active during all phases of flight.
4.3Design Assurance Level (DAL) requirements
Aircraft systems designers must meet DAL requirements. At this time, DAL requirements for WAIC applications are To Be Determined (TBD).
5.Typical Wireless Technical Characteristics
Typical wireless system characteristics are TBD.
AVSI encourages ICAO to begin the effort in generating the necessary international SARPs regarding WAIC applications. The appropriate SARPs will depend upon the WAIC technical characteristics and communication requirements. At this time, AVSI requires assistance from ICAO WG F participants in generating the appropriate technical characteristics of the WAIC systems and to fully contribute to the work to answer the questions in the attached PDNQ, in order to develop the necessary ITU-R Recommendations, as well as incorporation of that information into the ICAO SARPs. AVSI requests ICAO's assistance in developing appropriate technical characteristics for WAIC applications.
6.Current ICAO Initiative
It is necessary that the aviation industry work with ICAO to develop the necessary SARPs for these safety-related WAIC systems. Recognition and acceptance within ICAO for this effort is required for developing SARPs,which could provide an insight on the potential spectrum requirements for WAIC andin supporting ITU-R effortsto answer the questions in the PDNQ as well as the development of the necessary ITU-R Recommendations.
7.Conclusion
The ability to use the same type intra-aircraft wireless WAIC system globally is extremely important to the commercial aviation industry, but presents a significant challenge given the international nature of air travel. The aviation industry is constantly redesigning current and designing new aircraft that will be safe while reducing costs. Active participation by the aerospace industry,ICAO, and representatives of aviation certificationbodiesis necessary in order to enable the aviation industry to deliver the benefits of this wireless technology.