ELEC4504/4906GAVIONICS SYSTEMS ENGINEERING

INTRODUCTION

• OBJECTIVES

• SOME HISTORY

• FACTORS AFFECTING AVIONICS DEVELOPMENT

COURSE OBJECTIVES

To provide the aeronautical engineering student with knowledge of:

1. The basic principles behind the avionics systems used in civil aircraft

2. The factors which should be taken into account when installing avionics in aircraft and

3. How the avionics systems are used in the operation of a commercial aircraft

COURSE OUTLINE

1. Organizational Framework

2. Air Traffic Control

CNS – Communications/ Navigation /Surveillance

3. The Electromagnetic Spectrum

4. Navigation

5. Precision Approach Systems

6. Communications Systems

7. Radar and Surveillance Systems

COURSE OUTLINE(CONTINUED)

8. Control Systems

9. Flight Management Systems

10. Display Systems

11. Electrical Systems

12. System Design

13. System Testing

14. Future Developments

Factors Affecting Avionics Development

1. Cost:

2. Number of systems in service

3. Benefits

4. Reliability

Sometimes it appears to take a long time to introduce new systems into service. There are several reasons for this

ORGANIZATIONAL FRAMEWORK

1. ICAO (International Civil Aviation Organization)

2. National Civil Aviation Organizations (FAA, CAA, Transport Canada).

3. RTCA

4. SAE

5. ARINC

6. EUROCAE

ORGANIZATIONAL FRAMEWORK

1. ICAO (International Civil Aviation Organization)

• Part of the United Nations

• Headquarters in Montreal

– Since civil aviation is an international activity, it is beneficial for all nations to use the same standards for most aspects of their aviation operations.

ICAO

– ICAO provides this service through documents called SARPS (standards and recommended practices)

– Examples of activities covered by SARPS are:

• Aircrew licensing

• Weather reports

• Flight plan forms

• Registration Markings

• Navigation Systems

ICAO

1. ICAO (Continued)

For example the SARPs on Navigation defines the characteristics of the Instrument Landing System (ILS) and includes:

• Signal strength

• Signal format

• Accuracy

• Coverage (distances at which usable signal can be detected)

ICAO

1. ICAO (Continued)

Note that all of these documents are recommendations only. Each country (or state) makes its own laws and rules

It is advantageous, however, for a country to follow these SARPS since non-standard practices discourage other countries from operating into such states.

ORGANIZATIONAL FRAMEWORK

2. RTCA (Requirements and Technical Concepts for Aviation)

Formerly known as the Radio Technical Committee for Aeronautics

and Radio Technical Commission for Aeronautics

• An example of the FAA’s practice of contracting out much of its technical work

• To understand the role of RTCA it is necessary to understand the FAA’s TSO (Technical Standard Order)

RTCA

• A given TSO is a minimum performance standard for a given piece of aircraft equipment (not restricted to avionics equipment)

• A TSO authorization is the FAA’s recognition that a given design meets the TSO and also authorizes the manufacturer to produce it.

• While the TSO authorization is not an approval to install the equipment it gives the equipment a very great advantage in obtaining certification for its installation

One of the first questions you are asked, if you want to install some equipment in an aircraft is “is it TSO’d?

Thus a TSO is very important

RTCA

• Q: Where do TSO’s come from?

• A: RTCA

When the FAA determines the need for a new piece of equipment e.g. a GPS receiver, it contacts the RTCA.

RTCA then establishes a committee (called a special committee) and invites anyone with any interest in the subject to join the committee. (airlines, equipment manufacturers, FAA officials, aircraft associations and international representatives)

GPS committee is SC-159

The committee produces a document called a MOPS (minimum operational performance standard) This is given a number preceded by DO

e.g. the MOPS for the GPS receiver is DO-208

RTCA

The RTCA MOPS is then submitted to the FAA which uses it as the basis for the TSO

The GPS receiver TSO is TSO-C129a

Thus the RTCA is a very powerful organization in the development of aircraft equipment (not just avionics)

ORGANIZATIONAL FRAMEWORK

ARINC (Aeronautical Radio Inc)

Started in the 1930’s by a group of airlines to provide communications between their aircraft and their bases.

It still provides this service through the ATN (Aeronautical Telecommunications Network) and ACARS (Aircraft Communications and Addressing System)

For avionics, however it is important for standardizing aircraft electronics boxes, trays and connectors.

Later it developed standards for aircraft digital data busses.

ARINC

ARINC (Aeronautical Radio Inc)

Started in the 1930’s by a group of airlines to provide communications between their aircraft and their bases.

It still provides this service through the ATN (Aeronautical Telecommunications Network) and ACARS (Aircraft Communications and Addressing System)

For avionics, however it is important for standardizing aircraft electronics boxes, trays and connectors.

ARINC

ARINC (Aeronautical Radio Inc)

Started in the 1930’s by a group of airlines to provide communications between their aircraft and their bases.

It still provides this service through the ATN (Aeronautical Telecommunications Network) and ACARS (Aircraft Communications and Addressing System)

For avionics, however it is important for standardizing aircraft electronics boxes, trays and connectors.

ARINC

Electronic Equipment in aircraft has to be

• Firmly attached to the aircraft structure (by means of racks)

• Wired in to the aircraft systems

– Power

– Signals

– Controls

ARINC

Early Electronic Equipment was not standardized and hence the mounting systems and connectors were different not only for each piece of equipment but for the same equipment from different manufacturers

Thus upgrading equipment was expensive and time consuming

ARINC devised a set of standard “black box” sizes and corresponding mounting systems as well as connector designs.

ARINC

With standardized racks, boxes, trays and connectors, airlines could choose among various manufacturers of a particular item (e.g. Communications Transceiver) knowing that all they had to do was pull out the old set and plug in the new one.

ARINC

The original standard was called ARINC 404.

Or ATR (Air Transport Racking)

“Black box” sizes were 1ATR, 3/4ATR, ½ ATR, ¼ ATR etc.

A 1ATR box was about 10” wide, 8”high and 22” deep

The latest racking standard is ARINC 600 series.

ARINC

With the advent of digital communications in aircraft, ARINC developed popular digital data bus communications standards, primarily ARINC 429 and ARINC 629

SAE

SAE (originally Society of Automotive Engineers, now SAE International)

Another organization which develops standards.

For avionics the primary publications are ARP’s (Aerospace Recommended Practices)

ARP5672 - Aircraft Precipitation Static Certification

AS 5672A - ARC Fault Circuit Breaker (AFCB), Aircraft, Trip-Free Single Phase and Three Phase 115 VAC, 400 Hz - Constant Frequency

EUROCAE

EUROCAE is essentially the European version of RTCA

The two organizations work closely together and publish joint standards.

AIR TRAFFIC CONTROL (ATC)AND ITS RELATIONSHIP TO

AVIONICS SYSTEMS

OBJECTIVES OF ATC

• Maintain separation of aircraft• Expedite the flow of Air Traffic• NOT responsible for the separation of aircraft

from the ground (except when in radar contact

RESPONSIBILITES OF THE PILOT (GENERAL)

Maintain aircraft ATTITUDENavigate the aircraft from departure to destinationAvoid collision with other aircraft

How these are accomplished depends on the weather(specifically ceiling and visibility)

VISUAL METEOROLOGICAL CONDITIONS (VMC)

Generally 3 miles visibility and 1000 Ft. ceiling

Visual Flight Rules (VFR) apply

– Attitude maintained by visual reference to the horizon

– Navigation by reference to the ground (or electronic aids if pilot is able to and aircraft is so equipped

– Separation from other aircraft by visual contact (see and be seen) Note: ATC will assist but is not responsible.

– Aircraft not allowed to enter cloud

VFR ON TOP

With extra training in radionavigation, pilots can fly in clear air above cloud

– Note: Attitude is still with reference to the visible horizon

– Climb and descent must not require entry into cloud

INSTRUMENT METEOROLOGICAL CONDITIONS (IMC)

IMC exist whenever VMC do not

Obviously the rules pertaining to IMC are IFR (Instrument Flight Rules)

IFR apply in IMC and also to all flight above 18000 Ft in Canada and the USA (other altitudes are specified in other countries)

INSTRUMENT FLIGHT RULES

Separation from other aircraft is responsibility of ATC

ATC issues “clearances” which are specific routes/altitudes which must be followed.

Attitude (pitch, bank and heading) is maintained with reference to instruments.

– Simplest: artificial horizon and compass– More complex: inertial navigation system

Navigation is done using electronic navigation aids

Two way communication is required between pilot and controller

ATC must know where aircraft is

– ATC radar requires a transponder on the aircraft

INSTRUMENT FLIGHT RULES

On-board Collision Avoidance Systems supplement ATC

Terrain Avoidance Systems provide protection from CFIT (Controlled Flight Into Terrain) when aircraft is out of radar coverage

Typical IFR Flight Procedure

Pilot plans route (including altitudes) from departure point to destination

Pilot files flight plan

ATC decides if flight plan can be accepted as is or if it needs to be amended

Prior to starting engines, pilot requests ATC clearance.

ATC gives clearance (may be just “flight planned route”)

Pilot contacts ground control for taxi clearance

Typical IFR Flight Procedure

Aircraft taxis to runwayTakeoff clearance is obtained from TowerAfter takeoff, pilot contacts Departure Control who gives “vectors” or a

series of headings and altitudes to guide aircraft to the start of the route to which it has been cleared

Near destination, Arrival Control provides vectors to the landing approach.

Tower gives clearance to landGround Control gives clearance to taxi to arrival gate