Sunday, February 24, 2013

Integrated Modular Avionics for A380


The Flight International reported in 2001 that Airbus has selected Thales Avionics to supply the modules for the A380's integrated modular avionics (IMA). The company is, not surprisingly a French avionics manufacturer and it was working with a Germany company Diehl Avionik Systeme. The other candidate was Smiths Aerospace which supplies the common core system (CCS) for the Boeing 787 Dreamliner.

Works started to assist Airbus to define the concept of modular architecture and develop the system.

The Growth of Data Management in Aircraft.
The term DATA is normally used to describe the elements used in the computing. For the purpose of understanding, I am using it to include the command signals and the advisory signals used in the aircraft. That include the physical commands, like the command to turn left or right nose up or down.
A. Mechanical Linkages
In the days of B707, the term data processing was not coined yet. The command signal from the pilot was transmitted to the control surface via mechanical cable linkages. Some of the position indicators can be operated by mechanical cables. The example is the stab trim. The command can be from the pilot turning the stab trim wheel. The position of the stab trim is given the indicator in the central pedestal. The stab position indicator is driven mechanically by the mechanical cable. 

 B. Electrical - example stab trip switch.

C. Digital
a. ARINC 429 - Uses 32bits data words to transmit data. It is a simplex system, that mean, data can only move in one direction. A sender can have a maximum of 20 receivers. 

D. Federated Architecture
The ARINC 629 gave rise to the Federated architecture. is a multi-transmitter data bus protocol where up to 128 units can share the same bus. It was first installed on the Boeing 777. It is half duplex system, that mean a NOD can transmit and receive data, however it has to do it one at a time, when it transmits, it cannot receive and vise versa.

E. Integrated Modular Architecture.
a. Data processing
b. Data transmission. - ARINC 664 defines the use of a deterministic Ethernet network as an avionic databus in modern aircraft like the Airbus A380, Sukhoi Super Jet 100 and the Boeing 787 Dreamliner. The system is based on the commercial internet ( IEEE 802.3). The system is modified to add the deterministic elements as required in aviation. This is required to replace the "best effort" and missing word's packages in the commercial ethernet.

Sunday, February 17, 2013

Module 12.8 Helicopter Electrical Power ATA 24 Planning

Module 12 is on Helicopter Aerodynamics, Structure and Systems and module 12.8 is on typical helicopter electrical system.

In preparation for the lessons to groups of students, the following will be the topics of the powerpoint presentation. I am not able to include the powerpoint without removing some of the photos which may attract copy right issues.

1. Syllabus
The syllabus is in according to EASA part 66. The Malaysian version is under AN1101. 
12.8 Electrical Power (ATA 24) Level
Topics to be covered are...
- Batteries Installation and Operation; 
- DC power generation, AC power generation; 
- Emergency power generation; 
- Voltage regulation, Circuit protection. 
- Power distribution; 
- Inverters, transformers, rectifiers; 
- External/Ground power.

b. The fixed wing aircraft is similar and under the Module 11.6
- Batteries Installation and Operation; 
- DC power generation; 
- Voltage regulation; 
- Power distribution; 
- Circuit protection; 
- Inverters, transformers.

2. About Module 12.8 or 11.6
The electrical power system will always consists of 3 elements:
- Generation
- Distribution
- Utilization

3. Overview
To suit the adult learning preferences, I always give the students the overview. 
The traditional chalk and talk is used to suit the various levels of the students. Free white board drawing on the following topics.
- Brief Overview of parallel system
- Overview of DC System
- Main Components
- Generators – AC and
- CSD
- IDG
- RAT
- Voltage Regulator
- TRU
- Inverter
- Battery
- DC generator
- Circuit breaker

4. . Battery Installation and Operation
In module 3, we had covered the construction of batteries.
In this module, we cover on how the battery is installed in aircraft.
We are expected to know:
- Safety practices
- The practical installation and maintenance.
- The operation as intended for the aircraft.
- The circuit diagram
- Types of Batteries
       - Lead Acid
       - Nickel Cadmium
       - Lithium Ion

5. Battery Connector
A quick release connector with copper lockwire 26 AWG.
Contacts to be lubricated with  white petroleum jelly to prevent corrosion.

6. Temperature Monitoring - The importance of temperature monitoring. The description of thermal runaway.

7. Ventilation
- the various methods to ventilate, the importance of ventilation especially for lead acid battery.

8. Lead Acid Charging 
- Indications of fully charged cells
           - On charge – 2.7 volts => x12 = 32 volt.
           - SG maximum
           - Gassing

- Indication of fully discharged
          - Voltage 1.8v
          - SG minimum

9. Servicing – Lead Acid Battery
Lead Acid Battery
Nickel Cadmium
No servicing allowed.
Considered serviceable if the voltage (charger off) is above 24 volts.  


10 - Advantages/Disadvantage NiCd
 - The Advantages are Better power to weight ratio, Lower internal resistance, Longer life, Easy to replace cell, More robust and Higher Charging rate thus shorter charging time. Wider operating temperature

- Disadvantages are Higher cost, Prone to thermal runway and it Requires complex charging control circuit.  

11. Battery Capacity
Understand how capacity is measures and the effect of discharging rate on the capacity calculation.How the capacity is measured.

Saturday, February 16, 2013

TCP IP for Part 66

The new digital avionics used on the latest aircraft require the understanding of computer networking. For that purpose, I am including this video for my learning of TCP IP.

I find the graphic and animations used to explain TCP IP very informative..

 

 The video gives a graphical presentation of how the data is being sent from a computer to another destination. If your are sending a set of data to a receiver, you computer will break your data into smaller packages. Each package will have a number of information attached plus the contents. Some of the compulsory information are...the sender address, the receiver address, proxy server address. If you are sending from your office, it is likely that your data will enter the local area network. and then it will be sorted by the proxy server.    

Saturday, February 9, 2013

Internet Understand OSI - Open System Interconnect

Understanding the basic computer networking is a must for a person to understand the AFDX in an aircraft. For that reason, I had embarked in a journey to learn about networking.

We know that the data sent through internet packages, each has the addresses of sender and receiver.

To enable the different computers understand the messages, in 1970's -  ISO formulate the standard OSI model - the open system interconnection.. The network is in 7 layers:
application, presentation, session, transport, network, data link, physical.


In order to remember, take the first letters of the words, and you will have... all  ... people seem to need data processing.

The Function of The Layers
application layer -deal direct with the user. When you have something to send, the application layer will say... "hai, I have something to send".

-  presentation layer will format the things that you want to send.

- session layer - syncronisation so the sending and receiving syn

- transport layer - manage the package, data when sent are broken into packages

- network - routing and addressing, like ip addressing.

- data link - data frame management, the actual packaging, putting into the proper envilope.

- physical layer is the actual hardware.

When you are receiving the information, the path is reversed. It start with the physical layer.

How Data is sent and received
As it move down, information is being added to the data. On the receiving side, the wrapper is unrapped layer by layer, until the pure data is read.

TCP IP Model
It is based on DARPA model with 4 layer of data.
They are...

Appication
Transport
Internet
Network Access

The 4 layers relate to the 7 layer OSI model. 

Internet - Networking History of Ethernet

In my efforts to learn about the Integrated modular avionics face challenges, as most of the references in the internet assume that the reader understand the basic computer networking. We may come across comments stating that "the new AFDX is using is ethernet based" system. Thus, understanding the basic of computer networking is necessary to understand intergrated modular avionics.

I begin my search at the history of internet...
The history of ethernet began with Mr Xerox corporation in 1973, devising a system to connect its laser printer to multiple computers.









It is package data communication.
74 - PC was connected to the co-ax cable to communicate with other computers.Out of their own creativity the co-ax cable was called 'ether'. This was how the name ethernet was coined.

79  - Effort to manufacture ethernet compatible products.

80 - Promote ethernet as the standard communication network for PC. Compete with IBM, who promoted token ring.

89 - Ethernet won the battle when they switched the cabling standard to UTP.

The speed had brown tremendously, this was how it started:

- Started as 2.98 megabytes
- 10Base T - 10 megabyte per sec using the UTP
- 100 Base T - 100 megabytes
- 1 Gig
- 10 Gig



Reference : http://youtu.be/g5MezxMcRmk

Thursday, February 7, 2013

Basic Internet

Knowledge of internet is necessary as aircraft are using the concept and the technology in the data communication.

I have chose a simple and short Youtube video to give the basic understanding of the working of the internet. I am also putting information on ethernet, the basis of the AFDX, used on A380.

I like the simplified concept where the internet is considered to be a wire to which your computer is connected. There are many computers and networks that are connected to these wire where you can access them. Each of the items connected to the internet wire are given an IP address such as 216.76.29.153. These addresses are made more human friendly by giving them a suitable names known as domain names. A personal users like me will connect by computer to the internet through an ISP, Internet Service Provider. By searching through the address, I will reach the domain that I want to gain access. This concept is used in the aircraft communication although the protocol and the control may be different.

MIL 1553


1. Introduction
The MIL 1553 standard was published in 1973 to provide the functional characteristics of a serial bus. It was first used by F-16 Falcon followed by a number of other military aircraft. It is a half duplex system with redundant cables. 

To understand how the system work, we need to understand some of the terms:
- Avionic bus – communication between diff parts of ac
- Source – remote terminal with data to transmit
- Sink – a remote terminal to receive the date
- Dual redundancy  - use of back up system even part of comm. Fail, data will be sent and received.

2. Development on the EARLY aircraft.
-          Analogue
-          One device one display
-          No crss communication.
-          Example, altimeter, speedometer and compass are individual gauge.
Second generation
-          One devices many users.
o   Altimeter – display/ autopilot/ flight recorder.
o   Engine parameters – display/ autopilot/ flight data recorder/maintenance log.
-           
1980 ARINC 429, direct wire connection. As long the number is small, the system work well.

3. About MIL 1553
- Communication between 32 boxes.
- Data 32 16 bits words
- Command control , commander speak one at a time, all tramits begins with command word.
- Messages:
-                           0  BC to all RT
-                           0   Broadcast BC to all RT
-                            0 RT to BC
-                            0    Housekeeping messages (mode codes).

- Message format:
-                            0 Command word from bus controller
-                            0 Data from RT to/from bus controller
-           
-                             0 Status word from RT





          0 The 5 bits address can only support 32 remote terminals.

The T/R bits will determine receiving or transmission mode, 1=transmit and 0 = receive data

Subaddress allow access to RT subaddress.




Source:
https://www.youtube.com/watch?v=ovxxCFiKje4