BASIC NETWORKING

The IMA (integrated modular avionics) on A380 and B787 uses AFDX (avionics full duplex) system for the communications between the different components. The AFDX is based on the off the shelf commercial ethernet technology used for LAN (local area network). As such, it is important for the students to have a working appreciation of networking, and for that reason, I include a youtube video on basic networking.

AFDX - Aircraft Avionics Full Duplex System

The AFDX stands for avionics full duplex, a communication system used by both Airbus and Boeing for the latest aircraft. It was developed by Airbus mainly for A380 jetliner and later used in its A400 and A350. Boeing use it for B787. It is also known as arinc 664 part 7.  It is replacing the arinc 429 and 629. The 429  offers point to point communication in its simplex data communication which is not suitable as the number of systems and LRUs had grown significantly. The 629 offers half duplex communication with full expansion potential, however it requires special interfaces and equipment, thus, it is costly.

Ethernet is the most common communication system used in the commercial computers it the LAN system, but it suffers the two main disadvantages. It works on data packages and there are instances of missing data. Secondly, it is limited ability in its to control and schedule the communication timing, thus it is NOT suitable for system that requires immediate action/ responses such as the flight control system.

The communication system of the avionics requires:
- guaranteed real time operation.
- support repetitive data such as the altitude and latitude.
- support file data such as used for database and video.

 The AFDX is designed based on the ethernet technology with the added features to:
- ensure real time communication
- enable sampling messages
- enable queuing and SAP messages.
The system group the packages into three different types of data such as sampling and queuing. Each package on each VL will have sequence number to ensure all data are received and no duplicate data are used twice.

To make it real time, the sources and destinations are predetermined, this easier as the aircraft systems are closed systems where the users are predetermined.This is done by using the concept of virtual virtual links where a transmitter may talk to multiple receivers, like the concept of ARINC 429.

DIAGRAM to be added

There 3 VL here...
T1 ==> R1
T1 ==>R2
T1 ==> R3

Virtual links can only have 1 source, and they are simplex.

Each VR is allotted the BAG ( bandwidth allocation gap)  such as 1st, 2nd, 3rd .... 128 millisec. It there are more than one receivers, the AFDX will keep the signal as buffer.

The jitter is the time different between the transmission and receiving.
The BAG determine the timing and the frequency of the link, but not the contents. The contents is designed as per ARINC 653.

Redundancy - It is a concept designed for safety of the system. The data is transmitted in 2 different network.The first valid frame received will be used and the second data will be ignored.

Resources:
http://youtu.be/LxTVxz5ogag

---------------------------------------------------
Additional Information.

1. ARINC 664 consists of 8 parts. They are...
a. systems concept and overview
b. ethernet physical and data links layers.
c. internet based protocol and services.
d. address structure and numbers.
e. network domain and interconnect
f. network management
g. AFDX
h. Operation with non-IP protocols and services

DCA exam for aircraft maintenance license

Malaysian DCA exams to qualify as aircraft engineer are in a new format. From January 2013, the traditional paper based exams ended and replaced by the web based online examinations.

A candidate for the examination will have to follow the predetermined steps. The following are the process involving the candidate, Malaysian DCA and the computer system:.

1. CAAI and DCA build up the exam question data base.
2. The candidate Create your ID and profile.
3. DCA review and validate the ID and profile ( off line)
4. The system will notify the candidate that he/she is a registered candidate.
5. Candidate view the schedule and select the exam date.
6. Candidate Books the examination session.
7. The system generate the invoice.
8. The candidate pay the invoice online.
9. On the examination session, the candidate register for system generate questions set by random selection.
10. Candidate download the question paper and select the answer.
11. On completion, candidate update the paper.
12. System mark the paper and send the result to DCA.
13. DCA validate the result.
14. System notify the result to the candidate.

Module 4 - Question Samples

These can be some of the areas to be questioned. The questions are not designed as per the requirements as it is intended to demonstrate the possible ares to be asked.

1. Why diode is place in series to LED?.
        To protect the LED against reverse voltage.

2. In NPN transistor, what is P?.

3. What type of pulse trigger for SCR?

4. When SCR start to conduct , when does it stop?

5. Transistor is saturated, what happen to the resistance?

6. A capacitor is used to separate multistage amplifier, what is the effect of the capacitor.

7. To be used as amplifier, the transistor must be biased at which region?

8. Ops Am, + connected to earth, what type of amplifier?

9. How do you control the gain of an operational amplifier?

10. The process of adding impurities to semiconductor is called….

11. Where is/are the traces in a Multilayed PCB?
Traces are the copper connectors either at the top/bottom or is some PCB in the core.

12. What is/are the PCB substrate is made from?
substrate is the base of PCB, it is made from insulation material such as fibre glass or resined paper.

13. After the components are soldered, the PCB is environmentally sealed by using ……….  Coating.

The coating is called conformal coating, it provides the protection but easier to remove the components.

14. How is the DIP ic being mounted on PCB?.

15. When testing diode, you have low resistance in both ways, what does this show?.

16. What type of component the 3N123? .

Hall Effect Sensor

Hall effect is being used for various sensing functions. Before we discuss a typical sensor, let us review the Hall Effect.

I enclose a video on hall effect.
A few type of hall effect sensors are discussed.
- hall effect switch - when the south pole is brought near the switch, the LED  is switch on. When the south pole is taken away, the LED goes off. However, when a north pole is brought near, the switch is not activated.
- hall effect latch.- This is a type of sensor, where when is switched to on, it remain on until a north pole is brought into proximity.



Reference:
1. http:sensing.honeywell.com/index.php?ci_id=47847 accessed on 11 Jan 2013

Platform Services for IMA 2G

With the development of 2G for IMA, the existing 1G infrastructure is modified to meet the needs of the system. This short presentation by SCARLETT provide the overview of the transition.




The above video is a presentation made by SCARLETT -  a company involved in the development of the IMA (Intergrated Modular Avionics), with the quoted partners, Airbus, Sysgo, Skysoft and Thales.


 Advantages of IMA2G - The images extracted from the above video.