How airplanes communicate to ground?

Possibly everyone knows or can guess that airplanes use satellite phones to connect to ground. That’s true, but not entirely.

Satellite Communication or SatCom is just one of the ways to communicate to the ground systems. And this is one of the most expensive ways to do so. Did you ever use the phone on the airplanes which is also the remote of the IFE (In-flight entertainment system) and for which you were to swipe your credit card to pay USD 5 per minute as call charges? Remember? That phone is connected to SatCom and the $5 more or less go to the satellite communication company. Airlines don’t make money on your calls, it is/was just a service to te passengers. Anyways, let’s get back to our discussion.

There are various ways through which airplanes communicate to the ground. These are:

  • Sattelite Communication System (SatCom)
  • HF (high Frequency) Radio
  • VHF (Very High Frequency) Radio

We don’t normally notice, neither we get an opportunity to notice that all airplanes have multiple antennas sticking to their bodies. These antennas can vary in size, so much so that one might be of a size of a cigarette case and one might be over 6 feet long and a feet high, e.g. Inmarsat antennas.

The most basic explanantion of this communication system is that it is very much similar to the home Wi-Fi. There is a uplink (e.g.my laptop), a datalink (the router) and a downlink (the server).

Primarily, the typical aircraft’s air-ground communication depends on something called ACARS which stands for Aircraft Communications Addressing and Reporting System. Some interesting details can be found at Wikipedia which states it as a digital datalink system for transmission of short, relatively simple messages between aircraft and ground stations via radio or satellite. The protocol, which was designed by ARINC to replace their VHF voice service and deployed in 1978, uses telex formats. SITA later augmented their worldwide ground data network by adding radio stations to provide ACARS service.

ACARS messages are transmitted over one of three air-ground subnetworks.

  • VHF is the most commonly used and least expensive. Transmission is line-of-sight so VHF is not available over the oceans or other vast expansions of uninhabited surface, such as the Amazon.
  • SATCOM is a fairly expensive service that provides (near) worldwide coverage. The Inmarsat satellite network does not cover the polar regions. The Iridium satellite network became usable for ACARS transport in 2007 and provides excellent coverage in the polar regions.
  • HF is a more recently established subnetwork. Its purpose is to provide coverage in the polar regions where Inmarsat coverage is unreliable.

Obviously, the new communication methods or protocols like Iridium have been developed and the next Gen aircraft use them too. The iridium antenna is also very small in size which is very beneficial to airlines. Does size matter? Yes it does. The smaller an antenna is, the lesser drag is. Drag is the aerodynamic force that opposes an aircraft’s motion through the air. NASA has developed a website to teach school & college students about principles of aviation. I highly recommend this website for anyone interested in this subject.

Ohh, I din’t notice that it was too late and I have a lot to accomplish at work tomorrow. I will be adding few pictures & drawings to make these concepts more understandable. I will also be relating these concepts to Testing world to make them more interesting to our testing community.

A little about airplanes

We all fly in the airplanes. Some of us fly more than others. I fly almost every few days or months. Be honest, tell me how many times you thought how these most beautiful machines, which are hundreds of times heavier than air, fly in the air or communicate with the base on ground even when they are thousands of feet above ground?


Not only that, did you ever think how these machines and their communications systems are tested? Let me tell you one thing, knowing an aircraft’s internal designs and also knowing how it get tested is really very interesting. Even the most basic type of aircraft’s design are very complex. The larger and more advance an aircraft is, the more complicated it is to understand the architecture or design. 


Anyways, we are not really discussing the complexities of internal designs of an aircraft here. We are more interested in knowing:

1. How airplanes connect to ground
2. How aircraft communication systems are tested
3. What are the software that are used on airplanes
4. How these software are tested
5. What qualifies the testing on airplanes
6. Do we need to worry next time we fly whether software has been tested properly or not

All the questions I have listed above are the questions that people ask me. I cannot really answer all of them right here because each one of them requires a really long explanation. Let me write it down for you. In the next few days I will be adding more on the same interesting subject. 

Stay tuned..

My biggest Challenge today: AST sponsoring another testing event for Hong Kong Testers

On November 06, I posted on this blog about the upcoming AST testing event in Hong Kong:

I am pleased to inform that AST has agreed to sponsor the second Context-Driven Peer Conference for Hong Kong’s Testing community. I will be adding more details soon about the format, date and venue of this event.

The topic of the conference is Best Practices v/s Context-Driven Practices.

If you wish to be part of this peer conferecne, please reply with a message to me.  Let us know if you align yourself with the Context-Driven Testing approach/school. Also provide details of your contribution to Testing Community.

Please note that this conference is invitation only. So the better your message is, the more changes of you to be invited.

Stay Tuned for further information!

I saw Matt’s email about AST Grant when I was on vacations in Sydney late in October. I was glad that AST had sponsored another tetsing event for Hong Kong’s testing community in 2012 and this should be counted as an achievement. I posted the event details on various forums including LinkedIn & Twitter hoping that people will swamp my inbox with requests. They did! But I was hoping that I will get quality requests. Requests from thinking testers; from people who love testing and are enthusiastic about its advancement as a practice. People like us who are reading this post. But the requests that I have received are from ‘Business Development Managers’ of so-called testing body-shops who keep smelling for networking opportunities with anyone who is a part of senior management group and might throw a piece of meat at them so that they can get few more contractors to fit in as ‘test managers with X amount of years of experience in test management with world’s finest company with ISTQB Foundation and intermediate and Management certificates’. Hang on dude, tell me if this guy has any understanding of context-driven testing? Can he stand up and get challenged for his views on testing by a group of us? Possibly no!
Then I don’t need these people neither as employees nor as attendees at my Testing Event. I would rather postpone the event than accepting requests from “ISTQB certified Test Manager with X amount of years of experience in test management”.

My biggest challenge in Hong Kong has been finding people who are enthusiastic about technology, especially testing. Hong Kongers love /using/ technology. They like to spend money on gadgets. They like to buy the latest iPhones and Samsung galaxys and ipad minis; but they do not want to stop and think about anything more. They just play games on them and watch Gungnam style dance. That’s it!

Not even a single sincere tester! Not a single thinking tester. 🙁

You might say this is an opportunity. Yeah, I guessed so! But in truth, this is the biggest challenge for me today. Sigh!!