The International Standard Atmosphere
Dave Jesse on June 29, 2017

  For most purposes the properties of the air we fly in are described by the International Standard Atmosphere (ISA). This makes some assumptions about what is a normal day, then computes the air properties at different altitudes. In this blog I am going to give you the fastest explanation of how the ISA works […]

From Using Quaternions for Visualisation
Dave Jesse on June 6, 2017

  To my regular readers, I apologize for the absence of a blog in recent weeks. A severe tummy bug during a conference in Seoul followed by a shocking bout of jetlag in Phoenix (Thursday in Seoul and Monday in Phoenix via a weekend in Coventry is not to be recommended) are my only excuses. […]

Monitoring Small Aircraft 2
Dave Jesse on May 18, 2017

  Background In January 2015 I wrote a short blog entitled “Monitoring Small Aircraft”. It described how we can monitor relatively small aircraft when they are equipped with modern digital avionics. Specifically (and please don’t interpret this as advertising) the Garmin G1000 system, which includes a data card facility for recording flight data. The original […]

Following the Taxiways
Dave Jesse on April 21, 2017

In this blog I will explain how we compute the ground track for visualisations and why this is undergoing a process of revision. What the User Sees When we process flight data we often show the flight on a chart or, most commonly these days, on Google Earth. It is easy to see where the […]

What is the Groundspeed?
Dave Jesse on March 15, 2017

  Recently a customer asked whether the groundspeed recorded by the flight data recorder was right. They had (allegedly) exceeded a taxi speed limit by a large margin and suggested, very politely, that we had got this wrong. This prompted me to do some checks and as the results were interesting I thought I would […]

Why Two Vertical Speeds?
Dave Jesse on February 20, 2017

Following on from last week’s blog about rates of change, it occurred to me that I should have mentioned the second computed vertical speed and explained why we have two measurements for the same thing. After all, surely the vertical speed is exactly that. Why have “Vertical Speed” and also “Vertical Speed Inertial”? Quick Look […]

Rates of Change
Dave Jesse on February 13, 2017

One of our analysts asked if I had written a blog about how we calculate vertical speed, and I said “of course I did, ages ago”. There followed a 15-minute hunt for the subject and eventually I had to admit that it was missing, so here goes with a quick blog to plug a gap […]

Where an Aircraft Lands – Part 3
Dave Jesse on February 6, 2017

We found out which airfield the aircraft landed at, and now need to pick the right runway. Selecting the Runway From basic flight phase analysis we know when the landing roll took place. Using the recorded heading we take the median heading during the landing roll as the direction of the runway. Note that we […]

Where an Aircraft Lands – Part 2
Dave Jesse on January 30, 2017

My last post talked about some of the problems with finding out exactly where an aircraft lands. Now I will start to look at how the system works in practice. Pick an Airfield I will skip over the detail of how to identify the point of landing (this was covered in an earlier blog), so […]

Where an Aircraft Lands
Dave Jesse on January 13, 2017

Some time ago I was asked to write about how the POLARIS software decides where an aircraft lands. At the time we knew of some limitations of the system and were planning to revise that part of the analysis, so it seemed sensible to hold on until that revision had been completed. These limitations have […]