From Autocorrelation to Fourier
Dave Jesse on September 12, 2017

Just for fun Here is a little interlude to get back to helicopter accidents – and do some more tricky maths in the process. Autocorrelation Here are two combs from the previous blog, which was about autocorrelation. You will recall that we compared one comb with another to see how good the match was.   […]

Decoding the Falcon – Part 2 Triple Teasing
Dave Jesse on August 17, 2017

Well, I cheated. The autocorrelation plot at the end of the last blog was particularly poor because I included the text header of the file and only processed the first 1000 words. It looked like this: Simply by removing the text header (which is clearly not part of our repeating patterns) the plot improves to […]

Decoding the Falcon
Dave Jesse on August 9, 2017

Decoding the Falcon Occasionally an aircraft operator will send us data that is in a format we have never seen before. The aircraft maintainer has followed the manuals and downloaded a data file and sent this to us and, quite reasonably, he thinks we must be able to read it. He supplies all the information […]

Under Pressure
Dave Jesse on August 1, 2017

  I couldn’t resist the opportunity to quote from Queen and Bowie. Or just show my age as I remember Under Pressure as a new song, not a golden oldie. Actually we’re going to have a quick look at pressure measurements. Like this:     Pressure Units As the gauge above (I cannot bring myself […]

On Non-ISA Days
Dave Jesse on July 13, 2017

Non-Standard Day In my last blog I looked at how the characteristics of the atmosphere are computed from some simple assumptions. Namely that the air is at a high enough pressure to hold up the air above it and that there are simple relationships between the temperature and altitude. Today we are going to look […]

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 […]