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FDC
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 […]

FDC
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 […]

FDC
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 […]

FDC
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. […]

FDC
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 […]

FDC
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 […]

FDC
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 […]

FDC
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 […]

FDC
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 […]

FDC
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 […]