User:Johan G/Flight computer

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A flight computer calculates various flight related variables. This article will more or less be about the hand held ones, specifically the E6-B and CR types, while there also has been analogue electronic and digital electronic, ones over the years.

General concepts

All of them pretty much does the same thing. There's a lot of calculation during flight planning that have to be made related to the direction you are flying in, the air speed you are flying at, the effect of the wind on the your direction and air speed:

  • Firstly, all maps show true north, while navigation almost exclusively is done by magnetic north. The winds are also reported in true north.
  • Secondly, the air speed shown by your airspeed indicator, the indicated airspeed or IAS, is not the same as the speed you actually do have, the true air speed or TAS, as there is a varying difference between them, mainly dependent on altitude.
  • Thirdly, unless you are flying in still air the TAS is actually not the speed you have over the ground, the ground speed or GS. If you have a head wind coming towards you, your GS will be slower than your TAS, and the opposite if you have a tail wind coming from behind.
  • Fourthly, if you have the wind from the side, you will drift off from your track. To stay on track you will have to head into the wind. This results in that the (magnetic) heading, or MH, you will have to keep to get to the next checkpoint isn't the same as the direction from the last checkpoint to the next, the (magnetic) course or MC. Also since the wind is pushing from the side it will change your GS, though not as much as a head or tail wind.

On top of that there are also other calculations, but many of them uses other tools, like diagrams and tables. Such calculations can be fuel flow, range, take off speeds and distance, landing distance, aircraft performance under unusual conditions like hot air at high altitude etc.

The E6-B and the CR types of flight computers

There have been many variants of flight computers over the years, but the two ones that seem to stay are the E6-B and CR variants. While both basically does the same calculations, they get to the result in different ways, which is also reflected in their appearance. Put in simple words: The E6-B has a sliding chart in the middle and the CR is bolted together in the middle

In use the E6-B's work flow is more logical and easy to remember, while the CR is a bit more convenient in that all parts rotate around the centre and is easier to use with one hand alone e.g. when holding the yoke.

Similarities and differences

While both have a calculator side and a wind side, the appearance of the calculator side is almost identical.

The calculator side

The wind side


Time, distance and speed calculation

Ascent and descent calculations

Fuel calculations

Density altitude calculations

External links