RAF fighter jet preparing for takeoff at the SW extremity of RAF Lossiemouth air base. Beside the plane is a mobile air traffic control tower ( ATC ) or aka "runway caravan".
[Thanks - Jim Bain] ....
They tend to get used ...
a) On airfields with no proper ATC ie temporary runways on deployment
b) When the main ATC is out of action or not working properly for what
ever reason.
c) On some airfields the far end of a runway may be out of sight from
the main ATC due to the lie of the ground, not all runways, in fact
very few RAF ones were truly flat. Most slope one way or another and
some even have a hump in the middle.
The far western end of RAF Lossie is out of line of sight of the tower at eastern end of the station and so they use a mobile tower to keep an eye on departing and arriving aircraft - also it's a very long runway.
When flying is finished for the day the mobile tower trundles back to be
parked till next required.
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