The helicopter was owned or taken possession of by the Headmaster and featured in 'The Prime Minister's Brain.' It was controlled via Super Salamander and was located in the underground carpark of Saracen Tower.
SPLAT first encounter the machine when they are looking for a way into the tower because Super Salamander will not grant them access.
The Headmaster later escapes in the helicopter and sets course for Downing street to complete his plan, however using Super Salamander Dinah takes control of the helicopter and after considering crashing it, pushes it up towards the sky before escaping the burning building.
In the TV Series of 'The Demon Headmaster Takes Over' the helicopter is seen taken back control after becoming unstable and landing in the grounds of the Biogenetic Research Centre. A logo of the Octopus seen in Saracen Tower is shown on the side of the helicopter as it touches down, which is the last time we see it.