This may answer your question, taken from here Free Balloon Operations in World War TwoAt the risk of bogging down in detail, how is the deploment of the towing parachute enacted?
The resulting weapon fitted into a cylindrical container 14in long and 7in in diameter, and weighed 141b. After release from the aircraft the obstacle deployed.
It comprised, from top to bottom: a supporting parachute, a length of shock-absorber cord, the cylindrical container, an AAD bomb, 2,000ft of piano wire and, at the bottom, a second furled parachute.
When an aircraft struck the piano wire the shock wave ran up the wire, causing a weak link to break, releasing the main supporting parachute and the cylindrical container. As the container fell away the bomb was armed and a small stabilising parachute connected to the weapon was released. Simultaneously, the shockwave travelled down the piano wire and caused the lower parachute to open. This took up a position behind the aircraft and pulled the bomb smartly down on the aircraft.
However, in autumn 1940 Fighter Command's most difficult problem became how to counter the night raider. The long-term answer was the Bristol Beaufighter, fitted with airborne interception (AI) radar, directed on to its prey by a ground-controlled interception (GCI) precision radar. But each of those systems was in an early state of development, and some time would elapse before they were available in quantity. In the meantime, anything even remotely likely to be effective against the night bombers was pressed into use, including the Long Aerial Mine. German bombers attacking at night did not fly in formation. Instead, they approached their targets at irregular intervals, following their radio beams. At night, the mines were to serve a different purpose than that originally proposed. Instead of being used to split up an enemy formation, a line of mines would serve as an "aircraft trap" to destroy bombers.
Somewhat obsolete Handley Page Harrow twin-engined bombers were used for aerial mine laying. The device was successful as in 1941 there were six German bombers destroyed by the Pandoras.