Condign volumes 1 to 3

Read from the scan by GLM-OCR; expect the odd misread word.

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because of the huge numbers of aircraft flying certainly much more night flying than had been carried out in the short history of manned flight.

42. It is stated that large radius ball lightning (similar plasma bodies) can 'chase' aircraft while maintaining shape and more or less constant distance from the aircraft. The 'ball' is able to do so because it is not solid (otherwise a thrust force of thousands of Kg would be needed)! It is postulated that the layer of air adjacent to the surface of the ball loses its viscous properties. The ball follows the aircraft even in manoeuvres. Observations of ball lightning show that its characteristics do not change appreciably during its lifetime. When it is in the airstream of an aircraft it is postulated that it behaves as a non-deformable solid sphere in the airflow which holds its position due to the electrical/magnetic charges, described elsewhere in this Working Paper. The main reason for interest in close encounters of aircraft with ball lightning is one of flight safety. It is reported that large balls can be comparable with body diameter of large aircraft and can be 'captured' by the exhaust from engines and 'chase' the aircraft at a velocity of $ 1 5 0 - 2 0 0 \mathrm{m}. \mathrm{s}^{-1} $ (278-370kts), maintaining an apparent constant range from the tail assembly.

43. One (TU134) pilot reported that at an altitude of 10,000ft and flying at a velocity of 800km $ \mathrm{hr}^{-1} $ $ (-220\mathrm{ms}^{-1}) $ , the ball (in this case green) "appeared as though tethered behind the aircraft". Another (Russian) crew report, when flying at 7500ft altitude were 'followed' by a huge ball which was still in 'pursuit' after a fast descent to 4500ft. It refused to leave despite manoeuvre - which was limited for an airliner.

44. If the moving object were solid it would take the force of many Newtons to make it follow an aircraft. Clearly the ball is sensibly weightless (apart from the mass of the gases it contains). It is believed that the electrical charge of the ball diminishes as ionisation of the air-layer in contact with its surface occurs. The USSR treated the ball lightning phenomenon as very important and

Gaidukov [3] reported after modelling the interaction that:

- All efforts should be made to avoid lightning seen ahead (before a ball is formed).

- To avoid the chance of an encounter with a ball, pilots should encircle around a vertical line passing through the centre of the lightning'.

- Pendulum-like undulations in altitude may be seen (by balls ahead), and every effort should be made to place the ball astern, where it will assume a stable position.

- The balls cannot 'catch up' the aircraft once the pilot has ensured that the ball is astern.

- The ball will dissipate. Reports of 10km (tail chase!) are not unusual.

45. Several comments can be made:

(a) The instances of phenomena of ball lightning ahead of, or behind, aircraft is relatively rare, but the Russian research suggests, apart from initial lightning avoidance, that the aircraft would be safe with the ball astern.

(b) Reports of balls above aircraft 'pushing or forcing'an aircraft to descend are of concern, even if the ball does not cause physical damage its presence is clearly menacing to the uninitiated - especially as it occurs suddenly.

(c) A 'collision' from astern is not considered likely.

(d) A 'collision' head-on is possible and its imminence might cause violent pilot (control) reaction even though the contact may not (at the last moment) have actually occurred.

The 'stand off' of the ball lightning from an aircraft seems to be very much like the situation encountered in several scenarios where pilots have been scrambled to investigate 'UFO' sightings. A scenario where this occurs not only involves the 'stand-off' described here