CAB80-25 — Page 53

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APPENDIX C.

NORTHERN IRELAND EXPERIMENTAL SCHEME.

An oil burning generator scheme has now been organised in Northern Ireland. The dummy "vital target" is Cogry Mill, Doagh, about 14 miles northwest of Belfast.

Up to the present date three operations have been carried out during moonlight. The results are as follows:-

(1) 14th December.

Meteorological conditions were not unsuitable for the formation of a smoke screen and the moon was full and very bright. There was no ground mist and the general visibility was very good. Smoke was emitted from 5.45 p.m. to 10.15 p.m.

From the ground the smoke appeared to be covering the target very effectively; but the pilot and observer, who were over the target from 7.30 p.m. to 8.0 p.m. and from 9.45 p.m. to 10.10 p.m., reported that, except from a very low altitude, no smoke could be seen over the target and that the target was visible from all heights. The report added, however, that a more effective screen had formed about five miles down wind where the smoke had risen to 1,500 feet.

It is not suggested that the following necessarily provides a full explanation of this unfavourable report, but the facts should be placed on record, Owing to a mistaken signal the operating personnel temporarily extinguished a number of generators soon after 7 p.m., so that by 7.30 p.m. the density of the screen had diminished considerably; it is also known that after 4 hours' operation the smoke emission from the generators tends to diminish, It will be observed that, by an unfortunate co-incidence, the times at which the density of the screen might have been expected to be at a minimum, in consequence fall within the periods during which the observing aircraft was overhead.

(2) 16th December.

Meteorological conditions were again not unsuitable and the moon was very bright. There was no ground mist and visibility was exceptionally good. Smoke was emitted from 7.30 p.m. to 10.30 p.m.

From the ground the smoke appeared to be covering the target very effectively - in this respect there was little apparent difference between this screen and that produced on the previous occasion,

The observing aircraft was over the screen for one hour. The pilot and observer reported that:-

(a) No difficulty was experienced in locating the target area. (b) The smoke was visible as a screen 2,000 yards x 4-5 miles the screen was most effective 1 mile downwind from the target.

(c))The target was just invisible at 6,000 feet and hazy from

overhead at 2,000 feet.

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