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The Use of Barometric Charts in the Navigation of Airships1

Published online by Cambridge University Press:  28 July 2016

Norman L. Silvester
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Extract

Experience has shown how dependent is the airship upon weather conditions —more particularly for a safe ascent and descent. The numerous experiments with windscreens, tractors, mooring posts and landing gear emphasise the difficulty of handling an airship on the ground and of manoeuvring it in and out of its shed.

It is in the endeavour to minimise these risks that this study has been undertaken. In the discussion as to the most advisable course for an airship to adopt for its own safety when surprised by unfavourable weather, it should be remembered that in all the examples which follow, it is a case of “making the best of a bad job”; and that no pilot would wittingly leave his base with the knowledge of such bad weather impending except under pressure of war time necessity. It is hoped to demonstrate that in some cases it might be possible by skilful navigation, aided by the frequent communication of isobaric charts by wireless telegraphy and by accurate positions given frequently by the same means, for a pilot to keep in the air during the passage of bad weather and thus avoid the risk of wreck by attempting a premature landing.

Type
Research Article
Information
The Aeronautical Journal , Volume 31 , Issue 193 , January 1927 , pp. 60 - 80
Copyright
Copyright © Royal Aeronautical Society 1927

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Footnotes

1

This paper was written in 1918, whilst serving with the Naval Meteorological Service. At the time of transfer to the R.A.F. it fell into the hands of the Meteorological Office, to whom application for permission to publish was made in 1921. Permission was refused, but four years later, when the R.33 broke adrift from her mooring post, the Meteorological Office advised flying a course suggested in this paper, with which they were previously in disagreement. Permission was then given for the publication of the paper.

References

2 Miles per hour.

3 Barometer Manual, M.O. 61, 1916, p. 77.

4 Examples.—The period between October, 1919, and April, 1920, chosen at random, gives eight instances, vide 7h. synoptic charts on the following dates:—27th October; 19th December;. 3rd, 11th, 30th January; 15th March; 16th, 20th April.

5 Silvester, Q.J. Met. Soc, Vol. XLV., No. 190, page 171.

6 y/ρ = 2ωV sin ƛ± (V2/R) cot α

where y = pressure gradient

ρ = density of air.

ω = angular velocity of earth

V = velocity of air

ƛ = latitude

R = radius of earth

α = angular radius of small circle

due to Ferrel, Guldberg and Mohn, vide Sir Napier Shaw, Forecasting Weather, pp. 42-5.

7 G. I. Taylor deduces from data published by J. S. Dines, in Technical Report of Advisory Committee on Aeronautics, p. 216, that the diameter of an eddy formed in a wind velocity of seven metres per second at the surface is greater than 40 metres. Phil. Trans. Roy. Soc, Series A, Vol. 215, p. 22.

8 This alternative is not shown on the chart.

9 Silvester, “Weather Conditions at Mullion, Cornwall,” Q.J. Met. Soc, Vol. XLVI., No. 195, 1920, pp. 251/2.

10 Not shown on the course chart.

11 W. N. Shaw and R. C. K. Lempfert, “Life History of Surface Air Currents,” M.O. 174, 1906, pp. 18-20.

12 It is understood that experiments on these lines were conducted at an aerodrome in East Anglia shortly after this paper was written.