THE HONG KONG GOVERNMENT GAZETTE, MARCH 12, 1937.
No. 178.
DIRECTORATE OF AIR SERVICES, HONG KONG.
Notice to Aircraft Owners and Ground Engineers.
No. 6 of the year 1937.
CROSS LEVELS: RISK OF BURSTING.
Cases have occurred of cross levels bursting when left exposed to the sun in countries with a hot or moderately hot climate.
The risk of this happening will exist with all cross levels of the "steel ball" or "bubble" type in which there is no expansion chamber (the absence of which may be detected by a visual examination). It will also be present, though in lesser degree, where there is an expansion chamber of insufficient capacity.
It is therefore recommended that aeroplanes fitted with either of these types of cross level should not be left out in the open under a hot sun, unless the cross level is suitably shielded.
No. 179.
G. F. HOLE, Director of Air Services.
8th March, 1937.
DIRECTORATE OF AIR SERVICES, HONG KONG.
Notice to Aircraft Owners and Ground Engineers.
No. 7 of the year 1937.
DIAL INSTRUMENTS, MARKING OF.
1. Attention is drawn to the need to ensure that all dial instruments are clearly marked to show the units in which they are calibrated. Airspeed indicators, for instance, may be calibrated in miles per hour or in kilometres per hour, and the unit employed is immaterial provided it is clearly indicated on or immediately adjacent to the dial. Similar considerations apply to other dial instruments such as altime- ters, pressure gauges and thermometers.
2. Ground engineers should verify that instruments on aircraft under their charge are marked as indicated above.
3. Air Ministry Civil Specifications for dial instruments do not at present contain any clause dealing specifically with the need to indicate on the dial the units used. A clause to this effect will be added to Civil Specifications, where relevant, at the next convenient opportunity: meanwhile, instrument manufacturers should not release for use on civil aircraft any dial instruments unless the units in which they are calibrated are clearly indicated.
G. F. HOLE, Director of Air Services.
8th March, 1937.
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