For aerial photography to
be successful, the primary requisite is that the survey area should be completely
cloudless. Camera filters can film through haze of reasonable density, but cloudless
conditions are imperative. Completely cloudless conditions can be rare events,
especially in places such as Papua New Guinea, where it was acceptable to photograph
over minimum cloud patches. But it was then usual for the area to be photographed
a second time with the expectation that the area obliterated by cloud on the first
occasion probably would be clear of cloud on the second.
Regulations required that we observe flight time limitations daily, weekly, monthly
and yearly. These limitations were usually not restrictive. For example, the monthly
maximum was 100 hours and the annual maximum flight time limitation was 1000 flying
hours. On survey flying, about 500 hours annually was about the usual number flown
under normal survey conditions.
At times our crew would have two separate operations to perform. We would rise
early for an oil survey flight to make the most of calm conditions for the magnetometer,
and this flight would frequently be completed early because of turbulence. We
would be back on the ground by 8 am and sometimes earlier. We would then refuel
the aircraft, remove the magnetometer and install the camera for high level (for
those days) photography. We would then be airborne again by about 9 am if the
weather was cloudless and climb to 25,000 feet for perhaps a full day's photography
of 5 hours and 45 minutes. It was to cover these rare occasions when we didn't
want to miss out on repeated days of suitable photographic weather, especially
after the flight time of regular oil survey flights, that Adastra obtained a concession
from the then Department of Civil Aviation to the effect that we could fly 120
hours in any one month, providing we did not fly more than 200 hours in two consecutive
Flying is, for most pilots, an enjoyable occupation and it was no hardship to
fly to the maximum allowable, especially when it occurred so rarely. It has been
only in recent weeks when looking through my log book to check the accuracy of
dates etc. I noticed during the month of June 1963 I flew 120 hours and 15 minutes!
(It would probably have rendered the aircraft insurance invalid had we pranged
during those 15 minutes!)
25th August 2004.