Instrument Flying: Technique in Weather Page: 63
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T. O. No. 30-100D-1When available, landmarks in the immediate vicin-
ity of radio fixes should be chosen. If, because of
cloud or fog, the position check must be made by
radio, the precomputed estimates will still hold good
and will permit the pilot to determine his gain or loss
of time. This is particularly important when accurate
data on the wind at the flying level are not available.
A succession of fixes provides the only way of deter-
mining ground speed, and when the fuel supply is
limited this becomes vital to the successful completion
of the flight.
Regardless of the weather conditions, the compass
course and heading to be flown should be calculated.
The course should be marked on the map, together
with a reciprocal course, and during flight the compass
heading should be frequently checked against the avail-
able landmarks. Confidence in instruments can be de-
veloped only by skill in their use and frequent checks
of their accuracy.
Pilots of single-place aircraft must be particularly
careful in the use of flight plans, since there is no
navigator available except the pilot himself. A pilot
who claims that flying the airplane requires all his
attention is in reality claiming that he is able to do
only half his job. Accurate flight planning and ac-
curate checks of position are necessary because in-
strument conditions may develop at any time, and
unless the ground speed and definite course are known,
the fuel consumption, gyro heading, and other impor-
tant factors cannot be worked out without detailed
computations requiring considerable time and at-
tention.
YOU THINK YOU'RE THERE; BUT ARE YOU? UN-
LESS A PILOT KNOWS HE IS WHERE HE
THINKS HE IS, HE IS IN DIFFICULTY
Many an experienced pilot can recall times when
even in contact weather he became hopelessly lost
or was forced down by lack of fuel because he did not
follow elementary flight plan procedures. It can and
does happen. When the ceiling and visibility is low,
the situation becomes even more acute. To cite a
typical example:
On a night flight, with the weather clear and un-
limited, a pilot failed to check his position along a
beacon-lighted airway. He had expected a tail wind
but was actually not making good the speed he thought.
To check his position he finally identified a beacon by
its code flash and located it on his map. What he did
not know was that while concentrating on his map he
had permitted the plane to make a 180-degree turn,
catching it just as it reached the reciprocal heading.
Sure enough, there was the beacon passing below,
flashing its code.
On the reciprocal course but reassured as to his
"position," the pilot settled down to a contented hour of
flying. His amazement and chagrin when he landed,
for fuel, at his original point of departure, can be
readily visualized.THE MINIMUM SAFE ALTITUDE
A pilot should never take off without knowing the
nature of the terrain and the elevation of obstructions
along the route to be flown. The airways map must be
closely examined and the highest points on the route
prominently marked. From these notations a min-
imum safe altitude can be arrived at; the pilot should
never fly lower than this minimum unless contact
flight can be maintained with unlimited visibility.
In mountainous country, particularly in winter when
the higher peaks are snow-covered, contact flight be-
low the level of the highest terrain must be under-
taken with caution. Snow-covered peaks frequently
blend with the sky background or with the distant cloud
bank; and if the visibility is poor, they may not be
seen for what they are until too late.
On instrument flight, especially when a low approach
on instruments must be made at a terminal, the correct
ground elevation and the height of obstructions must
be accurately known. The pilot should never assume
that the terrain around an airport is level or be sat-
isfied to know the elevation of an obstacle "within a
few hundred feet." Even the' western prairies have
local hills that rise hundreds of feet, and the-appar-
ently level country side slopes upward toward the
foothills of the mountain ranges.
Abrupt changes in elevation of the terrain.have a
definite influence on weather, particularly when the
wind is blowing up the slope. A deck of stratus clouds
over the lowlands will turn to dense fog over higher
terrain., Many apilot has been deceivedby a "lowered
ceiling" that was in reality up-sloping terrain.
From above an overcast, mountains or ridges be-
low the clouds will frequently show as undulations in
the top of the layer due to eddy currents above the
crests of hills. This is, however, no accurate indica-
tion unless a steady wind is blowing at the lower level,
If the wind is calm or light, the cloud decks will not
show any variations even when mountain peaks rise to
within a few hundred feet of the top of the cloud layer.
THE GROUND IS WHERE YOU HIT IT
As far as obstacles are concerned, it is never safe
to make assumptions concerning your position unless
you have a definite radio fix. The sort of trouble you
can get into is illustrated by the following incident:
East bound on instrument in a snowstorm, a
pilot was having trouble reading the radio range signals.
While he was sure he was on course, he was not cer-
tain how far out he was from the range station. Since
the country was mountainous, he held a safe altitude
until he estimated his position to be a few miles west
of his destination, an airport at elevation of 5,100 feet.
Following the on-course signal, the pilot slowly
lost altitude, expecting to break out of the overcastRESTRICTED
Section 11
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63
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Army Air Forces. Instrument Flying: Technique in Weather, book, January 1, 1944; Ashland, Ohio. (https://texashistory.unt.edu/ark:/67531/metapth873973/m1/69/?q=+date%3A1941-1945&rotate=90: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting National WASP WWII Museum.