User manual

Section Appendix A.1 Part B
02 AIR
The behaviour of air in the atmosphere and the interrelationship of temperature, pressure,
density, humidity, dew point, freezing level etc should be known to all pilots. Atmospherics
affect water flying more than land flying because of the changes air movement causes to
the landing and take off areas. The effect of air density on aircraft performance must be
remembered in all conditions.
03 WIND
Air movement (wind) is particularly important because of the influence it has on the water
surface and the effect it has on the aircraft when it is on the water. For example, wind can
cause difficulties with taxiing and if gusts are erratic landing can be dangerous. Particular
types of wind are likely to influence water operations with PBY:
04 SEA BREEZES AND LAND BREEZES
Heating of the land during daylight produces upward movement of air over the land and
cooler more dense air is drawn in from over the sea (or large lake). This onshore
movement of air is the sea breeze and normally is noted late morning and is most intense
at from mid to late afternoon. Wind strength can reach 15-20 knots
More rapid cooling of the land
overnight can produce a less intense air flow from land to sea during the night but this is
rarely stronger than 10 knots.
05 VALLEY AND MOUNTAIN BREEZES
More rapid cooling of air at altitude leads to downhill and down valley air flow at night
(mountain breeze)
The rise of more rapidly heated valley floor air during the day can give an up valley wind
direction of importance around mountain lakes (valley breeze).
06 ANABATIC AND CATABATIC WINDS (STAU AND FÖHN)
Warm strong winds in the lee of mountains (e.g. the Canterbury Northwester) will produce
conditions of good visibility until dust becomes a problem, but lake and sea conditions tend
to be rough or very rough.
07 EFFECT OF LAND AND WATER
The lee sides of islands and "venturi" effects on narrow lakes and rivers are examples of
the land affecting the wind conditions often to the detriment of the seaplane pilot.
"Boundary layer" effects where the wind speed drops as it is measured closer to the water
surface also occur resulting in wind-shear and turbulence. For example, a wind of 20 knots
at 50 feet above the water may be only 10 knots at 6 feet above due to surface friction
retarding the air flow. This change may be enough to ruin an otherwise satisfactory
approach.
Rev No: 02 Stichting Catalina PH-PBY
Page: 2 01 April, 2006