User manual

Section Appendix A.1 Part B
water overruns the deeper water and the wave breaks. Breaking waves should be avoided
by pilots!
Wave activity around obstructions is varied but predictable. Wave propagation speed
generally decreases, wave direction will change according to where the wave is first
affected by the obstruction, and wave height often decreases. Hence the use of
breakwaters in and around harbours
12 WAVES RELATED TO HULL LENGTH
– Wavelets: 10 or more waves per hull length. Always live waves, will lie perpendicular
to wind and move with it, and provide good cavitations to aid in unsticking the aircraft
on take-off.
– Short waves: 4-7 wave crests per hull length. Almost always live waves, generally
good operating conditions though rougher than above.
– Medium waves: Wave length comparable to hull length. The most dangerous wave
form for flying boats since broaching is a risk. Usually needs the sea or a very large
lake for Catalina sized medium waves to develop.
– Long waves: Length greater than the hull length. In general it is easier to handle
the flying boat in these conditions than with medium waves. The longer the wavelength
the more readable and predictable the wave system becomes.
13 TIDES
Tide effects are due to the relative gravitational pulls of the sun and the moon. The
strength of the tide in any body of water depends on the size of the body, the relationship
of the sun and moon positions and the patterns of water flow in the body. The main
problem for the seaplane pilot is the change in water level associated with the tide flow.
Differences may be only a few centimetres in some large lakes but may reach 10-15
metres in some ocean areas.
14 CURRENTS AND WATER LEVELS
These may be drift currents caused by wind, tidal currents, or water flows associated with
temperature gradients in the body of water. All currents are modified by the Coriolis-effect
(right deviation in northern hemisphere). Lake outflows into rivers will often produce
current effects some distance back into the lake and pilots should remember that the
outflow from many lakes is regulated for hydro generation and may change at any time.
For the same reason, pilots must be prepared to find river and lake levels quite variable,
even over relatively short periods of time.
Rev No: 02 Stichting Catalina PH-PBY
Page: 4 01 April, 2006