User manual

Part B Section Appendix A.4
Water surface
conditions can affect takeoff run and especially important is the difficulty unsticking the
aircraft off glassy water. Hull resistance is reduced by cavitations of wavelets on the rear of
the hull.
Humidity
affects takeoff run by its effect on density. Humid air is less dense so in high humidity
conditions as are often found round large bodies of water, take-off performance may
suffer.
Centre of Gravity
position has a variable effect. A rearward CofG makes it harder to get the aircraft up onto
the step but once on the step a rearward CofG makes getting off the water easier and
shortens the takeoff run.
10 TAKEOFF TECHNIQUE (NORMAL CONDITIONS)
Preparation for a water takeoff is complicated by the fact that the aircraft will be moving. A
good lookout must be kept while at the same time completing the takeoff checklist. It is
sometime best to leave asymmetric power set (say 800RPM on one and 1100RPM on the
other so that the aircraft turns in a gentle circle during the pre-takeoff checks. The risk of
hitting shoals, reefs, boats or other obstructions is reduced if the direction of movement is
planned and controlled by the pilots.
Once pre-takeoff checks are complete, the aircraft should be taxied into win< until clear of
its own swells. The line-up checklist is then completed.
With the control column hard back, power is smoothly and quickly increased the takeoff
setting of 48 ins Manifold Pressure.
As the aircraft moves forwards and climbs the water "hump", visibility forward will be
temporarily lost due to spray and water over the windscreen. Gyro heading reference
should be noted before this and the heading maintained. Wings should be kept level by
aileron input as soon as this is effective. The nose will rear up until the aircraft "climbs" up
onto the step. Once there the control back pressure is relaxed until the aircraft is
hydroplaning in a slightly nose up attitude.
By adjusting the nose attitude slightly the best acceleration can be felt. With the nose too
high flying speed will not build up and with the nose too low porpoising will occur. Because
of the risk to the nose wheel doors porpoising must be countered immediately (see above).
Once established on the step there will be good rudder and aileron control to keep the
wings level and the track straight. If yaw develops the wings are probably not level so
check the horizon, float position and AH (Artificial Horizon) and correct as necessary.
Speed will build up rapidly at the correct trim angle and at 55-60 knots PBY will come off
the water. At high weights, a higher speed may be necessary before this will occur. Gentle
elevator back pressure usually ensures a smooth breaking free of the water. At the
weights PBY is flown it is safe to assume that at 55 knots she can be pulled off the water
(for example to clear a log or obstacle). She may not stay airborne without a bounce or two
but the obstacle can be cleared.
As the aircraft comes off the water there is a tendency for the nose to pitch up fractionally
due to the loss of drag from the hull. The pilots should concentrate
on nose attitude and fly level in ground effect until a speed of 95 kts, then change to Climb
attitude and maintain 95 kts.
With 95 knots IAS the nose may be re-trimmed and power reduced to CLB power settings.
Stichting Catalina PH-PBY Rev No: 02
01 April, 2006 Page: 5