Pipistrel Sinus 503, Flight And Maintenance Manual

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Appendix
Descent
Descending with Sinus ultralight motorglider is the stage of flight where perhaps most care must be
taken. As the aircraft is essencially a glider, it is very slippery and builds up speed very fast.
Start the descent by reducing throttle and setting propeller pitch back to flat (screw propeller
pitch knob fully to the left). Do not, under any circumstances, increase speed or use airbrakes to
descend at high speeds.
If you have cruised at 200 km/h
(105 kts)
this is your top descent speed. During initial descent
I would recommend you trim for a 30 km/h
(15 kts)
lower speed than the one you decided to descent
at. Do this for safety. In case you hit turbulence simply release forward pressure on the stick and the
aircraft will slow down.
Also, keep in mind you need to begin your descent quite some time before destination. A com-
fortable rate of descent is some 2,5 m/s
(500 fpm)
. So it takes you some 2 minutes for a 300 meter
(1000 feet)
drop. At 200 km/h
(105 kts)
this means 6,7 km (3,6 NM) for each 300 meter
(1000 feet drop)
.
Entering the traffic pattern the aircraft must be slowed down. In order to do this, hold your alti-
tude and reduce throttle to idle. When going below 150 km/h
(80 kts)
, set flaps to neutral position.
Set proper engine RPM to maintain speed of some 130 km/h
(70 kts)
. Trim the aircraft for comfortable
stick forces.
Just before turning to base-leg, reduce power to idle and set flaps to 1
st
stage. Once out of the
turn, reduce speed towards 90 km/h
(50 kts)
. Power remains idle from the point of turning base all
the way to touch-down. If you plan your approach this way, you will always be on the safe side - even
if your engine fails, you will still be able to safely reach the runway!
Turn to final at 90 km/h
(50 kts)
. When in runway heading, set flaps to 2
nd
stage. Operate the air-
brakes to obtain the desired descent path.
How to determine how much airbrakes you need for a certain angle of attack?
Open them half-way and observe the runway. If the runway treshold is moving up, you are dropping
too fast - retract the airbrakes a little. If the runway treshold is disappearing below your aircraft, you
are dropping too slowly - extend airbrakes further. When working on airbrakes, it is important to
keep the angle of attack constant thoughout final all the way to flare! The airbrakes will not im-
pact your speed, just rate (angle) of descent. For pilots who are not used to operate airbrakes but
throttle instead, let me tell you that airbrakes in Sinus ultralight motorglider work just like throttle
does: handle back equals less throttle, handle forward equals more throttle.
CAUTION!
Never drop the spoilers’ (airbrakes’) handle when using them, keep holding the
handle even if you are not moving it!
Roundout (Flare) and touchdown
Your speed should be a constant 90 km/h
(50 kts)
throughout the final with the descent path con-
stant as well. At a height of 10 meters
(25 feet)
, extend the spoilers (airbrakes) fully and hold them
there until the aircraft comes to a complete standstill. The flare must be gentle and the aircraft must
touch down with all three wheels at the same time.
Only so you will not bounce from the runway.
After touchdown, operate the rudder pedals if necessary to maintain runway heading. While brak-
ing, hold the stick back fully!
Once you have come to a standstill, retract flaps all the way to nega-
tive position (handle full down) and rectract and lock the spoilers (airbrakes) - handle full up.