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FEATURE
Above: Mucha in original colour scheme as delivered to Lausanne in 1959
Below: BGA5176 with canopy open
off the ground, and to balance the Mucha
to run on its single wheel. Time to
1,000 metres (3,280ft.) AGL behind the
Auster “Tugmaster” with only pilot in
the tug was 7½ minutes.
The Mucha has exceptionally pleasant
and well-harmonized controls. The general
feel is similar to, but better than an
Olympia, and the ailerons, in particular,
are among the best so far encountered in
any sailplane. There is, nevertheless,
sufficient aileron drag to call for rudder
when rolling rapidly into, or out of
turns.
The Mucha is unstable laterally, and if
left to its own devices in a turn, the turn
will steepen, and gradually turn into a
dive. As, however, the airbrakes may be
opened at any speed up to the maximum
permitted for the aircraft, and when
opened, will restrain the Mucha to within
this limit, the aircraft can take care of
itself under most conditions.
The Mucha can be trimmed to fly
level, hands off at any speed within the
normal operating range; if disturbed, it
will oscillate fore and aft. For example,
after trimming to fly hands off at
80km./hr (43 knots) a disturbance produced
an oscillation in which the speed
varied between 76 (41kts) and 84 km./hr.
(45kts), but which slowly dampened out;
the lower the speed at which the aircraft
is trimmed to fly, the longer the dampening
out takes. Opening the airbrakes
stopped the oscillation at once, and the
Mucha settled quickly each time into a
steady glide close to the speed at which it
was originally trimmed, although of
course steeper. Rate of descent in still
air, with airbrakes fully opened at 80
km./hr. (43 knots) was about 4.5
metres/sec. (14.7 ft./sec.), representing a
glide angle near a one-in-four, which is a
satisfactory steep approach for landing in
fields over obstacles.
Directionally the Mucha is stable and
the rudder, though never heavy, is powerful
and effective down to all speeds,
including below the stall.
Stalling the Mucha is interesting, and
special attention was paid to it. The first
indication of the approaching stall
occurred at 54km./hr. I.A.S. (29.1 knots)
in the form of a faint rumble, which
could be both heard and felt, and appeared
to come from somewhere down by the
tail. This cause is possibly the initial
breakdown of airflow over the centre-section,
so that there is a small amount of
turbulence over the tail unit; the effect is
much less than the usual pre-stall buffet.
At 52km./hr. (28 knots), the aircraft
begins to feel as though it were balanced
on a knife-edge, and it is difficult to hold
it level with ailerons alone; at
50/51km./hr. (27Knots) I.A.S. the aircraft
cannot be held level, and one or
other wing drops at this point: a spin
will develop unless prevented.
In level flight, with airbrakes closed,
the point of stall could be reached before
the stick was fully back. Further rearward
movement of the stick at this point
accentuated the wing drop; but at no time
was a spin inevitable, and the Mucha
responded immediately to the appropriate
recovery action. Little height need be
lost, and in fact a series of three full
stalls and recoveries, together with turns
between each to look around the sky,
resulted in a total loss of height of only
150 metres (490 ft.).
With airbrakes open, the stalling characteristics
are not noticeably different.
The sequence starts at 2km./hr. higher
speed, and a slightly greater rearward
pressure and movement is needed on the
control column to bring the aircraft to
the stall, but that is all.
As this pilot with parachute weighs
220lb, (98kg) the Mucha was flying
close to its maximum all-up weight of
718 lb. (326kg) for these tests, and the
c.g. would be near its forward position.
Nothing was found in the stalling
characteristics of the Mucha in this test
which could be beyond the competence
of a properly trained pilot, for it must be
assumed that such pilots have been adequately
trained in spin recovery. If this is
so, the Mucha can be considered an
excellent club and training aircraft, for it
will encourage pilots to fly with understanding
and skill, and it will provide
valuable experience, which is beyond the
capacity of the completely foolproof aircraft.
It is very likely with this idea in
mind that the Mucha has been adopted by
Polish clubs.
In the circuit the Mucha is particularly
easy to handle. The powerful airbrakes
VGC News No. 123 Spring 2008 43