Zenair CH 601 Zodiac handling notes
1.
These notes are based on the
handling qualities of a Zenair
CH 601 fitted with a Continental
C 90 engine and a Warp Drive, 3
Bladed, 64 inch diameter
propellers. The aircraft was
fitted with a tricycle
undercarriage. The notes are
supplementary to those published
by the kit manufacturer, which
include comprehensive engine and
airframe limitations, and should
be read in conjunction with
them. They aim to cover in more
detail than the kit manufacturer
the flying qualities of the
aircraft, and to deal with
handling characteristics which
are either not mentioned in the
kit manufacturers notes, or are
not dealt with in the depth
needed for coaching on the type.
The aircraft used for assessment
was originally fitted with the
standard tailplane but this was
increased in area after negative
longitudinal stability was
revealed by flight tests. The
aircraft was also originally
fitted with ailerons hinged to
bending metal sheet but this
method was changed to
conventional hinging in view of
the high lateral stick forces
accompanying the kit supplied
aileron fittings.
2. The side-by-side seating is
comfortable with plenty of
space, and all switches and
controls can be reached easily
from either seat. Seat height
and fore and aft adjustment are
not fitted. The all round view
from the cockpit is excellent.
Once the canopy is locked down
there is little or no
ventilation. Consequently the
canopy mists up in high humidity
while taxiing, and strong solar
heating rapidly makes the
cockpit environment extremely
hot.
With two people on board it is
possible for the canopy to be
held partially open while
taxiing to keep the temperature
within tolerable limits in hot
conditions, and to reduce
internal misting.
3. Differential wheel brakes,
the steerable nose wheel, and
the excellent view from the
cockpit make taxiing easy and
safe. The wheel brakes are most
effective.
4. The aircraft tends to swing
gently to the left on take off
but this can easily be
controlled as there is ample
rudder power. Immediately after
unstick the nose should be
raised well above the horizon in
order to maintain a climbing
speed of 65 mph. Considerable
right rudder is required in the
climb to maintain balanced
flight. Immediately after take
off it becomes evident that the
controls are not particularly
well harmonised. The ailerons
are heavy, the elevator is
light, and the rudder is about
right. However, this less than
ideal harmonisation does not
amount to a serious handling
deficiency.
5. When fitted with the kit
standard sized tailplane the
Zodiac is unstable in pitch,
both stick free and stick fixed,
above about 95 mph. The
longitudinal instability is
particularly noticeable as IAS
is increased, and at the cleared
IAS limit of 150 mph it is most
marked. When fitted with a
tailplane of increased volume
the aircraft is just
longitudinally stable stick free
at 150 mph IAS, and as IAS is
decreased pitch stability
returns to reasonable values.
6. The standard kit build calls
for the ailerons to be hinged on
thin flexible sheet metal. This
aileron hinging method results
in very high lateral stick
forces, and apart from the
handling discomfort this causes,
particularly when flying in
turbulence, the rate of roll is
restricted unless the pilot is
overly strong.
With conventional hinges fitted
to the ailerons the lateral
stick forces are reduced
significantly, and the rates of
roll are restored to sensible
values which are achievable with
reasonable applied force.
When side slipping, aileron
power is reduced and this makes
it almost impossible to achieve
useable side slip angles to the
right (left rudder and right
wing down), and quite difficult
to side slip at significant
angles to the left.
7. The all-flying rudder
provides good directional
control on take off and landing
and there is no difficulty in
maintaining balanced flight in
straight and turning flight
throughout the normal speed
range. However, over-balance can
occur at large rudder angles and
there is a noticeable lightening
of rudder forces as this
condition is approached.
8. In straight and turning
flight the stall is generally
benign, with adequate warning
buffet and some audible metal
wing skin panting as the stall
is approached. With power at
idle the stall speed is around
44 mph. As can be expected the
right wing drops gently when
stalling in straight flight with
around 75% power - at this power
setting the stall speed is 40
mph. In an accelerated right
turn at high power the right
wing can be made to drop sharply
if the aircraft is pulled
through the warning buffet.
9. On the approach to land, at
the comfortable approach speed
of 60 mph, the Zodiac flies with
a high nose up attitude which
obscures the runway threshold in
the final stages. The approach
angle is rather flat. If the
speed is too high at the
threshold the aircraft will
float a long way. However, the
Zodiac is not difficult to land
accurately and no special
techniques are required.
From a handling viewpoint a
sensible cross wind limit for
landing would be 12 knots.
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