sport & experimental aircraft

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Cub Comparison
Clipped Cub
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Zenair CH 601 Zodiac
Zivko Edge 540


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.

Cockpit - General Layout and Environment

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.

Take Off and Climb

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.

Longitudinal Stability

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.

Lateral Control

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.

Directional Control

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.

Approach and Landing

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.