1. These handling notes are based upon a flight test program carried out on an imported RV4 aircraft G-FTUO fitted with a Lycoming 0-360 fuel injected 180HP engine. The aircraft was built to the standard RV4 specification to a high degree of manufacturing accuracy. The advice here is based upon a subjective assessment of the aircraft flown and should be read in conjunction with the kit manufacturer's notes. The pitot/static system was believed to be over-reading slightly, which may account for slightly higher values for stall speeds and approach speeds throughout. Engine handling requirements have not been discussed thoroughly, as these will depend upon the type of engine installation.

Cockpit

2. The RV4 cockpit is adequately sized for the average build, although it would be a tight fit for the more portly gentlemen amongst us. Despite being sat well down into the seat with a seat cushion of perhaps 2 inches thickness I found that there was not a great deal of canopy clearance (about 2 inches for a 5ft 11" pilot). The cockpit is vented from punka louvres under the instrument panel and this provides sufficient air to keep the forward part of the bubble canopy from misting badly during cold weather with two on board. However, they are insufficient to prevent canopy misting around the rear occupant. This has been solved with some owners using NACA ducts, let into the lower rear canopy fairing, to provide additional ventilation. Some aircraft are also modified with a canopy support strut for taxiing with the canopy open a couple of inches. The canopy locking mechanism is sound.

The rear seat is somewhat cramped with most RV4s not being fitted with rudder pedals in the rear cockpit and the potential for some interference between the occupant's left leg and the Flap Lever. Although the fitting of electrically operated flaps is often included, the standard mechanical arrangement is less than ideal. The flap lever, situated just underneath the pilot's left thigh, has narrow detents for the mid/full flap positions.

This is precisely where the rear occupants left leg/foot is normally situated. Limited flying was carried out with the rear passenger in situ, although it is recommended to ask the rear passenger to move his left leg rearwards prior to and during operation of the flap lever. Although with air loads, the flaps would not accidentally lower in flight, the lever did have a tendency to jump out of the narrow gate for the Up position whilst on the ground, thus lowering flaps to the mid position.

Throttle/Mixture Levers were mounted next to one another in a quadrant type arrangement. This aircraft was modified with a mixture lever balk to prevent inadvertent mixture cut-off during throttle movement and aerobatics. The fuel cock for both L and R Wing Tanks was easily identifiable and readily accessible mounted on the floor between the pilot's legs.

Elevator trim was operated by a lever mounted forward of the throttle on the fuselage wall. This control was both easy to reach and operate during flight.

Taxying

3. Taxying presented no difficulties with good visibility over the nose of the aircraft and both a steerable tailwheel and differential toe-braking available. Weaving the aircraft during taxi was not necessary. Spats were fitted and care must be taken when taxiing over unprepared or rutted surfaces to avoid damage. There was no parking brake.

Take-Off can be performed with the flaps Up or at the Mid position as necessary.

Take Off and Climb

4. The aircraft performs very well with 180 HP, the large rudder providing ample directional control for take-off in significant cross winds. In still air, there is a little directional swing as the tail rises. However, compensation required is minimal and the aircraft rapidly gets airborne and accelerates to climbing speed. A 110mph climb at 2350rpm produced 2000ft/min rate of climb. Flap is not required for Take-Off unless a particularly short Take-Off run is required. In this case the Mid position may be used, bearing in mind that the aircraft accelerates rapidly to the flap limiting speed of 100mph. Trim was set just forward of neutral and lift off occurred around 70mph.

Longitudinal Stability

5. Longitudinal Stability was satisfactory including a very positive stick force/g relationship providing plenty of protection against exceeding g limitations. This was more than adequate for aerobatics taking into account the strong airframe design. High positive static stability in the cruise leads to relatively high control forces in pitch compared to the ailerons, which remain crisp and light throughout the flight envelope. Despite this slight heaviness in pitch, the general harmonisation of the controls is satisfactory and suitable for an aircraft of this type.

Lateral/Directional Stability

6. Strong directional stability and adequate dihedral effect provides for a linear aileron/rudder relationship for sideslip angles up to full rudder deflection both with and without flap. Sideslip can be used comfortably on the final approach, with significant effect on approach angle and no pitot/static interference. Control is positive at all times with the large rudder and presents no problem in kicking off drift for de-crabbing following sideslip or during cross wind landing.

Dutch roll is well damped and the aircraft has a neutrally stable spiral mode.

Stalling

7. The clean stall is uneventful with little to no wing drop and aileron control effective down to the stall at 63mph. About 5-7kts of light stall warning buffet is present with a significantly high nose attitude from a l kt/s deceleration in level flight. Dynamic entries and turning entries would not induce a wing drop unless sideslip was deliberately introduced. Unsurprisingly, stalling with flap at 58mph produced a consistent wing drop (to the left). However, recovery was swift, if applied immediately, with no tendency to accelerate too rapidly to flap limiting speed.

Aerobatics

8. All looping manoeuvres were initiated from 170mph and using a smooth 3.5g entry. This speed was also satisfactory for the roll off the top manoeuvre, with minimal adverse yaw producing a comfortable rolling manoeuvre at low speed.

Barrel Rolls and Slow Rolls were comfortably initiated at 160mph.

Stall turns were commenced with a pull up from 170 mph. For the LH stall turn, rudder could be delayed significantly, the effect of the prop wash help to provide sufficient turning moment. RH stall turns, however, required the rudder to be fed in at around 75mph to ensure that the aircraft would turn cleanly.

Caution:

With the fixed pitch prop as fitted to this aircraft, care must be taken not to overspeed the engine. This is particularly easy to do since the aircraft is very clean and accelerates quickly in a dive. A Vne run was carried out at 1/3 throttle position and the rpm approached the limiting value of 2700rpm at the Vne of 210mph. Engine overspeeding will occur if care is not taken during manouevring.

Spinning

9. The aircraft will not auto-rotate unless forced to do so by deliberate pro-spin application of controls. Initiation of significant sideslip near the stall will initiate auto-rotation with a full erect spin developing should pro-spin controls be held. Spins in both directions exhibit similar characteristics with rotation rate steadily increasing and attitude flattening slightly with an increasing no. of turns. Erect spins were limited to 3 turns in both directions with the throttle at idle.

Recovery was prompt in all cases (within 1/2 turn), with opposite rudder applied and steadily and centrally moving the stick forward until the rotation stopped. Recovery was also effective by centering all controls, although recovery was delayed further by 1/2 turn.

Approach and Landing

10. 80mph appeared a suitable approach speed although Vans recommended 75 mph. Although 75 mph provided a satisfactory margin from the stall, the increase in drag, particularly from the prop, on reducing power in the flare generally produced a more positive landing.

With the sprung undercarriage design, this produced a tendency to oscillate up and down on the gear assembly and did not feel as comfortable as the more controlled flare and deceleration from 80mph.

Deceleration through the flare was such that this increase in approach speed did not appear to have a marked effect on landing roll out. The aircraft is straightforward to 3 point with no directional difficulties throughout the landing roll.

The go-around requires only a pound or so of forward stick force to compensate for full power and acceleration into the climb, with no tendency to rapidly accelerate through the flap limiting speed.

During glide approaches 85mph worked well as an initial glide speed both clean and with flap, aiming for 80 mph coming into the flare. Any slower than 8Omph produces a significant drag rise in the approach configuration and consequent increased rate of descent.

Conclusion