FLIGHT TEST

Perhaps it was in the Project News column of LA magazine, or maybe a report from Oshkosh, when I first became aware of the image of an RV-3… and it immediately grabbed my enthusiastic attention. I thought it looked just right, sleek and purposeful, its tailwheel configuration giving it an energetic, ready-to-go, nose-in-the-air stance. The bubble canopy, coupled with a well-cowled drag reducing frontal area, the pilot sitting centrally being able to be totally connected with the machine. The figures promised real performance, ‘total performance’ was the concept that designer Richard VanGrunsven was aiming for, not just straight-line speed, but good short field ability, rate of climb and precision of handling. And by the praise of those fortunate enough to have sat in the cockpit and taken a ’3 aloft, he had succeeded. But, not everybody wants to fly a single-seater, many wish to share their flying experiences and what became the development of the ’3, the tandem two-seat RV-4, was almost as fast, and had almost as good short field performance, whilst maintaining those lovely handling qualities. The RV-4 is now an established icon and according to Google, is the fourth most popular kit-built aircraft ever conceived with 1,400 produced up to its 40th anniversary last August, from way back in 1979.

The start of the legend

Turning the clock back, how did this all start? The ’1, the first model retrospectively categorised and termed an RV-1, wasn’t really such at all. The subject aircraft was a modified and improved version of a 1952 design, the plans-built SA-3A Stits Playboy. A steel tube and wooden wing aircraft, the wings were oddly strutted from the top of the fuselage sides down to the low wings. VanGrunsven replaced this arrangement with a new aluminium cantilever wing, which included flaps that gave the aircraft a reduced stalling speed of 50mph. It also gained drag reducing upward sloping Hoener wing tips, a field of view enhancing bubble canopy, a streamlined cowling, wheel pants, modified tail surfaces – and an increase from 65hp to 125hp as the C65 was replaced with a Lycoming O-290G. No doubt this, albeit quite extreme modification of an existing design, was the stepping stone to VanGrunsven’s all new RV-3 which, at the 1972 EAA Oshkosh Convention, was awarded the Best Aerodynamic Detailing award. It is still quite evident, nearly 50 years later, why the hugely impressive series of RV aircraft still bathes in so much enthusiastic support – performance sells.

Our subject aircraft

Our subject RV-4 carries an upper dark blue fuselage over a greyed silver paint scheme, and its contrasting red registration is succinctly the marque identity and its registration, G-RVIV. It is fitted with a fuel-injected 160hp Lycoming’s O-320-D3G and an Aymar Dymuth fixed pitch

prop. Aymar Demuth was a US maker of wood and composite props for homebuilts but ceased trading in 2012 following the death of founder Mike Demuth. The RV-4 is known to be able to cruise close to Vne, which is 209mph/182kt and this example also moves with great rapidity. At a climb speed of 103mph/90kt, the VSI will indicate 1,500ft per min at max all up weight.

Planning our sortie

Before considering strapping in and starting, a little thought has to be given to the regime in which we are intending to fly. Should we wish to tootle around the sky, or fly from A to B, then the standard max all up weight (1,500lb/680kg) can be used, so long as we are within the centre of gravity limits of 68.7-77.4in aft of the datum. However, should we wish to pull up to +6G, then our all up weight must be below 1,375lb (623.5kg). Very briefly, kitted and clothed and sitting in the rear seat, I weigh 11stone 11lb (165lb) and I will size Steve as a fit XXL for tee shirts at 12stone 2lb (77kg), leaving us with an aircraft and crew combined weight of 1,006lb plus our 335lb, making 1,341lb. That allowed us a fuel load of 34lb, and at 7.2lb an imperial gallon that is only 4.72 gallons – or to make it sound better, 21.4 litres.

That seemed a bit tight, so our considered plan for this flight would be to start with 45 litres of fuel, sufficient for the stream departure following the photoship, and then flying beside them for the photoshoot for up to 40 minutes burning 20 litres at a reduced cruising speed. At this point of the game, we should be within the aeros weight category to enjoy ourselves further, looking at India Victor in a variety of attitudes and manoeuvres, but not too far from the airfield.

Compact and bijou

The design advantage of an efficient, lightweight tandem aircraft is not for all. Its configuration and dimensions may be overshadowed by the potentially larger sized pilots who may view the cockpit as rather restrictive, not allowing easy access or comfort when settled and strapped in. Ensuring one has clean shoes, from the left walkway, aided by it not having a steeply raked attitude and with the canopy swung to the right, entry is an easy matter of standing on the rear and supporting myself with the roll bar, lowering myself down as I slide my booted feet either side of the front seat. Stepping into the front cockpit, the roll bar is a good hand hold, but when lowering oneself down, grabbing the cockpit edges is a great help.

A Spartan rear

There are no instruments in the rear cockpit, all is cut to the bare minimum. There is a mount for a portable Garmin 196 on the rear of the front seat, but I thought I could see all of the panel by craning my head around Steve’s bonce. There is a stick, and its throw is not hindered or restricted by any items in either cockpit, and my rudder pedals are unusual in that they are rods that protrude from the front footwell which have chunky, metal circular discs for the balls of the feet to ease against. I also had a left side, wall-mounted throttle, and my stick has a coolie hat electric trim switch, and electric flap switch – the settings for take-off and approach can be judged visually by their angle against the inboard edge of the ailerons beyond (the sole trim indicator is mounted on the front panel), but otherwise that is all I have to contend with.

Ordinarily this is not a training machine and so items of operational necessity, such as fuel taps, radios etc are just not needed to be within reach for the rear seat ‘passenger’. Having said that, I did teach a fellow for his PPL in his own RV-4 quite some years ago, and he had to fit a rear throttle for me. It was an aesthetically and practical solution, having a polished and petite Edwardian brass door knob. I am 6ft 1in and have a slightly long back, measuring 36 1/4in from my seat to crown which has, unfortunately, precluded me from flying and closing the canopies of a Cri Cri (I have to admit I nearly cried) and a Monnet Moni (upon which I certainly moaned) – it would seem therefore that size matters… According to Van’s and Co., the rear seat has 39in from seat to canopy, which with a peaked ‘jeep’ cap and headset on I still had a flat-handed palm of head clearance – and I could still sidle from side to side to see very nearly ahead, as the rear cockpit is 25in wide, increasing to 28in beyond the roll bar as the fluted fuselage widens heading forward. This welcome expansion extends the front seat headroom to a comfortable 40in. There is a 7.3 cubic feet locker directly behind the rear seat, at the moment it is empty but can carry up to 50lb.

Fuel

Notable of the front cockpit controls are the internal roll trim springs on either side of the control column’s shaft. There is an adjuster to remove any fuel imbalance and Steve says it doesn’t need much counter movement to remove any potentially, but slightly annoying, roll bias. He tends to avoid any ‘real’ fuel imbalance that might produce this trait by changing tanks on a regular 15-minute cycle. The wing tanks have a combined capacity of 121 litres and the Andair rotary selector is centrally placed, on the floor just forward of the stick with the left and right circular content gauges just beyond. The electric fuel pump switch is mounted just below three horizontal ‘traffic light’ warning lights on the lower left side of the panel – green indicating pump on, red for fuel pump off and orange for flaps down.

At an rpm setting of 2,300 and a cruise of 140kt/161mph, flow is expected within the region of 23 to 25 litres an hour. So, even over-egging the pudding by saying we’ll use a litre of avgas every two minutes, we have four hours to travel in as straight a navigated line as possible. In a calm and soothing sky, free from oppressive headwinds and seated on a comfortably firm cushion, and having avoided any coffee beforehand, it would give a range of 560 nautical, or 627.2 statute miles. Long legs indeed! Controlling the fuel is a throttle and mixture quadrant mounted on the left fuselage side. There is no carb heat as ’IV has a fuel-injected engine.

Our camera ship today is Patrick Caruth’s Freelance (flight test December 2013) and if I remember he cruises at 105kt, which will give us plenty of performance for positioning ability and a reduced fuel burn as well.

Gyros, gauges and comms

There is but one gyroscopic driven instrument, the artificial horizon, and its tiny ‘sixpenny-sized’ suction gauge (which I bet few of us ever check) it’s sitting on its own, outside right. We have a neat mixture of steam, digital and warning lights in front of us on a smart light grey panel. Their functions are readily obvious once individually scanned but it is worth spending more than a glance as to where things sit. There is a mixture of representations for solo and associated group displays. I do like the circular RPM dial with an outward semi-circle of tiny green lights that light progressively further around the dial as the revs increase from 1,200 to 2,700rpm and to complement this representation inset there is a digital readout as well. To its right is a manifold pressure gauge, it’s needle correctly stuck at two o’clock showing us our high static ambient pressure of just over 30in. We have every engine parameter covered with back up warning lights.

A Becker 8:33 radio and transponder are positioned low and left on panel and nav is taken care of by an iPad with Runway HD and a backup Airbox Clarity.

Ready for the off…

The throttle knob, spherical in shape, fits comfortably into the crook of the left palm. It was once black but it’s paint has all but been worn away with use, exposing its wooden form. It moves freely through its full arc and, set a tad more than quarter of an inch open, and mixture fully back and closed, master on, fuel pump on and we hear the tick, tick, tick of pressured fuel to prime. Clear all around, ‘Clear prop!’. Left mag on, engage the starter and as the Lycoming fires and the prop blurs, the mixture is slid forward and the right mag is brought into the game. Alternator on, and the oil pressure rises to 55-60psi. Having warmed up, the fuel flow has been established on one tank and Steve changes to the other as we taxi to the hold for the run up. Into wind at 1,800rpm, mag check complete, idle is a sweet ‘chunk atta chunk’ with no undue roughness. The standard mantra is addressed and, at ‘flaps set’ a switch marked RSE situated under the flap and pump ‘traffic’ lights , is switched to ‘On’ – RSE stands for rear stick enabled – thus allowing or otherwise the rear seat occupant to operate the coolie hat flap, trim and PTT. My view is manageable providing I sweep the nose, don’t rush and anticipate any swing, all tempered by the fact that I have no brakes.

Take-off and climb

Having lined up, throttle closed, I give her back to Steve for the take-off. We have 2,200rpm static accompanied by the open exhausts, that eager prop slicing the air; rolling, the tail Previous page The Van’s has the speed to go long haul, the agility to stooge and play, and the strength to perform aerobatics – what else could you possibly want!

Top She rolls around the sky with such ease

Above The RV-4 is a very compact aircraft, easily manoeuvred by a single person but better with two in the confines of a hangar. held down, keeping straight with right rudder and stick still in neutral, I am ghosting the stick and foot work. Directional control is helped by having all three points on the runway rather than forcing the tail up too early, but at around 150 metres the tailwheel is slowly edging itself up and easing the nose down, allowing us to see more ahead. Rudder and direction still have the centreline, the engine and prop are singing away with an eagerness to fly. At perhaps 250 metres we sit in a near perfect ‘fly herself off attitude’ and, with the ASI passing 65kt she is being held in ground-effect and the speed allowed to rise to 90kt as the climb attitude is selected and trimmed. This all took place in under perhaps 400m. Passing 300ft and flaps up, slight nose attitude adjustment and blip on the stick’s electric coolie hat trim, we ascend to look for our partners in crime orbiting the Freelance in the sunshine. They are somewhere to the south before the 1,200-foot mast on the hills at Bulbarrow and over the villages and hedged, green fields of the Blackmore Vale.

Control is all

As with all machines and especially aircraft, control is all. So, being able to anticipate a change rather than reacting to an event, implies the finesse of control. It was present here today and I wondered what this fellow up front had cut his teeth on? As you can read in this month’s Meet the Members column, Steve started out on gliders and went

the Silver C route to powered flight, now sadly no longer possible. After a VP1 and a Condor, the RV came into Steve’s life. “How was your speed handling and check out on the RV?” I asked. “Ah well,” there was a slight pause and a head rocking chuckle, “double awesome burger with large fries! First take-off I was so awe struck, I was two miles out of the circuit passing 2,000ft before I remembered the flaps! But time in the cruise and a friendly back-seater taught me to anticipate the distance needed to slow down for a return to the circuit, and the white arc on the air speed for the 90kt flap limiting speed!”

A good pair of eyes from the front seat spots the Freelance and the RV closes. Within perhaps half a mile Steve gives me control and I prepare to join the echelon left as arranged. The trick is to reduce the power promptly as the lead aircraft appears to ‘bloom’ (to suddenly grow rapidly in size). But we are ganging along with a 50kt speed differential… and, like all of her family, ’IV is particularly aerodynamically clean. Anticipation, coupled with caution, ensured our ‘steed’ is given reduced power early and we stabilise, rise into the lateral position and sidle in on a diagonal alignment. Steve confirms that all of the engine parameters are in the green and continues his scan for other aircraft. I can see too, Patrick concentrating and looking ahead, not being distracted by the aircraft tucked in tight under his wing. We danced hither and thither to Neil’s command as he got his shots, the RV doing all we asked of her with consummate ease.

Stalls and stability

Photos complete, we were free to beetle back to Henstridge and do some general handling en route. Unfortunately, it seemed like the weather in the west was worsening, and Steve had to refuel and get back home with a reasonable margin before a winter’s afternoon darkened. Very quickly, after assuring ourselves we were in balance and were trimmed out perfectly hands off, first with flaps up and then in the Top left Flying along the South Coast, full tanks would get you well into mainland Europe.

Below left The aircraft is flown from the front seat, and ‘IV has a nicely appointed cockpit and panel. It’s an ergonomic dream..

Below The right side-hinged canopy and shallow sloped wingwalk make climbing in or out a relatively simple task. approach mode, I confirmed by releasing individual cross controls that she was stable laterally and directionally. We were of course still well within the C of G limits and the up down phugoids, those rising and falling hands off cycles, dissipated to assure us she was also stable in pitch. Clean stalls from straight and level exhibited no wing drop and are pre-warned both aerodynamically with a juddering elevator and stick, and a clearly audible buzzing warner prior to the start of sink and eventual stall at 52kt. Full flaps and no power showed a similar action at 48kt, but there was more waffle before we were let go, with a slight hint of instability and a right wing drop. Stalls from in balance climbing turns both left and right had her rolling progressively to wings level and, as she did so, all we had to do (as in ALL erect stalls) was to ease the stick forward to reattach the airflow for control response. When considering the speed range of the RV-4 from 48kt/55.2mph to a Vne of 182kt/207mph, there are few homebuilt or light general aviation machines for that matter, that have a 1: 3 airframe speed range. Quite remarkable. And very remarkable to achieve a cruise of 140kt/161mph at 2,400rpm burning 25 litres /5.5 imp’ gallons an hour and Steve has seen 175kt straight and level with both levers forward before reaching the engine red line speed of 2,700rpm. Lightly loaded, she’ll show 2,000ft a minute ascent!

Time to play

I started to clear the area for some aeros and then, after a brief discussion that perhaps we hadn’t burnt as much fuel as we anticipated and might only be on the edge of the aerobatic weight limit, we decided we had better stick to 4G. Entry speed for most aerobatic manoeuvres is 130-140kt. “I tell you what, let’s just do a couple of gentle rolls and fly together when the weather decides to change its

Above Silhouetted against a setting sun and a cirrus cloudscape, this is just magical.

Left The Van’s tailwheel looks quite rudimentary when compared with traditional units, but it certainly fulfils the job.

Below The Van’s series are something of an enigma – they are ostensibly an unsophisticated design yet perform quite magnificently. A convincing argument for less is more. mood.” So… a big, sweeping, balanced barrel roll, using pitch and roll at the seemingly correct rates with energy upwards to check, the inverted point confirming the roll rate was correct and continuing in low g to take us all the way around. Nice and smooth, what a lovely girl. Steve showed an aileron roll and she twirls beautifully.

She will roll 360° from cruise, with just short of full deflection beneath the Vno of 156kt IAS/179.4mph at just over three seconds. Pushed slightly further but starting with a higher nose attitude and same speed, again to the favourable right, she will roll twice before wings level and a lower nose attitude. However, I did have to increase the rate of roll with pro rudder for the last 90°. I have no doubt that she would come around cleanly without being forced should we start with a higher speed and power. Simply delightful.

Back in the circuit

Breaking off, Steve joined on a short left base for 24 with a constant curve at 70kt/80.5mph and partial flap, becoming 65kt/74.75mph with full flap. The last over the hedge speed I saw was 60kt/ 69mph before he held to float, maintaining the nose attitude above the horizon with stick not quite fully back for us to squeak on with all three wheels together. Nicely done. Well, we still have an aeroplane and Steve managed to get home before anybody could be concerned by the early onset of any darkening clouds. I think Neil was more than happy with his end, Patrick too. So, although we ended up beating a retreat for an early home visit, but to finish on a bit of misquoted doggerel: ‘He who has flown and flies away, can fly again another day’. Cheers Steve, great machine. But I'd like you to arrange some good early spring weather so we can aerobat a bit more, please… ■

VAN’S RV4

Specs with O-360 180hp engine

General characteristics

Length: 20ft 4in (6.20m) Wingspan: 23ft (7.0m) Height: 5ft 5in (1.65m) Wing area: 110sq ft (10m2) Empty weight: 903lb (410kg) minimum Gross weight: 1,500lb (680kg) Fuel capacity: 32 US gallons (120L; 27 imp gal) Powerplant: 1 × Lycoming O-320/O-360, 150-180hp Propeller: Two-bladed fixed pitch or constant speed propeller Performance

Maximum speed: 212mph (341km/h, 184kn) Cruise speed: 200mph (320km/h, 170kn) 75% power at 8,000ft Stall speed: 54mph (87km/h, 47kn) Range: 590mi (950km, 510nm) Service ceiling: 23,000ft (7,000m) Rate of climb: 1,950ft/min (9.9m/s) Wing loading: 13.64lb/sq ft (66.6 kg/m2) Power/mass: 8.33lb/hp