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Flight Test: Ryan ST-A – The Thirties Sportster

PUBLISHED: 17:01 02 August 2016 | UPDATED: 17:11 02 August 2016

FLIGHT TEST ST-A

FLIGHT TEST ST-A

Darren Harbar (C) SINGLE USE PILOT MAG ONLY

No more eye catching machine ever danced the skies than the lithe and shapely ST-A.

FLIGHT TEST ST-AFLIGHT TEST ST-A

Dancing across a perfect spring sky in a graceful chandelle, sunlight sparkling on the shining silver fuselage, the wail of the wind in the wires merging with the engine’s resolute roar, is pure joy. It is a beautiful day and I’m flying a beautiful aeroplane!

A sleek, stylish study in silver, the Ryan ST-A is undoubtedly one of the most handsome aeroplanes ever made. Even in the dull light inside one of Old Warden’s famed ‘aeroplane sheds’ it gleams and, despite being surrounded by some truly fabulous flying machines from the 1920s and ’30s, still stands out. The casual observer can’t fail to notice why; as well as being absolutely stunning it is−most unusually for a light aircraft of this era−a monocoque design, made mostly of metal. This is probably because production of the ST-A coincided with the introduction of a new type of aluminium alloy known as Alclad, of which more later.

FLIGHT TEST ST-AFLIGHT TEST ST-A

As the hangar doors slide open, spring sunlight streams into the shed and this rare Ryan practically glows in the morning sun. It’s more like a sculpture than an airframe−where Art Deco and Solvol Autosol meet. When I say to owner Peter Holloway that the cheap plastic drip tray under the luminous cowling looks somewhat incongruous he agrees, adding “I really should replace it with a silver champagne bucket”. And do you know what−it wouldn’t look out of place!

Having carefully pushed November ‘Charlie one eight niner two three’ down to the grass parking area (with ex-policeman Peter threateningly reminding us “not to leave any fingerprints, as I’ll know who did it” I study this iconic aircraft more closely.

FLIGHT TEST ST-AFLIGHT TEST ST-A

Shuttleworth’s Chief Pilot ‘Dodge’ Bailey and Chief Engineer Jean-Michel Munn wander over to offer advice, and Dodge also kindly gives me a set of reference cards for my kneeboard. Fully briefed, I return my attention to the aircraft. With its deep but narrow oval fuselage, sturdy wire-braced wings and delicately curved tail the ST-A has a harmony of line that’s rarely been bettered, and in many ways epitomises the 1930s American flying scene more than any other monoplane.

Peter’s aircraft was built in 1939, when it retailed for around $6,000−a lot of money in those days, but then ST-As have never been cheap. (ST stands for Sport Trainer, by the way.) Ryan made some 75 or so, and of these around 22 still exist, most of them retaining their original highly polished natural metal finish. The previously mentioned new aluminium alloy called Alclad was being introduced at about the same time as the Ryan Aeronautical Corporation of San Diego started designing the ST-A and consequently Alclad is used extensively. In fact some of the aerodynamic loads are borne by the skins themselves while, in a notable departure from most 1930s aircraft, it has relatively few stringers, formers and bulkheads. Instead, heavy gauge 24ST Alclad is wrapped around, and then riveted to the formers, enabling the longitudinal loads to be carried by the thick metal skins. The only significant use of steel (apart from the undercarriage) was for the bulkhead that carries the loads from the undercarriage, landing and flying wires, and the engine mounting. The bulkhead is made from steel sheet, while the engine mount is of the cradle type, being a welded assembly of steel tubing bolted to matching steel fittings riveted to the firewall end of the fuselage. The engine sits in this cradle and is secured to it in two places each side of the crankcase via bolts through rubber biscuits. All the steel used is 4130 grade.

FLIGHT TEST ST-AFLIGHT TEST ST-A

I’ve always felt that the ST-A somehow looks more European than most of its American contemporaries, and as I study the sleek cowling I realise why. Unlike most US-built aircraft, it has an inline engine−a configuration that never found much favour in America, with most engine manufacturers of the 1930s preferring either the V, horizontally-opposed or radial cylinder arrangement. The ST-A’s powerplant is a notable exception, being a four-cylinder, aircooled, inverted inline engine built by Menasco Motors of Los Angeles, California. Peter’s ST-A is powered by a Menasco D-4/87 Super Pirate, which produces 134hp at 2,260rpm and turns a Fahlin two-blade, fixed-pitch wooden propeller. The fuel is carried in a single 91 litre tank located between the front cockpit and engine, with quantity indicated by a float. There was a sixty-litre auxiliary fuel tank option, which fitted in the front cockpit once the flight controls were removed. With the auxiliary tank in place, the front cockpit cut-out was faired over with a metal cover which hinged open, allowing the remaining space to be used as an additional baggage area.

The main baggage compartment is behind the front seat, which hinges forward to give access. When Peter’s Miles Magister is parked alongside I note that the Ryan’s engine cooling intake is on the starboard side of the nose bowl, unlike aircraft fitted with British or European inline engines, which tend to have it on the other side. This difference is dictated by the clockwise rotation of the ST-A’s propeller, and ensures that air flows smoothly across the cylinders.

FLIGHT TEST ST-AFLIGHT TEST ST-A

Curiously, although a monocoque fuselage was considered quite futuristic in the mid-1930s, the wire-braced wings are not as advanced, employing an interesting mixture of traditional methods and materials. They consist of a steel tube stub centre section which carries the outer wing panels, the framework of these being made up of spruce spars, steel compression members and stamped aluminium alloy ribs. Although most of each wing panel is covered in fabric, the leading edge is skinned with 24ST Alclad, back to the front spar. The aerofoil is a NACA 2412 section, while the ailerons are a modified Frise type. An advanced feature is that the ST-A is fitted with flaps. As it has a similar MAUW but only half the wing area of contemporary biplanes it obviously has a higher wing loading, which means that it stalls at a significantly higher speed than its peers, necessitating a faster approach speed. To reduce this, large plain flaps are fitted−an innovation for a 1930s trainer. However, although the flaps cover about fifty per cent of the trailing edge and have five different positions they only extend to a maximum of 30 degrees. Dodge observes that they “don’t really do much” and speculates that they might’ve been more of a training aid. The flaps and ailerons consist of tubular aluminium alloy frames and stamped aluminium ribs, covered with fabric. A treadle-type undercarriage made from steel tube carries the main wheels, which are fitted with long-stroke oleo shock absorbers. The wheels and shock absorbers pivot forward of a fixed point attached to the stub centre section, which also anchors the lower flying wires.

The undercarriage struts are fully faired, while the large main wheels feature beautifully-made spats. It was during the 1930s that designers first began to fully appreciate the importance of reducing drag, and consequently the ST-A is carefully streamlined from spinner to sternpost, the whole effect giving the aircraft the appearance of movement even when it is standing still.

FLIGHT TEST ST-AFLIGHT TEST ST-A

The brakes are quite curious. As delivered from the factory they were heel-operated drum brakes actuated by cables, but this aircraft has toe-operated disc brakes. However, they’re not purely hydraulic. Instead, cables connect the pedals to master cylinders in the undercarriage fairings. Jean describes this system as “whacky−but it works!” The pneumatic tailwheel steers through the rudder pedals and also ‘breaks out’ to castor, but the tailwheel lock has been removed. The fin is braced to the tailplane with wires, with a trim tab on both elevators, and the size of the fin is interesting. It’s not very big and, as there’s clearly quite a bit of side area forward of the centre of pressure, I wonder about the directional stability. However, I also note that the rudder is a fair bit bigger than the fin and has the tailcone built into its base, fairings formed from Alclad sheet being attached to each side of the lower part, blending the tapering lines of the fuselage with the bottom of the rudder. The rest of the tail surfaces are fabric covered, and use the same construction materials and methods as the flaps and ailerons. It’s all very well made and of extremely high quality−even the leather trim around the cockpit rim is absolutely flawless.

Getting in is a bit of a squeeze, particularly if−like me−you don’t care to miss meals. Unlike the military Ryans the ST-A’s longerons are internal and, along with the oval-sectioned fuselage, make for a tight fit. Having successfully wiggled into the back seat, the cockpit is certainly snug and, although the stick, throttle and rudder pedals are all easily reached (the seat adjusts), the ancillary controls aren’t as well placarded as they could be. Peter explains that the small silver T-handle sprouting from the panel is for carb heat, the silver lever under the throttle quadrant operates the wobble pump, and the grey handle just forward of the seat sets the parking brake. The throttle quadrant is well sited on the left sidewall and carries throttle, mixture and a third lever, topped with a black knob marked S (for spark). This is the advance/retard control for the ignition timing and is a real asset when hand-swinging the prop. (The aircraft is fitted with a starter motor, but the battery is a little weary.)

FLIGHT TEST ST-AFLIGHT TEST ST-A

Immediately aft of the throttle quadrant are the elevator trimmer and its co-located position indicator. This confused me for a moment as, although you wind the trimmer the way you’d expect−forward for nose down, backward for nose up−the position indicator moves in the opposite direction. By your right knee are the flap lever and fuel selector. Some ST-As have the oil on/off control valve in the cockpit, but this one’s is in the engine bay. A potential ‘gotcha’ with the fuel system is that, with the selector set to on, there’s still about eleven litres sloshing about in the tank when the engine quits through fuel starvation! Although there’s only one tank, the ‘Res’ setting takes fuel from the very bottom, while ‘on’ feeds via a standpipe. Consequently, when taking off and landing, the fuel selector is always set to Res. The flaps are operated by an old style handbrake-like lever mounted on the right, and it’s probably there because it’s the only place it would fit!

The instrument panel layout is curious. There is a large, centrally-mounted compass with the ASI below and to the left, the altimeter is underneath the compass and tachometer to the right, with a combination gauge for the oil temperature, oil pressure and fuel pressure above the rotary magneto switch on the far right of the panel. Instrument anomalies are the single-pointer altimeter−which doesn’t have a Kollsman window but still has a range of 20,000ft−oil temperature being in Centigrade, and that with a maximum reading of 170mph the ASI only covers four mph more than the 166mph Vne (modern ASIs must be suitable to at least 1.05 x Vne).

FLIGHT TEST ST-AFLIGHT TEST ST-A

And as if the altimeter’s single needle isn’t potentially confusing enough, the tachometer has two pointers, the one showing thousands being quite small.

The sole concessions to the 21st century are a small transceiver, transponder and intercom. With everything set, I use the wobble pump to generate some fuel pressure, prime the engine using the throttle and the engine fires third swing. I move the advance/retard control quickly to about halfway and adjust the throttle until the engine is grumbling quietly to itself at 800rpm. The exhaust pipes are straight and stubby, and produce a satisfyingly crisp crackle that changes to an eager bark as soon as the revs are increased.

FLIGHT TEST ST-AFLIGHT TEST ST-A

Unsurprisingly the sight of this gorgeous machine starting up has drawn a small crowd to the fence and I give them a cheery confident wave and slowly taxi out. While strapping in I’d experienced more than a twinge of trepidation−who wouldn’t? However, as is often the case once the engine has barked into life, the eager ruffling of the propwash soon blows away any apprehension and I taxi in a sedate series of S-turns towards Runway 21. Visibility over the nose isn’t great and it is prudent to taxi at only one speed−slowly!

Pre-takeoff checks are pretty straightforward, the only irregularities being to ensure that the ignition control is fully forward to ‘Advance’ and the fuel selector on Res, although I am again confused for a moment by the trim position indicator.

As the ground is still quite soft in places I use the first notch of flap, carefully line up and bring the power in slowly. Today’s ambient conditions aren’t that far off ISA, with an OAT of 14°C, QNH of 1014 and a field elevation of 110ft. Of far more importance is the wind, which the sock shows to be most amenable−about ten knots within ten degrees of runway heading. Keeping straight proves easy, and a slight swing is effortlessly corrected with a dab of right rudder. After a ground roll of just under half the 628m available the Ryan slides into the sky.

FLIGHT TEST ST-AFLIGHT TEST ST-A

Peter’s aircraft has an extra nine horses over a stock ST-A and although the climb rate isn’t bad, it’s not as sparkling as the fuselage. An original 95hp ST can’t have been much fun at MAUW in a San Diego summer! Eighty five mph (75kt) indicated seems about right, and although the view over the nose is quite good the sky round here can be busy, so I weave from side to side in order to see past the long nose and scan for traffic. Even this simple manoeuvre demonstrates quite clearly the type’s crisp handling and well-coordinated controls. However, the slip ball is all over the tube, which is a little disconcerting. (I learned later that it’s almost certainly the wrong type.)

Assessing the rate of climb isn’t easy either. There’s no VSI, thermals are starting to pop and for the single-pointer altimeter to register 1,000ft the needle only travels 1/20th of the way round the dial. Between 700-800fpm is my best guess.The giant airship hangars at Cardington are a very useful landmark for keeping track of my position, so I head over to the west, and at 2,000ft-ish (the altimeter really isn’t that precise) level out and look about, before trying a couple of tight 360 degree turns in both directions. The Ryan marque has always had an enviable reputation for fine handling and the ST-A doesn’t disappoint. Both the ailerons and elevators are authoritative and feel very light and smooth, even though the static friction is quite noticeable on the ground.

FLIGHT TEST ST-AFLIGHT TEST ST-A

I am keen to discover what the handling is like at the slow end of the speed range so, once satisfied that no-one else is around, a clearing turn is swiftly followed by a couple of stalls. These produce no real surprises, with the caveat that the indicated stall speed is slower than I’d expected. Flaps down, the ST-A finally quits flying at about 37kt, and although at the stall there’s a slight wing drop (which might’ve been caused by the ball being out!) it’s pretty benign, with adequate pre-stall buffet. Lowering the flaps only reduces the stall by a few knots, and there is very little change in pitch trim as they go down.

Having retracted the flaps I accelerate to around ninety knots for a look at the stick-free stability, but the thermal activity makes this exercise difficult. It seems to be positive in pitch, just barely neutral in roll, and practically negative in yaw. The ST-A is certainly very ‘soft’ directionally, possibly because there is considerable keel area ahead of the centre of gravity and this, combined with a not especially large fin makes it feel somewhat directionally unstable, as indeed any aeroplane with ‘sports’ in its name should be. And for pure flying sport the ST-A takes a lot of beating. It’s no Pitts or Extra, but by the standards of the day it must’ve seemed phenomenal, and there were no manoeuvres in the aerobatic catalogue of the period that it couldn’t do. Famed American aviator ‘Tex’ Rankin flew his 150hp ST-A Special to victory in the 1937 US National Aerobatic Championships (folklore holds that he used to begin his display with a dive well past Vne), and the only comparable aircraft of this vintage that I’ve flown is the Bücker Jungmeister (see Pilot January 2015).

FLIGHT TEST ST-AFLIGHT TEST ST-A

Of course, the Jungmeister’s single seat certainly makes it less practical, while the biplane configuration provides a much more limited field of view than any monoplane. In this respect, the ST-A really is excellent and far superior to biplanes of a similar−or indeed any−vintage.

You’ve probably worked this out by now, dear reader, but the ST-A is a very special aeroplane. With taut handling, a responsive engine and plenty of the charisma and charm unique to the open cockpit, all wrapped up in a luminous monoplane masterpiece of burnished argent it’s just fantastic, and even sounds great. The streamlined flying wires sing their own song, with the baritone roar of the engine providing the perfect counterpoint. Throw in a sunny day and what more could you ask for? The visibility is excellent, and as Cardington’s huge hangars slide under the wing it almost feels as if I’m flying a time machine. These Bedfordshire skies have seen some amazing aircraft (and thanks to the Shuttleworth Collection, they still do) and as I point the shapely spinner back towards Old Warden I can’t help but wonder what Richard Shuttleworth would’ve made of the ST-A. I reckon he’d have loved it!

FLIGHT TEST ST-AFLIGHT TEST ST-A

On the way back I cruise at a comfortable 1,750rpm, which gives 104mph (90kt) IAS for a fuel flow of approximately thirty lit/hr. Overhead the airfield the windsock shows that the wind has backed slightly, although not enough to make life difficult. My experiments with the flaps have convinced me that−as Dodge had implied−they’re not worth monkeying with, so rather than keep swapping hands on the stick for the five different settings, I elect simply to drop full flap when I’m abeam the numbers. Proceeding downwind in an orderly fashion I wait until the wingtip appears to be almost touching the threshold, then select carb heat on, throttle slowly back, trim for 85mph, swap hands, full flap, swap hands again, tweak the trim, pause and then turn.

More by luck than judgement, a nicely curved, continuous base leg onto final turn produces a near-perfect constant aspect approach, and I add just a hint of power halfway round to shift the aiming point slightly further into the field. The field of view all the way round is good, and as I’m flying a fairly steep approach I never lose sight of the runway, even on short final.

FLIGHT TEST ST-AFLIGHT TEST ST-A

Over the hedge; stick and throttle smoothly back together (the throttle is almost closed anyway) and the Ryan settles slightly, the wheels feeling for the ground. There’s that fleeting, floating moment and I wait for the subtle and seamless transference of weight from wing to wheel. Boing! Through a combination of the runway’s slight upslope, the long-stroke undercarriage and pilot ineptitude, the wheels hit the ground while the wings are still thick with lift and I’m flying again, albeit briefly. It probably feels worse than it looks, and nothing falls off−but subtle and seamless it isn’t!

The ST-A rolls out straight and true, over quite a short run. Of course, as we all know, landing on grass greatly deskills the taildragger, but nevertheless as the speed drops I remain ready for a swing that doesn’t come. However, I suspect landing on tarmac is a much more fraught affair, and in fact the type has quite a reputation for ground looping−which is somewhat ironic as the Ryan sales literature of the time proclaimed that ‘the new tailwheel swivel lock, controlled from the pilot’s cockpit, makes ground looping virtually impossible’.

FLIGHT TEST ST-AFLIGHT TEST ST-A

An hour later and I taxi out again behind Peter’s Magister, which is being flown by Jean with photographer Darren. For this takeoff I leave the flaps up and can’t really discern any difference in performance.

Now, here’s a little secret: although the ST-A looks like it’s moving fast when it’s standing still, when it is moving it isn’t as fast as it looks! Despite the fact that the rather mundane-looking Maggie is two-up and I have a fair bit of geometric cut-off, it’s soon apparent that I’m just not catching up. A glance at the ASI shows 120mph, but something just doesn’t feel right. Later that evening Jean explains that the ST-A is fitted with what he describes as a “salesman’s static”. Basically, the position of the static port is such that it under-reads at the slow end of the speed spectrum (and thus the aircraft seems to stall at a very low speed) but overreads at high speed. Consequently the indicated airspeeds are both slower and faster than they actually are−a salesman’s static indeed!

FLIGHT TEST ST-AFLIGHT TEST ST-A

My second landing is slightly better, which I’m relieved about as the crowd is now quite sizeable. The aeroplane is really causing a stir, which is not surprising as there are fewer airworthy ST-As in the world than there are airworthy Spitfires in the UK−so if you want to be the star of the show this is the aeroplane for you. It’s a real scene-stealer, and I can almost hear the clicking of dozens of camera shutters above the noise of the engine.

Having climbed down carefully from the cockpit (while doing my utmost not to leave any fingerprints) I walk a few metres away and then turn to admire the aircraft one more time. As Darren’s fabulous photos clearly illustrate, it really is a lovely-looking flying machine and, by the standards of the day, has performance to match. Every sporting pilot in the USA wanted one and I don’t think it had a direct competitor. In the 1930s two-seat trainers fell into two distinct categories: light cabin monoplanes of between 40 to 70hp and open-cockpit biplanes of up to 220hp. Neither group was as fast or as aerobatic, and nothing else looked even half as good. Indeed, bearing in mind that most countries still had biplane fighters in frontline service in 1940, the sleek, sexy ST-A must have been a real head-turner in 1935, and it continues to turn heads, 81 years later. Why? Simple – it’s one of the best-looking aircraft ever made!

PIL JUNE16 FLIGHT TEST Ryan ST-APIL JUNE16 FLIGHT TEST Ryan ST-A

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