Flight test: Aeronca 11AC Chief
PUBLISHED: 13:39 30 January 2020 | UPDATED: 13:39 30 January 2020
Possessing many benign qualities, the Aeronca Chief earns our respect | Words Dave Unwin - Photos Keith Wilson
As the Chief settles gently onto the grass I glance at my watch. It's exactly 0900, which is precisely when Nils Jamieson had said he'd land. If he flies his 737 with the same precision (and I suspect he does) it's no wonder Jet2.com has such a fine reputation!
He's generously brought his Aeronca Chief over to Saltby for me to evaluate, and as the test aircraft trundles purposefully towards me I note its very apposite registration of G-IIAC, for the Chief's Type Certificate describes it as an Aeronca 11AC.
I must admit straight away to a real soft spot for Aeroncas (sometimes also referred to as 'Airknockers'). Although the first aircraft I ever soloed was a Schleicher K-13, and the first powered aeroplane a Cessna 150, it was in a 7AC Champ that I really learned how to fly.
So, as the neat little taildragger taxis towards me, I'll admit my enthusiasm generator is firmly on line, for despite hundreds of hours in Champs, Citabrias and Decathlons I've never sampled a Chief.
Owned by Jet2's 737-800 Fleet Technical Pilot (and GASCo Regional Safety Officer) Nils Jamieson, and known as Mabel, she rolled off the production line in 1946 and was the 169th Chief built.
After many years of flying in the US and then Canada Mabel arrived at Compton Abbas in 1991 and has been owned by Nils since 2014. Incidentally, if you think Mabel looks familiar it's because she is often used by GASCo for the preflight challenge at the LAA Rally.
Closer inspection soon confirms that the Chief is typical of the classic US light aircraft of the late forties and early fifties, being a strutted, high-wing taildragger powered by an air-cooled flat-four and featuring a fabric covered welded steel tube fuselage and wood-spar wing.
Devised by Aeronca's Chief Designer Ray Hermes (who also designed the Champ) it was built with eighty per cent commonality of parts, offering several advantages and enabling Aeronca to keep the price down. This is a fine example of American pragmatism and explains at least in part why the US eventually dominated light GA. In Britain, we'd probably have kept the seats and pedals and redesigned everything else!
The motor is quite closely cowled and access to it is excellent, as the cowling opens wide on both sides. Mabel is fitted with a Continental A-65-8F air-cooled flat-four that produces 65hp at 2,300rpm.
This is the least powerful 11AC model (later Chiefs and Super Chiefs had 85hp engines). As delivered from the factory it had a wooden Sensenich two-blade fixed-pitch prop, but these days has one built by well-known prop maker Chris Lodge.
The engine is fed from a single fuel tank mounted between the engine and cockpit, with an auxiliary tank behind the cockpit which feeds into the main tank. These have capacities of 57 and 30 litres respectively, for a total of 87 litres.
The wing is essentially the same as the Champ's but the side-by-side seating increased the effective wing area from 15.79sq m to 16.25. However, as the Chief is also slightly heavier (a MAUW of 567kg against the Champ's 553) the net result is that the Chief has a lower wing loading but also an inferior power to weight ratio when compared to its tandem sibling.
The undercarriage is of the fixed, divided type and consists of two interchangeable side-vees that use oleos in the front legs for shock absorption, while the wheels are fitted with the original cable-actuated heel operated Van Sickle drum brakes. A solid Scott tailwheel is suspended from the traditional spring-leaf arrangement and steers through the rudder pedals.
Wings and fuselage are essentially conventional in both design and construction. The fuselage features a triangular cross-section aft of the cockpit and is constructed of welded steel tubing and plywood formers, while the wing consists of wood spars and aluminium ribs. The tailplane is wire-braced and there is a trim tab in the left elevator and a length of cord doped into the rudder's trailing edge.
I was intrigued by the champagne cork at the top of the rudder. Nils explained that the rudder post is a steel tube which is open at the top. To prevent moisture ingress and corrosion he treated the tube with ACF-50 and put a bung in the top.
And as he explained, "what better bung than the cork from the champagne drunk to celebrate buying her?"
Access to the cockpit is via a door on each side. Climbing in requires a degree of dexterity that I don't recall with a Champ, but then I am twenty years older−and ten kilos fatter!
Anyway, it wasn't too onerous, and is certainly easier than a Cub. Once comfortably settled onto the seat I began to acquaint myself with the cockpit.
The rudder pedals are fixed but the bench seat adjusts, and once strapped down it seemed to me that the cowling line was a little lower than the Champ's, affording a slightly better field of view on the ground. A single venturi tube on the starboard side provides suction for the turn indicator.
The cockpit is delightful, and also delightfully simple. The top row of instruments is dominated by a large, suction-driven turn and slip in the centre, with the altimeter to its left and ASI to its right, flanked by oil pressure and oil temperature gauges.
The next row down consists of a large (and optimistic) VSI, an old-fashioned tachometer−which rotates counter-clockwise, and an eight-day clock. Below this there is a subpanel which carries the large, plunger type throttle, small plungers for the carburettor heat, cabin heat, fuel shutoff and engine primer, and a key-operated rotary magneto selector.
The sole concessions to modernity (a Trig transceiver and transponder) are very discreet. The spoked control wheels seem almost disproportionately large, as do the heel brakes, which are on the P1 side only. There is a handle for the elevator trim set into the cockpit roof and a parking brake below the instrument panel. The elevator trim slides fore and aft in the 'normal' sense.
The main tank's fuel gauge is set into the instrument panel forward of the compass, and the auxiliary tank's is above the parcel shelf. Interestingly they are the same type as fitted to a Model A Ford and display quantity remaining as a fraction.
The correct method is to run the main tank down to half full, and then in straight and level flight turn on the auxiliary fuel valve by the P1's left knee. Once this tank has been completely drained (by gravity) you turn the auxiliary fuel valve to 'off' and the main tank is now completely full again.
Simple and effective. As for baggage, there is a big bay behind the seats covered by an aft-hinged parcel shelf which can carry an impressive 70 lb.
Unlike many aircraft powered by an A-65, Mabel is fitted with an engine primer, which is a much better system than simply pumping the throttle (something I never like doing on any aircraft fitted with an up-draught carburettor). Mabel originally had a MacDowell recoil starter but these days is hand-swung. She fires on the second swing and we're good to go.
For a vintage taildragger, the Chief is a relatively easy aircraft to taxi, as long as it isn't too windy. If it is windy it can soon become a bit of a game, as the big fin turns it into a perfect weather-vane. Still, at least S-turning is unnecessary, as visibility over and each side of the nose is quite good, due to the lower cowling line.
The steerable tailwheel is linked to the rudder via springs and works well. Unfortunately, the same can't be said about the brakes, which are probably the worst facet of the Chief (although, in its defence, most aircraft of a similar type and vintage are no better).
These are ghastly heel-operated cable actuated drum units. The pedals are overly large and attached to the rudder pedals (weirdly, on the Champ they're tiny and set into the floor) and their geometry relative to the brake pedals is not good for the ankles.
With such simple systems, the pre-takeoff checks are very straightforward and I roll out onto the runway, line up with the centreline and open the throttle. The ambient conditions are a density altitude of about 650ft and less than 10kt of wind straight down the runway.
With approximately forty litres of fuel in the main tank and an empty aux tank, two blokes on the bench seat and some baggage, we are about fifty kilos below the 567kg MAUW.
Even with only 65 horses pulling, the acceleration−although far from startling−is perfectly adequate and the airspeed soon starts to build. Also, the Chief's strut-braced wing uses a relatively high-lift aerofoil section and is quite lightly loaded.
The best takeoff method is to pick the tailwheel up quite promptly with the powerful elevator, and then ease the aircraft off the ground at about 45kt. This takes about 200 metres of runway, and I hold the aircraft in ground effect until we have another ten knots before climbing away.
The best angle of climb is attained at around 55, but I soon speed up to 59, as this not only improves the view over the nose but also gets us clear of the airfield a bit quicker at a speed that gives us the best rate of climb−around 500fpm.
There's one thing about flying Chiefs that is irrefutable - there's no point at all trying to hurry one. A comfortable cruise speed is around 65-70kt, and although you may squeeze 75 out of one in a pinch you'll be burning a lot more fuel.
Incidentally, the cruise speeds of the various models of Chiefs provide an excellent example of the 'speed squared' law. Despite having almost 33% more horsepower than a 65hp Chief, an 85hp Super Chief still only cruises about five knots faster! The climb rate, of course, is significantly better, even though a Super Chief is heavier.
On the plus side, at 65kt you're only burning around 16 lph, so the single 57 litre fuselage tank provides a still-air range (including thirty minutes' reserve fuel) of around 195 nautical miles. Fill the auxiliary tank and the range is now a very useful 325nm.
We've taken off in stream behind the BGC's EuroFox, crewed by the regular team of pilot Al and photographer Keith, and as I move into formation above the beautiful Vale of Belvoir it soon becomes apparent that I don't have a lot of 'overtake' and will need to make the throttle my intention and not my reaction if I'm to avoid getting left behind when we're on the outside of a turn.
The field of view also isn't great, but Al flies a smooth, sympathetic lead, we get the job done, and I move onto a closer examination of the Chief's control and stability.
In common with most of its contemporaries, the Chief is very much a 'rudder aeroplane' and possesses a significant amount of adverse yaw. Furthermore, the harmony of control is not perfect, as the relatively weighty ailerons are actually slightly heavier than the elevators.
The roll rate is as leisurely as you'd imagine while the field of view in the turn (and most phases of flight) is typical of this type and vintage: not great but acceptable. Moving onto the stick-free stability, the standard checks confirm that it is−unsurprisingly−very stable around all three axes, being strongly positive longitudinally, positive directionally, and essentially neutral laterally.
In fact, while checking the spiral stability to port it is so steady (and the air so calm) that we hit our own wake! The directional stability is not quite as strong as I'd anticipated, bearing in mind that the fin is quite big.
Nevertheless, it is very stable around all three axes, proof that (in common with most American designs of this period) the emphasis was much more on stability than control. However, that's not to say that the controls are inadequate.
Indeed, Aeronca certificated the 11AC in both the FAA's 'Normal' and 'Utility' categories, which means that when flown in the Utility category it is approved for a limited number of aerobatic manoeuvres, including spins. In deference to Mabel's advanced age (and the paucity of parachutes) we only examine the stall but I've no doubt that it would spin quite readily if provoked, although it would recover equally promptly.
Stalls−either power on or off−are very benign. There is no artificial stall warner, but adequate natural pre-stall buffet before the wing quits at about 33kt. Recovery is quick and easy−just release the backpressure.
Even a departure stall is a complete non-event, while if you stall in a turn it simply rolls itself wings level. This really is a very benign aeroplane, and although all aircraft bite fools, the Chief would need to be flown very foolishly before it would bite.
For a look at the cruise I set the throttle so the engine runs at a very comfortable 2,150rpm. This gives an IAS of 65 and a TAS of 69 at 2,000ft. Increasing the power to 2,300 makes a lot more noise and burns considerably more fuel but doesn't much affect the speed. It's a pretty draggy design.
Back at Saltby I close the throttle when abeam the numbers, trim nose-up and get my first real surprise of the entire flight. The Chief has a surprisingly flat glide, and even though I angle the base leg slightly away from the threshold I still turn in too early.
Of course, like most of its contemporaries the Chief slips beautifully, and having corrected the approach with a good sideslip I glide gracefully over the threshold. It should've been perfect, but I don't quite hold it off long enough, and when the wheels touch the wing is still fat with lift.
Boing! The Chief skips down the runway in a series of ungainly bounces. "Oooohh! The undercarriage doesn't seem very well damped Nils, or is it me?" "It's all you", he laughs in reply as we slow to a stop. And things had been going so well...
Suitably chastened I resolve to do better next time, and do. Indeed, after the debacle of the first landing I quickly get the hang of it, and am soon greatly enjoying myself. It's no exaggeration to say that simply shooting touch 'n' goes in a Chief is great fun, for seamlessly shifting the weight from wing to wheel and back again is a sport of which I never tire, particularly when flying a classic taildragger from a grass field.
About fifty knots on final feels good, with 45 over the fence−although if it were windy I'd carry at least 55kt all the way into the flare. The Chief has plenty of drag and not much inertia, so the speed soon washes off. And if you are either too fast or too high, don't worry about the absence of flaps: it sideslips superbly.
Furthermore, if you're landing into a stiff breeze the speed at touchdown is very low. The brakes should only be used−and needed−for taxying, unless the field is very short, and although its tailwheel undercarriage means that it is inherently directionally unstable during the rollout, it is more benign than most.
I really enjoyed myself flying Mabel, and can clearly see why Nils is so enamoured with her. After a week of flying a 737 all round Europe in all sorts of weather it must be very relaxing to watch the world go by at sixty knots.
The Chief is a true classic and this type of machine will always be very special to me, as I really did learn a great deal about the science−and also the art−of flying in the cockpit of a Champ.
There's something very special about flying classic rag 'n' tube taildraggers, something that is difficult to explain and hard to resist.
Whoever it was in Aeronca's marketing department that decided the 11AC's name hit the nail right on the thumb. Hail to the Chief!