From The Cockpit – Grumman American AA Series

The AA-1 American Yankee design was initially developed by American Aviation. Upon acquisition Grumman tailored the design as the AA-1A Trainer, a specialised trainer version. From a first flight in March 1970 the Trainer achieved certification in mid January of 1971. The Trainer was basically a two seater offering side by side seating and powered by the Lycoming O-235-C2C driving a 71in McCauley prop.

The emphasis in the AA series design is upon simplicity – no more so evidenced than in the wing structure. The number of components was reduced to a near minimum by the use of a light alloy tube about Bin in diameter as the main spar and integral fuel tank in each wing. The number of ribs is small and the thicker gauged skins are fastened to the substructure by adhesive bonding; the skin joints are covered by thin chordwise straps, enhancing the aerodynamic cleanliness of the wing surfaces, free from parasitic protuberances. The wing is profiled to a NACA 64 series laminar section. Likewise the aileron and flap are of bonded construction, honeycomb and light alloy, with surfaces clean and smooth, attachment hinges being internal.

Simplicity of design is also predominant in the landing gear configuration. The fixed main gear legs are of straightforward glass fibre leaf spring construction, whilst the tubular steel nosegear is free swivelling and S shaped for flexibility and trailing castor action. Without nosewheel steering, differential braking must be used for ground steerage.

Fuselage construction is aluminium honeycomb for the cabin structure and semi-monocoque light alloy construction for the rear fuselage – all using adhesive bonding. By this means, the lower cabin skin also constitutes the floor to the cockpit – maximising leg and headroom, but necessitating use of a central tunnel between seats for flight control torque tube and cable transport. Below the seats is located a tubular spar carry through, providing the attachment points for the wings and main landing gear. The empennage surfaces are conventional, with anti-servo action on the elevator.

The Lycoming 0-235 is fed from the tubular spar fuel tanks, of total capacity 24 US gallons (83 litres). Filler caps are out near the tips. The aircraft’s electrical system, powered from a 25Ah battery and a 60A 14V engine drive generator, is used to drive the flaps only, in addition to flight instrumentation, lights and avionics. Grumman American offered for the airplane a wide range of avionics, both Narco and King.

The Tr-2 was marketed as a deluxe equipped variant of the Trainer, aimed at broadening the marketbase to include the sports aircraft sector. Maximum takeoff weight remained at 1,560lb, for a maximum useful load of 525Ib – really, a little airplane.

To further expand the range, the AA-5 Traveler was developed in quick time – basically a four seat more powerful version of the Trainer. The prototype AA-5 flew in August 1970 and certification was granted on 12 November 1971. Engine for the AA-5 was the Lycoming O-320-E2G of 150bhp. Not only was the fuselage extended to increase cabin volume but the empennage surfaces were changed and the wing area extended from the mere 101sq ft of the AA-1 to 140sq ft – involving an expansion in wingspan from 24. 5 to 31. 5 feet and a chord increase from 4. 1 to 4. 5 feet. The extended wingspan enabled the fuel tank capacity to go up to 38 US gallon total, providing for a VFR range increase from 370nm for the AA-1 to 434nm.

Cabin accommodation on the AA-5 is for a total of 4 adults in relative comfort. The Traveler then underwent cosmetic changes to become the AA5A Cheetah and was then re-engined with the Lycoming O-360-A4K to become the AA58 Tiger.

This was where the line finished. Cheetahs and Tigers, marketed at the height of the heady sales heyday of the mid and late 1970s sold well worldwide – the US and Australia as well as Europe where, in the UK, they are still a very popular training aircraft. There is little visible difference between the Cheetah and Tiger; however in the hot Australian summer environment the extra 30 horsepower was most welcome in improving hot and high field performance.

With the Motor Running

The cockpit is entered over the wings, after first sliding back the very large canopy. Assisted by the canopy’s long 40in sliding track entry to the rear seats, entry is effected relatively easily, stepping in from the wing roots. For a small aeroplane the AA-5A/B has excellent internal dimensions. The sense of spaciousness is to a substantial extent due to the large transparency area. For operations anywhere on the mainland tinted windscreens are a necessity – to reduce the greenhouse effect and cut down on reflected glare.

From the pilot’s seat the panel is low and visibility over it is unobstructed both on the ground while taxiing and in the air. The panel is also shallow, only deep enough for two 4in instruments and subsequently scan of an IFR panel is stretched by the location of the ADF, RBI and VOR/LLZ/GS indicators to the right of the flight instruments and tacho. Good use is made of the large centre pedestal which separates the seats and covers the flight controls runs. The panel has an eyebrow shroud feature, provid ing good protection against sunlight reflection. The pedestal contains power management controls at its top and has a simple fuel management panel below. I place much emphasis upon the design and presentation to the pilot of fuel management systems in light airplanes. In both areas the AA-5 airplanes excel – the pedestal presentation shows a fuel selector for each (wing) tank and below them the fuelselector, pointing to either the left or right tank indicator – a clear indication not only of fuel quantity but of fuel path to the engine.

Below the fuel management panel is located the variable flap selector and indicator _and elevator trim wheel, both nicely positioned to touch.

Bearing in mind the overall relatively small dimensions of the AA-5A/B, the cabin is particularly spacious – a good 41in maximum width and 35. 4in pitch for the rear passengers. Having flown with a total load of 3 adults and 2 children from Eagle Farm to Parafield this writer can personally attest to the quite comfortable accommodation. Furthermore the AA-5A/B’s cabin is versatile: the rear seats can be folded flat to make a flat area of about 60in by 38in for carriage of a maximum of 340Ib cargo, whilst retaining the cargo compartment’s 120Ib capability aft of this area.

Now let’s see how the aircraft’s lifting capability goes: take the Tiger, the more utility minded variant due to its more powerful engine – typical empty weight 1,388Ib, full fuel and four adults leaves 26Ib for baggage. Alternatively single pilot operation with a full cargo load of 460Ib and full fuel leaves plenty for an enormous packed lunch and tea.

In recognition of its limited range, a larger tankage option was offered with the Tiger – keeping the spar tubes dry and using integral rib/skin formed inboard tanks, providing a total usable fuel capacity of 51 US gals – giving a VFR reserve range of 570nm at 8,000ft at 65% Maximum Continuous Power (MCP).

Few light aircraft have nosewheels. Although AA-5’s provide a good introduction to nosewheel steering, it nevertheless required practice. In nil wind the nosewheel stays where it is put with a touch of differential braking; to stop the turn the opposite brake must be applied in order to straighten the nosewheel again. Crosswinds require a perpetual dabbing of the leeward brake in order to keep the airplane from weathercocking. But it is a deal easier than asymmetric taxiing in a turn with a castoring nosewheel. Takeoff performance on the Tiger is useful for ALA operations – at sea level in 40°C temps the distance to clear 50ft remains less than 2,000ft; flaps remaining up actually being the standard takeoff technique.

In the air the AA-5A/B have excellently responsive controls, particularly in the rolling plane. Nose attitude in a cruise climb remains sufficiently below the horizon to keep the flightpath ahead clear. It takes initial adaptation to trim the nose low enough for level cruise flight if you are used to a Cessna or Cherokee nose attitude.

The AA-5A/B’s aerodynamically clean wing contributes a significant amount to the aeroplane’s impressive level speed performance: at its 75% MCP full throttle altitude of 8,000ft the Tiger will true out at 139 knots, gross weight. At a more reasonably RPM of 2,500 at this altitude (equating to 61% MCP) the TAS reduces to 125 knots, with an accompanying 5% increase in range. The Tiger won’t shirk in getting up there either – 13 minutes at a speed of 85 knots IAS to 8,000ft.

The Tiger makes for a good cross country flier. We started early one mid January morning, out of Parafield bound for Brisbane. A cloudless sky, direct to Dubbo in four hours across the brown featureless landscape with quite passable cruise stability, both in pitch and roll. Out of Dubbo in the afternoon, thermals and convective instability had taken their toll over the Divide and through some of the milder cumuliform I found the Tiger to be likewise a reasonable IF platform. At Brisbane after a further 4 hours elapsed time from Dubbo, the only casualty of the trip had been the reputation of tomato sandwiches, which in our lunchbox, warmed up with the day and got an instant and irreversible (to this day) reaction of dislike from my wife, who was at the time in early expectancy with our first son.

The return trip showed up one quirk of the Tiger – engine vibration splitting the prop spinner a good 4in on the first sector. Reportedly common on the Tiger, we also had the same problem on Desmond Norman’s Freelance, which is powered by the O-360-A1A.

A useful little aeroplane is the Tiger, worth a look at this end of the market while Cheetahs are far more numerous – a little more load for a little less performance. Cheetahs have found widespread use as trainers, far more so than the two seat Yankee or Trainer, following the aero clubs’ preference for 4 seat over 2 seat aircraft.