From The Cockpit- Cessna 172

The 172 is a four-seat single-engine, high wing aircraft of all metal construction. Because of the sheer number of 172s built (over 33,000 built and around 850 on the local register), there are many pilots amongst us who know the 172 well, not only through usage for efficient personal flying, but also through learning basic skills as student pilots and have come to regard the 172 as the doyen of ‘utility and simplicity’ in small aeroplanes.

The Model 172 emerged onto the market from Cessna’s Wichita factory in 1955. Technically speaking, it was a major modification of the Model 170, a four-seat taildragger introduced 7 years earlier. The switch to a tricycle undercarriage was a conservative response, time wise, to the emerging preference of user pilots, spawned by several aircraft models of the Second World War. (On the other hand, Beech had capitalised upon this market switch in a far more prompt fashion with the Bonanza. ). The tricycle landing gear on the 172 made for easier ground handling; the other feature significantly different to the 170 was a change to the vertical tail profile (to an upright squared-off shape).

The early 172s had the reliable 0-300 Continental parked under the cowling, delivering 145 horsepower to a 2-blade fixed-pitch propeller.

In the 1960 model of the 172, Cessna swept back the vertical tail, giving it the distinctive appearance which has endured to the present (and which in part contributes to the ‘mosquito’ appearance the 172 takes on when viewed in the air from a distance). The 172 gained market acceptance quickly, as well as interest from across the Atlantic. By 1963 an agreement had been established with Reims Aviation for licence production of the 172 in France; these aircraft were fitted with O-300s produced by Rolls Royce in the United Kingdom, similarly under licence.

The Skyhawk name was introduced in 1961, more as a marketing initiative than anything else, as it referred to a deluxe or ‘options included’ version of the aircraft, including an overall paint scheme, a push button starter instead of the pull starter switch and an engine driven vacuum pump, in lieu of the external venturi for the suction-driven gyro instruments The fuselage shape was modified in the 1963 model of the 172; the rear windows were included in the re-shaped cabin, successfully exploiting the psychological function of transparency area to open-up or expand relatively confined volumes.

Also in that year, the militarization of the 172 was developing: the R172E variant was made more powerful by swapping the 180hp 0-360 Continental (type approval coming in 1964). With an injected 10-360 engine installed in 1966/67 the R172E saw service with the US Army as the T-41B and with the US Air Force as the T-41C and 41D (differing by the addition of a CSU propeller and a 28 volt electrical system).

The steady success of the 172 was reflected in production/ sales figures: by 1966 a total of more than 11,000 172s/ Skyhawks had been built; by mid-1967 the number had risen to 12,000. The clever combination of comfort and reasonable efficiency for a medium-performance four-seater was very well accepted by the market. At that time the model was the 172H, with modifications including a shorter nose leg, cowling attachment dampers, a pneumatic stall-warner (consisting of a tube to a leading edge vent at one end and a sound-generating reed in the cabin at the other; this type of stall-warner, although novel in concept, didn’t last on the aircraft). Flyaway prices of the aircraft were $US10,950 ex-Wichita and $13,750 ex-Reims for the F172H. MTOW of the 172H was 2,300Ib and standard useful load 1,020lb; maximum speed 138mph and 75% power cruise, 130mph on 6. 9 JG/hr of Avgas 80/87.

1968 saw the introduction of a 60amp gear-driven generator on the 0-300 providing ‘radio capability even when taxiing slowly’, as well as ‘open-view’ (rams horn) control wheels to ‘view all instruments with ease’ and refashioned spoke hubcaps and speed fairings.

Closely following came the model 1721 and deluxe Skyhawk with the 150hp Lycoming O-320-E2D engine now installed. Options included a wing leveller, apparently in response to the fashion at that time. The engine did little to performance – top speed now 139mph, 75% power cruise, 131mph at 9,000ft.

By this time more than 14,000 172s and Skyhawks had been sold. A statistical breakdown of usage is of interest: 58% business or personal use, 16% company owned for business (or corporate) flying, 14% training, 6% air taxi/charter and 1 % spe cial applications mods, particularly agricultural.

Cessna continued with calculated and conservative improvements to the 172. 1973 saw the re-profiled wing introduced: the original wing was of a standard NACA 2400 section. For the change, the leading edge radius of the section was increased and drooped slightly (the droop increased outboard, to improve the stall resistance of the wing, particularly over the outer wing section, ie. the aileron location thereby making the stall handling qualities of the aircraft more benign).

The 1974 FR172 came with the O-302-D; same MTOW, 2,300Ib, saw this aircraft haul a maximum useful load of 780Ib590lb over 940nm with full tanks. This year also over 360nm, or saw ‘an aberration’- the Reims Rocket, whose cowling housed the 210hp fuel-injected Lycoming IO-360-D, pulling the airframe at a maximum speed of 145mph.

The 172 has progressed further from these formative years. By February 1975, 21,762 aircraft had been built, including a total of

1300 F172s at Reims. The engine was changed to the 160hp

0-320-H in 1979; a troublesome engine it transpired, problems caused by inadequate lubrication of the valve system, together with oil pump breakages. The engine was later changed to the O-320-D2J in 1983 (160hp still).

Other modifications have led to the Cutlass and RG aircraft (the 180hp Cutlass II being the 172Q)- retraction of the landing gear answering the wishes of many 172 exponents eager to see a gain in performance.

Flying the 172

If a simple categorisation of the 172’s flying qualities comes to mind, it is ‘easy straightforward handling’. The ailerons lack effectiveness, particularly at low speed (but it is adequate), the rudder is a bit too heavy, the overhead trim near the wing root leading edges squeaks incessantly in turbulence and in a final approach go-around, with 40 degrees of flap lowered and the aircraft trimmed to 65 knots, the stick force change with full power is nearly excessive (and probably was the reason for reducing

the flap travel to 30 degrees on newer models- the airworthiness requirement calling for a maximum stick force of 50Ib in a go around); but the aircraft, as I recall its use going back to my earliest flying days, makes for a good trainer, whilst for personal/ commercial flying its honest capabilities, particularly in and out of airstrips, makes it attractive to pilots generally.

The aircraft’s field performance is in no small order due to its large and effective single-slotted flaps, which result in a stall speed for the aircraft of 46 knots at 2400lb gross weight. The flaps do in fact include some Fowler action, extending the wing chord as they are lowered.

As a popular and typical small airplane NASA has conducted quite a deal of stability and control research on the 172, including involvement in the stall/spin programmes (with many spins flown, ‘discovering’ a fast, nose-steep and high rotation spin, easily recoverable).

Operationally, the 172’s large centre of gravity range provides for loading flexibility. As a typical loading example, consider a representative 172M – empty weight 618kg (basic radio kit only),

gross weight 1043kg- a weight margin for pilot and three pax, full fuel in standard tanks of 144 litres capacity (enough for a 65% cruise range at 5000ft of 575nm, no reserves) and a very small amount of baggage. The optional long-range tanks increase fuel capacity to 182 litres at the expense of some payload, ie. one passenger less.

The Market

There is an enormous range of 172s on the Australian used aircraft market. The older the airframe, the greater is the variation in prices with avionics fitments. Mid-60s models of the 172/ Skyhawk, such as a 172H or 172F list VFR in the high teens, $17,000 to $19,000, with limited engine hours, rising to $23,000 to $25,000 for a NVMC/LIFR aircraft with good engine/prop hours to run.

Prices for 1972 to 74 models, LIFR with about 1000hrs ETA command mid to high $30,000s; there is considerable overlap with the late. Os models, such as 172Ns and Skyhawk cells, which with similar NVMC avionics may vary in price between $38,000 and $45,000. Of course to these ranges there are all exceptions freshly majored 1979 172N with high ETA hours may list in the $60,000s.

However the asking prices jump for aircraft of production years in the 1980s, for example, a 1981 Hawk XPll listing for $70,000 and a LIFR 172RG, with a list price approaching $90,000.