By Boran Pivčić

Every now and then, I get the urge to dig through the Airliners.net database looking for “oddball” aircraft – aircraft that almost made it to life, made it but sank into obscurity, or simply served as platforms for famous aircraft before being forgotten and discarded. My fascination with the above almost always centers on the Big Three – Beechcraft, Cessna and Piper – big corporations that produced some of the most famous aircraft of all time… and naturally had some upsets along the way.

Cessna – with their diverse line of everything from the 150 to the Citation X – naturally caught my attention first and it didn’t take me long to find three candidates that perfectly fit my criteria. As such, these aircraft had to be mass produced at some point in their lives and sold to civilian customers, but be little known and quite rare today. The list could have gone on for awhile, but I chose the 175 Skylark, 205 Super Skylane and the 336 Skymaster.

1. Cessna 175 Skylark:

Years produced: 1958-1962

Cessna 175 at Airliners.net
Cessna 175A at Airliners.net
Another 175A at Airliners.net
Cessna 172B at Airliners.net
Cessna 175C at Airliners.net

The most common of the three aircraft chosen, the 175 was designed to fill the gap bewteen the Cessna 172 – then still in infancy, with just two years of production behind it – and the larger and significantly more powerful 180. As such, it is an evolution of the 172 designed to accept the more powerful Continental GO-300 engine. Rated at 175 HP (versus the 145 HP of early Skyhawks), this engine was a bit of an oddity for a single engined plane, being geared (the G prefix) rather than direct drive as most piston engines are. A common solution on high-power twins of the era, geared engines had a reduction gearbox between the crankshaft and the propeller, allowing the engine to spin at a higher RPM while keeping the prop at lower speeds. Depending on your wishes, this allowed you to either crank the engine up to a higher speed to give more power while keeping the propeller tips below the speed of sound, or reducing prop RPM to make the plane quieter (or a combination of both as in the case of the 175).

Apart from the engine – and the redesigned cowl to accept the gearbox mechanism – the 175 incorporated some minor differences, but pretty much from the exterior looked like any 172 of the era. A little known fact is that the later, higher-powered 172 versions – such as the 195 HP Hawk XP, the 210 HP Reims Rocket, the military T-41 and the retractable 172RG – were evolutions of the 175 design, rather than the basic 172. Fitted with Cessna’s “Omni-Vision” rear windows and direct drive engines, these aircraft were all based on the later-model 175, but marketed as 172s. Indeed, I’ve personally often been in a position to compare the two, flying 9A-DDD, a stock 172N, and 9A-DMJ, an early model FR172F Rocket. DMJ, being based on the 175 which is based on the 172 and 172A, has the narrower and taller undercarriage and tighter cabin, while DDD, produced when the 172 design pretty much froze, has the wider track and lower main gear and more spacious cabin (when I started flying these two, I’ve often wondered why I couldn’t see as much of the main gear from the cabin in DMJ as I could in DDD).

Despite the increased grunt, the 175 was not a major success, with about 2,100 built. The main culpit was the GO-300, which proved to be a bit unreliable – though many now say that it was more the fault of operating technique than the engine itself.  Many pilots without experience on geared engines ran the GO-300 in the lower 2,000 RPM range common on direct drive engines. Designed for the higher 2,000s – around 2,800 as recommended by 175 type clubs – the engine didn’t get all the cooling it needed, leading to frequent breakdowns and relability issues.  A number of sources say that some owners have even switched to larger-displacement direct drive engines, partly due to the added costs of servicing the gearbox (and the fact that parts and rated mechanics for these nowadays very rare engines are increasingly hard to find).

(of note: unlike today, where both the model number and model name are part of the designation, in the 50s and early 60s, Cessnas designated with just the model number were the basic versions, while those with a model name were the deluxe models. So, the “175” was a cheapo model, while the “175 Skylark” was the full-option version. The same was with the first few models of the 172)

Specs for basic, A and B models (Rising Up Aviation): http://www.risingup.com/planespecs/info/airplane279.shtml
Specs for C model (Rising Up Aviation): http://www.risingup.com/planespecs/info/airplane278.shtml

2. Cessna 205 Super Skylane:

Years produced: 1963-1964

Cessna 205 (210-5) at Airliners.net
Another 205 at Airliners.net
Cessna 205A (210-5A) at Airliners.net

While the 175 is not all that obscure, the next aircraft on the list could certainly qualify – despite being the stepping stone to one of Cessna’s most famous piston singles. With a family tree stretching back to the 182 Skylane, the 205 was essentially a 210 Centurion (itself a beefed-up 182) with a fixed undercarriage and an interior optimised for utility, rather than comfort. Evidence to that is it’s official Cessna designation, 210-5, as well as the chin on the front cowl where the nose wheel would have been stowed on the early 210 models – some sources say this was later used to house radio equipment, though one would wonder about the heat from the engine.

That took the form of the six cyl normally aspirated Continental IO-470 from the 210B, rated at 260 HP, driving a constant speed propeller (usually three-blade, but photo evidence shows a number of two-blade models as well). Like the early 210, the 205 did not have the split rear doors that would debut on its follow-up, the famous 206 Super Skywagon/Stationair (early versions of which still had the cowl chin).

The small production run of just under 600 aircraft over two years meant the 205 was offered in just two versions, the basic 205 and the touched up 205A of 1964. Being a converted tourer, it wasn’t all that practical for utility work and was replaced the same year by the more powerful and purposeful 206.

Specs (Rising Up Aviation): http://www.risingup.com/planespecs/info/airplane233.shtml

3. Cessna 336 Skymaster:

Years produced: 1963-1964

Cessna 336 at Airliners.net
Another 336 at Airliners.net
And another at the same site

A Skymaster you say? But they’re not obscure… despite clearly deserving the “oddball” epythet any way you put it :). Indeed, the 337 Super Skymaster is a relatively common sight today, but it’s predecessor, the “normal” 336 Skymaster, is a first class rarity today as it was during its production run.

On the ground, it’s hard to tell them apart at a single glance (despite the 336 being a tad smaller) and only the most astute will notice a most interesting oddity on the 336 – the fixed undercarriage. An unusual configuration for a twin, I must admit I was instantly interested when I learnt of this a couple of years back – despite the Italian Partenavia (former Vulcanair) P.68 light twin sharing the same trait.

Initially, the 336 was designed as a four seater, built around two 175 HP GO-300 engines, the same as on the Skylark. Only the prototype was built in this configuration however, the design being changed to accommodate six, as well as  new 195 HP direct drive IO-360 engines, before deliveries began. Other changes included larger vertical stabilizers, revised wings and some other minor changes to improve handling.

Like the 205, the 336 had a short life and only 195 were produced in a single version before production switched to the bigger, more powerful – and retractable – 337 Super Skymaster (the Super later being dropped).

Specs and performance comparison with 337s (Skymaster.org.uk): http://www.skymaster.org.uk/perform.asp