Cessna 175 Skylark

The Cessna 175 is a light four-seat, single-engine, fixed wing aircraft produced by Cessna between 1958 and 1962. A deluxe model known as the Skylark was introduced in 1960. The aircraft is similar to the popular Cessna 172 but has higher gross weight and a more powerful engine with a geared reduction drive.

Declining sales stemming from reputedly poor engine reliability prompted Cessna to drop the 175 and Skylark nameplates, but the company continued to produce aircraft based on the 175 for several decades, selling them as variants of the 172 and as a military trainer aircraft, the T-41 Mescalero.

Production history
The 175 was designed to fill a niche between the Cessna 172 and the slightly heavier, larger and faster Cessna 182. The engine of the 175, a reduction drive or geared version of the O-300 (Continental GO-300) used in the 172, is rated at 175 hp (130 kW), or 30 hp (22 kW) more than the engine offered in the contemporary 172. Between 1958 and 1962, a total of 2,106 were built. The basic airplane was marketed as the 175, and the plane with a package of optional equipment and overall paint (a partial paint scheme was used on the basic model) was marketed as the Skylark.

Design
The airframe of the 175 is all metal, constructed of aluminum alloy. The fuselage is a semi-monocoque structure, with exterior skin sheets riveted to formers and longerons. The strut-braced high wings are constructed of exterior skins riveted to spars and ribs. The 175 has fixed landing gear in a tricycle arrangement, with main gear legs made of spring steel, and a steerable nosewheel connected through an oleo strut for shock absorption.

While it incorporates airframe changes to accommodate an increased gross weight, the 175 is similar in appearance to the 172 of the same vintage. The most noticeable difference is the distinctive hump in the forward cowling of later series airplanes to accommodate the engine's reduction gear. Although externally identical to the 172 with most parts aft of the firewall being interchangeable, the 175 was built to a different type certificate. The R172K Hawk XP and T-41B/C/D Mescalero share the 175 type certificate, along with the 172RG, the retractable landing gear version of the 172.

The GO-300 engine
An unusual feature of the 175 is the geared GO-300 engine. Whereas most single-engine airplanes use direct drive, this engine drives the propeller through a reduction drive, so the engine runs at 3200 rpm to turn the propeller at 2400 rpm (4:3). The GO-300 engine suffered reliability problems and helped give the 175 a poor reputation. Some Skylarks flying today have been converted to larger-displacement direct-drive engines though almost 90% still retain the GO-300.

The GO-300's tainted reputation is largely undeserved, since its problems were the result of pilots who were unfamiliar with gear reduction engines, simply not operating the engine at the higher RPMs specified in the C-175 Pilot's Operating Handbook. Pilots unfamiliar with the engine often operate the engine at the low RPM settings (2300–2700) appropriate to direct-drive engines, while the 175's Operating Handbook calls for cruising at 2900 RPM. The low RPM causes harmonic vibration in the reduction gear between the quill shaft (that turned the propeller) and crankshaft, and the low power results in low airspeeds that prevents the engine's air-cooling system from operating effectively, resulting in chronic reliability problems for engines not operated at the recommended power settings.

Variants
Cessna has historically used model years similar to U.S. auto manufacturers, with sales of new models typically starting a few months prior to the actual calendar year.
 * 175
 * Introduced for the 1958 model year with a geared 175 hp Continental GO-300-A or -300-C engine with a shock-mounted cowling. Other differences from the 172 include a one-piece "Sight-Sweep" windshield and a gross weight of 2350 lb.  Standard equipment included adjustable front seats, electric gauges, panel-mounted fuel drain control, safety-designed control wheels, and stainless steel mufflers.  Optional wheel fairings were also available.  The 1959 model year introduced new control wheels and was available in seven paint schemes (up from four in 1958), but was otherwise identical to the previous model year.  Certified 14 January 1958.  702 (1958) and 536 (1959) built.


 * 175A
 * 1960 model year with a redesigned swept tail, a 175 hp Continental GO-300-A, -300-C, or -300-D engine, an external baggage door, and reduced nose geat oleo strut travel. This model was approved for seaplane operations with a gross weight of 2450 lb.  A deluxe model was introduced under the name Slylark with a higher empty weight, full exterior paint, a refined interior, and wheel fairings as standard.  Certified 28 August 1959.  540 built.


 * 175B
 * 1961 model year with an electric starter, a "Blend-Temp" ventilation system, "Polycloud" seat lining, and optional reclining front seats. The deluxe Skylark also featured an engine-driven vacuum system for the gyroscopic flight instruments.  Like the 175A, the 175B was approved for seaplane operations.  Certified 14 June 1960.  225 built.


 * 175C Skylark
 * 1962 model year with a 175 hp Continental GO-300-A or -300-E engine, new wingtip fairings with position lights, a revised cowling with cowl flaps, a dual-beam landing/taxi light on the left wing, a new two-bladed constant-speed propeller, and gross weight increased to 2450 lb. The baseline model was dropped for this model year, therefore all 175Cs carried the "Skylark" name.  Certified 18 September 1961.  117 built.   This was the last model to carry the model number 175, though future variants of the same type certificate were marketed as variants of the Cessna 172.