This was the article that caused my worry about the ailerons on the rag wing. Steve
Is it correct? Ive marked the section with crying faces.
Coveted Classic: Cessna’s gorgeous 170
By John Miller
The 170 was a major project for Cessna’s wartime-earned manufacturing skills. It was developed from the two seat model 140 and 120 and was hugely important in shaping Cessna’s future single-engine products.
Those of us who regularly fly late model Cessna singles might like to spare a thought about where it all began. That 172s are still being built is a testimony to the aeroplane’s architect à Jeremiah "Jerry" Gerteis, Cessna’s highly respected Chief Engineer. Although Gerteis was an engineering assistant when the two-place 140 was designed, the little taildragger was to define Cessna’s future range of light aircraft. It not only pioneered the large-scale commercial use of Steve Wittman's unique sprung-gear undercarriage (for which Wittman was paid royalties for 17-years), the 140A was the first Cessna to carry the NACA 23-series aerofoil and half-tapered wing platform that was largely responsible for the 172Õs kindly handling.
The 140 and its flapless 120 version were a huge success. The aeroplane’s appeal lay in its remarkable simplicity, excellent flying qualities and durability. Cessna emerged from the 1947 general aviation crash in a strong position thanks to the 140Õs popularity, though production had fallen from 30 aircraft a day to five. Still holding a belief that the public wanted a "family car of the air" and seeing how the Stinson Voyager had rapidly become a best seller, Cessna wanted to launch a four-place version of the 140.
The company wanted to provide as much cabin space as possible, making their new aeroplane a true four-seater. Cessna were also experiencing the vicious downturn in sales that was too many competitors succumb and the close termination of others including Piper. Consequently, the 170 had to be inexpensive and offer as much value as possible. The prototype made use of a lengthened Cessna-140 fabric wing à a cost reducing effort that did not see production. With its big cabin and generous rear-seat legroom, Cessna was obliged to provide a wide centre of gravity range. At the same time the company wanted to bestow kindly pitch stability, stall and spin characteristics at the most rearwards C of G. To get the tailwheel down in a three-point landing configuration, the horizontal tail areas were enlarged at the expense of higher elevator forces compared to the 140.
The 140Õs extended wing was not a happy combination as the short ailerons were not powerful enough to counteract gusty conditions during the flare. Cessna’s development pilots complained that they often used the full 90-degree wheel displacement to keep the wings level in severe gusts
. At the time, Cessna were amazed that some pilots performed wheel landings à a practice even their own test pilots avoided. Early in the 170 programme, the engine mounting was lowered to provide better visibility whilst taxiing.
In June 1947, Cessna hired a new 165hp Voyager from an oblivious Stinson dealer in Detroit. It was used for extensive comparative testing against the 170. The new four-place Cessna had a much bigger cabin and a huge door allowing easy access to the rear seats. In efforts to reduce cost and weight, early 170s had very austere interiors à a feature acknowledged by Cessna who congratulated themselves that their four-seater was a lot easier to land than the Stinson in gusty crosswind conditions. The 170 was launched in 1948 with fabric-covered wings and dual struts. It cost US$5 475 and came with a 145hp C-145-2 Continental engine.
The rectangular planform wing was a headache. Although it provided great stalling behaviour and reasonable speed, the aileron problem was unacceptable. Cessna design engineers, Ozzie Mall and Don Simon, came up with a semi-tapered, all metal, NACA 20-series aerofoil wing. This immediately degraded the 170Õs stalling characteristics. However, by including larger Frise ailerons, control forces were reduced. The stall regime was Cessna’s biggest hurdle at the time and this was eventually overcome by adding one degree of washout outboard of the wing strut attach points. To make matters more complicated, production engineering insisted that the wing tips be interchangeable forcing the wing designers to make an aerofoil profile change towards the wing tips.
It wasn’t all bad news. The new all-metal wing had greater torsional strength allowing Cessna to use only one flying strut. Moreover, the company was able to take the existing Cessna 195 fin and rudder and use it for the new 170A model. The 170A was launched in 1949 and Cessna made a big thing of the optional landing lights installed in the wing leading edge. The company also called for some engine improvements and from 1950 they installed a C-145-2H version of the six-cylinder Continental. The Ô2HÕ powerplant had dynamic drilled-crankshaft dampers, which reduced noise and vibration within the austere cabin. The comfort issue had been a constant thorn for Cessna, despite the large cabin, so the same year they improved the door seals and offered higher grade fabrics for the interior.
The biggest improvement and the most significant one was Cessna’s decision to adopt the model-305 Bird Dog’s clever single-slotted flaps. The Bird Dog, which became very effective during the Vietnam War had a 60-degree flap setting! The flaps, specially designed with internal tracks, were to be a feature of all future strutted-wing single engined Cessna’s. The company’s marketing department loved the new flaps and called them “para lift†implying the 170A would descend like a parachute with full flaps. This caused much amusement and in some cases alarm within the design engineering department as in fact the aeroplane descended more rapidly. Cessna also became puzzled that aviation magazines continually criticized a marked transient nose-up motion when deploying the flaps. It was later discovered that the disciplined Cessna test pilots always applied flaps in a smooth and even upwards motion of the floor-mounted lever. The magazine writers usually applied flaps in a sudden movement by jerking the lever upwards. Nevertheless, the flap system was very successful, permitting a ten-percent shorter takeoff ground run for the 170B.
Over a nine-year production run, Cessna built 5 173 170s and the aeroplane set the stage that enabled Cessna to dominate the four-place market when the 172 was launched in 1956. By 1954, Cessna was already selling its popular 180. The company was planning to use the 180’s fuselage and vertical tail for the new 1956 170C. However, it was found that the empennage would not suit a lesser-powered airframe. Five years earlier, Piper had launched their tri-gear Tri-Pacer and it was apparent to Cessna that sentiment was moving away from taildragger configured light aircraft, especially in the training and personal role. The Tri-Pacer was beginning to score major sales. Initially this was lost on Cessna’s sales people who spotted a nose-gear mock-up in one of the engineering department’s experimental shops as early as 1954. A memo was quickly despatched to senior management and orders came back for the mock-up to be destroyed. Fortunately for Cessna, the installation was quietly dismantled and stowed away for future use. Paradoxically, the following year, management authorised the development of a nosewheel layout for the 170. The mock-up was trundled out immediately enabling Cessna to test fly the first 170 tri-gear a mere two months later on June 12, 1955.
Traditionalists within the design shop grumbled that the new layout gave a much reduced propeller clearance and a reduced cruise speed. However, the ease of landing the tri-gear was obvious and led to the cancellation of the entire 170C launch and the development of the newly-designated model 172
Flying the Cessna 170
For the flight evaluation we used Doug Reeve’s Krugersdorp-based 1953 170B, ZS-LJG. Doug is a great believer in originality as we discovered when testing his Stinson Voyager a few months back. His 170 is as close to a factory finished aeroplane as he could practically make it. Like the Stinson, it has benefited from a recent make-over and LJG is finished in a factory paint scheme. The interior is beautifully finished in leather and a mohair-type trim that extends to the cabin roof.
Over the years, owners have chopped and changed their instrument panels to accommodate extra gauges and instruments so original layouts are rare. LJG is no exception despite Doug’s ongoing efforts to restore a semblance of originality. He has managed to obtain a remanufactured “classic†dashboard moulding which is currently on its way from the USA. The 170 has therefore a plain black metal panel covered in instruments and gauges. It still retains its bar and pole artificial horizon and ribbon DI though.
The 170 was hailed as providing tremendous cabin space when it was launched in 1947, especially for rear seat passengers. However, for front seat occupants, it’s somewhat of a squeeze, especially at shoulder level. The front seats slide all the way back against the rear row and a recessed handhold on top of the panel helps when sliding the seat forward to reach the rudder pedals. The aircraft sits at a considerable angle on the ground so the handhold is vital to lever the seat forward and upwards. The door is then shut with a firm pull and the window opened to at least provide some room to lodge an elbow during the start and taxi.
The engine is a 145hp Continental C-145-2 six-cylinder, forerunner to the more numerous C-300 which went on to power later 170s and early 172s. It starts easily from cold after four or five pushes on the primer knob, roaring into life with a familiar low pitched rumble typical of six-pot Continentals. Allowing the temperatures to come up, the 170 is a honey to taxi, not least because of the superb view over the nose. A feature of its ground ride is the springy steel undercarriage leg, though the original Goodrich brakes are not the most powerful. Many 170s have been modified to accept Cleveland brakes which provide greater stopping power and manoeuvrability when taxiing.
The run-up is made at 1 700rpm and the mixture leaned off for Krugersdorp’s 5 500 feet elevation. After the pre-takeoff checks with 2 notches of flap selected, we lined up on runway 26 and advanced the throttle to full power. An initial but small tendency to swing to the left was easily countered with rudder and as the airspeed indicator comes alive at just under 40mph, the tail lifts. The tail up takeoff is usually adopted on the highveld although some pilots at sea level airfields prefer to keep the tail down, allowing the 170 to fly itself off at just over 55mph. Doug prefers to allow the speed to build to 60 mph before rotating 55mph being used for short field takeoffs. Best rate of climb is 70mph and with two up and full fuel we manage some 600 feet per minute as we head towards the Hekpoort valley.
Cessna 170s have become popular current taildraggers as they are easy to fly and, with all metal construction, relatively inexpensive to operate. The 170 represents perhaps the purest of Cessna’s single engined line in terms of flying qualities. It was immediately apparent that the aeroplane handles beautifully à far more responsive and with greater control harmonisation than the 172. By the early sixties, Cessna’s marketing people had become far more influential, mandating swept tails and rear cabin windows. These changes inevitably had a negative effect on handling even though the 172 remains the world’s safest light aircraft. The 172 is no aerial Ferrari but it has no vices and is easy to handle for inexperienced pilots.
Taildragger pilots tend to be far more adept at using their rudder à they have to be in order to safely handle their aeroplanes on the ground. Although the 170 handles well, with sharp ailerons and overall light control forces, it does require some rudder to complete balanced turns, especially in right-handers. The 170 stalls positively, rolling off to the right at the break with a pronounced nose drop. The roll off is easily countered with opposite rudder and normal stall recovery inputs. With two notches of flap the break comes at 54mph with power off and 58mph clean.
Owners often claim higher cruise speeds than early 172s and Doug flight plans for 110mph at 2 400rpm on cross country trips. At this speed, the aircraft is burning some 7 US gallons an hour. At 7 500 feet this gives a tank dry endurance of five and a half hours and a range of 629 statute miles.
Returning to the circuit, the aircraft is slowed to 100mph the top of the white arc flap operating speed. Doug prefers to wait for 90mph to lessen any stress on the flap mechanism and a single notch is applied on the downwind leg. There’s a marked nose-down attitude change with flap application and the second notch is applied just before turning onto final approach. With the trim set, the approach speed is pegged at 70mph and Doug likes to see 65 over the fence. Cessna always advocated three-point landings, and with plenty of elevator authority the aircraft settles onto the runway, just above the stall at 55mph. The spring steel gear has a distinctive and lively feel to it indicating that those attempting to do “wheeler†tail-high landings will have an interesting time controlling a 170’s bounces unless the speed and technique is absolutely correct. An impressive 40-degrees of flap is available for landing and although pitch control remains fully effective, there may be too much drag in the event of a go-around. With a small crosswind, Doug stopped the 170 short despite the Goodrich brakes and turned off the runway to return to his hangar.
The aircraft remains coveted by its few owners in South Africa where some seven still exist. 170s are considered valuable classics nowadays providing great flying characteristics with easily handled behaviour on the ground. Its popularity when new was reflected in Cessna’s production figures and values continually rise as pilots reacquaint themselves with the skills and pleasures of 170 flying.
Cessna 170B Specifications
Engine 45hp Continental C-145
Propeller McCauley fixed pitch 2-bladeWingspan 6 feet
Empty weight 220lbs
Gross weight 200lbs
Maximum speed 140mph
Cruise speed 110mph
Stall speed 52mph with full flaps
Fuel capacity 37 gallons
Maximum range 692 st miles
Load factor +4.4g 1.76
But I'me still getting use to the landings. Nothing like a Pawnee. Landing with some wind Even crosswind feels easier than with nill wind (doing a 3 pointer) can you guys with ragwings tell me your methods? I would imagine that with extra flap and a balanced tailplane like the "B" would be different again. What is your over the fence speed? Ive been using 55 Knots. How much do you very it for load? Also are they all heavy on the elevator? Ime useing full back trim on the approch so that I dont need two hands to round out. any way I whant to thank all of you for your help I tried to put some pictures into this message but I dont know how.