From The Cockpit – Cessna 210

The 210A of 1961 incorporated some improvements to the landing gear system, which showed up as an early weakness of the aircraft. Following this, the 210B of 1962 came with the IO-470-S engine, MTOW upgrade to 3,000Ib, rear windows and turtleback and tankage upgrade to an optional 84 USG. The sweptback fin, as on the other Cessna siblings, had irrevocably become part of the configuration. The 10cm width expansion of the 210C gave the cabin handsome cross-sectional dimensions of 44in width by 47in height. With the 21OD of 1964 the Centurion name was adopted- also engine power went up to 285bhp by application of the 10-520; weight went up to 3,100lb and with a need to keep stall speed down, the wing had been redesigned to allow greater flap area; from stability considerations, the tail surface areas had also increased.

The first accommodation extension came with the 21OE, which offered a 4 plus 2 seating arrangement, exactly as Piper did for the PA30 Twin Comanche. The drawback, of course, was a loss of baggage volume space, but there is no doubt that the option enhanced the aircraft’s flexibility. The 210 went ‘turbo’ with the F in 1966. Sales had lagged behind expectations though, almost inexplicably so and Cessna was on-going with a product improvement programme to achieve a sales pick up.

Turbocharging certainly did something. The 1966 model T-210F also took on board a three blade prop; gross was up to 3,300Ib. The 21OF fared well, with more than 250 sold during that mc;,del year; further Turbo-Centurions have consistently outsold normally aspirated versions nearly 2:1 since then. The engine on the T-21OF was the Continental TSIO-520C, of 285bhp-Cessna being among the first to employ the type. The standard fuel tankage was simply insufficient for the Turbo-210; the optional 80 gallon tanks were more useful.

Flint wingtip tanks which added a healthy 28 USG to the usable total could also be incorporated by Centurion owners. Perform, the T-210F would-1,280fpm rate of climb, after a takeoff distance of 1,265ft; sub transition altitude, no change in the maximum cruise speed of over 170kts, but high up at FL240, the cruise speed gets up to 190kts. Engine handling with the wastegate-controlled Turbo takes the usual care – opening the throttle too quickly can over-boost the engine (above the rated 32. 5 inches maximum) before the wastegate catches up with the correct exhaust dumping, whilst thermal shocking on descent should be avoided; if required, gear and flaps can also be used to enhance descent rate to some extent, by virtue of the high extension speeds of 139kts for each.

Whilst the T-210 may be definitely applicable in the high density altitudes of the western USA, Australia is ‘hot’ without the ‘high’ and thus purchase of a T-210 needs to be perhaps more carefully considered- ie, is the not inconsiderable turbocharger maintenance bill worth it.

Immediately following the 21OF, in 1967 the 210G went cantilever with 90 US gals as standard fuel and gross weight up to 3,400Ib. The strutless wing maintained the earlier models’ 3° of dihedral. Oddly, Cessna halved the dihedral on the 21OJ of 1969 – merely a ‘cosmetic’ decision, or evidence of a possible wing root fatigue problem associated with the spar kinks, who knows. One thing for certain, the loss of static lateral stability (which was degraded anyway with the more powerful engine slipstreaming over the effective flaps set at 40° deflection) associated with the change, needed compensation and it came in the form of a rudder aileron interconnect. The nosewheel strut was also shortened, unfortunately detracting from the aircraft’s rough field utilisation by virtue of reducing prop clearance to the ground.

Cessna had two more substantial changes in line for the Centurion. Firstly, in 1970 the 21OK came with the IO-520L at 300bhp and 25% bigger cabin, making it a truly six adult aircraft helpfully the gross jumped to 3,800lb. Also, the LG had wider track tube steel gearlegs installed.

Secondly, in 1977 Cessna added to the 21OM model a pressurised Centurion. Being the only pressurised single in production at the time (there were other prototypes and Mooney had been there with the Mustang), Cessna was taking a bold step, but one into a definite market however. The P210 was powered by the TSIO-520-AF, delivering 310bhp at 2,600rpm, hauling a gross of 4,000lb. Performance was no better than the Turbo-Centurion – takeoff and climb performance was in fact down from the earlier turbos simply because of the much greater MTOW, takeoff distance being 610 metres. Cruise speed at FL230 was still 189kts (75% power) but with a 12,100ft cabin altitude due to the P21O’s 3. 35psi pressure differential capability. The pressurisation is bled off the intake manifold downstream of the turbocharger and ducted to the cabin via a flow limiting venturi (operating sonically choked) at about 6Ib per minute. At FL230 and a MAP of 29. 5ins this system takes a calculated 5bhp (1. 5% of maximum power) from the engine.

The P210 on full fuel could carry five passengers without baggage a distance of 820nm (based on the fuel tankage of 329 litres). The Pressurised Centurion has not had much of a market in Australia, there are but a handful on the register; the Stateside market was more productive. For Cessna the introduction of the model was certainly problematic, particularly in systems areas For example-the P210 is a high performance high flier, but in the US seaboard and hinterland areas there is a lot of seasonal ‘high weather’ and the aircraft suffered from a number of post-vac pump failure loss of control accidents; the engine exhaust pipes experienced cracks, which with the attendant possibility of inductive (and cabin) and exhaust gas mixing, necessitated AD action. In its favour however is time – length of service allows problems to be identified and rectified. The high performance pressurised single genre is an advanced and difficult design to take on – Piper’s experience with the Malibu more recently demonstrates this point also. Summarily, if considering the purchase of a turbocharged Centurion for the Australian environment, I suggest that it makes the most sense to combine it with a pressurised cabin.

Concerning older Centurions generally, as regards maintenance perhaps the primary issues are related to the landing gear (LG), which was originally powered by an engine driven hydraulic pump and was quite unreliable. The LG is for its class unique: main landing gear consists of long tubular steel legs pivoted off vertical to retract rearwards into cutouts (without cover for the wheels). The nose landing gear retracting aft, fully covered by side hinged doors. Gear retraction relies upon electro-hydraulic power. The selector provides electric power to the hydraulic powerpack which pressurises the system, resulting in gear in motion via hydraulic actuators. The electric motor is depowered by the action of micros; mechanical downlocks and uplocks maintain gear position whilst the hydraulic pressure retained in the lines keeps the gear doors closed.

The retracted positioning of the main LG rearward along the lower fuselage was actually an ingenious solution to the problem for a high-winged aircraft. Most significant though on the LG is an on-going AD issued in 1976, calling for replacement of the LG saddle every 1,000 hours, due to fatigue cracking experience. The LG actuators were also problematic.

In all likelihood the Centurion you will find on the market will be a 21OK, L or M. Let’s look a bit closer at the 21OK, powered by the 300bhp 10-520: a genuine six seater with power to match. LG and brake operation are the only hydraulic services, flaps are electrically operated via an electric motor in the right wing root. Fuel system is straightforward, with each of the 160 litre usable tanks being individually selectable, fuel being routed from reservoir tanks through the selector, AUX pump, strainer and engine driven fuel pump (EDFP) to the fuel control unit (FCU). Special attention is given to switching design for the AUX pump (dual function switching being provided for START and for EMERG), as AUX pumps can deliver a rich cut to Conty engines.

The electrical system is 28v de, alternator output powering a split bus-primary for flaps, LG control, lights, stall heat etc and electronic bus for radios and avionics. Typical empty weight APS is 1,060kg, allowing 660kg up to the MTOW of 1,720kg, or 430kg with full fuel – enough for six on board with hand baggage only (toothbrush and ‘plastic’).

Flying the Centurion

Cabin size on the Centurion is comfortable for the row 1/2 occupants and adequate for the rear seat passengers. The coaming is high and does present some obstruction to forward vision, particularly on the ground, in spite of the shortened nosegear. As with any older aircraft, earlier models tend to have a hotchpotch of added instruments on an IFR panel.

Engine handling procedures are standard Continental. As previously mentioned the electric AUX pump has two switches START selection schedules one of two fuel flow rates from the pump, depending upon the throttle position (Low with the throttle near closed and higher with the throttle in the cruise power range); the EMERG switch selection provides the greatest pump fuel flow rate and brings ON the START switch via operation of an interlock. The AUX pump must be off for takeoff due to the series combination of fuel pressures from both the AUX pump and EDFP tending to flood and rich cut the engine. This is the same as on other injected Conty installations such as the Bonanza; it would be more reassuring if the system was enginee red so that the standard Lycoming procedure of taking off with the electric pump ON could be followed – thereby preventing an engine failure through failure of the EDFP driveshaft rather than provide a means of restoring power in that event.

Swing on takeoff is noticeable, but readily controllable. Best rate of climb speed in the 21OK is 95kts, cruise climb speed 110kts with 25/2,500 power. 21Os have cowl flaps; recommended climb procedure is cowl flaps OPEN. Level, mean cruise performance is 165kts TAX at 60 litres per hour (65% power schedule). The flight control feel to the 210 is solid and heavy. Takeoff pull force is large, more so for a flapless takeoff (10° being the normal setting) and once airborne attitude changes about all 3 axes requires some effort. It does not matter at all for a cruising aircraft, which the Centurion is; for the most part the heavy controls can be attributed to the state of aerodynamic balancing of the flight control surfaces – additionally however the rudder/aileron interconnect would expectedly add to circuit stiction (breakout forces).

At its heaviest weight the pressurised Centurion has a land flaps stall speed of 58kts; thus approach and landing speeds remain low- on the 21OK in the pattern use 80kts on base, 70 on final, reducing to 65 (all lAS) threshold speed. At this flare speed, final approach power needs to be kept on as the aircraft is levelled – a smooth touchdown on the energy absorbing main gear can then readily be accomplished. Trim change with max power on a go-around with landing flap lowered is substantial – caused by the tailplane positioning in relation to the significant Fowler flap downwash.

As with other aircraft types, the lot prices of used Centurions take a hike on models manufactured in the eighties. A 21OF should be about $50,000, 210Ls of the mid 70s are up at $90- 120,000 and Ns (1979 onwards), $130-200,000. The Cessna 210 airframe has also held an attraction for STC venturers – you may find a Robertson STOL madded aircraft (wing fences, drooped ailerons – a limited use indulgence) but you won’t as yet come across an Allison-powered 210 on the local market, although Soley has tinkered with and continues to develop the concept (what price the maintenance bill in this case).