Airtest – Cessna Grand Caravan

For anyone unused to turboprops, though, starting this whopper is surprisingly simple. Just turn on the master switch, twist the two fuel cocks in the roof (one for each wing tank), switch on the pump and flip the start switch forward. When, after half as many seconds, the whistling rpm reaches 12%, move the condition lever (the little right side red one supplying the engine with fuel) to low idle. Ignition and starter cut out are automatic, and within thirty seconds the prop has smoothly gone from feathered and stationary to a very purposeful thrimming blur, while engine rpm (strictly gas generator rpm or Ng) have smartly risen to a shrill but muted 50%.

Of course you would first have checked the park brake set, prop pitch fine (where it normally stays throughout flight), throttle (more correctly, the power lever) at idle, and standby power lever (the left red knob) closed, but this is all there is to it. A neat row of small engine dials spans the panel top, with twin fuel gauges at the right and torque (or power and therefore the most important one) on the left, in the edge of your scan. During start the Inter Turbine Temperature (ITT) should not exceed 1000°C, but rarely rises above 750, and prop rpm stabilises at a low 950.

Although more the size of a cabin twin’s, the roomy cockpit layout is also simple. Primary switches are on a small horizontal panel atop the tall left sidewall circuit breaker box, with lighting and green deicing switches in two neat groups below the control yoke and an enunciator panel ahead of you. Instruments and King radios are just like any other Cessna’s (except for inclusion of colour radar and an optional second set of right side dials) although the gated flap lever (wisely marked with the easily remembered limit speeds of 175 [325km/h] for 10°, 150 [278] for 20 and 125kt [230] for full), and its pin in a slot indicator are on the curved central console. The only oddity is an umbrella handle protruding from the panel above your right knee. Twisting and heaving it opens the engine intake particle separator, causing water, dust or other undesirable detritus to zip straight aft out of the left side cowling, rather than negotiate the serpentine intake duct into the compressor at the engine’s rear. Mandatory in icing conditions, its use causes only a two per cent power penalty. Looking ahead through the enormous, sloping, low sided windscreen returns that feeling of grandeur with a rush. Releasing the brakes and inching the power lever forward coaxes a satisfying roar from the propeller as its coarsening blades grab the air. Lowly lightplanes seem mere toys from this lofty eyrie as you look down onto the tops of their wings and pick your way among them, being careful not to blow any away. The Caravan’s slightly ponderous steering accentuates the impression of size, a slight lag and rather indirect feeling reminding of the four tonne mass following (although turns can be made remarkably tightly with a little help from the gently powerful brakes). Although the wings span nearly 16m, they are so far above most obstructions as to present no problems, although the right tip is obscured by the radome at its strut junction. The strong cantilevered gear legs impart a slightly rolling gait as they and the nose leg flex on uneven ground, but they absorb potholes extremely well.

Pre takeoff checks are simple as the pre start ones, including standby electrics, anti icing, overspeed governor test, condition lever to high idle (65% Ng) and flaps set at 20. As we swung on to the runway a feeling of gravity crept up on me as my mentor, surgeon turned ferry and demonstration pilot Guy Rosenschein switched on the no smoking and seat belt signs. Turning, I absorbed the looks of careful appraisal by the earnest faces of a half dozen non flying journalists in the eight seats behind us.

With a ten knot (19km/h) crosswind and a big engine, I was slightly surprised that keeping straight required absolutely no effort thanks to the powerplant’s noticeable down and right offset. Control was very easy using nose wheel steering and the slightly heavy servo tab assisted and spoiler augmented aileron system chosen for good low speed handling. The rotation speed of 80kt (150km/h) came after just 20 seconds, representing an acceleration better than many sports cars. A later short takeoff at 70kt (130km/h) took 13 seconds for a less than four hundred metre roll.

Immediately in the air, the Caravan shrank to feel like any smaller Cessna, with good control, quite excellent visibility and a steady, solid feel despite the convective bumps. The flaps came up promptly with just a slight sink as the last few degrees retracted, the consequent pitch change quickly neu- tralised with the neat optional yoke mounted switch. There are useful trim wheels for each of the three axes down below the central console, and they were all needed from time to time because big trim changes. Inevitably accompany the Caravan’s high power and broad speed range.

The published best climb angle is at ninety knots (168km/h), best rate at 100 (185) and cruise climb at 120 (222), but you can take your pick because it goes up like a lift at all these speeds. With eight aboard and 800kg of fuel, we weighed 3700kg of an allowable 3970, yet in a temperature of 19°C were level at 7000ft (2135m) within just six minutes of takeoff using max continuous power.

Although there are four engine levers on the quadrant, this is effectively a one control powerplant, because the right engine condition knob lives in high idle throughout flight and the prop setting can stay at 1900rpm. Lower revs change the sound of the engine, but not its volume (which was quiet The Caravan also comes in a floatplane model to ensure if is able to in time take over from those denizens of the utility world, the Beaver, Otter and Twin Otter.

enough to make headsets unnecessary) and would only be used if trying to squeeze the full seven hours endurance out of the tanks. In fact, other than inching it forward in the climb to maintain max continuous torque, even the power lever stays in the 1800ft/lbs (250m/kg) position for cruise, which wound up to 160kt (296km/h)IASatafuel flow around 180kg (400lb)/hr (equating to 178kt [330km/h] TAS and close to the book figure of 182kt (337) at 10,000ft [3050m], giving a range of 900nm [1668km) plus).

There is no vibration in the grey vinyl floored and light blue fabric walled cabin and sound level is even lower than in the cockpit. Although engine noise is inevitably significant throughout, it is less than in an unpressurised twin and a call from the cockpit can be heard 5m aft in the baggage area. Having entered this pleasant environment up their own three tread air stairs through an easily opened up and down split door aft of the right wing, passengers walk forward in a half crouch along a 1. 2m central aisle to comfortable individual seats with lap and diagonal belts and an eye level window apiece. Their view is excellent, and each has a ceiling air vent and light in the soft white PVC headliner. Connoisseurs quickly learn the aft most seats are quietest with the best view but, unless they are particularly observant, most customers honestly don’t notice the single engine.

Traditionally many airworthiness authorities have prohibited commercial IFR passenger operations in such aircraft, but the Caravan family has caused a worldwide re think. The important considerations are: how likely is powerplant failure, and what recourse is there should it happen? With a twin, particularly a piston twin, engine failure is at least twice as likely, while recovery to a safe landing demands particular and practised skills. On the other hand, the Caravan has big tanks, a simple fuel system and a remarkably reliable PT-6 engine with the phenomenally low published inflight shutdown rate of once per 500,000 flights.

If the engine does stop, from a normal 10,000ft (3050m) cruise the aeroplane can glide 22nm (40km), allowing nearly 15 minutes to try and sort out the problem. Modem GPS nav kit allows an immediate turn towards the nearest airfield or ALA (no matter how small, the ‘Van can hack it) and, if there is really nothing within range, its big flaps, low stall speed, excellent low speed handling, high fuselage and strong undercarriage make a forced landing as predictably safe as in any Cub.

Because this level of safety approaches that of most twins, several airworthiness authorities have revised their legislation in the eight years since the Caravan started work. In February 1993 Canada approved commercial single engined IFR and night passenger flights, provided the turbine engine is original equipment, the aircraft has adequate systems redundancy and proven reliability, and the operator has six months experience. FAR part 23 allows VFR and IFR freight flight by day and night (and in icing, with the appropriate equipment), seven EC countries (Norway, Sweden, Denmark, Finland, France, Portugal and Eire) permit single engine IFR cargo operations, and the imminent JAR Ops regulations are expected to address the subject of passenger operations.

Having arranged airworthiness certification, Cessna will support operators in their application for approval.

In view of this, I investigated the machine’s glide, feathering the prop (which can be done with the turbine still burning) and watching it slowly windmill as we very gently descended at ninety knots and 700fpm in complete control and eerie quietness (but with a surprisingly high left rudder load). Bored with the ease of this, after a few minutes we unfeathered the prop to try the standby power lever. The main cause of PT-6 unserviceability is not mechanical failure, but this emergency system bypasses the FCU’s normal pneu- a Fuel Control Unit (FCU) or P3 bleed air filter problem-thus matic signalling with a straight mechanical linkage to the fuel valve. With no limitations, it is simply less sophisticated and rather coarse, smaller lever movement being needed for a given power change (and spool up taking a little longer on starting).

An optional standby 75 amp alternator automatically cuts in should the main 200 amp starter generator fail and, although the flight instruments’ vacuum comes from a very reliable bleed air ejector, the electrical ones on the copilot’s panel provide backup and of course there are two complete pitot/static systems plus an alternate flap motor. All this gives remarkable systems redundancy in such a simple aeroplane. Forthose still unconvinced, Soloy is experimenting with their Dual Pac two engines driving one prop system, in which Cessna is not involved.

Returning to the handling, the adage that big aeroplanes are often easier to fly is very relevant to the Caravan. Although its roll rate is a bit ponderous, the ailerons (and spoilers) call for some muscle, and a fair pull force is needed at over 30° of bank, it is still surprisingly manoeuvrable and extremely stable, needing a big disturbance to deviate it from its original direction.

Its stalling manners are exemplary too. Clean, at a little over 3600kg (8000lb), the horn sounded at 75kt (140km/h) IAS and, after the NACA 2300 section’s expected minimal buffet, the nose dropped through 10° straight ahead at seventy (130). Ten degrees of flap depressed horn speed to 71 (132) and the break (with a slight right wing drop) to 65 (120), while full (thirty degrees) flap induced more buffet and lowered the stall to 55 (101km/h) IAS as the right wing fell away 10″. In fine pitch the big prop caused noticeable deceleration, especially with full flap, but conversely soon powered us out of the stall regime.

Flying a 120kt (222km/h) ILS with 1000ft/lb (138m/kg) power in this stable machine was simplicity itself and, after overcoming the pitch-up caused by flap extension, the 80kt (150km/h) approach and landing were equally easy despite a 50°, 15 gusting 20kt (37km/h) crosswind. Although response was slightly more ponderous at lower speeds, the elevated seating position did not seem to affect flare judgment, maybe because everything else about this aircraft is in proportion. Rolling to a halt without brakes or reverse took perhaps 500m. A subsequent short landing using full flap, 500ft/lb (69m/kg) for 70kt (130km/h), full reverse and hard braking resulted in a satisfyingly quick 250m stop after a touchdown during which, partly thanks to an unexpected gust, the undercarriage passed the Grimstead energy absorption test. Shutdown after the flight was as quick and easy as startup.

With a disposable load of 1733kg, this versatile aeroplane will carry up to 713kg payload (or seven passengers with baggage) and full fuel for a 900nm (1667km) range with 45 minutes reserve at max cruise speed. Alternatively, it will take 1400kg of load on a shorter 200nm sector. For maritime surveillance or military use (as the U-27A) it can loiter a hundred nautical miles from base for six hours at 90kt (168km/h) and 5000ft (1525m).

Airliner type Brownline floor tracking (for securing either seats, freight or cargo nets) is standard and can be recessed below plywood flooring to ease sliding packages. Wide CofG limits present no problems when carrying passengers and, in cargo configuration, the 12m3 cabin is divided into six clearly marked zones for easy freight distribution (with a tail support for the cautious). The flat, 112cm high floor takes up to 90kg per sq ft, is at truck bed level and, being horizontal, is simply loaded by fork lift, demanding no uphill struggling. The aircraft can fly with the 1. 2m square left side freight door removed, and the demonstrator’s underbelly cargo pod op- tion, holding up to 495kg in its 3. 15m3, is loaded through four left side composite doors.

Over 600 Caravans and Cargomasters of the six sub species have been delivered to date, including over 250 to Federal Express alone. The highest time airframe has accumulated 9000hrs and another amasses 300hrs monthly. Well over 1. 2 million total fleet flying hours in nine years displays a quite remarkable 99. 9% despatch reliability for a single engined aircraft and attests to its sound and robust design. Using pilot logged engine data on every sixth flight coupled with operator experience, Cessna has built up a record of technical problems and so can make a very accurate prediction of operating costs. Some FedEx operators have improved their PT6s’ TBO (Time Between Overhaul) from the already impressive 3500hrs to 5500 and expect 6000hrs, while other operators can extend life in 500hr increments (with the 1250hr hot end inspection becoming ‘on condition’) if they use this programme. The Caravan’s PT6A-114 has a single combined exhaust to reduce belly staining and easily accessible accessories. The wide opening cowlings come off in ten minutes, while compressor washing and hot end inspections can be accomplished in situ. Its battery tray swings out for quick disconnection and removal (for overnight charging, warming or aircraft security) and the exciter box bracket has provision for carriage of a spare.

The rugged, 3. 65m track, tubular spring main landing gear legs carry big 8. 50 by 10 tyres and pivot on a stainless steel cross tube with flexible rubber fairings allowing movement in all planes. The nose leg’s extra 8cm extension gives 35cm prop clearance, its coiled spring has unpressurised oil damping and, like the main legs, flexes fore and aft, using a 172RG main gear leg spring as its drag link.

The big 26m2 wing has a high 9. 6 aspect ratio. Its optional pneumatic leading edge and strut deicing complements the electrical prop and windscreen and pitot heat. Fuel is stored between main and aft spars inboard of the outer flap hinges, and the spliced outer 1. 8m can be replaced without jigs in the field in the event of damage. The wide Fowler flaps span 70% of the wing and increase its area by 15%, their outboard portions having unusual rubber vortex generators to keep the flow attached for the FAA required single engine aircraft’s 61kt (113km/h) stall speed. Unusually there are also vortex generators above the tailplane, and all flying controls are operated by stainless steel cables and torque tubes.

When you consider its ability to land at any small airstrip (which might be much nearer to an intended destination than any business jet’s airport) it is perhaps not entirely surprising that the executive version is becoming increasingly popular, with over 30 sold so far. The Caravan’s ageing conventionalĺ competition of Islanders, Otters and Twin Otters (especially on floats), are more costly to operate and this Grand ‘Van can carry more load in and out without refuelling than a Twotter. The million dollar Grand Caravan lifts 18% more than the earlier model for a 9% higher price (and only 2% greater running cost) but, while most buyers now opt for the larger machine, parachutists still prefer the earlier model because they can cram all fourteen permitted (temporary) occupants into its smaller airframe and climb to 12,000ft in nine minutes as its lower flat rated power is retained to a higher altitude. six months lead time for a specific order. As with their Customer demand is such that there is now approximately Citations, for safety Cessna provide Caravan purchasers with training, including ground school, 5. 5hrs in a cockpit procedures trainer, 5. 5hrs simulator time and 2. 5 flying hours. They proudly point out that the fleet has had no incidents since introducing this simulator training in 1990.

In America the word ‘Caravan’ does not evoke our conno- tation of a nasty tin and hardboard mobile road obstruction. There it implies a heavy duty international trader, conjuring slightly exotic visions of Marakesh, Samarkand and the an-engined Jumbo with the ruggedness, flexibility, reliability and cient mysteries of the oriental silk trade route. Here is a single load carrying capacity to rival the camel of old.

predictable, rock steady, sophisticated yet rugged advanced This big, powerful, simple, efficient, stable, manoeuvrable, STOL plane turned out to be my kind of aeroplane.