A qualitative (‘qual eval’) was conducted on a flight from Comair at Lanseria.Taxiing to runway 06L, with a relatively wide 3,55m wheel track, was smooth and despite a 10 and 12 knot crosswind. Directional control required no special attention from the pilot.
On a 24 degrees centigrade afternoon (ISA + 17 degrees centigrade), a pressure altitude of 4367 feet (density altitude 6600 feet), a takeoff weight of approximately 3402 kilograms, the aircraft quickly accelerated to the rotation speed of 70 knots, and lifted off at approximately 87 KIAS after approximately 510 metres, passing overhead an imaginary 17m obstacle at 90 KIAS covering a ground distance of 628 metres. Despite the 192 shp increase and quick-responding turbine power plant, directional control was easily maintained during takeoff and initial climb.
Established at the recommended cruise climb airspeed of 115 KIAS, (Vy=92KIAS), a “spot check” of excess shp was conducted through a 3000-foot “height slice” from 6500 feet to 9500 feet. With the prevailing atmospheric conditions at an average ISA+12 degrees centigrade, torque at 2137 lbs/1873 rpm (97,2% N1) ,an average rate of climb exceeding 1000ft/min was maintained up to 9500 feet; the climb time recorded was exactly 3 minutes.
Assessing the level cruise performance, two stabilized points were flown at 9500 feet, one at 1865 lbs torque / 1750 rpm/387 lbs/hr fuel consumption. At ISA+11 degrees centigrade ,true airspeed of 173 KTAS and 164 KTAS were measured which implies ranges of approximately 934 nm and approximately 1000 nm respectively, without reserves. Cessna’s POH predictions for range at 10000 feet, maximum cruise plus 45 minutes reserve, is 832nm.
The flying qualities of the Caravan were evaluated in the cruise configuration at 7500 feet pressure altitude,1865 feet/lbs 1750 rpm/145 KIAS .Longitudinal stability, both static and dynamic, was evaluated by assessing the phugoid and short period pitching oscillation damping.
In both cases, as would be expected from this class of aircraft, the Phugoid period of 35 seconds was positively damped with half amplitude within two cycles while short period damping, as was to be expected ,was nearly a periodic, that is approaching “deadbeat” motion, with no tendency to overshoot.
As a result, the implication in terms of handling and flying qualities was that the aircraft, under those conditions, would be easily controllable in pitch due to predictable response to pilot or atmospheric turbulence input, particularly important for an aircraft that will be flown many hours a day in all sorts of weather. Even at the relatively forward CoG .position, the pitch control was comfortably responsive.
The aircraft was easily trimmed in cruise while all dynamic motions were relatively slow and well behaved. Turns made with aileron only exhibited very little adverse yaw, and the Dutch Roll damped naturally in just three cycles with a short time to half amplitude.
Spiral stability, the tendency of an aircraft to diverge into a spiral if one wing is banked slightly, was essentially neutral which, in theory, implied that the aircraft could be left unattended in bank for at least 30 seconds or more without concern that it would be in a graveyard spiral when attention was redirected to bank and heading.
In addition, small corrections in bank or heading could be made easily using only the rudder, a useful characteristic if the single pilot’s hands were occupied with map handling or writing.
Roll authority was good, particularly for an aircraft the size of the Caravan. With nearly full aileron deflection at 145 KIAS, the aircraft exhibited a roll rate of approximately 30 degrees/second with only moderate adverse aileron yaw, thus demonstrating the effectiveness of the spoilers in roll control.
The stall characteristics were evaluated at a weight of about 3310kilograms.More than regulatory stall warning was provided between nine and 12KIAS above stall speed with mild buffet onset followed by a generally uneventful stall. Stall speeds in all three configurations tested were 67 KIAS (cruise configuration), 66 KIAS (approach flap) and 62 KIAS in the landing configuration. The average height required for recovery, was typically 250feet.
The Caravan demonstrated positive handling during the approach to the stall and at the stall with no uncommanded wing drop. The ailerons remained effective at the stall speed and did not produce a wing drop. The rudders also were effective in raising the low wing at the stall, which was preceded by a mild aerodynamic buffet.
With a 12-knot crosswind on takeoff, and in preparation for the landing, steady heading side slips were conducted in the landing configuration at 85 KIAS to determine typical crosswind handing characteristics.
Using the compass as an indirect method of determining side slip, approximately 19 degrees of side slip was generated by the rudder which theoretically implied that it would be possible to deal with a crosswind of approximately 29 knots versus Cessna’s demonstrated maximum crosswind limit of 20 degrees. The advantage of the high wing, of course, allows a lot more crosswind capability.
Handling in the circuit was relatively easy, with light control forces, good field of view, and energy management facilitated by the flap extension speed for takeoff and approach at 150 KIAS enabling 15 degrees of flap to be selected and to be used for effective energy management.
Landing back on runway 06 from a high downwind (6000 ft) and a quick turn in ahead of a commercial airliner inbound on long finals, provided the ideal opportunity to assess the handling qualities in a “tactical approach” and landing. The combination of relatively large propeller and powerful engine, combined with a predictable response to pilot input, provided effective and easily usable control over the glide path and center line.
The flaps provided the desired lift-to-drag characteristics for the nominal approach speed and elevator authority was adequate, even at the forward CoG .While the 10 knot crosswind presented no problems in directional control.
Unfortunately, there was no opportunity to evaluate the decelerating effects of the-21 degrees reverse thrust blade angle due to the requirement to clear the runway for inbound landing traffic on finals.
First impressions of the cockpit were that the avionics engineers had designed an uncluttered, attention-grabbing instrument panel powered by the all-glass Garmin G1000 avionics suite. This Garmin G1000 glass cockpit included three configurable 10-inch liquid crystal display, large format high resolution screens, one multifunction display (MFD) flanked by two primary flight displays (PFD) which integrated all primary flight, engine and sensor data to provide intuitive, at-a-glance situational awareness.
Flight critical data were displayed on the PFD, including traffic, topographic and relative terrain, digital attitude and heading, engine and airframe indications and crew alerting. In order to detect and avoid inclement weather, the G1000 glass cockpit also integrated the Garmin GWX 68 airborne colour weather radar via a 12-inch phased array antenna for weather detection ranges up to 305nm.The system included fully integrated transponder and dual Nav/Comm/GPS.
At eye level, the digital Garmin GFC 700 fully integrated flight control system provided innovative features including airspeed hold, over-speed protection, pitch hold and coupled VNAV,providing precise lateral and vertical guidance, traditionally only available to larger corporate aircraft and commercial airliners.
The layout was intuitive and the immediate impression was that the design goal was to maximize situational awareness for single pilot operations with the view to enhancing safety for single pilot operation.
The system allows pilots to load IFR flight plans on the G1000 to exactly match the intended route. Magenta rectangular pathways provided a visual window to guide pilots to follow the intended flight route. Pathways were spaced no more than 1000 metres apart and guidelines were provided in each corner that pointed in the direction of the active flight plan leg.
Although the Synthetic Vision capability existed, it was not assessed ,but with the obstacle data base providing the pilot with the existence of non-terrain structural hazards, this would, of course, hugely reduce pilot workloads and facilitate safety of flight in the less structured African airspace.
Other features included digital audio controllers, dual digital air data computers, and dual tri-axial magnetometers digital integrated autopilot to provide the pilot with enhanced capabilities, all of which brings new levels of safety and confidence for operations, particular within Africa’s Spartan navigational airspace.
Pilots operating within the African navigational airspace, particularly north of the RSA border, are fully aware of the challenges facing safe operations and generally poor situational awareness often due to limited navigational facilities. Through the provision of an integrated flight management system, the Caravan EX contributes significantly to situational awareness which will go a long away to improving safety of operations.