Flying Blackhawk's 850 HP Caravan - Blackhawk Modifications, Inc.

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Going Up, Fast We climbed into the cockpit, pulled up the boarding ladders and went through the routine PT6A starting procedure; master on and fuel pump to normal, engage start switch and watch rotation begin on the Ng gauge, waiting for 15% Ng to introduce fuel. The lightoff and rise in rpm caused no more than a 750 C. indication on the ITT (start limit is 975 C). Once stabilized, we confirmed that the starter had been switched into generator mode and the avionics were flipped on. The cooperative Hartford, Connecticut tower offered to arrange for VFR flight following service as we exited their airspace to the east; Dunkin’s plan was to execute a max-performance climbout above Providence’s Class C environment. We quickly taxied to runway 21 for a prop governor test and advanced to high idle condition, extended ten degrees of flap and took the inertial separator handle out of “bypass” position. With the APE kit, extreme short-field takeoffs are approved with 30 degrees of flap, versus 20 degrees for an unmodified airplane. Preferred Airparts Quarter Page 4/C Ad The propeller wound up to 2000 rpm while we held the brakes, and we advanced the power lever to about 2150 pounds of torque on the roll. The torque built to 2200 as we lifted off at a leisurely 80 knots, halfway down the 4400-foot runway. Once past 95 knots, the flaps were brought up and I quickly accelerated the aircraft to 120 knots. Dunkin advised me to hold 115 in the climb; by doing so, visibility over the nose was nil. The VSI read 2000 fpm initially, finally settling in at 1600 to 1700 fpm. Blackhawk’s brochure says the XP42A has double the climb rate of a standard Caravan, and when we compared numbers with the standard and modified charts, it appeared to be true; under similar conditions, a 675-hp 208B would manage around 850 fpm. With torque tweaked occasionally to keep 2200 pounds pulling us upward, the ITT started out at 730 degrees C. and rose to no more than 750 at the top of our climb, 11,500 MSL. Only about 8 minutes had elapsed since our sea-level liftoff. The -42A Pratt had kept its 2200 pounds of torque until 10,500 feet. Temperature was about 16 degrees over standard ISA and takeoff weight was estimated at 7700 pounds. As we leveled off with 2100 pounds of torque and 750 degrees on the ITT, the airspeed settled at 165 knots IAS, computing to a TAS of 202, while burning 460 PPH of Jet-A. The standard 208B’s book showed that only 1370 pounds of torque would have been available at 12,000 feet, providing a TAS of about 158 knots. In all fairness, Dunkin pointed out, our TAS would have been ten knots or so less if we had been at full gross weight. Great Lakes Aero Products Quarter Page 4/C Ad DECEMBER 2011 TWIN & TURBINE 21
With power reduced to 1900 pounds torque, we lost about 10 knots of speed, cutting fuel flow to 400 PPH. Dunkin then demonstrated a quiet-cruise mode by backing away a bit of torque and slowing the propeller rpm to 1700, bringing torque back up to 2200 pounds, but in a much quieter environment for the passengers. Handling at cruise remained trucklike but benign, just as the Caravan has always been. We experimented with slowflight at 80 knots and full flaps, which turned out to be a thoroughly honest bit of flying, simply lighter on the control feel but still ponderous in response. We did not essay a full stall, but Dunkin assured us that nothing has changed over the simple Skyhawk manners we have come to expect in the 208. Because the FAA insisted on duplicating the certification criteria, a complete spin program has been flown, comprising some 115 spins. Going Down, Fast Because one of the major markets for the XP42A mod is for skydiving centers, we experimented with the skydive descent at flight idle, pushing over to reach the 180- knot redline. With the VSI pegged solid at 3000 fpm down, we timed an eardrum-splitting 4000 fpm descent, then quickly resumed a 500 fpm letdown. Combining the improved climb rate and rapid descent, skydive centers will be able to take four loads per hour to the top of the non-oxygen altitudes. Cleared to land back at Hartford’s Brainard airport, we slowed to 175 knots, where ten degrees flap was permitted, which reduced speed to 150 knots so we could extend twenty degrees of flap. The final flap limit is 125 knots. A defunct set of runways a few miles east of the airport, the former Rentschler Field from World War II, tempted us, but, fortunately, Dunkin caught my mistake before it became serious. Cessna avoiding any equivalentlevel-of-safety games when certifying its big single under FAR Part 23, preferring to meet the 61-knot Vso stall speed limitation with pure aerodynamic wizardry, at least at the standard airplane’s 8,500-pound landing weight. As with all Caravans, approach and landing chores are simple; no landing gear to extend, no switches to throw, just slow to as little 80 knots and drive to the runway. We indulged in a 90-knot “high-speed” 22 TWIN & TURBINE DECEMBER 2011
Page 1 and 2: Flying Blackhawk’s Car By LeRoy C
Page 3 and 4: logged in Blackhawk’s recertifica
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Flying Blackhawk's 850 HP Caravan - Blackhawk Modifications, Inc.

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