By me
All photos me too, copyrighted
It is perhaps a sign of the state of general aviation on the Balkans that the arrival of a single Cessna Caravan can stir up so much interest that even people from neighboring countries head over to see it. While a perfectly common “garden variety” airplane everywhere else, the 208 is still a pretty exotic beast in these parts, with myself having come across only four examples in the 16 years I’ve spent hanging around light aircraft. Therefore I could be excused for packing up my photo gear and driving 120 km one way to Šentvid Airfield in Slovenia in order to catch it 😀 .
The machine in my sights, however, had a bit more going for it than just being a big Cessna with a turbine. On the one hand, it is a comparatively rare short-body Caravan I – and on the other it sports the impressive Blackhawk XP42 engine conversion that is not that common even in the more affluent bits of Europe. So as it spent its three days there hauling skydivers to altitude, I could take my sweet time and get to know it Achtung, Skyhawk! style 🙂 .
A handful of horses in the back – and 850 charging straight at me. Looking imposing in the soft afternoon light, D-FOXY returns from yet another series of skydive runs. Manufactured in 1999 with the serial 208-00303, Foxy spent its early years in the US, flying as a seaplane under the name N984J. In 2006 it would move to Italy as I-SEAA, before heading north into Germany in 2013, where it would eventually lose its floats, get buff and become a no-nonsense jump platform
Blackhawk Up
Though much can be said about the qualities and exploits of the rugged Caravan, what interested me most in this case was in fact Foxy’s nose job. One of the many products to come out of the Blackhawk Engineering works – the people who put third-party turboprop upgrades on the map – the XP42 mod involves replacing the 208’s standard engine (in this instance a “small series” 675 HP PT6A-114A*) with a much more potent “medium series” 850 HP PT6A-42A. In addition to the improved power, the 42’s larger core also noticeably adds to the torque, with take-off figures now up from 2,535 to 3,045 Nm. To soak all this up, the original three-blade 2.69 m McCauley prop gives way to a variety of four- and five-blade aluminum and composite units, with Foxy in particular sporting a conventional 2.54 m Hartzell for a bit of extra ground clearance.
* up until serial number 208-00276, most short-body Caravans were powered by the 600 HP PT6A-114 unit. From aircraft 277 onward, they switched to the same 114A as used by the bigger Grand Caravan. Also of note is PW&C’s engine class system: “small series” engines develop between 500 and 900 HP, “medium series” cover the 850-1,050 range – while “large series” go from 750 all the way to 1,900.
But, the XP42 upgrade is as much about added grunt as it is about the nature of its delivery. Unlike a simple engine swap, this conversion is what’s called a “firewall forward solution”, which includes – where necessary – extensive modification to the engine compartment itself in order to get the most out of the new powerplant. Since the majority of XP42s will be used for rough-and-tough hauling in arduous conditions, the folks at Blackhawk had gone to some length to make the upgrade more than just a course of steroids. To this end, the most obvious alteration is to the cowl, now widened at the front to accommodate a 40% larger oil cooler in order to keep things in the green even during operations in hot-and-high conditions or repeated back-to-back flight cycles. The new twin exhaust stacks (a consequence of the 42’s slightly different architecture) can be profiled to either eek more thrust out of the exhaust gasses (5 knots worth in fact) – or increase mass flow at the expense of cruising efficiency to lower turbine temperatures during the type of prolonged high-power climb common to skydive ops.
For comparison, a stock Caravan I, here in its military U-27 guise. Note the single large exhaust duct and narrow cowl
Other stuff? Well, the engine is now mounted at four points instead of three, there’s an improved air intake system with a modified inertial separator to further reduce the likelihood of foreign object ingestion at rough strips, the battery is now a Li-ion affair instead of lead/acid to save roughly 13 kg in weight – and there’s an optional 325 A starter generator instead of the stock 200 A unit to reduce wear and tear on the engine by shortening spool up and light up times. The package is also rounded up by custom Hawkeye engine gauges, generally similar to the Caravan’s originals – but now with an additional digital readout for most parameters.
Dear passengers, your flight is now ready for boarding. Though all of you will leave half way, we would like to thank you for flying with us! Though the prop is now noticeably shorter in span, it still spins at very similar speeds as the original, meaning the XP42 is still a pretty quiet machine, even at full chat
A peek under Foxy’s skirt. Though the 42A sports a larger core than the 114A, it is only 27 kg heavier dry, 190 vs 163 kg. Interestingly, it is also 34,7 cm longer than the 114A (1.68 vs 1.34 m) – but at the same time 13.2 cm narrower, sporting a 46.4 cm diameter vs the “smaller engine’s” 59.6. Also note the fuel/oil heat exchanger at the extreme right, which helps cool the oil by transferring some of its heat to the fuel on its way to the combustion chamber
And the conversion’s other party piece, the new oil cooler. A pretty good illustration why the XP42’s nose now looks like it had been rammed into a wall!
In addition to Blackhawk’s efforts to keep oil temperatures manageable even during repeated short cycles (as well as the day’s very agreeable 17 degrees Centigrade on the ground), Foxy came equipped with a custom cooling adapter, essentially three fans running off a 12 volt external battery that circulate air through the oil cooler to prevent the formation of local hot spots when the engine is not operating
With a load of between 10 and 15 skydivers every 15-20 minutes, Foxy’s modification sure had their work cut out for them (even more so since start-ups are more critical to turbine engine wear than running hours)!
What a truly wonderful way of spending an afternoon: sitting on the ground behind a revving 850 HP short-body Caravan to the background of rolling hills and lush forest…
As always, I would like to thank the very friendly staff at Šentvid Airfield – as well as Foxy’s pilot for allowing me to snoop around the aircraft inside & out!
Sources:
- Avbuyer – Blackhawk Modifications profile
- Blackhawk Modifications – Cessna Caravan Vx Upgrade and XP42 article
- EASA – Cessna 208, PT6A-100 series and PT6A-41 series Type Certificate Data Sheets (PDF)
- Pratt & Whitney Canada – PT6A family overview
- Seaplane Magazine – Caravan MT Propeller article
Achtung, Skyhawk! 