AOPA PILOT 58. JANUARY 1996

The thought of getting his hands on a flyable T-34C had intrigued Nogle for AOPA PILOT· 60. JANUARY 1996 The vertical stabll1zer was borrowed from a Travel Air, while the wing was built from Baron spars and Bonanza leading edges. some time. Unfortunately, the Navy was not releasing any of the turbine-pow- ered airplanes. In fact, rumor had it that the brass had agreed to a request from Beech to keep them off the open mar- ket. Along with a partner, Nogle decided to transform a T-34A into a turboprop, and the result is the Allison-powered AT-34. The partners originally intended the aircraft as a sales demonstrator, hoping to drum up modification busi- ness. It made several trips through South America, where it was showcased to those foreign militaries operating Model 45 Mentors. Eight years and two engine upgrades later, the AT-34 remains the sole exam- ple of its kind. With no success in the foreign military market, it is now leased to the Allison Engine Company, which uses the AT-34 to impress other piston aircraft owners with the performance benefits of turbine power. But sales success and design success are two very different animals. Nine hundred pounds lighter than the T-34C, the AT-34 is a screamer. Flat-rated from 495 shp to 450 shp, the Allison 250 B17F has two more oil injector ports than the standard engine, which give it a 30-sec- ond inverted flight capability. At a mere 205 pounds, the Allison engine is signif- icantly lighter than the 225-hp Conti- nental it replaced. To keep CG limits the same, the firewall was moved two feet forward. The resulting elongated nose section creates a sleeker look and pro- vides room for an additional baggage compartment. The space can also be fit- ted with a removable smoke system for airshow work. Larger wing bladders increase the standard fuel capacity from 50 to 80 gal- lons. Removable 20-gallon Osborne tip tanks boost total fuel capacity to 120 gallons, of which 114 (764 pounds) is usable. Aerobatics are not approved with fuel in the tip tanks. The AT-34 owes much to other branches of the Beech family tree. The gear assembly is from the A36 Bonanza and is a stronger design than that of the original Mentor. The vertical stabilizer, transplanted from a Travel Air, lends a less angular appearance to the tail feathers. The wing is a hybrid, made from Baron main wing spars and A36 Bonanza leading edges, with slightly thicker skin than the original. Otherwise, not much else on the out- side distinguishes the AT-34 from its more mainstream contemporaries. Inside, the battleship-gray cockpit is strictly utilitarian, befitting for a mili- tary trainer of this vintage. Front and rear instrument panels have been refur- bished with modern flight instruments, along with necessary turbine engine instruments. Two sets of duplicate con~ dition levers and power levers are nes- tled in control quadrants on the left sidewall, close to the gear and flap con- trols. Located just a few inches below these are aileron, elevator, and rudder trim wheels. The arrangement makes for minimum fuss when changing speeds and configurations, a plus in an airplane expected to fulfill formation, aerobatic, and instrument training roles. The aircraft is unpressurized, but diluter demand oxygen regulators are installed for high-altitude flight. Under Jud Nogle's watchful eye, I per- formed the Allison's straightforward starting drill. Battery On, starter On, and monitor Nj as the engine winds up. At 15 percent N l' push the condition lever to full forward and watch the Tur- bine Outlet Temperature (TOT) rise and stabilize, the indication of a successful light-off. Then it's starter Off and gener- ator On. Taxiing is an easy matter but requires a deft touch on the power controls. The aircraft wants to accelerate even at idle, but an occasional tug of the power lever (throttle for die-hard piston pilots) into the Beta range reverses the propeller just enough to slow things down with- out resorting to brakes. The AT-34's impatient behavior on the taxiway forewarns of its takeoff and flight performance. I had barely set takeoff power before the airspeed reached the rotation speed of 60 knots. On the humid, 85-degree-Fahrenheit afternoon when we flew the airplane, the rate of climb settled on 2,800 feet per minute as we left the pattern at 80 knots, weighing about 2,700 pounds-700 pounds below the AT-34's 3,400-pound maximum. I was told to plan on applying serious amounts of right rudder in the climb, and the torque from the big three-blade prop didn't disappoint. With the nose lowered to maintain a 120-knot cruise climb, the VSI still showed better than 1,500 fpm as we quickly neared 10,000 feet for some air work. Power is usually torque-limited for takeoff, but on very hot days the 810- degree-Celsius TOT takeoff limit may be reached first. There are no auto- matic torque or temperature limiters on the Allison, so it's up to the pilot to be sure neither limit is exceeded. (The torque gauge indicates horsepower The Allison 250 has two more oil injector ports than standard, allowing 30 seconds of inverted flight. directly, with 100 percent meaning that the engine is producing its full 450 shp. At higher altitudes, where TOT temperature is the principal limiting factor, available horsepower begins to drop off.) Once level, a fuel flow of 29 gallons (194 pounds) per hour delivered 170 knots indicated. Pitch trim proved extremely sensitive. Just thinking about moving the trim wheel seemed to affect the airplane. The fighter-type cockpit and first-class visibility naturally in- spired yanking and banking, so steep turns seemed a good place to start. Well-balanced stick forces made the 80- degree banked turns an exercise in pure fun. A few aileron rolls further showed off the airplane's ease of handling-and my own aerobatic rustiness. On a later flight with Allison pilot Jim Jackson, during his far more polished set of maneuvers, I would see what a good aerobatic trainer the Turbine Mentor really is . With no autopilot and limited bag- gage capacity, the AT-34 is not every- AOPA PILOT. 61 • JANUARY 1996 one's idea of the perfect cross-country airplane. What it lacks in these depart- ments, however, it makes up for in speed and endurance. At flight level 180, a fuel flow of 21.5 gallons (144 pounds) per hour nets a true airspeed of 200 knots, allowing for four-and-a-half hours' cruise with IFR reserves. At non-oxygen PILATUS PC-7 THE OFF-THE-SHELF MILITARY TRAINER ALTERNATIVE The world has changed a lot since the introduction of Beech's turbine-pow- ered T-34C Mentor and Cessna's T-37 jet trainers. Consider for a moment the demands faced by their eventual re- placement. It must perform in a jet-like fashion, to facilitate a student's proba- ble move to a front-line fighter or jet transport. Yet it should offer lessons to the pilot whose entire career may be spent flying prop-driven aircraft. It should be a good instrument platform, at the same time possessing superb visi- bility and nimbleness for formation, aerobatic, and basic air combat maneu- ver training. An upgradeable, modern avionics suite goes without saying. To support a variety of mission scenarios, it should have underwing hard points to carry external fuel tanks and weapons systems. It should be equipped with ejection seats, in recognition of the sometimes aggressive nature of its fly- ing. It should be easy to fly, yet difficult to fly well. Not least of all, it must be economical, reliable, and quiet. A tall order, perhaps, but one which any manufacturer worth its salt had better be prepared to fulfill. As the aerospace industry holds its collective breath in the long-running JPATS (Joint Primary Aircraft Training Sys- tem) competition, it's worth remem- bering that Pilatus Aircraft Ltd. already has a proven family of such aircraft fly- ing-the PC-7 and PC-9 turboprops. Both are currently in use by various air forces worldwide. When Raytheon Air- craft's Mkii initially got the JPATS nod from the Pentagon in June, it was really a vote of confidence in the PC-9. Much of the MkII's design is derived from that aircraft. If the Raytheon award survives the contract review forced by several losing manufacturers, Pilatus, the world's largest manufacturer of sin- AOPA PILOT· 62 . JANUARY 1996 altitudes, endurance drops noticeably. To get the same 200 KTASat 8,500 feet, expect to burn about 29.5 gallons (198 pounds) per hour, which yields three hours' cruise with IFR reserves. Neither slow flight nor a stall series held any unpleasant surprises. Power- off stalls proved gentle, with recovery gle-enginc turboprops, will receive royalties from Raytheon during the life of the contract. In the minus column, the MkII finds itself competing against the PC-7 and PC-9 for those same for- eign military sales marketplaces. (A large part of Raytheon's MklI output, in fact, is expected to flow to foreign air forces, some of whose training fleets make this country's '1'-37 and T-34C trainers look positively leading edgc.) Of the PC-7/PC-9/Mkil design fam- ily, only the PC-7 is available in the civilian marketplace. Most of the scver- al hundred copies sold since 1978 have been military orders, but a handful of well-heeled individuals in the United States and elscwhere havc anted up the $1.5 million admission price (at currcnt exchangc rates) to gct their hands on onc. The standard PC-7 comcs equipped with a 650-shp Pratt & Whitney PT6A- 25A engine fIat-rated to 550 shp, with a recommended THO of 3,000 hours. It boasts a sea-Icvel initial rate of climb of 2, 150 fpm at its Aerobatic category maximum takeoff weight of 4,189 pounds. At its heavier Utility category maximum takeoff weight of 5,952 pounds, it will still climb at better than 1,200 fpm. Maximum operating speed/ Mach (V1\IO/MMO)is 270 knots, or 0.55 Mach. It has less performance than its brawnier big brother, the PC-9, which is powercd by a Pratt & Whitney PT6A- 62 engine flat-rated to 950 shp-or its take-charge first cousin, the Haytheon MkII, with its 1,150 shp Pratt & Whit- ney PT6A-68 series engine. The PC-9 will climb at 4,090 fpm and hit top speeds of 320 KIAS, or Mach 0.68- most definitely jet-like. Nonetheless, the PC-7 possesses the kind of high- performancc characteristics that placc' it squarely in this elite class of aircraft. Recently we flew N7TP, owned by Charles Nogle of Champaign, Illinois. Nogle's PC-7, upgraded with a larger Pratt & Whitney PT6-25C engine pro- instantaneous following a slight push on the stick. The wing dips to the left during power-on stalls and is recovered easily with aileron. Bonanza pilots will no doubt feel right at home after a short time aloft in the Turbine Mentor. On the way back for some pattern work, Nogle suggested that I lower the gear and flaps and try a high-perfor- mance descent at flight idle, something that obviously shouldn't be done in a piston-powered airplane. With airspeed held below the 109 KIAS gear and flap extended limit, our descent rate in- creased to more than 4,000 fpm. My first approach was a little faster ducing 750 shp, performs considerably better than the standard airplane. Operating in the Aerobatic category, we saw initial climb rates of better than 3,300 fpm, placing the airplane about midway in climb performance be- tween the stock PC-7 and PC-9 mod- els. The bigger engine doesn't increase speed-the airplane is still limited by a redline of 270 knots. But the extra punch highlights the quantum leap in raw performance between this modern class of turboprop and the aging Men- tor fleet. The performance also holds up pretty well when measured against old-generation pure-jet trainers like the Cessna T-37, something that hasn't gone unnoticed by government bean counters around the world. A tour of N7TP's cockpit reveals the kinds of updated amenities not found in the Mentor. There is, for instance, a modern master caution annunciator panel that tracks the health of important systems and a glareshield-mounted angle-of-attack indicator to guide avia- tors in flying proper approach attitudes. An air-conditioning system is no doubt much appreciated by students and instructors alike during summertime sessions. The PC-7's pneumatically sealed canopy prevents engine exhaust fumes from leaking into the cockpit, a perennial problem in the T-34C during ground operations. Although N7TP does not have ejection seats-they are an option-the airplane can easily handle the extra weight. Well-organized system controls and niceties like electric trim and electric canopy retraction lend the cockpit an overall contemporary look and feel that the Mentor does not have. Compared to the Mentor, the PC-7 is considerably beefier. The PC-7 bulks out at 5,952 pounds, more than double the heft of the original piston-powered T-34 and almost a ton heavier than the turbine-powered T-34C. The PC-7's high wing loading of 33.3 pounds per square foot helps give it snappier con- trol characteristics, more fighter-like than Bonanza-like. If choice is the consumer trend of the 1990s, the PC-7 allows for a great deal of it. The South African Air Force recently ordered 60 PC-7 MkII Astras, a variant being delivered with a custom- designed glass cockpit avionics suite. G loading has been increased from the standard aerobatic category +6/-3 to +7.8/-3.5 and the engine upgraded to the 750-shp Pratt & Whitney PT6A-25C. The Astras will replace the SAAF's fleet of 1940s-vintage North American T-6G Harvards. While the outcome of JPATSremains in question in the United States, it's easy to see what a whole bunch of other countries (and a few lucky individuals) have already discovered-the PC-7 is a versatile, capable aircraft. It (and its more powerful siblings) stand ready to claim the title of new-age Mentor in the global marketplace. -vc AOPA PILOT· 63 . JANUARY 1996 ELI~ETMElectr~n.ic IFRTraining Environment Piper Arrow IV SELAircraft Module .If' Aviation 4 Teachware ~<IIIIIIIIIF Technologies PO Box 223254 Chantilly, VA 22022 Tel: (703) 378 7590 Fax: (703) 378 2511 In Europe call: #41 1 861 0561 .© 1995ATTechnologies. ELITETM is (1!-C(l~e~~r~_of_!~.Switze~and. All Rights Rese~ed.}·~~~~~_~~.~j~ctto change without notice. I Specifications Allison 250-B 17F turboprop, 495 shp derated to 450 shp Hartzel three-blade, reversible, feathering, 2,030 maximum rpm 27 ft 8 in 10 ft 32 It lOin 177.6 sq ft 16.8Ibs/sq ft 7.6Ib/hp 2,100 Ib 3,400 Ib 1,3801b 120 gallons (80 gallons in mains, 40 in removable tip tanks) Length Height Wingspan Wing area Wing loading Power loading Empty weight Maximum takeoff weight Useful load Fuel capacity Propeller Powerplant AT-34 'I\lfbine Mentor Price of Allison engine conversion: $400,000 Price as tested: $575,000 Performance Aerobatic category G limits +6/-3 Rate of climb, sea level 2,500 fpm Takeoff distance (50 ft obstacle) 700 ft Landing distance (50 ft obstacle) 670 ft Max cruise @ 10,000 feet 210 KTAS Service ceiling 25,000 ft Limiting and Hecommended Airspeeds Vx (best angle of climb) 70 KIAS Vy (best rate of climb) 100 KIAS Vs (stall in clean configuration) 60 KIAS Vso (stall in landing configuration) 55 KIAS VA (design maneuvering) 148 KIAS· VNE (never exceed) 219 KIAS• All specifications are based on manufacturer's calculations. All performance figures are based on standard day, standard atmosphere, sea level, gross weight conditions unless otherwise noted . than my 80-knots-over-the-fence goal and resulted in a floater. But by the sec- ond attempt I was hitting my aim point on speed. The third one was an ego- boosting squeaker. According to Nogle, the airplane has no bad habits, and I was starting to believe him. I reluctantly made the final full-stop landing- which, with the help of Beta thrust, required no braking to make the first turnoff comfortably. Too bad the AT-34 hasn't received a warmer welcome. It's a back-to-the- future example of how to breathe new life into an old design. D "ELITE is the premier real-time IFR training system that takes you a giant step further." - Capt. Bob Norris, Aviation Training Cm/mltant Call 1-800-557 -7590 for more information or to place your order. ELITpM 4.0 Prop Upgrade / Add-On $ 149.00 ELITpM 4.0 Jet Upgrade / Add-On $ 149.00 ELITpM 4.0 MEL "Twin" Add-On $ 349.00 ELITpM Basic IFR Training Package $ 349.00 ELITpM 4.0 Full Personal Simulator™ $ 699.00 (With a fleet of six aircraft and Continental Database) External Hardware Control Options call! "It had a flight director, stabilizer trim, and it all looked and performed like the real thing." - Tom Rege!)'ki. Pilot Career Counseler #1 Personal Simulator™ for PC and Macintosh. From single to multi en- gine, simple to complex aircraft, ELITE has the best IFR training en- vironment for student and profes- sional pilots. Fly any approach in the world. Use the easy-to-use, built-in graphic user interface or optional hardware. Whatever you choose, ELITE is simply the best. "The only PC-based flight simu- lator I have ever flown that actually responds like the aircraft. " - Pal BUller. CFll, MEL WRITE IN NO. 108 ON READER SERVICE CARD AOPA PtLOT· 64 • JANUARY 1996