We wonder if pairing an engine and an airframe gets the exhaustive attention it deserves or whether its just left to dumb luck. Theres no question that some engine/airframe marriages are made in heaven while others are the stuff of nightmares.
On the heavenly side, we count the Cessna 182 and the Continental O-470, the O-320 used in the Cessna 172 and the O-540 Lycoming Piper selected for the Cherokee Six. Engines/airframes that havent worked out so well include the Malibu Mirages ill-starred TIO-540-AE2A Lycoming and the Continental IO-360s Cessna used for its push-pull 337.
In our view, one of the best engine/airframe combinations of all time is the 200 HP Lycoming IO-360 mated to Mooneys J-model or 201. The IO-360 is a relatively simple four-banger with an established reputation for delivering a 2000-hour or better service run. In the 201, it will reliably yield 150 to 155-knot cruise speeds on about 10 gallons an hour and with 64 gallons of fuel, 800 miles of still-air range isnt a stretch for the airplane, if the pilots bladder can stand it.
Still, the 201 lacks the blistering speed some owners demand. Mooneys solution to this was the K-model 232 and eventually the Ovation and TLS. The aftermarkets solution was turbocharging for the IO-360-not a great mod, in our view-or simply stuffing a bigger motor into the J-model: Rocket Engineerings Missile conversion.
The Missile offers higher cruise speed and faster climb, essentially putting the short-body 201 on a performance par with the newer Ovation. The downside, of course, is higher fuel burn.
Four to Six
The heart of this conversion is the six-cylinder Continental IO-550-A, essentially the same 300 HP powerplant used in the Bonanza A36. The IO-550 is arguably one of the best engines Continental has ever made, although it, like other large bore engines, has been troubled by premature cylinder wear. The engine is smooth, starts easily and has good fuel specifics if leaned carefully.
In the Missile conversion, it has a 75-inch Hartzell three-bladed Scimitar prop which is full-feathering, as in the typical twin. Obviously, this is unusual for a single but follows the same design brief Rocket Engineering uses in its 350-HP Rocket mod. The full-feathering prop is touted as a safety feature, since a feathered prop will extend the glide in the event of an engine failure.
The $99,000 Missile Mod includes a new eight-point engine mount canted 2.3 degrees to the right to counteract torque, a new exhaust system, a modified 231 cowling to accommodate the obviously much longer engine and the three-blade prop. The cowl has a blister on the pilots side to clear the number 6 cylinder. To offset the forward balance of the larger engine, two batteries are fitted into a box that slides into the tailcone through the hat rack. Having two batteries is a plus for starting and IFR redundancy but getting at them for service is a bit awkward, in our view.
The cost of the mod includes virtually everything up to paint to match the cowl to the airframe and a training session at Rockets Spokane, Washington facility. Pre-1981 J-models will need tapered 231-style wingtips, another included item if its needed.
The weight of the larger engine adds 250 pounds to the airframe but allowable gross rises to 3200 pounds from 2740 pounds in the stock airframe, so the mod actually adds a little gain in useful load. J-models are typically in the 900 to 950-pound useful load while the Missile increases that to 1000 to 1100 pounds.
And, frankly, you need the payload for extra gas. A stock J-model carries 64 gallons of fuel which is, in our view, too little for a six-cylinder engine. Adding Monroy aux tanks-about $6500 installed-brings total fuel to 100 gallons or about six hours endurance, with reserve. In our view, to get the most out of this mod, the long-range tanks are a must.
We recently ferried a Missile conversion from Ohio to Connecticut and on to Florida and made some careful notes on performance. Whats immediately obvious is that takeoff and climb performance are dramatically improved. The 201 is a decent short-field airplane to begin with, the addition of another 100 HP only improves takeoff acceleration. On a fall day, we saw initial climb rate in the 1500 to 1600 FPM range to about 5000 feet, where it sagged only a little to about 1300 FPM. At 12,000 feet, we were still climbing at 1000 FPM.
Compared to the Lycoming, the IO-550 is noticeably smoother and with an exhaust note thats different although not perceptibly louder. Despite having an additional 100 HP, torque effects arent troublesome in the climb, thanks to the canted engine mount. On takeoff rotation, we felt the airplane needed a sterner tug to break loose but once trimmed, if felt like a 201-only faster.
The additional power is dramatically noticeable in the level off for cruise. J-model Mooneys typically take a few moments to gather themselves up for a slow acceleration to final cruise speed. Not the Missile. It virtually lurches from climb speed to cruise speed in seconds. We tried various cruise power settings at a range of altitudes.
We think the airplanes best altitudes are in the 8500 to 12,500- foot range, where plenty of power is still available without the inevitable drop off due to altitude. At 8500 feet, we noted a true airspeed of 173 knots on 15.5 GPH. Thats about 65 percent power or 195 HP, far better than the stock 201 can manage at the same altitude. At lower altitudes-2000 feet-flat out, we recorded 183 knots on 18.5 GPH.
The IO-550 engine in our test Missile was equipped with GAMIjectors but we were not able to run it well lean of peak, without roughness. At 6500 feet, 50 degrees lean of peak, we recorded 142 knots TAS at 9.7 GPH, but with engine roughness. For a max long-range economy flight with a decent tailwind, 1500 miles would be within reach at that power setting. (We think the engine roughness could be corrected with plug, mag or induction work.)
The Missile we flew had Precise Flight speed brakes which, while not a must, are definite nice-to-haves in an airplane thats 15 percent faster than a stock 201. Brakes seem like overkill on a 201, but not on a Missile.
Bottom line, the Missile conversion produces performance much like an Ovation and by the time an owner is fully invested in it, the cost will be about $50,000 less than a 1994 Ovation, which retails used for about $250,000. That the Ovation remains Mooneys best seller validates the concept that large-displacement, non-turbocharged powerplant is a good idea.
We like the Missile conversion; we think its a good one with well-thought-out engineering. Economically, its only attractive if you have a nice J-model airframe, like it and plan to keep it for a long time. The harsh reality is that high-dollar conversions like this are not good investments for the owner doing to converting. They may have little or no value to a buyer when it comes time to sell and buyers may be few and far between. An Ovation, on the other hand, will hold its value and appreciate and will be more saleable, in most cases.
The other side of this coin is that if you want a Missile, the smart-money way to buy is to be patient and look for one on the used market. They pop up occasionally. In a soft market-like that were suffering through now-some real bargains may crop up. Rocket Engineering says there are 55 Missile conversions in the fleet.
Also With This Article
Click here to view “Checklist.”