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Tue, Jul 15, 2003

New Power in Town: Bombardier V-6

V-220 and V-300T

Special ANN Feature by Tim Kern

These engines have been driving us nuts for a couple years; we've been pledged to secrecy that long! For the past two months, though, we've known all about them. Why haven't we told you? It was a deal -- we couldn't say anything, because the print guys had to be given a "fair chance" to get all their work done, and deliver to you. So, even though we knew, in the interest of fairness (and not getting our editorial tails in a legal wringer), we've had to hold off. We know that at least one "sport" aviation magazine jumped the embargo date by nearly two weeks - but, hey, they got the story wrong, anyway.

The wait isn't so bad -- the engine wouldn't have been available any sooner, even if we had told you.

Now the good news: there's a new powerplant soon to be available. Bombardier Recreational Products (they're not calling this new baby a 'Rotax 936' any more, even internally -- for instance, the valve covers, which, during development sometimes proclaimed, "Rotax," now read, "Bombardier") will offer an all-new, aviation V-6, in two flavors: a 220hp, normally-aspirated version, and a 300hp turbo. Bombardier claims, "...the best power-to-weight ratio in aviation technology."

The new engine is designed to fit where you're accustomed to seeing a 550 Continental or 540 Lycoming, with weight that's maybe just a couple pounds lighter than either (more on that later). It's not a 500+ cube monster, though; it's a tidy 3.1 liter (189 inch) machine. To make horsepower, it relies on advanced design, what Bombardier Recreational Products calls "the first true FADEC" controls, and a Rotax trademark, a gearbox. The engines make their top power at a carlike 6000 rpm.

... and speaking of cars, these new mills can drink your typical avgas; they will also be certified (we did mention that these are to be certified engines, didn't we?) to run on auto gas, or mogas. With a 4550 rpm cruise, you should see 16.5 gph go through the fuel filter and get turned into a state-of-the-art-clean exhaust. While that consumption figure is comparable to a 550 or 540, the savings on mogas (straight from the pump, you can save 60 cents to a buck or more a gallon; considerably more, if you also don't have to pay the 30-50 cent per gallon highway tax) could add up to significant dollars.

Specifics:

It's a 120 degree V-6, with a 4-main, straight-pin crank (two rods on each throw). It sports a dry sump design that uses about 2 gallons of oil. That oil is water-cooled, as is the entire engine. The bores in the aluminum-alloy block are Nikasil-coated. There's a single, chain-driven, overhead cam in each bank. One end of the crankshaft sports a unique flywheel; the other has a torsion bar extension, that goes to the 3:1 (108-36) gearbox. The fuel injection, a main component of the FADEC engine management system, offers clean firing, and doesn't have a venturi to help build up ice.

The V-6 will hang from special rubber/close metal mounts. The close metal design should stay relatively tight, in the event of an engine room fire, keeping added stress on the engine mounts to lower levels than conventional (1940s) designs.

The redundant EMS (Engine Management Systems) have a number of fully-redundant systems within them. Even in the event of failures, the redundant systems will still check one channel of manifold pressure, ambient pressure, rpm, and throttle setting. The EMS units also feature continuous data recording, so the entire history of the engine's life can be seen at the end of any flight. (Those who rent their airplanes to others, or members of fractional-ownership groups especially, should love that feature.) The EMS features an adaptive knock control -- it's a great way to keep the engine optimized, even as gasoline blends change -- or when you're using car gas, which is blended for the region where it's sold.

There's plenty of spark assured: you'll notice six double ignition coils.

Adding to the electrical redundancy are two 75-watt alternators. Everything with a wire on it, or a signal running through it, is duplicated. When we looked for the two ECUs, though, we couldn't find but one box. That's right -- the box is a mechanical item; rest assured, there's two ECUs in there, each with its separate wiring.

The ECU (the timing unit) has both camshaft and crankshaft speed and position sensors, for redundancy. It's a total dual-lane design -- two of everything; plus it carries a package of spare "maps," in case the sensors fail. For folks who still don't trust such things, and to add to the redundancy, there's an auto/manual, pilot-controlled select. If things really go phooie, there's still a fall-back, "limp-home" mode available; it is automatically employed.

This ANN News-Spy photo shows a test installation in a PA-28. Note that the valve covers are unidentified, and that there is a huge bunch of "extra" wiring in there -- for all the telemetry necessary during the test phase.

...as Opposed to a 'Fake FADEC?'

Bombardier Recreational Products likes to remind us that this is a "real FADEC." (Quite aside from the fact that it's on a V-6) it's not portable to other engines. Too bad -- a single lever controls the throttle, the mixture, the prop -- and triggers continuous onboard diagnostics. [Single-lever engine/prop management has come a long way since the FW190.] The advantages go beyond the obvious, and also include less mental fatigue for the pilot, and quicker, more-intuitive response to unforeseen events. Additionally, an unfamiliar or flustered pilot won't be able to flood out the engine, or lean it too much: thus security, longevity, and peace of mind.

Strategy: make the 'pie' bigger...

Bombardier's strategy is to sell, not replacement units or specialty units, but to develop more industry, overall. To that end, Bombardier Recreational Products will be offering the V-6 engines in complete, firewall-forward packages only, to certified-aircraft manufacturers. The integrated muffler design, the placement of the coolant radiators, the engine mounting -- everything will be designed for a specific application. The airframe manufacturer won't have to go to multiple suppliers to complete the power package. Bombardier will handle the power -- from the prop spinner to the firewall bolts. M-T and Hartzell have been doing the propeller work, for years. [The first flight of this puppy was back on March 11 of last year -ed.]

Speaking of the fuel system, the electric pumps (of course, there are two) will come from Bombardier. Each system includes a pump (located in the gas tank, as is automotive practice), two valves, an internal regulator (up to 3.3 bar pressure) and a feedback/return circuit, to keep fuel pressures steady, and to ensure fuel availability under all conditions.

...and speaking of flight conditions, the engine is not designed for use in aerobatic machines. Bombardier Recreational Products didn't want, in a mass-market engine, to saddle every customer with the necessary complication, weight, and expense of the systems a negative-G engine would require. Are there plans to do so in the future? The company says, "no." (This is a mass-market engine; aerobatic applications represent too small a possible clientele.)

The cooling system will hold 3 gallons of 50-50 water-antifreeze coolant, circulated by an automotive-style "plastic" impeller, that will move 81 gallons through the system each hour -- a complete circuit of all coolant in just over two minutes should keep the engine and oil cool. Additionally, high circulation should allow the usual, air-cooled-engine high-drag airflow to be closely cowled. There's a built-in coolant level sensor, too. In addition to the obvious advantages we've already listed, the protection water-cooling provides against shock cooling needs to be noted.

As for the need to pre-heat the engine, Bombardier says that you won't need to, until the temperature hits -25C (about 13 below zero, American). One other thing: water cooling means you can have cabin heat, free of the usual exhaust gas worries -- and as reliable and smooth as in a luxury car. No more, "frozen toes, burned knees" syndrome.

It's not easy being "green."

Bombardier Recreational Products, though, is addressing the increasingly-important issue of "environmentals" head-on. First, it's socially responsible; second, environmental concerns are going to be increasingly mandated, whether we're talking about emissions or noise; and third, when they are mandated, Bombardier will be ready to replace the old-design existing engines with what will be, by then, a high-volume, proven powerplant.

The rollout:

OK -- so you want one. What's next? First things first: Bombardier Recreational Products wants to be sure the world is ready. Rollout will be through Part 23 OEM airframe manufacturers, which will also service the powerplants, again following the automotive model. Before the engines are publicly available, the launch OEM will have a corps of trained mechanics; and will have field-replacement spares, and whatever special tools will be required. Repeat: the airframe manufacturer will be the engine-service interface. For the inevitable things that can't be anticipated, Bombardier will also maintain an AOG (Aircraft On Ground) response team -- anything the dealership can't handle, the AOG team will.

Bombardier Recreational Products will pursue a combined FAA and JAA program, to let customers worldwide experience the new engines.

After the Part 23 manufacturers are taken care of, certain Experimental kit manufacturers will be in line, for the firewall-forward treatment; after that, Bombardier plans to offer select STCs to the replacement/upgrade market. Thus, by 2008, pretty much everyone who wants one, will be able to buy one.

Quantity deliveries to the launch OEM (whose identity is still a loosely-guarded industry secret) will start in a little over two years. Price? Bombardier won't say, exactly; maybe they don't even know. You don't need a marketing MBA, though, to figure the new engines will be priced very closely to the existing 300 and 310hp competition, when all things -- the firewall forward package, special prop, etc. -- are considered. Whether Bombardier will be able to reduce costs enough to low-ball the market (and take it over) is something only their industrial and process engineers can tell. Whether they'd want to, is an issue probably left to their corporate lawyers and accountants.

It's the next wave.

What Bombardier Recreational Products has shown us is a totally-new aircraft engine, targeted at what many think will be the backbone of GA: the 200-300hp gas-powered segment. With global certification, mogas-capable engine management, automotive-style manufacturing techniques, processes, materials, and electronics, the engine promises to be long-lived and low-maintenance. With a fuel burn as good as (or even slightly better than) the competition's, significant savings can be realized by running mogas (and especially if you can buy it without paying highway tax), with very little performance penalty.

The big leap forward, in terms of universal acceptance, though, will come from other sectors: the people who live near GA airports and their politicians. The Bombardier V-6 is designed to satisfy not just the "scientific" environmentalists (those who look at emissions), but also the legions of folk who buy homes near small airports, and then rally to get the airports shut down, because of the noise.

These new V-6s are designed to be quiet.

Not only will Bombardier Recreational Products supervise the exhaust and muffler design (less-problematic on the turbo, of course), to ensure that the exhaust note is neither excessively loud nor offensive; the prop, where a giant portion of the noise originates, will be almost a non-factor.

Remember that gearbox, with the super-low 3:1 ratio? At peak engine rpm, the prop will still turn just 2000 rpm. The good news is, the prop tips won't be getting loud, ever. At cruise (just over 1500 prop rpm), you'll probably be able to read the Hartzell or M-T logo, as the blades go past -- but you won't hear much. Bombardier didn't say so, but maybe they're hoping that people will point to their new engine, and get their politicians to mandate new noise laws, since "it can be done." It would make for one great STC business, no?

Counterpoint:

This pair of engines has so many good things going for it -- packaging, technology, weight, power, efficiency, longevity, low-maintenance design, aerodynamic improvements, fail-safe operating modes, water cooling, truly modern engine controls, and a reasonable roll-out plan -- that we almost hesitate to even mention any concerns; but hey, if we didn't mention them, we'd be doing you a disservice.

First of all, it's a 6. All two-bank 6-cylinder four-stroke engines (not just V-6s, but the traditional flat-6 engines, as well) have one heck of a torsional vibration built into the crank. As engine-design guru Allan Lockheed (Allan is the developer of the industry standard "Engine Expert" performance design software; and his dad brought us the Vega, among others) told us, "There are two methods commonly-employed to counteract that vibration: some use a balance shaft; others make a V-8." Bombardier has tackled that problem with a balance shaft.

Additionally, Bombardier Recreational Products has made a preemptive strike on the possible problem of 5-cylinder operation. As noted above, the front end of the crankshaft has an extension on it. That tube, about an inch in diameter and maybe eight inches long, is a torsion bar -- a spring. Any roughness, any rotational shock the engine creates, gets transmitted through that torsion bar, which is tuned to absorb a lot of it -- the net result may very well be an engine that is smoother than most existing 6-cylinder engines, and nearly as smooth as a V-8. The gearbox, and the resultant multi-blade prop, will help in this area, as well.

Our other concern centers around that gearbox. It's not that Bombardier doesn't know how to build a bulletproof gearbox -- there are tens of thousands of examples in the air, of just how good a (Rotax) gearbox can be -- but we're concerned to varying degrees about two parameters of the gearbox design.

First, the idea that a prop cruising at 1500~1700 rpm can be very efficient, is not in dispute -- if the prop is thirteen feet in diameter. A prop of that size, though, would be a nuisance on a Bonanza-class design. The good news is, Bombardier says that Hartzell told them, through multi-blade (and presumably wide-chord) design, an efficient propeller of 80~96 inch diameter could be close to ideal. It's still on the big side, but, considering the noise factor, it may well be worth it. Remember, too: the gearbox output hub is located above the crankshaft centerline, a flexibility in design not attainable with direct-drive cranks -- and that allows longer blades, while maintaining the requisite ground clearance. It's not a whole lot higher than the flat-6 configuration (which keeps the crank at the top anyway), but anything helps.

The only truly inexplicable thing about this gearbox is the ratio: 108:36, or exactly 3:1. At top speed, that means that the exact same two teeth -- one from each gear -- will touch 33 times each second. If there is any mismatch in machining, if there is any impurity or foreign matter that gets mashed into a tooth, if there is the slightest problem in heat-treatment or another aspect of the metallurgy -- that problem will be revisited as often as 33 times each second. (You can hear 33Hz - it's that frequent.) Taking such a potential problem and "spreading it around," say by using a ratio of 107:37 (which would fit, at least, on the same bore centers), would mean that any pair of teeth would not meet, every time the prop shaft came around. (In this particular example, that particular mesh of prime numbers would happen once every 3959 engine revolutions -- roughly once every 40 seconds, at top speed; or just once in 50+ seconds, at cruise.)

Bombardier's engineers are aware of this, of course. Through channels, we got the answer that Bombardier is confident-enough in its suppliers and its own processes and quality assurance, that they are not concerned about this particular point. As for the unforeseen, they assured us that the gears are much larger than the engineering numbers would dictate -- in other words, the gearbox is overbuilt by a considerable margin.

While all that extra effort and bulk may well address the problem, we wonder why that particular ratio (rather than, say, the 2.891:1 ratio in the above example) had to be chosen. An alternate ratio could -- from a performance standpoint -- easily have been used, with the added benefit of reduced bulk, and a little more tolerance in gear manufacture, plus the reductions in weight and cost that must surely result. [Note: the Bombardier folks told us that ratio was chosen to make the pilot's job easier. A 3:1 calculation is a lot easier to do than a 2.891:1 calculation. We just don't know why a pilot needs to do the calculation in the first place -ed.]

Next: the prop-makers speak! Stay tuned to Aero-News!

FMI: Oshkosh booths 299, 305, 306; www.VaircraftEngines.com

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