Cirrus’ New Turbo: Baffling


The way the story goes, Cirrus Aircraft (still called Cirrus Design back in 2006) didn’t initially want to sell a turbo version of the SR22. Then customers starting seeing SR22s regularly doing 200 knots on FlightAware, clustered around central Oklahoma. The story continues that there were threats of canceled orders; customers would rather buy a used Cirrus capable of this mysterious extra speed than a new one.I don’t know if customer pressure finally convinced Cirrus to come out with the turbo (SR22TN), but when Cirrus did move, it took the unusual step of doing it by STC, embracing the turbonormalized system cooked up by Ada, Oklahoma’s Tornado Alley Turbos (TAT).The SR22TN has a turbo system strapped on the SR22’s high-compression IO-550 engine. Normally, this would be a detonation minefield, but TAT avoided this because the installation boosts only enough to maintain sea-level power as the airplane climbed. But with a high percentage of 310 horses available in the flight levels, the SR22TN pushed past the magic 200 in true airspeed.It was also mandated in the POH that the engine must be run lean-of-peak. This was a first, although other aircraft have been certified with the lean-of-peak option. But not lately. The TAT system proved Cirrus’ most popular model and one of the most successful and reliable turbo installations ever.Fast forward four years and Cirrus rolls out a new turbocharged version, the SR22T, at the annual Cirrus Owners and Pilots Association migration, which I attended last weekend in Dayton, Ohio. The new model has a TSIO-550 that ground boosts up to 34 inches and uses the traditional low-compression pistons. There are a handful of other changes that dress up the new model that Cirrus billed in the announcement as “lighter, quieter, smoother.”Judging by comments I heard at Dayton, some current Cirrus owners seem less than impressed. Devotees of the TAT system are practically evangelical in their support of the turbonormalized system, so it’s no surprise they latched on to some of the new model’s shortcomings and made their counter pronouncement: “slower, hotter, burns more gas.”Cirrus concedes all three of those points, but quantifies them as an acceptable trade. The speed Delta may be as much as 10 knots or so up in the mid-teens where most turbos travel; the fuel burn is 0.3 GPH more. I say “may be” because our trial of the airplane for an article in the July issue of Aviation Consumer revealed inconsistent data. But the TN still appears faster.The SR22T POH has “acceptable” CHTs in the low 400s. Some folks would disagree on how acceptable that is over the long haul, especially given the troubles Continental has had with premature cylinder wear. Outside the rabid TAT fans, whom you’d expect to turn up their noses at the new machine, reaction of the crowd at large seemed to fall between lukewarm and, well, apathetic.This disturbs me, especially in light of Cirrus billing the new model as having “future fuel flexibility.” This is a clear play toward the lower-compression engine being able to burn lower-octane gas. But notably missing was any statement on how much flexibility an SR22T owner would have when burning lower octane gas.Teledyne Continental has been pushing 94UL as substitute for endangered 100LL, but it concedes that to avoid detonation, power reductions may be necessary. So is a buyer of an SR22T covering his bases for a future fuel, or just thinking he is? Nobody knows and Cirrus isn’t volunteering any numbers to help buyers out. In other words, there’s no power table for running this airplane on 94UL or anything less than 100UL. That’s where the apathy bothers me. I think there are plenty of potential buyers who don’t know enough on the issue to ask this question.If five years down the road, a couple of hundred SR22T owners get smacked with enforced power reductions they thought they had immunity from, someone’s going to start talking lawsuit. I think an SR22T buyer is going to read “fuel flexible” as “burns 94UL without restrictions,” and this hasn’t been shown to be true. In addition, the SR22TN has an excellent maintenance history. The long-term maintenance of the new SR22T is an unknown. There’s some risk that this could come back to bite them if maintenance issues emerge.Against these factors, I’m having trouble seeing where the risk of introducing the SR22T is worth whatever gain there might be. Normally, new models are supposed to be better in measurable ways–faster, higher and so on–but this one isn’t. Not in terms of the engine anyway.I would say that many of the folks at the COPA migration were baffled by the introduction of the SR22T, thinking there must be some behind-the-scenes deal making or myopic bean counting going on. I can see why.