Two Single-Engine Jets Funded Again

The Cirrus SF50 Vision single-engine jet development program had been on hold since last fall while the company’s new Chinese based owner, CAIGA, analyzed and reviewed the program. But the new owners are apparently satisfied with the prospects for the small jet and Cirrus says development work on the program is now going ahead full speed.

A few weeks ago the Diamond D-Jet got a similar shot in the arm in the form of new company ownership and financing from investors fromDubai. The D-Jet program has been in the works for years and three prototypes have been flying. But like the Cirrus Vision, the D-Jet program had been on the shelf for months awaiting new funding commitments. 

In contrast, Piper spent lavishly on a large redesign of its PiperJet over the past couple of years. Piper created a much larger fuselage for what became the Altaire single engine jet, and predicted a higher cruise altitude, longer range, and higher speed. Piper went so far as to recruit engineers for the program in Wichita, an effort complete with billboards in the Air Capital.

Piper spent lavishly on a large redesign of its PiperJet over the past couple of years but then pulled the plug and canceled the program.

But suddenly, after a large presence at the NBAA show complete with full scale mockup of the Altaire cabin, Piper pulled the plug and canceled the program. The move was so abrupt that advertisements for the jet were still appearing in aviation magazines after the program had been suspended.

The owners of all three single-engine jet programs are now located outside the U.S. with Piper’s parent being based in Brunei, Cirrus in China, and Diamond in the Middle East. That certainly means there is a global view at work when it comes to single-engine jets. But how can three companies look at similar programs and come to opposite conclusions on how to proceed?

While I can’t possibly know how the discussions evolved at each of the three companies, and what factors were considered, I do know what the biggest challenges are for any single-engine jet design. It really boils down to the inefficiency of jet engines – particularly small engines with a modest bypass ratio – when flying below 37,000 feet or even higher, and the 61-knot stall speed limit on single-engine airplanes.

Cirrus and Diamond expect to certify their jets with a maximum ceiling of 25,000 to 28,000 feet. It is extremely doubtful the FAA would ever approve an operating ceiling for a single above 30,000 feet. The reason is that cabin pressurization could be suddenly lost if the engine were to fail. Or even more likely, pressurization would be lost by the failure of any element of the single string pressurization system, including pipes, couplings, valves, and so on. Multiengine airplanes have at least two of everything needed to maintain cabin pressure.

The Diamond D-Jet recently got a shot in the arm in the form of new company ownership and financing from investors from Dubai.

Being restricted to a low maximum cruise altitude means the single-engine jet will have higher fuel flows than a single-engine turboprop, or piston. The extra speed of the jet will help make up for the higher fuel flows, but, still, a single-engine jet will need to carry more fuel for the same trip than a piston or turboprop single.

The weight of the extra fuel increases wing loading, of course, and a higher wing loading leads to a higher stall speed. To meet the 61-knot stall maximum in landing configuration the single-engine jet needs a bigger wing than is desirable for efficient cruise. A very effective wing flap can help reduce the stall speed, but in the end, weight will win out and the single-engine jet won’t be able to carry as much fuel as most of us want to make the nonstop trips we want to fly.

There is also the one turn spin recovery rule that applies to all singles and that can be complicated in any airplane. It’s most likely that a successful single-engine jet will employ a stall barrier “stick pusher” system that actually prevents an aerodynamic stall and thus prevents a possible spin.Pilatus uses such a system on its PC-12, and the big majority of larger jets all have stick pushers.

A stick pusher system adds weight and cost because everything including sensors and the actual stick pushers must be dual. But an even larger penalty for single-engine airplanes is that the pusher must activate at a higher speed than the actual stall so that margin eats into the 61-knot stall maximum at least a little.

The Williams International FJ33 will be featured on the D-Jet and the Cirrus Vision. Altitude certification limits and higher fuel flows means more fuel needed for the same trip taken in a turboprop or piston-driven aircraft.

Then there are all of the typical developmental issues that any airplane faces such as performance goals, flying qualities, dealing with icing, system design, and so on.

Can a single-engine jet be designed and certified? Of course it can. Will such an airplane be accepted by pilots and be a sales success great enough to return the development cost? Nobody knows. But three investor groups have voted with their dollars in the past few months and by two to one, the bet is that a single-engine jet can succeed.

But we can’t hold our breath waiting for the outcome. Diamond has set no firm delivery schedule that I am aware of, and Cirrus recently inferred that first delivery of an SF50 Vision is about three years away so there is plenty of time for more twists and turns before the first single-engine jet is delivered.

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18 Responses to Two Single-Engine Jets Funded Again

  1. This is great news. I’m not sure many appreciate the huge advantage of a single-engine jet over a twin-engine jet in terms of lower maintenance cost. Any multiengine turbine aircraft is required by regulation to be maintained strictly in accordance with the manufacturer’s inspection program, while a single-engine turbine that weighs less than 12,500 pounds is maintained under the same minimalist and flexible maintenance regulations as a Cessna 182 — all that’s required is one annual inspection every 12 calendar months in accordance with Part 43 Appendix D, and the manufacturer’s recommendations are nothing more than recommendations, not requirements. No phase inspections, no TBOs, no mandatory replacement intervals — at least for the most part. The sole exceptions are maintenance mandated by Airworthiness Directive or Airworthiness Limitation, just like any other Part 23 light airplane.

    I’m getting too old and too poor to ever own one of these birds, but I’m pretty excited about showing younger, richer aircraft owners how to maintain these things without damaging their wallets. I’m particularly excited about the Cirrus jet, which has a cavernous interior and a CAPS chute system which more than makes up for its single engine. (CAPS has a near-perfect record of saves, witness yesterday’s CAPS pull in the Bahamas.)

  2. CRAZEDpilot says:

    So glad to have this type of information disseminated to us all in the pilot community, we really appreciate it! The photographs of these beautiful jets are amazing and the detail informative even for those of us who don’t have private jet ownership in our future. Thanks again for your time and efforts!

  3. John in Brisbane says:

    Nice article Mac. I seriously love these new jets but I reckon that is my heart talking. Something like a TBM 850 with the potential for 320 KTAS is what the head is saying.

    Despite the storied litany of issues, I still think the eclipse 500 was viable and maybe it will be in future. Or a 4 seater with two of those fj22s …

  4. Robin Oldfield says:

    Jets are sexy, but a pressurized Bonanza size turboprop would be safer, more versatile, and undoubtedly less expensive for the owner to operate and for the manufacturer to develop.

  5. Michael Sheridan says:

    I’ll take a turboprop ANY day. Safer, more accessible to more pilots, less expensive on all levels, not the least of which is fuel. In many cases greater range and greater access to airports. I can’t any advantage other than what some see as “sexy” red plane that looks like something out of a Flash Gordon cartoon. Odds are at least one of the two left will never see the light of day. I look forward to the Kestrel.

  6. Drew says:

    If the market for these things is determined to be outside the USA, say China, and the owners are not American, one wonders how long FAA certification constraints will control their design.

    • Mac says:

      The D-Jet is being developed in Canada and will be subject to Canadian rules first, but those are very close to FAA standards and both countries usually can issue a joint certification. The Cirrus SF50 is being developed entirely in the U.S. so there is no question FAA rules apply. The reality is that in most circumstances the FAA is less demanding of new airplane designs then are other national aviation authorities. Perhaps emerging nations will establish their own certification standards in the future, but that has not been the history. New certification systems have been built on what has worked in the past.

      Mac Mc

  7. Pingback: Two Single-Engine Jets Funded Again | Left Seat « The Official EDMO Blog

  8. Alex Kovnat says:

    It is an intellectual frustration that the Piper Altaire design will not be pursued.

    With single engine general aviation jets, we have seen three configurations. The Cirrus SF-50, uses the old Beechcraft V35B-type tail with the single engine’s backblast passing through the angle between the V-tail surfaces. The Altaire, borrows a little from the old McDonnel-Douglas DC-10 in that the single engine is intetrated into the vertical stabilizer. The third concept, that of the D-Jet, uses a bifurcated inlet configuration that reminds me of the Douglas A4 Skyhawk beloved for years by Navy pilots.

    Of the above, which would one prefer? It seems to me that it would be a toss-up between the Altaire and Cirrus configurations. But with the former not being pursued, we will never find out from real world experience which configuration owner-pilots would like the best.

    Here’a a possible market for single-engine jets whose cruise speed would be faster than the TBM850 single engine turbobprop plane: Flying businesspersons whose travel does not require carriage of passengers, and whose desire to fly fast is such that they wouldn’t mind wearing an oralnasal oxygen mask like a fighter pilot. That would eliminate the pressurization issue, so said aircraft wouldn’t be restricted to no higher than 30,000 feet.

  9. Earl Turner says:

    Beautiful picture of the Diamond Jet. An airplane that good looking has to be successful.

  10. Alex Kovnat says:

    The Diamond jet isn’t bad looking and the old Douglas A-4 was a great attack aircraft that served the U.S. Navy (and also, other nations) well. But for civil aviation it seems to me the Cirrus concept would have lower air intake losses. The now-discontinued Piper Altaire configuration seems to me to have the best aerodynamics of all — air moves in a straight line into the engine, through the engine and out the back without going through intake ducting like the center engine on the old Boeing 727, or the side-intake single engine jets mentioned above.

    Also, with the Altaire the engine exhaust flows backwards freely, without scrubbing on the fuselage. Since the Altaire offers both good intake and good exhaust aerodynamics, I think it would be nice if some financier or group of financiers would revive the program.

    • Mac says:

      You’re right about the Altaire engine location on the fin having the least losses for both intake and exhaust. But there were concerns about pitching moment from power changes with the single engine being so far above the airplane waterline. Piper had anticipated the need for some sort of a trim system that could compensate for the pitch changes with power, but the limited flight testing done in the PiperJet indicated the pitch changes would not be as strong and pronounced as feared and a special compensation system compensation system probably wouldn’t be required.

      Mac Mc

  11. David says:

    I am just ticked off at Piper for wasting some much money. They should have just put the Piper Jet into production instead of spending a lot of money an the redesign into the Altaire. After the Piper Jet was in production and making money they could have built the Altaire. Instead they have pushed themselves closer to the edge.

  12. Bill Moon says:

    A real jet will take an investment of 400 to 500 million (if the mistakes are not to large) to get the aircraft certified and in production. Return on investment is not there. I saw a comment by one of the companies developing a new jet, “10 million would fund the program”. With thinking like this, people will continue to lose money to the huckers and we won’t get new aircraft.

  13. Ed says:

    The 61 knot rule for single engined aircraft is not absolute. The PC12 originally came out with a MTOW of 4100kg (9020lbs) and a 61knot stall speed, but that was increased to 4500kg (9921lbs) and 64kts stall speed in the PC12/45 that was produced new and most of the older ones modified to. The PC12/47 and the PC12/47E (NG) have 4740kg (10450lbs) and 66kt stall speed a very useful weight, but there is no kit to modify the PC12/45′s to /47′s. Apparently they have to show “an equivelent level of safety” at the higher stall speed as at 61kts – ie the plane has to be more crash resistant. One of the changes to take the stall speed from 64kts to 66 kts was new pilot seats – the old ones obvioulsy couldn’t meet the more demanding requirements of the higher stall speed. I don’t know if this can be done with a new design or only permitted with an existing design that has proved itself already.

  14. Street says:

    A very efficient design for a very personal jet is also very simple and inexpensive to aquire and to operate: Take up a hang-glider or hot-air balloon, drop your pants, and let a huge fart with an opposite bearing to your destination. If it’s huge enough of a blast, the forward thrust should be quite sufficient to getcha where you need to go. Also, if you go tandem, you produce twice the thrust (ingenious)! Then, your personal jet is all natural, ergonomic, and very… how shall we say… umm, green (or brown, butt-friendly to the environment, see)? A good healthy chile dinner before each flight, with lots of garlic, will produce the thrust, and away you go.

    And away I go. Cheers!


  15. roger russton says:

    I’d rather just have a real warjet for fun and a modern (single lever power controlled, no shock cooling possible, modern design) piston engine single or true light twin (i.e., trransport category single engine performance) for transportation.

    More fun, more WGBD (why guys buy stuff in the first place) , and cheaper.

    That guy with the 106 project is getting reasonable-you could be lined up and in MAX AB on the runway for, I’m realistically thinking, a couple million total. A civilian jet is going to be a letdown emotionally by contrast-it won’t accelerate like an old Lear 23 let alone a real fighter.

  16. constantly i used to read smaller articles that also clear their motive, and that is also happening with this article which I am reading now.|

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