Last time, we started the search for speed by discussing some of the criteria for a successor project to my current airplane, an F1 Rocket. I explained the idea of a target list, which is a table of desired characteristics that the new project should meet, balancing the goal of flying faster with the desire to get there in one piece. We looked at a number of candidate piston-powered designs, mostly clustered around 240 knots, but capable of up to 270 knots with turbocharging and altitude.
I also introduced two assistants who will help me make a decision. On my left shoulder is Luke, a little red fellow with a pitchfork, who has a tendency to jab the side of my neck while shouting, “Go faster!” On the right is Charlie, a munchkin with a halo, who calmly whispers caution, preparation, and sober assessment of risk.
Needless to say, these guys aren’t exactly best friends. But we’ll hear from both of them as we set our sights even higher in terms of both speed and cost, with the introduction of turbine-powered options.
Hold on to your hat and grab your wallet; both could be blown away!
The Lancair IV was the company’s first four-seat model. This in itself is a bit unusual, as relatively few kitbuilt aircraft come with more than two seats. Flying with a turbocharged IO-550, the airplane promised blistering performance to match its good looks. As the engine was turbocharged, the airplane achieved its best performance at higher altitudes, so the pressurized IV-P was introduced shortly after the IV.
None of the IV-variant kits are currently in production, though completed and partial kits can still be found on the used market.
The Lancair IV and IV-P are airplanes I really wanted to like. Cruise speeds are close to the target, they have a spacious cockpit with four seats and baggage space, and they look cool. However, there are some nasty characteristics associated with this airplane.
The published climb rate is a decent 1500 feet per minute. With optimal cruising altitudes at 24,000 feet, this would mean something approaching 25 minutes to get to altitude, assuming a conservative reduction in climb rate as altitude increases. However, anecdotal reports suggest that holding the maximum climb rate may not be realistic on a warm day, with some owners stating a need to hold the nose down to 500 feet per minute in order to keep cylinder-head temperatures below 400 F. This obviously makes for a much longer climb before realizing those impressive published cruise figures and means that, on many flights, climbing to optimal altitudes is not realistic. Furthermore, the pressurized version requires maintaining a certain amount of power to hold cabin pressure, which causes VNE to be exceeded on the descent unless using speed brakes. Using speed brakes means giving up a lot of that hard-won altitude and missing out on the downhill boost at the end of the flight. This also lends argument to keeping the airplane at lower altitudes, and again missing out on those impressive cruise numbers.
However, the biggest issue with the Lancair IV and IV-P is its atrocious safety record, related at least in part to its stall and spin characteristics.
In May 1999, the CAFE Foundation flight tested the Lancair IV and confirmed a stall speed of 66 knots indicated. They also conducted a series of stall tests and did not find any nasty behavior. However, the experience of the test does not seem to have been frequently repeated within the customer-built fleet, leading a factory representative at one time to advise owners not to engage in stall testing of the aircraft under any circumstances, at any altitude.
A search of the NTSB accident database reveals 66 reported accidents involving Lancair IV aircraft, of which 35 resulted in fatalities. That is a stunning 53% fatality rate. There are currently 353 Lancair IV aircraft in the FAA’s registration database. If we assume that all of the fatal accidents resulted in the aircraft being removed from the registration database, this implies a population of 388 aircraft, of which 66 have been involved in accidents, or 17%. This is a bit of a misleading statistic as it is comparing all aircraft registered, from the first model constructed to the last, and all accidents that occurred after the first model was constructed, so it is not the same as an annual accident rate. However, having 17% of the fleet involved in an accident and 9% (35388=.09) involved in a fatal accident is a sobering statistic. This means that almost 1 in 10 Lancair IV aircraft constructed to date have crashed with deadly results. A perusal of the fatal accident reports shows a high number precipitated by engine failure, followed by stall/spin and/or collision with terrain. A high stall speed would make off-airport landings more challenging to conduct without getting hurt. That being said, 66 knots doesn’t seem exceptionally high. However, I have seen some evidence to suggest that a number of Lancair IV aircraft have stall speeds significantly greater than 66 knots. According to one builder I spoke to, the original flap track mechanism design was very intolerant of any build variances, with the result that the finished assembly would often not fully deploy. His aircraft was affected by this, and the stall speeds he experienced were more like 90 knots clean and 82 knots dirty. This is a whole different ballgame than 66 knots. I have seen stall statistics for other Lancair IV aircraft that were similarly high but don’t know if the reason (limited flap deployment) was the same. However, assuming a 90-knot clean stall speed, failure to fully deploy flaps upon landing after an engine failure would certainly make crash survivability a long shot, even if the aircraft is under control at touchdown.
There are some interesting wing tip modifications being developed by a company called Vortecx Industries in an attempt to tame the IV’s stall and spin behavior while maintaining or even improving cruise speed. This was covered in KITPLANES [“Taming the Lancair IV,” October 2015], but despite some generic claims of lowered stall speed, I have not yet seen evidence to demonstrate it has been lowered significantly below the 66 knots seen in the CAFE testing, or that it has resulted in docile spin characteristics.
Another company, RDD Enterprises, has developed a modified IV/IV-P that includes a new wing, a new tail, deice, and a ballistic parachute. Their website claims a stall speed 3 knots slower and cruise speed 17 knots slower than published by the CAFE foundation, all at a price “similar to a new Cirrus SR22.” I’m not really sure what that means, other than it puts the price out of my target range.
Luke says, “Still not fast enough,” and Charlie says, “You can’t enjoy flying if you’re dead.”
Lancair IV/IV-P Turbine
The Lancair IV/IV-P Turbine resulted from replacing the Continental IO-550 with a Walter M601E turbine engine.
Not long ago, these engines were plentiful and cheap—an overhauled 601 could be obtained for about the same price as a new Continental IO-550 or Lycoming IO-540. Unfortunately, that has since changed as the prices seem to have risen up closer to the Pratt and Whitney PT6 that they were designed to emulate. It’s hard to get a handle on what the market price is for these engines at the current time, but as near as I can tell, an overhauled PT6 is likely to cost north of a quarter-million dollars, and the Walter engines are not far behind. While the IV/IV-P Turbine kits are no longer in production, used examples can be found for around $400,000, which is probably less than it would cost to build a new one at current engine prices, if a kit was still for sale.
Woo-hoo—322 knots! The speed of these airplanes certainly meets the target, and the climb rate easily addresses the shortcomings of the piston-powered examples, getting the airplane into the speed and efficiency of the flight levels in a matter of minutes. However, the published stall speeds belie the same safety issues plaguing the piston-powered IV/IV-P: high real-world stall speed and nasty spin characteristics, contributing to a high fatal accident rate. As much as I love the performance of this airplane, the safety issues and cost put it out of the running for me. Too bad—the original promise of a docile, high-performance airframe with a cheap turbine would make a compelling proposition.
Luke says, “Go for it, you wimp!” Charlie says, “Over my (your) dead body!”
The Lancair Evolution evolved out of the Lancair IV-T (or Propjet) and was driven by the desire to design a new airplane around the assumption that it would be powered by a turbine, rather than adapting a turbine to an existing design, as the IV model Propjets did. This also afforded the opportunity to address some of the design shortcomings of the IV models, especially with regard to flight characteristics and stall speed.
The selected engine for the Evolution was the Pratt & Whitney PT6, which combined with a high kit price in the vicinity of $500,000, resulted in a finished aircraft costing well north of $1 million.
The dwindling number of pilots today means a limited potential market for any aircraft. That market drops when the pilot must also be the builder of the aircraft, and the potential market of pilot/builders who are able and willing to spend over a million dollars on an airplane and still build it themselves is likely quite small, indeed. This possibly had something to do with news of the company shutting down in October 2017, though rumor has it they have since reopened under new ownership.
The Evolution design clearly placed a heavier emphasis on safety than the predecessor IV models, with published stall speed down to a respectable 61 knots, an airframe parachute system, and deice. With the larger of the available engines (PT6-140A), it achieves a cruise speed of 330 knots, comparable to the IV-T. With the smaller engine (PT6-135A), it cruised 20 knots slower than the IV-T. However, even with the smaller engine, losing 20 knots at the top end is worth it, if it results in much safer characteristics at the bottom end, and the statistics seem to prove it. There are 84 Evolutions on the FAA aircraft registry, but only 3 accidents on the NTSB database, of which 1 was fatal.
In order to achieve its impressive 330-knot cruise speed, the airplane needs to be up high. The published numbers were attained at 28,000 feet, where the airplane maintains an 8000-foot cabin altitude. This is the highest of all the planes I looked at, but with an initial climb rate of 4000 feet per minute and reports of 11 minutes to cruising altitude, not much time is lost in getting to where it is fast and (somewhat) economical.
Some flight reports indicate light elevator and very heavy ailerons, especially at higher cruise speeds, although this may have been corrected with an aileron redesign in later models. An actual flight would be needed to confirm control feel for a given aircraft.
Kudos to the designer for developing what appears to be a much safer, but still fast airplane. It’s unfortunate that the cost of the airframe kit was placed about 10 times higher than other, slower airframe kits and also unfortunate that a low-cost turbine alternative was not available. In the 1990s and early 2000s, overhauled Walter engines were available for under $50,000. If a reasonable cost Evolution airframe had been mated to one of those engines, the aircraft might have been finished for not a lot more money than a new RV-10 today. If that had happened, we would probably be seeing hordes of Evolutions in the sky. However, it’s just a pipe dream for a speed-obsessed layman like me.
Luke says, “It’s fast, it’s sexy. I like it. Get one.” Charlie says, “As long as you don’t mind giving up food…and your car…and your house…and going into debt.”
(Photo: FlugKerl2 (CC BY-SA 3.0 [https://creativecommons.org/licenses/ by-sa/3.0]), from Wikimedia Commons.)
The original Legend was first flown in 1996 with a converted automotive engine. However, like many such attempts, the conversion was found to be problematic and in 1999 was replaced by a Walter M601E turbine. This proved to be a much better match for the aircraft and propelled it to some impressive performance figures. In recent years, prices have risen significantly, and the M601 has become less attractive, with the result that Garrett and Pratt & Whitney turbines are now finding their way into the aircraft. Unfortunately, some of these new engines drive the price up significantly, but the performance goes up, too.
The company producing the Turbine Legend dropped out of sight for a while, but has recently returned under new ownership and is now producing new airframe kits, starting at $199,000. The corporate structure is unique, with the company itself located in British Columbia, the composite pieces constructed in Florida, and builder assistance offered by a company in Alberta. Various engine alternatives are offered on the company website, including automotive conversions, Garrett, and Pratt & Whitney, but no longer any Walter turbines.
The Turbine Legend is not pressurized, so getting optimal performance will require supplemental oxygen: cannulas below 18,000 feet or masks above that. The company website advertises a set of performance specs that seem to match the old M601 powerplant, but not the alternatives, leaving some question about how the other engines perform. The table shows the M601 data from their website, combined with some third-party flight reports.
(Photo: Bill Larkins (CC BY-SA 2.0 [https://creativecommons.org/licenses/by-sa/2.0]), via Wikimedia Commons.)
As with some other high-performance aircraft, some of the flight reports indicate light elevator and heavy ailerons, especially at higher airspeeds.
Oddly enough, it appears that the cruise performance for the Turbine Legend was determined at just under 18,000 feet. Some comments indicate that the Walter engine actually loses efficiency above this altitude. If this is true, and given that the Legend is not pressurized, determining performance figures at this altitude makes sense and means less time is spent in the climb—in this case, potentially less than 5 minutes to get to cruising altitude.
The design of the Legend looks much like a fighter aircraft: two tandem seats and not much else. I found a reference to a 10-cubic-foot baggage compartment, but I’m not sure where it is squeezed in. However, 10 cubic feet is not enough for what I typically pack for a week’s vacation, never mind my wife.
At the current time, there are only 17 Turbine Legends on the FAA aircraft registration database. The NTSB database shows 3 accidents, of which 1 was fatal, caused by a collision with a tree after engine failure.
While half the cost of an Evolution, $600,000 (estimated completed cost) is still a lot of money for a kit aircraft. The small number of airframes makes it difficult to come to any definite conclusions about the fleet, but a 66-knot stall speed is above the target limit, and while the Walter engine might like to operate best around 17,000 feet, the others like to be higher, which makes the lack of pressurization a consideration when using these other powerplants. Furthermore, there are always issues that come up with any new engine installation. Building a new airframe now, with one of the alternative engines, means potentially dealing with some new-installation teething issues that would likely have already been worked out if there were dozens of examples already flying.
Not long ago, a derivative of the Turbine Legend called the Venom was marketed out of Florida, powered by a GE H75 turbine and sporting some impressive performance numbers. GE was actually involved as a partner in the project, however, rumor has it that GE has since pulled out and taken their engine home with them. Since then, the new owners of the Turbine Legend acquired the rights to the Venom, so it’s now all under one roof, with a variety of engine options offered. The new owners are quite responsive and seem very enthusiastic about their airplane.
Luke says, “Meh. It’s pretty fast. You could do worse.” Charlie says, “Stall speed is too high, baggage is almost nonexistent, and you will still need to give up food if you want to pay for this aircraft.”
With six seats, a turbine engine, and a max gross weight of 7500 pounds, the Epic LT is in a whole different class than the typical homebuilt airplane.
Bend, Oregon, must have something fast in its water, as it is not only the home of Epic aircraft, but also was the location of Lancair’s manufacturing facility prior to its sale to Cessna (who subsequently shut it down).
Epic Aircraft flew the Epic LT in 2004, produced a number of kits, passed into new ownership, and is today focused on what appears to be the final steps needed to start producing factory-built certified models, marketed as the E1000. In fact, clicking on the “Aircraft” link on the company website only produces information about the E1000. No mention is made of the kit predecessor or whether any kits or support are still being offered, leaving open the question of whether owners of the LT might be left to feel orphaned.
Although the engines for both the Epic LT and Evolution share the same beginning to their names, PT6, the Epic LT uses the A-67 variant, developing 1200 horsepower. This is about 50% more than the “big engine” version of the Evolution, allowing the much bigger aircraft to be propelled to an impressive 325 knots true airspeed, nearly matching the fastest turboprop in factory production today, the TBM 900/930.
The fact that the LT was the starting point for a certified model bodes well for its flight characteristics, but it’s not clear what modifications may have been made in the certification program or how the two aircraft might actually compare. However, the size of the airplane means it won’t fit in our hangar, the stall speed is above our upper limit, and the takeoff and landing distance requirements just barely push through the target limits. Of course, there is also the minor detail of cost.
Luke says, “Cool plane! Fast, climbs well, good range, lots of room. The girls will think you’re rich. Go for it!” Charlie says, “You can’t afford to buy or feed it, and it won’t safely operate out of your home field or fit in your hangar. You’re married, and ‘the girls’ will know there’s no money left after you blew it all on the airplane. Get real!”
And the Winner Is
The F1 Rocket.
By most experimental aircraft standards, the cruise is pretty good, the climb and efficiency is excellent, and there is enough useful load and baggage capacity to take the two of us to Oshkosh with a week’s worth of camping gear (as long as we pack like we’re backpacking).
The numbers in the table are based on my airplane and may not be an exact match to published figures. The insurance is liability only, and the height is to the tip of the propeller with the tail on the ground.
My desire to build something new is still frustrated. The dream of a fast plane at a reasonable price that won’t kill me is still just a dream. Perhaps it wouldn’t be so unrealistic if it was possible to buy an engine for less than the price of an airframe kit, and if there was a matching airframe kit that was only 50% more than the typical homebuilt (after all, if it’s only 50% faster, it should only cost 50% more, right?) However, the reality of the current market is that the next airplane that would fit my budget, skills, and desires doesn’t exist yet.
It’s interesting that of all the airplanes in the list, only the Turbine Legend (and possibly the Evolution) is currently available as a new kit. All others have ceased production, though a couple may yet come back to market—time will tell. There’s an interesting question about why those airplanes have disappeared and left such an obvious vacuum in their class. Perhaps the answer lies in the fact that the compromises necessary to achieve speed have historically resulted in airplanes that were dangerous to fly, and as much as many of us want to fly fast, our Charlies are holding us back.
In the late 1990s and early 2000s, the Walter M601 provided an inexpensive, powerful engine option. If something similar could be found today, it might provide the basis for a revival of this class of aircraft. A new Continental or Lycoming big-bore engine pushes up against (or through) $50,000, and at the top end produces close to 400 horsepower. If the dollars-to-horsepower equation could be scaled at that ratio without compromising reliability, there might be some possibility to mate the engine to a reasonably priced airframe and produce an airplane that doesn’t cost more than a house. However, so long as high-power engines are pushing up to a quarter-million dollars, the prospect for an inexpensive kit and finished airplane in a (somewhat) affordable range seems unlikely at best.
It’s human nature to strive for more: bigger, faster, better. However, maybe it’s time I shook my head, faced reality, and accepted the fact that the airplane I have is the best fit for me, and I should fly and be satisfied, and stop pushing for more.
Luke says, “No way!”
You’ve probably noticed that you prefer the F-1 Rocket but the picture is of a Harmon Rocket. There are differences. The rectangular wing has a greater c.g. range than the Evo wing, which may be of interest if you want to load up the rear (only) baggage compartment.
IIRC, turbine engines become less efficient as altitude increases, but airframe efficiency usually increases faster than engine efficiency decreases.
As you noted, the Rockets come with at least two different wings. Harmon Rockets typically have the rectangular wing as you mention. The F1 Rockets came in two wing flavors: (1) Standard Wing and (2) Evo wing. The Standard wing (similar to the Harmon “rectangular wing”) has a wider C of G range as you noted. The Evo wing seems to have an edge with a slightly lower stall speed and a slightly higher cruise speed (especially at altitude). My own F1 Rocket was built with the Standard wing, as the Evo wing option was not yet available when I built it. That being said, I like the ability to carry my wife and all our camping gear for Oshkosh and the Evo wing might require that she leave some of her stuff behind, which would make me a less popular pilot! 🙂
Great article! Safety > Speed
I realize you wrote this article a few years ago. Have you been following the progress of https://www.darkaero.com/aircraft/? 275 mph cruise, two seats, 1700 sm range, 750 lbs useful load, rate of climb 2500 ft/min, Estimated Complete Cost: $150,000 – $200,000 USD. The one deal breaker for you might be an estimated 70mph stall speed. Check it out if you haven’t already.
Yes, the DarkAero project is quite interesting on a number of fronts, not least the approach the brothers are taking in terms of using extensive computer modeling, innovative construction methods and consideration of kit production from the outset. Their Youtube videos and social media postings are very informative and help to differentiate them from the typical experimental aircraft developer.
You are correct that the high anticipated stall speed is a concern for me, as it the use of an engine which is not very well known in North America. In my mind, as engine reliability certainty decreases, so should the stall speed. A high stall speed coupled with a less well known engine is a combination that increases my perception of risk.
Another design which is still in the “coming together” stage which is of interest is the Veloce 600 https://veloceplanes.com/600/. This is a twin-engine, turbo charged and pressurized design for which the developers are claiming impressive anticipated performance. However, it is not as far along in the development process as the DarkAero and in my mind, has targets which will be challenging to meet.
For both designs, much remains to be demonstrated during and after the prototype flies and in both cases, successful kits will require manuals, manufacturing capability and support.
All that being said, for both companies I am looking forward to the results of the prototype test flights and wish them every success.
Hi David & All,
Loved both articles and voices, Luke is right, we can’t stop pushing. I have to admit Charlie has a point about continuing to eat and breath. I would love to hear your comments an the Veloce, 4 seat speedster flying for some years now. They have planned 300hp turbo 2.0L Mogas engine they hope will do the impossible by increasing performance decreasing cost and pilot work load while maintaining reliability. Is this possible in your opinion and to what extent does their outline seem likely to provide these outcomes?
Thanks for the kind words.
The Veloce 400 looks like an interesting airplane and the 300hp turbocharged flavor offers respectable cruise at altitude, based on their published performance figures.
That being said, I have not yet read an independent flight evaluation of the aircraft to verify the performance figures and flight characteristics. As you know, many aircraft have historically had difficulty matching the numbers in the marketing materials. This may or may not be the case here and I look forward to reading an independent review in the future.
The Veloce 600 also looks quite interesting, but at this point, the prototype has not yet flown, so there are some big unknowns about its real-world performance and flight characteristics.
However, in both cases, the peak published performance is associated with nontraditional engines. This could work out fine, but many alternative (i.e. not Lycoming, Continental or Rotax) engines have experienced challenges in the field. For example, automotive derivatives have great promise on paper and seem like they should be cheaper, more powerful, more fuel efficient and more reliable, but I am not aware of any which have actually delivered on that promise in numbers which are statistically compelling. Some recent work by Ron Wanttaja indicates that when you look at experimental aircraft accident statistics, if an experimental aircraft with an automotive conversion engine is involved in an accident, 44% of the time, the accident involves a power failure. This compares to 27% for those powered by traditional aircraft engines. Turbine engines also ought to be quite reliable, but in practice in experimental aviation, the accident statistics do not bear this out. In many cases, this may not be the fault of the engine itself, but something in the installation, accessories, cooling system, electrical supply, etc. but the bottom line is the same. Note that the above statistics are a very broad bucket (“automotive conversion”). Some are obviously much better than others and it may not be fair to put the better performing ones in the same category. However, it seems like a good idea to me to have a hard look at any non-traditional engine before deciding to put it in an aircraft and especially as the stall speed starts getting above 40-50 mph, where safe off-airport landings become more challenging. With any new design there are risks; even if rigorous engineering analysis is carried out in the design phase, there can be problems which only become apparent with multiple units in the field accumulating real-world hours – which is why there are things like STC’s (for certified aircraft) and automotive recalls. For many experimental aircraft, the number in the field is limited, so this real-world experience is not very deep. This is just part of the package with these kinds of aircraft. Combining a new airframe with a non-traditional powerplant means dealing with two relative unknowns; an airframe with little real-world experience and an engine with little real-world experience. Again, this is part of the package and is what experimental aviation is all about, but a prospective builder would be well advised to go into this kind of project with their eyes wide open.