Meet the Esprit – a twin-engine ultralight motorglider.
Soaring enthusiasts who want to self-launch their aircraft are limited to simple hang gliders on one end and expensive motorgliders on the other. Performance for these machines ranges 15:1 to 50:1. To get one you’ll spend $5000 or $200,000. What you could not do is spend $20,000 to get medium performance*… until now.
Debuting his machine at AirVenture 2000 airshow, Dobro Hajek brings a modern soaring aircraft to the ultralight community. I believe he will also find significant interest from two other groups: sailplane and hang glider pilots. Each loves dedicated machines without engines but many will also prefer an aircraft that can launch itself.
With its distinctive compound-tapered wings and winglets and its dual engines with folding props, the sleek Esprit goes a long way past the Aero Dovron that Hajek (pronounced HAY-yek) once imported. The Straton D-8 was an interesting little motorglider with a high wing and struts but at 17:1, this inexpensive machine didn’t have the go power it needed to attract a solid market in the United States.
Hajek changes that with the Esprit. At 26:1 calculated performance, this aircraft offers excellent glide for its speed range and a sink rate computed to be less than 170 fpm. These numbers are sharp improvements over predecessors and puts the Esprit in a new league. As Hajek logs more hours and after he makes minor adjustments to the prototype, he will hand Esprit over to a professional test pilot who will put it through an evaluation regimen to confirm glide ratio and sink rate performance.
An aerodynamicist, Hajek’s description of Esprit’s performance sounds like an engineer rather than a marketer and one gets the feeling it may come close to the calculated figures.
Draw back from the Esprit and it looks all the more sailplane-like with its curved cockpit pod connected to a tapering tail boom that is topped with a modern looking T tail. In flight, the long, slender wings lend a graceful appearance that pilots find pleasing. As it passes overhead, you cannot see the engines nestled into the wing’s upper surface. Their noise is surprisingly low.
Two Solos Make One Soaring Flight
The tiny Solo engines produce only 15 hp each, but their combined push lifts the Esprit into the air vigorously at a claimed 1000 fpm. Though I have yet to fly Esprit, it did not appear to have any difficulty with the sometimes-challenging ultralight airstrip at Oshkosh.
Landing was another matter. Hajek spoke of the vexing conditions at this year’s airshow when, day after the day, a stalled low front caused north winds of 15-20 mph. At AirVenture’s ultralight strip, this translates to a near-90*deg*crosswind. While the Esprit can handle the crosswind from a control standpoint, says Dobro, it naturally prefers landing into the wind to achieve its minimum rollout of 350 feet.
A combination of the bumpy turf strip and lack of headwind caused Hajek to make three passes on one breezy day. With no headwind to slow him down, Dobro relaunched a few feet into the air with every bump in the strip and used nearly the entire runway to bring the sleek motorglider to rest. In most situations this problem would not exist and even so, the Esprit proved itself able to operate from the 1500-foot strip.
The twin Solo engines will prove even more capable for soaring flight. Adapted from a certified German setup, Esprit’s folding props align with the wind whenever the power is sufficiently reduced, thanks to strong springs. As each of the little engines has an electric starter, firing them up for the trip home should be easy after Hajek makes one more change: He will install a remote compression release to allow for easier cold restarting of the engines. Even with a high compression ratio, the Solo engines restart easily when warm, Dobro reports, but they resist when cool. On a good day of soaring, with the engine off for perhaps several hours, a cooled engine will often be the case.
The engines were valued for their high power-to-weight ratio but they required many small changes to suit Hajek the perfectionist. He altered the carburetor, fuel pumps, muffler and engine mount. In the weeks ahead he will also install the compression release, lighten the folding prop hub, and lighten and improve the belt drive and its mount. Currently a Hirth reduction drive is used, but Hajek feels he can make a better one.
“The airframe design is frozen,” says Hajek. He’s pleased with the all-aluminum aircraft and its D-cell spar. Covered in the center section with sheet aluminum, the outer two thirds of each wing are fabric covered.
Handsome and Clean
Every time I walked by the strategically parked aircraft at AirVenture, several pilots could be seen poring deeply over the many innovations Hajek has added to his dream machine.
He expects the airframe kit to sell for $12,000 and the twin Solo engines cost $3000 each. Even with accessories like the BRS emergency parachute system that Hajek installed in his prototype Esprit, you should get airborne for $20,000. Though this is three times the cost of a modern hang glider, it offers twice the glide and does so for 10-20% of the cost of a full-size motorglider.
Although elegant machines like the Stemme offer 50:1 glide for $200,000, the Esprit is a far better deal at $800 per glide point compared to the Stemme’s $4000 per glide point. (The hang glider wins this price/performance comparison at a mere $400 per glide point.)
I’ve known Hajek from many conversations over several years, and I have found him honest and knowledgeable, a wonderful combination in the sometimes uncertain world of sport aircraft producers.
Since a Part 103 Esprit is supposed to qualify under FAA’s simplest rule, Hajek’s company can fully build the Esprit for you. This will cost extra, of course, but at perhaps $25,000 fully equipped and ready to fly, this is a still quite a bargain in the world of smooth soaring machines.
I can’t wait to get my hands around the controls of the Esprit. Maybe you feel similarly.
|Empty weight||254 lb|
|Gross weight||485 lb|
|Wing area||105 sq.ft.|
|Useful Load||231 lb|
|Payload (with full fuel)||201 lb|
|Load Limit||+4, -2 G|
|Fuel Capacity||5 gallons|
|Power||Solo, 15 hp each|
|Max Speed||80 mph|
|Cruise speed||65 mph|
|Stall Speed||25 mph|
|Rate of climb at gross||1000 fpm|
|Takeoff distance at gross||250 ft|
|Landing distance at gross||350 ft|
|Min Sink Rate||168 fpm, calculated|
|Glide Ratio||26:1, calculated|
Peter Vigar says
I am very interested in this aircraft , where and how can I buy one, I live in South Australia, regards, Peter Vigar
Dan Johnson says
Hi Peter: Regretfully we have not seen this handsome aircraft for many years. I fear you are out-of-luck.