Let’s Get High… Really High, OK? Exploring the “Upper Atmosphere” in a Pipistrel Motorglider

Probably like a lot of you, I enjoy different kinds of flying but if asked to state one favorite, it’s an easy question to answer.

I’m a great enthusiast of soaring flight. Over decades of sampling a large number of aircraft of every description, I’m still drawn to a machine, which lacking any kind of powerplant, relies on the performance of the design and the skill of the pilot to stay aloft. I remain fascinated with locating rising columns of heated air. Circle well enough into one of these invisible thermals and you may be rewarded with an invigorating sensation of lift, of riding the swirling airmass thousands of feet into the air …silently. It’s mesmerizing to observe the ground fall away as you are propelled higher and higher.

You may never have felt such thing and you may be hesitant about launching into the air in an aircraft that will allow only one approach and landing per flight; no exceptions. However, for those entranced by manipulating wisps of air to rise upward, a machine like Pipistrel’s Sinus is a thing of beauty.

Though awkwardly named, to English speakers at least, Sinus boasts long and slender but very hard-working wings that permit this SLSA motorglider to glide 27:1, giving the ability to reach more than 10 miles from only 2,000 feet above ground (assuming no lift or sink). Even if you don’t care about soaring, a glide path that flat can get you to a safe landing in many more situations.

Want to learn more? Let’s take a sample soaring flight. Even better, let’s investigate wave soaring.

Riding the Wave

Some years back I flew with Pipistrel dealer, Robert Mudd, to more than 17,000 feet. Conditions would have allowed us to soar even higher but at Flight Level 180, you enter Class A airspace and we were not prepared for that. Lift was abundant, though, so we had to go find sinking air to stay out of controlled space.

You can read my full pilot report on Sinus; most information remains relevant but some specs and all pricing has changed. Check for Pipistrel dealers for current prices and for used aircraft availability.

Robert continues to be a soaring enthusiast, hailing from New Mexico. He relates the following story about flying a wave near Albuquerque. If you aren’t sure what wave is, read on.

Knowing about waves can help you better negotiate mountain flying.

Roger wrote, “A local glider pilot, John Wahl, has been forecasting mountain wave for the Moriarty, New Mexico area but never getting much real feedback as to the accuracy of his predictions.” Mountain waves form when moving air rises over mountainous terrain. As the air rushes up the slope, layers above repeat the lift. Upper air is pushed aloft by the lower atmosphere climbing a mountain’s windward side*. See nearby diagram and learn more about wave soaring.

Robert continues, “In late October 2021, he forecast wave for a Saturday so I borrowed Hugh Bivin’s Sinus, N21PX, and took John along to see if the wave would be as forecast. We had his plots of where it should start and end geographically. We had oxygen, a data logger, warm clothes, and a sense of adventure.

“We took off about 10:15 AM and climbed west-northwest under Rotax power. Our home field elevation is 6,200 feet.

“The orientation of the wind aloft was not the best for wave to form. An ideal wind direction is 260 to 280 degrees so as to be perpendicular to the Sandia mountains, which rise to 10,500 feet. The wave was forecast to be at the northern end of the Sandia range, and be at an angle to the mountains. Wind aloft was about 230 degrees, not ideal by any means. This would be a good test of John’s forecasting method.

“We saw a line of clouds had formed along the forecasted direction. We got to the upwind side about 15 miles west of Moriarty and turned to run parallel to it. These were the roll clouds [sometimes associated with wave conditions] but really did not look much like a traditional roll cloud. They were just a line of not very tall cumulus. But we started to see an increased climb rate some distance upwind of them. We were about 8,500 feet above sea level. I slowly brought the power to idle but we did not climb, so I returned back to climb thrust. A short time later I tried that again and we found ourselves climbing with idle power. I shut off the motor and feathered the prop. We were still climbing! It became very quiet.

“We continued on a north-northwest track, climbing modestly at about 1.5 to 2 knots, about 150-200 feet per minute. The forecast was for stronger lift ahead so we continued. Sure enough, just where John had forecast stronger conditions, we found that. The best climb rate we saw was 3 knots or about 300 feet per minute. We stopped the climb at 17,910 feet. We could have gone higher, I think to at least 20,000 feet, but the wave window was not open.

“John was very happy, as was I. His forecast was validated under unusual conditions.

“We turned around and more or less followed our track back, still in wave, but staying well below 18,000 feet.

“The view was fantastic. As we flew out of the region of better lift we started a long slow decent and turned slightly to the southeast toward home.

“We landed after 1.25 hours of flight time, about an hour of which was power off. Naturally, the landing was done power off. As we cleared the runway I un-feathered the prop, started the motor and taxied to the hangar.

“This flight could not have been done except in a motorglider, and the fact it was done in a Sinus made it all the more interesting. I figured we used about 3 gallons of fuel. The flight was not just for fun but to validate John’s forecast model; so there was a strong sense of accomplishment and satisfaction.

“This illustrates the potential of research that can be done in a touring type motorglider. Because both pilot and researcher were side by side, coordinating the flight path was easy (unpowered sailplanes almost always have tandem seating). We were able to motor right to the area we wanted to explore, and, of course. always had a safety out with the motor.

“All in all, it was a flight to remember for the research, fellowship, and the fun of it.”

—Robert Mudd, October 2021

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TECHNICAL SPECIFICATIONS
Pipistrel Sinus
LSA Motorglider

• Wingspan — 49 feet, 1.5 inches
• Wing Area — 132 square feet
• Length — 24 feet, 1 inch
• Height — 6 feet
• Maximum Takeoff Weight — 1,213 pounds
• Standard Empty Weight — 644 pounds (typical weight 661 pounds)
• Useful Load — 569 pounds
• Payload (with full fuel) — 471 pounds
• Stall Speed (best flaps) — 35 knots
• Maneuvering Speed — 76 knots
• Maximum Rate of Climb — 1,063 feet per minutes at 62 knots
• Minimum Sink Rate (a key soaring term) — 217 feet per minute
• Takeoff Ground Roll — 433 feet
• Glide Ratio — 27:1
• Power Cruise — 110 to 115 knot with 80 horsepower Rotax 912
• Fuel Capacity — 15.9 gallons
• Fuel in optional long-range tanks — 24. 6 gallons
• Fuel Consumption — 3.1 gallons per hour at 110 knots
• Configuration — Available in tail dragger or nosewheel
• Endurance — up to 7.5 hours
• Maximum Range — 850 nautical miles
• Propeller — Feathering propeller option (approved for LSA motorgliders)
• Cockpit Width — 44 inches
• Baggage — 55 pounds capacity with external access option

* You can also soar leeside wave but this is for experts only.

Here’s our video with Rand Vollmer. Hear from a Sinus expert about this high performing LSA motorglider.

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