Gliding the Polar Vortex – The Perlan II

The Windward Performance Perlan II is a one-of-a-kind high altitude glider. Designed to fly closer to the edge of space than any other crewed aircraft, record breaking high altitude flights will resume in the coming months, with the goal of the glider of reaching 90,000 feet above the earth. There’s a lot of history leading up to where the project is today, and when you see what has already been achieved, one can get a sense that soaring seventeen miles up in the air isn’t so far-fetched.

First of all, there have been a pair of Perlan gliders. The original Perlan I was designed to research mountain waves… the rivers of air that flow over the earth, well above ground level. Einar Enevoldson, an aviator with extensive experience as a test pilot for the US Air Force, Great Britain, and NASA, developed a plan to study the waves in the tropopause.

While most of the streams are found at lower altitudes in “temperate latitudes”, the waves extend much higher in polar regions. Planning began in 1992, and the so-called “Perlan Project” first glider was modified for duties in 1999. Famous balloonist Steve Fossett joined Einar on the team as the second pilot, and a Glaser-Dirks DG-500 motorized glider was modified as a pure glider for the flight program.

Among the experiments that the Perlan I and crew flew was to prove Enevoldson’s thesis of using the mountain waves to climb to unprecedented altitudes. In 2006, a world record of 50,671 feet of altitude was reached by the duo in the Perlan I glider, and served as proof of the gliding concept. Part of the Program is to track holes in the Ozone Layer near the South Pole, and these flights will operate from Argentina. Others flights will operate in U. S. airspace over the Rocky Mountains.

A further program to make a more capable high altitude glider was launched soon thereafter, being designed by Greg Cole and built by the Bend, Oregon’s Windward Performance company. Unfortunately, Steve Fossett was killed in an aviation accident in September 2009 (not associated with the Perlan I/II Programs), and the project stalled for lack of funding. The partially completed, improved glider was known as the Perlan II. Since then, several funding methods were used to get the project rolling again, and in 2014, Airbus became the principal sponsor.

The robust airframe of the Perlan II was built to withstand +6/-4 Gs, with a long wingspan of approximately 83 feet and a fuselage length of only 33 feet. Fully built of composite materials, the crew capsule is pressurized while at sea level, and the crew of 2 does not need to wear bulky pressure suits. It will be towed to a medium altitude by a specialized aircraft (more about that in a few minutes), then release from it and continue its climb.

The Perlan II first flew in 2015, at Redmond, Oregon. Flight testing began over Nevada in 2015, moving to Argentina in 2016. Einar Enevoldson was still a flight crew member in the Perlan II Project, although there were more pilots involved than those in the Perlan I campaign.  Various crews claimed more altitude records in 2017 and 2018. On September 2, 2018, Jim Paine and Tim Gardner soared to 76,124 feet, some 2.400 feet higher than the official altitude record made by a Lockheed U-2… it became the highest subsonic flight recorded and certified by the FAI – Federation Aeronautique International.

Today’s Perlan II Project is focused on three missions: Innovation, Science and Inspiration. According to their web site, their Innovation is: “We explore the largest waves on the planet – stratospheric waves energized by the polar vortex. These waves play a primary role in creating the ozone hole, distributing pollutants around the globe, and mixing the stratosphere in ways that impact global weather. Our research is allowing scientists to better understand the dynamics of climate change.” 

Their Science is: “We aim to extend wing-borne flight to unprecedented altitudes. Our current goal is to reach 90,000 feet and become the highest-flying wing-born aircraft in human history, all in a zero-emissions research plane that doesn’t pollute the atmosphere”. The Perlan II Project’s web site notes that the design operates “most efficiently” at 50,000 feet, but it can operate “exceptionally well at both sea level and at 90,000 feet”.

 Finally, their Inspiration is: “We want to show the next generation of scientists, engineers and aviators what can be accomplished by a small, passionate team of volunteers.”

The specialized one-of-a-kind glider is carried aloft by another specialized aircraft, the rare Grob G-520T EGRETT (named after its three developing companies of E-Systems, Grob and Garrett). The current G-520T version is a two-seat high altitude, long duration motor-glider, powered by a Honeywell TPE-14F turboprop engine. The propeller used to assist the aircraft up into high altitudes is 10 feet in diameter! The optimum mission altitude of the EGRETT is around 50,000 feet, where the glider will release and begin to soar to higher altitudes.

The G-520 was originally a single seat design for a joint German Air Force/US Air Force long-endurance, manned reconnaissance platform.  The design began as the D-450 EGRETT I, and the follow-on D-500 EGRETT II. Although the full military program was terminated, 6 G-520Ts (the ultimate two-seat version) were built, and sensors were fitted for testing the concept in any event. The design is the largest high – altitude turboprop in the world, and holds multiple world performance records in its class, including a maximum altitude of 53, 329 feet.  The aircraft is fitted with 12 equipment bays for sensors and other cargo, capable of carrying a staggering total of 850 kg (1874 pounds) of equipment, along with two crewmembers in the pressurized cabin. Today, the sole active D-520T airframe is operated by Av Experts, LLC of Dennison, TX.

A short flight demonstration by both the Grob D-520T EGRETT II and the Windward Performance Perlan II glider was performed at the EAA’s 2022 AirVenture Oshkosh show. The Grob, with the glider in tow, departed and climbed a few thousand feet in front of an afternoon air show crowd. A pass with the glider in tow gave photographers a great opportunity to see this rare combination joined only by a tow cable.  After release, the Perlan II gracefully made a few circuits and landed, while the Grob EGRETT II made more passes without the glider in tow.

In contrast to the low-altitude passes in Wisconsin, the two aircraft will operate in South America while attempting to attain the program’s goal of soaring to 90,000 feet in altitude. Soaring over Argentina’s Patagonian Mountains, the Grob tow aircraft will climb for more than an hour to place the Perlan II glider in the right place for a release and climb. The Grob is not RVSM equipped, but with a waiver, it can operate in the same airspace as civilian operators. The soaring operation will take place away from any non-participating aircraft, allowing for carefully planned profiles. Plans for an assault of the altitude record are anticipated to occur around mid-2023, during optimal seasonal weather in Argentina.

The Perlan II glider has already soared to more than 80 percent of their goal of 90,000 feet. Some sources report even 100,000 feet could be attained. If all goes well in 2023, the aviation world may well see some new high-altitude aircraft records. Any glide above 76,124 feet will better the Perlan II’s previous glider record. But just think about this…  Lockheed’s SR-71A Blackbird holds the world’s absolute altitude record for sustained flight by a manned aircraft at 85,069 feet (officially). Now there’s a contrast, a definitely subsonic glider besting the world’s fastest jet aircraft in some performance measures. With help from Av Experts’ EGRETT II, the Perlan II glider may soon break the coveted altitude mark.