H55 Demonstrates High-Density Altitude Electric Flight in Colorado, Showcasing Aircraft Performance in Extreme Conditions

H55, the electric aviation pioneer born from the Solar Impulse project, has completed a series of high-density altitude, high-temperature demonstration flights in Colorado as part of its Across USA Tour. These tests confirm the real-world performance of the H55 powered Bristell B23 Energic, illustrating the operational performance of electric aviation. 

Operating in Challenging Conditions

The Colorado mission flights took place from an airfield situated at 5,800 feet above sea level, with temperatures reaching 36°C (96.8°F) and a takeoff density altitude of 9,500ft. The B23 Energic performed flawlessly providing smooth, 500 feet per minute climbs using normal runway distance for departures. This “hot and high” scenario tests an aircraft’s take-off distance, climb performance, and overall efficiency. In contrast to conventional combustion engines which face degraded performance in such operating environments, the electric propulsion system of the B23 Energic delivered steady and reliable results. 
“Colorado offers one of the most demanding environments for aviation,” said Gregory Blatt, Co-Founder and Mission Director of H55. “This stop gives us a chance to demonstrate how electric propulsion is not only sustainable, but operationally consistent in conditions previously considered restrictive for many aircraft types. We’re especially grateful to Centennial Airport and jetCenters of Colorado for their warm welcome and support. Their commitment to innovation and sustainability reflects the shared mission of accelerating the adoption of clean aviation solutions.”

A First for Colorado

Centennial Flyers, a leading flight school based at Centennial Airport (KAPA), signed a Letter of Intent (LOI) during H55’s Colorado stop-over, becoming the first operator in the State to formally commit to adopting electric aviation. Their decision reflects the growing momentum across the U.S. for the Bristell B23 Energic, which continues to attract interest from flight schools, pilot individuals, operators, and regional airports seeking sustainable and cost-efficient training solutions. This engagement further strengthens H55’s expanding order book and underscores the market’s readiness for certified electric aircraft.

Proving Electric Flight in Real Environmental Settings

Electric propulsion systems face heightened scrutiny when tested outside of controlled environments. In Colorado’s hot, high-altitude climate, H55’s certified Electric Propulsion System (EPS) excels, maintaining optimal performance despite the challenges posed by both elevated temperatures and reduced air density. The system delivered consistent climb rates and demonstrated efficient battery cooling, proving that electric flight can operate effectively in diverse climates and geographies year-round.

Key Questions Answered in Colorado

• Can electric aircraft operate effectively at high-density altitudes? 

Yes—the B23 Energic performed in conditions of 36°C (96.8°F) and a 9,500 ft density altitude with stability and strong climb rates, at 500 feet per minute. 

• How does heat affect electric propulsion?

H55’s battery and EPS architecture performed within nominal thermal limits, with no signs of degradation despite high ambient temperatures, up to 40°C (104°F).

Advancing Climate Resilient Flight Training

As electric aircraft join training fleets, climate resilient performance is essential. The B23 Energic offers zero emissions, low noise, and minimal vibration—ideal for flight schools and airports under stricter environmental rules. Colorado illustrated flawless performance in conditions that normally strain conventional aircraft. With no performance loss or system degradation, H55’s EPS proves electric propulsion is ready for high-altitude, high-temperature flight.

Next Stop: Oshkosh

Following the Colorado tour stop, the Across USA Tour continues with its seventh stop at EAA AirVenture Oshkosh 2025 — “The World’s Greatest Aviation Celebration”. Attendees can learn more about the future of electric aviation at the 2025 Electric Aircraft Symposium (July 19-20), followed by the annual airshow (July 21-27) — a first for both H55 and Bristell BRM AERO.  A Bristell/H55 press conference will be held on Tuesday, July 22 at 11:00 AM CST at Booths 296-297. 

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