Toyota Technical Center U.S.A. Inc. Executive Engineer David Hermance died Nov. 25 when a small plane he was piloting went down off the coast of California.

Hermance, in charge of Advanced Technology Vehicles for Toyota and regarded by some as the man responsible for bringing a more competitive version of Toyota’s hybrid-electric Prius car to the U.S., reportedly was flying an Interavia E-3, a 2-seat Russian aerobatic plane, near Los Angeles when witnesses report it dove into the water after performing a series of loops.

The wreckage of Hermance’s plane and his body were recovered the morning of Nov. 26, local fire officials tell the Associated Press. Hermance was believed to be the only occupant.

Hermance, a licensed pilot, was well known in automotive circles for his passion for hybrid vehicles and alternative technologies.

In August, he told Ward’s Toyota had recently seen its first “wear out” of a hybrid battery pack in a first-generation Prius with 180,000 miles (289,674 km) on it.

He was gleeful though that most Priuses had seen more use and their batteries were still going strong with 250,000 miles (402,352 km) of use.

Hermance joined Toyota in 1991 as a senior manager evaluating engines, then was promoted to a general manager in the powertrain department. In this role Hermance had responsibility for calibrating gasoline engines for the North American market.

Hermance was a diligent promoter of HEVs and was the point man for explaining the complex technology to the media and most other audiences. He also drew respect for the affable manner in which he addressed ongoing criticism of HEVs’ failure to deliver projected fuel-economy gains.

Under his guidance, Toyota deployed a more powerful and more fuel-efficient hybrid-electric powertrain for the Prius to the U.S. in 2003. Earlier models had not sold well but, with a speedier, more efficient second-generation North American version of the car, Prius sales grew to more than 100,000 units in the U.S. in 2005.

Before joining Toyota, Hermance worked for General Motors Corp. as an engineer for 26 years.

Hermance is survived by his wife, Mary, and two adult children.