The tail rotor pushes back with four hundred pounds of sideways force.”

Ethan looked up from the plastic model to Henry’s face, staring at the straight line of his son’s nose.

“Who taught you that?” Ethan asked.

“I read the technical manual at the public library,” Henry said.

“Mom checked it out for me three times.”

Ethan didn’t answer for several seconds, his eyes resting on the small plastic turbine intake on top of the model.

“I worked with flight contractors in San Diego four years ago,” Ethan said, his voice dropping to a flat, quiet tone.