Case Study: LOCKHEED MARTIN F-22 APU Intakes

Air vents for the F-22 which provided cooling of the APUs while sustaining extreme pressures at Mach 2.

The F-22 APU Air Intake Grill. Built to Withstand Airspeeds At Mach 2.


  • Complex Aluminum Forms
  • Uniquely Stronger Welds to Withstand Vibration
  • Constructed to Withstand Extremes in Temperatures

This very sophisticated design was a manufacturing challenge. Made from high-grade aluminum, the original design was soon discovered to react to air pressures at speeds above Mach 1, when the force of the air and the location of the vents created tremendous vibration of the louvers. The sound this generated, behind the cockpit, was so loud it could be heard in the cockpit through the pilot’s helmet.

ACE was assigned the re-manufacturing of the new design by our key customer Honeywell. Welding aluminum is very difficult due to the nature of the metal, rapid oxidation and porosity of the welds (due to imperfect conditions, such as high humidity). The louvers, or “fins” had to withstand the extreme conditions found at speeds above Mach 1: baking-to-freezing temperatures, expansion, tremendous wind force, vibration and air turbulence. This very heavy gauge construction was developed for and exceeded the demands required for the intake grill.

Built for Extreme Speed

You wouldn't think a passive vent cover would need to stand up to wind. But how about wind moving faster the Mach 1? These covers, redesigned to curb vibration, stood up to air blasting in at the speed of sound.

Every Component Custom Formed

Every single blade in the grill had slight variation in the shape. Subtle but distinct, each blade was hand-crafted and precision welded into place to meet very stringent specifications. The blades had to be exact to properly bring in the cooling air without succumbing to deafening vibrations.

Construction Which Rivaled Our Most Difficult Projects

Not only was intense attention paid to positioning the components exactly where they needed to meet the frames. Custom welding made the job that much more challenging because of the thin separation between the blades themselves.