The Department of Defense, through the Defense Logistics Agency (DLA) Aviation at Philadelphia, PA, is seeking to procure four units of a heat exchanger (NSN 7R-1660-015126501-QE, REF NR 1001441-1) critical for aircraft air conditioning, heating, and pressurizing systems. This procurement requires engineering source approval due to the flight-critical nature of the item, necessitating that only approved sources may submit proposals, as the technical data necessary for full and open competition is not available. Interested parties must provide detailed technical data and qualifications in accordance with the NAVSUP Weapon Systems Support Source Approval Information Brochures, with a submission deadline of 45 days from the notice publication. For inquiries, contact Isabella Perrins at (215) 660-7088 or via email at ISABELLA.PERRINS@DLA.MIL.