Principal Mechanical Engineer

Principal Mechanical Engineer (TS/SCI Required)Location: Reston, VALeidos is seeking an experienced Principal Mechanical Engineer to support high-priority national security missions in Reston, Virginia. This role focuses on the assessment, reverse engineering, and characterization of complex above-ground and subterranean facilities located in denied-access environments.The successful candidate will leverage extensive engineering expertise to analyze facility designs, spatial layouts, operational workflows, and supporting infrastructure to determine functional capabilities and mission relevance. You will evaluate facility systems, model critical infrastructure, identify vulnerabilities, and provide technical insights that support complex intelligence and defense initiatives.This position requires a highly experienced engineer who can develop sound technical assessments in situations where complete information is rarely available. The ideal candidate combines creativity, engineering rigor, and exceptional analytical skills with meticulous attention to detail. As a senior technical leader, you will work alongside interdisciplinary teams of government and contractor professionals while serving as a recognized subject matter expert in support of critical mission objectives.Work is performed in a fast-paced, mission-focused environment within a government facility.Primary ResponsibilitiesReverse Engineering & Facility CharacterizationAnalyze and characterize the physical and functional attributes of facility layouts, building architecture, and operational workflows within denied-access environments to determine facility purpose, capability, and operational capacity.Vulnerability AssessmentsEvaluate facility and infrastructure designs to identify security vulnerabilities, single points of failure, operational bottlenecks, and potential mission impacts.3D Modeling & SimulationDevelop high-fidelity 3D models and conduct engineering simulations to replicate facility operations, workflow efficiencies, and structural or mechanical limitations.Infrastructure AnalysisApply multidisciplinary engineering expertise to assess supporting facility systems, with a primary emphasis on Mechanical, Electrical, and Plumbing (MEP) integration and functionality within complex facilities.Technical Documentation & ReportingTranslate field-collected data, intelligence information, and engineering assessments into comprehensive technical reports, CAD/BIM products, and simulation-based analyses for Department of Defense stakeholders.Research & DevelopmentLead or contribute to customer-approved research and development initiatives, independently or as part of a multidisciplinary team, to advance analytical methodologies, modeling capabilities, and mission solutions.Technical Leadership & Subject Matter ExpertiseServe as a recognized subject matter expert within the organization and broader technical community, providing authoritative guidance and engineering insight to complex mission challenges.Required QualificationsActive TS/SCI clearance required. Must be a U.S. Citizen.Demonstrated mastery of advanced engineering technologies, scientific principles, theories, and concepts, with the ability to apply expertise across highly complex technical and mission-focused programs.Master's degree with 15+ years of relevant experience, or a Doctorate with 13+ years of relevant experience.Relevant experience includes facility analysis, infrastructure vulnerability assessments, and mechanical engineering within commercial, Department of Defense, or Intelligence Community environments.MEP Systems Expertise: Strong multidisciplinary understanding of Mechanical, Electrical, and Plumbing (MEP) system design, integration, and operational functionality within complex industrial or military facilities, including specialized containment systems, filtration systems, and backup power infrastructure.Ability to identify industrial HVAC equipment, estimate system size and capacity, and assess operational capabilities through visual analysis.Ability to evaluate, organize, and leverage large datasets from diverse sources, including field-collected data, equipment technical manuals, and existing facility models.Expertise in 3D modeling, engineering analysis, and physical simulation methodologies.Experience interpreting engineering drawings, facility layouts, blueprints, and intelligence-derived technical data.Demonstrated ability to make sound technical judgments with incomplete information while clearly communicating assumptions, uncertainties, and recommended paths forward.Preferred QualificationsFive or more years of field experience working with industrial HVAC systems, including air-cooled and water-cooled chillers, condensers, cooling towers, air handlers, heat exchangers, boilers, and related equipment.Working knowledge of air management systems supporting critical environments, including medical laboratories, clean rooms, chemical laboratories, and similar specialized facilities.Hands-on experience with advanced Building Information Modeling (BIM) and engineering simulation tools, including Autodesk Revit, VENTSIM, ETAP, and other industry-standard CAD and modeling platforms.Experience supporting forensic engineering investigations, industrial accident analyses, or Department of Defense facility vulnerability studies.Professional Engineer (PE) license and/or Project Management Professional (PMP) certification.Experience identifying mechanical system vulnerabilities and developing effective mitigation or corrective action strategies.If you're looking for comfort, keep scrolling. At Leidos, we outthink, outbuild, and outpace the status quo — because the mission demands it. We're not hiring followers. We're recruiting the ones who disrupt, provoke, and refuse to fail. Step 10 is ancient history. We're already at step 30 — and moving faster than anyone else dares.