Principal Mechanical Design Engineer - Defence Sector

Location: Stevenage
Relocation Support: May be available
Salary: Highly competitive + strong package
Working Pattern: Hybrid (2-3 days on-site)
Clearance: Sole British Citizenship or Dual UK National (with British Citizenship)

Copello are partnering with a leading defence business to identify an experienced Principle Mechanical Design Engineer, who is ready to help shape the next-generation of defence technology. Our client—an industry front runneris expanding, and we’re supporting them in the search for experienced engineers who can take the lead on complex mechanical solutions across the full product lifecycle.
From early-stage concept development through detailed design, qualification, production and ongoing in-service support, you’ll be at the heart of projects that genuinely matter, working alongside elite multidisciplinary teams.

The Opportunity - Principle Mechanical Design Engineer
As a Principal Mechanical Design Engineer, you’ll take ownership of mechanical work packages that underpin some of the UK’s most advanced defence capabilities. You’ll lead design solutions for a wide range of complex systems while navigating the challenges of multidisciplinary collaboration and high-integrity engineering.
This is a role where your technical depth, leadership, and ability to influence across teams will make an immediate and visible impact. Outstanding development opportunities and long-term career progression are a natural part of the environment.

What expertise you will bring as Principle Design Engineer
*Degree/HNC/HND (or equivalent) with significant Mechanical Design and Development experience
*Proven ability to lead mechanical design work packages
*Experience working within multi-disciplinary engineering teams
*Awareness of proving, qualification and compliance processes
*Strong background in DFMEA, DFA, DFM and robust engineering practices
*Confident communicator able to influence and negotiate across teams
*Experience engaging suppliers and working across internal/external interfaces
*Ability to adapt to cultural differences and varying team dynamics
*Calm, professional approach with excellent prioritisation skills
*Knowledge of structural, thermal or dynamic analysis (advantageous)
*3D CAD/CAE proficiency (training available on preferred tools)

Additional Requirements as Principle Design Engineer
Due to the nature of the work, successful candidates must meet baseline personnel security checks (BPSS). Nationality restrictions apply in line with government security regulations.
If you’re driven by engineering excellence and motivated by work that directly supports national defence, this is an exceptional opportunity to step into a principal role with real influence.