Senior Mechanical Engineer - Stress Analysis

You are a hands-on Senior Structural Engineer owning aircraft structural analysis, system level Global Finite Element Models (GFEMs), and assembly level Detailed Finite Element Models (DFEMs). At Zipline you will apply first-principles analysis and tight design-test-analysis loops to keep our delivery aircraft safe, light, and highly available for continuous logistics operations. Your work directly affects aircraft airworthiness, fleet uptime, and mission success—increasing vehicle life, decreasing maintenance intervals, root causing & preventing in-field failures, and enabling higher payloads and range for deliveries. This role reports into the Structural Analysis Lead and operates across design, test, reliability, systems, and field operations and is based at Zipline's manufacturing and test lab facility in South San Francisco. Travel to field sites and test ranges is typically 5-10% depending on program phase.

How to know if it's you:  You’ve built your own prototypes to get quick answers, pencil and paper calculations are always your first step, you prefer simple and fast over detailed and large, you are on the floor during system testing, you have never presented a FEM plot without adjusting the legend scale . On any given day you could be building test articles in our composites/prototype labs, developing simple models to inform design trade studies, performing structural tests to validate analysis, working across disciplines to tackle complex system level challenges, root causing a test or field failure, or in the field supporting flight tests.

Zipline was founded by engineers dedicated to making the world a better place. We are building a new global industry and are looking for a talented engineer who takes a hands-on approach and will use analysis to drive design. The ideal candidate will be someone who excels in a fast paced, dynamic environment and is excited to own and drive simple, elegant solutions to complex problems.

• Own and maintain the top-level Global Finite Element Model (GFEM): set and enforce standards for material properties, numbering, interfaces, model fidelity, and validation procedures. Ensure GFEM is the go-to single source of truth resource for the team.
• Produce rapid analysis studies and design guidance: perform hand calculations and create lightweight beam/shell FEMs to drive design trades; deliver updated models and results within 24–48 hours to match evolving configurations.
• Structural sizing and certification support: perform static, dynamic, stability, and damage-tolerance analyses for metallic and composite primary/secondary structures; evaluate and optimize systems (flight and ground) for structural loads, vibration modes, and deflections; produce documented margin and load reports for qualification testing and regulatory artifacts.
• Test planning and correlation: define pre-test predictions, instrumentation plans, and post-test correlation workflows; tune models to test data and drive model agreement to within target tolerance (e.g., stiffness and key stress results within ~5% for validated modes and load paths).
• Failure investigation and corrective actions: lead root-cause investigations for test and field failures, generate corrective design changes, and work with manufacturing, design, reliability, and test teams to close actions and update inspection criteria.
• Cross-functional ownership and tooling: collaborate daily with design, systems, reliability, test, and flight operations; level up the company’s engineers by creating and documenting standardized in-house FEM tools, verification checklists, and model-release processes; mentor 3–5 contributors who feed into the GFEM.
• Field and flight-test support: support flight-test campaigns and field remediation events on-site, execute rapid test fixes, and prioritize fleet-impacting issues to minimize downtime and preserve flight schedules. Resolve test issues (hours) and provide corrective action direction for issues found in qualification testing
• Measurable outcomes you will be accountable for: reduction in product level cost per delivery, GFEM release cadence (e.g., weekly/monthly to match config updates), reduction in structural repeat failures across fleet, mass or margin improvements from design trades, and model-to-test correlation metrics.

• Minimum 5 years experience in structural analysis for aircraft or complex aerospace vehicles working with metallic, composite, and polymer structures; must have hands-on hardware experience
• Demonstrated ownership of a top-level GFEM or equivalent system-level model integrating multiple subsystem inputs; experience managing contributions from 3–5 engineers.
• Deep capability with industry-standard tools (examples: NX, FEMAP/NX Nastran, ANSYS, Siemens Design Center), and proficiency scripting in Python or MATLAB to automate workflows and reports.
• Solid classical stress and dynamics background: Roark/Bruhn-level hand-calculation fluency plus structural modes, random vibration, and forced-harmonic analysis experience.
• Proven track record of experimental correlation: defining instrumentation, producing pre-test predictions, and tuning models to match static/dynamic/flight tests within engineering tolerances.
• Must-have traits: clear owner mentality with rapid decision cadence, tolerance for ambiguity and shifting configurations, disciplined documentation habits, and the ability to identify opportunities to maximize impacts to cost, scalability, and fleet health
• Location: role is based in South San Francisco
• Must be eligible to work in the US

Zipline is an equal opportunity employer and prohibits discrimination and harassment of any type without regard to race, color, religion, age, sex, national origin, disability status, genetics, protected veteran status, sexual orientation, gender identity or expression, or any other characteristic protected by federal, state or local laws or our own sensibilities.

We value diversity at Zipline and welcome applications from those who are traditionally underrepresented in tech. If you like the sound of this position but are not sure if you are the perfect fit, please apply!