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Project Spearhead

Project Spearhead is Arrow's ~25 kg MTOW hybrid fixed-wing VTOL aircraft project. It is a quadplane-style platform: electric motors provide vertical takeoff and landing, while an internal-combustion pusher engine is intended to provide efficient cruise flight.

Spearhead is aimed at long-endurance missions such as survey, rural surveillance, and light cargo. Just as importantly, it is a hardware learning platform for Arrow: the project builds real experience with fixed-wing aircraft sizing, hybrid propulsion, transition flight, long-range telemetry, and larger aircraft systems — a deliberate step on Arrow's path toward bigger aircraft.

These docs are a living engineering record. Spearhead is in active prototype development, so details will change as the team builds, tests, and learns. Treat the DAO proposal as the project charter and these docs as the current state of execution.

Project goals​

Spearhead is intended to develop and validate:

  • Aircraft sizing and structural integrity for a 25 kg class fixed-wing VTOL aircraft.
  • Hybrid propulsion using electric VTOL motors plus an internal-combustion pusher engine for cruise.
  • Generator integration, cruise battery-charging strategy, and energy management.
  • Hover-to-cruise and cruise-to-landing transition control.
  • Internal-combustion engine vibration mitigation and avionics protection.
  • Long-range telemetry, including RF and possible satellite-based links.
  • Modular payload support for surveillance and limited cargo use cases.
  • Safety and failure handling for lost-link, engine-out, and long-range operations.

The goal is not a polished commercial aircraft in the first pass. The goal is a capable prototype platform and the internal know-how needed for future larger systems.

Where the project is now​

Phase 1: the PT1 prototype build is underway in Ankara, Türkiye (as of July 2026). PT1 is the electric-only validation aircraft — the internal-combustion cruise system comes later.

Current work includes:

  • Airframe construction: laser-cut plywood ribs and spars, carbon-fiber structure, Oratex fabric skin, and 3D-printed structural connectors.
  • Electrical harness assembly per the electrical master document, with a fully connectorized, bench-tested-first approach.
  • ArduPilot QuadPlane configuration on a Pixhawk flight controller, plus SITL simulation work.
  • Aerodynamic and flight-dynamics analysis (see the information notes).

Because the aircraft is still being validated, requirements and component choices are provisional unless captured in a dated document.

Roadmap​

The proposal defines four broad phases:

Phase 1: Electric flight validation​

Build and test the full airframe with electric VTOL propulsion only. This validates hover stability, control-surface authority, structural integrity, and the wing detachment system before adding the complexity of the internal-combustion cruise system.

Phase 2: Hybrid integration​

Install the internal-combustion pusher engine, fuel system, cooling, and related hybrid hardware. Focus areas: static engine runs, temperature and vibration measurement, flight-controller filtering, VTOL–cruise transition, cruise flight, and battery sizing.

Phase 3: BVLOS and long-range testing​

Expand from short-range testing toward long-range flight profiles: telemetry range, link latency, command reliability, lost-link behavior, recovery protocols, and environment awareness.

Phase 4: Operational tailoring​

Refine the platform around specific mission configurations, including cargo and surveillance pods. This phase should produce clearer operating limits, payload/range tradeoffs, and a performance manual while transferring Spearhead lessons into future larger aircraft work.

How these docs are organized​

  • Engineering documents such as the electrical master document carry a doc ID, revision, author, and date. They are the authoritative specification for their subsystem.
  • Information notes (information-note/) are dated design and analysis notes, organized by phase and discipline (aerodynamics, flight dynamics).
  • Reference guides (reference-guide/) collect stable technical reference material, such as the ArduPilot QuadPlane reference.
  • Planning notes (such as the PT1 electrical planning note and parts list) capture build-cycle execution detail.

When documents conflict, the newer dated document wins.

Contributing​

Useful contributions right now include:

  • Reviewing aerodynamic sizing, stability analysis, and transition risks.
  • Improving ArduPilot QuadPlane, SITL, and simulation setup notes.
  • Researching propulsion, generator, telemetry, and payload-system options for the hybrid phases.
  • Helping define ground-test, taxi-test, and first-flight checklists.
  • Turning meeting discussion into clear dated decisions and documentation.

See the contributing guide and join the Arrow Discord — Spearhead has a weekly technical call and active build discussion.