StopRotor Aircraft

Fixed wing & helicopter performance in a single aircraft

The StopRotor is a new aircraft capable of both rotary & fixed wing flight.

The design combines the utility of the helicopter rotor system with the performance and efficiency of fixed wing flight.

The unique design and method of operation enables inflight transition between modes and where the central wing is utilised as either a rotating or fixed wing.

The aircraft retains the industry proven, centrally mounted, two bladed helicopter rotor system backed by almost 100 years of research and development.

This enables robust performance in a wide range of environmental conditions and uniquely for the StopRotor aircraft; optimisation of the rotorwing for VTOL performance also favors fixed wing performance. As identified by DARPA 2013, hover efficiency of rotorcraft is only 60% of the theoretical ideal due mainly to the compromise to achieve forward speed performance.

Flight capabilities:

  • VTOL
  • Hover
  • Conventional & Short TOL
  • Fixed wing flight
  • Compound / rotary flight
  • In-flight transition between modes

This combination in a single aircraft offers unprecedented flight capabilities.

StopRotor Aircraft Design

This aircraft design is a new solution to in-flight transition between rotary and fixed wing flight modes enabling stopped rotor aircraft designs.

A new aircraft type means new opportunities for the aerospace industry:

  1. World first research opportunities
  2. A new solution for civil and Defence applications
  3. Unprecedented flight capabilities in a competitive market

In-Flight Transiiton

The StopRotor Innovation

The use of high alpha flight controls to provide axial airflow to the rotor system enables transition between flight modes.

The StopRotor design combines conventional flight envelopes with controlled, sustainable flight at high angles of attack to achieve axial airflow allowing aerodynamic control of the RotorWing to stop or start enabling transition between flight modes.

UAS P/L  has focused on simplicity of design to provide an aerodynamic solution to enable stop rotor operations that can be applied to larger aircraft platforms. Flying prototypes have been used to demonstrate this concept.

The aerodynamic transition is viewed the same as an aerobatic manoeuvre, using vertical space to complete.

Once the transition is complete the aircraft is flown out of the transition envelope and resumes normal fixed or rotary wing flight.

High Angle of Attack (high alpha) flight is routinely performed by high performance military and aerobatic aircraft.

The StopRotor design is a new solution for a VTOL aircraft. Review VTOL Prior Art.

Features & Benefits

The most useful aircraft in the world would take off, hover, and land like a helicopter but fly as fast as a plane. Australian Popular Science Feb 2013

A StopRotor aircraft combines the ideal flight characteristics of the two most successful aircraft types in the world; the helicopter and aeroplane.

StopRotor Flight

Helicopters are the most efficient VTOL capable aircraft known today.

The most efficient helicopters have large, slow turning rotors which provide optimum vertical lift. The requirement to achieve forward flight means that the rotor system vertical lift efficiency has to be compromised to generate aircraft movement and provide a useful flight envelope.

Large, efficient rotors are subject to early onset asymmetric airflow limiting their forward flight capability. To solve this problem vertical lift capability is reduced in favour of designs that favour forward speed. Faster spinning, shorter rotors provide the control necessary for helicopter flight, but still suffer from the effect of asymmetric airflow as speed increases. As a result of asymmetric airflow, the fastest helicopters achieve speeds of around 180 knots. DARPA X Plane program identifies that hover efficiency of rotorcraft is only 60% of the theoretical ideal due mainly to the compromise to achieve forward speed performance.

A StopRotor aircraft overcomes the limitations of a helicopter in forward flight by stopping the rotor and thus can use a rotor system that can be more efficient in hover while allowing high speed, forward flight as a fixed wing.

Transition Profile

The Hybrid RotorWing transition profile is a paradigm shift but provides a stable predictable flight mode that allows reversible conversion in a controlled and sustainable manner between rotary and fixed wing modes of operation. The transition profile can be completed in multiple attitudes with a brief trade off in energy and or altitude. This profile is the key enabling feature that unlocks the potential of a StopRotor aircraft.

The RotorWing

The RotorWing of a StopRotor aircraft is unique:

  • It can be optimised for hover performance which also favors performance as a fixed wing. ALL other VTOL aircraft must compromise between efficient rotary and fixed wing flight.
  • It can be optimised as a higher inertia rotor aiding autorotation performance.
  • It allows a rotor disc loading similar to or lower than a conventional helicopter.
  • Low rotor disc loading minimizes rotor down wash and ground erosion.
  • The RotorWing does not require high blade twist to generate forward thrust in fixed wing modes of operation.
  • It allows for potentially both single or multiple RotorWing configurations
  • It can be designed to favor hover performance or maneuverability subject to the predominant flight mode.

Multi Role Aircraft

The StopRotor aircraft provides a wide range of performance capabilities, enabling diverse mission profiles, in-flight adaptability and allowing high speed, long range access to remote unprepared landing sites.

For a helicopter style mission that involves hovering flight the aircraft would be operated as any other conventional helicopter where the rotor provides the lift and thrust requirements for vertical and horizontal movement.

For short range missions the aircraft would be operated as compound helicopter where the rotor would be unloaded but not stopped with wings and forward thrust engine assisting in forward flight. At the destination the aircraft would revert to helicopter operations for a vertical landing or perform a short field landing as required. For long range high speed flight, the aircraft would convert to a fixed wing to take advantage of its high speed, high altitude capability allowing operations above weather like any other fixed wing aircraft. At the destination a conversion to rotary wing mode can be achieved for vertical landing or a conventional runway landing can be made whilst in fixed wing mode.

Mission Adaptive Flight

The Hybrid RotorWing is capable of conventional (CTOL), short (STOL) or vertical (VTOL) take off and landing operations. The design provides the ability to adapt and respond to changing requirements;

  • Conventional runway based operations as a fixed or rotary wing aircraft (CTOL)
  • V/STOL operations to prepared and unprepared landing sites on both land and water
  • Unique payload mission versatility and adaptability
  • In-flight transitions between rotary and fixed wing flight

Aircraft Design

A practical design preserving valued attributes of both rotary and fixed wing aircraft including;

  • Flexible design parameters
  • High speed, efficient fixed wing flight allowing operations at high altitude over long range
  • Optimised vertical performance without the need to compromise for forward flight

Failsafe Operations

The Hybrid RotorWing design allows the familiar fail safe operations of  both rotary and fixed wing performance

  • Auto-rotative performance in rotary mode
  • Fixed wing glide