Control Effectors, Flight Control, Flow control, Manoeuvre, Performance
The survivability of future manned and unmanned military vehicles will rely on surface geometries with smooth, continuous outer mould lines. Vehicle designs that do not involve ‘seams’, ‘gaps’ or moving surfaces have been studied in the past and continue to evolve. This requirement to be seamless invokes a very critical characteristic for vehicle control and suggests that new control effector strategies may be a requirement. In addition because the control power for any one control effector is limited, a suite of control effectors may be required to provide all envelope control of a vehicle.
There are many approaches that involve seamless geometry movement including morphing leading and trailing edges, morphable wings and wing tips, continuous mould-line technology, etc. Several of these concepts were addressed in an AVT Symposium on Morphing Vehicles (Evora, Portugal, April 2009, RTO-MP-AVT-168). Likewise there are many pneumatic control approaches to create ‘virtual geometry changes’ that involve blowing or suction to increase the effectiveness of (or even replace) conventional aerodynamic control surfaces. Successfully implemented flow control technologies have the potential to revolutionise the performance and manoeuvre characteristics of modern air and maritime platforms. Flow control technologies have a wide range of uses from separation control for improving high alpha performance to lift augmentation and full 3-axis flight control. However, to date, exploitation on production platforms has been limited, often due to the complexity, power requirements and impact on cruise performance.
A recent STO workshop (May 2013, AVT-215, Novel Control Effectors for Military Vehicles) explored many of these innovative control effector technologies including geometric, seamless and virtual (pneumatics, plasmas etc.) shaping with a key objective to explore, assess and baseline the current state of the art. Task Group AVT-239 (Innovative Control Effectors for Manoeuvring of Air Vehicles) has built upon the outcome of the workshop to investigate a number of pneumatic control approaches against benchmark configurations. The RTG has looked not only at functional performance, but also key integration criteria, e.g. complexity, maintainability, reliability, etc.
As a result of work in AVT-239, two opportunities have arisen to demonstrate innovative control effector technologies on subscale air vehicles through the proposed Cooperative Demonstration of Technology (CDT). These demonstrations will prove the feasibility/applicability of implementing the selected technologies and to confirm/prove the model based analysis undertaken within AVT-239. This CDT will increase confidence that the technologies could be implemented on a full scale vehicle, thereby reducing the design compromises imposed by expected future design demands such as low observability, and realizing the potential performance and manoeuvring benefits for future NATO air vehicles.
The aim of the CDT is to integrate pneumatic-based control effectors onto a subscale air vehicle with a representative tailless planform and ultimately demonstrate effective flight control, whole or in part, with minimal, or no, conventional control surface input.
The CDT is expected to involve two representative tailless aircraft configurations. Reduced scale versions of these configurations have been used in the research efforts of AVT-239. The aircraft and the control approaches will be developed by two teams, one based in the UK and one in the US. Their testing programmes will be separate but complementary.
By carrying out the demonstration, the CDT will:
• Confirm the feasibility of using novel control technologies to stabilize and manoeuvre a tailless vehicle, not just in terms of performance, but also integration
• Identify the steps and barriers to an implementation at full scale.
• Increase confidence in the modelling and prediction methods when applied to full scale vehicles.
• Design of the test vehicle in a modular fashion to enable testing of different pneumatic approaches
• Incremental risk-reduction component testing for conventional and innovative control systems
• Manufacture of the test vehicle
• Qualification and certification for flight, including any necessary system ground tests
• Planning and coordination of demonstration, including test schedule with progressive work up to full fluidic control
• Summarising and reporting on demonstration, including both technical assessment and publicity