The call topic description called for a new IPS (Ice protection system) for composite propeller blades, which can be integrated with composites. From a state-of-the-art-survey of ice protection system (IPS) technologies performed in the preparation of this proposal, seven new active IPS technologies have been selected as having potential for being developed into a cost effective propeller IPS of high technical performance. These are:
- Hot air heating
- Laser heating
- Heating foils either surface mounted or embedded with either steady state or pulsed electrical heating
- Electromagnetic repulsion/attraction
- Microwave heating
- Low frequency forced vibration by electromechanical transducers
- Guided wave ultrasonics using microfiber piezoelectric composites.
Synergistic combination of these IPS approaches, and synergistic combination of any one with a number of passive technologies probably involving non-intrusive ice-phobic chemical coatings, were also investigated. The project discovered the ranking order of performance of these 7 systems to TRL4. There will be a number of innovations to facilitate the high aerodynamic performance of each IPS i.e. they should generate no significant additional drag on any surfaces. This was achieved through the use of power delivery components of very low dimension perpendicular to flight surfaces e.g. microwave strip-line wave guided and antenna, fibre optic cables, low dimensional air ducting and piezoelectric composite foils. By modelling the systems (subject to further state of the art study and screening within the project) a prototype, according with the specifications defined in the topic description and additional partner criteria for performance evaluation, robustness and cost effectiveness, was developed. The prototype construction, if laboratory evaluations were passed, will be tested to TRL4 on a propeller test rig in an icing wind tunnel.
Ice accretion during flight of an aircraft affects the performance and control of the plane. Aircraft icing continues to be a concern, reportedly causing numerous aviation accidents and deaths globally in the recent years. The altitude range of operation of aircraft makes them susceptible to encounter icing conditions. In addition, economic pressures dictate that aircraft must keep flying in known adverse weather conditions and these pressures will continue to increase. Moreover, there will always be risks that a flight will run into unpredictable icy forming conditions even when departing in perfect weather. On open rotor propeller aircraft, it is identified that the leading edge of the propeller blade is especially vulnerable to ice accretion in flight, as well as on the ground. When the ice built up, the increased mass due to the ice will lead to increases of drag and consequently decreases the lift. The ice accretion also caused uneven distribution of weight which prejudices the flight equilibrium and as a consequence, lowers the minimum stall angle which is hazardous. Ice also causes the control and propulsion mechanisms to be reduced in efficiency and even seize up which may endanger the aircraft. Ice can also be dangerous on propellers because these structures are finely balanced and any moderate ice accretion can seriously affect the balance, causing stress levels which could threaten the structural integrity.
There is a real need of IPS for the propellers of the advance open rotor engine as propeller aircraft are more prone to icing problems in flight than jet (turbofan) engines because:
- They tend to fly lower in more cloudy or more moist air and it is in these conditions that most of the in-flight ice accretion occurs.
- They are used much more than jets for regional travel in colder parts of the world with severe winters, typically northern Europe, North America, Canada, Russia, Northern China and many other areas all over the world with high altitude terrain.
In this project, the open rotor architecture is envisaged on single aisle, short or medium range aircraft (i.e. A320 type). The project called for a new Ice Protection System (IPS) which is suitable or adaptable to such open-rotor propeller blades. From a prior state of the art survey of IPS technologies, seven active IPS technologies have been established as having potential for being developed into a cost-effective propeller IPS of high technical performance. These are (i) Hot air heating, (ii) Laser heating, (iii) Heating foils either surface mounted or embedded with either steady state or pulsed electrical heating (also known as electrical resistance heating). (iv) Electromagnetic repulsion/attraction, (v) MW (MW) heating, (vi) Low frequency forced vibration by electromechanical transducers and (vii) Ultrasonic Guided Wave (UGW).