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Prism Defence was formed in 2004, and consists of a team of highly-skilled test pilots, flight test engineers, and other ship and aviation engineering specialists. Our niche is rotary wing flight test, particularly ship-aircraft interface testing, with Prism members having been responsible for more than a dozen such trials for the navies of Australia, New Zealand, Denmark and Sweden.
Prism personnel have first-hand knowledge flying helicopters and commanding ships and therefore have a thorough understanding of the complexity of ship / helicopter integration. In addition to this understanding of the problem, Prism has many years of experience in the science behind the complex ship-helicopter interface. This unique combination of operational and developmental experience means that Prism is able to develop operating limits that maximise the operational capability whilst maintaining safety to an acceptance level making Prism the right choice for bringing a ship-based helicopter capability to fruition.
A major focus of the ship-helicopter integration effort is often centred on the conduct of first of class flight trials (FOCFT), which are also referred to as ship helicopter operating limit (SHOL) trials, or dynamic interface (DI) trials.
However, FOCFT are only part of the story. A synopsis of each of Prism's associated expertise is detailed below.
Ship design and helideck certification
In order to ensure that safe and practical helicopter operations can be conducted to a given vessel, the ship’s flight deck (or helideck) and aviation facilities must meet a range of certification standards, national guidelines, and operator requirements. Prism has a thorough understanding of these standards and how they apply to different ship classifications. Prism ensures that the standards are appropriate, and then evaluates the flight deck and aviation facilities in accordance with these standards.
The embarked environment has unique characteristics, which must be considered prior to a helicopter operating at sea, particularly if the aircraft type has had little embarked operating history. Prism understands this complex environment and applicable aircraft certification standards, and is therefore able to work with the certifying authority to review compliance with these standards prior to embarkation.
Ship airflow trials / analysis
Turbulence is an expected aspect of the embarked environment, but it can vary significantly between different ship types. Prism can employ modelling and simulation tools during the ship design phase to assist designers in reducing adverse aerodynamic effects over the flight deck. Once the ship has been built, Prism is able to use modelling, or conduct actual airflow measurements, to identify airflow characteristics that could cause dramatic handling qualities issues for the pilot, thereby serving to minimise hazards during the conduct of the trial.
Ship motion limits analysis
One of the major analysis tasks that is conducted prior to embarking a helicopter onboard a ship involves dynamic modelling of the aircraft on the flight helideck, to determine when the unrestrained helicopter begins to slide or topple, or when the restrained helicopter exceeds a structural limit. This activity is commonly referred to as "toppling and sliding" analysis; although, because it also analyses the restrained helicopter, Prism refers to this as ship motion limits analysis.
Ship and aircraft instrumentation
Instrumentation is required for FOCFT to provide critical safety information for the test crew, and to measure trials data to produce accurately-defined limits. Prism's in-house, experienced design team are able to instrument both the helicopter and ship and provide a telemetry link to enhance safety and trials efficiency. Prism has the flexibility to develop an entirely new data acquisition system, or to integrate our specialised SHOL-development software to an existing suite.
First of class helicopter flight trials
FOCFT involves the development of ship helicopter operating limits SHOL, and evaluating the suitability of ship aircraft interface.
SHOL are a group of defined operating limits for safe operation of a particular helicopter type with a given class of vessel. The limits are a function of the vessel’s motion and superstructure turbulence characteristics, and also the performance and configuration of the helicopter type.
SHOL development involves operating the helicopter in a wide range of environmental conditions, commencing in benign conditions, with an incremental build-up. Proven processes are followed to determine the operational flight envelope and any unique procedures required to safely operate from the vessel. The aircraft and ship are usually instrumented in order to safely reach the maximum operating limits.