Capability is a function of design or conversion. Helos offer operational flexibility either without requiring modification or by being adapted to various roles through installation of mission-specific equipment.
By Don Van Dyke
ATP/Helo/CFII, F28, Bell 222.
Pro Pilot Canadian Technical Editor
Helicopter versatility is characterized by diverse, often confusing terms like multi-domain, multi-functional, multi-utility, multi-purpose, multi-payload, multi-service, utility, and others.
However, these concepts are not synonymous, and their use in helicopter promotion, review, and selection is further complicated by the lack of internationally agreed definitions regarding:
• the terms “role” and “mission,” and related terms multi-role and multi-mission.
• basic weight or wake turbulence categories (light, medium, heavy, etc).
• criteria for evaluating capabilities which seek to satisfy diverse user requirements.
• identification and optimization of acquisition, operating, and life cycle costs.
Consistent definition, clear understanding, and uniform application of these fundamental concepts are essential to the efficient, cost-effective acquisition and employment of these uniquely capable aircraft.
The discussion presented in this article is based on information distilled from numerous official sources.
Role and mission
A role is the primary function for which a given helicopter was designed and equipped, and for which crews are trained. A mission is a task (a clearly defined action or activity to be completed) together with the reason (purpose) therefor.
Role. Many, if not most, commercial helicopter roles derive from original military designs and technology innovations.
For example, the Bell 211 (HueyTug), introduced in the mid-1960s, was a purpose-built commercial flying crane version of the Bell UH-1C Iroquois. It was equipped with a new transmission, longer main rotor, larger tailboom, strengthened fuselage, stability augmentation system, and a 2650-shp T55-L-7 turboshaft engine.
Similarly, the Sikorsky S-64 Skycrane was developed from the Sikorsky CH-54 Tarhe, and the intermeshing rotor system of the Kaman K-MAX evolved from the synchrocopter design of the Kaman HH-43 Huskie.
Mission. Missions are a measure of what a helicopter fleet must be able to do, and are usually matched with helicopter roles on a best-fit basis.
Missions are diverse, examples of which may include marketing, demonstration, herding and game capture, airshows, urban air mobility (UAM), autonomy, on-demand mobility, and advanced manned/unmanned teaming and swarming. Helicopters matched with roles and/or missions complete each operation with little or no modification.
Multi-role, multi-mission, mission-specific
A central value of a helicopter is its suitability, readiness, and availability for tasking. Major objectives of multiple helicopter configurations are to increase availability, utility, and affordability for military and civil users.
Multi-role. The term multirole applies to helicopters capable of 2 or more primary functions, either with no required modification or modified with combinations of modular systems, tailored equipment, and/or avionics, allowing the same airframe to change quickly between roles.
Development of multi-role helicopters seeks to reduce costs by sharing common airframes, thereby decreasing the logistics footprint and number of personnel required to support different helicopter types.
Multi-mission. Operators historically tended to acquire rotorcraft specialized and optimized for their intended domain (eg, maritime, ground). However, the oil and gas industry downturn, in particular, reduced the overall demand for helicopters. This left operators to increasingly seek aircraft capable of serving multiple missions with domain interoperability.
Helicopter industry executives believe the current market is looking for greater utility and thus driving demand for rotorcraft capable of completing a greater range of missions.
Multi-mission helicopters range from light types like the single-engine Leonardo AW009 (SW-4) to the 3-engine, heavy Leonardo AW101 Merlin. Multi-missions are varied both in the combining of helicopter roles for their achievement and the identification of new applications for multi-role platforms.
Multi-mission concepts may also apply to helicopter avionics. Flight management system (FMS) upgrades offer advanced functionality for law enforcement and similar functions, making multiple mission profiles available to the crew at the touch of a button, saving workload and enhancing situational understanding.
Mission-specific. Opinions on multi-role and multi-mission helicopters remain divergent. Designing for multiple, nearly exclusive roles from the start may result in less than desired performance.
Multi-role aircraft tend to be larger than necessary, to be overly complex, and to exhibit a high cost-to-capability ratio. Certain military and civil aircraft designs, while innovative and technologically possible, have proved costly and failed to meet basic expectations.
Expensive post-production modifications and extended procurement times were often the result. Airbus Helicopters announced at Heli-Expo 2019 its focus on purpose-built helicopter types to execute more narrowly-scoped missions.
This approach relies on the philosophy that a mission-specific design will do it well, with room to grow into other missions – given time.
However, purpose-built helicopters are not easily or quickly converted from one role to another, typified by those customized for military/paramilitary/police, VIP/executive transport, and emergency medical service (EMS) operations.
Evaluating role/mission designs
Different helicopter users (ie, private owners, commercial operators, multi-nationals, armed forces, state agencies, border security services, etc) may use the same helicopter for an assortment of missions. A common goal is to identify an optimum role/mission design which satisfies wide-ranging user requirements at the lowest possible life cycle costs (LCCs).
This should involve a formalized decision process for the assessment of different design solutions, but it has to be one which goes beyond simple comparison of performance and equipage. A framework for multi-role helicopter design which optimized LCCs was developed by the Netherlands National Aerospace Laboratory (NLR). Modifying this approach, factors dominating mission requirements are defined (flight hours, flight profile, payload, etc), and role features ideally matching these requirements can then be identified.
The sensitivity of the helicopter design to each of these parameters is then assessed by trade-off analyses. Comparisons will inform choices by decisionmakers regarding acquisition of new aircraft and retention of existing aircraft.
Baseline design. Helicopter designs are normally driven by performance requirements, where mass is historically considered the primary optimization criterion. These are tabulated together with figures of merit based on technical opinion and experience. Simply, the candidate helicopter is then compared with the baseline helicopter and scored.
However, convergence of propulsion, autonomy, communication, and perception technologies must also be considered together with other less common influences. These may include:
• propulsion alternatives (turbine, electric, hybrid).
• safety management manual (SMM) requirements for complex operations.
• resolution of cabin and role equipment design issues.
• ongoing verification/validation activities on problematic or deficient aircraft systems.
• limitations of darkness, weather, density altitude.
• cybersecurity and survivability in degraded electromagnetic environments.
• energy efficiency and community noise.
• role of simplified controls and automation in training, recruiting, and retaining pilots.
• insurance and liability of OEMs (especially those privately-owned and self-insured).
• rate of airworthiness directives (ADs), service bulletins (SBs), service letters (SLs).
• decommissioning and re-sale.
Multi-role helicopters may be characterized in terms of risk criteria in operations requiring specific approvals, such as performance-based navigation (PBN), low-visibility operation (LVO), extended-range operations, hoist operation, EMS, night vision imaging system (NVIS) or dangerous goods (DG), and operating environment (offshore, maritime, mountainous area, etc).
LCCs are influenced not only by the mission characteristics, but also by the maintenance policies applied, which in turn can be affected by design choices. To optimize cost, a multi-disciplinary optimization approach is required at the preliminary evaluation/selection phase.
It is expected that the future of multi-role rotorcraft will continue to be influenced by technologies and designs developed for military applications.
The US Army Joint Multi-Role (JMR) Technology Demonstrator program seeks to realize rotorcraft with significantly improved speed, range, and hover stability while reducing unit and maintenance costs.
Candidates are the Bell V-280 Valor tiltrotor (with higher speed and greater range than its competitor) and the Sikorsky-Boeing SB>1 Defiant compound helicopter, which features less downdraft and noise due to its dual rotors. The speed and range of both aircraft are attractive for multirole commercial applications.
The JMR Technology Demonstrator effort will inform requirements for the US Army’s Future Vertical Lift (FVL) family of systems, which will become operational in the 2030s and is intended to replace Sikorsky UH-60 Black Hawk and Boeing Apache helicopters.
NATO Industry Advisory Group (NIAG) has recommended that future rotorcraft designs avoid a single main rotor in favor of coaxial, tiltrotor, or compound configurations. Other concepts to be settled include aeromechanics, experimental aerodynamics, and drive systems.
The primary roles for which FVL development is supported include conducting assault, urban security, attack, maritime interdiction, medical evacuation, humanitarian assistance/disaster relief, tactical resupply, direct action, non-combatant evacuation operation, and combat search and rescue missions in support of army and joint forces.
The experience and technologies gained during the evolution of FVL systems will be shared among a wide field of users and feature in next-generation rotorcraft multi-role capability planning. In both civil and military markets, manufacturers will strive to offer products which are increasingly able to morph from one role to another and with ever greater mission reach and capability.
Don Van Dyke is professor of advanced aerospace topics at Chicoutimi College of Aviation – CQFA Montreal. He is an 18,000-hour TT pilot and instructor with extensive airline, business and charter experience on both airplanes and helicopters. A former IATA ops director, he has served on several ICAO panels. He is a Fellow of the Royal Aeronautical Society and is a flight operations expert on technical projects under UN administration.