The potential of rotorcraft to increase airport capacity

Keywords Conferences, Aircraft, Helicopters, Royal Aeronautical Society

Many issues were discussed at this Conference at the Royal Aeronautical Society with contributions including current rotorcraft passenger services and the major concerns which will need to be addressed in the near future to ensure widespread acceptance of more extensive services.

Three current scheduled helicopter operations were described,Malmo/Copenhagen, Vancouver/Victoria Island and Penzance/Scilly.

The first of these told of the beginning, in the 1970s, of an operation that enabled Helsingborg to become the first city in the world in 1985 with an international scheduled airline service using helicopters. Efforts at expansion followed in the succeeding years, culminating in permission to operate between Malmo and Copenhagen in 1988. The next few years saw varying fortunes but in the 1990s, with reorganisation and more new equipment, a first inter-line agreement(with Delta Airlines) was concluded in 1996. Further helicopters have been delivered and passenger numbers have been rising successively for a number of years.

Helijet, which operates between Vancouver and Victoria, began operations late in 1986. Prior to this, commuter passengers were restricted to floatplanes in daylight VFR operations. Within six months of start-up, the company had a 70 per cent load factor and within two years the total harbour to harbour market had doubled to 130,000 passengers. Service, reliability and safety were quoted as attracting further passengers and, in 1996, Vancouver Helicopters was acquired and the company entered into the corporate VIP charter, tourism and the film market. In 1997, North America's first international scheduled helicopter service between Vancouver and Seattle was launched and further diverse contracts followed. The company now has six SK 76 and seven light/intermediate helicopters. During the busy season, 55 flights per day are operated. Noise mitigation for public acceptance of helicopters is vital and special routes are round particular areas and cruising altitudes raised.

The history of the Penzance/Scilly service described how, after years of small fixed-wing operations, the S61N began to operate a scheduled service in 1964. This helicopter was a great improvement on its predecessors particularly since no fixed-wing aircraft could match its performance on this route. For example, one helicopter carried 36,334 passengers in eight months, whereas up to five Rapides carried only 27,000 in 12 months. Regularity also improved. A new terminal was built in the Scillies in 1974 and, by the end of this decade, one helicopter was carrying 86,000 passengers a year. Recession and recovery followed but, despite this, a second heliport was opened at Tresco in 1983. After further difficult years British International was formed in 1994 and a complete review of operations was undertaken, resulting in vast improvements in recent years, including:

• a 43 per cent increase in passengers since 1994;

• up to 26 flight per day departing Penzance when required; and

• a second helicopter schedule despatches 18 or more flights per day (this extra capacity has enabled an expansion of the inclusive tour business).

One of the successful factors is that the service plans to embark-disembark up to 30 people plus baggage and refuel in eight to ten minutes at Penzance and at St Mary's; a seven-minute turn around is planned.

Public acceptability of rotorcraft

These critical topics were outlined by speakers from GKN Westland and AHS International. Over a number of years, research has implied that helicopter noise levels need to be much lower than those for fixed-wing aircraft for a similar level of annoyance or acceptance. An alternative view would be that annoyance caused by main roto/tip vortex interaction (BVI), main rotor wake/tail rotor interaction (TRI) and tail rotor noise is largely ignored by conventional rating procedures. In fact, an underlying dislike of helicopters and the additional annoyance due to certain transient characteristics of rotor noise are both important.

Concerns of safety are also of great importance, particularly as most of those used, particularly in Europe, are twin engine and can fly with one engine inoperative. The connection between noise and safety is not obvious but it has been shown that concerns about the latter have a direct bearing on the level of acceptance. Another idea which is not true is that helicopters fly in an uncontrolled manner.

Fixed-wing aircraft operations typically involve a large number of flights per day and, because the characteristics of most of the large jets are similar,the noise climate is relatively uniform. Away from airports aircraft overfly at high altitude and there is little general concern over aircraft safety. Helicopter operations are very different. In general, the number of operations is relatively low and very variable in nature. Flight paths, unlike those used by fixed-wing aircraft, vary widely and so at any one location the noise pattern is much less consistent. There is also a very large difference in both level and more importantly, the character of noise created by different helicopters with some small helicopters sounding noisier than larger ones. Overflights are generally made at relatively low altitudes, so that any concerns over safety are heightened.

Overall, the reaction to helicopters and heliports is dependent on several factors, some of which are completely unrelated to helicopter noise. These non-acoustic phenomena are described collectively as virtual noise and are usually triggered by acoustic noise although there is some evidence of a visual trigger. The non-acoustic component can dictate the level of public response to helicopters in certain circumstances. The reduction of noise from all sources on helicopters has undoubtedly been accomplished on the latest advanced technology designs. This also decreases the virtual noise. Nevertheless, the only way to increase public acceptance is to reduce noise to become inaudible, or minimize the annoyance factors.

Of considerable interest was a contribution from Bell Helicopter on tiltrotor development to meet public acceptability targets. After a brief review of tiltrotor technology including the XV-15, V-22 and Bell/Agusta 609, the paper expanded on congestion at airports and the inevitable result of frustrating delays in flying from one city to another, no matter what the distance. It is projected that in the next 20 years there will be a 95 per cent increase in the number of passenger flights. Already, Milan, the most congested, has almost three-quarters of its flights delayed by an average of 52 minutes each.

Expanded airports and new airports are not necessarily the answer because of environmental considerations, availability and cost. A civil tiltrotor system is a viable option and would provide convenient air service access to a large proportion of the travelling public. This kind of aircraft can provide the services into the larger, long distance airports that commuter turboprops ply today.

Changes are needed and can be made to national and regional airspace control systems so that tiltrotors and other vertical flight aircraft can operate more efficiently. New approaches can be designed, one being the NASA/Boeing study called the "simultaneous non-interfering (SNI) approach" for rotorcraft. Although it is designed to accommodate all rotorcraft, this new approach concept will specifically allow tiltrotors to operate in the fixed-wing system. Tiltrotors will be handled in the conventional way while en route and then transition into a new approach procedure that will allow them to move out of the fixed wing ILS approach and into a new, separate IFR approach to the final touchdown area.

Public perception advantages of tiltrotors are key factors, noise being most critical but the tiltrotor may have some improvement over other rotorcraft in this respect. Such services could also spread air and ground congestion round airports more equitably over a larger area. A 40-passenger tiltrotor is projected and these could be the choice for the commuter aircraft of the future.

European developments

Rotorcraft technology and products was presented by Eurocopter, France, and concentrated on developments foreseen for 2005/2015. Several key features are apparent, these being economic efficiency and cost reductions in the fields of(in order):

• 1.

  equipment and avionics;

• 2.

  engines;

• 3.

  dynamic components; and

• 4.

  airframe.

Speed and range impact on economic efficiency; for the first, fuselage aerodynamics are most important and, for the latter, a tiltrotor demonstrates improvements in many technologies.

All-weather capability should be the same for rotorcraft as for fixed-wing aircraft and this is now possible. In take-off and landing phases, accurate navigation, 3D cartography, ground collision avoidance, enhanced vision,obstacle warning, and airborne collision avoidance systems are all available, as well as in the en route phase, GPS navigation, low cost icing and the systems already mentioned. Integration into the future ATC/ATM system is now practical. Economic efficiency will be improved by all-weather capability.

Eurocopter views the product range in the future as:

• light singles - 4/6 passengers;

• light twin - 5/6 passengers;

• medium twin - 9/12 passengers;

• medium heavy - 15/19 passengers; and

• heavy - 30/40 passengers.

This range includes helicopters and tiltrotors.

A review of European research initiatives was given by GKN Westland Helicopters, which sought to cover the major issues appropriate to achieving rotorcraft operations from airports and a summary of relevant European collaborative research projects (past, present or future). Air infrastructure studies exist in many fields, including departure and arrival integrated management system for co-operative improvement of airport traffic flow; North European CNS/ATM application project; and forum for large improvement of air traffic in Europe.

The RESPECT (rotorcraft efficient and safe procedures for critical trajectories) project deserves particular mention, which began in 1997 and will last for three years. It aims to:

• develop a common helicopter performance code and validate using flight test data;

• analytically optimise trajectories and proposed improved take-off and landing procedures;

• assess practical feasibility and repeatability of the developed procedures;

• propose guidelines for improved helicopter operations; and

• propose a simulation-based helicopter performance analysis tool.

Ground movement studies would also be completed as well as the environmental impact.

Quiet helicopter research activities are in many areas (Plate 1) including:

• drag reduction of rotor head and pylon fairing;

• cockpit instrumentation, human/machine interface and visibility/handling qualities in steep descents;

• low RPM and high torque gearboxes and new materials; and

• cabin noise reduction.

The European tiltrotor programme includes the Agusta share in BA 609, as well as two new proposals. Many other initiatives are in progress to decrease the impact of noise and traffic demand, as well as a study completed in 1997 on interactions between high-speed rail and air passenger transport. Many key issues are still to be addressed.

 Plate 1 GKN Westland Helicopters' quiet helicopter technology research areas

Air-traffic and airport management

Air-traffic management capacity constraints on and around airports was a subject dealt with by Eurocontrol. Initially, the main emphasis of Eurocontrol was on the en route phase of flight. What was known as EATCHIP (European air-traffic control harmonisation and integration programme), now the European air-traffic management programme (EATMP), has developed initiatives predicted to provide an increase of over 50 per cent in capacity in the en routeenvironment by 2005.

Up to the present, little emphasis has been placed on rotorcraft to enhance capacity, although an effort must be made to analyse these operations under IFR. To explore the potential of rotorcraft a significant change may be required in the perception of operations from an ATC perspective. Existing procedures will have to be re-examined to enable the impact of rotorcraft operations to be assessed. Many possibilities have to be considered; for example, is it possible to utilise RNAV, etc. to provide for instrument approach procedures offset by 90°from the runway to be used by rotorcraft? If so, can these be considered as independent operations or must they be considered as dependent for reasons of missed approach, etc.? The initial work undertaken to date suggests that the use of rotorcraft may militate against the effect of some constraints on and around airports and, therefore, the use of such technology should be investigated. Rotorcraft certainly seem to have the potential to increase the European ATC capacity if utilised for distances of up to 1,000km. However, note should be taken of recent developments and the potential of fast rail travel.

From Boeing came a contribution on integrated rotorcraft/vertical flight operations to reduce delay and increase capacity. Airspace problems continue to multiply daily. As passenger demand increases, so does the demand for access to already constrained terminal airspace. The problem is, however, not so much the airspace as the terminal facility, specifically the runway. New types, such as the tiltrotor, or improved helicopters, could be one solution, while the other is a new concept of airspace management.

Current and traditional delay and capacity solutions include additional runways and a coordinated traffic flow planning system that supports higher capacity and efficiency. The alternative solution is vertical flight aircraft and simultaneous and non-interfering operation (SNI). Compared to a conventional regional size turboprop, the tiltrotor can turn shorter and climb or descend at slower airspeeds and at steeper angles. The best use can be made of the technology by replacing a percentage of regional/commuter aircraft of 40 seats or fewer with tiltrotors or efficient helicopters of comparable seat capacity.

The SNI concept referred to combines aircraft-specific unique flight characteristics with applicable regulations and performance-based air-traffic procedures and there are no new pieces of technology required for its implementation; only judicious, site-specific application of already existing and approved procedures.