David Learmount/LONDON
Fixed-wing aircraft set out for airports or airfields, but helicopter destinations are of almost limitless variety, and the precise details are often unknown to the pilot at departure. There is no Jeppesen approach chart for the site of a road accident or a mountain rescue. Professional helicopter pilots also face many more variations in their normal duties than do fixed-wing pilots.
The only advantage that helicopters have is their ability to fly very slowly or to hover. While it is this capability which allows them to land where fixed-wing aircraft cannot, the events in each year's helicopter accident review (see pp40-51) serve as a reminder that slow flight and, particularly, the hover are inherently unstable. Rotary-wing pilots may say that this is fundamental and that they do not need to be reminded of it, but the evidence suggests that they need more respect for the basics. Helicopter pilots have a particular need for self-discipline in the absence of the orderly routines imposed by airport-approach procedures and the safety conferred by the predictability of airport destinations.
A fair number of bush or outback helicopter pilots, according to studies carried out in Australia, either have, or at least adopt, a devil-may-care attitude to the job they do. This macho style, perhaps, contaminates those colleagues who would otherwise be more careful. The very nature of remote operations can have a powerful effect on the attitude of people towards their work.
The whole "frontier" atmosphere surrounding some of the more remote Canadian logging or firefighting operations, for example, may make it more difficult to apply self-discipline because of the sense of freedom and self-reliance that has attracted many people to the job in the first place. Yet working with underslung (external) loads is potentially one of the most dangerous jobs in aviation.
This year's accident review shows a dramatic increase in accidents which occurred while aircraft were either carrying underslung loads, or had load cables deployed (see table of accident causes). There were 25 such incidents, compared with eight in 1995.
The sheer variety of things that can go wrong is frightening. It can range from a misunderstanding between pilot and ground-crew - who are not usually equipped with voice intercommunication - about whether the load has been attached or released (see entries for 14 and 30 May), to a situation in which a cable snags on the ground (15 October) or on one of the helicopter's landing skids and topples the aircraft as the pilot increases power to take up the load (1 November).
Main- and tail-rotor failures doubled in the year under study (1996), totalling 13, compared with six in 1995. Every year, the problem of drive or gearbox failures, particularly for the tail rotor, is flagged by the Helicopter Association of America (HAI) and numerous public and independent safety agencies such as the Flight Safety Foundation (FSF).
Such failures can happen in situations other than work involving underslung loads, but they do occur unusually frequently in this work, perhaps because the load is taken up relatively suddenly. Another possibility, however, is that the pilot has less knowledge and control over the weight of the load and is often using an ageing helicopter which was not designed for the task.
This continues to worry the HAI, says its chief of safety and operations Dick Wright, particularly concerning former-military Bell UH-1 Iroquois ("Huey") machines which have been acquired for logging and agricultural applications. Three suffered mechanical failures in 1996 while lifting external loads. Bell Helicopter Textron, the world's largest passenger and utility helicopter manufacturer, has observed that mechanical failure is a factor in 5.8% of helicopter accidents, but that the proportion increases to 17.5% in accidents involving external-load work.
There is plenty of evidence in the 1996 accident list to suggest that working helicopter pilots are in too much of a hurry to survey a landing site properly, particularly when it is unprepared. This is a difficult task, even in good weather. The pilot has to be able to assess the physical characteristics of the site, including everything from the potential approach path, to surface-slope, texture and strength.
It is easy to feel sympathy for the pilot who set down in what looked like a firm field and found that the surface collapsed because of rabbit burrows. When a pilot lands on a frozen lake and the ice collapses (23 October), however, is it entirely the pilot's fault ? This happens at least once each year, however, usually resulting in the loss of the helicopter and sometimes lives, too. Pilots left with complete freedom to choose where to land, or even whether to land at all in circumstances where the task could be carried out without setting down, bear a heavy responsibility. Operators stand to lose a machine and a pilot, let alone passengers.
LANDING-SITE CONDITION
Operating procedures lay down preferences for the type of landing site, for example lakeside rather than lake ice, unless ground services have established beyond doubt the strength and thickness of the ice. Some of the burden on pilots would be lifted by not putting pressure on them to continue where there is reasonable doubt about landing-site conditions.
There is also a need to consider the micro-climate associated with landing sites near, for example, mountain ridges, or even immediately downwind of hangars when the pilot does have the privilege of landing at an airfield (see 24 January, 22 February, 21 April).
It is easy to say that all this is what "good airmanship" means for a helicopter pilot, but if aircraft and people are lost regularly because pilots get it wrong, the industry may need to look at training, company operating guidelines, and what they ask of any pilot.
Medevac or rescue work often demands local knowledge of terrain and weather peculiarities. If the pilot is new to the area or the task, the demands may be too high
Sometimes it seems surprising that a particular task was authorised by the operator at all or, if it was not, that the pilot may have chosen to do it in a particular way. In a power-line maintenance job on 19 September, a pilot was hovering next to power lines, rotors overlapping them, while the maintenance engineer, seated on a platform attached to the skids, carried out work on the line. It does not take a great deal of imagination to see that a gust of wind could destabilise the hover sufficiently to snag the skid on the wires or pylon, or catch the rotors on the wires. It happened. The crew escaped with injuries but the helicopter was destroyed.
That was in Australia, but similar practices exist in Hawaii. On 29 November, a helicopter with a crew installing cables on pylons snagged its skid and crashed. It is worth asking whether helicopters should be used for stringing cables on pylons, because cable- or wirestrikes are a perennial nightmare for all helicopter pilots.
There was certainly no decline in wirestrike accidents in 1996: there were 14, the same as in 1995. US National Transportation Safety Board (NTSB) records for the years 1990-5 show that 87 US civil helicopter wirestrikes killed 29 people, and the US Army Safety Center at Fort Rucker, Alabama, shows similarly unhappy figures for military operations: 97 wirestrikes killed 14 people from 1990 to 1996, while damage to airframes totalled $64 million.
An FSF helicopter safety report published in March highlighted the work being done on wirestrike prevention at the US Army Aeromedical Research Laboratory at Fort Rucker.
The aim is to increase the "conspicuousness" of wires, not merely by placing the internationally accepted (but rarely used) three-dimensional orange-coloured globes at intervals along the cables, but by giving the objects a solar-power-recharged light-source which has the potential to reduce poor-visibility and night-time wirestrikes. The Army's figures show that 72% of its wirestrikes occur at night, and that these are more likely to cause death or serious damage.
On power lines, wire-markers have already been developed which are lit by the energy from the wire's electromagnetic field, but communications cables, structure-supporting cables and those for ski-lifts or cable-cars do not have that advantage.
EARLY WARNING SYSTEM
Health-and-usage monitoring systems (HUMS), hailed as the greatest advance in technology for detecting mechanical faults before they cause engine or gearbox failure, are now a well-established tool for the helicopter maintenance engineer.
The HAI, however, is pushing for its development through the US Advanced Aviation Transportation Technology research and development programme as a smart early-warning system for pilots, identifying not just potential faults but providing pilots with cockpit-warning of system limitations and stresses.
The British Helicopter Advisory Board's John Friedberger is optimistic about the progress of HUMS as they move from the "operator-led" programmes that they have been until now into systems that "-the manufacturers are taking much more seriously".
Capt Per Gram is a Norwegian helicopter pilot experienced in that most unfriendly of operating environments, the North Sea. Writing in the International Federation of Airline Pilots Association (IFALPA) journal Interpilot, he is scathing in his criticism of some aspects of an operating arena in which the perverse weather and cold sea have forced the development of procedures more disciplined than in most areas of helicopter operation.
Gram is worried, for instance, that when the draft European Joint Aviation Requirements for helicopter operations (JAR Ops (H)), are approved, an oil-rig landing site may be designated as an approved weather-diversion alternate for the destination rig. He insists that North Sea helicopter operators should be compelled to carry sufficient fuel for an onshore alternate, because if the weather is too bad for one rig, it may be too bad for them all.
Gram, clearly devoted to rotary-wing operations, says: "An aeroplane, by its nature, wants to fly and if not interfered with too strongly by unusual events or a deliberately incompetent pilot, it will fly. A helicopter does not want to fly. It is maintained in the air by a variety of forces and controls working in opposition to each other, and if there is any disturbance in the delicate balance, the helicopter stops flying immediately and disastrously."
This year's award for the luckiest helicopter pilot must go to the Australian agricultural pilot (9 November) who, after suffering a wirestrike, survived his aircraft's determined attempt to destroy itself and him. The wirestrike broke the main rotor-mast, and the rotor severed the front of the helicopter from the rear. The pilot walked away from the inverted front section.
Source: Flight International
