David Learmount/LONDON
World helicopter accident totals over the past few years certainly show no improvement in safety's favour. The figures plot a wandering line, revealing no real trend.
In the USA, by far the biggest single nation of helicopter operators and the best documented statistically, the helicopter safety picture is worsening marginally in absolute figures and rates for all sectors. This is while other sectors in US general aviation - light aeroplanes and corporate fixed-wing aviation for example - are steadily improving.
There were 197 helicopter accidents in the USA in 1999, compared to 161 in 1991. Over the same period, fatal accidents have climbed from 25 to 31, and rates are on a shallow climb (see graph).
While a world total of 192 turbine helicopter accidents (see accident listings, P38), last year showed improvement over 1998's 239 accidents, it still did not beat the 1997 level of only 171 accidents. A glance at 1996 shows 218.
Engine failure/power loss accidents remained high last year, at 49, but mechanical failures (not including rotor blade failures) rocketed from 13 to 28. The most common were failures - usually disastrous - in the drive train or one of the gearboxes, but one was in a gearbox mounting.
Other accident categories which changed significantly were wire strikes and external load snagging accidents - both down in numbers. Events caused by disorientation in blowing snow or white-out conditions, and crashes in which weather was a major factor, were both up. Known maintenance error accidents doubled from three to six.
The Helicopter Association International's (HAI) analysis of the US Federal Aviation Administration's figures for accidents in the USA during 1999 is educational. The fatal accident rate for twin-turbine helicopters is slightly worse than that for single-turbine helicopters, but the all-accidents rates for the two shows twins (2.87 accidents per 100,000h flown) to be much safer than singles (7.29). This differential is consistent in previous years.
Piston-engined helicopter figures differ vastly from those of turbine-powered rotary wing aircraft. The 1999 figures show the piston accident rate as 25.28 accidents per 100,000h flown, which is 3.5 times the rate for single turbines and nearly nine times the rate for turbine twins. HAI safety director Dick Wright cautions against judging the piston-engined helicopters too harshly, particularly in assuming that the engines are less reliable.
He points out that 17% of all helicopter operations involve flying training, which has a high accident rate, and most training helicopters are piston-engined. A high proportion of agricultural helicopters and of helicopters flown by relatively inexperienced owner/pilots are also piston machines.
Despite the apparent lack of progress in the safety of rotary-wing flying compared with fixed-wing, efforts are under way to pinpoint areas for improvement. Wright points out that the HAI is taking part in the Joint Safety Analysis Teams (JSAT) under the FAA's overall Safer Skies initiative and that the weather and controlled flight into terrain (CFIT) reports have just been completed and filed with Administrator Jane Garvey.
Wright chooses to leave it to the FAA to release the recommendations, hinting only that "most of the recommendations tend to be the same for all aviation communities," meaning fixed and rotary wing.
In New Zealand, helicopter accidents have been giving its civil aviation authority (NZCAA) headaches for years. The NZCAA reports that "the helicopter revenue passenger and freight long-term accident rate is downward, but the 1999 accident rate is above the year 2000 target". It adds that the accident rate for the helicopter "revenue other" group (includes agricultural and training) is "slightly lower than it was at the beginning of 1995".
Compared with overall US rates, the long-term accident rate trend for non-revenue helicopter operations is upward, says the NZCAA, pointing out that it reached a high of 78 accidents per 100,000h flying at the end of 1998.
Quirky weather
Perhaps the most salutary safety story of 1999 was white-out-related. It was the extraordinary tale of the three Alaskan sightseeing helicopters from Temsco Helicopters which suffered identical accidents on the same day in the same area (accident tables, 10 September). The second two had gone to help the first one, which had crashed on Juneau Ice Field. Luckily, no-one died. The problem was the quirky nature of the light: everything visible around, above and below was in shades of white, and the few apparent visual cues were just traps.
Even the third pilot, operating with extreme care, was beaten by the light and, like his colleagues, flew into the sloping ice without knowing it was coming up to hit him.
Another factor driving the pilots onward and possibly distorting their judgement was the self-imposed pressure on a pilot when colleagues need rescuing. It is far more difficult to make a detached decision, like waiting for the weather to improve, especially when the weather looks as if it is flyable.
Temsco was not the only company to lose a sightseeing helicopter to quirky light over an Alaskan glacier. On 9 June, a Coastal Helicopters aircraft with seven people on board fell victim to "flat light" over the Herbert glacier. No-one survived. Other pilots who were there that day reported visual meteorological conditions, but with 'flat light' beneath overcast skies making the glacier surface difficult to see.
It is hard to know how pilots can assess and report what they cannot see accurately. They can only report what they think they see.
However, with four helicopter crashes in one year over ice during sightseeing operations from Juneau, Alaska, a cautionary message is evident for the companies which specialise in the task, and for those people who consider paying to fly with them: white-out can be just as dangerous as zero visibility, but in zero visibility nobody would take off.
Another operation which might make potential passengers look for alternative forms of transport would be helicopter transport between the Rangali Island Hilton Hotel helipad and Mali International Airport in the Maldive Islands.
Twice last year there were fatal accidents to helicopters taking off from the helipad. In one case (26 January), a Mil Mi-8 suffered mechanical failure over the sea and five people died in the ditching.
In the other accident (on 3 December), a Bell 212 crashed into the sea in instrument meteorological conditions, resulting in all 10 people on board being killed.
A most simple weather accident involved a police pilot who looked at the night sky and saw stars, so decided to take off without checking the weather. He climbed quickly into unexpected cloud with a "night sun" light switched on, became disorientated and crashed (17 August).
Helicopter flying is still more the province of individualism than fixed-wing flying, probably because of the diversity of tasks, locations and situations which helicopter pilots face.
It is almost bound to involve higher risk than airport-centred aeroplane flying, but some professional operators still achieve safety levels approaching fixed-wing standards.
Source: Flight International
