Often it is unfair to blame only the pilot for colliding with objects near a helipad. Some sites are unnecessarily cluttered with objects waiting to be hit

Helicopters cannot afford malfunctions, because when they happen loss of control is frequently the result

David Learmount/london

Fixed wing aircraft can suffer serious malfunctions and still remain stable and controllable. Helicopters are not so lucky. They are controlled by a complex formula of equal and opposite forces: remove any one of these and a dramatic departure from controlled flight is the likely outcome. During 1997 at least 47 turbine helicopters crashed out of control, more than one-quarter of the 171 machines round the world which suffered serious accidents.

In these circumstances a pilot is occasionally lucky enough to retain sufficient control to make impact with the ground survivable. If it were not for the fact that helicopters, even out of control, often hit the ground at a relatively low speed, commercial passenger transport by rotary wing aircraft would probably be illegal. In more than half of the 47 accidents in which control was lost other than by collision, there were no fatalities. The remaining 22, however, cost 58 lives. Only pilot error, a factor in 72 events, featured in a larger number of accidents.


Rigid adherence to component life recommendations, and replacement when damage or faulty parts are suspected, is even more important in helicopters than in fixed wing aircraft because of their unforgiving nature. Similarly, manufacturing quality control is crucial: an Aerospatiale AS350B2 crashed last year because of a faulty hydraulic pump drive belt which failed at less than half its recommended life (see 30 March entry in accident tables).

The ultimate fear, where component quality is concerned, must be events precipitated by "bogus parts" dealing, which seems to be more common in the helicopter business than elsewhere - although perhaps it is more disastrous in helicopters and comes to light because of that. On 7 January, 1997, the pilot of a recently purchased secondhand Hughes 369HS suffered problems controlling his helicopter. Having landed to investigate the symptoms, the pilot could not identify a cause and took off again. He then lost control and crashed, but survived. Investigators discovered that the aircraft had been classified "destroyed" in a fatal accident at Labelle, Florida, on 26 June, 1992. The new owner had bought the rebuilt helicopter in Florida in December 1996.

A year later came the culmination of international investigations, led by the New Zealand authorities, into the bogus parts market. Aided by the US Federal Bureau of Investigation, the Federal Aviation Administration, US Customs and Excise, and manufacturer Robinson Helicopter, New Zealand believes that it has set a world precedent by successfully prosecuting a bogus parts dealer on two counts of manslaughter after a Robinson R22 crashed in New Zealand on 25 October, 1995. One of the tail rotor blades had disintegrated in flight, leading to loss of control and the death of the pilot and his passenger. The investigators suspected that the blade had been remanufactured, and a quiet but extensive campaign to find the suppliers began. It was dubbed Operation Blade.

Police inquiries identified the source of the blades as New Zealander James Gedson. He had contracted a Torrance, California-based company called Cherry Air Specialties (CAS), to remanufacture some damaged components which he had originally purchased from among crashed helicopter parts in a Los Angeles salvage yard. The blades he obtained had been classified as damaged beyond repair. Gedson contracted CAS to use some tailrotor components to produce three sets of counterfeit blades, according to the police. He took the parts to New Zealand and they were all fitted to helicopters, one of which suffered the fatal October 1995 crash.

It was established, during the investigation, that Gedson had been trading bogus parts for years with the connivance of the owners of CAS. These had been exhaustively traced from the manufacturer through various helicopters and traders until the point where Gedson bought, remanufactured and resold them.


The New Zealand authorities believe that Gedson's prosecution is the first in the world to secure a verdict of manslaughter, relating to the supply of bogus parts. Perhaps history will judge Operation Blade and the verdict it won in 1997 as a landmark not only in helicopter safety, but aviation safety as a whole. If the helicopter industry is more vulnerable to the effects of bogus parts than any other aviation sector, at least it has also shown that the fight against the problem can produce results.

Also published during 1997 was a Flight Safety Foundation (FSF) summary of rotary wing agricultural aviation accidents in the USA from 1989 to 1995. This is revealing because not only does it provide insight into one of the most risky types of helicopter operation, but also it gives a safety picture of a significant part of the piston engine helicopter sector, for which accurate records are difficult to obtain.

The FSF report, drawn from US Federal Aviation Administration and National Transportation Safety Board statistics, reveals that engine power loss was the most frequent causal factor in agricultural helicopter accidents, comprising 33% of them. Some 88% of the total of 180 accidents (all categories) during the period involved piston powered helicopters, but the FSF does not distinguish between turbine and piston powered helicopters when studying individual accident categories.

Among the 58 power loss accidents cited, however, 18 (31%) resulted from fuel exhaustion, which demonstrates either a certain lack of discipline on the part of the pilots involved, or perhaps the high level of concentration on physical aircraft handling, demanded by the extreme low-level flying and the need for tight manoeuvring. Engine mechanical failure is also cited as causing 31% of power failures, and fuel contamination 10%. The remainder of the power losses comprise "miscellaneous" causes (7%), and "undetermined" (21%).

To give a picture of where agricultural helicopter safety fits into the US general aviation safety league, the FSF quotes various FAA figures for accident rates per 10,000 flying hours during 1993 and 1994. General aviation as a whole rated nine accidents per 100,000h, whereas the total agricultural aviation accident rate, including fixed wing operations, was about 12.5 per 100,000h. For agricultural helicopter operations, however, the rate goes up dramatically to 22.5 for 1993 and 16 for 1994.


Maintenance inadequacies featured far higher in the accident cause league table than they usually do with fixed wing aircraft. Grouping together what the FAA calls "improper" maintenance (2%), "inadequate" maintenance (8%) and "pilot and maintenance" (9%), maintenance, or lack of it, features as a cause in 19% of agricultural helicopter accidents in the USA. The "pilot and maintenance" category is an interesting one, encompassing situations where the pilot either knew about, or should have recognised, the need for maintenance, but took off anyway.

Boeing studies have revealed, meanwhile, that maintenance faults are a causal factor in only about 3% or less of fixed wing commercial air transport accidents. Whether this vast difference exists because fixed wing aircraft are less vulnerable to poor maintenance than helicopters, or because there is more poor maintenance practice among helicopter operators is arguable; but to the pilot whose life is at risk the distinction is wholly academic.

Among the accident categories cited by the FSF, obstacle strike (22%) is the next most common after power loss; loss of control and "malfunction other than power loss" each comprise 20% of the total. Malfunctions of some kind, then, are involved in 53% of US agricultural helicopter accidents, an unhappy state of affairs, even taking into account the high demands that agricultural flying puts upon the machines.


To return to the non-agricultural helicopter world, malfunctions or failures of some kind or another were the cause of at least 45 turbine helicopter accidents in 1997, according to the early evidence. That is 26% of all accident cases, which is much better than the FSF's agricultural helicopter statistics; but that is not surprising because that environment is, on the whole, less risky than that of low-level agricultural work, and turbines tend to be more reliable than piston engines. Three of the year's turbine helicopter accidents involved agricultural operations, and two of them appear to be power failure. The third was caused by tailrotor failure. Collision with obstacles (trees/objects) caused 13 accidents (7.6%) during 1997. Added to wirestrikes, however, they make 22 collision events (13%).

Sometimes it is not only the pilots who should be blamed for hitting objects on approach to a helipad, however. Some helipads, and not just the temporary ones, are constructed with very little thought to safe approach, departure and even set down. The Mil Mi-8 accident on 14 July is a classic example. The helicopter's tail struck a fuel tank 12.5m from the pad, which was constructed of logs. The pad had the maximum permitted degree of slope, and approaches were restricted by oil drilling equipment. It was the definition of an accident waiting to happen.

Every year accidents happen to helicopters landing on high sites and those just below mountain ridges. Often the accident is brought on by the gusty microclimate which will clearly exist at such a location when there is any wind, particularly when the site is downwind of the ridge (see 24 February entry).

It is clear that skiers, winter sports enthusiasts and adventure holidaymakers will want to be delivered to sites close to the start point for their activity. If, however, they were given the choice of a landing site which was slightly further away but carried a lower risk, which would they choose? The question is hypothetical because they are not given the choice. Like most passengers, they trust the operator to decide.

Pilots are the operators' representative on the spot and have to make the final decisions. Every year, Flight International's accident listing is full of events in which pilots push their skills, their machines, and their own endurance, beyond the limits. A pilot died on 14 September, picking up reindeer carcasses for hunters. The final pick-up, in dusk at the end of a long day, was not difficult. The fact, however, that darkness was approaching and the landing was his 93rd of the day made the manoeuvre fatal. It is difficult to imagine that fatigue did not play a part. It is also easy for pilots not to recognise the onset of fatigue, which is why the operator should set guidelines for a safe working day.


External load operations remain high risk



Pilot error/misjudgement


Engine failure/power loss/fire


Other mechanical failure


Main/tail-rotor failure






Crew training exercises


Collision with trees/objects


Collision with aircraft




Underslung loads/cables snagged


Low level manoeuvring


Maintenance (error known)


Loss of control


White-out/blown snow




Illegal/bogus parts


Other causes


Note: Total accidents listed:171. Many accidents have more than one causal factor. The causes given, as assessed at this stage, are the principal apparent causes and major contributory factors in the accidents listed and may be subject to revision following full inquiry. The causes of some accidents are unknown.

Pilot error could indicate a direct mistake, failure to follow standard operating procedures, inappropriate pilot strategic judgement, or failure to intervene correctly to save the flight. A conservative approach has been adopted in these assessments. Inquiries will probably report pilot error factors as being present in a higher proportion of the total.

Controlled flight into terrain does not refer only to collision with high ground or rising terrain, but includes collision with level ground or water (eg: on the approach) when the aircraft is under control.

See also Turbine helicopters accidents list

Source: Flight International