Features Procedures Safety & Training
No early explanation for Glasgow crash

The Air Accident Investigations Board (AAIB) often issues a
preliminary bulletin within days of a major incident, but with police
not discounting the possibility of finding more survivors below the
helicopter in the Clutha bar, emergency response was the priority rather
than investigation on Sunday.

Investigators from the manufacturer
Eurocopter are assisting the government team. Eurocopter told operators
of the EC135 to fly as normal, in a safety information notice issued at
the weekend. It said: "At this stage Eurocopter is not in a position to
recommend any special measures to our worldwide EC135 operators."

The
AAIB will continue examining the wreckage of the EC135 when it is taken
to its HQ in Farnborough, Hampshire. Investigators will not have the
usual recourse to a black box or flight data recorder, which are not
required to be fitted in police helicopters.

Any grounding of the
fleet is seen as extremely unlikely, as it usually occurs if a broader
design fault is discovered in the aircraft model. The EC135 entered
service in 1996 and is used by emergency services around the world.

David
Learmount, operations and safety editor of aviation news website Flight
Global, said: "It's chosen because it's robust. An unsafe aeroplane is
never given a licence. You don't go looking for a type and say that was
the cause."

Police Scotland
said that following a safety notice last year, the EC135 T2, the
force's sole helicopter, underwent detailed inspection that found no
faults. Eurocopter issued the notice in May 2012 after a crack was
located in the main rotor hub shaft of an EC135 helicopter in France.

One
theory raised early on was that the helicopter may have run out of
fuel, after witnesses described seeing it dropping like a stone from the
sky. Another theory was that there was a problem with the gearbox
transmission system.

The British Airline Pilots' Association said
that while questions about why the crash happened were understandable,
"it is our experience that speculation about causes is often wide of the
mark".

Learmount echoed that caution, saying non-specialist
witnesses to traumatic events were often unreliable in their
interpretation of events. He said: "Something failed. But the list of
what it could be is incredibly long. Helicopters are very complex
mechanical devices.

"This helicopter when it crashed was totally
out of control – if the pilot had any control and was pushed into a
forced landing, he would not have gone for the flat roof. If you lose
control suddenly like that something dramatic has suddenly occurred,
probably a mechanical failure of some kind."

The EC135 has two
engines, and in the unlikely event they both failed simultaneously it
would still be able to glide, Learmount said.

The crash comes at a
time of heightened anxiety about the helicopter safety of helicopter
flying in Britain, particularly in Scotland after a spate of incidents
involving offshore workers travelling to North Sea rigs – including the
fatal crash of a Eurocopter Super Puma helicopter in August,
killing four.

In January the first recorded fatal helicopter crash
in London raised concern about flying in built-up areas. The pilot died
after colliding with a crane by the Thames near Vauxhall, and falling
wreckage killed a pedestrian and injured 12 on the ground.

The
Commons transport select committee launched an inquiry into helicopter
safety in September. Louise Ellman, the committee's chair, said of the
Glasgow crash: "It's very distressing and highlights the general
concern about the helicopters."

The focus of the committee's
inquiry will be the North Sea. Ellman said she had heard worrying
evidence that the offshore gas and oil industry's workforce had lost
confidence in the helicopters they had to use.

A review of North
Sea helicopter safety is also being conducted by the Civil Aviation
Authority and the European Aviation Safety Agency.