EASA orders Super Puma
inspections
TEXT: Michael Sandelson
– The Foreigner ©2016
The European Air Safety
Agency’s Emergency Airworthiness Directive covers mandatory inspection of key EC
225 helicopter parts. Airbus Helicopters also tells aircraft owners to take
action.
In their document,
officials say that their move is a precautionary measure following the 29th
April accident in Norway, which claimed 13
lives.
Norway’s Accident
Investigation Board (NAIB) has stated that the crash was due to technical
failure rather than human error.
NAIB officials are
upholding their own temporary ban on Airbus EC225 LP flights. The UK and
Norwegian CAAs have issued No Fly orders.
“The partial information
available so far indicates in-flight separation of the main rotor hub from the
main gearbox,” the European Air Safety Agency’s Airworthiness Directive
reads.
Technical failure
investigation
The root cause of the
accident in Norway is still under investigation. EASA states that it may require
further mandatory action.
In a
statement, Airbus Helicopters
says that “the investigation will now solely be focused on potential root causes
of a technical failure, such as design, production, and/or
maintenance.”
Current main rotor drive
inspections EASA has imposed on all
owners of this aircraft type must be carried out before the helicopters’ next
flights, they say.
These relate to:
·
Checking that all the
main gearbox’s (MGB) suspension bars – Front and Right Hand and Left Hand – are
installed correctly (these are the MGB’s mounting
supports). This is in accordance with Airbus Helicopter’s (AH) instructions in
their EC225 Alert Service Bulletin 53A058
·
Checking that there are
no metal particles in the MGB’s chip detectors – in accordance with the
instructions of Work Card 60.00.00.212 of AH EC225 Maintenance Manual
(MMA)
·
Checking that there are
no metal particles in the MGB’s oil filter. This is in accordance with the
instructions of Work Card 63.24.01.061 of AH EC 225 MMA
·
Checking that no limits
have been exceeded on helicopters that are fitted with an M’ARMS Vibration
Health Monitoring System. The data is to be accessible should future analysis be
needed.
Critical part
Commenting on EASA’s
Emergency Airworthiness Directive, Per Gram, a former helicopter pilot with over
20,000 hours flying time tells The Foreigner that “the entire helicopter hangs
underneath these MGB suspension bars.”
“The three suspension
bars run from the fuselage up to the main gearbox and connect everything
together. The main rotor loosens if the Front Suspension Bar either fails or
comes off. It’s quite obvious why investigators are focusing on this issue now,”
he adds.
EASA’s Directive refers
to a previous “Service Bulletin” that was issued with regards to the MGB’s
mounting supports.
These are issued by
aircraft manufacturers every so often and usually require all operators to check
for specific damage or wrongly fitted components after something minor has been
found during routine maintenance on a particular aircraft.
Airbus Helicopters has
also sent out an Emergency Air
Service Bulletin (Airbus Safety Alert
3035-S-00, dated 3rd May 2016) to all EC 225 (now H225)
owners.
“Following the accident
involving an EC225LP dated April 29th, and considering the observations gathered
by the investigation team since this date, this Alert Service Bulletin requests,
as a precautionary measure, the verification of the correct installation of all
MGB suspension bar attachments,” they
write.
“This Alert Service
Bulletin consists in a one-off check of the MGB suspension bar attachments for
their torque tightening value and the condition of the pins and sending the
results of this check to Airbus Helicopters. Compliance with this Alert Service
Bulletin is mandatory.”
Close examination
Chip
detectors are magnetic switches
that protrude into the flow of oil in engines and gearboxes, usually situated
near the oil filter.
The oil should not
usually contain any metal particles during normal operation, but small particles
of metal will break off and get into the oil if a component is beginning to wear
badly or break up.
These then stick to the
magnet of the chip detector as they flow past it and will short out the two
contacts, thereby setting off an alarm to the pilot that something is
wrong.
The two Maintenance
Manual references will refer to the manufacturer’s instructions describing the
correct procedure to the engineers for removing and inspecting these components.
Oil filter
checks are routinely made
every time an oil change is done on an aircraft, but can also be called for in a
case where an investigation is being made into a potential failure situation.
The oil filter is
removed and replaced and the old filter is then sent off to a specialist company
to be analysed.
They cut the filter open
and make a spectroscopic
analysis of any particles that
are found in the filter paper to accurately determine the chemical composition
of the particles.
In-flight alarms
If any particles are
found in the oil, this test will reveal exactly what metal or alloy they are
made of, and this data can be used by the aircraft manufacturer to determine
exactly which component in an engine or gearbox they are likely to have come
from.
These tests are
routinely made every time the oil is changed in aircraft engines and gearboxes,
and usually allow component failures to be detected long before they become
serious.
M’ARMS Vibration Health
Monitoring System stands for “Aircraft
Recording and Monitoring System”.
It is an electronic vibration detector fitted to some aircraft engines and
gearboxes in order to alert the crew to abnormal vibration in the engine or
gearbox.
The
system, which is not fitted to all aircraft, will give the crew additional
information about the seriousness of any engine or gearbox-related problem
should another indication alarm (such as a chip detector) go off during flight.
Data
from this will most likely be recorded on the aircraft’s flight data recorder as
well.
The
M’ARMS system is also useful because it records vibration and engine exceedance
data (i.e. if the engine has been mistreated by over-speeding, or
over-torqueing, etc.) on previous flights.
Airbus Helicopters says
that it “welcomes the announcement made by the Accident Investigation Board
Norway (AIBN) and “continues to provide its full support to the AIBN
investigation.”
AP
