Safety by design
Redesigned
vertical
shaft
on the EC225
All EC225 operators have resumed flights worldwide.
Meanwhile, progress toward a permanent solution has
continued:
• Unprecedented engineering efforts
• Collaboration with regulators, customers & external experts
• Solution designed and built with safety at its core
A Redesigned Shaft:
Starting soon, redesigned vertical gear shafts will be installed
on all EC225 helicopters.
Previous Design
New Design
Extensive test campaign on new shaft
- Eliminates ‘mud’ retention area
- Improved surface finish
- Eliminates small radius “hot spot":
stress concentration factor deleted
In order to confirm the robustness
of the new shaft and to gain
certification by EASA, the
European aviation regulator, three
kinds of tests were performed
using more than 15 shafts.
1: Fatigue tests in order to
demonstrate
the
safety
margins of the shaft and
substantiating 20.000 fh
Service Life Limit.
- Increased thickness:
reduces stress by ~ 2,7
The new design addresses all factors that,
in combination, caused the vertical shaft
rupture:
- Welding hole with improved
manufacturing process
and new plug
Factor 1:
Active corrosion definitively removed thanks to:
Smoother shape inside shaft to prevent retention areas
Improved lubrication by:
- Permanent flushing of the welding area by new oil jets
- Doubling oil volume injected inside shaft with two additional
lubrication holes thus limiting splines wear
- 4 lubrication holes:
doubling splines’ lubrication
- Increased thickness
to reduce stress level
2: Tests in the real main gear
box (MGB) with more than
200 hours of tests performed
on the power bench reflecting
the most stringent flight
profiles.
3: Flight tests in order to check
the integrity of the shaft
under
flight
conditions,
testing the total flight
envelope.
Factor 2:
Residual stress compensated thanks to:
- Reinforced design in welding area: can withstand 3x more
stress
Factor 3:
Stress concentrating factors (hot spots) gone thanks to:
- Improved shaft’s internal geometry to remove angles and
hot spots
1 - Test bench for fatigue tests.
What about the current protective measures?
The design of the new shaft followed one principal
purpose – to remove any and all cause for a
vertical shaft rupture.
Current maintenance constraints (shaft cleaning, US
NDI, and MOD45 onboard monitoring) are no longer
required.
The MOD45 continues to be monitored on the
ground by the HUMS ground station, as is done with
all dynamic components of the helicopter.
Monitoring data at the HUMS ground station
www.EC225news.com
2 - Tests on power bench.
3 - Flight tests
How do you technically proceed with the exchange?
The entire EC225 fleet will be retrofitted during the upcoming months.
The procedure will be:
• MGB removal by the operator
• Vertical shaft replacement inside the MGB main module by depot-level
qualified Airbus Helicopters specialists
• MGB reinstallation on aircraft by the operator
• MGB full test:
On test bench by Airbus Helicopters specialists or through ground run
by the operator
In-flight tests by the operator
• Aircraft released to service by the operator