Originally Posted by
n305fa
The OH life of the MGB including epicyclic is 2500 hrs on the EC225, the planets have an ultimate life of 5000 hrs from memory.
Here is my summary on TBO.
The MGB had a total flight time of 2300 hours before OH according to the
PR agency Zync reports to media. (Incl 4 extensions of TBO, recorded in OEP)
Zync has also reported TBO is 2000 hours.
17. of January this was changed to a new unit. According to reports in the media.
At time of accident this unit had 1300 flying hours .
CHC Helikopterserice CEO claims during press conference they follow a maintenance program which says the gearbox is sent to a supplier for maintenance at 4400 hours. It could be wrongly cited, we are here talking about something else.
What is not clear is that Zync claims the AC had a new approval after 17 th of January for the MGB change. There is still no documentation stored in OEP about this. (until the accident it should at least be protocolled)
Originally Posted by
Concentric
Firstly, with reference to the AIBN Preliminary Report dated 27/5/16, Figure 4 shows the broken upper end of the front suspension bar which has clearly fractured in a ductile manner from a gross tensile overload, evidenced by the elongation of the male eye. Any suggestion that it was not properly pinned at either end or that the lower connecting lug bolts were incorrectly torqued contradicts the evidence. The bar must in fact have been very well restrained and under a tensile force much greater than its design load before it failed in this manner, assuming it was made of the correct material. For anything not designed to, other than the pins and bolts, to have transmitted this force is, frankly, far-fetched. For the front bar at least, it would also appear that the direction of loading was close to its normal arrangement as the pin is not bent and failure was across minimum tensile section.
It could be also a scenario, that the rear susp bars are sheared off the fuselage
(on picture in prel report it looks like this).
Then it could be the remaining front susp bar could already be in such torsion
that the upper mount have recieved all of the bending torque, of the rotor on its way loose.
Originally Posted by
Concentric
Secondly, the ATC radar plot (Figure 1) gives a timeline and some indication of groundspeed of LN-OJF. The radar returns are at approximately 4 second intervals and the (straight line) distance covered between 09:54:44 and 09:54:48 is only about 50% of that covered in the preceding 4 seconds. If I have scaled off the map correctly, the initial groundspeed appears to be approximately 148 knots but the average groundspeed for the 4 seconds after 09:54:48 appears to be approximately 74 knots (it could be higher if the aircraft followed an S-turn). The CVFDR is reported to have shown everything ‘normal until a sudden catastrophic failure developed in 1-2seconds’.
The (average) groundspeed after 09:54:48 scales as approximately 52 knots, by which time, taking the wind direction (190 – 200degrees) and final position of the MRH into account, the MRH had probably separated from the aircraft. Thereafter the fuselage would be a ballistic projectile with only air resistance having any effect on its groundspeed. Within the 4 seconds after 09:54:44 the aircraft had decelerated from 148 knots to slightly over 52 knots regardless of flight path. It is even possible it could have been during just the last 2 seconds of that interval.
This would appear to be a very high rate of horizontal deceleration (up to 2.5g) in addition to normal ‘g’ and any additional vertical acceleration and/or rotational acceleration. I will leave it to the professionals to suggest whether this is within normal airframe loading limits and how a helicopter can be made to decelerate this rapidly. Presumably it requires a very severe flare and the rotor to be attached? On top of mast axial loading such a rotation must impart a moment to the top of the gearbox, increasing load on the front suspension bar.
If we look at the take-off rate of climb, it is not much different to
the rate of deceleration before the incident. (Which could indicate a free fall)
I wouldnt put too much certainty in the recorded speed on the radar readings.
It could well be that the resolution is not small enough to include the exact speed
upon impact. The radar plots I have looked at (flightradar24) you see the
last recording is about 52 knots. It could well be the last recording upon ground impact. (That occured before the last recorded point on the radar)
In the very first reports of the accident in the a newspaper.
there where also an amateur video of the incident. You can see the aircraft coming
in at altitude, huge mechanical noise, the rotor shear of (not in focus on the film)
and there is a black cloud upon impact. The video then focus on the separated rotor flying its own way. (the same film after this moment is still public)
I refer to this only to avoid speculation of this part. I would say it came
in at normal altitude (400-600 m on the film) before it dropped
After seeing this I was in total shock.