DRIVESHAFT FAILURE
Yes, but a short shaft failure on a B206 that has an engine producing 300 shp one moment, which when suddenly unloaded, makes me wonder of the instantaneous engine acceleration that might occur, and how effective a hydromechanical GP or PT governor might be at limiting any resulting affects from that. I haven't seen a C20 fail before, but I have seen a C30 hand out free samples of expensive engine bits and pieces flung far and wide. It gets very messy very quickly.
how effective a hydromechanical GP or PT governor might be at limiting any resulting affects from that
Join Date: Sep 2014
Location: US
Posts: 16
Likes: 0
Received 0 Likes
on
0 Posts
Driveshaft Failure
The investigation results are not yet posted, but the below crash video mimics well what a short shaft failure might look like.
https://www.youtube.com/watch?v=aQUV_NwNHyQ
https://www.youtube.com/watch?v=aQUV_NwNHyQ
The investigation results are not yet posted, but the below crash video mimics well what a short shaft failure might look like.
Unless of course you know more than the NTSB.
but I have seen a C30 hand out free samples of expensive engine bits and pieces flung far and wide. It gets very messy very quickly.
I asked the question a few years ago for the 350...
http://www.pprune.org/rotorheads/229...t-failure.html
Some usefull info there
http://www.pprune.org/rotorheads/229...t-failure.html
Some usefull info there
Join Date: Jan 2009
Location: around and about
Age: 71
Posts: 280
Likes: 0
Received 1 Like
on
1 Post
GB, I think you are correct.
IIRC, several years ago there was a classic HF incident in Canada when for a chain of reasons, a B206 was wheeled out for gd runs/hover check after major maintenance. The Jesus nut had been left on the bench. Everything OK at ground idle, but, on wind up to flight idle, (and perhaps a little collective), the rotor departed the airframe. This was inconvenient,...... but the engine, relieved of its load, went to nose-bleed RPM on the N2 train. Result - welded PT wheels to the labyrinth seals on the casing. Only the Lord knows how many RPM, but certainly exceeded the plastic deformation of the wheels' constituent steel. This just for info - VFR
IIRC, several years ago there was a classic HF incident in Canada when for a chain of reasons, a B206 was wheeled out for gd runs/hover check after major maintenance. The Jesus nut had been left on the bench. Everything OK at ground idle, but, on wind up to flight idle, (and perhaps a little collective), the rotor departed the airframe. This was inconvenient,...... but the engine, relieved of its load, went to nose-bleed RPM on the N2 train. Result - welded PT wheels to the labyrinth seals on the casing. Only the Lord knows how many RPM, but certainly exceeded the plastic deformation of the wheels' constituent steel. This just for info - VFR
vfr, Ever seen someone run an MD500 without blades? The procedure is in the AMM to balance just the head.
How much torque do you really think there is at FL? All you are doing is removing that torque. Easily caught by the governor. .
I'm calling BS on this one.
How much torque do you really think there is at FL? All you are doing is removing that torque. Easily caught by the governor. .
I'm calling BS on this one.
I don't know about the MD500 but any helicopter with a rotor speed governing system will quite happily run with both engines running with the rotor blades removed.
Quite difficult to believe in some cases. I remember running a 332 in storage without blades and the engineer beside me was having kittens as I went through the normal start with the first engine and then straight into the second.
It was sitting quite happily at about 270 Rrpm with both engines well above Idle.
Quite difficult to believe in some cases. I remember running a 332 in storage without blades and the engineer beside me was having kittens as I went through the normal start with the first engine and then straight into the second.
It was sitting quite happily at about 270 Rrpm with both engines well above Idle.
On either the Arrius or Arriel engine course (can't remember which) at Turbomeca it was said that the primary overspeed protection (certification requirement) was blade shedding with the electrical overspeed system being secondary.
In the early 80's the BO 105 had a problem with freewheel slippage which manifested itself as
100% N2 with idle N1. End result was that the freewheel would re-engage on shut down destroying the driveshaft. What you saw depended on whether one or both engines were running.
In the early 80's the BO 105 had a problem with freewheel slippage which manifested itself as
100% N2 with idle N1. End result was that the freewheel would re-engage on shut down destroying the driveshaft. What you saw depended on whether one or both engines were running.
Join Date: Jan 2009
Location: around and about
Age: 71
Posts: 280
Likes: 0
Received 1 Like
on
1 Post
OK, RVDT, I see your point .........
HOWEVER I requested and borrowed the graphics of the resultant damage (and still use them in initial HF courses to emphasise the importance of 2nd inspections). To correct my post, perhaps I should have stressed this was into a hover, and probably the machine was heavy. The resultant departure of the head was apparently 'unexpected' (!!) - but the damage was extreme, I promise you. But thank you for pointing out the lack of specifics in my post, safe flying - VFR
PS on a rethink, the reason it all went pear-shaped was simply because the Jesus nut was not fitted, RPM at 100%Nr, min-blade pitch angle and the split cones dropped out. Then in just one revolution the trunnion dropped putting o-my-God collective pitch to an energy charged M/R, Sorry forgetful - must be an ageing thing LOL
HOWEVER I requested and borrowed the graphics of the resultant damage (and still use them in initial HF courses to emphasise the importance of 2nd inspections). To correct my post, perhaps I should have stressed this was into a hover, and probably the machine was heavy. The resultant departure of the head was apparently 'unexpected' (!!) - but the damage was extreme, I promise you. But thank you for pointing out the lack of specifics in my post, safe flying - VFR
PS on a rethink, the reason it all went pear-shaped was simply because the Jesus nut was not fitted, RPM at 100%Nr, min-blade pitch angle and the split cones dropped out. Then in just one revolution the trunnion dropped putting o-my-God collective pitch to an energy charged M/R, Sorry forgetful - must be an ageing thing LOL
Last edited by vfr440; 30th Aug 2016 at 18:31. Reason: Added very relevant PS, apologies
Actually, VFR, I thought if was obvious what you described and I got it first time!
OK, RVDT, I see your point .........
HOWEVER I requested and borrowed the graphics of the resultant damage (and still use them in initial HF courses to emphasise the importance of 2nd inspections). To correct my post, perhaps I should have stressed this was into a hover, and probably the machine was heavy. The resultant departure of the head was apparently 'unexpected' (!!) - but the damage was extreme, I promise you. But thank you for pointing out the lack of specifics in my post, safe flying - VFR
PS on a rethink, the reason it all went pear-shaped was simply because the Jesus nut was not fitted, RPM at 100%Nr, min-blade pitch angle and the split cones dropped out. Then in just one revolution the trunnion dropped putting o-my-God collective pitch to an energy charged M/R, Sorry forgetful - must be an ageing thing LOL
HOWEVER I requested and borrowed the graphics of the resultant damage (and still use them in initial HF courses to emphasise the importance of 2nd inspections). To correct my post, perhaps I should have stressed this was into a hover, and probably the machine was heavy. The resultant departure of the head was apparently 'unexpected' (!!) - but the damage was extreme, I promise you. But thank you for pointing out the lack of specifics in my post, safe flying - VFR
PS on a rethink, the reason it all went pear-shaped was simply because the Jesus nut was not fitted, RPM at 100%Nr, min-blade pitch angle and the split cones dropped out. Then in just one revolution the trunnion dropped putting o-my-God collective pitch to an energy charged M/R, Sorry forgetful - must be an ageing thing LOL
The Bell 206 accident in Hawaii is far from explained by the NTSB. They only say that they pulled the thing out of the water and all of the big structural pieces are accounted for.
Luckily there is video evidence of the last few seconds of the flight. This video shows a fairly shallow approach that suddenly gets interrupted. The video contradicts the pilot's statements that he initiated an autorotation to include a left pedal turn to land parallel to the shoreline. That simply did not happen. The videographer's statement was that the helicopter was coming in low and straight. Doesn't sound autorotative to me...
What we can see AND HEAR is the end of a fairly shallow approach. All of a sudden the ship plummets out of the sky, accompanied by the very clear sound of the tail rotor rpm *increasing* as the 206B's notoriously slow N2 governor, taken quite by surprise hadn't yet caught up with the lack of load. And there was a slight left yaw which would also be expected. This can ONLY be caused by one thing: Main driveshaft failure.
No matter what the pilot *says* happened, he's wrong. We always get it wrong. Whether he's being deliberately dishonest or just remembers things wrong doesn't really matter. I'd guess that it all happened too fast for his puny brain to comprehend, and felt that he had to immediately come up with an explanation of why he crashed. CYA? Why not just shrug and say, "I dunno, I don't remember. I'll get back to you when my memory of the event is more clear."
So don't think that the NTSB has ruled on that one yet.
Luckily there is video evidence of the last few seconds of the flight. This video shows a fairly shallow approach that suddenly gets interrupted. The video contradicts the pilot's statements that he initiated an autorotation to include a left pedal turn to land parallel to the shoreline. That simply did not happen. The videographer's statement was that the helicopter was coming in low and straight. Doesn't sound autorotative to me...
What we can see AND HEAR is the end of a fairly shallow approach. All of a sudden the ship plummets out of the sky, accompanied by the very clear sound of the tail rotor rpm *increasing* as the 206B's notoriously slow N2 governor, taken quite by surprise hadn't yet caught up with the lack of load. And there was a slight left yaw which would also be expected. This can ONLY be caused by one thing: Main driveshaft failure.
No matter what the pilot *says* happened, he's wrong. We always get it wrong. Whether he's being deliberately dishonest or just remembers things wrong doesn't really matter. I'd guess that it all happened too fast for his puny brain to comprehend, and felt that he had to immediately come up with an explanation of why he crashed. CYA? Why not just shrug and say, "I dunno, I don't remember. I'll get back to you when my memory of the event is more clear."
So don't think that the NTSB has ruled on that one yet.
Join Date: Sep 2007
Location: USA
Posts: 601
Likes: 0
Received 0 Likes
on
0 Posts
The worst rotorcraft driveshaft failure example I can imagine would be the CH-47's interconnect drive between the fwd/aft rotors. The 1982 Mannheim crash is a very graphic example of what happens when the interconnect drive system fails on a CH-47 tandem helo.
The most complicated rotorcraft driveshaft system I can think of is the V-22 cross-wing interconnect. Three gearboxes (2 TAGB & 1 MWGB), a dozen or so driveshaft sections, a similar number of hangar bearings, and a large number of diaphragm type flex couplings. What makes things difficult with this particular application is the driveshaft system must accommodate flexing of the wing structure. The V-22 interconnect drive system's primary function is to power both rotors during OEI operation. And failure of the drive system during certain OEI operating conditions (hover, transition, etc) can be catastrophic. The 1992 Quantico crash was an example of a driveshaft failure during transition and OEI conditions.
The most complicated rotorcraft driveshaft system I can think of is the V-22 cross-wing interconnect. Three gearboxes (2 TAGB & 1 MWGB), a dozen or so driveshaft sections, a similar number of hangar bearings, and a large number of diaphragm type flex couplings. What makes things difficult with this particular application is the driveshaft system must accommodate flexing of the wing structure. The V-22 interconnect drive system's primary function is to power both rotors during OEI operation. And failure of the drive system during certain OEI operating conditions (hover, transition, etc) can be catastrophic. The 1992 Quantico crash was an example of a driveshaft failure during transition and OEI conditions.
Join Date: May 2008
Location: St Johns, Newfoundland,Canada
Posts: 330
Likes: 0
Received 0 Likes
on
0 Posts
vfr440
Re your post referring to the Canadian Jesus Bolt. You might want to pull up the TSB report and read before posting bull****.
The Pilot and Engineer sadly killed in this incident were colleagues and highly experienced operators. The A/C actually disintegrated in flight due rotor separation, as you correctly state due lack of JB. There was not a lot left for the TSB to investigate, except the JB sitting in an apprentice engineers tool box. Very sad I remember the phone call.
Re your post referring to the Canadian Jesus Bolt. You might want to pull up the TSB report and read before posting bull****.
The Pilot and Engineer sadly killed in this incident were colleagues and highly experienced operators. The A/C actually disintegrated in flight due rotor separation, as you correctly state due lack of JB. There was not a lot left for the TSB to investigate, except the JB sitting in an apprentice engineers tool box. Very sad I remember the phone call.
Join Date: Sep 2014
Location: US
Posts: 16
Likes: 0
Received 0 Likes
on
0 Posts
Pearl Harbor 206 crash
Join Date: May 2013
Location: Canada
Posts: 71
Likes: 0
Received 0 Likes
on
0 Posts
Lessons learned?
So there was discolouration on the coupling and the temp strips were missing.
We check these on every pre-flight.
In the spirit of a lesson not being learned unless a behaviour is changed, is there anything else to look out for on a pre-flight, maybe grease being thrown around? We don't check for any lash or play in the shaft, does anyone else?
V7
We check these on every pre-flight.
In the spirit of a lesson not being learned unless a behaviour is changed, is there anything else to look out for on a pre-flight, maybe grease being thrown around? We don't check for any lash or play in the shaft, does anyone else?
V7
Join Date: Jul 2008
Location: Canada
Posts: 309
Likes: 0
Received 0 Likes
on
0 Posts
Last time I have flown the B212 was about 9 years ago so I am a bit rusty on the procedures. Last I flew the aircraft, I was the company training pilot on the 212 and 205 and was told and shown a new training procedure for the 212 but not the 205 (don't know why, 205 is in the same situation) and the procedure was called Main driveshaft failure training, here also called shortshaft or power shaft. The training was to recognize what happened in flight when the failure occur and what to do about it.
This came about due to 2 recent (at the time) accident in the US military where 2 212 crashed with lost of lives and it was found out that the problem was due to a powershaft failure AND the wrong response to it by the pic.
According to the report both pilots in both accident had the reaction of pulling collective up to slow down RPM to investigate the problem.
Doesn't take much to loose rotor RPM especially when the engines are not connected anymore to the trany and RPM would come down to a point of no recovery possible.
I do not have the paperwork related to it but it showed dual tach and different needles position depending if it was a powershaft failure or gov-overspeed etc.
Don't know if they are still training for that nowadays.
jD
This came about due to 2 recent (at the time) accident in the US military where 2 212 crashed with lost of lives and it was found out that the problem was due to a powershaft failure AND the wrong response to it by the pic.
According to the report both pilots in both accident had the reaction of pulling collective up to slow down RPM to investigate the problem.
Doesn't take much to loose rotor RPM especially when the engines are not connected anymore to the trany and RPM would come down to a point of no recovery possible.
I do not have the paperwork related to it but it showed dual tach and different needles position depending if it was a powershaft failure or gov-overspeed etc.
Don't know if they are still training for that nowadays.
jD
but I have seen a C30 hand out free samples of expensive engine bits and pieces flung far and wide
the S76 tail rotor drive is geared between the two engine inputs
Each engine has a separate power train all the way up to the bull gear through a single spur and a single bevel mesh. The tail takeoff is from the left engine power train. In case of a left engine failure the tail takeoff still drives through the right engine to the bull gear back through the bevel set to the tail take off.
Sikorsky Archives | S-76
Last edited by megan; 24th Feb 2018 at 05:23.
A good reason for not doing ground runs to find where the problem is when the trend check has taken a massive nose dive.Sir Korsky, most of the schematics I've seen would have you interpret that as being the case, because the orientation of the graphic is so poor. See below for a clearer view. You can see the tail rotor is only driven from the #1 engine side. As Sikorsky saysSo its theoretically possible for a #1 engine drive failure into the MGB where #2 is what supplies main rotor power and you you have to keep #1 running to drive the tail rotor ie shutting down #1 will deprive you of tail rotor drive. A fact I've never seen pointed out in training or simulator.
Sikorsky Archives | S-76
Sikorsky Archives | S-76
Have you not started No 2 first and seen the main and tail rotors spin up together?