roll over , sudden stoppage
Thread Starter
Joined: Mar 2003
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From: the hills of halton
roll over , sudden stoppage
Interested about what differerent Maint manuals say about sudden stoppage. Eurocopter 350 manual is very specific about which parts to scrap and which to overhaul.
What about other maufacturers ?.
What about other maufacturers ?.
Joined: Feb 2002
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From: N20,W99
posted 30th July 2003 21:15 ___ _____ _
To add to your question, it would also be nice to add the differences between what exactly do manufacturers consider "sudden stoppage"
Here is a personal story.
when I got my very first initial training in the 206, I was practicing 360 and during the final approach it was obvious we were short to the landing spot so after quickly rolling on power to recover the engine stalled many consecutive times, so we just continued to the ground and touched down on a very muddy surface. Next thing I know the skids digged themselves into the ground and the machine was tipping over on its nose, I only remember seeing the blades inches of the ground before it miraculously went back to level, my instructor only breathed deeply and said "that was scary".
Anyway we agreed not to roll the throttle so quickly to avoid stalls (common if you are rough with throttle at 8,000FT) did a couple more and went home, after shutting down I was walking around the acft. to check everything was in place and noticed the top 1or2 inches of left vertical fin was graciously curved inboard (like an upside down U), the blade seemed, no apparent damage, being an authorized Bell service center the machine was quickly inspected and it was determined that the underside of the blade about 4 inches from the leading edge had contacted the fin, note the blade did not even hit with the leading edge, it was the underside of the blade, and the blade damage was minimal, within limits for service according to Bell, well anyway after sending some pics to Bell asking how this should be handled they immediately transmission said "sudden stoppage", blades, transmission, mast, even the tailrotor drive-shafts had to go!
This was in an L4 in which almost everything is considered sudden stoppage, now listen to this, we recently had an L1 in for repair which had hit the ground very hard it nosed over an the blades DID hit the ground, it was really messy, in the L1 which is almost the same identical helicopter concept, the manual says that if the mast is NOT bent then it is NOT fully treated as sudden stoppage! This meant for example that the mast in the wrecked helicopter is still flying today since it was not bent, but the mast in the L4 that slapped the fin with barely any blade damage became a beautiful lamp!
It doesn't end here, just this last saturday the factory sent over an instructor from the U.S. to give recurrent training to the one and only pilot of the one and only Enstrom 480B (turbine) in the country, they go out, this instructor has never flown at this altitude, and during one of the practice autos something goes funny as it is usual up here and the horrible 480B sinks to the ground hits hard and blows of one of the fins, blade is pretty scratched, fin is missing its upper corner, Enstrom's maintenance procedure? Repair that same fin (glue a the missing piece on) check for damage in a couple of spots and it was flying the next day!
Strange world ain't it?
To add to your question, it would also be nice to add the differences between what exactly do manufacturers consider "sudden stoppage"
Here is a personal story.
when I got my very first initial training in the 206, I was practicing 360 and during the final approach it was obvious we were short to the landing spot so after quickly rolling on power to recover the engine stalled many consecutive times, so we just continued to the ground and touched down on a very muddy surface. Next thing I know the skids digged themselves into the ground and the machine was tipping over on its nose, I only remember seeing the blades inches of the ground before it miraculously went back to level, my instructor only breathed deeply and said "that was scary".
Anyway we agreed not to roll the throttle so quickly to avoid stalls (common if you are rough with throttle at 8,000FT) did a couple more and went home, after shutting down I was walking around the acft. to check everything was in place and noticed the top 1or2 inches of left vertical fin was graciously curved inboard (like an upside down U), the blade seemed, no apparent damage, being an authorized Bell service center the machine was quickly inspected and it was determined that the underside of the blade about 4 inches from the leading edge had contacted the fin, note the blade did not even hit with the leading edge, it was the underside of the blade, and the blade damage was minimal, within limits for service according to Bell, well anyway after sending some pics to Bell asking how this should be handled they immediately transmission said "sudden stoppage", blades, transmission, mast, even the tailrotor drive-shafts had to go!
This was in an L4 in which almost everything is considered sudden stoppage, now listen to this, we recently had an L1 in for repair which had hit the ground very hard it nosed over an the blades DID hit the ground, it was really messy, in the L1 which is almost the same identical helicopter concept, the manual says that if the mast is NOT bent then it is NOT fully treated as sudden stoppage! This meant for example that the mast in the wrecked helicopter is still flying today since it was not bent, but the mast in the L4 that slapped the fin with barely any blade damage became a beautiful lamp!
It doesn't end here, just this last saturday the factory sent over an instructor from the U.S. to give recurrent training to the one and only pilot of the one and only Enstrom 480B (turbine) in the country, they go out, this instructor has never flown at this altitude, and during one of the practice autos something goes funny as it is usual up here and the horrible 480B sinks to the ground hits hard and blows of one of the fins, blade is pretty scratched, fin is missing its upper corner, Enstrom's maintenance procedure? Repair that same fin (glue a the missing piece on) check for damage in a couple of spots and it was flying the next day!
Strange world ain't it?
Iconoclast
Joined: Sep 2000
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From: The home of Dudley Dooright-Where the lead dog is the only one that gets a change of scenery.
The meaning of a word. You say one thing and the other guy hears another word.
To: BlenderPilot
You used the term stalls. Bell may have interpreted this as compressor stalls, which in truth may have been the case. If you have experienced a compressor stall the entire driveline and dynamic system is changed (but only after a detailed inspection). We experienced compressor stalls on our 214s in Iran and the same was true for them when a compressor stall happened. In some cases parts of the fuselage were changed. Of course there is a big difference in the horsepower of the 206 and the 214 engines with the application of instantaneous torque being applied to the respective drivetrains and dynamics.
I don’t know the design geometry of the 206 but how can a blade hit a fin. Is there a possibility that the transmission tilted backwards when the helicopter nosed over and the pilot may have pulled aft cyclic.
You used the term stalls. Bell may have interpreted this as compressor stalls, which in truth may have been the case. If you have experienced a compressor stall the entire driveline and dynamic system is changed (but only after a detailed inspection). We experienced compressor stalls on our 214s in Iran and the same was true for them when a compressor stall happened. In some cases parts of the fuselage were changed. Of course there is a big difference in the horsepower of the 206 and the 214 engines with the application of instantaneous torque being applied to the respective drivetrains and dynamics.
I don’t know the design geometry of the 206 but how can a blade hit a fin. Is there a possibility that the transmission tilted backwards when the helicopter nosed over and the pilot may have pulled aft cyclic.
Joined: Feb 2002
Posts: 1,119
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From: N20,W99
Dear Lu,
Well I did get compressor stalls, like the ones you get when you roll the throttle on too quickly sometimes. And let me see if I understand this correctly, you are telling me you have to change the entire driveline and dynamic system? I have gotten compressor stalls many times at this altitude and I have never seen anything having to be replaced except maybe the FCU for not functioning properly.
On how the blade hit the fin, well this is pretty simple to do in the L4, things that can cause a "fin hit" can be, lowering collective too quickly after a touchdown auto, pulling cyclic back beyond neutral during a running auto landing, high wind gusts during starting and shut down, I guess its sort of "easy" in the 206L series, and the interesting thing is that if your barely hit the fin, that means your were about 2 inches away from hittng the TR driveshaft covers (boom). The transmision does have that Nodamatic system which makes flying the L series sort of like riding a magic carpet in terms of smooth ride, but it does allow for some limited movement, but not enough for the blades to contact the fins, the blades need to be flexed down for this to happen.
Tomorrow I will take a pic of a flapped down blade in a 206L and you will see how close the blade gets to the fin.
Well I did get compressor stalls, like the ones you get when you roll the throttle on too quickly sometimes. And let me see if I understand this correctly, you are telling me you have to change the entire driveline and dynamic system? I have gotten compressor stalls many times at this altitude and I have never seen anything having to be replaced except maybe the FCU for not functioning properly.
On how the blade hit the fin, well this is pretty simple to do in the L4, things that can cause a "fin hit" can be, lowering collective too quickly after a touchdown auto, pulling cyclic back beyond neutral during a running auto landing, high wind gusts during starting and shut down, I guess its sort of "easy" in the 206L series, and the interesting thing is that if your barely hit the fin, that means your were about 2 inches away from hittng the TR driveshaft covers (boom). The transmision does have that Nodamatic system which makes flying the L series sort of like riding a magic carpet in terms of smooth ride, but it does allow for some limited movement, but not enough for the blades to contact the fins, the blades need to be flexed down for this to happen.
Tomorrow I will take a pic of a flapped down blade in a 206L and you will see how close the blade gets to the fin.
Joined: Jun 2003
Posts: 288
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From: USA
Dear Blender Pilot,
If Lu is not correct about possible replacement of components, he should be. Pilots and engineers are often shocked when they see drive train load data after even minor compressor surge and/or stall events. These events are often referred to as "ringing" the drive train and the reduction in component lives can be significant. Repetitive turbine engine compressor surge/stall events should not be taken lightly.
Best Regards, Rich
If Lu is not correct about possible replacement of components, he should be. Pilots and engineers are often shocked when they see drive train load data after even minor compressor surge and/or stall events. These events are often referred to as "ringing" the drive train and the reduction in component lives can be significant. Repetitive turbine engine compressor surge/stall events should not be taken lightly.
Best Regards, Rich
