S76 down in Baltic Sea (Now incl NTSB Safety Recommendation)
Strangely enough, I have experienced something looking similar on Flight Safety' simulator the other day. We were simulating a "collective drive" situation with a jaming after the mixing unit; (rudder pedals inefficient and linked to collective) Everything was going not too badly at about 130 kts untill I slowly tried to reduce speed to about 80 kts for an IMC let down. For some reason everything went messy from here ; speed reduced to about 60 Kts, and when I tried to increase it again ,I had a shard nose up motion with (I believe) a left yaw I couldn't counter (collective drive situation) I cannot tell if the yaw then reversed the other side (I was IMC)
It ended up quickly in a simulated crash, with 3 pairs of staring wide eyes,and adrenalyn pumping...in the darkness of this diabolic box. Frightening !
But is the simulator faithfull enough to simulate situations at the edge of flight enveloppe ?
It ended up quickly in a simulated crash, with 3 pairs of staring wide eyes,and adrenalyn pumping...in the darkness of this diabolic box. Frightening !
But is the simulator faithfull enough to simulate situations at the edge of flight enveloppe ?
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I was an instructor in the 76, and have quite a few hours in it. It is difficult to diagnose on the basis of so little info, but I think you guys are on the right track. It looks like a jammed or broken tail rotor cable could have been the culpret.
With a powerful tail rotor intact, but driven to full angle, a slowdown from cruise will make the aircraft spin, and the collective driving is a symptom of the pilot's foot trying to push pedal against the jam, and instead back-driving the collective. The nose pitch up and such are artifacts of the strong yaw to pitch coupling of the airframe, so that a left yaw at high speed looks like a strong pitch up.
I wonder what maintenance was performed in the several hours before the accident, if the tail cable was touched, it could be a sign.
With a powerful tail rotor intact, but driven to full angle, a slowdown from cruise will make the aircraft spin, and the collective driving is a symptom of the pilot's foot trying to push pedal against the jam, and instead back-driving the collective. The nose pitch up and such are artifacts of the strong yaw to pitch coupling of the airframe, so that a left yaw at high speed looks like a strong pitch up.
I wonder what maintenance was performed in the several hours before the accident, if the tail cable was touched, it could be a sign.
This collective pitch/yaw coupling on the S76 is a bitch to understand, cannot be practiced if not in a sim, definitely not user friendly and can have a nasty outcome: 37 seconds between the TR control problem and the crash - assuming of course it's the primary cause. I wonder how this system made it through the certification process.
ATN
ATN
Yes, and when I try to understand it a little deeper it makes me suspect the designer was (or is) not a human beeing, a bit like the pyramids mystery. Beside this, I believe this "collective drive" situation due to a jamming beyond the mixing unit is extremly rare ( I have the knowledge of only one case, with a succesfull landing )
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ATN and cpt,
I think you do not understand the mixing on the S76 and its implications, certainly not enough to make those comments.
It is not possible for the mixer to have caused the accident. It is possible for the mixer to have confused you enought to believe otherwise.
PM me or repost, and I will be glad to explain the system.
I think you do not understand the mixing on the S76 and its implications, certainly not enough to make those comments.
It is not possible for the mixer to have caused the accident. It is possible for the mixer to have confused you enought to believe otherwise.
PM me or repost, and I will be glad to explain the system.
There is an Urban Myth, first heard at FSI, that the original 76 didn't have that complex mixing unit. The engineers put together a system that looked like it would work, and all the external airframe designer had to do was create a bulge on the left transmission to accommodate one of the servos, which poked out a bit.
Oh, no, says the designer, the external appearance must be smooth and sleek. Move the servo so it doesn't poke out. So, the servo was moved and that nightmare mixing unit was devised to allow the control runs (already fixed in the design) to still operate.
Makes a nice story, anyway - thanks Eber!
Oh, no, says the designer, the external appearance must be smooth and sleek. Move the servo so it doesn't poke out. So, the servo was moved and that nightmare mixing unit was devised to allow the control runs (already fixed in the design) to still operate.
Makes a nice story, anyway - thanks Eber!
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Eber Wright is one of those Flight Safety guys with too much time and too few facts. He can call me to get this one straight, after all, I was there! This bulge crap is an old - wrong- wives tale. The need for a mixer on the 76 was dictated when the delta three coupling was added. I was on the team that did so, and would be glad to provide the details. RJSquirrel is right, the mixer is not a source of black magic, nor is it at all likely to cause a problem.
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When we had our 76A at beginning of 80s I don't recall "Collective Drive" being discussed at original American Airlines Ground School or subsequent Flight Safety Sim visits. However I did encounter Collective/Pedal interlock which was subsequently put down to the Pitch Change Shaft jamming, I believe because tho splined for 6? only fitted with two keys. At cruise position the keys chattered and wore notches thus if keys not exactly in line with spline, the shaft couldn't move, so everytime tried to move pedals collective moved.
Don't see this would cause anything as dramatic as this accident and has probably been addressed in subsequent 20+years.
Don't see this would cause anything as dramatic as this accident and has probably been addressed in subsequent 20+years.
332m,
Which is best...."logical" or precise?
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Which is best...."logical" or precise?
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Hi rjsquirrel,
For sure I'll always be happy to follow a specialised course on S76 flight controls (with a very patient instructor) .
I know amongst other thinks that, with a high position of collective pitch and right pedal application, we reach a point where the linkage is positioned in such a manner that rudder pedal movment is impaired.
I don't have the faintest idea of what caused this poor S76 to crash, but apparently, there is evidence of "extreme" collective up position and an initial violent yaw to left...
My case on the sim at F.Safety was different in a sense that we were simulating a mechanical link jamming aft of the mixing unit. Nevertheless at one stage I also had to cope with a rapid nose-up attitude and a left yaw (probably when I lowered collective)
Please mail me at: [email protected] if you feel patient enough to enlight me on this flight controls matter.
For sure I'll always be happy to follow a specialised course on S76 flight controls (with a very patient instructor) .
I know amongst other thinks that, with a high position of collective pitch and right pedal application, we reach a point where the linkage is positioned in such a manner that rudder pedal movment is impaired.
I don't have the faintest idea of what caused this poor S76 to crash, but apparently, there is evidence of "extreme" collective up position and an initial violent yaw to left...
My case on the sim at F.Safety was different in a sense that we were simulating a mechanical link jamming aft of the mixing unit. Nevertheless at one stage I also had to cope with a rapid nose-up attitude and a left yaw (probably when I lowered collective)
Please mail me at: [email protected] if you feel patient enough to enlight me on this flight controls matter.
Safety officials to look into Copterline's operating procedures
Surprise inspections also planned for domestic airlines
The Finnish Civil Aviation Administration (FCAA) have decided to evaluate the entire operating procedures of the ill-fated commercial operator Copterline, whose helicopter crashed into the Gulf of Finland just outside of Tallinn a little over a month ago, killing all fourteen people on board.
The report published on Monday reads that although the reason for the crash remains unclear it is reasonable to call for a re-evaluation of Copterline's flight operations after such a serious accident. According to Kim Salonen, the director of the Flight Safety Authority at the FCAA, it is better to go through the operations now rather than to wait for a year for the completion of the accident report.
Salonen emphasises that Copterline is not suspected of any specific shortcomings in its operations. Rather, this is a matter of double-checking if safety could somehow be improved. "We will go through weather restrictions, refresher training, and safety equipment. Everything related to flying, basically." Copterline director Jorma Kalhola views FCAA's estimate as a resonable one. "The authorities' actions are also going to be evaluated."
The report establishes that regular helicopter services are rare even on a global scale, and therefore the safety of Copterline's operation is difficult to gauge in the light of statistics. The report avoids looking into the reasons for the accident, which are subject to investigation by an examination board in Estonia. The report merely states that the accident resulted from a sudden event that was beyond the control of the pilots. According to the Minister of Transport and Communications Leena Luhtanen - who requested the report - there is no need for drastic measures on account of the accident.
The report also reveals that the Flight Safety Authority want to start performing random inspections on domestic airlines and to increase the number of inspections carried out on foreign carriers. This was prompted by the numerous serious air crashes this summer. Department chief Eero Kausalainen at the Flight Safety Authority says the random inspections of domestic carriers' planes will be an addition to check-ups already performed at regular intervals.
According to International Civil Aviation Organisation (ICAO) norms, surprise inspections are to be carried out evenly and impartially on all airlines. Since 1997, around 30 to 40 foreign planes have been subjected to random inspections each year. Last year's number of random checks was 51. This year about 80 planes will go through an unscheduled examination.
Surprise inspections also planned for domestic airlines
The Finnish Civil Aviation Administration (FCAA) have decided to evaluate the entire operating procedures of the ill-fated commercial operator Copterline, whose helicopter crashed into the Gulf of Finland just outside of Tallinn a little over a month ago, killing all fourteen people on board.
The report published on Monday reads that although the reason for the crash remains unclear it is reasonable to call for a re-evaluation of Copterline's flight operations after such a serious accident. According to Kim Salonen, the director of the Flight Safety Authority at the FCAA, it is better to go through the operations now rather than to wait for a year for the completion of the accident report.
Salonen emphasises that Copterline is not suspected of any specific shortcomings in its operations. Rather, this is a matter of double-checking if safety could somehow be improved. "We will go through weather restrictions, refresher training, and safety equipment. Everything related to flying, basically." Copterline director Jorma Kalhola views FCAA's estimate as a resonable one. "The authorities' actions are also going to be evaluated."
The report establishes that regular helicopter services are rare even on a global scale, and therefore the safety of Copterline's operation is difficult to gauge in the light of statistics. The report avoids looking into the reasons for the accident, which are subject to investigation by an examination board in Estonia. The report merely states that the accident resulted from a sudden event that was beyond the control of the pilots. According to the Minister of Transport and Communications Leena Luhtanen - who requested the report - there is no need for drastic measures on account of the accident.
The report also reveals that the Flight Safety Authority want to start performing random inspections on domestic airlines and to increase the number of inspections carried out on foreign carriers. This was prompted by the numerous serious air crashes this summer. Department chief Eero Kausalainen at the Flight Safety Authority says the random inspections of domestic carriers' planes will be an addition to check-ups already performed at regular intervals.
According to International Civil Aviation Organisation (ICAO) norms, surprise inspections are to be carried out evenly and impartially on all airlines. Since 1997, around 30 to 40 foreign planes have been subjected to random inspections each year. Last year's number of random checks was 51. This year about 80 planes will go through an unscheduled examination.
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Copterline accident
This accident remains quite a mystery. The team (Sikorsky,
NTSB, Estonian authorities, Turbomeca, etc.) are still unable to find any
"smoking gun" associated with the accident. So far, no technical problem
has been found. The MGB has been examined and nothing abnormal was found their, either.
The U. S. NTSB is giving this accident a high priority and is ready to utilize their full range of resources to try and determine the primary cause of the accident.
Press release__________
Sent: Tue Sep 13 01:08:21 2005
Subject: Estonian investigation commission rules out engine failure as cause of August helicopter crash
Estonian investigation commission rules out engine failure as cause of
August helicopter crash
18:59, 12. september 2005
TALLINN, Sep 12, BNS - A commission set up in Estonia to investigate the crash near Tallinn last month of a helicopter of the Finnish Copterline company has ruled out breaking off of the rotor blade and engine failure as the causes of the accident but has so far failed to establish why the chopper crashed.
"We've a fairly true picture of how everything happened but unfortunately we're unable to say why it happened," the chairman of the Economy and Communications Ministry commission probing into the helicopter accident, Taivo Kivistik, told reporters today.
His deputy, Tonu Ader, said the commission has as a result of the investigation ruled out several earlier theories about possible causes of the accident. He declined to say which versions the investigators consider the more likely so as to avoid speculation.
The probe did not establish the breaking off of some parts while the helicopter was in air, Ader said. The parts separated from the chopper were lying near the wreck on the bottom of the sea and the only part lying farther away from the wreck was a blade of the main rotor.
"The commission has serious grounds to eliminate the breaking off of the main rotor blade as a cause of the crash," Ader said.
According to Ader, the commission reached the conclusion that the blade found at a distance from the wreck did not break off until the helicopter hit water. He made it clear that all four blades had broken off and had sustained relatively similar damage.
The commission also ruled out the possibility of the engines failing during flight. Ader said the engines continued working till almost the moment the helicopter struck water.
The helicopter started behaving inexplicably around 37 seconds before plunging into sea, Ader said. In his words, first its nose lifted up while the helicopter itself started to turn to its left side and away from its original course.
Then the chopper turned back right and started falling, making 13 full turns to the right, or one turn in 2.5 seconds on the average, until it hit water.
"The high speed of turning may indicate an overload which prevented the crew from getting control of the helicopter," Ader said.
According to him, the tape of the discussion between the pilot and the co-pilot showed that right before the zero-moment when things started to go wrong the pilot said, "Let's boost power," which was followed by an expression of surprise and, a few seconds later, by a very quiet Mayday
call repeated three times.
A bit later the co-pilot's question, "Have we lost the tail?" could be heard following which the recording contained no distinguishable phrases, he said.
According to Ader, clear evidence exists that the helicopter's tail rotor continued turning until the chopper hit water and that the aircraft's hydraulic systems were in order.
The Sikorsky S-76 C+ helicopter operated by Finland's Copterline company plunged into the Baltic Sea on August 10 shortly after taking off from Tallinn for Helsinki, claiming the lives of all the 12 passengers and two pilots on board.
The investigating commission was supposed to publish its interim report today but did not do so because of a petition against it lodged by the families of Estonian victims of the crash.
The commission is to complete its final report within a year of the accident, or by Aug. 10, 2006 at the latest
NTSB, Estonian authorities, Turbomeca, etc.) are still unable to find any
"smoking gun" associated with the accident. So far, no technical problem
has been found. The MGB has been examined and nothing abnormal was found their, either.
The U. S. NTSB is giving this accident a high priority and is ready to utilize their full range of resources to try and determine the primary cause of the accident.
Press release__________
Sent: Tue Sep 13 01:08:21 2005
Subject: Estonian investigation commission rules out engine failure as cause of August helicopter crash
Estonian investigation commission rules out engine failure as cause of
August helicopter crash
18:59, 12. september 2005
TALLINN, Sep 12, BNS - A commission set up in Estonia to investigate the crash near Tallinn last month of a helicopter of the Finnish Copterline company has ruled out breaking off of the rotor blade and engine failure as the causes of the accident but has so far failed to establish why the chopper crashed.
"We've a fairly true picture of how everything happened but unfortunately we're unable to say why it happened," the chairman of the Economy and Communications Ministry commission probing into the helicopter accident, Taivo Kivistik, told reporters today.
His deputy, Tonu Ader, said the commission has as a result of the investigation ruled out several earlier theories about possible causes of the accident. He declined to say which versions the investigators consider the more likely so as to avoid speculation.
The probe did not establish the breaking off of some parts while the helicopter was in air, Ader said. The parts separated from the chopper were lying near the wreck on the bottom of the sea and the only part lying farther away from the wreck was a blade of the main rotor.
"The commission has serious grounds to eliminate the breaking off of the main rotor blade as a cause of the crash," Ader said.
According to Ader, the commission reached the conclusion that the blade found at a distance from the wreck did not break off until the helicopter hit water. He made it clear that all four blades had broken off and had sustained relatively similar damage.
The commission also ruled out the possibility of the engines failing during flight. Ader said the engines continued working till almost the moment the helicopter struck water.
The helicopter started behaving inexplicably around 37 seconds before plunging into sea, Ader said. In his words, first its nose lifted up while the helicopter itself started to turn to its left side and away from its original course.
Then the chopper turned back right and started falling, making 13 full turns to the right, or one turn in 2.5 seconds on the average, until it hit water.
"The high speed of turning may indicate an overload which prevented the crew from getting control of the helicopter," Ader said.
According to him, the tape of the discussion between the pilot and the co-pilot showed that right before the zero-moment when things started to go wrong the pilot said, "Let's boost power," which was followed by an expression of surprise and, a few seconds later, by a very quiet Mayday
call repeated three times.
A bit later the co-pilot's question, "Have we lost the tail?" could be heard following which the recording contained no distinguishable phrases, he said.
According to Ader, clear evidence exists that the helicopter's tail rotor continued turning until the chopper hit water and that the aircraft's hydraulic systems were in order.
The Sikorsky S-76 C+ helicopter operated by Finland's Copterline company plunged into the Baltic Sea on August 10 shortly after taking off from Tallinn for Helsinki, claiming the lives of all the 12 passengers and two pilots on board.
The investigating commission was supposed to publish its interim report today but did not do so because of a petition against it lodged by the families of Estonian victims of the crash.
The commission is to complete its final report within a year of the accident, or by Aug. 10, 2006 at the latest
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rumor
Been hearing some rumors (this is a rumours networks so ....) that the rate the machine was spinning was to great to be caused be any kind of tailrotor failure.
The talk is that the machine encountered some sort of weather fenomena like a tornade or a whirlwind and that it cause the machine to get out of hand. Can anyone confirm if this is correct? Turning 360 degrees in 2.5 seconds, is that to fast to be caused by loosing tailrotoreffect?
Anyone know if a tornado or whirlwind can suddenly appear and then disappear without the met-people knowing of it (seeing it on weather-radar and so on) ?
Best regards
RotorSwede
The talk is that the machine encountered some sort of weather fenomena like a tornade or a whirlwind and that it cause the machine to get out of hand. Can anyone confirm if this is correct? Turning 360 degrees in 2.5 seconds, is that to fast to be caused by loosing tailrotoreffect?
Anyone know if a tornado or whirlwind can suddenly appear and then disappear without the met-people knowing of it (seeing it on weather-radar and so on) ?
Best regards
RotorSwede
Technical fault discovered in crashed Copterline helicopter
A technical fault has been found from the control system of the Copterline helicopter which crashed near Tallinn in August with the loss of all its passengers and crew, and its impact on the possible cause of accident is to be further investigated, commercial operator Copterline reported yesterday.
During investigations carried out in Washington, a technical fault was discovered in the front servo of the Sikorsky 76C-helicopter, which is thought to have been a possible cause for a temporary seizing up of the control system.
The front servo is one of the three power steering systems of the control apparatus, which transmits the steering commands of the pilot. The manufacturer of these parts is responsible for their complete overhaul on a regular basis.
"It was discovered in Washington that the front servo did not pass the operational check. It is still unclear what caused the freezing of the front servo. It is also uncertain whether the accident was caused by the front servo malfunction", the Finnish representative of the Estonian-led commission of inquiry, nimi>Hannu Melaranta, announced on Thursday.
Fourteen people died in August, including 12 passengers, when a Finnish Copterline helicopter on a scheduled flight between Tallinn and Helsinki crashed into the Gulf of Finland shortly after take-off from the Estonian capital.
Copterline is also to start lay-off talks because scheduled traffic between Helsinki and Tallinn is not profitable. According to the company, this is a direct result of the helicopter crash in August.
Only one of the company's 12 helicopters is flying the scheduled Helsinki-Tallinn route. However, more than half of the 70-strong personnel is working in scheduled traffic.
A technical fault has been found from the control system of the Copterline helicopter which crashed near Tallinn in August with the loss of all its passengers and crew, and its impact on the possible cause of accident is to be further investigated, commercial operator Copterline reported yesterday.
During investigations carried out in Washington, a technical fault was discovered in the front servo of the Sikorsky 76C-helicopter, which is thought to have been a possible cause for a temporary seizing up of the control system.
The front servo is one of the three power steering systems of the control apparatus, which transmits the steering commands of the pilot. The manufacturer of these parts is responsible for their complete overhaul on a regular basis.
"It was discovered in Washington that the front servo did not pass the operational check. It is still unclear what caused the freezing of the front servo. It is also uncertain whether the accident was caused by the front servo malfunction", the Finnish representative of the Estonian-led commission of inquiry, nimi>Hannu Melaranta, announced on Thursday.
Fourteen people died in August, including 12 passengers, when a Finnish Copterline helicopter on a scheduled flight between Tallinn and Helsinki crashed into the Gulf of Finland shortly after take-off from the Estonian capital.
Copterline is also to start lay-off talks because scheduled traffic between Helsinki and Tallinn is not profitable. According to the company, this is a direct result of the helicopter crash in August.
Only one of the company's 12 helicopters is flying the scheduled Helsinki-Tallinn route. However, more than half of the 70-strong personnel is working in scheduled traffic.
Not so long ago Copterline was planning to add a S-92 on the route!
Too bad if this crash will destroy travelers interest in traveling with helicopters between the two destinations.
I wonder if it is really safer to travel with ferry?
Too bad if this crash will destroy travelers interest in traveling with helicopters between the two destinations.
I wonder if it is really safer to travel with ferry?
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Is plasma spray part of the std actuator ? , I have always associated it with overhaul / repair before but as this was a fairly new machine one would not think the servos had been through an overhaul cycle.