HeliNinja Posted February 19, 2016 Report Share Posted February 19, 2016 Article and video: http://www.npr.org/sections/thetwo-way/2016/02/18/467269135/watch-helicopter-crashes-into-the-ocean-in-hawaii 1 Quote Link to comment Share on other sites More sharing options...
takefootoff Posted February 19, 2016 Report Share Posted February 19, 2016 Man, that thing dropped fast. Quote Link to comment Share on other sites More sharing options...
A-aron Posted February 19, 2016 Report Share Posted February 19, 2016 Any ideas on what happened? Quote Link to comment Share on other sites More sharing options...
Nearly Retired Posted February 19, 2016 Report Share Posted February 19, 2016 I would say with confidence that the main drive shaft failed. The main rotor slows like someone pulled the brake handle while nose yaws *left* and the tail rotor speeds up. There's only one thing that can cause that set of conditions in a 206. However, main drive shaft failure is *VERY* unusual in a 206 anymore. There are "temp strips" on the couplings that must be checked on preflight for evidence of overheating. So if the MDS did fail, then there are some big questions that have to be answered. It *could* be something else, of course...and we'll find out sooner or later. 1 Quote Link to comment Share on other sites More sharing options...
TomPPL Posted February 19, 2016 Report Share Posted February 19, 2016 What would be the main cause of this type of failure? I'm guessing a bearing breakdown? I would say with confidence that the main drive shaft failed. The main rotor slows like someone pulled the brake handle while nose yaws *left* and the tail rotor speeds up. There's only one thing that can cause that set of conditions in a 206. However, main drive shaft failure is *VERY* unusual in a 206 anymore. There are "temp strips" on the couplings that must be checked on preflight for evidence of overheating. So if the MDS did fail, then there are some big questions that have to be answered. It *could* be something else, of course...and we'll find out sooner or later. Quote Link to comment Share on other sites More sharing options...
Nearly Retired Posted February 19, 2016 Report Share Posted February 19, 2016 The input drive shaft (IDS) from the engine gearbox to the transmission has two flexible couplings on either end to allow for transmission movement. The 206 transmission is mounted fairly "softly" compared to, say, an Astar or H-500; it can move around quite a bit. These couplings can and do fail, although thankfully not very often. On each coupling there are tell-tale temp strips which are designed to alert you if the coupling is overheating. The temp strips change color when this happens. They are a preflight item and no self-respecting 206 pilot gets in one without checking them. While IDS failures have occurred in the 206 series over the years, they are very, very rare now. Having said that, well, sh*t happens. If one of those couplings failed, then all drive to the transmission would be lost. The old couplings can be replaced by a new-style which is called "K-Flex" and made by Kaman Aerospace. These new couplings do away with the temp strip indicators. However not all 206's have been updated. 1 Quote Link to comment Share on other sites More sharing options...
TomPPL Posted February 19, 2016 Report Share Posted February 19, 2016 Thanks for the reply, interesting! Quote Link to comment Share on other sites More sharing options...
iChris Posted February 19, 2016 Report Share Posted February 19, 2016 (edited) I would say with confidence that the main drive shaft failed. The main rotor slows like someone pulled the brake handle while nose yaws *left* and the tail rotor speeds up. There's only one thing that can cause that set of conditions in a 206. Excellent first call. that’s a very hideous type failure (short shaft failures) and also very uncommon. It’s so uncommon most new folks have probably never heard of that type of failure. Even those who regularly fly the Bell jet Ranger or Eurocopter AS350. Seldom talked about during training or check rides. The left yaw in addition to the high-pitched whine are characteristic of that type failure. The pilot would be dealing with conflicting information, as it appears to be an engine failure; however, all indications are that the engine is still running, which is actually the case. If it were handled as a power settling issue this is what you would see. The left yaw caused by the addition of the up collective to arrest the descent and the engines response to that up collective, resulting in additional tail rotor thrust, since the engine is still online but unloaded from the main rotor. Main rotor torque and RPM decreasing. The whine cause by the engine over-speed as it is no longer driving the load of the main rotor transmission. It could be the dreaded downwind hovering turn. Four PAX on board, heavily loaded, turns downwind and starts to settle. However, during the whole video you never notice any right yaw, which would normally be the case if you pull down the rotor RPM due to some settling issue. The bell 206 and AS350 both use the alternate drive system. The tail rotor is not driven directly from the main rotor transmission. We’ll just have to wait and see. https://youtu.be/LrS1jhG9tf4 https://youtu.be/BeZN-7cKlrc Edited February 19, 2016 by iChris Quote Link to comment Share on other sites More sharing options...
iChris Posted February 19, 2016 Report Share Posted February 19, 2016 (edited) It could be the dreaded downwind hovering turn. Four PAX on board, heavily loaded, turns downwind and starts to settle. However, during the whole video you never notice any right yaw, which would normally be the case if you pull down the rotor RPM due to some settling issue. Sometime it's hard to tell. In the accident below there's little if any right yaw; however, it's more of a settling issue than any type of mechanical failure. This one lacks the left yaw characteristic of the Bell 206 crash. '>https://youtu.be/upaLFBsYymI Edited February 19, 2016 by iChris Quote Link to comment Share on other sites More sharing options...
r22butters Posted February 19, 2016 Report Share Posted February 19, 2016 I remember that video. Too heavy to go that slow was the issue, if I recall? That 206 seems to beginn to drop before it yaws. Wouldn't the driveshaft breaking (like our clutch belt failure) cause a sudden more "jerking" yaw before it starts to drop? Quote Link to comment Share on other sites More sharing options...
rockapotomus Posted February 19, 2016 Report Share Posted February 19, 2016 iChris, thank you for the detailed explanation on the 206. I'm a student pilot and studying these events and learning as much about them is very important to me. Not meaning to switch topics too much, but I'm curious about the r44 video. r22butters, you mention that the 44 is too heavily loaded for that airspeed. I'm having trouble telling, but did the pilot attempt to get out of that settling with power situation by applying forward cyclic and then up collective per the specified emergency procedure? If he did, was there simply not enough time AGL altitude to actually recover i.e. gain enough forward airspeed to climb out? As well, if he did, I assume that that recovery maneuver would be negatively affected by too much weight, right? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
iChris Posted February 19, 2016 Report Share Posted February 19, 2016 (edited) I remember that video. Too heavy to go that slow was the issue, if I recall? That 206 seems to beginn to drop before it yaws. Wouldn't the driveshaft breaking (like our clutch belt failure) cause a sudden more "jerking" yaw before it starts to drop? The R22 and 300 are more conventional drive systems, were the tail rotor is driven directly from the main rotor transmission. You dont have to worry about such a hideous type failure. Your correct, thats why its sometime hard to tell. In fact, it may never be resolved, since the fact that the short shaft is found sheared, could be determined to be the effect of the sudden stoppage due to the rotors contacting the water. This could likely go down as an engine failure, settling issue, or pilot error. Without the video and from the pilots perspective and everyone elses perspective, it would appear to be one of those three causes, since short shaft failures are so uncommon. The question of why the pilot was hovering so low over water should also be investigated. Edited February 20, 2016 by iChris Quote Link to comment Share on other sites More sharing options...
ShelbyFlyer Posted February 19, 2016 Report Share Posted February 19, 2016 Acknowledging that looking at a video with frame rates can give illusions; anybody else notice that the tail rotor seems to windmill and then stop before the impact. I do believe the sound of fast engine acceleration indicates a drive train failure. I don't think I'd put all the money on the main drive shaft. I would consider something closer to the free-wheeling unit or N2 gear train. Looking at Google earth, it appears the area of impact is right next to the Pearl Harbor Visitor center. I don't see any helipads in the visitor center. The aircraft's low altitude and landing attitude before the failure, could suggest that the pilot was set up for an emergency landing. An impending failure in the drive train may have given the pilot a chip light. A main drive shaft failure would not have a caution warning panel indication. There may have been unusual vibration also. Fortunately, the pilot survived and we should have a full report in about a year. Fly safe Quote Link to comment Share on other sites More sharing options...
iChris Posted February 20, 2016 Report Share Posted February 20, 2016 (edited) Acknowledging that looking at a video with frame rates can give illusions; anybody else notice that the tail rotor seems to windmill and then stop before the impact. I do believe the sound of fast engine acceleration indicates a drive train failure. I don't think I'd put all the money on the main drive shaft. I would consider something closer to the free-wheeling unit or N2 gear train. Your correct, frame rate does cause thatll illusion. In the example below, you can see how the frame rate actually makes the wheels seem to stops and change direction. So it is with the tail rotor. It actually looks like it stops and reverses direction. Also, the main drive shaft is closer to the free-wheeling unit than most anything else. Link - Kathryn's Report The main rotor drive system provides a means of transmitting power from the engine to the main rotors. The main rotor drive system consists of a transmission, main rotor mast, main driveshaft, freewheel assembly, and oil cooler. The freewheel assembly is mounted on the engine accessory gear case. It connects the engine to the transmission through the main driveshaft on the forward side, and the tail rotor gearbox through related shafting on the aft side. This provides simultaneous rotation of main and tail rotors and permits free rotation of both rotors when the engine is not operating. - BHT-206A/B-SERIES-MM-6; 63-1. MAIN ROTOR DRIVE SYSTEM Frame rate does cause illusions. In the third example below, you can see how the frame rate actually makes the wheels on the top car seem to stop and change direction. Illusions Cased by Video Frame Rate Illusions Cased by Video Frame Rate https://youtu.be/dFhDUJqg6nE Doors off made for an easy exit from the helicopter... Edited February 28, 2016 by iChris Quote Link to comment Share on other sites More sharing options...
Nearly Retired Posted February 21, 2016 Report Share Posted February 21, 2016 In the news report today showing the helicopter being lifted from the water, the main rotor blades look absolutely undamaged - hardly even bent. To me, this indicates that they were definitely not under power when they hit (nor were they turning very fast). That being the case, if the input drive shaft is damaged/sheared, it did not happen because the main rotor blades hit something and sent a shock back through the system. I think this pilot knew he had a problem and was making an emergency/precautionary landing there at the Pearl Harbor site. He *almost* made it, too. 1 Quote Link to comment Share on other sites More sharing options...
mudkow60 Posted February 21, 2016 Report Share Posted February 21, 2016 Or... a pax pushed the collective full down at a critical time. Quote Link to comment Share on other sites More sharing options...
TomPPL Posted February 21, 2016 Report Share Posted February 21, 2016 This is what I'm thinking: I think this pilot knew he had a problem and was making an emergency/precautionary landing there at the Pearl Harbor site. He *almost* made it, too. Looks to me - in my limited knowledge - that he was setting up for a landing. 1 Quote Link to comment Share on other sites More sharing options...
iChris Posted February 21, 2016 Report Share Posted February 21, 2016 (edited) I think this pilot knew he had a problem and was making an emergency/precautionary landing there at the Pearl Harbor site. He *almost* made it, too. This is what I'm thinking: Looks to me - in my limited knowledge - that he was setting up for a landing. That’s consistent with the witness’s observation below. The helicopter was coming in low over the water directly toward him. Something happen that required the pilot to deviate from the required altitude that he would normally fly, to comply with the regulations, that allowed him to operate without floats on a tour flight. We now know that from the tower recordings, that he was experiencing some problems. The Hawaii Army National Guard identified the pilot as Ryan Rohner, a UH-60 Black Hawk pilot and warrant officer. He has been with the guard since 1998. Pilot: Tower, Chopper 8, I think I’m going down. Tower: Chopper 8, roger. Okay chopper, you said (inaudible) of Ford Island, right? Pilot: (Inaudible) Tower: Okay Air 1, if you can check next to the Arizona Memorial, please. Air 1: Arizona Memorial, on my way, ma’am. Tower: Air 1, we have a report that he’s underwater. The rules would normally require him to operate at an altitude that would ensure the helicopter was within power off glide distance of the shore and also require, in some cases, that passengers wear flotation gear. The flotation gear requirement is somewhat weak because belt pack flotation gear meets the requirements, which means you’re not actually fully wearing the gear See Link. Additional effort is required once in the water to fully employ. It’s very hard to stay within the requirements when you’re operating in an area with that much water everywhere that you fly. Most operators use float equipped helicopters, which allowed for a lot more flexibility in their operation. Whether he’s operating under CFR §135, §136.31, or §91.147 there is some flexibility in the regulations that would allow him to operate without floats, see below: Note, some apply to National Parks, and Hawaii. §91.205 [12]§135.183[a] §136.11 [c]§136 Appendix A [3] Provisions under a Letter of Authorization https://youtu.be/BeZN-7cKlrc Edited February 22, 2016 by iChris 1 Quote Link to comment Share on other sites More sharing options...
HawaiiCFII Posted February 22, 2016 Report Share Posted February 22, 2016 In reference to the chance it could be a settling issue and I don't see this mentioned yet. It appears to me that he had a nearly direct headwind based on the way the steam moves after splashdown. On the other video with the selfie, the fronds on the palm tree appear to show the prevailing wind direction to be close to the wind in the first video and you can hear it in the microphone. 1 Quote Link to comment Share on other sites More sharing options...
adam32 Posted February 24, 2016 Report Share Posted February 24, 2016 Pre-lim is out... http://www.verticalmag.com/news/article/NTSB-issues-preliminary-report-for-Hawaii-helicopter-crash?utm_source=vertical-daily-news&utm_medium=email&utm_campaign=vertical-daily-news-02-24-16 1 Quote Link to comment Share on other sites More sharing options...
SBuzzkill Posted February 25, 2016 Report Share Posted February 25, 2016 “The pilot reported to the [NTSB] investigator-in-charge, that while in cruise flight over Ford Island, he felt a vibration followed by a grinding noise. Shortly after, the pilot heard a loud bang, scanned the instrument panel and saw that the engine instruments indicated the engine was still running, however, rotor r.p.m. decreasing. “The pilot initiated an autorotation to a grassy area near Contemplation Circle at the World War II Valor in the Pacific National Monument. As the pilot neared his intended landing area, he observed multiple people within the area. The pilot stated he initiated a left pedal turn, attempting to land close to the shoreline. Subsequently, the helicopter descended rapidly into the water, about 20 feet from the shoreline. His account and the video do not match. Quote Link to comment Share on other sites More sharing options...
iChris Posted February 25, 2016 Report Share Posted February 25, 2016 (edited) “The pilot reported to the [NTSB] investigator-in-charge, that while in cruise flight over Ford Island, he felt a vibration followed by a grinding noise. Shortly after, the pilot heard a loud bang, scanned the instrument panel and saw that the engine instruments indicated the engine was still running, however, rotor r.p.m. decreasing. “The pilot initiated an autorotation to a grassy area near Contemplation Circle at the World War II Valor in the Pacific National Monument. As the pilot neared his intended landing area, he observed multiple people within the area. The pilot stated he initiated a left pedal turn, attempting to land close to the shoreline. Subsequently, the helicopter descended rapidly into the water, about 20 feet from the shoreline. His account and the video do not match. No, the pilot’s account and the video are consistent; moreover, the pilot’s account and the video are amazingly consistent with the type of failure first set forward by Nearly Retired’s post #4 and #6. “He felt a vibration followed by a grinding noise. Shortly after, the pilot heard a loud bang, scanned the instrument panel and saw that the engine instruments indicated the engine was still running, however, rotor r.p.m. decreasing.” Look at some of the similarities in the following reports: NTSB Identification: IAD05LA084 NTSB Identification: LAX06LA161 NTSB Identification: DEN91FA068 NTSB Identification: LAX89LA253 NTSB Identification: FTW86FA085 NTSB Identification: FTW82FRJ17 NTSB Identification: NYC79FA056 Edited February 25, 2016 by iChris 1 Quote Link to comment Share on other sites More sharing options...
r22butters Posted February 25, 2016 Report Share Posted February 25, 2016 So when the video begins he's already in an auto? Quote Link to comment Share on other sites More sharing options...
iChris Posted February 25, 2016 Report Share Posted February 25, 2016 So when the video begins he's already in an auto? The Initial problem occurred at altitude, which necessitated the auto. Quote Link to comment Share on other sites More sharing options...
iChris Posted February 25, 2016 Report Share Posted February 25, 2016 (edited) iChris, thank you for the detailed explanation on the 206. I'm a student pilot and studying these events and learning as much about them is very important to me. Not meaning to switch topics too much, but I'm curious about the r44 video. r22butters, you mention that the 44 is too heavily loaded for that airspeed. I'm having trouble telling, but did the pilot attempt to get out of that settling with power situation by applying forward cyclic and then up collective per the specified emergency procedure? If he did, was there simply not enough time AGL altitude to actually recover i.e. gain enough forward airspeed to climb out? As well, if he did, I assume that that recovery maneuver would be negatively affected by too much weight, right? Thanks in advance. That R44 accident is a good example of settling with power, where the power available doesn't meet the power required. Most often the result of the pilot not understanding the characteristics of airspeed vs. power on the backside of the power curve. You're basically correct, not enough altitude nor time to recover NTSB Identification: CEN11CA325 https://youtu.be/y4sxEOdPYDQ'>https://youtu.be/y4sxEOdPYDQ https://youtu.be/yz_vEsRHeWs'>https://youtu.be/yz_vEsRHeWs Edited February 25, 2016 by iChris 2 Quote Link to comment Share on other sites More sharing options...
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