Collective collar slipped - Printable Version +- Rotorway Forums (https://rotorwayforums.com) +-- Forum: Rotorway General (https://rotorwayforums.com/forum-1.html) +--- Forum: Mechanical Failures and Accidents (https://rotorwayforums.com/forum-6.html) +--- Thread: Collective collar slipped (/thread-181.html)

Collective collar slipped - Orv Neisingh - 08-13-2026 Here is an area where I experienced a control lockup in flight was with the donut-shaped collar around the main rotor shaft under the non-rotating swash plate on the Rotorway helicopter. This collar must be secured to the main shaft by clamping pressure so that it cannot slide up or down. In this case I was with a student when the collective controls locked in the near full-up position. This happened in an area where the wind was high and gusting higher as my student was making an approach to the fuel tanks on his ranch. Controlling the helicopter, a Jet Exec non-factory configuration, in the gusty winds was requiring a lot of collective input when all at once the collective locked in the near-full up position. It is important to note that the jet engine equipped ships vary greatly from the design of the Rotorway helicopter and their reliability history should not be compared with that of a Rotorway built to factory specs. The helicopter began to climb, and climb fast, with the powerful turbine engine powering it's rotor system. I emphatically called out to my student "I've got it", those special words that I reserve for the times when I need the student completely off of the helicopter's controls. I took the controls and tried to force the collective down but it would not move down at all. I then slightly decreased the throttle on the Jet Exec to achieve a main rotor RPM of around 92 percent but the helicopter continued to climb. I knew that eventually we would run out of power and stall the main rotor blades ending in our demise. I then remembered that rapid erratic cyclic inputs would severely dump lift so I began to move the cyclic control from stop to stop in all directions causing the helicopter to loose lift and settle to the ground where I was able to slide it on (it had the extended skid modification which one again prevented the helicopter from nosing over with forward ground contact). A word of caution here, we were in a life and death situation and the only way that I could stop the rapid climb was to reduce the main rotor RPM to decrease the lift being produced along with very aggressive cyclic inputs. Doing this in flight and especially in a high rotor pitch angle climb is very risky and if the rotor RPM is allowed to decrease much below that point the main rotors will stall and the helicopter will fall like a rock. I had no choice and did what I needed to do to cause the helicopter to descend and slide onto the surface. Upon investigating the cause of the lock-up we discovered the problem. My student had purchased a rolled over helicopter in Texas. He completely rebuilt it before I arrived. The torque on the nut securing the collar to the main rotor shaft had been checked by me when I arrived a the students home. The torque value on the NUT was correct but the collar still slipped down allowing the alignment forks to exit the top of the collar and rotate away from their slots in the collar. The forks now effectively blocked the collective control from moving the swashplate downward to lower the pitch on the main rotor blades. Upon examination after the lockup we found that the clamping bolt had corroded threads. The bolt thread condition caused the nylock nut to achieve the proper torque, but before the nut was far enough onto the bolt to securely clamp the collar to the shaft. The person installing the collar must have used a defective bolt to secure it. I now gently but firmly pry down on the collar on every ship I apply downward pressure on the collar to insure that it has the proper clamping pressure so that it will not move. I also check the torque on both the nut and the bolt head to insure that both are at the proper setting to achieve the required clamping force on the collar. The photo below was taken after we landed. You can clearly see the forks sitting out of their slots and resting on top of the collar which prevents them from being able to be lowered.  =100%=100%After we re-positioned and secured the collar above and completed Ron's flight instruction, I headed to Pennsylvania to provide another student with advanced flight training. I was performing an airworthiness inspection on this student's Rotorway Exec 90 when I noticed the collar position looked too low. When I pulled full up-collective the fork came completely out of the collar. We checked the torque settings and they were incorrect for the nut and bolt head, they were loose. This student had been flying it that way at altitude and if he had ever been put into the position of applying full up-collective the fork would have come out of the guide slots and rotated away from them. This would again have jammed the collective in the full-pitch position. Had that happened it could have ended up in an unhappy ending! Everyone should check the position and security of this collar. That was the second collar issue found in 2 weeks. The photo below was taken before we slid this second collar back into position and properly torquing the clamping bolt.  =100%=100%This method of securing the collar to the main shaft is very effective but the installation must be done to the factory standards. It is the responsibility of the owner/builder to check the integrity of the clampinb bolt to insure proper securring of the collar to prevent it from moving. The photo above shows a properly placed collar and this builder also fabricated a reinforced collective scissor bracket. I have seen this bracket break in the past. The break occured at the 90 degree bend and is most likely from improper technique used in bending the bracket ears performed by the builder. Those bends should be radiused as per the factory drawings.  The following week I was off to Connecticut and of course now the first thing on this students ship that I checked was his locking collar. When I applied downward pressure on the collar with a piece of wood and a fulcrum the collar slipped down easily. We checked the torque on the nut and it turned and turned and turned but would not tighten. It took us nearly an hour to get the locknut with stripped threads off the bolt and as you can clearly see in the photo below the installer had used a bolt that was the next size longer than called for in the factory specs. When the nut was tightened it ran out of threads and rode up onto the shank of the bolt stripping the nut's threads. With the threads stripped the collar could not apply the required clamping force onto the main rotor shaft. It could have eventually slid down to the point that the forks could clear the collar, rotate, and jam the collective in the full up-collective position.  I urge everyone to check their collars prior to flight. This series of loose collars is not common because I have only found one loose clamping ring since. RE: Collective collar slipped - Geno Mancini - 08-13-2026 Very informative Orv. I have added the construction jpg for adjusting that clamp. It is 1/4 x 2-1/8 bolt with 1 washer under the head and 1 washer under the nut. Torque to 72 inlb.