R22 accident 27th March 2014 Borroloola, NT
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R22 accident 27th March 2014 Borroloola, NT
I can't find any previous reference to this Rotor drive v belt failure involving Robinson R22 helicopter, VH-HRX, 100 km SW of Borroloola, NT on 27 March 2014
A cautionary tale 
What happened
On 27 March 2014 the pilot of a Robinson R22 helicopter, registered VH-HRX, departed from Mullapunyah station, Northern Territory, for a short flight to the north-west. About 10 minutes after departure the pilot radioed that the drive v‑belts had failed and the station owner, in another R22, saw the helicopter enter a steep descent.
Soon after, the station owner found the helicopter complete and upright in a relatively clear area. The pilot of VH-HRX, who was laying a few metres from the helicopter, had sustained a serious head injury. The station owner tended the casualty and alerted emergency services at Borroloola of the accident, as well as personnel at the station homestead. Station personnel accessed the accident site over the rough terrain and started to transport the injured pilot on the back of a utility vehicle. The casualty was later transferred to a Bell 206 Jetranger helicopter for transfer to Macarthur River Mine. An aeromedical service then transported the injured pilot to Darwin where he was hospitalised for a number of weeks.
What the ATSB found
During the initial engine start/clutch engagement process following an extended period of static belt stretching, one or both rotor drive v-belts were displaced on the lower sheave with consequent increase in v-belt slack. Although the pilot, who was not qualified to conduct such maintenance, adjusted the clutch actuator to correct the excessive v‑belt slack, the v-belt displacement went undetected. While being operated in that abnormal configuration, one of the belts weakened and failed with consequent failure of the remaining belt, loss of drive to the rotors, and a forced landing.
Although Robinson Helicopter Company Safety Notice SN-33 provided guidance to pilots on how to stretch new v-belts statically, it did not specifically warn pilots that this process can increase the risk of belt displacement during the subsequent start.
Safety message
This accident highlights that in addition to having a good working knowledge of Robinson Helicopter Company Safety Notice SN-33, R22 pilots and engineers should be especially aware that, if the rotors do not turn within 5 seconds after clutch engagement, it is critical to perform the shutdown procedure and check the slack and position of the v-belts on both the lower and upper sheaves, before flight.
Pilots and operators of helicopters should also consider the residual risk of their operation and the benefit of occupants wearing helmets to reduce the risk of head injury in the event of an emergency landing.
On 27 March 2014 the pilot of a Robinson R22 helicopter, registered VH-HRX, departed from Mullapunyah station, Northern Territory, for a short flight to the north-west. About 10 minutes after departure the pilot radioed that the drive v‑belts had failed and the station owner, in another R22, saw the helicopter enter a steep descent.
Soon after, the station owner found the helicopter complete and upright in a relatively clear area. The pilot of VH-HRX, who was laying a few metres from the helicopter, had sustained a serious head injury. The station owner tended the casualty and alerted emergency services at Borroloola of the accident, as well as personnel at the station homestead. Station personnel accessed the accident site over the rough terrain and started to transport the injured pilot on the back of a utility vehicle. The casualty was later transferred to a Bell 206 Jetranger helicopter for transfer to Macarthur River Mine. An aeromedical service then transported the injured pilot to Darwin where he was hospitalised for a number of weeks.
What the ATSB found
During the initial engine start/clutch engagement process following an extended period of static belt stretching, one or both rotor drive v-belts were displaced on the lower sheave with consequent increase in v-belt slack. Although the pilot, who was not qualified to conduct such maintenance, adjusted the clutch actuator to correct the excessive v‑belt slack, the v-belt displacement went undetected. While being operated in that abnormal configuration, one of the belts weakened and failed with consequent failure of the remaining belt, loss of drive to the rotors, and a forced landing.
Although Robinson Helicopter Company Safety Notice SN-33 provided guidance to pilots on how to stretch new v-belts statically, it did not specifically warn pilots that this process can increase the risk of belt displacement during the subsequent start.
Safety message
This accident highlights that in addition to having a good working knowledge of Robinson Helicopter Company Safety Notice SN-33, R22 pilots and engineers should be especially aware that, if the rotors do not turn within 5 seconds after clutch engagement, it is critical to perform the shutdown procedure and check the slack and position of the v-belts on both the lower and upper sheaves, before flight.
Pilots and operators of helicopters should also consider the residual risk of their operation and the benefit of occupants wearing helmets to reduce the risk of head injury in the event of an emergency landing.
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I remember about 24 years ago after a run of belt failures on R22's, Robinson issued a statement saying that when new belts were fitted you had to fly in a safe environment for 18 hours.
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The pilot was indeed critically injured and many feared he would not pull through. Now as far as I am told he has sold most of his operation, which involved local tourist and air work (survey) in R44's and I think another R22 as I believe there is doubt he will be able to pass his medical.
We have certainly had some problems with these belts over the years, with many of us experiencing belt failures, indeed at least one fatality as noted in the crash comics.
Our latest thinking is that it is folly to do a static engagement for a period of time as that then conditions the belts, particularly these newer stiffer varieties to a form profile which induces a vibration upon first start up thus causing further depletary reactions. This theory is undergoing CASA discussions I believe.
This in layman's terms is likened to the airliner landing wheel which has been sitting in cool conditions overnight and the resultant conditioned flat spot causes a distinct vibration on first taxi and take off. We all would have experienced that.
We have certainly had some problems with these belts over the years, with many of us experiencing belt failures, indeed at least one fatality as noted in the crash comics.
Our latest thinking is that it is folly to do a static engagement for a period of time as that then conditions the belts, particularly these newer stiffer varieties to a form profile which induces a vibration upon first start up thus causing further depletary reactions. This theory is undergoing CASA discussions I believe.
This in layman's terms is likened to the airliner landing wheel which has been sitting in cool conditions overnight and the resultant conditioned flat spot causes a distinct vibration on first taxi and take off. We all would have experienced that.
topendtorque
A number of times I have stopped and left the belts engaged and shut down, then disengaged prior to the next start. This is done to stretch new belts that growl excessively. Is this what you are referring to?
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Yes, here is the final report in which it refers to the stretching in some detail, note the words "shape set"
http://www.atsb.gov.au/media/5179535...58%20Final.pdf
http://www.atsb.gov.au/media/5179535...58%20Final.pdf
tourque
Now its the Service Bulletin that will get us, Must say though I only ever had the belts stretch overnight and then tried again, but couldn't fault someone for doing it longer. The old saying that metal has memory applies to rubber also.
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The happy medium
Lames seem to set the belts so tight these days that the MRBs turn while cranking, makes life hard for the starter motor. I guess if it makes it less likely the belts will jump the groove then so be it. Would be nice if there was a happy medium though.
Robinson are now saying to count the clutch actuator time. Apparently a clutch motor popped a breaker midway through the engage cycle, the pilot didn't notice, attempted to take off with belts only half tensioned, crashed.
Robinson are now saying to count the clutch actuator time. Apparently a clutch motor popped a breaker midway through the engage cycle, the pilot didn't notice, attempted to take off with belts only half tensioned, crashed.
22Clip, quick reply as I'm getting ready to go on tour but basically, in my (limited) experience with new RHC belts, they are too small and even with the minimum stop adjustment wound right out, they still turn the blades when the engine is being cranked. There comes a point where the intermediate flex plate contacts the t/r pitch control bellcrank if the minimum stop is wound too far back.
In my opinion, the best fix is to fly the first 20 hours after a belt change as quickly as you can.
In my opinion, the best fix is to fly the first 20 hours after a belt change as quickly as you can.
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Yeah spot on, no fun having to start up with pedals not centralised so rear flex plate nuts miss the tail rotor push rod nut. We'd never accept this in motor cars would we?
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My belts have been too tight ever since its' rebuild 200 hours ago. The adjuster is on the end stop and I have tried all the shut downs with belts tight etc. Unless I pre stretch the belts prior to every cold start up, the starter always turns the rotors. This eventually broke the end off my starter motor housing presumably due to the load, so I always pre stretch the belts now. I just need to run the clutch for about 30 seconds and leave it for an hour prior to a cold start. I did query this with Robinsons and they told me it was OK to do this if it cured my problem.
Last edited by muffin; 19th Jan 2015 at 14:31.
