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Old 22nd Aug 2020, 15:03
  #26 (permalink)  
blackdog7
 
Join Date: Jan 2011
Location: Lower Troposphere
Posts: 55
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Originally Posted by ring gear
For JD: Yeah, we were victim to the "pre-tracked" s70 blades when we first got them. This was when SA where whirl towering them late 80's early 90's. This would have been when you were there for sure, probably when you were CP there, my best guess. I think I have a couple of SA certificates with your signature on it back around those times. I believe it was SA who prevented us from actually adjusting the tabs originally at unit level. It actually tied our hands behind our back when it came to RTB. We had to turn off the "Tab" option on the CH8500, as SA would not allow us to bend them. Finally, after bashing our heads agains brick walls and being forced to accept decidedly "average" balance solutions, we gained approval to adjust Tabs. This made a vast improvement in ride quality and speed-to-solution of RTB because we could finally use ALL the adjustment mechanisms available.

As the article about whirl towers on the web site tries to show, even if a blade is "pre-tracked", it cannot correct a blade track for changes produced through increasing IAS....exactly when tab bending should be used and utilised - unless SA utilised a humungas wind machine to simulate a 80/120kts airflow...which I doubt strongly they did. A whirl tower can only confirm a blade in-track condition in a on-ground flat pitch flight idle condition and in a hover condition i.e. with pitch/collective applied to hover power equivalent condition. And then, the change in blade track during these 2 x different "power"/angle of attack conditions, the adjustment should be made using the DYNAMIC chord adjustment weights ...not the tabs.

So the original usefulness of the "pre-track" that SA were recommending back then is dubious and strongly debatable. But many things change over time as we begin to learn more and more about all sorts of things.

The creation of rogue rotor blades as described on the web site is what happens in real life. The helicopter community has lived with the phenomena since day one...but not many have understood the process. It has cost, and continues to cost the helicopter operators/industry a lot of wasted time and money.....needlessly. The new tooling does prevent the rogue rotor blade from occurring. It is game changing, as witnessed by many Defence forces who use it....just need to get those damn OEMs to agree and embrace the new paradigm and allow civil operators to use the same tooling that many militaries are so successfully using world wide.

I would love to have a discussion with you about your time there in SA and discuss some of the items on the web site with you....maybe we can make contact privately and open up a private chat via skype/messenger or some means to discuss these many issues. It would be great to discuss and get your thoughts on various item from the perspective of your extensive experience.

For BlackHawk9: Good old "StarWars Alley" , we didn't have a rock anchor with us at the time. It had already been deployed in the dinghy we had deployed to Pine Mountain creek (through-load in UH-1), so we had to make do.

For Blackdog7: Your so anal! ...and so indicative of the "new" age of aviation.

And just for you ring gear....obviously an old codger. Welcome to the new age.
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