I prefer the string method on 206s and a scope on 205/212s. Made special mirrors for this and in my opinion is the way to go. And agree also that explanation does account for a greater part of the sequence of events.

I have never flown with Van Horn main blades, however, I did have a balance weight come loose and slide to the tip cap in an OEM blade on a Jet Ranger once---it did not push off the tip cap, and stayed there. Luckily, I was in the traffic pattern and effected an immediate landing, it was NOT a comfortable ride however.

The timing of this recent bulletin is very interesting
https://documentation.vanhornaviatio...OTQ2OC4wLjAuMA..

I've been wrenching on 206 series for over 30 years and we have used nothing but the string and mirror method for probably 20 yrs for blade alignment on the ground before M/R hub and blade install. Now we use the alignment pins that go into the blade bolt bores, much easier on the eyes than the mirror method, but both work just fine. Most of the time if you spend the time getting the alignment perfect on the ground you will rarely have to do sweep adjustments during track and balance, Sometime with the RADS asking for a quarter point of sweep which is very very hard to do. Now if you're trunnion was not centered correctly during m/r hub build up, well you're just going to be chasing your tail.

Lets just say I know the person who developed those alignment pins which did provide a marked improvement to the process especially when in a remote location. But if you want to win some beer money, align the blades one string width aft of the bevel edge (lag) and you’ll never need to sweep a blade again. Guaranteed.

In the OEM 206 MRB the balance weights are actually installed up against the tip cap. What you felt could have been the 206 "tell tale" weight, which is an approx 1" cube of lead that us bonded to the IML of the spar on one face at the same time as the 21 pound main inertia lead sheet. Its designed to indicate a bondline degradation ahead of the failure of the larger main lead sheet if it detaches and impacts the tip cap.

https://cimg1.ibsrv.net/gimg/pprune....77785e0635.jpg

Yes, you are correct, ....just a pilot, I tried to explain as best I could remember, I did not realize there was a difference. I remember the mechanics had to get the books out and try show me---this was way back in 2004 and my memory is fading on the whole thing.

Van Horn's information letter regarding "collective bounce" suggest sweeping both blades aft up to "two points" which would then misalign the initial straight alignment.

Per Van Horn's letter: (5) Sweeping both blades up to 2 points aft has been shown to further decrease the severity of the vertical vibration and increase the airspeed at which onset occurs.

And per Van Horn's guidance for 206L MR track and balance they state excessive sweep gives you the tailboom wag. Now you might see why VHBs are not that popular with some.

https://cimg9.ibsrv.net/gimg/pprune....1d1ec60c45.jpg

dragon6172: When I play the Forbes Breaking News clip posted by Gordy in #251, I see different things when using different screens and different playback speeds. For slow playback speeds, like x0.25, you will probably see the entire body of the helicopter sometimes comes and goes or jumps. What might seem like a puff of smoke that is left behind by the helicopter (I certainly see that at some speeds and on some screens) might just be the previous position of the fuselage fading out in a following frame and might relate to a video compression processes? NTSB should have the benefit of gaining access to the original recordings.

That's a good observation. I think the format and algo used by IP cams probably does some of its own compression wizardry, too. The NTSB will figure it out.

Just a thought.
The 206 wouldn't have been equipped with an FDR, but would data from the mobile phones on board be useful?
Logging of yaw/pitch/roll and maybe GPS...?

Although smartphones are equipped with all these sensor, as far as I know they don't log the data from them. And even if they did, unlocking them to get at the data could prove challenging.

Many thanks. Yes, arrows are turned against each other on this aircraft. I wasn`t aware of that option.

First one has to find them.

This might be a fruitful line of investigation. From various serious crime trials, it's known that the accelerometer can yield useful information. They're recreated people's steps, that kind of thing. So acceleration forces should be readily available. Assuming, as you say, they can get into them. This is normally the purview of the other gov agencies...

Who have limited success sometimes, I think. I recall a mass killing terror attack in California (?) where the FBI could not unlock the iPhones and Apple refused to assist.

As a pure SLF, and maybe slightly off topic:
I watched the above NTSB video and I was wondering what the qualifications are of the people inspecting - in this case - a helicopter?

Would they be metallurgists, Helicopter pilots, Physics education, Helicopter/Plane mechanics...?
Would the NTSB send a call out to very experienced 206 pilots/mechanics?
Would they call out the actual manufacturers to examine the craft?

From reading this post there seems to be some very experienced and knowledgeable people replying here and wonder if from these forum based analysis's, are the NTSB people as good or better..?

There is a set NTSB procedure for the who, what, where, how the investigation is performed. In general, the NTSB people you see initially around the aircraft are NTSB investigators, airframe/engine OEM representative investigators, and usually several FAA investigators.

Once the aircraft is moved to a “secure location” then the NTSB may rely on various other people with more specific experience to continue the on-site investigation. However, the NTSB has strict limits on who is able to participate at that point so that may only include operator personnel to assist with disassembly, specialize component personnel if needed, etc.

If any part(s) require a more scientific review, those items will be shipped to the appropriate labs, metallurgists, etc. All in all, the investigation will cover an A-Z list of possibilities and topics and given this was a high profile accident will bring in even more resources to help determine the possible cause(s).