Dynamic Rollover

[cburg]

....

 

[cburg]

How's this for close:

 

https://www.youtube.com/watch?v=n6P51PWvTQo

Alternative (motorcycle) recovery technique ;-)

[Francis Meyrick]

Classification of dynamic roll-over events, anybody?

 

DR events are a fact of helicopter life. In training, we talk about it a lot. Unfortunately, it’s hard to demonstrate. (repeatedly…)

I hate to see the rush to Judgment. “What a dumb-ass”. “Shouldn’t have a helicopter License”. “That would never happen to me” Etc, etc.

The guys in those accidents are probably feeling bad enough, without being immortalized on You-Boob, and held up as examples of the proliferation of Dinosovarian genetic material in Aviation.

How about a bit of humanity here. It’s really not that hard to do. (In both senses). At some stage of our formative years, we too were at a limited experience level perhaps, where we were exposed to a steep learning curve. Now, what helps that process along? Ridicule? Mockery? I doubt it.

So, more gently perhaps, let’s see if we can dig a little further, and classify these type of events.

Building on cburg’s post:

(3 conditions required)

1.) Pivot Point - Roll Over on Level Ground (Takeoff)
2.) Rolling motion - Rolling Downslope (Takeoff or Landing)
3.) Exceeding the critical angle

(and maybe,as a 4th, mention the usual ingredient of "vertical thrust"/up collective/panic-pull...)

I wonder (I ask the question) if it would be helpful to point out three categories.

1) “Static” DR. Typically, we think of ONE skid up against a rock, or a skid stuck on ice, or embedded in tarmac. Often the skid on the other side, away from the pilot’s view. That’s the one every student immediately relates to, because you (as the CFI) can draw it so easily on the whiteboard. It’s intuitive. Easy enough to understand. I propose the stress on saying “please do not think this can only happen to low time pilots… it can (and does) happen to high-timers in a rush.”

2) “drifting hover DR”. Typically, something the student might not immediately associate with the risk of DR. Coming up to a low hover, and “drifting” (waffling about) in an unskilled (or careless) manner, and “drifting” sideways (or backwards and sideways) into a pivot point (fulcrum).

3) “low speed take-off DR”. Typically, (see the 407 video), our hero fails to understand (or respect) the aerodynamic process of achieving ETL. Not expecting that sink. Especially when you are heavy.

I hesitate to introduce a fourth category (speed above “low speed”), because at that stage, although the elements of DR arguably are present, we tend to think of that not so much as DR, but as “crashing”.

If you incorporated these classifications into your briefing, especially if you coupled it to some of these You-Boob disasters, I think it might help? I’m asking the question, not stating some magnificent wisdom. Lest I be angrily stomped on by the Great, Exalted Ones.

 

Above all, I propose:

1) this teaching should be delivered in a respectful manner, with emphasis on how EASY this DR fiasco can be achieved. Even by accomplished pilots, distracted, tired, in a rush, or otherwise not giving a seemingly simple helicopter task the full attention it deserves.

2) There should be a conscious absence of mockery or ridicule in the briefing. As is clearly evident in some of the above comments. That’s unhelpful, and sends entirely the wrong message. It says basically that “Only idiots” do that. So, by implication, once you’re “good”, then you really don’t have to worry about DR anymore, because you are way, way above all that stuff…

 

Just my 1 and one half cents’ worth. Feel free to jump on me now.

(Quack-quack)

 

“Flying helicopters is a privilege, not a right…”

Edited April 22, 2014 by Francis Meyrick

[Spike]

Absent of subjective material, personal opinions or misinterpreted information. DR by the book….

 

 

http://www.faa.gov/documentLibrary/media/Advisory_Circular/ac90-87.pdf

[aeroscout]

If you are real ginger with the controls, especially the collective, and you don't exceed the critical angle, a reduction of collective will prevent DR on the pickup. On the setdown, until the landing gear is solidly grounded you are bracketed with potential rollover in either direction depending on your roll rate.

The problem with dynamic rollover is that the critical angle is variable based on roll rate in the direction of the rollover.

All other factors being equal the highest critical angle is when the cg moves laterally slightly past the pivot point with no roll momentum. All the rest are smaller from there as the roll rate increases.

When setting down you have to be super controlled until both skids (or wheels) are solidly on the ground.

When picking up, you have to be supremely controlled until both skids (or wheels) are stabilized in the air.

[helonorth]

You gotta be super and supremely controlled. Roger.

[aeroscout]

You gotta be super and supremely controlled. Roger.

How about ultra refined control touch ?

Can you give lessons on the proper use of roger, Roger ?

[cburg]

MMMM - Master Manipulator of Mechanical Machinery

[aeroscout]

MMMM - Master Manipulator of Mechanical Machinery

Nice !

[Francis Meyrick]

A different take on DR. Easier-to-do-than-you might-think++++++

 

Here is a link to some other drawings on this same subject.

 

Edited April 22, 2014 by Francis Meyrick

[aeroscout]

Wow Moggy !

[Francis Meyrick]

(The helicopter in the sketch is meant to be flying away from you)

 

I honestly think that scenario has killed a BUNCH of Tuna Pilots over the years. A lot of the inexplicable disappearances. In essence though, it's just another manifestation of simple DR.

The references for anybody interested are from "Moggy's Tunaboat Manual."

 

And my own personal brush with terminal disaster, with the ship way,way out of sight over the horizon, is described here: A Blip on the Radar (8) "Eyes of Dead Man"

Edited April 19, 2014 by Francis Meyrick

[aeroscout]

That has the potential to hit close to home. I guess it all does at one level or another.

[adam32]

Nice little sketch...but its not Dynamic Rollover...that is a crash.

 

Kinda like that dumbass in the 206 that tried to pull a boat with a rope...not dynamic rollover, it was a crash due to stupidity.

[aeroscout]

Nice little sketch...but its not Dynamic Rollover...that is a crash.

 

Kinda like that dumbass in the 206 that tried to pull a boat with a rope...not dynamic rollover, it was a crash due to stupidity.

So dynamic rollover isn't a crash ?

[Francis Meyrick]

link to drawings

 

Interesting, eh? The amazing world of helicopters.

I agree completely it's not a "classic DR". Or is it? It's certainly worth including in the discussion, because the kind of scenario I show in my drawing, is certainly not limited to Tuna boat radio buoy dropping. Right? I've had emails from Seismic pilots, and National Guard Pilots (describing what happens in Afghanistan when you try and big up a load that has been accidentally way, way overloaded), and one great chat with a logging pilot who works here at PHI. The kind of scenario I drew above occurs in myriad different forms in the choppy world. Do we leave our students with the mindset that only "classic DR" occurs? With a skid up against a rock, or something? Classic DR?

The poor guy who tied up to the boat, tried to tow it, and promptly became immortalized on You-Boob... (he's got my sympathy) is it just enough to say "he was stupid and that would never, ever happen to me?" ('cos I'm so good) Caution. He might be a highly intelligent individual otherwise, who in his training stages, formative flying, was never confronted with a diagram like I posted above. Had he been shown similar diagrams, and had he discussed them with his basic training CFI, might this accident have been prevented? Helicopter accidents just abound with people being caught out by something basically simple. Something they never, ever thought they would get bitten by. I have watched it happen, time and time again, to 10,000 hour plus veterans! The older I get, the more my last remaining stuttering brain cell seems to want to communicate some form of "watch it - it's MUCH easier to do than you think". Caution-caution- go easy on the judgments. There for the grace of God...

 

So, is it a classic DR? No. Does it have sneaky ingredients of a DR? I ask the question,

 

 

Building on cburg’s post:

(3 conditions required)

1.) Pivot Point - Roll Over on Level Ground (Takeoff)
2.) Rolling motion - Rolling Downslope (Takeoff or Landing)
3.) Exceeding the critical angle

(and maybe,as a 4th, mention the usual ingredient of "vertical thrust"/up collective/panic-pull...)

 

How about we think up a phrase to describe this kerfuffle? How 'bout

"EVOLVING Dynamic Rollover" ?

 

Or, think up a totally new phrase? It seems to me that the accident scenario involved in "Evolving DR" is a really sneaky one. It could be a skid caught in netting (some tuna boats), caught on a fuel hose, caught on branches. Or it could be a load that get's stuck (seismic, logging, Afghanistan, etc, etc)

Sure, the helicopter gets off the deck. Or arrives overhead in a stable hover. But when it starts unraveling, you might as well have your skid up against a rock. If you keep pulling, and/or putting in "normal" control inputs, you are gonna get HURT.

 

Edited April 22, 2014 by Francis Meyrick

[aeroscout]

I don't see the kerfuffle.

When you sling you make sure the line doesn't go over the skid.

It might not be the textbook definition of dynamic rollover, but your helicopter will roll over dynamically.

All the pre conditions for classic dynamic rollover are being met by all the examples Moggy has mentioned.

There are very few original ways left to wreck a helicopter.

[cburg]

Mosquito Air in grass...he never lowered collective...or move the stick.

 

https://www.youtube.com/watch?v=BL48WyO7JwQ

[cburg]

Here's another close one Bryan posted today (old clip).

00:02:25

https://www.youtube.com/watch?v=7sDKXv0_SNg#t=171