Thoughts

General stuff that gets thrown about when Helicopter Pilots shoot the Breeze.
Low_Level_Hell
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Thoughts

Postby Low_Level_Hell » Tue Apr 4 2017, 01:49

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bangequalsbad
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Re: Thoughts

Postby bangequalsbad » Tue Apr 4 2017, 02:29

CAT?
(Clear Air Turbulence)
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hand in pants
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Re: Thoughts

Postby hand in pants » Tue Apr 4 2017, 21:02

There a couple of statements from this gentleman I would not agree with.
"Pilots have a very healthy sense of self-preservation. They don't tend to do things that are going kill them."
True but, we actually do do things that could kill us routinely. And every now and again, we are killed. I think we ALL have a healthy respect for the dangers in our job, but we do occasionally step over the line and pay for it.

I would ask what they were doing immediately prior to the "mast bumping" and barrel roll.

I will always question it when someone blames the machine. Robinson products have been around for about 30 years, people aren't that slow that they wouldn't catch on to something wrong with the helicopter or some design flaw that will kill us out of the blue.
Hand in Pants, I'm thinking, my god, that IS huge!!!!!!!!
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Re: Thoughts

Postby Jamienz » Tue Apr 4 2017, 21:13

My understanding was that Jim was demonstrating low G at the time, and was therefore prepared for the event, so knew to roll with it. I have heard that from quite a few different (reliable) sources but that seems to be missing from these articles. Secondhand information so could be wrong, but it makes sense as a fair few instructors used to do this.

I know of one other mast bumping event in an R22 where the occupants survived, and this was the result of a new student pushing the cyclic forward in a low speed high power scenario. This time they were about 400' AGL but the instructor did the same thing and basically went with the roll, which went all the way round. The 22 was pretty much a write off, and I personally looked at it about an hour after it happened, it sent shivers down my spine. Very lucky guys, and impressive reactions from the PIC.
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CYHeli
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Re: Thoughts

Postby CYHeli » Wed Apr 5 2017, 04:24

I read an article by Frank Robinson once who described that the roll rate can go to 100 deg per sec, so <2 secs and you are upside down.
Oc:=
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County
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Re: Thoughts

Postby County » Wed Apr 5 2017, 05:02

Only one way to recover from a low g situation and that is aft cyclic and lower collective. In the early 90's the Robinson factory flying course used to train the recovery process.
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Re: Thoughts

Postby arrrj » Wed Apr 5 2017, 08:30

I am not sure I would have the presence of mind to "follow the roll" by doing a barrel roll ! Particularly knowing that teeter rotor heads are not meant for this.

But I haven't flown a 22, so perhaps that's is good.

I do know rule number one though, keep the rotor loaded...all the time, then you don't have to be a test pilot.
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Re: Thoughts

Postby zzodr » Wed Apr 5 2017, 13:27

County wrote:Only one way to recover from a low g situation and that is aft cyclic and lower collective. In the early 90's the Robinson factory flying course used to train the recovery process.


I think you meant aft cyclic and raise collective.
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Re: Thoughts

Postby johnsweapon » Wed Apr 5 2017, 15:17

zzodr wrote:
County wrote:Only one way to recover from a low g situation and that is aft cyclic and lower collective. In the early 90's the Robinson factory flying course used to train the recovery process.


I think you meant aft cyclic and raise collective.


I was under the impression that raising the collective actually made the problem worse, instead aft cyclic and lowering the collective would be the remedy....

Below is an extract I found on exactly that. Maybe worth a read before you go yanking on the collective to get yourself out of Low-G situations.

> Kurt Robinson told me that the company “has always felt lowering the collective is helpful,” but wants to emphasize aft cyclic because it directly addresses low-G loading. Note that some pilots have mistakenly interpreted “reload the rotor disc” to mean they should raise the collective, which will only make the situation worse.) - See more at: https://www.verticalmag.com/features/un ... Yfs3l.dpuf <
agusta
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Re: Thoughts

Postby agusta » Wed Apr 5 2017, 19:57

zzodr wrote:
County wrote:Only one way to recover from a low g situation and that is aft cyclic and lower collective. In the early 90's the Robinson factory flying course used to train the recovery process.


I think you meant aft cyclic and raise collective.



Raising collective will want to make it roll more
Jamienz
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Re: Thoughts

Postby Jamienz » Wed Apr 5 2017, 22:02

yep 100%, raising collective is possibly the worst thing you can do in a low G situation. Unfortunately it seems a lot of pilots have this misconception, including myself when I first did a 44 rating a few years back. There is a US Army film on mast bumping that I think advocates raising collective, and I think few instructors were also promoting it inadvertently. One good thing about all this publicity is that it makes people think a lot more about whats going on during a mast bumping event, and hopefully dispelling some of the misconceptions. Personally I think "quick stop" technique if things start to get hairy in a robbie. Cyclic back, lower collective and right pedal. All things which reduce your chance of a right roll. But the best solution is to either slow down or not be in the air in the first place when its turbulent.
zzodr
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Re: Thoughts

Postby zzodr » Thu Apr 6 2017, 01:27

Well I'm always willing to learn, so..
I'm all ears on how raising the collective (obviously not yanking it, not pulling it all the way) is somehow detrimental to a LOW G recovery.

The roll is a secondary effect of the Low G condition, remove the Low G condition, the roll stops, correct?
The roll is caused by the increased tail rotor effectiveness, right drift, left yaw, aerodynamic sideloads etc etc = rapid roll to the right.
Due to reduced main rotor thrust during LOW G. We are flying the discs, the fuselage reacts.

Raising collective increases rotor thrust, increases G loading on the disc. Generally regarded as a good thing during LOW G condition.
Obviously AFT CYCLIC is the primary and most effective remedy.
Lowering collective causes the nose to drop, and initially lower G loading. We all know this from practice autos. You can feel it on entry.
So, why make an input that reduces the effectiveness of aft cyclic and REDUCES G load during a LOW G recovery?

Or just leave the collective where it is. But lowering it does not help a Low G recovery, nor is it mentioned in any Robinson safety notice for LOW G recovery.


Recovery action

Prevention is the best rule. Never get into a negative G situation in a two bladed helicopter system by intentionally using abrupt control inputs. If you do experience a negative G for any reason then the obvious solution is to reload the rotor disc so that you are experiencing positive G. This can be done by

Using aft cyclic to increase the G force and use right cyclic to follow the roll

Raise collective to increase the total rotor thrust and help increase the G force

Once the G force has been restored then you can recover to straight and level flight.


http://www.myaviationschool.com/aviatio ... mping.html
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Re: Thoughts

Postby Helicoil » Thu Apr 6 2017, 01:58

zzodr wrote:Well I'm always willing to learn, so..

Or just leave the collective where it is. But lowering it does not help a Low G recovery, nor is it mentioned in any Robinson safety notice for LOW G recovery.



The roll is caused by T/R thrust acting above the aircraft centre of gravity. When you lower the collective, you reduce torque and at the same time you'll instinctively push in right pedal which will reduce the strength of the force causing the roll...

I heard a story that a certain exceptionally high-time R22 pilot went to Frank suggesting a change to the flight manual to lower collective instead of aft cyclic for low-G situations as it was the better recovery method. Apparently Frank agreed, however couldn't make the change to the POH due to the risk of litigation.
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Re: Thoughts

Postby LVDT » Thu Apr 6 2017, 06:33

So the "natural reaction" to the right roll is to use aft cyclic and follow the roll?

Really? Do you get a second go if you "forget"?

A bit more light reading for you. https://www.verticalmag.com/features/un ... d-reasons/
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rotors99
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Re: Thoughts

Postby rotors99 » Thu Apr 6 2017, 07:01

Do you get a second go if you "forget"?


Yes sure........in your next Life pop;
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Eric Hunt
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Re: Thoughts

Postby Eric Hunt » Thu Apr 6 2017, 07:54

Well, I'm with Zzodr on this one, load the disc to reduce the low g.

When you lower the collective, you reduce torque and at the same time you'll instinctively push in right pedal which will reduce the strength of the force causing the roll...


...but what if your instincts are a bit off? Now you have less torque and less disc loading, but the same force on the tail rotor, which will make things far worse by adding a bootful of yaw to the roll - just watch the mast bump speed up now! Because the yaw will make the fuselage roll, from the airflow hitting it while hanging below the disc.
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rotors99
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Re: Thoughts

Postby rotors99 » Thu Apr 6 2017, 08:18

Reducing power makes absolutely no sense....it is adding to the problem of a disc being further unloaded. As for avoiding low/negative-G maneuvers sure, but what about unexpected turbulence, or up/down drafts. So the potential for this to occur is real. Getting the disc reloaded is a key to surviving. Aft cyclic; yep makes sense. Unloading the power-pedal so therefore squeezing in on the R pedal in a USA made machine would reduce the roll. Lowering the lever....naaar Oc:= F that pop;
Last edited by rotors99 on Thu Apr 6 2017, 13:14, edited 1 time in total.
Jamienz
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Re: Thoughts

Postby Jamienz » Thu Apr 6 2017, 10:26

I'm no expert on aerodynamics but have been on a couple of the Robinson courses, including the factory one held by Heliflite here in Auckland last year. The clear consensus from every A cat instructor, every Robinson representative, Tim Tucker, Kurt Robinson etc is aft cyclic and lowering the collective. In that order or combined.

The right roll and how hard it flicks is completely relative to how much power in use you have. Raise the collective and it will roll quicker.

In all honesty, I reckon by the time its starting to roll, the average pilot has little to no hope in saving it at that point. The best protection is prevention. Slow the bastard down, or even better don't be there in the first place.
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Re: Thoughts

Postby County » Thu Apr 6 2017, 11:51

Aft cyclic and lower collective. That's how we were trained to recover from an induced low g situation by factory instructor. How ever in my 28 years of flying Robinson Helicopters I have never been in a low g situation other than in that training environment.
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Re: Thoughts

Postby County » Thu Apr 6 2017, 11:55

County wrote:Aft cyclic and lower collective. That's how we were trained to recover from an induced low g situation by factory instructor. How ever in my 28 years of flying Robinson Helicopters I have never been in a low g situation other than in that training environment.

zzodr.... your way off the mark mate.

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