Low G in R-22?

[rjtjrt]

The other day on lee of a mountain range on a hot day (41C) sudden sharp turbulence downdraft and aircraft rolled right. To say I was apprehensive is masterfull understatement. Towards the end I gingerly put in a bit of left pedal (harking back to fixed wing days to stop the right roll I thought whilst avoiding any left cyclic input. The downdraft lasted about 5 seconds, I guess, and it didn't feel easy to reload the rotor (ie positive G) whilst in the downdraft. I held cyclic rigid till it got to about 45 degrees right roll whilst I kept repeating "I don't like this" to myself (I was alone) and by then flew out of it and positive G, then cyclic left till rotor level.
My question. Is there any role (no pun intended) for left pedal as an ancillary action in stopping/recovery/reducing the right roll of low g in a semi rigid rotorcraft if for some reason can't immediately re load the rotor with back cyclic? (I acknowledge the primacy of re loading the rotor by use of cyclic).
John

[tony 1969]

I thought the right roll is caused by the tail rotor so pushing left pedal would actually worsen the situation. Could be wrong though I frequently am.

[Heli-Jock]

Ton1969,
You are quite right this time, whilst the rotor head is not loaded with posotive G, the tail rotor is the culprit for right roll.
So more left pedal would make this condition worse!
I'm not sure if squeezing the right pedal would help, but ive always been taught to reload the disk with gently aft cyclic before trying to make right the attitude of the aircraft.
I've had low G demonstrated in a R44 at the Robinson factory last november and what amazed me most is that a reasonably quick forward movement of around 4-6 inches on the cyclic was enuf to put us in a low G condition and start a steep bank to the right.
"Dont try this at home"::

[KNIEVEL77]

John,

You say you've been to the Robinson factory.......do they have any courses or training facilities that one can go to?

K77.

[Heli-Jock]

Knievel77
Yes, they run a 3 and a half day safety course, in Calafornia,details of which you will get from the robinson web site. The courses are booked well in advance so i'd reckon you will wait a few months for a place.
It consists of 3 days safety briefings from various well experienced pilots.
They also give you around 1.3 hrs on the 4th day, R22 or R44, with one of they,re instructors.
Its a great and worth while experience if you fly Robinsons.


JF

[KNIEVEL77]

Excellent, thanks for that John.

[HeliCraig]

They are currently booking for November this year - so it is a bit of wait, but apparently well worth it.

Just sent my application off, having scanned licence etc!

[Bronx]

More info here Robinson courses (http://www.pprune.org/forums/showthread.php?p=2332636)

[muffin]

There are also courses held periodically here in the UK. Some of them are run by the guy from the factory who does the US courses, so have exactly the same content.

I would suggest that you get your PPL first though, as you will then be in a better position to understand what the course is all about.

[delta3]

Low G can/will indeed happen when hitting a strong downdraft.

This low-G should be treated with the same remedy as a pilot induced low-G : take the cyclic aft gently to reload the disk.

Some time ago this was discussed, some pilots had some ideas about using pedals (not me), but a plank like left pedal is most certainly not the answer, it is dangerous.

Downdrafts in moutainous areas just don't fall out of the sky, they are quite predictable, when one observes the mountain ridges vv the wind. Many times they are preceded by an updraft. In that case flairing in advance at the first signs while reducing speed is what I would advise (during the previous updraft), because in the downdraft you can pull some extra collective.

d3

[biggles99]

But in principle RJTJRT did the right thing.

he didn't panic, he didn't fight it, he didn't make any sudden and/or excessive corrective control inputs.

All of us who have been there will know how hard it is not to have a hand-jerk reaction when it feels like the hand of God has just slapped you sideways.

good for you, RJTJRT

Big Ls

[dragman]

The right roll is not "caused" by a low G scenario, but because the pilot has not reacted to it. As the rotor disc unloads due to the down-draught and pedal settings are not changed, the nose will yaw left which will begin a right roll through parasite drag on the fuselage. The manual recommends the aft cyclic input before lateral etc.

Now take a step back to the down-draught and as the low-G feelings come on, watch that very expensive piece of string attached to the bubble. If you keep it in balance by adding some right pedal, I'd bet my beer fridge and it's contents that the roll won't happen.

[dragman]

rjtrjt, you asked a very good question about the use of pedal to recover the roll. Yes this does work when flying a stiff-wing and is a good way to avoid stall through aileron use on approach by "picking up" the wing, but as tony and john mentioned, it certainly would worsen the situation and is something that stiff-wing pilots making the transition to choppers should be aware of.

[[email protected]]

dragman - in the low to zero g scenario, the TR is the only thing producing any force that can act on the fuselage. It is displaced vertically and longitudinally from the C of G (especially where forward cyclic has created the zero g) and that is why the fuselage yaws and rolls, not parasite drag.

[FLY VFR]

Yes the course is run in the Uk by Richard Sanford. Robinson's accident/technical investigator. A very knowledgeable person, and well worth sitting his course. As mentioned above, its over a 3 day period, 2 full days in the classroom and the 3 day is split, with an hour or so flight demonstrating what has just been taught. From my experience of the course I think every Robinson pilot so take it, and have heard lots of Robinson pilots who say they will change their attitude with regards to flying the Robinson having attended the course.
The course was run in conjunction with a flight training school, so I wouldn't know where the next course will be held but I do have Richards's Telephone Number and Email address should you need it.

[dragman]

[email protected],

I hear what you are saying, and agree that during a cyclic pushover the c of g would be much lower and any TR thrust would cause a roll. But I was led to believe it was a combination of this and that during the ensuing skid to the right, the fuselage lags behind due to an airflow onto the starboard side - or in other words - an increase in parasite drag

[NickLappos]

dragman has it right! The tale is a scary one, but only to those who congratulate themselves when they make a successful landing. The idea that through turbulence lone he experienced lower than 1 g for more than a fraction of a second is simply not believable. The roll he described could certainly have been caused by the disturbance, sans low g, but then the dialog would have been much less like Poe and more like Gann. Give us a break here, guys!

From 140 knots in an S76, you cannot sustain zero g for longer than 2 seconds, on purpose. This fellow saw nothing like that folks!

Please remember that 'low" g is not zero g, and it takes close to zero g to lose a robbie, in fact, it takes some pilot help to make air turbulance into a robbie-killer. Typical helo turbulence against the highly loaded blades of the helo don't create less than about .6 g ever, and more likely perhaps .8 g. Can someone who flies with a g meter please chime in?

When everybody is finished congratulating the poor sod for flying into turbulence, can we get back to ppruning?

[TwinHueyMan]

I'm in no way an experienced joe in this matter, but I had quite a fright while out on one of my first solos in a robby, right after watching Frank's horror film, doing some orbiting around a field next to a nice mountain. Hit a downdraft, felt a right roll from an already steep right orbit, scared the bejeebus out of me and ruined a brand new set of fruit o the looms. Sure enough on the next flight with my instructor, I felt "low G" during a downdraft in flight and the right roll came on again. I got very white and was confident our mast was miliseconds away from departing so thus added quite a bit of aft cyclic, to which the instructor asked why I banked right and slowed. Told him I felt we were in a low G situation and was taking appropriate measures... he mentioned that we were nowhere near the point at which the chopper would roll right on its own. Apparently when we got a little light, I would get a little too frightened of the chopper, and let it do what it wanted to do... which, with the trim pushing on the cyclic, was roll right. A nice ride through the mechanical turbulence of the downtown skyscrapers with him at the helm, coming through unscathed, and I was right as rain again. I've since rode much bigger downdrafts and never gotten scared again... just a little preemptive aft cyclic and on we go.

Not saying that you weren't in a low G arena rjtjrt, but all the chaps I fly with here in Hawaii say they have never seen an uncommanded right roll in turbulence, and it gets very rough out here. Add to that, the gents who got to do the low G training at the Robby factory when it was still there said the roll was faster than you'd imagine... not much time to realize and react with the proper aft input. Their advice was to keep the aft cyclic in mind, use a little every time that you feel light, keep the chopper level, and turbulence is no big deal. Till you hit a thunderstorm. Then unbuckle, sit on the instrument panel and shove the cyclic up yer bum... Makes it interesting for the crash investigators. Always thought that was a good one.

Just what I've been told.

Mike

Mike

[[email protected]]

Dragman - in normal flight, say 70 kts, if you yaw left, the aircraft will roll left not right because the disc flaps back relative to the direction of travel (which hasn't changed) and not relative to the fuselage heading (which has changed). Normally the 2 are co-incident but, unless you oppose the flapback with cyclic, you won't get a right roll with left yaw.

[rjtjrt]

"When everybody is finished congratulating the poor sod for flying into turbulence, can we get back to ppruning?"
Nick
Was it a stupid question?:confused:
I agree it may have just been a turbulence induced roll and not low G. I was not prepared to assume it wasn't low G at the time and use left cyclic to recover. I don't have your experience. That's why I asked the question.
Not trying to be smart, just unsure. I am low time - 80 hours. I am about to do the Robinson Safety Course with Tim Tucker and will ask him.
John

[rjtjrt]

TwinHueyMan
Mike
Thanks for an informative reply. Very useful information.
John

[MightyGem]

Was it a stupid question?

rjtjrt, if you don't know the answer, there are no stupid questions. It's always nice to make sure. The hard part is picking out the right answers from all the posts!!