R22 G meter

[Goldy]

Ok, so I am flying along hitting some thermals, climbing 500 FPM at around 18 inches of MP and doing 75 knots....I love free lift. However, just how much of a neg G gets you into a mast bumping scenario? and even if I knew that number, how do I know just how much neg G I am currently experiencing?

 

I know when I fly gliders there is a G meter on board. It registers both negative and positive G forces. Anyone ever thought it might be a good idea to have this on the 22, and mark in red those areas where the rotor can become unloaded???

 

Is this idea just too simple ?

 

Goldy

[Collective Down!]

Not sure how low the G's have to be before it's a problem in the R22, but loosely related...

1. During the RHC safety course, Tim Tucker said (off the record) that the negative G and mast bumping potential is most dangerous at high speeds, particularly above 80 knots. I think that might be part of the reason the speed recommended for flight in turbulent air is 0.7 VNE (it contradicts that and says 0.9 VNE in another part of the manual), but no less than 60. I heard they used to demonstrate low G during the RHC course... Maybe one of the R22 veterans could answer your question from personal experience.
    
   
2. If i remember correctly, a Jetranger is limited to 0.5 G or more.
   

[FauxZ]

I've also heard anything under about half a G is dangerous. Nothing to back that up though.

[Goldy]

I've also heard anything under about half a G is dangerous. Nothing to back that up though.

 

 

Yeah, I remember from the safety course its around 1/2 a G. Now if I could just calibrate my stomach so I knew exactly when I hit that number !

 

Goldy

[lelebebbel]

I doubt that there is a precise number you have to hit to get into a low G roll - from what I heard at the robinson course, the forward airspeed and the resulting height of the tailrotor above the CoG play a big role here, too, so at different airspeeds, you'll probably experience the roll at different G forces. Another example that the G-forces aren't the only factor: I bet you can get close to or even below .5Gs by just dumping the collective, without getting a rolling moment.

 

I'm trying to develop a reflex to just give gentle aft cyclic whenever I feel light in the seat.

[FauxZ]

Forward airspeed is certainly a must, otherwise you're just rolling the helicopter around a point rather than causing any large downward acceleration. I've heard of it being demo'd at the safety course. They'll fly you at a very low airspeed, 20kts for example, and just jab the cyclic forward, no low G. I've never personally done it, and don't plan to with my limited experience either. I also do not endorse such behavior mind you, just passing along what I've heard. While my brain tells me it's perfectly fine, I'd like to have some practical experience to back it up..

[Pogue]

Forward airspeed is certainly a must, otherwise you're just rolling the helicopter around a point rather than causing any large downward acceleration. I've heard of it being demo'd at the safety course. They'll fly you at a very low airspeed, 20kts for example, and just jab the cyclic forward, no low G. I've never personally done it, and don't plan to with my limited experience either. I also do not endorse such behavior mind you, just passing along what I've heard. While my brain tells me it's perfectly fine, I'd like to have some practical experience to back it up..

Yeah, they did that to me at the safety course. Very slow and went sharply nose down without any ill effects on anything but my heart rate. They also did a very gentle pushover at moderate speed to demonstrate the right roll. Even with the a slow roll I could see how a mast bump could happen - it didn't even really feel like low g. I understand why they took low g out of the flight training guide - I think there were as many mast bumps training for it as there were without the training. I'm convinced it's a good situation to stay away from. :-)

[Worldcrime]

Not sure how low the G's have to be before it's a problem in the R22, but loosely related...

1. During the RHC safety course, Tim Tucker said (off the record) that the negative G and mast bumping potential is most dangerous at high speeds, particularly above 80 knots. I think that might be part of the reason the speed recommended for flight in turbulent air is 0.7 VNE (it contradicts that and says 0.9 VNE in another part of the manual), but no less than 60. I heard they used to demonstrate low G during the RHC course... Maybe one of the R22 veterans could answer your question from personal experience.
    
   
2. If i remember correctly, a Jetranger is limited to 0.5 G or more.
   

 

Just a thought but if Tim told you something off the record, it should be off the record - not published on the internet.

 

 

richard

[celticmatrix]

I definitely remember the low G demo that was given to me by the pilot I flew with at the Safety Course - the faster you fly the faster you enter the roll condition and the easier it is to get into with the slightest forward "bump" of the cyclic.... It was demonstrated at moderate and higher airspeeds for me since the guy I flew with thought it pertinent due to the fact I was working on my commercial rating, and therefore operating at higher cruise speeds - and is not something I'll soon forget!

 

All I can say is that it is always in a pilots best interests to have those emergency procedures ingrained into their system to the point of reflex.

 

As for the G meter that is something I'm unfamiliar with - what is the typical size and weight?

[Collective Down!]

Just a thought but if Tim told you something off the record, it should be off the record - not published on the internet.

 

 

richard

 

Haha, yeah but it's not really a huge secret... Like a lot of posters have already concurred, they used to teach it and demonstrate it at the safety course.

 

Don't forget the primary objective of the safety course... To share information that will make the Robinson helicopters safer by educating the folks who fly them. When Tim or anyone else says something "off the record" I'm sure they want the information disseminated, they just don't want the legal backlash it may bring.

[Guest pokey]

Just a thought but if Tim told you something off the record, it should be off the record - not published on the internet.

 

 

richard

 

I don't mean to come off as disrespectful----but that sounds typical from someone who is from D.C. the reason for forums like this is to learn B4 "we" actually make the mistake & sharing ANY info like this? in MY book it's okey dokey

 

 

As for the G meter that is something I'm unfamiliar with - what is the typical size and weight?

 

it's 2 & 1/4 inch instrument, dont weigh much at all & is easily installed in your panel--make sure you do a log book entry tho, & sign w/ a A&P number & all the legal stuff that you may need to go along w/ the installation

[Guest pokey]

Is this idea just too simple ?

 

Goldy

 

 

I used to do alot of loops, aileron/snap/barrel rolls, spins & ALL kinds of combinations of the above--NOT in a helicopter ! (of korse !) & the G meter isnt "watched", it really just tells the pilot after a maneauver that: "you are having tooo much fun OR did not execute the maneauver properly & may break the airplane IF you keep it up" One actually gets used to the G's, both positive & negative. To unload the system & get "light in the pants"--------ya dont need a G meter. Go take an aerobatic ride & you will see what i mean

[Worldcrime]

I don't mean to come off as disrespectful----but that sounds typical from someone who is from D.C. the reason for forums like this is to learn B4 "we" actually make the mistake & sharing ANY info like this? in MY book it's okey dokey

it's 2 & 1/4 inch instrument, dont weigh much at all & is easily installed in your panel--make sure you do a log book entry tho, & sign w/ a A&P number & all the legal stuff that you may need to go along w/ the installation

 

 

Point taken.

in MY book it's okey dokey

I'm all for sharing safety info. I'm a FAAST team counselor and have my own aviation safety business. All I'm saying is "off the record" usually means just that.

Richard

[joker]

Goldy (et al.)

 

I have read this thread with interest and am in two minds.

 

First I wonder of the necessity of a g-meter installed. If a pilot knows the contributory factors, the and the dangers of low or negative G, then a meter should not be necessary. The value of the Gs is not really important, because the danger is a combination of the low G and the speed (aggressiveness) and direction of the pilot input. 1/2 G has been banded around as the (un-official) redline. However, as someone mentioned, mast bumping can still occur at higher Gs with the wrong pilot input.

 

Secondly, I actually wonder if an installtion of some sort of 'low-G' indicator could have an opposite effect and be contributory to accidents.

 

Imagine the aircraft fitted with a low-G meter. The pilot now has a false sense of security, as he flies along happy that he is not at that 1/2G redline. He believes he is now immune from this hazard.

 

Another scenario is a 'Low-G Horn'. Again, the pilot flies along....he gets into a low-G condition, and the mere horn causes a panick (I have seen this with the Low-RPM horn) and he over reacts.

 

Personally, I truely believe that with this hazard, pilot knowledge and prudence can avoid situations without the need for such a meter.

 

Regards,

 

Joker

[joker]

Goldy (et al.)

 

I have read this thread with interest and am in two minds.

 

First I wonder of the necessity of a g-meter installed. If a pilot knows the contributory factors, and the dangers of low or negative G, then a meter should not be necessary. The value of the Gs is not really important, because the danger is a combination of the low G and the speed (aggressiveness) and direction of the pilot input, as well as the speed and pitch of the aircraft. 1/2 G has been banded around as the (un-official) redline. However, as someone mentioned, mast bumping can still occur at higher Gs with the wrong pilot input or speed.

 

Secondly, I actually wonder if an installtion of some sort of 'low-G' indicator could have an opposite effect and be contributory to accidents.

 

Imagine the aircraft fitted with a low-G meter. The pilot now has a false sense of security, as he flies along happy that he is not at that 1/2G redline. He believes he is now immune from this hazard.

 

Another scenario is a 'Low-G Horn'. Again, the pilot flies along....he gets into a low-G condition, and the mere horn causes a panick (I have seen this with the Low-RPM horn) and he over reacts.

 

Personally, I truely believe that with this hazard, pilot knowledge and prudence can avoid situations without the need for such a meter.

 

Regards,

 

Joker

 

Hmmm...seems that I have double posted! Maybe a mod can delete Post #14!

Edited September 12, 2007 by joker

[Goldy]

I used to do alot of loops, aileron/snap/barrel rolls, spins & ALL kinds of combinations of the above--NOT in a helicopter ! (of korse !) & the G meter isnt "watched", it really just tells the pilot after a maneauver that: "you are having tooo much fun OR did not execute the maneauver properly & may break the airplane IF you keep it up" One actually gets used to the G's, both positive & negative. To unload the system & get "light in the pants"--------ya dont need a G meter. Go take an aerobatic ride & you will see what i mean

 

Pokey- read my post....it says when I fly "gliders"....I am guessing you have never flown a glider since you think I need an aerobatic ride ?? Most gliders are good for around 10-12G's...and nothing does 70 degree turns and loops better than a glider. Not to mention the entire purpose of the flight is to find thermals, place your aircraft in them, and hang on for the Neg G ride to the top. So, yes I try to scan the instruments ( in a glider...its like 3 of them..hey why is there no oil pressure !) and I do occasionally glance at the G meter just to see where I am at....although I dont recall ever seeing +8 ( thats a joke!).

 

I was just thinking at 65 knots..how much Neg G does it take? How do I know what margin of safety I have at that speed. I have been in a couple 1000 ft/min thermals that make you feel pretty light in the 22...and thats not easy for me at 240 pounds.

 

Like I said, just had a thought at 1000 AGL.....hmmm

 

Now, I want 10% of the proceeds when somebody gets a STC for an R22 G meter !

 

Goldy

[nicepants]

I've also heard anything under about half a G is dangerous. Nothing to back that up though.

 

When practicing autos, it certainly feels like we hit .5 G or less. One particular auto, we were pulling near max power and it felt like I was coming down the first drop on a roller coaster....definitely less than .5Gs, but we never got into a tail-high attitude.

[FauxZ]

I've thought about that too but haven't been able to find anything in print to back up my theories. Anyway, I'm assuming it's because you're not Low G for long, assuming it's even enough low G. On top of that you are reducing tail rotor thrust and torque, both of which add to the roll, and lastly you are not putting the tail rotor as far above the center of gravity as you would in a push over. Simply my own theories.

 

I do remember them saying at the safety course that they tested all sorts of power settings and tail rotor positions to try to minimize the roll and that's how they came up with the aft cyclic recovery as the best option. They said nothing else really had much of an effect. That's as close to an official answer as I've been able to find.

[HelliBoy]

Here's a thought about the momentary neg. G in the entry portion of autos. The no tail high sounds good but; what happens if you enter while nose low in that time it takes to apply aft cyclic and get the t/r down??? Low G roll?? Probably not. Heres why in my opinion;

The neg.G feeling we get when we abruptly enter an autorotation is not the same as the neg.G we get from a pushover. In a pushover we unload the rotor to the point when it is only attached to the mast by an unloaded hinge because we've used something other than the lift created by the rotor to change the momentum of the two bodies. Its basically on its own. The fact that we're traveling in the same direction is merely coincidence. In contrast, when we enter an auto abruptly we still have a loaded rotor, we're pulling down on it. The helicopter would not get started on its downward path if the lift wasnt removed from the rotor by lowering the collective, which means that the gravity takes over and the fuselage pulls the rotor disk down with it. We may have a negative G or close to it but the disk is not unloaded.

I'm not an engineer or physicist but the lack of any information concerning the low G we get on autorotaion entries makes me think that the disk doesnt get unloaded. Combined with (and those of you who've had the low G demo in the past know what I'm talking about) the negligible ammount of tail high attitude you need for the roll to show itself.

 

This has really sparked my interest and although I dont fly teetering hub helis anymore, I want to see if my theory is correct before I ever repeat it in an authoritative fashion over cold beer. So if anyone knows for sure whats going on here please set me straight or stroke my ego.

[Goldy]

Pretty hard to unload a rotor with 1370 pounds hanging under it and gravity pulling it straight down..lets not forget the 65 knot attitude you are in during an auto also, and the fact that you are producing zero power ( torque).....Im done stroking.

[nicepants]

Pretty hard to unload a rotor with 1370 pounds hanging under it and gravity pulling it straight down..lets not forget the 65 knot attitude you are in during an auto also, and the fact that you are producing zero power ( torque).....Im done stroking.

 

The explanations here make it easier to understand. Clearly not all in-cockpit "low g" conditions are equal. I asked my instructor about this as well and his response was that in an auto we don't have an "unloaded" rotor. Good info...that's one less drop of sweat on my forehead during my next auto ;-)