R66 crash in Wikieup, Arizona, U.S.A., kills 2
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aft cyclic then worry about getting upright.
Crab, be careful telling anyone to play with the collective before the cyclic, you will get them killed.
But yes, prevention is better than the cure, and the best prevention is again aft cyclic, as that will make you slow down...
Crab, be careful telling anyone to play with the collective before the cyclic, you will get them killed.
But yes, prevention is better than the cure, and the best prevention is again aft cyclic, as that will make you slow down...
aft cyclic then worry about getting upright.
Crab, be careful telling anyone to play with the collective before the cyclic, you will get them killed.
Crab, be careful telling anyone to play with the collective before the cyclic, you will get them killed.
If you have some G (less than 1 but more than zero then aft cyclic may have a beneficial effect)
Please explain how using the collective will get people killed??
AnFI -
You ask the question. The answer is actually YES YOU ARE WRONG
Do you understand the term control power?
Jellicoe
You get the roll because the cyclic is ineffective and the only thing creating thrust relative to the fuselage is the TR. The roll occurs as a secondary function of left yaw (you have power pedal applied in the cruise) - putting in right pedal is effectively the same as applying collective without adding left pedal - it causes right yaw which will tend to oppose the roll.
As you discovered
it happens quickly and if you had added aft cyclic (instead of holding the controls steady) you would very likely have chopped off the tail.
Just how many accident reports of this phenomenon do people have to read before they understand it?
That reaction could kill you in a 2 blade system, especially the Robinson products. It seems a lot of people forget that the low G is not what kills you in this situation, its the fuselage rolling independently, underneath an unloaded rotor disc. In my opinion prevention is far better than the cure - i.e. slow down in turb, and or try not to fly too light in bumpy weather. But should you encounter a low G roll, pulling on the collective to load the disc will only make the roll and ensuing mast bump happen quicker and more violently.
As you discovered
In saying all that, I have experienced a roll in an R22 once (out of approx 400+ hrs Robinson time, mostly 44 but sprinkled with 22 and 66 time). It happened so quick that i was at 50-60 degrees before I could think about responding. Luckily my hand stayed still and did not correct the roll and we sort of swung out of it. From that point I decided that I probably dont have quick enough reactions to fix the problem after the roll, so decided that I would just slow down and/or not fly on really windy days in the Robbies.
Just how many accident reports of this phenomenon do people have to read before they understand it?
https://assets.publishing.service.go...PUDD_10-94.pdf
here is the one I referred to earlier
here is the one I referred to earlier
Hi Crab, I try not to post on these forums, especially to give advise but there seems to be some misinformation. My concern was the unnerving posts about people loading the disc with collective, which is undoubtably the wrong thing to do. Increasing the torque that is flipping you will just kill you quicker.
I think you are right in that in a completely unloaded disk i.e. zero G, then you have no control power. Any right, left or aft cyclic wont do anything at that point but I think if you get to that position the horse has pretty much bolted and you are just along for the ride.
I think you are right in that in a completely unloaded disk i.e. zero G, then you have no control power. Any right, left or aft cyclic wont do anything at that point but I think if you get to that position the horse has pretty much bolted and you are just along for the ride.
From Robinson http://www.robinsonheli.com/service_...s/rhc_sn29.pdf
and http://www.robinsonheli.com/service_...s/rhc_sn11.pdf read this one carefully as first of all it warns against aft cyclic and then says do it very gently - even the manufacturers can't give consistent advice.
If your automatic/trained reaction is to pull aft cyclic, you might well chop off your own tail - straight from the horses mouth - good enough for you AnFi?
and http://www.robinsonheli.com/service_...s/rhc_sn11.pdf read this one carefully as first of all it warns against aft cyclic and then says do it very gently - even the manufacturers can't give consistent advice.
If your automatic/trained reaction is to pull aft cyclic, you might well chop off your own tail - straight from the horses mouth - good enough for you AnFi?
Chopjock - no it doesn't but if you can't load the disc with cyclic, what else are you going to use to get the rotor pulling the airframe around again rather than waiting to see if it sorts itself out?
Clearly the worst thing you can do is try to oppose the roll with left cyclic but that will be an automatic reaction for most pilots to an undemanded roll to the right.
The only problem with adding collective is if the Nr has decayed due to the reduction in G (negative flare effect) where more power might further reduce the Nr briefly until normal G is restored.
Which would you rather have - slightly low Nr or a chopped off tail?
As has been said before the answer is prevention since the cures carry their own risks and the Robinson safety notices emphasise keeping well below Vne, especially in turbulence - but how many pilots follow that advice or even think about it before they encounter the updraught?
Clearly the worst thing you can do is try to oppose the roll with left cyclic but that will be an automatic reaction for most pilots to an undemanded roll to the right.
The only problem with adding collective is if the Nr has decayed due to the reduction in G (negative flare effect) where more power might further reduce the Nr briefly until normal G is restored.
Which would you rather have - slightly low Nr or a chopped off tail?
As has been said before the answer is prevention since the cures carry their own risks and the Robinson safety notices emphasise keeping well below Vne, especially in turbulence - but how many pilots follow that advice or even think about it before they encounter the updraught?
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no it doesn't but if you can't load the disc with cyclic, what else are you going to use to get the rotor pulling the airframe around again rather than waiting to see if it sorts itself out?
this phenomena was quite pronounced when the AH-1G was fielded in the late 60's due to the maneuvering and high angle/high speed weapons delivery that was used at the time, in fact low-g roll and recovery was a demo maneuver at Cobra Hall until someone discovered how dangerous it was. The corrective action is aft cyclic followed by rolling level. The following is from the AH-1S Operator's Manual (-10)
Capture.JPG
Capture.JPG
Chopjock - unless the nose is pitching down - the SN specifically says ' If the helicopter is still pitching forward when the pilot applies aft cyclic to reload the rotor, the rotor disc may tilt aft relative to the fuselage before it is reloaded.'
As I said earlier, unless you are zero G, you will have some cyclic control but at the lower end of the scale it will seem less effective so judging 'gentle' or 'a little' aft cyclic might be very difficult.
If there is no nose down pitch then gentle aft cyclic should work.
The rapid entry to autorotation is a problem if you push the nose forward - as in the accident I linked to and the other SN - in that case aft cyclic would be disastrous.
Jellicoe - the SN says that aft cyclic would combine MR torque reaction with the TR thrust - the TR thrust is producing left yaw and any application of lever would produce right yaw. It is the reduction in MR Torque caused by flare effect (moving the cyclic aft) that aggravates the yaw and thereby the right rolling motion highlighted in the SN.
As I said earlier, unless you are zero G, you will have some cyclic control but at the lower end of the scale it will seem less effective so judging 'gentle' or 'a little' aft cyclic might be very difficult.
If there is no nose down pitch then gentle aft cyclic should work.
The rapid entry to autorotation is a problem if you push the nose forward - as in the accident I linked to and the other SN - in that case aft cyclic would be disastrous.
Jellicoe - the SN says that aft cyclic would combine MR torque reaction with the TR thrust - the TR thrust is producing left yaw and any application of lever would produce right yaw. It is the reduction in MR Torque caused by flare effect (moving the cyclic aft) that aggravates the yaw and thereby the right rolling motion highlighted in the SN.
LRP - whilst all teetering head helos are susceptible to mast bumping, do the Bells exhibit the rather nasty rapid right roll which is the problem with the Robinsons?
At the risk of getting a bad case of crabs 
,
Unless I'm misreading the report, the comments about entering auto-rotation (with student fixed-wing pilots) are specifically about stalling the blades that already have low Nr.
In this instance forward cyclic and pulling collective would prove fatal.
In the context of the report this isn't proven but rather referred to as being similar to another low Nr-related tail strike.
,Unless I'm misreading the report, the comments about entering auto-rotation (with student fixed-wing pilots) are specifically about stalling the blades that already have low Nr.
In this instance forward cyclic and pulling collective would prove fatal.
In the context of the report this isn't proven but rather referred to as being similar to another low Nr-related tail strike.
Bell ringer - the rotor stall would only occur following a real loss of power, not for a practice autorotation.
FW pilots tend to react to a stall by pushing both hands forward (stick forward and full throttle) which translates to lever down and forward cyclic in a helo - if you do that for a practice autorotation and are even remotely ham-fisted, you can quickly get to a low G, mast bumping scenario.
You can get tail strikes from both low Nr (rotor stall) and low G with associated mast bumping and undemanded roll. FW responses to emergency (or practice emergency) situations can be fatal in both scenarios.
FW pilots tend to react to a stall by pushing both hands forward (stick forward and full throttle) which translates to lever down and forward cyclic in a helo - if you do that for a practice autorotation and are even remotely ham-fisted, you can quickly get to a low G, mast bumping scenario.
You can get tail strikes from both low Nr (rotor stall) and low G with associated mast bumping and undemanded roll. FW responses to emergency (or practice emergency) situations can be fatal in both scenarios.
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Hmmmm
Robinsons are like Islam, should be banned!!
regardless of all the banter and sh*t slinging going on. EVERY pilot should have in his or her mind what they will do in a low G situation.
Personally, I always self briefed Aft cyclic. And always had that in my mind. Hold the cyclic still, then gently aft.
how the hell are you supposed to know if your 0.0 deg low g or .99 low G I will never know.
Plan for it guys, same as places to land if the donk stops. Have a plan of what the recovery is.
Plan. That will save your ass.
An addition to this. Neg G will not cause mast bumping. It's the incorrect pilot actions that causes it. Correct actions can and will stop it from happening.
During low G, there is no main rotor thrust occurring. But the tail rotor still produces thrust. The TRT causes the 2 bladed heli to roll to the right which put the flapping of the blades at maximum. The incorrect but natural reaction of the pilot is to correct the right roll with left cyclic. As the flapping is already at maximum it is then exceeded which causes the blade drop stop to contact the mast. In a very lucky situation the mast may only be bent but somehow holding on. More often then not, the mast is damaged enough the main rotor departs.
To reload the disk, aft cyclic. The pilot must be mindful that low g, you will have a light feeling in the seat of your pants. Then the roll. Aft cyclic (although at that point unnatural) is the best way to reload the disk.
Regardless of different procedures. Robinson state ( well the last time I watched that video) was aft cyclic.
Also, just slow the hang down. What's a 10kt reduction in airspeed?
Condolences to the crew.
regardless of all the banter and sh*t slinging going on. EVERY pilot should have in his or her mind what they will do in a low G situation.
Personally, I always self briefed Aft cyclic. And always had that in my mind. Hold the cyclic still, then gently aft.
how the hell are you supposed to know if your 0.0 deg low g or .99 low G I will never know.
Plan for it guys, same as places to land if the donk stops. Have a plan of what the recovery is.
Plan. That will save your ass.
An addition to this. Neg G will not cause mast bumping. It's the incorrect pilot actions that causes it. Correct actions can and will stop it from happening.
During low G, there is no main rotor thrust occurring. But the tail rotor still produces thrust. The TRT causes the 2 bladed heli to roll to the right which put the flapping of the blades at maximum. The incorrect but natural reaction of the pilot is to correct the right roll with left cyclic. As the flapping is already at maximum it is then exceeded which causes the blade drop stop to contact the mast. In a very lucky situation the mast may only be bent but somehow holding on. More often then not, the mast is damaged enough the main rotor departs.
To reload the disk, aft cyclic. The pilot must be mindful that low g, you will have a light feeling in the seat of your pants. Then the roll. Aft cyclic (although at that point unnatural) is the best way to reload the disk.
Regardless of different procedures. Robinson state ( well the last time I watched that video) was aft cyclic.
Also, just slow the hang down. What's a 10kt reduction in airspeed?
Condolences to the crew.
Last edited by Hughesy; 15th Jul 2016 at 20:42.
Originally Posted by [email protected]
LRP - whilst all teetering head helos are susceptible to mast bumping, do the Bells exhibit the rather nasty rapid right roll which is the problem with the Robinsons?
Last edited by LRP; 16th Jul 2016 at 05:14.
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The AAIB Report, following the crash of this B206 at last year's Isle of Man TT, makes interesting and sobering reading:
https://assets.publishing.service.go...RAMY_06-16.pdf
A combination of inexperience, strong winds and teetering rotorhead.
https://assets.publishing.service.go...RAMY_06-16.pdf
A combination of inexperience, strong winds and teetering rotorhead.
Hughesy - I think that
and
is pretty much the best advice for Robinson drivers.
The second one should help prevent the event in the first place and the second, especially the pause before gently loading the disc is the best 'one-size fits all' recovery strategy.
i didn't want to create a cyclic vs collective argument - simply highlight what is going on in the low G environment so pilots can make their own educated decisions.
Obviously the best decision is not to get in a Robbie in the first place (I have promised my wife not to ever do so again)
Hold the cyclic still, then gently aft.
Also, just slow the hang down. What's a 10kt reduction in airspeed?
The second one should help prevent the event in the first place and the second, especially the pause before gently loading the disc is the best 'one-size fits all' recovery strategy.
i didn't want to create a cyclic vs collective argument - simply highlight what is going on in the low G environment so pilots can make their own educated decisions.
Obviously the best decision is not to get in a Robbie in the first place (I have promised my wife not to ever do so again)