Double amputee Solo in RAF 2000

[gyroo]

Howdy again T-Bird,Murray"s point is that the unique RAF mast mounted stabilator is actually a horizontal stabilizer for the torque tube or torque bar. It is naturally heavily airspeed dependent. Its purpose is to keep the torque tube or torque bar orientated at a pre-selected angle to the oncoming airflow, and therefore the rotor tip path plane will also be stabilized because the spindle is rigidly attached perpendicular to the torque bar. It is true that RAFs with the stabilator can be flown for prolonged periods hands-off-stick. But, what Murray is talking about is that in this hands-off situation the stick will pitch forward or aft of its own accord if the pod is experiencing a bit of pendular effect in turbulence. And, in such turbulence its conceptually much better to leave the stick alone because the stabilator will be free to do its work without interference.If the pilot of this stabilator-fitted RAF, who is sitting in a fixed position in a pod experiencing a bit of pendular oscillation, grabs the stick and prevents it from "doing its own thing", then - in effect - the pilot and the stabilator are fighting against one another. That"s what Murray is commenting about.There"s nothing wrong with a bit of mechanical stability augmentation - look at the Hiller control rotor in Hiller 12s, or the Bell stabilizer bars on Bell 47s or UH-1B"s, C"s, D"s. E"s or H"s. The point is that modern gyros simply don"t need mechanical stability augmentation - except for the RAF!Mark R

[tonydenton]

your wearing them down mark.

[t-bird]

Thanks Mark.It makes sense.

[gyroo]

Thanks T-Bird,Much of what we"ve all been discussing back and forth can perhaps be lumped under "Handling Qualities" which is a much more informative label than "dynamic stability". The fuselage or pod of every rotorcraft to a greater or lesser extent will behave like a pendulum under the rotor (those with good horizontal stabilizers are much less subject to pitch "excursions" as they are called). The control stick is almost always anchored to the floor of the pod and human brains seem hardwired to instinctively and subconsciously want to keep the stick steady with reference to its surroundings in the pod if the pilot at any given moment is not intentionally maneuvering. Gyros are more prone to PIO than many types of aircraft because most are very "short coupled" - they are often short and stubby and don"t have a nice long fuselage with nice big tail surfaces a long ways back from the CofG like planes have.The subconscious tendency of a human to try to keep a stick steady within a cockpit is also one of the main ingredients of PIO, where with the pod pitching back and forth a wise and experienced pilot will realise "I don"t need to try to damp out or chase this", whereas an inexperienced pilot will fall into the trap of doing control stick pitch movements that he or she thinks will dampen down the pendular pitching. In the vast majority of cases even the most ham-fisted newbie won"t actually do much harm and things will settle down within a number of seconds until the next upset or turbulence hits. This is all part of the post-pilot-certificate self-learning process that we all know so well: learning to leave it alone, to not make things worse. Very occasionally, however, an unfortunate newbie"s control stick movements will exacerbate the pod-pitching tendency, or in other words their stick inputs will be so badly out of phase with the pod pitching that their inputs actually worsen the pitching instead of dampening it.The fact that many gyros are completely open-frame without a pod shouldn"t be overlooked. In these configurations it is absolutely essential for a newbie to have a visual airframe reference as far out in front of him or her as is possible. The ideal situation is a radio aerial on the very front of the keel with the top of the aerial level with the horizon from the pilot"s viewpoint when on the ground. In flight all the newbie needs to then do is watch where the top of the aerial is with reference to the horizon. If an open-frame gyro hasn"t got any such visual airframe reference for a newbie there"s a potential PIO disaster lurking just around the corner.History (in the UK and here) seems to show that very occasionally inexperienced pilots caught in extreme turbulence tend to try to "plow through" no matter what and in-effect wrestle with the controls chasing and trying to counter the pitching and rolling. Rolling isn"t too much of a problem, whereas pitching is. In extreme turbulence with little experience, things can get so bad with the pitching that the g-loading on the rotor is substantially unloaded and the mast-pitching-or-rolling moment able to be produced by the rotor vanishes, but the ability of the rotor to wildly flap or even flail does not (called unconstrained flapping) because the rotor is still at a high rpm.In these seconds, speaking from a dynamic point of view, we come to a fork in the road. Fork in the Road 1If the machine is CLT or near CLT, such as a Newo, there will be no tendency for the pod to bunt over because the thrust line is more or less in line with the gyro CofG. Nevertheless, if the pilot is absolutely determined to plow through "no matter what", then the rotor is likely to be encountering transient episodes of reduced or even severely reduced-g and in this circumstance the inexperienced pilot will be finding that no matter what he or she does with the stick, the gyro doesn"t seem to be responding (because any pitch-tilting-moment being generated by the unloaded rotor is reduced in reduced-g). The pilot then unconsciously over-controls or puts in harsher or harsher stick inputs. Now, despite the fact that the unloaded rotor can"t tilt the mast, the rotor is still spinning at near-full flight rpm and the tilting head is being swept through extreme angles. The rotor will try to follow the harshly tilting spindle and that"s where the catastrophic flapping - or unconstrained flapping - comes in, in exceptional circumstances being violent enough that within one or two rotor revolutions the teeter stops have well and truly been struck and the head partially wrenched off the mast and one or other of the blades will sweep down so violently that a blade scythes through the pod. This has happened in Australia in both helicopters and gyros. This is what happened with the Newo customer first-pick-up-flight fatality you mentioned - the pilot had previously held a fixed wing licence and inexplicably just "firewalled" it determined to plow through extreme turbulence.I stress that for such a catastrophe to occur one must have the near-lethal combination of heavy turbulence, a gyro being flown at very high speed, and a pilot inexperienced in gyros absolutely determined to "plow through no matter what" and who is wrestling and chasing the controls and overcontrolling.Fork in the Road 2If an identical set of circumstances arises with a gyro that is significantly High Thrust Line (HTL), then the catastrophe described above will happen much earlier in the event and more assuredly. This is because the High Thrust Line WILL pivot or pitch or bunt the gyro forward around the gyro"s CofG UN-COMMANDED even before the situation with the reduced-g rotor has got to the point where there is unconstrained flapping. A common and telltale characteristic of PPO in fatal accidents is evidence of multiple and progressively worsening rotor strikes on the vertical stabilizer and/or rudder. Frequently, in these PPO accidents the VS and rudder are located away from the main wreckage indicating the rotor strikes detached and flung those surfaces away from the plummeting gyro.What has happened with the HTL gyro here is that essentially although the rotor has not yet reached the "point of no return" (or in other words it"s not yet flapping catastrophically), the gyro frame itself is now pitching forward uncommanded because the thrust line is so much higher than the airframe CofG. The final icing on the cake in this particular recipe is that as the pilot senses the un-commanded bunt or nose-down pitching, he or she will naturally pull the stick back. However, it is extremely likely that the bunt-over will have already put the rotor into a severely reduced-g situation and wrenching the stick back hard won"t save things - in fact it"s likely to induce the unconstrained flapping spoken of in the paragraphs above, this time induced in a slightly different way. Another way of imagining this is that as the gyro bunts over, the frame is taking the rotor over with it. The pilot, however, pulls harshly back on the stick but that may either stop the rotor bunting further or may cause it to flap back harshly. In any event the tail has come up into contact with the rotor so it"s all over anyway.The end result will be pretty much the same - the rotor is likely to be pitching back harshly as unconstrained flapping starts up, but in any event the gyro frame and tail are bunting over and the tail comes up into the rotor arc that much quicker.You will now appreciate that it is often subtle differences in the wreckage that enable the break-up sequence to be determined and for whether a PPO has occurred.Conclusions From the analysis above one can see that it is possible to turn any gyro into pieces of aluminium confetti if one really, really tries hard enough to destroy one in flight. The same can be said for any flying machine, or indeed even any car if a driver deliberately and suicidally has a sudden impulse to veer off the road and aim for a tree.The hypothesis with HTL gyros is, bac

ked up by the University of Glasgow research, that in the harrowing conditions outlined above the HTL gyro is very much more likely to PPO to destruction before unconstrained rotor flapping starts.The more HTL a gyro is, the more readily it will enter un-commanded PPO.Cheers,Mark R

[mad max]

All gyro pilots should be trained to instinctively pull the throttle back during turbulent conditions and keep a sharp eye on the ASI. The conditions generally drive you up anyway due to high airspeeds. I often allow the craft to face a new direction if it wants to for a while untill things settle down again. Going through inland whirl winds is frightening at first but can be fun once you develope the skills to survive and loose some of the fear. (I must confess if I have a passenger at the time I refuse to talk while concentrating).

[t-bird]

Hi MarkI can add that in a overcontrolling situation you will loose 100 RPM a second. I agree also that overcontroling will happen much quicker with a RAF. You would then expect to see RAF pilots dropping out of the sky like flies.Why aren"t they ?Does it have to do with the demographics of the pilots ? It looks like they attract a lot of farmers that are older. Could be that they are risk more adverse than younger pilots.Training at an international airport ? Everything has to be to the book and pilots are more dissiplined.The instructors. These guys really know the machine and give the student the ability to fly in a wider envelope. How big a role does the hours training play.The machines. The machines are all the same, Mark mentioned how smooth the rotors were.Or that 20 000 hours is not that great and the only reason we don"t see those statistics here is that very few of the muster pilots are submitting hours.

[gyroo]

Yes, yes -Perhaps I should have added that once a rotor goes into reduced-g, the auto-rotative effect diminishes proportionately and the rotor can slow disastrously within seconds. It may not necessarily instantly slow, however, because the reduction of auto-rotative effect is accompanied by reduced induced drag as well, leaving the rotor"s considerable rotational inertia only battling parasite drag. On the other hand, we also now know of instances where a rotor has gone from 320-340 rpm to less than 90 in a second and a half (Nowra, February 2014), but in that case the rotor experienced top down inflow that braked the rotation.The disaster scenarios I have described in excruciating millisecond-by-millisecond detail in my previous lengthy sermon are FORTUNATELY extremely rare. They don"t happen regularly here or anywhere else in the world - yet they occasionally DO happen. And the important bit is we now know why they happen. This simple statement couldn"t reliably be made 25 to 30 years ago. Such a detailed explanation couldn"t be reliably made even 15 years ago.It"s probably time to stop emphasizing the disaster scenarios for a while and to acknowledge that many tens of thousands of hours of pleasurable and trouble free gyro hours are enjoyed here, and in South Africa, and everywhere else in the world gyros can operate.Aside from the formal training we all have, our gyro-learning experiences continue on for as long as we fly. That"s why we all instinctively and routinely use the descriptions of "inexperienced pilot" or "experienced pilot", with the assumption being that perhaps the experienced pilot will have scared him or herself enough times early on to learn that it"s best to avoid things that he or she may have done when first "let loose".It would be good if you could explain more about the South African training regimes, methodology and training philosophies, and more importantly what will happen to people if they operate outside the official regime. One recurring phenomenon that ASRA has is that quite a few people join ASRA, then learn to fly, then lapse their membership. Anecdotally, we know that they"re out there flying away but they"re no longer "legal" because a pre-requisite of legal gyro flying in Australia is ASRA membership.Is this phenomenon also encountered in South Africa?I"ll finish up by saying that many tens of thousands of extremely pleasurable gyro flying hours are experienced in Australia and elsewhere every year. If people think I"m all doom and gloom, then that"s just not the case.BUT - I reckon that there has to be someone resident on this forum who"s got the inclination to explain the intricacies, and as Tech Mgr it"s logical that I be the one. I think it helps that I"ve got half a bookcase full of rotary wing textbooks and can actually penetrate at least part-way into the labyrinth of calculations contained in them, and that I have previously flown planes and choppers as well as gyros.

[birdy]

Or that 20 000 hours is not that great and the only reason we don"t see those statistics here is that very few of the muster pilots are submitting hours.???how many use rafs for mustern?Never heard of anyone.

[gyroo]

Good morning Birdy -Heard it was 45 out your way yesterday?Newer readers may not know that you"ve had both a RAF as well as your famous "Feral" at the same time. Why did you muster in Feral and not the RAF?

[t-bird]

Birdy it is not just about Raf hours but hours in any gyro.The accident rate will be very high if not all the hours are accounted for.Say

[gyroo]

T-Bird you"ve really got the bull"s eye with this one.

[Brian]

Or that 20 000 hours is not that great and the only reason we don"t see those statistics here is that very few of the muster pilots are submitting hours.???how many use rafs for mustern?Never heard of anyone.Yep, I know of 2 RAF"s back years ago but not today. One bloke said he had found 10,000 different ways to sit in one & the other learnt a lot in a very shot space of time & got out of the raf into a single place gyro

[birdy]

Heard it was 45 out your way yesterday?45 wut?[i]Why did you muster in Feral and not the RAF?

[birdy]

TBird, your confusen me.You kept bangn on bout 20.000 hours and no carcasses in SA, then you say 20,000 hours is missrepresenting coz the mustern blokes dont tell.Exuse me for thinkn they was the same hours.Mark, if the mustern pilots were respected for the ligitamate work they do, instead of the "authorities" sayn they are just dangerous cowboys and dont pay casa any privilage money, maybe more would surface.

[t-bird]

Hi
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