Another New Generation Rollover

[Brian]

Some of these new generation gyros do not have clearance between the prop & rotors until rotor revs get up to a certain speed so thats why they pre rotate stick forward. Why dont they just lengthen the mast, well I"m guessing no 1 they wouldnt fly as well & 2. probability of rotor shake would be more likely. [ I"m guessing there ] so go ahead & shoot

[WEST OZ FLYER]

Additional: If you remove the micro switch, say good bye to any hopes of warranty....the reason the switch is there, as well as to supposedly stop flap, is because the mechanism might not run successfully or reliably with the added stress of stick back deflection of the head? If prerotation with the stick back where it needs to be on the takeoff roll could be approved by the manufacturer, it would be a great leap forward IMOExactly MadMauz. The switch is there to stop you cutting off the tail. Maybe they could put a light on the instrument panel at a safe rrpm that tells you you can go full backstick while prerotating. A bit like an idiot light I find it hard to believe that any prerotator system has trouble prerotating at full back stick, flex drive, shaft drive or what ever. If they prerotate at full forward stick of 0* then full back stick is 9*. Any universal joint will tolerate that. The standard pinion angle in a car is 6-8*"s. with out adding suspension movement to it. Your car drives fine and the tail shaft uni"s last for a really long time don"t they? Disco, I"m not talking about starting the blades at low rrpm"s. It"s all about getting the blades back while prerotating. ( when they sufficiently clear the tail ) The MTO3"s have a switch where by the stick has to be full forward and centered. If you do a "book" take off where by you enter the runway, line up on the piano keys and prerotate with a slight crosswind you can not lean the disc into the wind. I would prefer to prerotate head on into the wind (preferably while on the holding line not taking up runway time) then take off slowly but the "book" says line up then prerotate and that is what some instructors are teaching.Birdy the only ones have I have seen (paid attention to) is the MTO series. I think that Magni might have it right. There was a new M24 here a couple of days ago. Too busy looking at his leather interior thinking it takes all sorts to make the world go round. ;D Never paid much attention to that part as these Euro"s don"t do much for me. My theory is it is easier to change the relative airflow to the disc with the prerotator engaged travelling forward that it is trying to match airspeed from a very low airspeed to a disc that is at 2/3 flight speed. Better to catch up to a constant rrpm than accelerate into decaying rrpm. Chopper, I am only saying that going full back stick while prerotating at a safe rrpm for the tail. Still starting with full forward. To me the delay from prerotating to getting the stick back and firewalling the throttle is causing some of the problem. Holding the stick forward trying to take off,

[birdy]

Firstly, full backstick should be bout 18*, not 9, but yes, if the systm is designed proper, its very doable.My made up raf spinners will get to bout 90% flight rpm.I start with the stick full forward, or into wind which ever dirction its comen from. Saves stopper contact that happens if just centered.If im confined, ill let the stick onto the backstop and keep spin,n till its at maxed. The rotor makes for a good airbreak.I wont go into detail from this point, but the spinner stays on till im clear, of wotever is in my way.Why these million dollar tubs cant do this is beyond me.

[WEST OZ FLYER]

Firstly, full backstick should be bout 18*, not 9, but yes, if the systm is designed proper, its very doable.If the the system designed proper the angle from zero is 9* forward or 9* back. Sorry not real good at explaining stuff on this computer.

[MadMuz]

I think what you are trying to say westy, is from neutral/middle stick it is approx. 9 degrees each direction.... but from full forward stick (9 degrees forward of centre) it is 18 degrees to the back stop.... so you are both correct.... typing is a pain to get all info across without interpretation you would get smile to smile

[eigyro]

The stick must be held forward during prerotation due to mechanical limitations.The Hookes joints used in the prerotator need to be kept in line when rotating,otherwise destructive pulsing occurs at the driven (rotor) end.Therefore, the rotor must be prerotated to a higher rpm than would otherwise be necessary,to allow for the falloff in rotor rpm between releasing the prerotator, releasing the wheel brake, pulling the stick back and accelerating the machine to the point where the rotor begins to accelerateagain under aerodynamic load.The time taken to do the above transition, the rate of application of power, and the headwind, willall effect the point at which the rotor picks up speed aerodynamically. This will be tricky if you knowbuggerall about rotor management.Hence the take-off-by-numbers routine. Mostly, it works. Get the sequence wrong/push the limits,and it gets expensive.I understand this process has been simplified somewhat by a switch that disengages the prerotatorif the stick is not full forward. Whether simplification was the reason for this, or whether it was to stopfolks damaging the prerotator, or damaging the tail, I do not know. Possibly all three.In a Magni, you begin prerotation with the stick forward.The stick can be moved rearward as the rotor rpm builds, taking advantage of any headwind,and putting the rotor into flight attitude, before releasing the brake and adding power.Less falloff of rotor rpm, simpler procedure, less prone to errors.I wonder why we rarely hear of these takeoff problems with Magnis.Steve UK will assure you it is due only to the numbers sold. I don"t agree.If I was running MT, I would fit a Wunderlich-type prerotator, or a CV-jointed shaft system,and a centrifugal teeter stop system, (as per Twinstarr and Wallis )system.I have yet to hear a cogent argument for the radical stick-back rotor angles on the MTs.You cant come near these angles in flight, and I suspect it doesn"t ACTUALLY improve takeoffperformance.Anyway, if your runway is that short, it"s too short.

[Disco]

If the the system designed proper the angle from zero is 9* forward or 9* back. Sorry not real good at explaining stuff on this computer. Added to this 18 of travel, 2 degrees of forward helps give you the range for what might need to be done on the ground.

[gyroo]

Howdy guys,HUB TILT AND ROTOR TEETER ANGLE RANGESReading a few of the posts above there seems to be a bit of confusion about tilt and teeter angles.Let"s get back to basics a bit. The forward and aft pitch range of the tilting spindle rotor hub should be 9 degrees forward of the usual cruise spindle angle, and 9 degrees back from the usual cruise spindle angle. If the usual cruise spindle angle is 9 degrees back from the vertical (a fairly average number), then it follows that on the ground full forward stick should push the spindle to true vertical, while full back stick will have the tilting spindle tilted back at 18 degrees back from the vertical.But, lets also not forget that within the tilting hub we also have a teetering hub-bar and rotor. The UK research has confirmed that it is easily possible for an incipient or transient teeter angle of 8 degrees to occur if the stick is jabbed in flight. ASRA recommends a teeter range of 9 degrees + 9 degrees = 18 degrees teeter range within the hub itself. "Teeter" is the term universally applied to a rotor see-sawing within a rotor hub. "Tilt" is the word universally used to describe the range of angular movement that the hub and spindle are capable of. So, the hub "tilts", while the rotor "teeters" within the hub.If set up in the way ASRA recommends, with the rotor stationary on the ground orientated fore and aft and with the stick back on the rear stop, and the rotor pulled down to the rear teeter stop within the hub so that it is above the tail, we end up with 18 degrees spindle tiltback PLUS 9 degrees teeter allowance, which EQUALS a total of 27 degrees down angle on the rear facing blade. In other words, a gyro should be set up to allow the rear facing blade to tilt down 27 degrees from true horizontal (but this basic information omits any adjustment for the average 2 degrees inbuilt hub-bar coning angle). But, during a flapping event the rotor tip path plane can easily sweep well beyond those stop limits and hence that"s why tails often get struck off to the right during a rear-up leading to roll-over.Some people add 2 to 3 more degrees to the forward spindle tilt range to allow for a spinning rotor on the ground to be tilted forward at a near-zero-lift angle of attack as well as to facilitate friction rotor brake pads making contact with the ring gear to stop the rotor. Rigging the spindle to allow for a few degrees extra forward of vertical also theoretically would be an allowance to cater for the increasing disparity between the spindle axis and the rotor tip path plane as flapback occurs as airspeed increases. The only time a rotor spindle axis is truly perpendicular to the rotor tip path plane is during a zero airspeed vertical descent. At all other times during forward flight the spindle axis will always be tilted forward a bit relative to the tip path plane, and the angle increases as airspeed increases. It is actually not necessary to build-in an allowance for that because I simply cannot imagine any in-flight situation at higher speeds where a pilot would find his control stick contacting the forward stop - or put another way, if that did occur it"d be the last thing the pilot experienced as he or she bunted over and entered the land of Oblivion.Cheers,Mark Regan

[birdy]

The only times my spindle would be on or near the frunt stop in flight is only momentarily dureing an inertia hover/landing.

[WEST OZ FLYER]

The stick must be held forward during prerotation due to mechanical limitations. The Hookes joints used in the prerotator need to be kept in line when rotating,otherwise destructive pulsing occurs at the driven (rotor) end.eigyro, I know that they have an inherent fast and slow side at an angle but I find it hard to believe that a Hookes joint at a slight angle can cause this damage. In a Magni, you begin prerotation with the stick forward. The stick can be moved rearward as the rotor rpm builds, taking advantage of any headwind, and putting the rotor into flight attitude, before releasing the brake and adding power.Less falloff of rotor rpm, simpler procedure, less prone to errors.My argument exactly.

[MadMuz]

The only times my spindle would be on or near the frunt stop in flight is only momentarily dureing an inertia hover/landing.Ahhh... so you are admitting that gyros can hover?

[gyroo]

The only times my spindle would be on or near the frunt stop in flight is only momentarily dureing an inertia hover/landing.Yep - I agree with Professor Birdy. In helicopters the most likely time that your cyclic stick will come close to the front stop is after an aggressive "quick stop" where as you fly horizontally about 50 feet up at 50 to 60 knots, you drop the collective then feed in back stick progressively to do a flare to a stop without gaining or losing height. The chopper can easily assume a 30 degree or more tail down attitude and as the airspeed falls to zero you bring collective back up as well as feeding in a real lot of forward stick, and that"s the time when you"ll come close to the forward stop. The maneuver sounds complicated but after practice it is surprisingly easy to do and outwardly looks quite dramatic.Birdy"s "inertia hover/landing" is really a gyro quick stop.In choppers during quick stops or autorotation landings the name of the game is for skids to be level at the end of the maneuver, whereas in a gyro you can still have the gyro nose up when the wheels make contact with the ground.Mark R

[birdy]

Did i ever say a gyro couldnt do an inertia hover M&M?The thing to remember in both gyros and choppys is to be sure you are always at 1G or more, specialy ina choppy, or your disc will out run the machine. Mast bump ina choppy and stopper hammering ina gyro, basicaly the same thing.In gyros its not so risky, coz to do an inertia hover you need oversped rotors ( or you dont hover), and oversped rotors means you have more n 1G lift.Ina choppy, if you just stick forward to level without feedn enuf pitch, the rotor wont be producing enuf lift to heave the machine around, and itll get left behind.

[Disco]

Prof Birdy makes a man think.

[birdy]

.??????Never heard a SCG be,n called a professer before, dose this mean i geta bita alfabet after me name?