Vertical Descents

[Greg Mitchell]

G'Day Frank,Sorry to hear of your accident Frank. Good that you walked away unscathed. Thanks for sharing your experience.Best regards,Mitch.www.thebutterflyllc.com

[birdy]

I too am sorry bout wots happened to you and your machine [but glad to ere your still around to tell us bout it] but not half as sorry for the advice your get'n.Either I'm readn it cockeyed or your instructer is have'n trouble with understanding wot happened.I'll try to explain my concern.If you first tryed right rudder, I assume you "appeared" to be spinning left.IOW, the horison was going from left to right, right?If you had forward AS, right rudder would have stopped the spin,0 AS and nuthn happens, BUT, if you were going backwards it would have accentuated it.[ think of it as reversing a motor car, lookn forward, you have to steer in the opposite direction to the way you want the car to turn.]In a gyro thats go'n backwards, it 'appears' to be spinning left, coz your still lookn forward, at a horison thats go'n left to right but its actualy spinning right, backwards, so the opposite input is needed to stop the spin."the Gyro lurched back I actually lent forward into the harness," It takes a few hours before you can stare at your rotors with out unintentionly applying some input to the stick.[try riding a scooter and look up over you shoulder as you did in the gyro, see how far you get.]"Then she started to spin slowly, the blades started to hammer the stops"If your in a virtical power off decent, the disc is horisontal, meaning theres no cyclic adjustments to the blades if the machine starts to spin, BUT if theres backstick, the blades will hammer the stops or even the high cyclic inputs are enough to kick the stick as the blades try to follow the machine round in a spin. "I banked to the right away from the spin nothing happened, banked left into the spin this was a concern I thought this could possibly make things worse, still nothing,"When your in a panic situation, or even unsure wots go'n on, when you try to regain control of the machine, time seems to stand still. You apply wot you 'think' is a correction, nuthn happens imeadiatly, so your hart rate jumps some more and you try sumthn else, not giving the machine time to react.[which is exactly wot happens in a PIO.]"I spoke to my instructer the next day He said my best chance for recovery would have been to bank into the spin and hold it there, slide the gyro sideways presenting a lowered blade to the airflow creating some airspeed over the blades and unstalling the disc,"Banking into the spin is right if you were go'n backwards[ which is wot it sounds like,] but its not to "unstall' the disc, coz the disc can't stall, wot your doing is actualy banking OUT of the spin, coz your go'n backwards."also stop the prop"Cut'n power is the best thing you can do in almost any out of control situation, in this case, it'll help to bring the nose down with the stick forward and arrest the reversed airflow. "Torque is what coused the problem and then made it worse when I powered up,"????????????????.I think wot happened is when you powered up, you increased the airflow over the rudder, which, when fly'n backwards, woz pointing the wrong way, make'n the situation worse."There is a bit of a myth in Gyro cicles that these machines are a lot safer than fixed wings you can't stall or spin,No direspect to you Frank, but that ain't a myth."One possible reason given me for the spin was the size of the prop 76 inches produces a lot of leverage."While a prop can induce a spin in a virtical decent[ which BTW is nuthn like a FW spin], its not sumthn that cant be stopped.Where people get into trouble is if the spin they encounter is slightly forward, vertical, or slightly backwards.Slightly forward AS and pure virtical need the same inputs to arrest a spin, BUT reversed airflow in a spin requires reversed inputs to be stopped."Behind the power curve is not a sink"Lastly, if its not a sink, wot is it???[ I'd like to know coz I do it all the time.]As I stated earlier Frank, I'm not trying to be a smartass or disrespectfull, but I don't think you have a clear grasp of how these machines work.[ No sure you should be ask'n your instructer either.]This should draw some flack, mite retreat to me bunker I reckon.Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.

[asra]

Hi Frank.Who is your Instrutor if you don't mind me asking?

[Brian]

Glad you are okay Frank but I agree with Birdy in what he has said. I will also re interate that a gyro is one of the safest flying machines in all regimes of flight.A spin is a manourver that has to be carefully done otherwise things can get out of hand quickly. I'm quessing you havent a lot of hours up Frank and you have entered a spin accidently and as well have started to tail slide, not an ideal way to spin. Its also very scary when controll inputs dont have the desired effect and to have the blades hammering the stops means that things arent in good shape. Its a good lesson to low hour pilots in that they need to keep their attention on flying the gyro at all times, if you are concerned about any part of a gyro while flying, land and check it out on the ground. If you would like to know whats happening up at the rotor head, get a friend to video it for you. Personally, I dont like seeing that head shake anyway ! A gyro is a very sensative machine to controll inputs and thats what makes it such a hoot and fun to fly as well as being an ideal machine to use at low level to work stock.If its any help, my FW instructor hammered into me, AVIATE, NAVIGATE then COMMUNICATE in that order!! So at all times, fly the gyro!!!Brian

[asra]

I think Birdy is actually Chuck Beatty with a brough(sp?)....OK, Chuck Beatty with a different accent. I should never try to be clever after a couple beers []

[birdy]

??????????Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.

[Brian]

Birdy, just wondering, you seem to have a good idea on what happened with Franks spin.Okay, he has pulled the nose up pretty high, got cruising power on, gyro has come to a halt then starts a backward slide, rudder isnt straight as gyro starts to spin backwards, spin a is getting quicker. Its from here on I havent got a clear picture of the spin, I see it nose high going backwards spinning fairly quickly, wouldnt the rudder being straightened and nose lowered the way to recover ?? Power would need to be reduced to idle ? Would the nose want to lower seeing the blades are "hammering" ? Sounds scary to me !! Brian

[Scott Hogan]

Frank,Just as a matter of interest, what sort of tail does your gyro have?Hoges

[asra]

Question ?Could someone explain how it is that a gyro's rotors continue to autorotate in a "vertical" desent ????????????????? Considering there plain of rotation and direction of airflow.Regards Sam. []

[Brian]

Sam, the airflow is coming through the rotors from below as the gyro descends. Thats another reason why gyros are so safe and dont stall.Brian

[asra]

BrianAutorotation happens due to the reletive airflow striking the blades at an angle of attack, and lift being produced at 90 degrees to that airflow.Because, the lift vector is in front of the axis of rotation the blades are self powering.If you consider what happens in a vertical desent, the rotor disc is either flat or angled back.The now reletive airflow is now striking the blades from below, so this would, as I understand it, stall them.Or am I missing something here!!!!Regards Sam. [?]

[Tim]

Sam the relative angle of attack changes very little whether in forward flight or vertical descent. You must take into account the speed of the rotors when determining the relative angle of attack. In both cases the air is striking the rotor Rotor at a fairly shallow angle of attack.Tim McClure

[asra]

Tim you've lost me. How can the angle of attack be small when the air is now striking the blades from below.And how does rotor speed influence angle of attack. Sam. [V]

[NiqueNaque]

Sam,Up velocity initially is say 10 mphRotor velocity is 250 mph at tip, therefore angle is inv tan 10/250the faster the rotor speed, angle for 300 mph is inv tan 10/300 even more shallow.

[asra]

Come on NickYou know Im just a simple bloke, who struggled with maths at school.I do understand that an aerofoil section raised higher than 15 degrees, will begin to experience airflow seperation.And I do understand how flapping increases and decreases the blades AOA.But still struggling to understand autorotation in a vertical descent, as there is no flapping occuring, and the reletive airflow and blades AOA is definatly higher than 15 degrees.More like 100 degrees plus.Sorry fellers, must be all the rain we had, has waterlogged the brain. Sam [V]