Why Rotax 915 power won't mean more blade sailing accidents - rotor management is not the issue! 

Really informative, extremely well explained and makes perfect sense 👍🏻

A good way to think about this is your retreating blade stalls. The teeter is adding angle of attack to the retreating side to compansate for difference in airspeed between each rotor. Once it's stalled you're in trouble if you are going too fast. The disadvantage of a blast rotors up to 3/4 of flying rpm and then start ripping down the strip is your rotors will decelerate until they reach a sustainable match. If people don't believe this then prespin to say 200 on a no wind day release pre rotator then watch what happens to rpm if you stay put. It seems to me as someone who's flown in mostly gryos without prerotaors other than my arm that the whole process is much more manageable if you prerotate enough to get going and then match airspeed to rotor rpm. This isn't very high speed so everything is happening slowly. Generally my takeoff run was slower but my ground used was often less. This was because a) I would wind up from the taxiway so was ready to take off as soon as I entered the strip so I probably had 80-100rpm (no rotor tacho) but my ground roll would be about 10-12 mph until the blades started to pick up the a touch more then nose lift then more power establish balance then gradually add full power lift off at 20mph hold a foot or 2 then climb out at 35mph (best LD). It strikes me many of these take off issues appear to be basically too much happening too soon for the pilot to manage. Prerotating does not mean you stop managing rotors. I used to regularly get off in half the distance of machines that were lighter, more powerful wit prerotators. They were off sooner but I used less airstrip. Now that would not be true had I not taxiied and gotten 80-100 rpm but give me that and gradual must win everytime. If you pump the coals on and the wait till rpm increases sufficient to lift the nose and get balanced you are either a) taking off behind the power curve or b) eating airstrip. IMO we have too much focus on power, taller machines, longer rotors, more powerful prerotaors. My driect drive VW with 22ft rotors was off the ground at 20mph climbing at 35mph. Why are these machines not getting off till 40mph? Why are they climbing at 60mph. My VW was under powered and about the same weight as a 912 why does gaining 40hp suddenly degrade performance?

Thanks a lot for this informative info.

100% agree on this Phil, I can't see any connection between engine power and blade sailing...? If anyone has any other input I'd love to hear it.....

I love watching these vids and am slowly accruing knowledge that will hopefully stand me in good stead when I finally have the chance to front up for instruction. Can I respectfully suggest you improve the audio by getting closer to the mic, using a lav mic, USB mic or an XLR mic with a USB interface? Despite the the fact that you obviously know your stuff, improving this will really pull the production value (and perceived authority) up a couple of notches.

I curious now 3 years latter (just re-watching) if there has or has not been in increase in hinging/flapping accidents with higher powered gyros. I have noticed watching many of these accidents in modern machines is they often get blamed on blade flap (hinging) instead of over rotation. Having watched many a set of blades hinging/flapping over the years - and been the one it was happening to as a gyroglider instructor as well. The blades when hinging make a characteristic S shape that is really pronounced. If both blades are conned up IT AIN'T BLADE FLAP. In hinging/flapping as one half of the rotor is essentially fully stalled it will be curved towards the ground. Most of these accidents you see attributed to this are simply over rotation then hitting the blades on the ground as a result. I think this is more to do with the aggressive nature of the take off run trying to chase the rotor rpm (to avoid blade flap). I think both types of accidents would reduce if pilots adopted the older method. Pre-rotate to lower initial rpm. Wind up using airflow by only increasing forward speed when the rotors were ready thus you are reducing angle of attack and decreasing time to get the blades to accelerate. Blades hitting the air at higher relative angle of attack will have less forward component of lift and accelerate faster. This would both reduce ground distance used and hence give better distance to avoid obsticles and reduce both genuine blade flap incidence (which I suspect most are not) and reduce over rotation incidence because you are not suddenly having everything all happen at once. Although I am a tired record of this opinion by now I'll keep banging on until we see some change.

As a fixed wing pilot, I’m curious as to why there is an emphasis in a Gyro on IAS rather than purely the Rotor Speed (RPM). To me, I would be much more interested in the Rotor speed than my speed through the air - which is really only relevant to a “wing”. Is it wrong to say that a rotary aircraft’s lift depends entirely on the RPM of the blades? In which case wouldn’t you agree that there should be a whopping great big RPM gauge with colour coding for caution and danger zones (helicopters usually have a warning horn for slow rotor RPM too) rather than the usual reference to IAS? There is usually a correlation to RPM and IAS and I can see that, but to me most of the accidents that you have described would be avoided if the pilot was completely aware of the rotor speed and therefore the relative lift that can be expected from that RPM. I’ll be keen to see what anyone else thinks. Cheers - love the channel and looking forward to a Gyro flight once COVID is over ..!

Bingo!

Why the design of the rotor allows the blade to hit the propeller or any parts of the craft ?

its almost as if, a rotor tach is a more important instrument than an airspeed indicator. Especially since airspeed can be fauxed to an extent by a simple drag gauge but I cant think of a way for a home made simple device for rotor RPM Although I bet at least some of these machines already had rotor RPM instrumentation and went in anyway

Its the hand that rocks the cradle. . .

Poor rotor management and probably not enough emphasis on rotor blades by instructors it doesn’t matter how horse power you have you will still flap blades if you travel quicker than what the blades can handle

Is there an audio rotor speed warning? Just like stall warning?

“Goats are like mushrooms, because if you shoot a duck, I’m scared of toasters.” Boe Jiden

ERROR!! The narrator refers to the force acting on the rotor blades as "centripetal" force! This is incorrect! The correct name of the force is "centrifugal" force (the spinning parts try to move away from the center of spin). Centripetal force is the inverse of centrifugal force - the spinning parts move towards the axis of spin!! Do your own research and verify this!