AR-1 N159WT Oregon

[BEN S]

Tyger, "You're killin me Smalls!"

 

[Abid]

Thats fine Fara, as I said this is the forum to bring up these ideas or comments.
My point on what I do for a living was to emphasize that dangerous tasks can be taght as well.
If you are so certain (and you keep saying you are) that strict adherence to the POH is the panacea of safety, I guess your andwer is you would have picked the 22 year old CFI.
The issue is not what to do or train when everything goes right, its whay you do the things you do so you can control things when they go WRONG!.
Book written in 1930s called Stick and Rudder....good book.
Again. I have no desire to "win" this discussion. I don't sell or train in Gyros.
I just will not sit idly by and not say something if I feel there is a problem.

I tend to not follow the lead of answering questions that don't have any relationship to the problem. The young or old CFI is that type of question to me. We are discussing a technical specific topic and I simply avoid philosophical discussions when we are at such a stage because the relevance is way too loose IMHO.

Again going back to outrunning the rotors. You can only outrun them when your forward speed exceeds capacity for the blades to handle dissymmetry of lift. The lower the rotor RPM, the more danger you are in of getting there quickly if you make a mistake and as you yourself have said in "real life" people make some mistakes. I agree. Thus you give them a procedure that takes that into account. We know that around 8.8 degrees of incidence autorotation is difficult to sustain and rotors will start to flap. Your Advance Ratio is too close for comfort when you start moving forward at low rotor RPM.

 

[Tyger]

Tyger, "You're killin me Smalls!"

I wasn't going to say anything, but Dave provoked me!

 

[BEN S]

Just so were clear, 8.7 degrees is okay?

Dude....I'm out.

 

[Resasi]

You can only outrun them when your forward speed exceeds capacity for the blades to handle dissymmetry of lift.

Not to be too picky Fara, but it is possible to get blade flap/blade sail without moving forward at all...and I have experienced it.

I liked flying the Benson (no pre-rotator) on windy days. (Not in this particular clip.)

On one very windy day, I pushed it out in the anticipation of some fun flying.
I was on my own so once ready, held the stick forward, facing into wind, stood up and began turning the rotors, sat back down and buckled in with the anticipation of then being able to very quickly nurse up the rotors then be able to taxi away.

To my dismay the wind was so strong, in excess of 20Kts that the slightest attempt to bring the stick back resulted in blade flap with the stick immediately beginning it dreaded side to side jerking.

I was not able to get the rotor up to speed and that was without moving at all. The wind speed alone prevented it. These were Rotor Hawks a comparatively mild mannered blade.No flying that particular day.

But yes, when the speed of the wind through the rotor disc, exceeds the capacity of the rotors to handle it...ie rotor rpm is too low...then blade flap/blade sail will occur.

 

[Abid]

Not to be too picky Fara, but it is possible to get blade flap/blade sail without moving forward at all...and I have experienced it.

I liked flying the Benson (no pre-rotator) on windy days. (Not in this particular clip.)

On one very windy day, I pushed it out in the anticipation of some fun flying.
I was on my own so once ready, held the stick forward, facing into wind, stood up and began turning the rotors, sat back down and buckled in with the anticipation of then being able to very quickly nurse up the rotors then be able to taxi away.

To my dismay the wind was so strong, in excess of 20Kts that the slightest attempt to bring the stick back resulted in blade flap with the stick immediately beginning it dreaded side to side jerking.

I was not able to get the rotor up to speed and that was without moving at all. The wind speed alone prevented it. These were Rotor Hawks a comparatively mild mannered blade.No flying that particular day.

But yes, when the speed of the wind through the rotor disc, exceeds the capacity of the rotors to handle it...ie rotor rpm is too low...then blade flap/blade sail will occur.

Yes basically wind sped seen by rotor disc in rotor disc plane exceeds the capacity of given rotor RPM to take care of dissymmetry of lift and you have a flap. Completely you can have it in windy enough day with very low rotor RPM. We can experience it on taxiing while rotor is turning which is how I try and show students what an onset of flap feels like and then stop and hang in to the stick forward into the wind till it stops.

 

[Abid]

Just so were clear, 8.7 degrees is okay?

Dude....I'm out.

Yes 8.7 in such a rotor would be ok but very close. Generally you are in the 2.5 to 5 range normally. Anyway as a pilot you don’t need all these numbers what you need are key numbers for operational purposes and those are in the procedures given in the POH. All this is figured out for you to keep you well clear of most danger.

 

[Vance]

We know that around 8.8 degrees of incidence autorotation is difficult to sustain and rotors will start to flap. Your Advance Ratio is too close for comfort when you start moving forward at low rotor RPM.

Please help me understand.

What is 8.8 degrees of incidence?

What is my advance ratio that is too close for comfort?

I thought a two blade semi rigid rotor flapped to manage dissymmetry of lift.

Most of the events that I investigated where the rotor struck something happened in windy conditions.

How do you measure something on a rotor to a tenth of a degree in turbulence?

 

[EI-GYRO]

No one is seriously suggesting that anyone should start tandem blades by hand.
What is being suggested is that (an early) part of the training should be the art/technique of patting up a set of blades on a static
single-seater, or rotor training rig. The knowledge thereby safely gained should pay off later in a much better understanding of rotor
management, and a consequent reduction in takeoff screwups.

OTOH, keep stuffing more and more powerful engines into machines that don't need them, and break out the popcorn.

Repeatedly stating that the pilot should follow the procedures clearly is not working. While correct, it achieves nothing.
It comes under the heading of repeating the same experiment again and again and expecting different results. Not gonna happen.

I know I'm farting against thunder here, but sometimes you just have to fart.

 

[Abid]

No one is seriously suggesting that anyone should start tandem blades by hand.
What is being suggested is that (an early) part of the training should be the art/technique of patting up a set of blades on a static
single-seater, or rotor training rig. The knowledge thereby safely gained should pay off later in a much better understanding of rotor
management, and a consequent reduction in takeoff screwups.

OTOH, keep stuffing more and more powerful engines into machines that don't need them, and break out the popcorn.

Repeatedly stating that the pilot should follow the procedures clearly is not working. While correct, it achieves nothing.
It comes under the heading of repeating the same experiment again and again and expecting different results. Not gonna happen.

I know I'm farting against thunder here, but sometimes you just have to fart.

It is working at least in the case of AR-1.
It’s the ones not being taught the process listed in POH and thus not following the procedure who are having the accidents. Can't say its not working till you show me that people who were taught POH procedure are flapping left and right on T/O roll. That has not happened yet. Of course it will but not so far in 5 years. But I am all for hand patting static displays. Hopefully CFIs will set them up at their flight schools and hangers who believe that's the way to go.

 

[Abid]

Please help me understand.

What is 8.8 degrees of incidence?

What is my advance ratio that is too close for comfort?

I thought a two blade semi rigid rotor flapped to manage dissymmetry of lift.

Most of the events that I investigated where the rotor struck something happened in windy conditions.

How do you measure something on a rotor to a tenth of a degree in turbulence?

Advance ratio, I am sure you have heard of it. Its applicable in prop as well as rotorcraft. Sometimes called Mu. Its simply relates to rotor rotational speed to air velocity (generally indicated airspeed). Obviously that is the problem in a flap in this case of outrunning the rotor or too much speed for given rotational speed. Its just an easy way of talking about that relationship then using all those words to explain it.

From Wikepedia
The advance ratio μ is defined as:

where

V∞	is the free-stream fluid velocity in m/s, typically the true airspeed of the helicopter
Ω	is the rotor rotational speed in
r	is the rotor radius in m

Incidence in this case is the mechanical angle between the chord line of a blade element/station against its rotor disc plane. Mechanical pitch angle. When you go too high a pitch, no matter the angle of inflow, autorotation will not be possible. This is different than disc AoA. In a flapping situation the blade is twisting, bending at different stations and also in a sinusidal form.

You don't need to measure it necessarily, they have modeled it and also measured it (Nikolsky and Seckel). Its not something you need to do as a pilot. Although the GWS measures teeter angle with a sensor quite accurately so things like that can be done

 

[Vance]

Advance ratio, I am sure you have heard of it. Its applicable in prop as well as rotorcraft. Sometimes called Mu. Its simply relates to rotor rotational speed to air velocity (generally indicated airspeed). Obviously that is the problem in a flap in this case of outrunning the rotor or too much speed for given rotational speed. Its just an easy way of talking about that relationship then using all those words to explain it.

I ask because I am trying to find better ways to explain rotor aerodynamics and you explanation appears to me to be incomplete.

What is 8.8 degrees of incidence?

I will rephrase the second question.

Please quantify what advance ratio is too close for comfort?

I thought a two blade semi rigid rotor flapped to manage dissymmetry of lift.

Most of the events that I investigated where the rotor struck something happened in windy conditions.

How do you measure something on a rotor to a tenth of a degree in turbulence?

 

[Abid]

I ask because I am trying to find better ways to explain rotor aerodynamics and you explanation appears to me to be incomplete.

What is 8.8 degrees of incidence?

I will rephrase the second question.

Please quantify what advance ratio is too close for comfort?

I thought a two blade semi rigid rotor flapped to manage dissymmetry of lift.

Most of the events that I investigated where the rotor struck something happened in windy conditions.

How do you measure something on a rotor to a tenth of a degree in turbulence?

Look above. I added answer to your second question. This is not really that applicable to pilots. Its good but what they need to know to operate safely is summarized in manuals and procedures. They should understand general high level concept for sure and perhaps most importantly understand that the basic data in the POH is not coming out of someone's "fart" as someone posted. It actually has basis in science, measurements and has been proven to give you a very good chance of being safe. Given some standardization in a type of gyroplane a lot of this data will apply across models and be similar.

 

[Doug Riley]

Of course, as Vance is trying to teach us, gyro folk often use the word "flapping" to mean two different (although related) things. One kind of flapping is good, and the other is not good. Confusing.

The first kind of flapping is simply the normal activity of the flap hinges (in our case, usually a teetering type of flap hinge). In this flapping activity, the hub bar rotates several degrees around its hinge bolt, oscillating between a position that's square to the spindle to one that's NOT square to it as the rotor turns. This movement in-and-out of square happens in a regular cycle, twice per rotor revolution. This is what the hinge is designed to do, and it's good.

The second meaning of "flapping" is as our shorthand name for retreating-blade stall. This happens when the backward-travelling, or retreating, blade lacks enough airspeed to avoid stalling the whole blade. The other (advancing) blade has plenty of airspeed, and its lift cause the whole seesaw mechanism to teeter violently. The stalled blade can do a lot of damage in just a flash. In flight, this same condition is quite likely to be fatal.

We might avoid confusion by calling the second type "blade sailing" or some such other name. Whatever we call it, the underlying phenomenon in "flapping type 2" is retreating-blade stall.

 

[Abid]

Of course, as Vance is trying to teach us, gyro folk often use the word "flapping" to mean two different (although related) things. One kind of flapping is good, and the other is not good. Confusing.

The first kind of flapping is simply the normal activity of the flap hinges (in our case, usually a teetering type of flap hinge). In this flapping activity, the hub bar rotates several degrees around its hinge bolt, oscillating between a position that's square to the spindle to one that's NOT square to it as the rotor turns. This movement in-and-out of square happens in a regular cycle, twice per rotor revolution. This is what the hinge is designed to do, and it's good.

The second meaning of "flapping" is as our shorthand name for retreating-blade stall. This happens when the backward-travelling, or retreating, blade lacks enough airspeed to avoid stalling the whole blade. The other (advancing) blade has plenty of airspeed, and its lift cause the whole seesaw mechanism to teeter violently. The stalled blade can do a lot of damage in just a flash. In flight, this same condition is quite likely to be fatal.

We might avoid confusion by calling the second type "blade sailing" or some such other name. Whatever we call it, the underlying phenomenon in "flapping type 2" is retreating-blade stall.

Yes sorry it may be confusing certainly to new pilots. It is technically retreating blade stall. No matter what you think of your gyroplane blade to tail and prop clearance on the ground; in a retreating blade stall your blade will chop off your tail and even your prop blade tips. That can happen on any gyroplane I have ever seen so far.
Again general guideline to avoid that is to increase your rotor RPM and decrease your airspeed. On takeoff you have a pre-rotator and have certain amount of control on what rotor RPM you want to reach to start moving forward. Use it and follow guidelines in pre-rotation and takeoff procedure in your manual. In gusty wind, control your forward airspeed with throttle application and watch your RRPM to make sure they are increasing (trend). Abort takeoff if your rotor RPM simply isn't increasing and could be even decreasing. There is no design that can alleviate this problem if you don't understand that this Physics will cause you to chop your tail if you do not give yourself the operational buffer built into recommended procedures. Do your own procedure at your own risk. For each airspeed given the diameter of your rotor, there is a rotor RPM that is needed at a minimum to be safe. Fall below that rotor RPM for that airspeed and you will start this process. Recommended rotor RPM in takeoff procedure pre-rotation give you a nice big buffer. You can decide to have it in your pocket or you can decide to play closer to the edge with an empty wallet. You play stupid games, you get stupid prizes. Fly safely.

 

[Resasi]

That's why in the UK it is described as blade sail/ing, and I put... blade sail/blade flap.

This to distinguish from what the rotor blades are doing naturally in normal operation.

 

[EI-GYRO]

It is working at least in the case of AR-1.
It’s the ones not being taught the process listed in POH and thus not following the procedure who are having the accidents. Can't say its not working till you show me that people who were taught POH procedure are flapping left and right on T/O roll. That has not happened yet. Of course it will but not so far in 5 years. But I am all for hand patting static displays. Hopefully CFIs will set them up at their flight schools and hangers who believe that's the way to go.

So the screwed up takeoffs are being caused by people being taught the wrong procedure?????

I find that a stretch to believe.. They seem to me to be caused by mistakes in the application of the POH procedure rather than anything else.

 

[BEN S]

This whole thing smacks of liability laws and who is not getting blamed for what...

According to the Fara method, if in my new Jeep operating hand book it says "if about to get into an accident, apply brakes and manoeuvre accordingly so as to avoid possibly fatal contact with any other items or vehicles...failure to comply with this warning can be fatal"

See??? Now I just solved the whole mess of accidents we have had ever since cars were invented! We can now do away with Insurance, and while were at it we can probably get rid of drivers education....because we just need drivers to read and follow the manual!

But thats just horseshit....and you all know it.

 

[Burrengyro]

This whole thing smacks of liability laws and who is not getting blamed for what...

According to the Fara method, if in my new Jeep operating hand book it says "if about to get into an accident, apply brakes and manoeuvre accordingly so as to avoid possibly fatal contact with any other items or vehicles...failure to comply with this warning can be fatal"

See??? Now I just solved the whole mess of accidents we have had ever since cars were invented! We can now do away with Insurance, and while were at it we can probably get rid of drivers education....because we just need drivers to read and follow the manual!

But thats just horseshit....and you all know it.

She who knows better will say: Didn't read the manual, did you???! after I usually made the mistake of trying to fix something without reading the same manual and ended up cocking things up. She is usually right, of course.

I once tried to make a magnet using mild steel and wound a coil of wire around it. I told my father (who did not know much about electricity) about my big plan. He was very supportive. I plugged into the mains and duly blew up the main fuse board. Of course, AC current does not magnetize much. My mother who was a great believer in reading and that "knowledge is no load" drily admonished me and my father saying: you two would need to read a book or two before messing with electricity again. Our house had to be rewired after my efforts..... I also have similar experiences with Molotov cocktails, homemade grenades and other explosives without reference to a relevant manual.

My wife and my mother and women, in general, are usually right about things and men don't read manuals until after some damage has been done. But what would they know???..... Now, if I could only find the manual for my wife........

 

[Vance]

A learner won’t remember everything I tell them as a flight instructor so with time and practice I figure out how much to emphasize the different aspects of flying a gyroplane.

It is my observation that at least 30% of the gyroplane mishaps are due to rotor mismanagement.

How to describe it so people will remember is a challenge to me.

Many flight instructors forget how hard a time they had with their takeoffs at first and imagine if they keep it simple enough their learners will be able to do it by route.

It is my observation that without a clear reason to do it by the book deviation becomes the norm.

It works until one day it doesn’t.

I have found that sometimes there is a disconnect between what my mind knows and what my body does.

Blade sailing is not just for low time gyroplane pilots. I have seen many high time gyroplane pilots whack their tails with the blades.