Brief flight report

I am now in Aussie-land (arrived yesterday) at my Sunshine Coast apartment "home" - for the next month .... enjoying beach-time with Jason,Shelbie & 2 delightful grand-daughters!

I brought some of the broken parts from my Colorado friend's broken machine("Tess") in my huge suitcase ...to send to Neil for re-build/refurbishment! A small start to Tess's re-build process!

I doubt this year I'll go to Canberra as I did last year ... Neil & I will mail parts back & forth ....I have a good list of spare parts that Tim Weiland & I will stock for our TAG owners to bring back when I return.

I know every US TAG owner who got to meet Neil on his personal round-the-world service check on TAG tails was super impressed with his customer-care & knowledge of gyros and his design! (This was in 2018 after the ASRA inspection of the TAG crash at Orange was concerned about his tail-keel brace attachments!).
Enjoy your time there Chris! Stay safe and get a good recharge on your Ozzy accent!

It's unlikely I will get to Australia again. R&R in 1967 and 1970 were the only time I visited, and I was an archetypical ugly American at the time. Fast forward a few decades. I'm more polished on the corners now and would love to meet the team that designed this neat aircraft.

I sure appreciate the advice and assistance you have given me Chris.

Jim
Jim,

You went there to unwind and release some steam from tours of combat. Not the best of behavior, but expected.

I totally enjoyed my time in the Land of Oz. Great and fun people to be with.

Wayne
 
Yes that is what Neil says they cost ...the pre-preg carbon fibre has gone up horrifically in recent years! If "stupid human tricks" would quit wrecking his rotors, their life expectancy is well over 5000 hours .. equal & better to that rated life of the Aussie "gold-standard" Goodman composite rotors used by many mustering machines ... (the ones that time-out Rotax 912 engines in a couple of years!)

The TAG rotor is carbon -on CARBON spar! (unlike others that put a bit of carbon& fiberglass on an Aluminum spar!)
The metal fatigue element/ life-span on ALL extruded aluminum rotors is what led Neil to look for a different rotor solution!

I agree that this may be "over-kill" for the low hours we sport-fliers put on our machines !
Remember however that Neil designed the TAG gyro FOR the Australian customers who wanted a RUGGED & DURABLE gyro suited to the rough Australian environment!
His mustering customers have really put his gyro design to the working -gyro field test , & they are more than happy to fly a "10,000 hour" rated rotor design!
What are these Goodman composite rotors?

wolfy
 
I am grateful Jim Mayfield generously offered us his experience and recognition of a potential risk.

It is my observation that Jim Mayfield has a quick mind that likely identified the risk and fast reactions that addressed it quickly noting the potential problem without having to experience it and do damage.

I have had learners not understand that the retreating blade can stall (flap) when the aircraft is stopped.

In my opinion based on my experience; retreating blade stall is about airspeed and not ground speed.

The retreating blade stalls before the advancing blade because the angle of attack is higher on the retreating blade.

In The Predator I teach the learner to have the cyclic forward any time the rotor rpm is below 100 so that a gust of wind doesn’t run the rotor into the empennage.

The cyclic may be full forward and left or right because there is nothing to hit on the sides.

In The Predator it would be difficult to hit the runway on the side.

This also gives the learner the opportunity to use the prevailing wind to slow the rotor.
 

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I am grateful Jim Mayfield generously offered us his experience and recognition of a potential risk.

It is my observation that Jim Mayfield has a quick mind that likely identified the risk and fast reactions that addressed it quickly noting the potential problem without having to experience it and do damage.

I have had learners not understand that the retreating blade can stall (flap) when the aircraft is stopped.

In my opinion based on my experience; retreating blade stall is about airspeed and not ground speed.

The retreating blade stalls before the advancing blade because the angle of attack is higher on the retreating blade.

In The Predator I teach the learner to have the cyclic forward any time the rotor rpm is below 100 so that a gust of wind doesn’t run the rotor into the empennage.

The cyclic may be full forward and left or right because there is nothing to hit on the sides.

In The Predator it would be difficult to hit the runway on the side.

This also gives the learner the opportunity to use the prevailing wind to slow the rotor.
I am still a little confused about this aspect of a blade stalling and flapping when the gyro is standing still. How is it then possibly safe to perform the old fashioned maneuver of patting the blades by hand with the stick back to get the blades started without a prerotator? Possibly then someone on the forum who is familiar with doing this can explain to me how you avoid a blade stall and flap when beginning a taxi in gyros without a prerotator and what the technique is that is used? Is the stick brought back progressiely as the gyro speeds up?
My follow up question to this is; if one were to accelerate the rotor using the prerotator with the stick back, from standstill, would I flap the blade if the gyro was not moving? (assuming here that there is no tail to worry about) And another follow up question; if the stick is not brought forward after landing, the gyro is stopped and rotor speed is simply allowed to decay and there is no tail to worry about, will the blade flap in any type of dangerous fashion? From what Vance says, this may have to do with the wind, but lets assume no wind. My overall understanding is that it would require the stick to be eased back or forward in a progressive fashion to avoid any oscillation of the blade as it speeds up or slows down.
 
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Morning Jeff,

I believe Vance is indicating that blade flap occurs with airspeed being too high with rotor rpm being too low. If you are sitting still with a 10 KT headwind there is some RRPM that will result in blade flap at some disc angle.

Even with zero RRPM, I would not want the stick fully aft because wind on the flat bottom of an aft tilted rotor could force the rotor to flap further rearward and drive the rear blade into the tail or prop if the geometry permits.

As to hand starting blades, I have only done it with Bensen, Brock, StanZ, Rotordyne, etc. All in the 22-23 foot range. The blades were not nearly as flexible (droopy) as the 27-30 foot rotors currently in use on the newer, larger machines.

Jim
 
This morning's one hour flight was to verify my feelings about the vibration improvement in my rotor system.

It is much smoother than it was before I shifted the teeter spindle .01” but not yet where I would like it to be.

I know it would be easier with a PB-4, but I did not buy one. In the old days, when Pterodactyls ruled the skies, we would use flagging to adjust track, knife edges to check span wise balance, stringing to get us close on correct blade alignment, and keeping a good record of chord wise adjustments to ensure we were not making adjustments haphazardly.

This afternoon I will make another chord wise adjustment. I had said I would make a .002-.003” adjustment but I think I will move the teeter spindle another .01” in the same direction as the last move and then fly. The vibration will get better or worse. If it gets worse, I'll move the teeter spindle back half the distance and fly it again. If it gets better, I'll decide if another move is warranted.

Unless I am looking for it, the power/yaw couple I observed in my first test flights with this aircraft have faded into the background of my consciousness. I seem to be feeding in appropriate rudder pedal pressures as necessary. It seems natural now, in the latter stages of the takeoff roll, to feed in a little left forward stick and right rudder just as liftoff occurs. The aircraft accelerates nicely to 60 KTS IAS and begins to levitate. With an OAT of 50F this morning rate of climb settled down to 800 FPM until my 500 foot pattern altitude.

It was a great morning and life continues to be good!

Jim
 
I know it would be easier with a PB-4, but I did not buy one. In the old days, when Pterodactyls ruled the skies, we would use flagging to adjust track, knife edges to check span wise balance, stringing to get us close on correct blade alignment, and keeping a good record of chord wise adjustments to ensure we were not making adjustments haphazardly.
I'll loan you mine when I finish my balancing project.

Bobby
 
I am still a little confused about this aspect of a blade stalling and flapping when the gyro is standing still. How is it then possibly safe to perform the old fashioned maneuver of patting the blades by hand with the stick back to get the blades started without a prerotator? Possibly then someone on the forum who is familiar with doing this can explain to me how you avoid a blade stall and flap when beginning a taxi in gyros without a prerotator and what the technique is that is used? Is the stick brought back progressiely as the gyro speeds up?
My follow up question to this is; if one were to accelerate the rotor using the prerotator with the stick back, from standstill, would I flap the blade if the gyro was not moving? (assuming here that there is no tail to worry about) And another follow up question; if the stick is not brought forward after landing, the gyro is stopped and rotor speed is simply allowed to decay and there is no tail to worry about, will the blade flap in any type of dangerous fashion? From what Vance says, this may have to do with the wind, but lets assume no wind. My overall understanding is that it would require the stick to be eased back or forward in a progressive fashion to avoid any oscillation of the blade as it speeds up or slows down.
Loftus

This might help.
Here is an old video that I haven't bothered to edit. It shows me flapping the rotor at very low Rrpms (<50).


You can see the flapping angle that was measured in real time on the screen of the tablet, the sun kept causing a lot of reflections that is why you see me waving my hand about trying to block the sun.

You can also see a very early prototype GWS warning light flashing when it considers that there is a risk of flapping. The system is much more sophisticated today.

By monitoring the flapping angle I was able to slowly nurse the Rrpm up to an acceptable value. I doubt if I could have done it without knowing the flapping angle but I'm sure many old timers could do it by feel.

Interesting to note that during flapping the stick tends to pulse back and forth confirming Jean Claude's theory that a flapping rotor doesn't flap from side to side.

During this test I actually touched the rotor with the prop, no damage just a mark on the rotor paint. This rotor would pass the Australian requirement. When the rotor is stationary, with the stick fully back and the rotor on the flapping stop there is plenty of clearance between the rotor and the prop and tail, yet during low speed flapping the rotor still managed to fit the prop.

Here is a screenshot of the video showing the different instrumants.
1699274313846.png

Mike G
 
Loftus

This might help.
Here is an old video that I haven't bothered to edit. It shows me flapping the rotor at very low Rrpms (<50).


You can see the flapping angle that was measured in real time on the screen of the tablet, the sun kept causing a lot of reflections that is why you see me waving my hand about trying to block the sun.

You can also see a very early prototype GWS warning light flashing when it considers that there is a risk of flapping. The system is much more sophisticated today.

By monitoring the flapping angle I was able to slowly nurse the Rrpm up to an acceptable value. I doubt if I could have done it without knowing the flapping angle but I'm sure many old timers could do it by feel.

Interesting to note that during flapping the stick tends to pulse back and forth confirming Jean Claude's theory that a flapping rotor doesn't flap from side to side.

During this test I actually touched the rotor with the prop, no damage just a mark on the rotor paint. This rotor would pass the Australian requirement. When the rotor is stationary, with the stick fully back and the rotor on the flapping stop there is plenty of clearance between the rotor and the prop and tail, yet during low speed flapping the rotor still managed to fit the prop.

Here is a screenshot of the video showing the different instrumants.
View attachment 1159732

Mike G
Thanks. Excellent video. Do you have a table of sorts of flapping angle RRPM and Wind Speed. I would assume that in zero wind then that no flapping would occur, am I correct?
 
Do you have a table of sorts of flapping angle RRPM and Wind Speed.
As long as the retreating blade has not reached stall, the flapping angle stabilizes at a low value (less than 4°). So, the stops can not to hit
But when the retreating blade reaches the stall, the flapping angle diverges and increases with each revolution. The blades will then hit their stops after a few more revolution, whatever the margins given.

So, with a rotor at 20 degrees, and pitch setting of 3 degrees , the flapping angle divergence can appears for a forward speed > 0.2 * circumferencial speed of blade tip
This means that a 24 ft rotor at 70 rrpm can hit the stops as early as forward airspeed 10 Knots.
 
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Thanks. Excellent video. Do you have a table of sorts of flapping angle RRPM and Wind Speed. I would assume that in zero wind then that no flapping would occur, am I correct?
loftus
I'm sure you already know this so perhaps I'm missing what your question is.
Flapping is due to dis-symmetry of lift, as the advancing blade sees a higher airspeed than the retreating blade. If the gyro is not moving forwards and there is no wind then there is no flapping. I theorize that perhaps there would be some as each blade past over the propeller wash.

One of the problems is that many (including me) use the word flapping to cover different things.
As pointed out by someone in another thread:
If the rotor is seeing wind because it's advancing or there is simply wind the rotor will flap due to dis-symmetry of lift. This "flapping" is normal in our rotors. As JC points out it's usually less than 4° and if you take the time to watch my video presentation of the GWS you'll see the flapping angle recorded during a flight.

If the airspeed is too high for the rotor speed (see graph below) the retreating blade stalls excessively (part of the retreating blade is always stalled even in a successful take off and light) and the rotor flaps excessively and hits the flapping stops (usually set at about 8-10° flapping angle). This is the classic "flapping accident at take-off. Some suggest (and I tend to agree) that we call this blade sailing to reduce the confusion.

There is an accident scenario that seems to be the basis of this thread that at very low Rrpms if you pull the stick fully back and the rotor happens to be at one of the flapping stops, the rotor can hit the prop, tail or even the ground. In my view this is a design issue that can (and should) be avoided.

Then we have the scenario with a very low Rrpm and with the stick fully back the rotor flaps excessively or sails (poor rotor management) and the rotor hits the prop, tail and/or ground even though, in theory, it shouldn't because it doesn't when you try it stationary on the ground. This is what happened in my video. This is probably due to the force with which the rotor hits the flapping stop taking out any clearances in the rotor head, its roll and pitch pivots plus the flexibility in the mast and control system and a lower rigidity of the blade because at low Rrpms there is insufficient centrifugal force to keep the rotor rigid.


The table you are looking for would be quite complicated because as JC points out flapping angle is dependent upon so many variables such as rotor diameter, TAS (so DA), chord, pitch setting, aerofoil profile, stick/rotor disc angle and Rrpm (which depends upon AUW.
Also as discussed on the GWS thread, knowing the flapping angle is of little to no value to the pilot

JC has given you one approach to your request, I would offer the graph I posted in another thread.

1699364975439.png

This one shows a typical pre rotation (with about 15 kph headwind) and take-off.

I hope this helps.

Mike
 
I love how deeply you have gotten into this important discipline Mike G and your willingness and patience to share the details of what you have learned in an elegant way.

Thank you.
 
I love how deeply you have gotten into this important discipline Mike G and your willingness and patience to share the details of what you have learned in an elegant way.

Thank you.
Thank you Vance, how is the GWS installation progressing? Do you need any more help?
Mike
 
That is a great post Mike.

An additional comment to go along with your post, that may possibly help people comprehend, why blade/tail/airframe/gound contact occurs at this stage, is that our rotors are long thin wings that possess quite a lot of flexibility at rest...or at slower rotor rpms.

This flexibility decreases as rotor rpm's increase/high and centrifugal/centripetal forces increase blade rigidity, allowing a better clearance to be maintained the greater the rotor rpm when the stops are just being hit.

As another afterthought, I was given a short sharp reminder one day, when having hand started my blades ( Rotor- Hawkes) a mild mannered rotor, on a very windy day, with the stick full forward, I took my seat, fastened the harness, and then before I had even started moving inadvertently brought the stick back... just a little...when to my surprise and consternation I immediately began blade flap/blade sail with the stick starting a rapid side to side, with the knocking sound as the rotor began hitting the stops.

I was low on experience, but loved windy days and the fun that could be had, and on this day the winds were at least 23/24Kts with gusts. I had, with a very slight increase in disc angle of attack, exceeded the amount of air the rotor could handle for the rpm I had managed to achieve with my hand patting.

Having been used to lower wind speeds it normally took moving off then slowly milking in a little more air to increase my RRPM, here was a good example that I could encounter blade flap while standing still, due to the wind conditions on that day.

I did actually go on to fly, having rectified the blade flap/sail. I moved the gyro to the lee side of the hanger to get the rotors spun up, and a friend of mine very kindly took some video on her phone on that day and gave it to me later.

 
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Thank you Vance, how is the GWS installation progressing? Do you need any more help?
Mike
I am embarrassed by how long it is taking me particularly after Chris did so much so quickly.

I keep finding excuses to procrastinate despite my desire to complete the installation and reap the benefits with my learners.

The more I learned about your GWS the more impressed I am with what you have done.

I love when it reminds me I am behind the power curve making a power on landing and I don’t know how it knows that since the cyclic and throttle switches are not mounted.

I have not been successful at finding a block of time to finish the installation.

My rotor tachometer has stopped working and I need to get to the bottom of that before I can give instruction.

If there is a way to have Chris finish up mounting the two switches that would be a great help.

I have tried to find someone local without success.

Moving continues to suck time from my life.
 
Loftus

This might help.
Here is an old video that I haven't bothered to edit. It shows me flapping the rotor at very low Rrpms (<50).


You can see the flapping angle that was measured in real time on the screen of the tablet, the sun kept causing a lot of reflections that is why you see me waving my hand about trying to block the sun.

You can also see a very early prototype GWS warning light flashing when it considers that there is a risk of flapping. The system is much more sophisticated today.

By monitoring the flapping angle I was able to slowly nurse the Rrpm up to an acceptable value. I doubt if I could have done it without knowing the flapping angle but I'm sure many old timers could do it by feel.

Interesting to note that during flapping the stick tends to pulse back and forth confirming Jean Claude's theory that a flapping rotor doesn't flap from side to side.

During this test I actually touched the rotor with the prop, no damage just a mark on the rotor paint. This rotor would pass the Australian requirement. When the rotor is stationary, with the stick fully back and the rotor on the flapping stop there is plenty of clearance between the rotor and the prop and tail, yet during low speed flapping the rotor still managed to fit the prop.

Here is a screenshot of the video showing the different instrumants.
View attachment 1159732

Mike G
I uploaded this video to YouTube for this thread thinking that it would be interesting for members who were still not sure about blade flapping/sailing at very low Rrpms and it complimented the subject.
YouTube allows you to see how many people watched you video and how long they stayed with it.
The results are interesting and I'm not sure what to conclude from them.
1700400874076.png

First, it only got 25 views, which could show that there is very little interest in the subject unless only about 25 guys are actually following the thread. It could also mean that we only have about 25 guys who are really active on the forum.

This is a 6:42 minute video (so not too long) and 50% of viewers dropped out after 1:45 minutes, suggesting it wasn't very interesting.

Only 21% of viewers actually got to the end, most having dropped out after 3 minutes.

It makes me wonder about how to justify the effort in searching for this old video on old hard drives and the time it took to upload it to YT on my slow server.

Mike G
 
Hi Mike,

It's hard to generate a cost/benefit analysis on an endeavor like yours. It would appear to me that "someone" has been saved from damage, or even death, by your system. Even if it is only "one" that "one" should be important to all of us.

I hope you decide to continue your efforts to educate us on the advantages of the GWS. Probably a reason you do this work is because it is the right thing to do. I appreciate your efforts.

Jim
 
Mike,
Something like this is quite esoteric for the general population, but absolutely does not detract from the importance of what you have done for the gyro community. For me flapping / blade sailing or whatever one chooses to call it is one of those things in aviation like stalling; we should train ourselves to avoid coming anywhere close to these potentially disastrous events.
 
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