Fatal - Cavalon G-CKYT, Scotland, UK 12 NOV 2020

Abid

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I had an interesting discussion this weekend with a dealer rep, comparing a Magni M24 design to the Cavalon design which may reflect a little on the high rate of Cavalon accidents, particularly for low time pilots. The tail of the Cavalon sits significantly higher than the M24 due to the shape of the tail boom. This may result in the empenage being shielded from the airflow by the body of the aircraft to a greater degree in the Cavalon, which may result in less directional control particularly at low power on landing etc in the Cavalon. Of course add to that the nose wheel design differences possibly making for a less controllable aircraft close to the ground. I'd be interested to hear the thoughts of any folks that have flown both aircraft.

A side by side gyro with the tail literally less than 5 feet behind its big fat wide body is going to put the tail hidden from clean air. The farther back you are the more likely air will have a chance to get cleaner but neither gyro has that going on. The tail in both is of course more effective with some power on as prop is producing its own localized relative wind for the tail.
I have not flown the Cavalon yet but I did fly the M24. M24 and Magni gyroplanes in general have very thin airfoils for vertical stabilizer. Its easy enough to see. We all know that thicker curved airfoils produce more pressure and are more effective. M24 was happy flying in a slip for over a mile when I flew it without any tendency to come back unless I deliberately made it. It could use a yaw indicator.
 

Abid

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Fara, Rotor RPM being caused to/allowed to slow down... when rotors are at slower rpm they lack the rigidity they possess at high RPM's due to centrifugal/centripetal force. Soft floppy rotors (a gyros wings) flex and can start impacting fuselage or tail structure with almost always destruction of components/rotor and the consequent fatal results.

Wings on an aircraft retain their design rigidity and strength, unless compromised through some form of structural failure or exceedence of design limitations, speed/ turbulence /gross weight.

A fixed wing pilot is not faced with his wings going soft because he slows down or starts getting negative G.

Hmm ... hold on. If your wings in flight have gone soft, you have done a fatal mistake and there is no returning from that. That is like saying if you got yourself in a flat spin at 600 feet how would you recover from that. You won't. Its a fatal mistake. Going into such mistakes means you executed a maneuver to put the aircraft out of its safe flight envelope.
I do not know of anything that goes up in the air that cannot be put in a situation where it would not lose its wings or flying surface or power. They all can be. In that sense flight is more dangerous than being on the ground and if one cannot accept that risk, train adequately to manage and reduce that risk and respects the flight envelope, one should not be flying.

Yes you can execute maneuvers in rotorcraft that can take their rotors limp and you can stall, and spin airplanes right into the ground. Both will likely kill. You can additionally have things like ground resonance and blade flapping in rotorcraft and you can ground loop taildragger airplanes on the ground. You can additionally takeoff behind the power curve in a gyroplane and you can stall an airplane with a departure stall.

I do not see how its better or worse. What I see is lack of enough training. Overconfidence by people coming in from other categories of aircraft, easy go instructors sometimes who are being pressured (honestly idiotically) by customers wanting to fly gyroplanes and lack of and low availability of instructors for gyroplanes

And as an aside lack of good insurance for instructors. Lack of a serious body that promotes and looks after this category of aircraft. Accidents in LSA and in gyroplanes are higher than GA. Yes they are. Now take a look at the average age of a newcomer to gyroplanes and LSA compared to GA and you will see beyond simple numbers and realize unless that average age of the newcomer to these categories does not reduce significantly, the accident rate will also not significantly reduce. The insurance companies are fairly smart and have the data. There is a reason why aviation underwriters do not insure even in GA anyone new that is above 70 or 75 years old.
 
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WaspAir

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I do see better and worse.

If you had been on this forum long ago, you would have seen plenty of attempted justification for retaining serious design flaws offered by people who were quick to say that training was the better answer. It's an unpleasant history. Perhaps you didn't mean to echo that, but it brings back the shadow of an ugly time.
 

Abid

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I do see better and worse.

If you had been on this forum long ago, you would have seen plenty of attempted justification for retaining serious design flaws offered by people who were quick to say that training was the better answer. It's an unpleasant history. Perhaps you didn't mean to echo that, but it brings back the shadow of an ugly time.

Well I am not advocating high thrust line with no HS for instance or too short coupled main wheels versus front tire with a geometry that encourages darting off to the side. That is not what I mean. But I don't think rotorcraft blades being flexible at low RPM is a serious design flaw. Of course they are flexible. Part of our training is to handle that.
The very first AR-1 (S/N: 1) is not found on US register. Its because it went to China. Just as it got there, within 10 days I had a message that the owner had discovered a serious "design flaw". I asked for details. He said that our blades can touch the tail. I asked for further details about what happened. The answer I got was that he assembled the gyro out of the container, put the rotor blades on. Ran the engine and then applied brakes and stopped and pulled the stick all the way back and started pre-rotating and it chopped his tail off and also hit his prop and we needed to fix it under warranty because of bad design.
I resent him the POH and some videos of many of the other gyroplane models starting pre-rotation with stick forward. After seeing those, he then asked how much to fix all the things he had broken. I gave him a quote and never heard back. AR-1 s/n: 0001 RIP. Or most likely it sacrificed itself to reverse engineering in some shop in China. Who knows.
I sure hope you don't think rotor blades being flexible when at rest or low rotor RPM is a design flaw in rotorcraft. They would all be grounded. It is indeed a matter of training.

ASRA has this rule where with stick all the way back with blade hitting the teeter stop, the blade should not touch the tail. May be ASRA talked to that Chinese customer because even if it does not touch it at rest; in a rotor flap you would need to clear it by 24 inches to save the rotor from touching the tail. Training and knowledge is mandatory and sometimes we do have to expect people to just get their head on right and gain some knowledge and training before deciding they can fly something.
 
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Vance

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I know who you are talking about. Just remember we are all prone to paralysis through analysis sometimes and that happens and we can step back, clear the junk out of our heads and next time arrive to things much more clearly. 2 bladed fixed pitch teetering rotor is as simple as it gets. There is no dark magic going on that some would have you believe. Its a wing that is rotating
When I teach rotor aerodynamics to FAA standards I simplify rotor aerodynamics to the level required.

We were trying to understand, quantify and illustrate the airflow patterns at various stations along the length of the rotor on a higher level than what is in The Rotorcraft Flying Handbook.

I am not an educated man. I do have a lot of experience operating a gyroplane rotor.

My friend has a Masters of Science in Aerospace Engineering, MSAE, Georgia Institute of Technology, 1988, Rotary Wing Flight Mechanics /Aerodynamics. He is also a military trained rotorcraft test pilot.

Neither of us felt a fixed pitch two blade semi rigid rotor was simple.
 

Abid

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When I teach rotor aerodynamics to FAA standards I simplify rotor aerodynamics to the level required.

We were trying to understand, quantify and illustrate the airflow patterns at various stations along the length of the rotor on a higher level than what is in The Rotorcraft Flying Handbook.

I am not an educated man. I do have a lot of experience operating a gyroplane rotor.

My friend has a Masters of Science in Aerospace Engineering, MSAE, Georgia Institute of Technology, 1988, Rotary Wing Flight Mechanics /Aerodynamics. He is also a military trained rotorcraft test pilot.

Neither of us felt a fixed pitch two blade semi rigid rotor was simple.
It is the simplest rotor there is. He studied stuff that was a lot more complex and if he could study those fixed pitch 2 blade central flapping hinge is simple by comparison.
 

Resasi

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Hmm ... hold on.

Yup holding on... and just for a little background on why I say what I have said.

First job in aviation was as a fixed wing instructor at Burnside-Ott Aviation Training Academy at Opa-Locka Florida. Dug the log books out just to check figures. At the time the largest Civilian Flight School in the US.

Went on the 26th June 1969, with a UK PPL and 139 hrs to get my US Commercial Instrument and Multi ratings.
Did the commercial and twin check rides on the same day with the FAA, not the school designee, on the 2nd August 1969 at 212hrs.
Went on with Instrument rating, completed on 11th Sept 1969 at 240 hrs TT.

My Instructor then talked me into doing the Instructor rating. Check ride passed with FAA 22nd Oct 1969 at 290 hrs.
Then running out of money but Chief Instructor offered me a loan to do the Instrument Instructor with the offer of a job with the school if I did, and to comply with Immigration regs had to sign on to do the ATP. So began the Instrument Instructor.

At that time had also done a basic aerobatic course with a small school on the field called Taildraggers. The owner asked if I could do some Instruction for him with a Young Eagles program he had with a local boys military academy/school, so began that together with some basic aerobatic training, while doing the double I at Burnside.

Instrument Instructor check-ride with FAA 16th Jan 1970 at 435hrs. Then began full time Instruction with Burnside on the 20th Jan after some checks with the school's Chief Instructor.

First students were started at 06:30 with T.O at 0700 times were TO to Touchdown and did not include taxi time. with around 4 to 5 students a day, every day, two evenings a week until 10:00pm for night flying. And every weekend either a Sat or a Sun. at the school.

School had around 90 Cessna 150's, 25 172's, 5 Twin Comanches, 5 Lake Amphibians, 1 Cessna 310, 2 Beech 18's, 3 DC3's.
The airfield at that time had around 3,000 movements a day and was a regular Coast Guard base, and had excess jets based there.
Taught on all types except the Beech 18 and DC3, that included types that some student came to the school with.
Finally met the requirements for the ATP and had to take that on 14th June 1971 and at that time had 2188 hrsTT and had taught over 200 students on various course types and ratings. It was a very intensive time and certainly gave me a massive insight into student behaviour and in the development of my own flying education.

I continued to instruct in the various airline and executive jobs I have done since then, and studied as an assistant gyro instructor after getting my gyro PPL simply to help out with our group, but have not continued with that as we dispersed when we lost the use of RAF Little Rissington, I don't have a two seat gyro, or the financial incentive, and am retired. I have flown many fixed wing types, and a number of gyro types including the AR1 with Greg. Academically pretty simple, but a lot of practical flying and instructional experience on many types of fixed wing and gyro so I am perhaps slightly aware of the differences that I speak of, always acknowledging my very low time on gyros.

I have personally known 5 pilots who have lost their lives in gyros in my 10 or so years in gyros, about 2 who lost they lives in the 50+ years of fixed wing. In my very limited time with single seat gyro instruction I have been acutely aware of when to release pilots to go solo. In my fixed wing days my average students would solo between 6-8 hrs, very much longer with the few that I have taken to a solo stage in gyros. There is much more involved with simply taking a gyro off than a fixed wing, and I have never believed in by the numbers, monkey see monkey do, type instruction.

By the way how many types of single seat gyros have you flown?

You have made excellent points with starting age, not many young, too many old farts (like me) with high FW time and zero rotary/gyro. Possibly with Instructors giving in to pressure, which does certainly skew the statistics. But having had my say...still acknowledge the massive amount that I do not know and always ready to listen to what you have to say.
 
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Abid

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Yup holding on... and just for a little background on why I say what I have said.

First job in aviation was as a fixed wing instructor at Burnside-Ott Aviation Training Academy at Opa-Locka Florida. Dug the log books out just to check figures. At the time the largest Civilian Flight School in the US.

Went on the 26th June 1969, with a UK PPL and 139 hrs to get my US Commercial Instrument and Multi ratings.
Did the commercial and twin check rides on the same day with the FAA, not the school designee, on the 2nd August 1969 at 212hrs.
Went on with Instrument rating, completed on 11th Sept 1969 at 240 hrs TT.

My Instructor then talked me into doing the Instructor rating. Check ride passed with FAA 22nd Oct 1969 at 290 hrs.
Then running out of money but Chief Instructor offered me a loan to do the Instrument Instructor with the offer of a job with the school if I did, and to comply with Immigration regs had to sign on to do the ATP. So began the Instrument Instructor.

At that time had also done a basic aerobatic course with a small school on the field called Taildraggers. The owner asked if I could do some Instruction for him with a Young Eagles program he had with a local boys military academy/school, so began that together with some basic aerobatic training, while doing the double I at Burnside.

Instrument Instructor check-ride with FAA 16th Jan 1970 at 435hrs. Then began full time Instruction with Burnside on the 20th Jan after some checks with the school's Chief Instructor.

First students were started at 06:30 with T.O at 0700 times were TO to Touchdown and did not include taxi time. with around 4 to 5 students a day, every day, two evenings a week until 10:00pm for night flying. And every weekend either a Sat or a Sun. at the school.

School had around 90 Cessna 150's, 25 172's, 5 Twin Comanches, 5 Lake Amphibians, 1 Cessna 310, 2 Beech 18's, 3 DC3's.
The airfield at that time had around 3,000 movements a day and was a regular Coast Guard base, and had excess jets based there.
Taught on all types except the Beech 18 and DC3, that included types that some student came to the school with.
Finally met the requirements for the ATP and had to take that on 14th June 1971 and at that time had 2188 hrsTT and had taught over 200 students on various course types and ratings. It was a very intensive time and certainly gave me a massive insight into student behaviour and in the development of my own flying education.

I continued to instruct in the various airline and executive jobs I have done since then, and studied as an assistant gyro instructor after getting my gyro PPL simply to help out with our group, but have not continued with that as we dispersed when we lost the use of RAF Little Rissington, I don't have a two seat gyro, or the financial incentive, and am retired. I have flown many fixed wing types, and a number of gyro types including the AR1 with Greg. Academically pretty simple, but a lot of practical flying and instructional experience on many types of fixed wing and gyro so I am perhaps slightly aware of the differences that I speak of, always acknowledging my very low time on gyros.

I have personally known 5 pilots who have lost their lives in gyros in my 10 or so years in gyros, about 2 who lost they lives in the 50+ years of fixed wing. In my very limited time with single seat gyro instruction I have been acutely aware of when to release pilots to go solo. In my fixed wing days my average students would solo between 6-8 hrs, very much longer with the few that I have taken to a solo stage in gyros. There is much more involved with simply taking a gyro off than a fixed wing, and I have never believed in by the numbers, monkey see monkey do, type instruction.

By the way how many types of single seat gyros have you flown?

You have made excellent points with starting age, not many young, too many old farts (like me) with high FW time and zero rotary/gyro. Possibly with Instructors giving in to pressure, which does certainly skew the statistics. But having had my say...still acknowledge the massive amount that I do not know and always ready to listen to what you have to say.

Not sure what the point of listing all that personal experience was honestly in this context. I appreciate your personal flying experience but I am not getting your point of listing it all out here specifically.

I know 13 fixed wing pilots right here in Tampa Bay who have died in my 16 years of flying. What does that mean? Absolutely nothing as far as I can tell. One just went down in the water today here in Tampa and was thankfully saved. This has nothing to do with a logical point(s). Rotorcraft having limp wings when the rotor RPM is slow where fixed wings have fixed rigid wings and thus they are different and require different training.

I have flown zero hours in single seat gyroplanes and I have no desire to fly them either so far. The older single seat ones I would not touch with a 20 foot pole. Yes I have heard they are so maneuverable. If I wanted to do aerobatics I'd fly an airplane and I do. But again what does that have to do with any points you or me were making.

I am simply saying that rotorcraft have to be handled like rotorcraft. Trikes like trikes and airplanes like airplanes. Trying to fly one like the other and we shall not see very good results. That point is as simple and plain as it can be. My thousands of hours in trikes did not do jack for me hands on in gyroplanes and they won't for anyone else either.
 
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Resasi

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Listed simply to give some idea of experience and background, specifically in the instruction of students in flying.

The point I tried to make, and will try to make again, is my belief that student/low time pilots flying fixed wings providing lift, have less variables to cope with than student/low time pilots managing autogyro rotors. This based upon my experience of instructing ab initio pilots in either type...and further to that, I believe a large percentage of gyro accidents is due directly to the mismanagement of rotors.

Throw in perhaps, comparisons of accidents per 10,000hrs of say, gyros, flex wings, gliders, light sport fixed wings, and a picture may emerge.
 
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Philbennett

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We have talked the safety of gyros around a few times and whilst it never seems to lead to much agreement it is fact that a fixed wing aircraft is able to fly through use of a structure whilst rotary wing aircraft through use of a mechanism and a structure is inherently safer than a mechanism. However as it relates to this accident you can pull the aerofoils off either if you exceed limitations, if limits are exceeded by a second solo student personally it falls into the same bucket as hitting the boundary fence, running out of fuel, VFR flight into IMC, etc. Sorry I mean a visual flight rules flight into instrument meteorological conditions for the non English speakers....[relax in the UK its called banter!]
 

Vance

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We have talked the safety of gyros around a few times and whilst it never seems to lead to much agreement it is fact that a fixed wing aircraft is able to fly through use of a structure whilst rotary wing aircraft through use of a mechanism and a structure is inherently safer than a mechanism. However as it relates to this accident you can pull the aerofoils off either if you exceed limitations, if limits are exceeded by a second solo student personally it falls into the same bucket as hitting the boundary fence, running out of fuel, VFR flight into IMC, etc. Sorry I mean a visual flight rules flight into instrument meteorological conditions for the non English speakers....[relax in the UK its called banter!]
What limitations did the accident pilot exceed?
 

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We can all read the exact wording when the AAIB release their final report but for the avoidance of doubt with the "investigation focused on understanding the circumstances which led to the rotor head separating in flight", a year passing and those engaged with the AAIB so far on the engineering side saying that there is no evidence of the failure caused by some inherent design or structural defect and that it seemed that it failed due to overloading if you don't like my wording around limitations what wording would suit you?
 

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What maneuver does the engineering side of the AAIB (or anyone) suggest could cause an overload high enough to separate the rotor head from the rest of the gyro?
Mike G
 

Philbennett

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The Cavalon POH suggests:-
CAUTION This gyroplane has been designed and tested for a safe design load of 3.5g at maximum take-off weight 500kg / 3.0g at maximum take-off weight 560kg. Note that flying at high speeds in turbulent air, especially in combination with aggressive manoeuvres or a steep turn, can easily create high loads on the aircraft.
Demonstrated Structural Load Factors
Demonstrated positive load factor (500 kg)............................................. + 3.5 g
Demonstrated negative load factor (500 kg) – structural limit...................... - 1 g
Demonstrated positive load factor (560 kg)............................................. + 3.0 g
Demonstrated negative load factor (560 kg) – structural limit................... - 0.5 g
Important note: the indication of a demonstrated negative load factor represents a structural limit only. In flight, the limitations (see 2.9) have to be respected at all times.

Not sure the weight of the aircraft at the time but I suspect that it was towards the high end given the process most go through when sending students solo. Sustained positive g at those values is I agree a challenge although a peak g with an aggressive pull not really [decent at Vne or beyond and pull up, spiral dive] and think we likely agree the negative g limit is not a challenge.
 

Abid

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What maneuver does the engineering side of the AAIB (or anyone) suggest could cause an overload high enough to separate the rotor head from the rest of the gyro?
Mike G

Yeah that was my question as well. That demonstrated positive G load factor is from analysis and ground testing for structural loads
 

Tyger

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Not sure the weight of the aircraft at the time but I suspect that it was towards the high end given the process most go through when sending students solo.
Can you explain the above a bit better?

I am trying to imagine what kind of screw up might have led to more than 3Gs occuring, for a student on his second solo?
What makes them suspect it was a G overload vs some mechanical failure?
 

Abid

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So we saying that the +3 -0.5 number is not a limit?

No. But would love to know which maneuver they think got the student one up there specially if they mean positive loading.
Are they talking talking about the rotorhead separating in negative G load??
 

JETLAG03

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Curious, what is the load limit of an 8.8 bolt? If that is where the separation occurred.
 

Philbennett

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I can hear everyone and we are in danger of shooting the messenger. What I personally am saying you can read for yourselves above and to re-state on the basis the thinking thus far is that it didn't fail because of defects [and that is re-enforced by the lack of any airworthiness release in over a year since] that comes from two sources - one from the factory, the other an engineering resource in the UK - both have been part of the conversation with the AAIB. If that thinking has changed recently [since October?] then I haven't seen any caution over the use of Cavalon.

What could cause the rotor to separate? -ve load would likely mean contact with the aircraft; +ve load I don't know what analysis has been done that demonstrates what happens beyond +3/+3.5g and the associated rotor rpm's but its a limit and for a reason.
 
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