Auto-Gyro blades

Philbennett

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I'll type things as they were recently published in the UK Light Aircraft Association magazine of Feb 2022, slightly edited for brevity ;.

For those not familiar with the UK most gyroplanes fly with the revalidation of their permits to fly done by the Light Aircraft Assoc. [LAA]. They have an engineering resource and are active in highlighting various issues they find throughout the fleet of aircraft they are responsible for.

While conducting the annual inspection on an Auto-Gyro MTOsport, LAA inspector [name withheld] discovered longitundinal cracks in the upper surface of the rotor blades from the root end hole to the second bolt hold. This was visible to the naked eye. Rotor blade inspections have always been part of the service and inspection regime for all of the factory built gyroplane fleet however in the light of an event abroad in the summer of 2021 the AutoGyro inspection has changed with the issue of SB-144 Issue 1 and the updating of the inspection schedules....
It continues with a description of that change before :-
The calculated safe service life of the Rotor System 2 blades is 2500 hours, however it has been found that the real world service life is significantly less
It continues to explain the factors as per the Cranfield study that many are familiar with and suggests that rotors may only last as little as 1600 hours and that factors such as flight cycles, touch and goes, pre-rotations and other operating regimes [such as operation on hard or grass runways] may need to be considered as well as flight hours.
 

Vance

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I'll type things as they were recently published in the UK Light Aircraft Association magazine of Feb 2022, slightly edited for brevity ;.

For those not familiar with the UK most gyroplanes fly with the revalidation of their permits to fly done by the Light Aircraft Assoc. [LAA]. They have an engineering resource and are active in highlighting various issues they find throughout the fleet of aircraft they are responsible for.


It continues with a description of that change before :-

It continues to explain the factors as per the Cranfield study that many are familiar with and suggests that rotors may only last as little as 1600 hours and that factors such as flight cycles, touch and goes, pre-rotations and other operating regimes [such as operation on hard or grass runways] may need to be considered as well as flight hours.
With my limited experience at predicting fatigue life of aluminum structures I found the amount of bending and the number of cycles were fundamental parts of predicting service life.

I hope that people don’t condemn all extruded blades systems because one system is not lasting as long as predicted.
 

Philbennett

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No I'm sure not. What I think seems very limiting however, and I wonder if or how it will ultimately be addressed, is how the ongoing service life will be judged because if the process relies upon service engineers spotting visible blade cracking which may only be apparent once some element of disassembly has been under-taken there seems to me a lot of scope for potential future in-flight failure. That becomes especially true because the increased inspections that may reveal such issues do not arise until 1500 hours.
 

Andino

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"The calculated safe service life of the Rotor System 2 blades is 2500 hours, however it has been found that the real world service life is significantly less"

I once was thinking of buying an MTOsport 2017 (or a Calidus), but didn't trust the 2,500 hours service life claim of the rotor because I was never able to locate the "university study" on their RotorSystem2. Has anybody at all ever read that document?
 

Abid

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Averso Stella extruded blades are 20 pounds heavier than AutoGyro and their life limit is less
 

Andino

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Averso Stella extruded blades are 20 pounds heavier than AutoGyro and their life limit is less
The Aversos seem to have a conservative service life determination and good safety record. I've heard of no in-flight failures, which I believe is unique to extruded blades.
 

Philbennett

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"The calculated safe service life of the Rotor System 2 blades is 2500 hours, however it has been found that the real world service life is significantly less"

I once was thinking of buying an MTOsport 2017 (or a Calidus), but didn't trust the 2,500 hours service life claim of the rotor because I was never able to locate the "university study" on their RotorSystem2. Has anybody at all ever read that document?
Cranfield RS1 study
 

Andino

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Righto, and I've read that study several times. It lead to the grounding of 700+ hours RotorSystem1 blades, and the subsequent development of RS2, correct? But where is that "university study" which AutoGyro relied upon for the 2,500 hour service life of RS2? I searched again earlier today. It cannot be found online. Strange!
 

Abid

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The Aversos seem to have a conservative service life determination and good safety record. I've heard of no in-flight failures, which I believe is unique to extruded blades.

Yes I did that research before going with Averso instead of Girabet or AirCopter etc. I guess that is because they have more metal in them. I think almost 15 to 20 pounds more
 

Philbennett

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Andino

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Thank you, Phil. I'll inquire. (AutoGyro's "university study" really should not be so mysterious, as it was the basis for the CAA's RS2 approval, correct?)
 

Philbennett

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Well you know I'm not sure who or how the CAA approve gyroplane because I'm not sure where the expertise is and I'm sure there has been an element of using outside resource as lead that provides a great paper trail and ticks some boxes but I'm not sure what the engineering rigor is behind that. If that outside resource happens to be aligned to a manufacturer then perhaps this is what you get.

What I am pretty clear upon in my own mind - and others, including the regulation can make their own minds up - is it seems to me that the fundamentals of RS1 and RS2 blade wise are similar and therefore the conclusions from the Cranfield study would apply regardless of the numeric suffix.

Of course in 2022 the number of aircraft with +1500hrs of time on the rotors is pretty small. That is partly due to the average hours flown by aircraft in private ownership, partly due to a reset of rotor hours that came where they [AutoGyro] offered a discounted RS2 for existing RS1 owners and the fact RS2 is in any event just over 10 years old and a couple of those are limited by the corona virus.

Personally I have decided not to fly in one where either I don't know the history and the hours are high [beyond 1000] and not in one at all where the operation is mainly off grass and beyond 500hrs. It may seem irrational but in the UK there is just too much unknown, untrust-worthy data/commentary and poor regulatory process for me, to mean there is far too many commercially involved that seem to have influence. That should be interesting to people globally because often the UK is a lead.
 

Andino

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Well you know I'm not sure who or how the CAA approve gyroplane because I'm not sure where the expertise is and I'm sure there has been an element of using outside resource as lead that provides a great paper trail and ticks some boxes but I'm not sure what the engineering rigor is behind that. If that outside resource happens to be aligned to a manufacturer then perhaps this is what you get.

What I am pretty clear upon in my own mind - and others, including the regulation can make their own minds up - is it seems to me that the fundamentals of RS1 and RS2 blade wise are similar and therefore the conclusions from the Cranfield study would apply regardless of the numeric suffix.

Of course in 2022 the number of aircraft with +1500hrs of time on the rotors is pretty small. That is partly due to the average hours flown by aircraft in private ownership, partly due to a reset of rotor hours that came where they [AutoGyro] offered a discounted RS2 for existing RS1 owners and the fact RS2 is in any event just over 10 years old and a couple of those are limited by the corona virus.

Personally I have decided not to fly in one where either I don't know the history and the hours are high [beyond 1000] and not in one at all where the operation is mainly off grass and beyond 500hrs. It may seem irrational but in the UK there is just too much unknown, untrust-worthy data/commentary and poor regulatory process for me, to mean there is far too many commercially involved that seem to have influence. That should be interesting to people globally because often the UK is a lead.
Phil, I am heartened to read such a frank and balanced opinion, especially from a CFI who has probably many hours in AutoGyos. Your "in the UK there is just too much unknown, untrust-worthy data/commentary and poor regulatory process for me, to mean there is far too many commercially involved that seem to have influence" is fair, and your <500 grass hours/<1000 total hours total limits seem prudent.

What got my attention years ago was AutoGyro's Service Information Letter AG-SIL-2019-03-EN concerning rotor blade inspection guidelines (pdf attached below), and its page 5 photo of a longitudinal crack at the most inboard region. (Not to mention outboard bolt hole lateral cracks, which by now are seen to appear.) I've never heard of another gyroplane manufacturer with caveats about lateral and longitudinal blade cracking.

AutoGyro RS2 longitudinal rotor blade cracking alert.png

I've attached the CAA's Airworthiness Approval Note (AAN) 29247 about the RS2. AutoGyro really should produce their "university study" calculating RS2 safe life as 2,500 hours. AG seems to have no arguable proprietary interest in withholding it. Until we can read that alleged study for ourselves, I agree that the Cranfield report should be overlayed with RS2 for sake of caution.
 

Attachments

  • AG-SIL-2019-03-B-EN Rotor Blade Inspection.pdf
    764.7 KB · Views: 15
  • 29247000000.pdf
    1.4 MB · Views: 13
  • 29247000202.pdf
    991.6 KB · Views: 10
  • 29247000300.pdf
    1.2 MB · Views: 12

Andino

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On 24 January 2022 the UK CAA issued MANDATORY PERMIT DIRECTIVE 2022-002 and AIRWORTHINESS DIRECTIVE G-2022-0001 (both attached below).

Reason:
The CAA has been advised of two different crack mechanisms that are occurring on rotor blades on
AGC gyroplanes equipped with Rotor System II.

1. Longitudinal (i.e. spanwise) cracks from the root to the second bolt hole have been found on
the top surface of rotor blades on a MTOsport equipped with Rotor System II, including the
Cavalon Pro.
Due to similarity of design, this condition may also affect other gyroplanes types from AGC with
Rotor System I or Rotor System II.

2. A crack and fretting have been found at the outer attachment bolt hole of a rotor blade of a
RotorSystem II
installed on an MTOsport gyroplane.
Due to similarity of design, this condition may also affect other gyroplanes types from AGC
equipped with Rotor System I or Rotor System II, including the Cavalon Pro.

Cracks in the rotor blades may result in loss of the blade and consequent loss of control of the
gyroplane.

This AD has been raised to check the hours of the rotor systems installed on affected gyroplanes, align
the inspection programme to the new life limits and inspection intervals, check the rotor blades for
evidence of corrosion and/or cracks and replacement as required.
 

Attachments

  • 2022-002.pdf
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  • G-2022-0001.pdf
    122.1 KB · Views: 13

MilesW

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Righto, and I've read that study several times. It lead to the grounding of 700+ hours RotorSystem1 blades, and the subsequent development of RS2, correct? But where is that "university study" which AutoGyro relied upon for the 2,500 hour service life of RS2? I searched again earlier today. It cannot be found online. Strange!


What is the betting there is no additional study, but that it is an "extrapolation" of the RS1 study taking into account their perceived improvements?
 

Andino

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What is the betting there is no additional study, but that it is an "extrapolation" of the RS1 study taking into account their perceived improvements?
Miles, quelle surprise that nobody is betting against you. "University study" my *rse. If they had real data supporting 2,500 hours of service life, they'd be quoting it far and wide. After 11 years of AutoGyro's RS2, nobody in the industry has bothered to wonder about this?
 
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