Vne limit on CH 640

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by geosnooker2000, Jul 4, 2019.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Jul 5, 2019 #21

    MadRocketScientist

    MadRocketScientist

    MadRocketScientist

    Well-Known Member

    Joined:
    May 17, 2009
    Messages:
    1,436
    Likes Received:
    894
    Location:
    Canterbury, New Zealand, Earth, Milky Way Galaxy.
    They also made a mess of the CriCri kits when they did them and made changes that caused flutter on those too! Killed at least one pilot. They don't like to talk about that much and pretend it never happened.
     
  2. Jul 5, 2019 #22

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,699
    Likes Received:
    1,765
    Location:
    North Carolina
    Is that related to Colomban designs not being avaialbe in the USA now?
     
  3. Jul 6, 2019 #23

    MadRocketScientist

    MadRocketScientist

    MadRocketScientist

    Well-Known Member

    Joined:
    May 17, 2009
    Messages:
    1,436
    Likes Received:
    894
    Location:
    Canterbury, New Zealand, Earth, Milky Way Galaxy.
    You hit the nail on the head...
     
    flyinut likes this.
  4. Jul 6, 2019 #24

    MadProfessor8138

    MadProfessor8138

    MadProfessor8138

    Well-Known Member

    Joined:
    Nov 4, 2015
    Messages:
    556
    Likes Received:
    231
    Location:
    Ekron,Kentucky
    It's my understanding that he will not sell to anyone in North America....PERIOD,DONT EVEN ASK !!!
    Even though he had nothing to do with the design that killed the pilot,he was pulled into court and blamed for the incident.
    He spent much time and money defending himself over an issue that someone else created by POORLY copying his design,without his permission.
    Can't blame the man for having a resentment over the whole situation.

    Kevin
     
  5. Jul 6, 2019 #25

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,699
    Likes Received:
    1,765
    Location:
    North Carolina
    This explains why I've never been able to find out why the Cri-Cri design was accused of being to blame. It wasn't...
    You need to google Zenair Cricket, not Colomban Cri-cri.
     
  6. Jul 6, 2019 #26

    MadProfessor8138

    MadProfessor8138

    MadProfessor8138

    Well-Known Member

    Joined:
    Nov 4, 2015
    Messages:
    556
    Likes Received:
    231
    Location:
    Ekron,Kentucky
    That's right....they are 2 different designs.
    The Cri Cri was not the plane that killed the pilot....the Zenair Cricket did.
    But Mr.Colomban was pulled into court and sued over the issue that he had nothing to do with..
    He spent huge amounts of time and money to clear himself of something that he had NO AFFILIATION WITH !!!
    His design was copied,correction,his design was POORLY copied by Zenair without his permission and he got the short end of the stick out of the deal.
    Zenair prett much walked away unscathed because of the attention on Mr.Colomban.
    I can totally understand why the man will not sell to anyone in North America......would you ?

    Kevin
     
  7. Jul 6, 2019 #27

    Vigilant1

    Vigilant1

    Vigilant1

    Well-Known Member HBA Supporter

    Joined:
    Jan 24, 2011
    Messages:
    3,888
    Likes Received:
    1,713
    Location:
    US
    I hadn't heard this story, thanks.
    The account at this link (http://all-aero.com/index.php?optio...ban-mc10--mc12--mc15-cri-cri-cricket&catid=59) indicates that M. Colomban and Zenair had a business relationship, and that Zenair's use of the design was authorized (which would be consistent with the similarity of name, Zenair's use of the designation "MC12", etc) Reportedly, Zenair's use a steel torque tube ( rather than the CriCri's aluminum one) caused the trouble. I'm sure the modification was a major issue in the trial.
     
    Last edited: Jul 6, 2019
  8. Jul 6, 2019 #28

    geosnooker2000

    geosnooker2000

    geosnooker2000

    Well-Known Member

    Joined:
    Mar 30, 2019
    Messages:
    100
    Likes Received:
    10
    Location:
    Somerville, TN
    I wonder... was it really a steel tube, or was it a steel bar. Steel tubes are not known for their "tortional flexibilty".
     
  9. Jul 6, 2019 #29

    MadProfessor8138

    MadProfessor8138

    MadProfessor8138

    Well-Known Member

    Joined:
    Nov 4, 2015
    Messages:
    556
    Likes Received:
    231
    Location:
    Ekron,Kentucky
    From what I remember ....from way back when....
    Yes,he had a business relationship with Zenair but things started to go south after they started making changes to his design that weren't approved by him,and other issues I believe.
    If my memory is correct,he walked away from Zenair but they continued on with their business plan anyways.
    He was gone well before the incident happened but was pulled into court anyways.

    That was a long time ago and my memory could be foggy but I believe I still have an article from the U.S. Aviator magazine laying the whole situation out.

    Kevin
     
  10. Jul 6, 2019 #30

    rdj

    rdj

    rdj

    Well-Known Member

    Joined:
    Sep 10, 2009
    Messages:
    288
    Likes Received:
    185
    Location:
    Northern California
    Unlike Part 23 certificated planes, every homebuilt is unique, hence why Vne is 'subjective'. However, most kitplane manufacturers give Vc, and from FAR 23.335 you can get the minimum recommended Vd:
    Normal: 1.40 * Vc
    Utility: 1.50 * Vc
    Aerobatic: 1.55 * Vc

    These should be good numbers for a properly designed experimental (naturally, no guarantees though). With a minimum Vd, use FAR 23.1505 to establish Vne as 0.9 * Vd.

    That's a good first approximation as to what you should CAREFULLY demonstrate during flight testing by actually diving your uniquely-built experimental aircraft to Vd and looking around to make sure nothing has fallen off. Vne is measured in TAS because the flutter considerations are related to the true speed of the air molecules over the surfaces.

    Quick example: Vc for the Zenith 650 is 108 kts or 124mph. Multiply by 1.4 and you get 174mph. Multiply by 0.9 and Vne calculates to around 156mph. For comparison, Zenith lists 160mph as Vne for the 650 on their spec page:
    http://www.zenithair.net/specs-ch650/

    Note that the spec page shows that at 75% cruise at 8000 feet (about the most you can pull from a non-turbo IC engine at full throttle) you get 160mph TAS, which is right at Vne. In practice that's not a problem, because those numbers--like most experimental aircraft numbers--are "optimistic", and realistic non-firewalled non-fuel-guzzling cruise numbers aren't that high at 8000 feet. However, put a turbocharged Rotax 915 and a variable-pitch prop in a Zenith 650 and fly it up to 15000 feet, and I wouldn't be surprised at all if the wings fell off the first time you hit a bump. That's not the fault of the plane or the designer, but the fool who is trying to fly a faster and higher mission than the plane was designed for.
     
    geosnooker2000 and mcrae0104 like this.
  11. Jul 6, 2019 #31

    MadRocketScientist

    MadRocketScientist

    MadRocketScientist

    Well-Known Member

    Joined:
    May 17, 2009
    Messages:
    1,436
    Likes Received:
    894
    Location:
    Canterbury, New Zealand, Earth, Milky Way Galaxy.
    The plans item is a 32mm diameter, 1mm wall thickness, 2024 aluminium tube which was substituted with a 4130 tube, size looks like 3/4".
     
  12. Jul 6, 2019 #32

    geosnooker2000

    geosnooker2000

    geosnooker2000

    Well-Known Member

    Joined:
    Mar 30, 2019
    Messages:
    100
    Likes Received:
    10
    Location:
    Somerville, TN
    How long was the tube in question (roughly in inches or feet)?
     
  13. Jul 6, 2019 #33

    MadRocketScientist

    MadRocketScientist

    MadRocketScientist

    Well-Known Member

    Joined:
    May 17, 2009
    Messages:
    1,436
    Likes Received:
    894
    Location:
    Canterbury, New Zealand, Earth, Milky Way Galaxy.
    Last edited: Jul 6, 2019
    pictsidhe and BJC like this.
  14. Jul 6, 2019 #34

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,699
    Likes Received:
    1,765
    Location:
    North Carolina
    This thread has turned me off the Heintz designs...
     
    bmcj and dragon2knight like this.
  15. Jul 6, 2019 #35

    BJC

    BJC

    BJC

    Well-Known Member

    Joined:
    Oct 7, 2013
    Messages:
    9,493
    Likes Received:
    6,251
    Location:
    97FL, Florida, USA
    The early Heintz designs were (my description) intended to be flown low and slow from farm land or open prairies, using minimum cost components such as wheelbarrow wheels and cheap VW engines. The were, by comparison to contemporary HBA, crude.

    The designs may have been extrapolated too far.


    BJC
     
    wsimpso1 likes this.
  16. Jul 7, 2019 #36

    BJC

    BJC

    BJC

    Well-Known Member

    Joined:
    Oct 7, 2013
    Messages:
    9,493
    Likes Received:
    6,251
    Location:
    97FL, Florida, USA
    mcrae0104 likes this.
  17. Jul 8, 2019 #37

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,529
    Likes Received:
    3,228
    Location:
    Memphis, TN
    There goes the memory. Nice how that is the wrong Comanche in that picture.
     
  18. Jul 8, 2019 #38

    BJC

    BJC

    BJC

    Well-Known Member

    Joined:
    Oct 7, 2013
    Messages:
    9,493
    Likes Received:
    6,251
    Location:
    97FL, Florida, USA
    It’s not clear to me if the NASA link is referring to the same flutter test flight as shown in the video, especially since the NASA article has a photo of a different airplane.


    BJC
     
  19. Jul 8, 2019 #39

    christos

    christos

    christos

    Active Member

    Joined:
    Nov 9, 2018
    Messages:
    39
    Likes Received:
    12
    Location:
    Greece
    The flutter is a dynamic response problem. Flutter is a dynamic instability occurring in flight, at a speed called flutter speed.
    You need an excellent aerodynamic and structural analysis background if you want to solve it. Stiffness of a wing is a wing geometry's and material's equation. So you can improve it without weight increase.
    Flutter speed is an equation of weather conditions, fuel (in wings) and many others.
    You need a really good boundary layer simulation to simulate it.


    There is a lot of small aircraft without flutter analysis in their designs but these are fly without any problem because of these are quite stiff. Off course they make this stage of design in a sailplane's or a high-speed aircraft's case etc.
     
  20. Jul 8, 2019 #40

    wsimpso1

    wsimpso1

    wsimpso1

    Well-Known Member

    Joined:
    Oct 19, 2003
    Messages:
    5,781
    Likes Received:
    3,007
    Location:
    Saline Michigan
    Tube, bar, whatever. GJ/L is torsional stiffness, Tr/J is torsional stress. Generally, a tube is close to a solid bar on both stiffness and strength, with it mostly gaining weight when you fill in the center.
     

Share This Page

arrow_white