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Recent content by jpaero

  1. jpaero

    Re-framed- Skin shear flow with ribs

    Just in case you missed, the questions were: 1. Will the shear flows in the skin/spar vary across the bays if all the bays enclose the same area? If they do vary, what causes the change, and what factors determine this variation? 2. If the shear flows remain constant across the bays, I assume...
  2. jpaero

    Re-framed- Skin shear flow with ribs

    At the outset, this question in some fashion is a follow-up of my previous question but I feel is worth asking as a separate one. Let us say I have a wingbox as shown below subjected to pure torsion at one end and cantilevered at the other. I understand that I can calculate the shear flow as...
  3. jpaero

    Skin shear re-distribution

    Thank you for the response. Yes, I totally understand that buckling loads of the combined panel will be lower than that of the individual smaller panels. These are not highly optimized structures and the applied loads are low enough for me to explore combining the panel. If ok, I want to...
  4. jpaero

    Skin shear re-distribution

    I have a structure similar to the one shown below. The structure was originally analyzed using FEA with Rib(A) present. Due to some issue, we need to ignore the presence of Rib (A). We are not in a position to re-run the FEM. We have the panel shear flows for each of the panels based on the...
  5. jpaero

    Cut-out reinforcement design drivers

    Would anyone know what drives the design of cut-out reinforcements? For eg: how do I go about designing a pax door cut-out surround? What would my design drivers be? I can think of the skin stress being a limiting parameter. But are there any other? Also, if you are doing an initial sizing...
  6. jpaero

    Bending moment acting on an aircraft rib

    While I get that the reaction system with 4.09N/mm shear flow reacts the torsion, I do not understand what it does to the rib. For example, what if there was no rib in this system (when looking at torsion alone)?
  7. jpaero

    Bending moment acting on an aircraft rib

    I also think something doesn't add up in the bending moment diagram. The F/S reaction is approx 1878N and the R/S is ~250N. The remaining ~255N comes out as the vertical component of the shear flow in the inclines. At the front spar, it's just 3.56*260*260/2=120,328N/mm. (Matches) At 332.5mm...
  8. jpaero

    de Havilland Comet Design changes

    Thank you everyone for your inputs!! I guess I have found "the" details I was looking for: 1- A constructional method for minimising the hazard of catastrophic failure in a pressure-cabin (https://reports.aerade.cranfield.ac.uk/handle/1826.2/299) 2-Pressure-cabin design a discussion of some of...
  9. jpaero

    de Havilland Comet Design changes

    @3DDave:"The majority of efforts aren't to stop propagation, it's to never start one to begin with and to detect any that have started." I thought you can almost reliably never stop a crack from initiating. All you can do is to ensure that when one starts, you have designs in place to slow them...
  10. jpaero

    de Havilland Comet Design changes

    Just wanted to note here that there is a youtube video by Prof. Paul Withey on the accident pretty much on the lines of the presentation in verymadmac's link above. https://youtu.be/K5HqEwbp4GA While I find it immensely useful, it falls short of the design measures used to prevent the kind of...
  11. jpaero

    de Havilland Comet Design changes

    I am trying to learn the specific design related issues with the de Havilland Comet. I have read the investigation report which spoke of: 1. Underestimation of stresses at the corners 2. Overloading the fatigue specimen before the fatigue test itself 3. Testing only the fwd fuse and effect of...
  12. jpaero

    Fatigue load spectrum

    @Ng2020: My question was related to methods of extrapolating flight measurements to cover for gusts that were not experienced during those flights. For example, if I do a single test flight to arrive at my 10,000 flight cycle usage spectrum, the test flight almost certainly will not experience...
  13. jpaero

    Fatigue load spectrum

    Thank you all!! The information in your responses is going to take me a while to digest!!!
  14. jpaero

    Fatigue load spectrum

    Background: I am involved in a fatigue life extension project of an aircraft. The initial fatigue life of the aircraft was determined using a theoretical load spectrum of 10,000 FC. And now we want to evaluate the actual fatigue life consumed. So we are going to perform a few flights (in line...
  15. jpaero

    Standards for Sailplanes (I4-FVK/91)

    I have managed to get hold of a copy from the LBA. Just for information, this document forms the requirement basis for composite materials including the fatigue test requirements.
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