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Thread: Flying with windows open.

  1. #1
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    Default Flying with windows open.

    New to the forum and CC #128. Here is a question.

    I am aware the POH restricts flying with windows open on take off. During flight, the POH restricts to one side open. I've seen cubs fly with windows, doors open or even removed.

    What is the reason for this restriction?

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    Default Re: Flying with windows open.

    Welcome to the forums. This restriction was also covered in a service instruction discussed in more detail here.

    To summarize, flying the plane at higher speeds causes greater buffeting and air pressure in the back of the aircraft. There have been cases of delamination of the rear windows.
    Last edited by Adam Sloon; 05-01-2013 at 07:31 AM. Reason: Typo

  3. #3
    Senior Member turbopilot's Avatar
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    Default Re: Flying with windows open.

    Quote Originally Posted by Adam Sloon View Post
    Welcome to the forums. This restriction was also covered in a service instruction discussed in more detail here.

    To summarize, flying the plane at higher speeds causes greater buffeting and air pressure in the back of the aircraft. There have been cases of delamination of the rear windows.
    I note this sentence in the Service Instruction:

    "This issue has been limited to aircraft with an early style of both window frame design and adhesive technique which has since been revised."

    Could you describe and/or show some images of the updated windows. Can older planes be modified or retrofitted with the revised windows?
    Bob Anderson, CC11-00435, N94RA

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    Default Re: Flying with windows open.

    Pete will correct me if I am wrong, but I believe there are two separate but linked issues. The main windows (the ones which hinge open) did not always have the center piece of tubing which runs vertically in the middle of the window. This change was made fairly early on according to the drawings. The cracking issue was limited to old styles of window, but the change cannot eliminate the amount of prop wash in that area, so the risk still exists. If your aircraft does not have the newer style, I am sure an MRA could be made to make that change.

    The rear windows, or D-windows, are the ones which had the issues of delamination. Having both main windows open at higher airspeed forces a lot of air into the back of the aircraft, which combined with increased prop wash buffeting had caused cases where edges of the windows had begun to separate from the surface they were bonded to.
    Last edited by Adam Sloon; 05-01-2013 at 01:05 PM.

  5. #5
    Senior Member turbopilot's Avatar
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    Default Re: Flying with windows open.

    Quote Originally Posted by Adam Sloon View Post
    Pete will correct me if I am wrong, but I believe there are two separate but linked issues. The main windows (the ones which hinge open) did not always have the center piece of tubing which runs vertically in the middle of the window. This change was made fairly early on according to the drawings. The cracking issue was limited to old styles of window, but the change cannot eliminate the amount of prop wash in that area, so the risk still exists. If you aircraft does not have the newer style, I am sure an MRA could be made to make that change.

    The rear windows, or D-windows, are the ones which had the issues of delamination. Having both main windows open at higher airspeed forces a lot of air into the back of the aircraft, which combined with increased prop wash buffeting had caused cases where edges of the windows had begun to separate from the surface they were bonded to.
    I have the center tubing in the main windows, so has there been a modification in the aft "D" windows in later SN's to prevent delamination?
    Bob Anderson, CC11-00435, N94RA

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    Default Re: Flying with windows open.

    Quote Originally Posted by turbopilot View Post
    ...so has there been a modification in the aft "D" windows in later SN's to prevent delamination?
    Early on the sealant was changed to Parrbond. Around S/N 109 there was a change to the fuselage which added channels to the bottom and rear edges of the D-window mount.

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    Default Re: Flying with windows open.

    Are there any solutions being explored? Flying with the window/door open is one of the reasons for flying a cub.

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    Senior Member randylervold's Avatar
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    Default Re: Flying with windows open.

    Quote Originally Posted by Fresno View Post
    Are there any solutions being explored? Flying with the window/door open is one of the reasons for flying a cub.
    Quickly detachable windows are in the development queue which we'll get to at some point. Note that below 80 mph you can fly with the windows open. As Adam has relayed we have experienced some adhesive failure with the early rear windows in the hot climates when operating with both windows open hence the restriction. The 80 mph restriction is somewhat arbitrary, the latches that hold the window open seem to let go at about that speed. As the manufacturer we unfortunately need to keep worst case scenarios in mind.

    Personally, I like to open the right window AND door and leave the left one closed. That way when slipping it in you don't get any cross cockpit turbulence yet you still get the feel of an open cockpit airplane.

    Remember, this aint your granddaddy's J3 which topped out at 70 mph. With the 180 hp fan up front everything has to deal with much more stress. So, open the windows and doors, stay below 80 mph, and go enjoy some treetop flying!
    Randy Lervold

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    Default Re: Flying with windows open.

    Thank you for the clarification. I look forward to the future advancements.

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