My Safety Concerns About Bubble Canopies

Discussion in 'Rules and Regulations / Flight Safety / Better Pil' started by JayKoit, Oct 17, 2018.

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  1. Oct 19, 2018 #21

    plncraze

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    An old Kitplanes had an article about a T-18 that rolled over. The roll bar stayed in shape but the rivets which held it to skin tore out. The writer said to consider the vertical fin your roll over protection and to draw a line from the fin to the top of the engine, in the case of the T-18, and make sure your head was below that line.
     
  2. Oct 19, 2018 #22

    BJC

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    Properly motivated, it is possible to bust through a flat wraped 1/8” plexiglass canopy head first.


    BJC
     
  3. Oct 19, 2018 #23

    pictsidhe

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    Auto centre punches work great on brittle materials. High impact plastics may resist them. It would be well worth testing scraps of your actual canopy to see if they are an option, or not...
     
  4. Oct 20, 2018 #24

    Daleandee

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    Something learned by many when building a Sonex ... the best way to bust the canopy seemed to be a tool like this:

    [​IMG]:roll:

    Dale
    N319WF
     
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  5. Oct 20, 2018 #25

    lr27

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    A high feed rate with a bandsaw works, if I recall correctly. Plus you break the bandsaw blade! Not something to carry in the cockpit, I suppose. ;-)
     
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  6. Oct 20, 2018 #26

    pictsidhe

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    I put a drill into reverse when drilling perspex and melt my way through.
     
  7. Oct 21, 2018 #27

    bifft

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    I have heard that center punches will easily break a cold canopy, but not in hot weather. Haven't tried it myself, but do have some scraps left over I could try on.

    Have one similar to https://www.emergencykits.com/emergency-supplies/automotive/emergency-hammer-3-in-1 strapped where I can easily reach it in my RV.
     
  8. Oct 21, 2018 #28

    lr27

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    You could probably blow it out with an air bag. Which might be nice to have anyway. A bit fiddly to install, I guess.
     
  9. Oct 22, 2018 #29

    Riggerrob

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    Some designers recommend drawing that line from the engine to halfway up the vertical fin. Fins tend to bend or crumple during roll-over accidents.
     
  10. Oct 22, 2018 #30

    lake_harley

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    A friend of mine was killed when his plane (RV6A) ended up upside-down during a landing accident. No official report yet, but it would appear his neck was broken and spinal cord severed. His passenger also received a broken neck but is recovering. I'm not too familiar with the details of a RV6A and wondered if it has any sort of roll bar? I suspect it does, and photos I saw of the plane after the crash it doesn't appear that it was crushed down to the fuselage. Report is that the passenger's head actually went through the canopy. I questioned, when talking about the accident with friends, if perhaps shoulder belts were properly tightened or if investigation will reveal that shoulder harness (which the plane had) may have been left somewhat loose for "comfort" or to be able to reach things on the instrument panel.

    Having a background with stock car racing, there are a lot of improperly installed and yet more improperly used shoulder belts. I wonder how many lap/shoulder belt systems are improperly installed or left somewhat loose for any variety of reasons. The accident was a pretty severe reality check.
     
  11. Oct 22, 2018 #31

    gtae07

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    The RV-6/6A does have a roll bar. If a sliding canopy, it's a steel bar and forward brace; on the tip-up it's a built-up frame just aft of the seats.

    Many builders only install a 4-point harness. From personal experience in Dad's RV-6 slider, unless you first tighten the lap belt crushingly tight, then the shoulder straps crushingly tight, it's possible to whack your head on the canopy doing spins or with a good thump from turbulence. A normal "snug" 4-point harness still gives a lot of movement, compared to my experience in a couple of RVs with 5-point harnesses at the same "snugness".

    My RV-7 will have 5-point harnesses.
     
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  12. Oct 22, 2018 #32

    BJC

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    Yes, a properly installed 5 point harness holds one down (into the seat). That also helps keep one from sliding forward under the lap belt during deceleration. The shoulder harness keeps one’s face out of the instrument panel during deceleration.

    High negative g is flown with the shoulder straps loose, and both seat straps, one with a crotch strap, tight.


    BJC
     
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  13. Oct 22, 2018 #33

    wsimpso1

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    Shoulder belts in airplanes are supposed to be led to points at or above the shoulders to prevent compression fractures of the spine in the much more common up and back impulse from a forced landing. Shoulder belts installed this way do NOTHING to prevent upward movement of the torso when the whole thing inverts and stops with a thump.

    I am way more suspicious that the laps belts were loose, which are supposed to be applied across the pelvis, snugging you aft and down when tight. When loose, the lap belt will allow your head to hit the overhead with vigor and result in broken necks. Loose belts are common...

    Billski
     
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  14. Oct 22, 2018 #34

    wsimpso1

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    You did not get the joke. Many a builder has found out that conventional drill bits will "hog in" on plexiglass and send a crack clear across a windshield or canopy, causing you to purchase another canopy. Bits may be modified or purchased already modified that will behave just fine in plexiglass...

    Billski
     
  15. Oct 22, 2018 #35

    Twodeaddogs

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    Fully agree with Billski.....the sound perspex makes when you crack it and watch dollars metaphorically fly out the door....
     
  16. Oct 22, 2018 #36

    BBerson

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    If you install a couple "emergency" holes in the canopy edge, a steel bar could be inserted and pried to send a crack across the canopy.
     
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  17. Oct 22, 2018 #37

    BJC

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    I lean toward explosive bolts to forcefully remove the canopy mounting hardware. Blast shields may be necessary to protect the pilot and passenger, and, for safety, a hand crank generator to charge the firing circuit should be installed for those occasions when neither the battery nor the back-up battery can get the job done. The added weight is the real safety feature, though; the airplane will be too heavy to fly.


    BJC
     
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  18. Oct 23, 2018 #38

    lr27

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    If you leave off the blast shields, no medical care will be required.
     
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  19. Oct 23, 2018 #39

    rdj

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    Getting flipped and trapped in my 650 bubble canopy is a long way down on the list of ways I can kill myself in the plane. It's also generally easier to flip taildraggers than it is to flip tricycle gear aircraft like the 650. Provided there's no fire my primary concern would be making sure I had an adequate supply of snacks while sitting on the bubble canopy waiting for help to arrive.
     
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  20. Oct 23, 2018 #40

    Twodeaddogs

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    you need to have an FW 190 in your life. 20mm cannon cartridge to blow off the canopy.....
     
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