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  #1  
Old 01-19-2012, 04:52 PM
Rhino889's Avatar
Rhino889 Rhino889 is offline
 
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Default Jettison able Canopy

Jettison able Canopy:

No one ever wants to ditch a canopy… but it might be useful to do so in certain situations.

My mission profile is 1000ft down the beach enjoying the view, aerobatics and occasional flights with the wife down in the Bahamas’ island chain.

I’ve read at great lengths regarding the 8’s canopy and getting out in flight while tumbling around. This is a possible concern, however for me ditching in water situations is also a possibility. The thought of a ditch at sea while your passenger is sitting back there, most likely still cocooned under the canopy... not good.

From what I’ve read, most guys put quick-disconnect pins where bolts normally go for connecting the rollers and canopy bow. Some have suggested both pulling the pins in emergency situations and also flying with the pins completely out (downward and forward air pressure on the canopy).

I’m not comfortable flying with the pins out. I’m sure it’s fine and I don’t question others for doing it. It’s just not for me.

Pins engaged causes a problem in my mind for VERY rapid jettison and exit. Too many steps:

1. Rotate canopy handle for disengage of latching mechanism.
2. reach left, find pin
3. pull pin
4. reach right, find pin
5. pull pin
6. PUSH UP and BACK with everything YOU GOT!

* I separated the find and pull steps to illustrate the time and effort of performing this task under tumbling situations.

My solution cuts down the steps to:

1. rotate canopy handle for disengage of latching mechanism
2. pull back while giving UPWARD pressure. (upward should be natural in this situation)


I’ve spent some time trying to figure out a simple (USMC style) solution to this problem. My desire was to have something quick and natural, something you do every time you exit the aircraft.

RV-8/8A factor: The “cool” things about the RV8 canopy system. I want to be able to open the canopy 3-4 inches in flight (Florida heat) and taxi with the “Cool-guy arm on the rail”. I won’t make excuses, I want to look cool! With that in mind I made sure these two factors were retained.

I plan on cutting out 3 inches (3x roller diameter) of the roller track’s upper cap. Approximately 15 inches and extending to 18 inches behind the front canopy bow. This was determined for me personally using seat back rest and leading edge of my shoulders. I place the cut-out before the shoulder because of “cool-guy arm” position would dictate canopy locked into position behind shoulder. This cut-out position also gives a 10+ inch buffer behind my inflight open canopy position. Should the canopy somehow become unlocked from the inflight position, the downward and forward air pressure on the canopy would have a margin for ????.

The only other player would be on the ground while loading people. I think we can all agree that gravity will retain the roller for 3 inches while traveling forward-rear-forward.

Scenario 1: Tumbling from doing a maneuver reserved for MX2/ Extra aircraft. Wing left about 20 seconds ago! Time to try and catch it leaving fuselage behind! Dang, guess those engineers know what they are talking about!?


1 rotate canopy handle for disengage of latching mechanism
2 pull back while giving UPWARD pressure.

Once rollers get to cut out: Canopy gone…
Time to go skydiving

Scenario 2: Flying with wife over open water. Engine quits/ Fire onboard/ etc.

1. Within couple 100 feet of water and slowed (possible canopy impact with HS, slow speed reduces blunt force trauma on HS)
2. rotate canopy handle for disengage of latching mechanism
3. pull back while giving UPWARD pressure.

Once rollers get to cut out: Canopy gone…(hopefully)
Time to go swimming

I present this to the group for input and ideas. It’s always better to get as many different opinions on a safety subject like this. I’ve left some thoughts out to allow for free exchange of ideas. Instead of just countering mine, I’d like the clean slate approach. I figure someone has thought of this or done this by now? I haven't been able to find anything with the searches?

Hopefully nobody ever needs this modification, but hey $h1% happens!

Disclaimer: I do not recommend this and I have not tested it. I am just a pilot, not an engineer.

These are some rough cut up scrap. Final product would have nice rounded edges and look better.





Maintaining the structural form


Blue tape is position of my cuts (determined by pilots shoulder+seatback)

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Last edited by Rhino889 : 01-19-2012 at 04:54 PM.
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  #2  
Old 01-19-2012, 05:06 PM
Mike S's Avatar
Mike S Mike S is offline
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Default

Sure seems like it would work, but then I only want an 8, dont really have one bit of experience with them.

Pretty sure one of the 8 flying guys will chime in sooner or later.

Good use of out of the box thinking.
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  #3  
Old 01-19-2012, 06:40 PM
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panhandler1956 panhandler1956 is offline
 
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Default

Rhino,

I like your idea. The only risk I can see is maybe normal ops on the ground in heavy winds. If a gust caught the canopy as it was transitioning the 'gap' in the tracks it might make an unplanned departure - probably a remote possibility.

I have the pins in mine, and they are definitely not a perfect solution. I don't mind flying with them out, but I fear I'll forget them and damage my canopy (same wind gust or prop blast scenario) on the ground with it open or partially open.
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  #4  
Old 01-19-2012, 07:26 PM
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NickAir NickAir is offline
 
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Location: McMinnville, Oregon: HOME of the SPRUCE GOOSE
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Default

I have thought about this as a safety issue on RV's for years. I, have no engeneering data to confirm the safety of the modification so I never did it. Van did not recommend it as there is a rear canopy pressure that complicates the issue. I don't know about other complications that he may have understood. I am a skydiver and have considerations of actually exiting the cockpit. There was an RV pilot that did exit his RV from the air due to a likely cockpit flame out when the canopy was unsecured. Good safety issue to consider. Hopefully this issue will make some progress with other's input.

The partially open option for in flight, (2-12 inches,) has been discussed by many RV pilots and builders over the years. Van does not approve it though. Needs more research. I have heard a few others say that it is really hard to slide a slider to the rear while in flight. Pressures on rear of canopy while in flight. Never tried it myself. It would be a nice option for some of us.

The jettison issue is a question of if the canopy could be moved to the rear and then pushed up into the airstream for the jettison. It seems that if a person could lift the canopy up an inch or so the slipstream would take over with removing the canopy.

I am not an engineer and I have no practical experience with this issue. All my comments are opinions only. I look forward to what other's input will contribute.
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  #5  
Old 01-20-2012, 05:42 AM
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pierre smith pierre smith is offline
 
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Default Like Strega.

The unlimited P-51, Strega, doesn't have a lip that the canopy slides under. It merely butts up against the windshield, so there's no restriction to the canopy simply leaving upward, not being retained by the lip.

I looked at it at Reno and it's a really nice, close fit...might consider that as well. Have no clue as to how noisy that might be tho',

Best,
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  #6  
Old 01-20-2012, 07:36 AM
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RV8RIVETER RV8RIVETER is offline
 
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I would think that you would be better off with the opening at the front of the rail. That way, you will have help holding it down with the windscreen fairing (canopy slides under) and being at the first part of travel you will have your hands on it to open so won't have to worry about any gusts while on the ground. Also less time to open in emergency, just clear the windscreen fairing, which is just shy of 1/2" on mine.

Whatever you choose it would be good idea to mark the area in red, visible to thhe pilot from inside to know where it is.
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  #7  
Old 01-20-2012, 08:11 AM
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chepburn chepburn is offline
 
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Its a good idea, but, in the heat of the moment, pulling back and up 'just right' to get the rollers up and out of the track may be easier said than done. (Imagine being a little too aggressive on the aft vs the up and overshooting the slot)

I have no idea on how to do this, but how about a 2 action system.

1: Unlatch canopy lock.
2: Pull Canopy jettison handle(s)... the action of this handle(s) is to pull back on canopy and raise a ramp inside the rail that guides the rollers up and away through your cut out. I dont think the mechanics of this would be too tough, and the big red jettison handle(s) would look cool as well.
Imagine aft sliding handles on both sides that pushes up on a triangle wedge mounted below the rail that push up through a slot. The wedge is a ramp to guide your rollers up. The overall travel of the handles would only have to be about 4 inches.

Chris
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  #8  
Old 01-20-2012, 10:18 AM
terrykohler terrykohler is offline
 
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Default Where Did You Get the Extrusion that You're Using?

Scott:
I could be wrong, but it appears that the aluminum that you're using is the hardware store variety. If that's the case, you should be aware that there's a big difference in strength between aircraft alloys and what might be used to frame a screen door. Most wrought aircraft product goes thru some sort of secondary heat treat process and also is typically formed with fillets and radii.
If it isn't aircraft grade, DON'T USE IT. Certainly not to help hold on your canopy.
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  #9  
Old 01-20-2012, 11:10 AM
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dbuds2 dbuds2 is offline
 
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Default Great Thread Rhino

Gotta love this forum for exploring experimental ideas with real world experiences.

Seriously considering your idea as I don't see a downside. I have the little cam over mid position stop and would cut my track to make sure there is still both up & down restraint while taxiing.

Someone mentioned flying with the pins always out. Other than remembering to reinstall when on the ground, has this system worked acceptably?
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  #10  
Old 01-20-2012, 11:12 AM
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Quote:
Originally Posted by Rhino889 View Post
....
I?ve spent some time trying to figure out a simple (USMC style) solution to this problem. My desire was to have something quick and natural, something you do every time you exit the aircraft.
....
I'm not sure if this is the logic you want.

If it's something you do as a normal exit then you risk have a loose canopy on the ground every time you get out.

It's a bit like glider pilots not wanting to get out of the cockpit with their chutes on - so they instinctively un-buckle both the seat belt and chute harness on every normal cockpit exit.

It has been known for pilots (but maybe an OWT) to undo both harnesses and then jump in an emergency.

Your emergency action should be easy, but different....
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