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  #11  
Old 09-17-2017, 07:43 PM
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snopercod snopercod is offline
 
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Quote:
Originally Posted by rv7charlie View Post
...no one mentions any flight characteristics change when it pops open.
Read the Lancair report linked above. It's all in there.
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  #12  
Old 09-17-2017, 08:05 PM
Tony Rome Tony Rome is offline
 
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Default http://www.vansairforce.com/community/showthread.php?t=122941

Hope this helps, older thread discusses several factors.

Tony Rome

http://www.vansairforce.com/communit...d.php?t=122941
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  #13  
Old 09-17-2017, 09:11 PM
rv7charlie rv7charlie is offline
 
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Quote:
Originally Posted by snopercod View Post
Read the Lancair report linked above. It's all in there.
The linked articles are RV-specific, and my responses were intended to be RV-specific. Guess I shouldn't have made the reference to doors on certified planes (only mentioned to demonstrate that pilot distraction is more likely than aero issues in an RV).

Sorry :-)

Charlie
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  #14  
Old 09-17-2017, 11:53 PM
Captain Avgas Captain Avgas is offline
 
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Originally Posted by mike newall View Post
I have had a canopy come open on both a 7 and a 12 ..........

In neither event was there a marked change in handling - yes, there was a startle effect, more so on the 7 as I was not expecting anything, on the 12, I was still under flight testing so was expecting the unexpected !
Vans current Service Letter on Tip-up Canopies suggests that a significant nose-down pitch is a very real possibility if the canopy pops open in flight. It also suggests that different flight configurations may affect the outcome. This would be consistent with some RV pilots reporting minimal change in flight characteristics with others reporting quite severe pitch down. Here is an extract from the Vans Service Letter:

"Field reports indicate that if the canopy does become unlatched in flight, the aircraft will most likely pitch nose down abruptly. The severity of the pitching moment can depend on speed, attitude and weight and balance".

It is interesting that the ATSB report indicated that one of the objects that flew out of the cockpit when the canopy came open was a hand held radio. I am imagining that the amount of wind turbulence in the cockpit required to pick up a portable radio and suck it up and out of the plane must have been immense.
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Last edited by Captain Avgas : 09-17-2017 at 11:57 PM.
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  #15  
Old 09-18-2017, 04:20 AM
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mike newall mike newall is offline
 
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Quote:
Originally Posted by DHeal View Post
Mike -- Why did you "hold on to the canopy" during your approach and landing? Were you concerned that it would rise up further than the initial 12" and depart the airframe or interfere with aircraft controlability? What do you think might happen during the approach and landing if one did not hold onto the canopy? Thanks for sharing your experience. -- David
David,

Initially, the canopy raised by about a foot, although there was no change to pitch. I spent 5 minutes swapping hands and finding a combination of throttle, holding the stick and stopping the canopy going up and down that meant I was happy that no unexpected pitch changes would occur at slower speed. Just thought it would be safer to hold the canopy during the approach and landing, rather than have it free floating.

The whole thing was reported to Vans and to our LAA with photos, the main cause was that the catch had asymmetric leg lengths, so when swapped 180°, it gave the visual impression of being latched, but when airborne, the aerodynamic forces on the canopy pulled the latch out of the catch and it opened. We are now building 2 RV12's and notice that the catch and secondary and microswitch alert system has significantly increased the safety and robustness of the system.

The RV7 was pure dumbness

Bob,

I guess on both of mine, I was lucky that there was no pitch down, or if there was, instinct checked it.
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  #16  
Old 09-18-2017, 08:35 AM
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Snowflake Snowflake is offline
 
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Originally Posted by Captain Avgas View Post
It is interesting that the ATSB report indicated that one of the objects that flew out of the cockpit when the canopy came open was a hand held radio. I am imagining that the amount of wind turbulence in the cockpit required to pick up a portable radio and suck it up and out of the plane must have been immense.
I suspect it's more likely that this was one of the cases that experienced a significant pitching-down moment, which would have floated the handheld radio (and probably a lot of other stuff) off the seat/floor/wherever. Possibly far enough to carry it out the opening, but at least far enough that the winds took it from there.
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  #17  
Old 09-18-2017, 09:45 AM
edbooth edbooth is offline
 
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Default Canopy latch

Have had canopy pop up twice, once in a 6 and once in a 7. Both times due to pilot lack of attention.😕There was no significant change in flight attitude. Just slowed to 90 kts, held the stick with my knees, pulled down, latched and flew on. Unless there is something extrordinary going on, I don't think it creates a eminent crash situation. IMHO
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  #18  
Old 09-18-2017, 10:00 AM
BillL BillL is offline
 
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Quote:
Originally Posted by snopercod View Post
Read the Lancair report linked above. It's all in there.
Quote:
Originally Posted by rv7charlie View Post
The linked articles are RV-specific, and my responses were intended to be RV-specific. Guess I shouldn't have made the reference to doors on certified planes (only mentioned to demonstrate that pilot distraction is more likely than aero issues in an RV).

Sorry :-)

Charlie
Reading the Lancair report, there was report of pilots of an RV7 that tested the canopy release effects, speeds and pitching. It said that pitch could be affected by pushing it up or pulling it down from a stabilized position. It seemed directly relevant to the topic.

On my fitting of the tip up (-7), I struggled with the design intent. The fitting has to be near perfect between loose and too tight. I did two things, fitted stiff rubber stops to define the "down" condition, then adjusted the latch force to get both sides to latch at the same time. Even a soft rail seal is too much to compress with the flexible latching system, and the bar flexes (torsion) allowing one side to latch but not the other. It could certainly use some design improvement, but IMO it can be fitted to latch well with some attention, and judgement.

On a side note, ensuring the plexiglass at the rear corners had 1/8" clearance to the roll bar base angles, and fitting the stops saved my bacon when the garage door hit the open canopy and closed it for me. Only minor scratches and no damage, except to my underwear.
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Last edited by BillL : 09-18-2017 at 10:10 AM. Reason: added information
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  #19  
Old 09-18-2017, 12:33 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Captain Avgas View Post
Vans current Service Letter on Tip-up Canopies suggests that a significant nose-down pitch is a very real possibility if the canopy pops open in flight. It also suggests that different flight configurations may affect the outcome. This would be consistent with some RV pilots reporting minimal change in flight characteristics with others reporting quite severe pitch down. Here is an extract from the Vans Service Letter:

"Field reports indicate that if the canopy does become unlatched in flight, the aircraft will most likely pitch nose down abruptly. The severity of the pitching moment can depend on speed, attitude and weight and balance".

It is interesting that the ATSB report indicated that one of the objects that flew out of the cockpit when the canopy came open was a hand held radio. I am imagining that the amount of wind turbulence in the cockpit required to pick up a portable radio and suck it up and out of the plane must have been immense.
Note that the above quote from the Service Letter says "Field Reports"

Flight characteristics with an unlatched canopy has not ever been tested by engineering at Van's.

Field reports means that some (a couple that I am aware of) reports have been received that indicated an abrupt change in pitch when the canopy opened. Since it has not been formally tested, those reports can't be ignored just because there is other reports to the contrary, but there have been lots of others that indicate nothing notable occurred.

Why the difference? No way to know. It could have been because of very light or no grip on the stick at the time of opening? Because of the light pitch stick forces on an RV, an aerodynamic or pitch trim change that might pitch the nose over a large amount might only take a small amount of stick pressure to counter.

There is a lot of evidence that indicates that with normal input from the pilot, nothing significant occurs other than a lot of noise and wind.
As the Service Letter points out, the goal needs to be to assure that an open canopy doesn't occur by inspection for proper construction, adjustment, and operation of the mechanism, and use of a check list to help mitigate the human factor.
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Last edited by rvbuilder2002 : 09-18-2017 at 02:06 PM.
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