Preparing for emergency landings (canopy)

[Bad Sheila]

Have AN RV6. Canopy came open in flight. Could close the rear latch but not the side latch.
WARNING: When landing my stall speed was increased by 10-12 kts. Luckily I have the Skyview AOA with audible warning. Imagine my surprise when I was slowing to 60 kts for landing and the stall warning horn was screaming at me. YOU HAVE BEEN WARNED!

[sailvi767]

Something does not seem right with seeing a 10 to 12 knot increase in stall speed. That really should not happen with the canopy partially open. I am wondering if there might be a pitot static issue in your aircraft. Perhaps the canopy being open caused a pressure change in the cockpit leading to a false airspeed indication. A 20% increase in stall speed is just not plausible with a canopy open a few inches or even missing for that matter.

George

[Bill Boyd]

Took off with tip-up canopy unlocked and only able to pull down enough to get the secondary latch holding it. Completed the flight and landed normally with the canopy thus ajar, and it was a normal flare and normal landing at customary speeds (65 MIAS over the numbers and 50 at the touchdown).

I suspect you have a static issue somewhere.

-Stormy 6-A

[ijustwannafly]

Originally Posted by gmcjetpilot

RV's tend to flip over with off field landings so regardless have some gear to break, cut, pound, pry and bend (pliers) in case you need it.

As far as latch unlock before touch down, that's a PIC decision. I think having the tip-up closed gives some more roll over strength? Sliders are hard to impossible to open in flight, as I'm told, not withstanding optional builder installed pull-pins in the fwd rollers. Good luck you'll need it.

PS: if there's engine fire and smoke, opening a slider canopy could draw smoke/flames into the cockpit. The tragic Oregon RV-8 accident showed that.

What accident do you speak of?
This is a very concerning subject for me. Its probably one of my biggest fears. After flying airplanes with doors like everyone else here most likely started in, going to a canopy style airplane adds a new fear to landing poorly, flipping the airplane, or as you guys are discussing a forced water landing.

Let me ask you this. I am somewhat perplexed over the fact that the general consensus is that it is hard to get a slider open in flight or a tip up down in flight.
That is counter intuitive to what most people would think.
The rushing air should all but blow the slider back and or push the tip up down into place.
Can someone explain this more please?
Thanks

[lr172]

Originally Posted by ijustwannafly

What accident do you speak of?
This is a very concerning subject for me. Its probably one of my biggest fears. After flying airplanes with doors like everyone else here most likely started in, going to a canopy style airplane adds a new fear to landing poorly, flipping the airplane, or as you guys are discussing a forced water landing.

Let me ask you this. I am somewhat perplexed over the fact that the general consensus is that it is hard to get a slider open in flight or a tip up down in flight.
That is counter intuitive to what most people would think.
The rushing air should all but blow the slider back and or push the tip up down into place.
Can someone explain this more please?
Thanks

Seems somewhat intuitive to me. Opening the canopy will allow air into the cabin at a high velocity (think sticking your hand out of the car window at 80 MPH. Now imagine doing it at 150 MPH). Pressure will be exerted on every surface, including the canopy, as the air cannot exit. This pressure would lift the canopy and place a good deal of force on the sliding mechanism. I don't have a slider, but am guessing that this upward force causes enough friction to prevent movement. The sliding mechanism should be designed to eliminate friction at a downward trajectory (from gravity) and not likely for an upward trajectory.

Larry

Larry

[cfiidon]

Originally Posted by lr172

Seems somewhat intuitive to me. Opening the canopy will allow air into the cabin at a high velocity (think sticking your hand out of the car window at 80 MPH. Now imagine doing it at 150 MPH). Pressure will be exerted on every surface, including the canopy, as the air cannot exit. This pressure would lift the canopy and place a good deal of force on the sliding mechanism. I don't have a slider, but am guessing that this upward force causes enough friction to prevent movement. The sliding mechanism should be designed to eliminate friction at a downward trajectory (from gravity) and not likely for an upward trajectory.

Larry

Larry

I believe you need to consider the venturi effect. When you open the canopy slightly, you are allowing high speed air to flow over the openings (at the canopy bow and around the sides), creating a very low pressure inside the canopy itself, or relative high pressure outside the canopy. To use your car window analogy, cracking the windows a little bit sucks air out. Open them enough and the air blows in also.
I imagine the same thing occurs with the canopy. Open a little and it's trying to close itself. At some point the venturi effect will reduce and the pressures will "balance". Past some point the canopy will probably try to blow off.
Where is that point? I'm sure a wind tunnel test could find it, or a very brave test pilot.

Don

[LettersFromFlyoverCountry]

I didn't put the quick release mechanism in (well, actually, I took it out early) because I didn't want to cut into the top skin to allow the hinges to pop out.

I've thought about this a lot and while I carry a plexi busting thing, I'm pretty sure that one the cabin fills with water, I wouldn't be able to swing it through the water with enough force to do much damage. I just don't know.

At the same time, I can see the plane flipping over in a foot of water and be unable to get out.

So I've thought this idea: What about smashing the canopy BEFORE you ditch?

[dhc2jeep1]

I, too, am wondering why it is difficult to open a slider canopy in flight. Please don't get me wrong, I am not doubting anyone's experience. I just wonder what is different between a RV slider and an AT-6 slider? I took some aerobatic training in a AT-6 and was instructed on the ground that in case I started to feel sick, to let the instructor know and we would open the canopy to the first notch for some fresh air. At the end of the first hour, I did start feeling sick and we opened the canopy to the first notch. It was not overly easy, but it also was not impossible either. I was also taught that if we had to bail out, we would open the canopy all the way and then jump out toward the wing. This makes me think about all the WWII pilots that jumped out of fighters with sliders too.

[rvbuilder2002]

Originally Posted by Bad Sheila

Have AN RV6. Canopy came open in flight. Could close the rear latch but not the side latch.
WARNING: When landing my stall speed was increased by 10-12 kts. Luckily I have the Skyview AOA with audible warning. Imagine my surprise when I was slowing to 60 kts for landing and the stall warning horn was screaming at me. YOU HAVE BEEN WARNED!

Bad Sheila
Here is a warning back to you... I think it is highly likely that you have a leak in your static system that was influenced by a large pressure change inside the fuselage with the canopy open.

As far as why RV canopies open or can't be opened... it is at least partially caused by a varied distribution of aerodynamic pressure...

The shape of an RV canopy results in high pressure (on the outside) at the base of the windshield and at the aft portion where the canopy or rear window is interfacing to the top of the aft fuselage. There is low pressure in the zone of the high point in the canopy (above your head), just like a wing airfoil.
Depending on the canopy type (slider or tip-up) the delta between these pressures will cause different results.
I.E., a tip up lifts at the back because there is low pressure at the back of the moving portion of the canopy. A slider is difficult to open because there is high pressure pushing down on the aft end, resisting the lifting it needs to do during the start of the opening process.
There are likely other influences as well... such as friction in the rollers and slides on a slider induced by the pressure loads, etc.

[RKellogg]

I used to give instruction in Thorp T211s, a low wing with sliding canopy similar in configuration to an RV, but a tad chunkier and slower. We used to open and close the sliding canopy in flight. Effort was not more than one person could manage easily. The Thorp canopy rolled fore/aft on a straight / horizontal rail system, and it didn't close nearly as cleanly as an RV. The open canopy cost about 10 knots in speed, IIRC.

The POH forbade landings with the canopy open, perhaps because the canopy could roll shut, perhaps due to tail blanking at high AOA...??

Someplace out in an Illinois cornfield there is a camouflage BDU cap that I lost while demonstrating the canopy procedure to an Air Force Colonel/ B-52 pilot. (Had a great time, Warren!)

- Roger