Preparing for emergency landings (canopy)

[RKellogg]

Originally Posted by rvbuilder2002

Bad Sheila
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.

Easy check : Do the static source instruments respond to abruptly opening/closing cockpit vents while in flight? When I have the in-cockpit alternate static source open, the altimeter and ASI show very direct response to vent changes (on the order of 10 kt or so). Opening a fresh air vent slightly pressurizes the cockpit and decreases indicated airspeed and reported altitude.

it is not entirely inconceivable that a partially open canopy would disturb the airflow at the static ports and cause the reported error.

- Roger

[ijustwannafly]

Originally Posted by cfiidon

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

Thanks Don
This is precisely what i was referring to.

[6S4 Hugo]

Originally Posted by Ironflight

I am sure I read a story about a fellow who ditched his -8 out in Hawaii maybe two years ago (it was while I was building), and survived, but I can't remember where I saw it....

http://archives.starbulletin.com/200...ws/story1.html

"After impact the canopy closed and the aircraft inverted underwater, trapping me in the cockpit," Justman said in a written statement. "I released my shoulder harness and seat belt and worked at opening the canopy while underwater for over a minute."

"Miraculously, the canopy partially opened ... and I was able to eject myself from the cockpit just before the aircraft sank," he said.