HPC 7 #1 November 15, 2017 We all know that F111-type material is only good for a certain number of jumps before its porosity exceeds 12 CFM and good flares and soft landings become problematic. But what about hybrid canopies with ZP upper skins and F111 elsewhere? Because of the F111 component, do those canopies have a life expectancy as well? The ZP will hold up, the F111 won't, so overall how will the canopy perform once the F111 part of it wears out? Thanks.What's right isn't always popular and what's popular isn't always right. Quote Share this post Link to post Share on other sites
sundevil777 93 #2 November 15, 2017 HPCWe all know that F111-type material is only good for a certain number of jumps before its porosity exceeds 12 CFM and good flares and soft landings become problematic. But what about hybrid canopies with ZP upper skins and F111 elsewhere? Because of the F111 component, do those canopies have a life expectancy as well? The ZP will hold up, the F111 won't, so overall how will the canopy perform once the F111 part of it wears out? Thanks. I think that using non-zero porosity fabric on the lower skin does not result in lower performance over time. When a wing is flying at high angles of attack (such as during a flared landing), it is very important that the airflow over the top of the wing stay "attached"/not separate from the surface of the wing. If air is leaking out through the top skin fabric too much, then I think it has the effect of separating the airflow. Conditions on the bottom skin of the wing are very different, with separation not being an issue, so leakage through non-ZP fabric on the bottom doesn't matter. If it was possible to actually suck air into the wing through/from the top skin, then you get the ability to produce good lift at even higher angles of attack, as the airflow stays attached when it otherwise would not. This has been done on some experimental airplanes, including a Boeing 757 testbed that had part of the wing drilled with very tiny holes and a vacuum applied to suck air into the wing. So, air leaking out through the fabric matters a lot for the top skin, but not for the bottom, as long as it is not so much that cell pressurization suffers. That's my theory on why non zp is being applied on bottom skins, and I think it makes sense. In my previous life I was a mechanical design engineer, even did such for the Boeing company.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
HPC 7 #3 November 15, 2017 *** When a wing is flying at high angles of attack (such as during a flared landing), it is very important that the airflow over the top of the wing stay "attached"/not separate from the surface of the wing.*** Is this what they call the boundary layer?What's right isn't always popular and what's popular isn't always right. Quote Share this post Link to post Share on other sites
sundevil777 93 #4 November 15, 2017 Quote When a wing is flying at high angles of attack (such as during a flared landing), it is very important that the airflow over the top of the wing stay "attached"/not separate from the surface of the wing. Is this what they call the boundary layer? It is a part of the overall subject, having the boundary layer stay "attached" to keep it generating more lift until the critical angle/angle of attack when it doesn't stay attached which is when the wing is considered to have stalled.People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am Quote Share this post Link to post Share on other sites
