[Music] foreign welcome back to helicopter lessons in 10 minutes celeste i'm jacob and this video covers the topic of mushing now the term mushing typically only shows up in army manuals because it's usually prevalent the most in a dive recovery not a lot of airframes or other jobs find themselves diving as much as army helicopters especially the attack and recon types but you know some of the civilian helicopters or depending on your helicopter job you could find yourself in a stall condition sorry a dive condition so it's important to know not to get into mushing because it is a temporary stall that could affect your ability to recover that aircraft simply put it's going to be a temporary stall condition as a result of being at high air speeds while conducting a rapid apt cyclic application it's a it's nothing more than just a stalling of the airfoil simply put both planes and helicopters can stall when aggressively recovering from a dive because of how it affects the critical angle and the resultant relative wind acting on the air fuel now i'll use some explanations in this video that puts uh or that pull from my disimitry of lift expanded video so if you need or want a refresher on those or some of these terms don't quite make sense just click on the link the link that appears either in the video or the description and i break down parts of the air for a little bit more but let's get started so quick recap of the air fuel let's say we got an air foil right here to be useful to the airfoil the wind or the resultant relative wind needs to impact in the critical angle that means generally on the front side of the aircraft or of the airfoil the resultant relative wind needs to impact here to produce lift broken down even further if i were to draw my cord line through the blade here i'm going to have a few other regions that start to pop up so we'll just kind of draw some lines out here that's going to be the positive lift region we've got the positive stall region the negative lift region the negative stall region and then back here in the back is going to be a reverse flow region so what i need this airfoil to do to act properly and produce lift is i need the resultant relative wind to impact inside this positive lift region to produce lift if i don't have that the blade of the helicopter doesn't produce lift if all of them are doing it then i'm potentially going to be falling out of the sky because i don't have any lift so let's look at getting set up for a dive profile so prior to the dive if i'm in straight level flight i'm generally traveling and this way and the resultant relative wind is this way it's generally going to be inside that that positive lift region as i start to pitch over and induce a dive profile the aircraft is coming down like that now i'm in the dive profile the aircraft is traveling in this direction resultant relative wind in this direction still inside that positive lift region but let's say that uh i'm done shooting guys in the face with diving rockets and i need to recover this aircraft before impacting the degree the terrain so if i pull back with a quick aggressive f cyclic my profiles are going to change to something like this where the nose is high after you know pulling up from the dive obviously i don't want to go close to the ground anymore but what happens is the aircraft's momentum continues to push it this way resultant relative wind pushing this way and so now when i'm seeing this airfoil the whole rotor disc my airflow the resultant relative wind or the combination of my forward air speed induced flow angle of incidence all of that put together causes my resultant relative wind to impact the airfoil inside the positive stall region positive stall means there's no more left being created this airflow if it's outside this critical angle it's useless airflow it's nothing but drag i'm not recovering from airflow or the airfoil is not able to use this airflow in this region so in this profile the aircraft is now mushing say towards the ground it's continuing to travel towards the ground so you'll feel feedback and flight controls and the aircraft continues its descent despite having a pitched up attitude trying to arrest the descent now this was talked about heavily by world war ii fighter pilots doing strafing runs in their planes who barely recovered the aircraft in time after doing strafing runs or they witnessed other pilots who were not so lucky now the same holds true for planes and helicopters today today the faa uses the term c-fit or controlled flight into terrain to describe flight conditions where an aircraft strikes the ground without any kind of mechanical problems and that's what's going on here there's no mechanical problems this is a aerodynamic phenomena of the resultant relative wind just not impacting in the right general area of the airfoil so how do you recover from this important to know if you ever find yourself in this situation now the tendency is to clam up and apply even more af cyclic but this just prolongs the stall this is only going to make it worse the only way to get out of this mushing condition is actually to apply forward cyclic and this reduces the severity or shifts that resultant relative wind back inside the critical angle makes it useful so instead of arresting a dive with that much of a nose no side attitude maybe you have an attitude like this where the mo the momentum is still carrying the aircraft that way but the airfoil is still getting that resultant relative wind inside the critical angle in the positive lift region specifically to be able to recover out of this so recovery is going to be forward cyclic reduce the severity of the dive recovery now you should start to feel a little bit more authority with the cyclic and you begin to slowly reapply as much af cyclic as needed but if you ever find yourself mushing then apply more forward cycling get the airfoil airflow back inside the critical angle of the airfoil but the best fix is to never get into mushing in the first place so how do you avoid mushing well the only way to avoid it is really just to understand why it's cost so it's it's caused because the aggressive nature of the diver recovery so if you want to avoid it use a slower or a more progressive af cyclic um now that since the speed of the af cyclic is what is really causing the mushing condition avoid the rapid aggressive nature of it all that goes to say is with any flight maneuver always allow enough altitude to recover keep in mind that at higher altitudes and air speeds say if you're up in the mountains and the air is thinner the amount of time and altitude required to recover from these type of maneuvers is going to increase so always think ahead the worst time to realize that you cannot recover from maneuver or from a maneuver is while you're actually in the maneuver but that wraps up mushing it's a temporary stall condition that predominantly is experienced during aggressive half cyclic most common with dive recoveries thank you all for watching if you need more clarity on these five regions of the ear full uh be sure to check out my video to symmetry of lift expanded where i break that down further aside from that if you found this video helpful or informative be sure to hit the like subscribe and leave a comment below as always i'm jacob this is helicopter lessons in 10 minutes or less safe flying