Mushing in Helicopters
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- čas přidán 13. 06. 2021
- Welcome back to Helicopter Lessons in 10 Minutes or Less! I'm Jacob and this video covers Mushing.
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The term "mushing" typically only shows up in Army manuals and isn't really seen much in other military manuals or civilian manuals. This is because this aerodynamic feature tends to happen during dive recovery, a profile Army helicopters can frequently find themselves in, especially attack and recon helicopters. But the term is defined as a temporary stall condition at high airspeeds with rapid aft cyclic application. Simply put, both planes and helicopters can stall when aggressively recovering from a dive. I use some explanations in this video that pull from my Dissymmetry of Lift - Expanded video ( • Dissymmetry of Lift - ... ) if you want or need a refresher on some of the parts of the airfoil seen shortly.
To be useful to the airfoil, airflow needs to impact inside the critical angle. That is, the Resultant Relative Wind (RRW) needs to be below the chordline and inside the critical angle to produce lift. Broken down further, there are 5 regions of the airfoil: Positive Lift, Positive Stall, Negative Lift, Negative Stall, and Reverse Flow. We need airflow specifically in the positive lift area of the airfoil for the blade to produce lift. Anything else and the helicopter doesn't produce lift and falls out of the sky.
In straight and level flight, the rotor system is predominately operating in the positive lift region. The combined effects of forward airspeed, induced flow, and angle of incidence put it there. The same holds true as a helicopter enters a dive profile. The aircraft is traveling towards the ground and the RRW is in the critical angle. But if I pull back aft cyclic too quickly or aggressively my profile changes but the helicopter's momentum still carries it in the same direction. The RRW shifts underneath and into the Positive Stall region of the airfoil. The aircraft is now mushing. You may feel feedback in the flight controls and the aircraft continues its descent despite a pitch-up attitude.
This was talked about heavily by WW2 fighter pilots during strafing runs in their planes who barely recovered in time or witnessed others not so lucky. The same holds true today for planes and helicopters. Today the FAA uses the term CFIT (Controlled Flight into Terrain) to describe a flight conditions where aircraft strike the ground without any mechanical issue. Mushing is not a mechanical failure. Its an aerodynamic condition.
So how do you recover? The tendency is to clam up and apply more aft cyclic. But this prolongs the stall and can make it worse. The only way to get out of mushing is to apply forward cyclic and rotate the RRW back into the positive lift region of the airfoil. You should start to feel more authority with the cyclic and begin to slowly reapply aft cyclic as needed to recover. But the best fix is prevention. To avoid mushing, use a slower, more progressive aft cyclic in dive recoveries. Since its the speed of aft cyclic application, just avoid the rapid, aggressive nature. All that goes to say you should always allow enough altitude to recover from any maneuver. Keep in mind that at higher airspeeds and Pressure/Density altitudes, recovery from a dive increases in both time and altitude required. Think ahead. The worst time to realize you can't recovery is while you're trying to recover.
That wraps up mushing. It is a temporary stall condition predominately experienced during aggressive dive recoveries. Thank you for watching. Be sure to hit like, subscribe, and leave a comment.
As always, I'm Jacob. Safe flying.
Just when I thought I had a good understanding, from your previous videos, you add another one to remind me I still have more to learn. Thank you for these videos.
Glad you enjoy them. I’ve got plenty more in the works.
@@helicopterlessonsin10minut10 Air National Guard, NY currently exercising special night flying techniques/equipment, Adirondacks, NY
You know what I enjoy most about your delivery? You don't assume the viewer knows more than basics. In other words, understanding what you're getting across is easy because of how you lay out the information.
That’s the goal. Breaking it down so just about anyone, even non pilots, can understand. I appreciate the feedback!
@@helicopterlessonsin10minut10 you're welcome
An interesting story Jacob... 35 years ago when I was young and dumb (now I'm just dumb), I was goofing off in my Aeronca L-16A when landing one day. I was at or over gross weight as I had a large man in the back seat and at the time, I was over 250lbs... and I was making a very steep approach and pulled hard at about 50' above the runway at about 90mph. I definitely felt the wing, "let go" and all lift was lost and the plane was mushing toward the ground. Thank goodness for the big wing of the champ and when I let off the pressure on the stick, lift was regained about 5' from mushing into the runway, which based on the descent rate would have probably broken the airplane and our backs! Never did that again, but am just telling this story as it is not only fighters that can experience this effect. I guess some would call this a high speed stall, but I like the explanation of mushing and it certainly felt like that. Love your videos. Thanks for all your expertise and time.
Glad you’re back
Definitely been finding your videos useful with converting from PPL fixed wing to helicopter. Felt instantly at home in a helicopter which never fully felt in the fixed wing. Thanks for making the videos.
Doing the same thing rn and couldn’t agree more.
Just passed the SIFT on Monday with a 58. As a prior medic its been tough learning all of this from scratch but your videos help a lot!
Awesome! Be sure to leave some feedback on one of the SIFT prep videos and share what you did well on as well as what was the most challenging parts.
studying for the SIFT now, currently enlisted with no aviation knowledge. I'd love to ask you some questions!
@@jordanking5273 I'll try to answer them to the best of my knowledge
It's like a really fast and aggressive settling with power situation. Great video, great explanation.
Awesome to see you back! I missed your videos!
Interesting topic and instruction. I was a Utility guy and I think this phenomenon should be taught to the Army UH population more often. An interesting rule of thumb is at high gross weight, 90 kts IAS, 60 degree bank angle, the aircraft doubles in weight and will loose altitude. It’s fatal at low altitudes.
Excellent posting, thanks for share it.
Keep up the awesome work!
love your work. thank you.
He returns! Praise be
You are back, thanks
Hey Jacob, it’s been a while. I just wanted to drop in and say THANKS. Your videos helped me immensely with passing the SIFT. Fast forward to now, I’m at Rucker in common core hold. I will continue using your videos to learn and refresh. You are doing great things for aviators and future aviators!
great video!
I’m training myself to be more regular, not to spend too much time on the toilet. These videos give me a good window of time to shoot for.
THANKS FOR THE VIDEO
Awesome. Thanks!
Is this not really simply a specific case of settling with power, wherein momentum is exceeding lift?
To be distinct from vortex ring state by not being characterized by disrupted airflow (for a period of time within the correction, anyway), though it threatens to rapidly become so.
Thanks for posting. Welcome back sir!
Good to be back. I appreciate you checking in over the years David.
@@helicopterlessonsin10minut10 absolutely sir.
Think 💭 ahead! Key point in flight as well as many aspects in life!
Hey, welcome back!
Welcome back! I just bought your book
Thanks!
Thanks!
You came back just when I finished watching all your old videos. Perfect timing!
Much Obliged Sir,, 👌👌
I'm sure you are familiar with the g loading chart in the -10. Do you know if the g loading chart is to prevent structure damage to the airframe or to prevent pilots from getting into mushing? (Positive G only) What happens if you exceed the positive g limits from the g loading chart?
G loading doesn’t necessarily mean you’ll get into G loading limits. It’s a separate aerodynamic situation. G loading can damage the aircraft specifically in the rotor system. That’s usually the limiting factor. 2G’s essentially means the aircraft doubles in weight. That’s a lot for a rotor system to handle. Great question.
Hey sir, great explanation! So what’s the difference between mushing and autorotation
Another informative video thanks PS got watch those tan lines : )
Not from a watch but from a memorial bracelet for a friend lost in combat. Glad you enjoyed the video!
What is the different between the mushing and jackstall?
The Mi-24 suffers bad from this becuase of its speed, weight, and it’s wing behind the rotor that stalls at similar AOA as when the rotor stalls. The manual mentions giving not only forward cyclic but decreasing collective 1-3 degrees.
It’s simulation in DCS seems to agree with this. Couldn’t reducing collective to un stall blades also be part of recovery for other helicopters?
The madlad!
I’m old. I had to look that up haha! Thanks
@@helicopterlessonsin10minut10 Anytime. Im glad I could teach you something too. Not as cool as these helicopter videos though, thanks!
I'm of the class of heli-simmers that pine for more realism in the simming experience INCLUDING the warts of flight. Because we like the idea that we could be pilots and are experiencing the same sorts of constraints but your videos show me there are an enormous number of little constraints that are not at all or adequately modeled in the sim. This makes us bad sim pilots because we are overly confident based on ignorance of real world limitations that the simulator blithely ignores. I have little idea what kind of maneuvers I can or cannot get away with because the sim doesn't give much attention to those limitations.
👊
how different settling with power?
I've heard of SWP during a quick stop. Is this the same principle that the positive stall region is eating the wind because of the angle?
The difference between Settling with Power and Mushing is airspeed. SWP is less than ETL where a second set of vortices can form. Mushing occurs at airspeeds far faster than ETL where there’s no way a second set of vortices can develop. Mushing is a positive stall condition whereas SWP refers to root vortices combined with wing tip vortices. Great question!
@@helicopterlessonsin10minut10 thanks!
Can this also be caused by to Rapid of a quick stop in forward flight?
It could. Any drastic aft cyclic could cause this. It’s just most prevalent in dive recoveries.
J.W. you in any of these choppers in the intro's?
Yep. I’m in the lead aircraft here.
😎🤜
Is “mushing“ similar to “settling with [insufficient] power“?
Mushing is more of a stall. Regardless of how much power you pull it won’t fix the stall. You need to change pitch of the disk. Settling with insufficient power is more like developing a high sink rate without enough power to arrest it towards the ground. Think high, hot, heavy and a high rate of descent that there’s just not enough power to slow down at the bottle so you impact with quite a lot of force.
How to loft a small car nearly of700-800 grams
I’m sorry but I don’t understand your question.
I mean that for a project I need to lift a toy car how can I lift it or fly it
I would determine the weight and see how much power available you have for a helicopter to lift it. Check out the max gross weight hover charts.
@@helicopterlessonsin10minut10
Make understand in simple words
@@helicopterlessonsin10minut10 I want to make through motor
So, forward cyclic to recover. Ok, so you are sacraficing altitude for airspeed, to get aircraft back in trim. This mushing thing is also causing a high "G" condition where pulling more aft cyclic can cause mast bumping. Not good! Instead of "diving" why not do down collective while going forward to get a shallow angle of descent, mind you, you are descending at 2000ft per minute +/-, while still keeping the aircraft level and in trim. While still hauling ass descending, a bit of forward cyclic n up collective should get your ass up rather quickly with ETL, Effective Translational Lift... This mushrooming thing is not a good manuver, IMO...