# What sort of obstructions can a helicopter propeller withstand? **URL:** \ **Category:** Factual Questions\ **Created:** [November 19, 2014, 9:29pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105 "2014-11-19T21:29:16Z")\ **Posts on this page:** 13\ **Page:** 3
**Author:** ![Scumpup](https://avatars.discourse-cdn.com/v4/letter/s/ce73a5/32.png) [@Scumpup](https://boards.straightdope.com/u/Scumpup)\ **Post date:** [November 20, 2014, 5:25pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/41 "2014-11-20T17:25:22Z")
> [@Chronos](#): > > Wouldn’t this make it really, really easy to shoot down a military helicopter, if all you need to do is get something as big and tough as a cloth bag into the path of the wing? Military helicopters to which you might want to do that are often shooting at you with some frightening weapons of their own. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [November 20, 2014, 5:40pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/42 "2014-11-20T17:40:49Z")
> [@Chronos](#): > > Wouldn’t this make it really, really easy to shoot down a military helicopter, if all you need to do is get something as big and tough as a cloth bag into the path of the wing? The trick is to get your obstructions into the path of the helicopter. They used balloon barrages in WWII to keep enemy planes higher, but London still got bombed. I’d have to ask the SO, who flew Black Hawks in the Gulf War, but I know at least some military helicopters are equipped with millimetre wave RADAR that can detect smaller obstructions. ISTM that if you want to set up a ‘net’ (or more accurately, vertical obstructions) you need some way to keep them up there. Balloons can easily be seen. You could string obstructions between high points – and indeed, helicopters are lost and people are killed when they fly into wires spanning canyons – but these can often be avoided when the attacking force knows about them. You could develop a weapon like a TOW rocket that trails a line behind it, but it would have to be fairly large to carry a long enough snare of sufficient diameter to bring down a helicopter. If such things were worth making, they probably would have been made already. I doubt one could be improvised that would work beyond the first few times and after the surprise wears off. Really, the best way to bring down a helicopter is to shoot at the fuselage in hopes of killing the crew or destroying the engine(s). You can do this with machine guns or shoulder-launched missiles or rockets. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [November 20, 2014, 5:58pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/43 "2014-11-20T17:58:11Z")
> [@Johnny\_L.A](#): > > **Re: Stranger’s post on rotor heads** > Robinsons have a semi-rigid, aka ‘teetering’, rotor system. I always laughed during the preflight when I inspected the rotor head. I’d look at the teeter hinge and think, ‘That one bolt holds the rotors on. Hm… Best not to think about it.’ 😛 That would be the [Jesus pin.](http://en.wikipedia.org/wiki/Jesus_nut) ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [November 20, 2014, 6:11pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/44 "2014-11-20T18:11:31Z")
> [@Johnny\_L.A](#): > > **Re: Stranger’s post on rotor heads** > Robinsons have a semi-rigid, aka ‘teetering’, rotor system. I always laughed during the preflight when I inspected the rotor head. I’d look at the teeter hinge and think, ‘That one bolt holds the rotors on. Hm… Best not to think about it.’ 😛 A.K.A. the “Jesus bolt”, as in “Jesus Himself installed it and blessed it, and if it comes off there ain’t no Resurrection for you.” > [@silenus](#): > > I always _liked_ flying in helicopters. Of course, the last time I did so was damn-near 50 years ago. They used to run a commuter service from the Orange Show grounds in San Bernardino into LAX flying Sikorsky S-61Ls. I have two words for you, “In…Sane”. > [@Chronos](#): > > Wouldn’t this make it really, really easy to shoot down a military helicopter, if all you need to do is get something as big and tough as a cloth bag into the path of the wing? Yes, very much so. Which is why military attack helicopters don’t get in dogfights (despite what you see in films) and generally follow the tactics of flying nap-of-the-earth (NOE) while being directed by an observer (typically a high altitude fixed wing surveillance craft) toward a target to minimize exposure, then popping up and launching before returning to a protected position. The alternative is flying as high an altitude as possible over hostile territory to stay out of small arms range, but they’re obviously pretty much totally exposed to any anti-aircraft fire capability. People have flown A-10s and F-14s back to airfield or carrier with entire wings missing or one engine totally gone, but lose a single rotor blade or the tail rotor on a helicopter and you are now falling in a 20 million dollar deathtrap. Only crazy people fly helicopters (apologies to the mentally disabled who do so). Stranger ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [November 20, 2014, 10:06pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/45 "2014-11-20T22:06:25Z")
I don’t go as far anti-helo overboard as \*\*Stranger \*\*does, but thinking back to my Olden Dayes with Uncle Sam and counting up the number of times a helo nearly killed me versus the vastly more missions I did in conventional aircraft, I begin to wonder whether he has more of a point than I’d given him credit for. All in all, sometimes the past is better left unexamined. Or at least un-tallied. Aaah, the comparative recklessness of youth. ---
**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\ **Post date:** [November 20, 2014, 10:35pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/46 "2014-11-20T22:35:06Z")
who used to fly huey’s in vietnam > [@](#): > > Haley rotor blade. The chord with, which is the measurement from the thick front of the blade that greets the wind to the thin backside of the blade is A minimum of 24 inches, dependent on the helicopter and the blade configuration. Mine was 24 inches, but it does not look like it until you actually are next to it. The blades are laminated to incredible strength yet flexible. They could absorb amazing battle damage (for example, bullet holes, stress from achieving maximum G forces, etc.). It was very common for the Hueys to vertically descend into a temporary Landing zone “LZ” while the blades were chopping tree limbs and bamboo to a maximum of 2 inches in diameter. Now, the front edge could sustain some damage, but we had to be careful to minimize any adverse effects of the airflow which created the lift to keep us in the air. They were amazingly strong, with the inertia generated in these huge blades allowed for landing without power in emergency autorotation procedures. > > I don’t remember the exact weight of the blade, but they were heavy. The second of the blade was approximately 2 1/4 inches thick, again depending on the model. The blade’s rotated in normal operation at approximately 660 rpm. ---
**Author:** ![fisha](https://avatars.discourse-cdn.com/v4/letter/f/da6949/32.png) [@fisha](https://boards.straightdope.com/u/fisha)\ **Post date:** [November 21, 2014, 12:00pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/47 "2014-11-21T12:00:57Z")
> [@Stranger\_On\_A\_Train](#): > > God, I hate helicopters. Every time I have to ride in one I wonder what I did in a past life to deserve this. > > Stranger If you love them, they will love you back. Til death do you part. Fixed wing, would rather not, the plane only tolerates me, commercial I get lost in the crowd, but helicopters are a glorious integration. Kind of like a horse that you have esp with, or a really good partner and a perfect fit for sex, or the first time I got up on a wakeboard. You just metaphysically get it. I also understand that I will probably die from one of these things. Well worth it. (The above was a romanticized version of reality. ) ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [November 21, 2014, 1:58pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/48 "2014-11-21T13:58:33Z")
> [@fisha](#): > > You just metaphysically get it. ‘It’s very Zen.’ What I mean by that is that you become one with the machine. Helicopters, at least the little ones I can fly, require constant, minute, control inputs to remain stable. Helicopters are inherently unstable, and they need human help. But if you think about these inputs and consciously react to the natural instability, you’ll always be behind the machine. You can’t think about it. You need to let your body and the machine talk to each other without your consciousness getting in the way. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [November 21, 2014, 3:43pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/49 "2014-11-21T15:43:13Z")
> [@fisha](#): > > Kind of like a horse that you have esp with, I can’t stand horses, either; vicious, flighty bastards just waiting for you to turn your back so they can kick you in the ribs, or they freak out because of a branch on the ground. I’ll take a donkey any day; a creature capable of thinking for itself, even if it is a pain in the ass. > [@Johnny\_L.A](#): > > ‘It’s very Zen.’ > > What I mean by that is that you become one with the machine. Helicopters, at least the little ones I can fly, require constant, minute, control inputs to remain stable. You will “become one with the machine” milliseconds before you and the machine are disaggregated into component parts upon contact with the ground. I don’t care how much you are “always behind the machine”; all it takes is for one in the complex chain of components to fail, and now you are in a box that has the aerodynamic characteristics of a slightly rounded brick, falling out of the sky with only in incomplete set of octopus arms vainly flapping in the air to retard your sudden and violent reintroduction to the ground. I mean, come on, they were invented as a child’s toy, and Thomas Edison killed one of his own employees trying to make one work powered by guncotton. It’s an inherently insane machine, only outdubified as a means of transportation by rocket propelled launch vehicles. Stranger ---
**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [November 21, 2014, 3:51pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/50 "2014-11-21T15:51:54Z")
You all seem to think main rotor blades are like dragonfly wings. This is not true for every heli. Apache blades can continue to work with a hole shot out of the middle. Of course, the pilot will probably lose a filling or two from the vibration, but they’ll get back. I saw the MD600 prototype after it had a tailboom strike during autorotation testing - sliced the whole think clean off. The pilot flew it to a safe landing. The main rotor blades weren’t the problem - the lack of directional control was. He had to fly in a spiral until touchdown. Early OH-6s tended to have a lot of tailboom strikes on landing. The blades survived - mostly. [![](http://resizer.lavozdigital.es/resizer/resizer.php?imagen=/deliverty/demo/resources/jpg/3/4/1311957293643.jpg&nuevoancho=950&nuevoalto=570©right=conCopyright&encrypt=false) ](http://resizer.lavozdigital.es/resizer/resizer.php?imagen=/deliverty/demo/resources/jpg/3/4/1311957293643.jpg&nuevoancho=950&nuevoalto=570©right=conCopyright&encrypt=false) Note the blade on the left side. It doesn’t come from the factory with that curve! But you’ll notice the blade is complete. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [November 21, 2014, 4:20pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/51 "2014-11-21T16:20:02Z")
**Low Flight** – Anonymous _Oh, I’ve slipped the surly bonds of earth And hovered out of ground effect on semi-rigid blades; Earthward I’ve auto’ed and met the rising brush of non-paved terrain And done a thousand things you would never care to Skidded and dropped and flared Low in the heat soaked roar. Confined there, I’ve chased the earthbound traffic And lost the race to insignificant headwinds; Forward and up a little in ground effect I’ve topped the General’s hedge with drooping turns Where never Skyhawk or even Phantom flew. Shaking and pulling collective, I’ve lumbered The low untresspassed halls of victor airways, Put out my hand and touched a tree._ ---
**Author:** ![fisha](https://avatars.discourse-cdn.com/v4/letter/f/da6949/32.png) [@fisha](https://boards.straightdope.com/u/fisha)\ **Post date:** [November 21, 2014, 5:54pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/52 "2014-11-21T17:54:55Z")
> [@Stranger\_On\_A\_Train](#): > > You will “become one with the machine” milliseconds before you and the machine are disaggregated into component parts upon contact with the ground. I don’t care how much you are “always behind the machine”; all it takes is for one in the complex chain of components to fail, and now you are in a box that has the aerodynamic characteristics of a slightly rounded brick, falling out of the sky with only in incomplete set of octopus arms vainly flapping in the air to retard your sudden and violent reintroduction to the ground. I mean, come on, they were invented as a child’s toy, and Thomas Edison killed one of his own employees trying to make one work powered by guncotton. It’s an inherently insane machine, only outdubified as a means of transportation by rocket propelled launch vehicles. > > Stranger Well yeah, duh. No one ever mentioned sanity being a prerequisite. Plus I’m a woman, and as my husband has so eloquently mentioned more than once “All women are crazy, it’s just a matter of degrees.” What I think is crazy, is a friend of mine has the same strong opinion of helicopters as you do, **Stranger** , yet he falls asleep within 2-3 minutes every single time. I’ve seen it more than once. ---
**Author:** ![48Willys](https://avatars.discourse-cdn.com/v4/letter/4/db5fbb/32.png) [@48Willys](https://boards.straightdope.com/u/48Willys)\ **Post date:** [November 21, 2014, 7:52pm UTC](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105/53 "2014-11-21T19:52:53Z")
Fisha, He just wants to die peacefully on his sleep! Sorry, I just could not resist. I have flown in all kinds of fixed wing aircraft, once in a balloon, and often at the end of a 25 to 50 foot cable slung under a helicopter. I have yet to fly INSIDE of one. I have been told that it is not as much fun as flying below the thing. You can get to thinking about the whole concept of how a helicopter flies, and that is just plane scary! As an aircraft mechanic, A&P-IA, I am well aware that ALL machines fail at some point. In a helicopter that failure is a touch more likely to be incompatible with flight… Still, if any of you Chopper Pilots were to offer me a ride, I promise you that I will not fall asleep! [Previous page](https://boards.straightdope.com/t/what-sort-of-obstructions-can-a-helicopter-propeller-withstand/705105.md?page=2)