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Post by silverdragon on Nov 3, 2012 8:45:32 GMT
Helicopters...
The rotors are above your head, mostly WAY above your head, so why the "Monkey walk" as you walk to and from?....
I dunno, it seems as if the extra few inches aint goina do THAT much good?....
Ok, so it was a Chinook a few years back (last century) that I got this strange wandering from, as I can plainly SEE that the rotors are a few feet (cough...) up from me.... but then again, a Sea-King SAR, as well, its not exactly claustrophobic under those either, yet there I was, upright, plenty of room, surrounded by intelligent folks who know what they are doing, and I am the only one NOT doing the Monkey-Walk half crouch to walk under the rotors?....
And they are looking at me as if I have a death wish?....
C'mon people, common sense required, why DO we do the monkey walk under rotors if they are well out of reach?... and if something DID go wrong, would that inch or so actually do you any good, or would it in fact HINDER you as you tried to get out of there?....
Or is it a psycho-semantic(sp?) thing?... we "[think]" we are safer so we are?....
Its been on my mind for 20 years, why have I taken this long to ask?....
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Post by memeengine on Nov 3, 2012 11:11:46 GMT
I'm no helicopter expert but I just assumed that it's a carry over from the earlier military helicopters. These were smaller than the current generation so that the rotors were lower to start with. Also the materials used for the rotors were less stiff and consequently as the rotors slowed down (and the lift decreased) the ends sagged downwards. So people moving to and from the helicopter ducked down to avoid getting hit.
There's probably a bit of over reaction involved in it too. If you put a sign above a doorway saying "mind your head" people will still tend to duck a little even if they could easily walk through normally.
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Post by Lonewolf on Nov 3, 2012 12:25:45 GMT
Even though I have a fixed wing license, I'd never gotten (that) close to a helicopter before last year and I always said the same thing. "There's plenty of room, why duck?".
Then I rode one to a remote repeater site. I damn near crawled to and from that beast even though there was 4' or so clearance.
I'd say it's a psychological reaction to something that can easily kill you so close to your dead.
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Post by trakmec on Nov 3, 2012 18:48:15 GMT
well for the UH60’s depending on your angle of approach to the AC, and the angle of “attach” for the rotors wither they are 90 degrees to the airframe, or some other position relative to the AC it is quite possible to hit them from the front. This may be more likely on unlevel terrain, that’s why you approach the AC from the sides, Head on approach bad, rear approach VERY bad!  On top of that if the rotors are turning up speed for lift off they do create some noticeable downward force |
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Post by Lokifan on Nov 3, 2012 18:57:49 GMT
I always wondered about that, too.
I sometimes thought it was because people saw the monkey walk on TV. ;D
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Post by silverdragon on Nov 5, 2012 6:31:50 GMT
I have to admit, them spinning overhead, I walk to-and-from with one eye on them....
I dunno, for sure, if one was to actually dip and hit me?... I suspect I would be in an are where getting lightly thwacked upside the back of the heed would be the smallest of problems, a blade that dipped that low would not be exactly as designed........
Yeah, its psychological I suppose, but why?...
IS it just because we all watched "Mash" when we were kids, and saw them do it on there?...
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Post by the light works on Nov 6, 2012 6:19:15 GMT
put simply: you can't really see the rotor accurately, and the ground may not be level as it looks - and it is one of those cases where even though the risk is low, the consequences are rather extreme. in our training on working with the crew of our local air ambulance, the orders are:
1: always stoop when under the rotors when the engine is running.
2: NEVER go more then the length of the stretcher behind the loading door when then engine is running.
3: always wear eye protection when the engine is running. (getting pelted by gravel kicked up from the rotor wash is a good reminder)
it is also worth noting that when you are stooping you are less likely to unthinkingly put your hands above your head.
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Post by silverdragon on Nov 9, 2012 8:45:26 GMT
Good points TLW about the eye protection... I have had grit in the eye on one occasion.
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Post by the light works on Nov 9, 2012 15:51:14 GMT
the rules about stooping and keeping clear of the tailboom are based on the fact that at close quarters you can't really "see" the rotors properly, and it is possible to accidentally get into harms way - so you keep farther away than you actually NEED to, just to avoid the rather severe circumstances of getting it wrong.
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Post by GTCGreg on Nov 9, 2012 17:08:55 GMT
While in college, I spent my summers working for a charter helicopter service and spent a lot of time riding in and working around copters. We had a couple of monster Sikorsky's that there was no way you needed to duck when walking near. We also had 3 Bell 206 Jet Rangers and 2 Bell 47Gs. Those were another story. While the main rotor was a few feet above your head, it was possible for the rotor to dip down well below your head line if the pilot wasn't paying attention and accidentally hit the stick or a gust of wind came along. We were always told to keep our head down when under a rotating rotor.
Far more dangerous than the main rotor is the tail rotor. On most copters it's low enough to walk into and turns so fast that it is almost invisible. Far more people are injured or killed by the tail rotor than being struck by the main rotor.
It's also hard for the pilot to see if someone is standing near the tail of the aircraft. If the pilot lifts off and pivots, you could easily be struck by the tail rotor if you are anywhere near. A good rule is NEVER go near the back of a helicopter when the engine is running.
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Post by silverdragon on Nov 10, 2012 8:23:33 GMT
Tail rotors, I always adopt the "Corridor" idea, you take a direct 90 deg to the aircraft direct approach to the doors and dont ever go towards the tail... EVER ever... unless the engine is off and no movement on either rotor and you have a set of spanners and are qualified to use them?....
Craft with Low main rotors, I agree, if its only a few inches clearance, DUCK ...........>>[PULL!]
I was specifically addressing the ones with a few FEET clearance and above?....
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Post by the light works on Nov 11, 2012 0:40:34 GMT
Tail rotors, I always adopt the "Corridor" idea, you take a direct 90 deg to the aircraft direct approach to the doors and dont ever go towards the tail... EVER ever... unless the engine is off and no movement on either rotor and you have a set of spanners and are qualified to use them?.... Craft with Low main rotors, I agree, if its only a few inches clearance, DUCK ...........>>[PULL!] I was specifically addressing the ones with a few FEET clearance and above?.... the rotor on the REACH air ambulances is about 7-8' of clearance - with the blades and ground both level. no guarantee of either at the time you happen to be standing under them. when loading a patient, one or two people have to break the 90 degree plane as the stretcher loads at a 45 degree angle between the pilot (front right) an the nurse (rear left) and BTW, don't drive below your guardian angel's stall speed.  |
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Post by silverdragon on Nov 11, 2012 11:33:53 GMT
My Guardian Angel has VTOL... Pegasus was the name Rolls Royce adopted for the power plant in the Harrier Jump Jet... It has always been, and always will be, alongside the Merlin in my Hall of Fame for favourite engines. My only experience of rescue craft is our own wonderful RAF Sea-King... Westland WS-61 Sea King is a British licence-built version of the American Sikorsky S-61 helicopter of the same name, built by Westland Helicopters. (That direct from Wikapedia will suffice as explanation..... en.wikipedia.org/wiki/Westland_Sea_King ) It has side doors, and high above the head rotors. |
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Post by Lokifan on Nov 16, 2012 20:43:20 GMT
You know, it would be a visually interesting test to see how near you could put a Buster head to a rotating helicopter blade.
Making a rig to verify forces in the vertical and horizontal (will the airflow knock you over before the blade hits?), and gradually raising an analogue into the spinning blades.
Kind of a super-sized ceiling fan test. ;D
Maybe mix in the much PTD "Fan Death" nonsense to fill out the hour. Or at least for a quick mention to put it to rest.
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Post by c64 on Nov 16, 2012 20:55:27 GMT
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Post by the light works on Nov 17, 2012 3:16:11 GMT
This is our boys. great guys and they have no qualms about taking the bird out of level flight, if necessary. www.reachair.com/ |
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Post by silverdragon on Nov 17, 2012 9:40:53 GMT
You posted a "At Rest" photo... when at rest, the rotors are easily visible and not (much) danger.... When spinning, they rise up, even centrifugal force will make them rise without any input from the pilot.... With the Chinooks that do drop-offs or collections of troops and equipment in "Hot" zones (Afghanistan) they actually dont "Quite" do a full landing, more hover with the wheels on the ground, in case of "Incoming" and having to do an emergency GTF-Outa-Here.... I as a passenger have never yet boarded a Helicopter with the blades at rest, as the pilot usually has them spinning, after doing about half an hour of pre-flight checks, and he dont want no passengers whittling on and blethering about absolute [deleted] that may distract him whilst pre-flight checking?.... I am not sure about Air Ambulances here, as have never had the misfortune to need one, but do they actually switch the big fan off when loading passengers?.... I know that the Sea-King when doing Sea rescues does not... for obvious reasons?... they dont like getting wet.... |
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Post by c64 on Nov 17, 2012 12:52:36 GMT
It depends. Restarting the engine takes a while and isn't exactly good for the engine. When idling, the "big fan" rotates slowly with not much centrifugal force.
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Post by the light works on Nov 17, 2012 15:53:57 GMT
it depends on how hot the extraction is. last time, they were filling in on what would have been a "medical taxi" transport if a car had been available. the pilot shut it down and gave us the grand tour while the patient was being delivered to us (it was an alternate location pickup because the ceiling was too low for the hospital helipad)
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ronbo6
Demi-Minion
Survivor: End of the World. 12/21/2012
Posts: 91
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Post by ronbo6 on Nov 18, 2012 2:56:24 GMT
I'm no helicopter expert but I just assumed that it's a carry over from the earlier military helicopters. These were smaller than the current generation so that the rotors were lower to start with. Also the materials used for the rotors were less stiff and consequently as the rotors slowed down (and the lift decreased) the ends sagged downwards. So people moving to and from the helicopter ducked down to avoid getting hit. I believe you are definitely onto a lot of the basis for it there. As a pretty graphic example of when and how the 'monkey walk' was necessary, just watch the opening credits from the old M*A*S*H TV series. The rotors on those Korean War medevac choppers weren't all that much above their heads under all operating conditions. |
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On top of that if the rotors are turning up speed for lift off they do create some noticeable downward force 
