Real Helicopters

[Gate88]

So the job I was on yesterday had a real helicopter on it, never one to miss an opportunity I thought I'd have a good look round it.



This is a twin squirel apparently and its the first time I have studied the real deal in depth up close and what struck me is how little actually holds these things together. The mechanics of the tail for example are remarkably similar to that of my Trex's, a slider on a shaft that goes backwards and forwards controlled by a 90 degree elbow and a rod. The thing that struck me was that the blade grips were only attached to the slider by a couple of bolts that only had 13mm nyloc nuts holding them on.

Now call me an old woman but I'm someone who's had a few model tail failures in my time and they're not much fun but in a real one I should imagine they're significantly less enjoyable.

If you were to scale this down to a 600 size you'd look at it and think those teeny tiny nuts and bolts are never going to hold this together! I chatted to the pilot for a while and granted he only runs a governed head speed of 340 and only has about +4 degrees of pitch but still, knowing helis like I do, even if we had had the time for him to give me a ride I dont think I'd have fancied it much!

[unwind-protect]

What you have to remember is that the Trex is stressed for manoeuvres that would turn your average human inside out, whereas the Squirrel... isn't.

[Gate88]

What you have to remember is that the Trex is stressed for manoeuvres that would turn your average human inside out, whereas the Squirrel... isn't.

Its a good point but 13mm nuts look awful small when your life depends on them!

[Mark_T]

If that bothers you that much, you really don't want to take a close look at an R22 or an S300

[Gate88]

If that bothers you that much, you really don't want to take a close look at an R22 or an S300

Na Probably not!

[Mart61]

If that bothers you that much, you really don't want to take a close look at an R22 or an S300

The AAIB stats speak volumes on this matter.

[trillian]

When I was at a big airshow in Australia last year I had a close look at the mechanics on various helicopters, the tailrotors and linkage, swashplates etc.

It is interesting to see how some of them are put together.

What I find surprising is that some tailrotors are able to tilt just like the rotorheads (like on the Jet Ranger for example). I can see why the rotorheads tilt but never would have thought the tailrotors needed to. (obviously some tailrotors do not tilt at all but some do)

[alioth]

Its a good point but 13mm nuts look awful small when your life depends on them!

The 13mm nuts aren't holding back a great deal of force, though. The metal of the bolt that actually is, is extremely strong - and they do all sorts of engineering calculations to make sure this is so :-) The evidence is that it's not raining Twin Squirrels. If you think 13mm nuts are bad on the tail rotor, before you fly off on holiday take a look around an airliner maintenance facility and take a look at what holds the wings on...then remember the airliner weighs probably *hundreds* of tons.

As for the Robinson helis, in the United States they had to bring out specific regulations just for the R22 and R44 because they are so dangerous for pilots who are not trained in the quirks of these helicopters (they are reasonably safe, as very small piston helicopters go, for those who are properly trained. They tend to get crashed a lot because they are used for training). The main problem with the R22 is that it has very little rotor inertia - if you don't get the collective down straight away if the engine burps, you die, basically. Other helis with much more rotor inertia give you some time (in some helis you can autorotate to the ground, lift off again and do a 360 piro, and land they have so much rotor inertia).

he other problem with them (which is common to all teetering Bell-style rotor heads) is that low-G manoevres can provoke something called "mast bumping". This is a very innocuous name and sounds very non-serious, but what "mast bumping" means is that if the rotor blades hit their teeter stops, the mast snaps off and the rotor head departs from the helicopter. This tends to result in a fairly bad day for the occupants. Also, the main rotor can teeter far enough to chop the tail boom off. If I remember right "mast bumping" was discovered by some unfortunate military pilots trying to follow the profile of rugged terrain in (I think) something similar to a Huey, and tearing off the rotor system when pushing over to go down the back side of a ridge.

[clubb699]

HEHEHE i work for a large Areospace company if i told you half what i see you probably would not go on a plane again

[unwind-protect]

TThe main problem with the R22 is that it has very little rotor inertia - if you don't get the collective down straight away if the engine burps, you die, basically.

"Straight away" in this case being within 1.1 seconds from engine failure; after that the rotor rpm will have died to the point where it will no longer autorotate, the blades fold back or are ripped off, and the game is over.

[crash-alot]

I'll never get in one of those!!!

[alex]

HEHEHE i work for a large Areospace company if i told you half what i see you probably would not go on a plane again

Haha- nice to hear I have faith......................

I have had some fun closeups of real helis as I crew the local lifeboat, so have done lots of joint rescues and exercises, rides and winches included. THe vibration inside makes the vibration we get on our helis seem gentle :P I used to wonder how the helis cope with it, especially after being involved in a mid channel force 9 winter rescue- I remember seeing how much the blades flex and move while hovering and imagining the stresses involved. The blade tips must have been moving up an down by 0.5-1m.

I then fly my 700 in a force 3 and look at how stable it is considering it only weighs about 4kg- gives me a lot more faith in the real thing

Helis defy what is right and that is why they are fascinating.

[p4ddy]

HEHEHE i work for a large Areospace company if i told you half what i see you probably would not go on a plane again

Eaton???

[derrick]

I flew an r22 and the buzz is something else, have done track day's in single seaters but it don't compare to the r22 stall turns and auto rotations better than any fairground rides. If i won the lottery i would get a real one.

[SparkleBee]

Firm i work for does some heli parts jobs, and i also was surprised at how flimsy some of these parts seem. Gazelle tail rotor drive shaft for example is an alloy tube that weighs about the same as a packet of crisps. The splined drive end that goes into the shaft is held on with 6 small rivets.
And gazelle and a109 rotor link parts seem much lighter engineered than parts for a car. I know the materials and technology involved is far superior but it puts me off wanting to go in a heli!