what part does not look up to the job

[bugdevheli]

nearing completion of a little rotary project, i was looking at some components and asking myself the question. what would be the result of a failure of this particular part. What parts of your machine do you look at and wonder, " what if " . for example r22 flex plate Bug.

[birrddog]

Following on from the active threads...

The main gearbox!

[TRC]

What parts of your machine do you look at and wonder, " what if "


Just about ALL of it - on the ground pre-flight.

BUT,

I found out a long time ago to never look at the rotating bits in flight - out of the skylight of a 206 at the main rotor hub, or out the back of a 47 or an Alouette II and see just about everything thrashing round........... horrible.

[Hughes500]

How about the whole R22?

[SASless]

For way too many years I always had a feeling I would see a Main Rotor Blade zinging off into space at the Two O'Clock direction.:uhoh:

Don't ask me to explain that....as there is no logical, sane, rational reason one would ever arrive at that thought.

What is odd....there are a few aircraft I feel quite safe in re mechanical design.

105 and 117's spring to mind. :ok:

[T4 Risen]

All the moving bits, metal bits and electrical bits, other than that im pretty happy:ok:

[FLY 7]

The nut that holds the cyclic :eek:

[Fark'n'ell]

How about the whole R22?

Now we are starting to get somewhere.:ok:

[ChopperFAN]

This is a good way to discuss flaws or under engineered things...

I like all the as350's... But when I look at photos, see through drawings of the airframe, and how its only a floor with a rear firewall with a gbox loitering just overhead, in an accident they almost always end up with no roof and the seats hanging out

Thin floors on helicopters like the 206... isnt that a wee bit dangerous for many landings in remote locations? I have always had concerns about random fencing posts or cut stumps in long grasss injuring someone

The way cabin sections are constucted really scares me... Helicopters are usually all engine and drivetrain, and crew safety should be most important...

Isnt there a way to make the cabin area altitude pending ejecting capsule with stronger alloy frame with chute to slow its decent, and mount the driveline ant tail together so it will land clear off the crew

If youre in the dead mans curve then it wont help much, but if a major component failed in cruise and it all went sour with low autorotation chance i would love this option...

It may be a little far fetched but its 2009... We really should have our prioritys right

Simon

I look forward to see what else worries u all :sad:

[Jonasraf]

Flying hughes 300,

The tail rotor loosens and flys through the cabin (and me). :\

[TRC]

ChopperFAN

I agree with you that the 350/355 cabin is pretty soft and doesn't give much protection to the occupants - the standard 355 fuel tanks aren't too crashworthy either.

I think you'll find that the cabin floor of a 206 isn't as thin as you think. It's about 1.5+ inches thick honeycombe.

Jonasraf

I think that's happened to a 300, can't remember if it was in flight or if it happened after a tailstrike at the bottom of an EOL. Anyway, a loose T/R blade was found with evidence of it having hit the poor bloody pilot. The odds on that happening very often are pretty slim I'd have thought.

[helimutt]

I was watching an S61 land yesterday and the size of the aircraft in relation to the part of the main rotor mast I could see!!!! :eek:

Although up close it probably looks much more substantial?

[VeeAny]

TRC

You are correct there are at least two reported cases of parts of the tail rotor coming through the back of the hughes 300, the one at Biggin about 18 months ago after striking its tail on the ground on take off, and one back in 1975 where the tail rotor broke apart in flight and a fragment hit the pilot in the back of the head and killed him.

I've edited the above to include the word parts just to clarify.

GS

[TRC]

....there are at least two reported cases of the tail rotor coming through the back of the hughes 300,....

Blimey, I'd have thought that once would have been a fluke......

[Matari]

I was always less than impressed with Bell swashplates. From 2-per vibes on the 206 to cracks on the 205/212 series, it seemed Bell could never quite get it right. Other ships I worked on, like the Sikorskys, BO105, Astar, Puma, etc. had much more robust swashplate designs.

[traumajunkie]

On a Hughes 300...

The single small screw bolt thing that hold the little wheel that the clutch cable passes through. Seconded..

[Two's in]

If you assume the fuselage will generally hold together, the transmission will probably take the load, the Main Rotor will remain effective and the engine will keep turning, you always come back to a single item.

The lift from the Main Rotor is transferred to the MRGB, and hence to the aircraft. So let's look a little closer at that transfer between Main Rotor and the MRGB. The Rotor Mast is the mechanical connection, but how does the load transfer from the mast to the MRGB? The mast effectively holds the MRGB while simultaneously being driven by the gearing, so how does that lift/weight transfer happen? In most cases the MRGB top bearing secures the gear drive on the mast which is in turn driven by the the gearbox. So during flight the entire lift/weight coupling between the Rotor and the Gearbox is a function of a single bearing. OK, it's a well engineered bearing, but it's still the difference between continued happiness and a less enticing outcome every time you commit aviation.

Sure all those other bits are important, but only like a big house and a pension plan are important when compared to oxygen.

[before landing check list]

Chopperfan,
Then you need a H500 or 530.

Jerry

[helofixer]

The aluminum chip detector housings/bodies used by Bell (made by TEDECO). In the past week we have had 2 different ones fail, thankfully discovered when changing the base o-rings during (1) an engine swap on the chip detector housing on a 206L4 Freewheeling Unit and (2)a lower detector on a 206L3 M/R gearbox. 2 different part numbers and styles with the same failure. The freewheeling unit one seperated completely when torquing the chip detector base (70-100 inch lb.) The base broke off and fell on the floor and the guts of it fell into the free wheeling unit housing.

Upon re installing our L3 main gearbox in the aircraft after an internal inspection, I could not get the chip detecting portion of the detector to engage and lock into the body. I changed orings, checked torque and could not get it to install. So I pulled the body and removed the oring and to my dismay saw a small hair line crack that was 3/4 the way around the entire circumfrence. When torquing against the oring and the xmsn case, the crack would allow the receptacle portion to move inside the gearbox not allowing the detector to be installed. Scary stuff seeing as just a few mm of aluminum is holding all your transmission oil in.

/
http://www.tedecoindustrial.com/3a7739.gif
/

both cracks were located between the hex portion on one side and the gap to the right of the threaded portion where the sealing o-ring rests.

[helimutt]

suggest you check your torque wrench?? :E

[Miles Gustaph]

...well I hate the expanding bolt on the tail rotor bell crank of the AS350/355's... anything that falls apart in your hand when you take it out cannot be good!

[ericferret]

Seem to think that expanding bolts are used to hold Hughes 500 blades on.

There has been at least one other H300 fatal in the UK due to loss of the tail rotor although it didnt penetrate the cabin, in fact it was never found.

I saw another 300 where the bolt was worn 50% through and the out of balance vibration had elongated all the TRBG flange mounting bolt holes to about twice their normal size.
The gearbox and flange had almost detached from the boom. The only way to remove the tail rotor was to cut the bolt out as it was so badly stepped.

Same system on the older 500's but I 've never seen a similar problem.

The original bolt was a cadmium plated steel bolt later replaced by a special bolt. I do not know if there have been further problems sice the modified bolt was introduced.

Reminds me of a story involving a friend of mine fitting a main rotor to a 205 in a field camp.

One of the oilrig guys was taking a lot of interest in the task. On discovering that only the "jesus" nut retained the whole system he offered to run a few beads of weld around the nut to beef it up a bit!!!!!!!!!! Clearly its not only pilots and engineers who sometimes wince a bit at the aircraft designers offerings.

[Sikorskyfan]

Anybody ever take a close look at what retains a 205/212 mast in the transmission?

[generalspecific]

saddle tanks with avgas sitting above a hot engine in my R44... not good in a hard landing.. hence why i always wear the growbag..

[Trans Lift]

MR blades departing on their own accord is definitely a worrying thought. As one of my ground instructors once said, "At that stage you'd have to fasten your seatbelts and enjoy the rest of your ride!"
Hadn't heard the stories about the 300's tail rotors before, scary stuff. I'll certainly be giving it an extra careful look tomorrow..............:ok:

[ericferret]

Not sure if you would have time to even think. A military 212 was reported to have exploded in flight by aircraft flying with it (Philipines?). Turned out that it shed a main blade.

[SASless]

For a while we had several CH-47A's that experienced a main rotor blade rotating 90 degrees in the cuff with an immediate disintegration of the aircraft.

I do not care to think what that ride would be like.....except hopefully the G forces of the aircraft coming apart would render you unconscious and you could then go in your sleep.

Not much use in cinching up the old seatbelt in that situation as there would not be anything to cinch to.

I used to have a nightmare where I found myself strapped in the seat...cyclic and collective in hand....and nothing else around but the clear blue sky.

Reckon it was the Anchovie Pizza's?