22 blade failure

[imabell]

this photograph is of a blade with less that 300 hours on it. the pilot felt an increasing vibration and a strange sound . he was very low at the time and this probably saved a serious incident from more dire consequence.

i, and many others, always thought that the robbie blades were a one piece constuction joined at the trailing edge. now i know better.


http://www.bluetonguehelicopters.com.au/pprune/tip.jpg

[Nigel Osborn]

From the paint erosion, it looks like he has flown through a lot of bulldust?:confused:

[sir.pratt]

and for 300hr blades, those end-cap screws look like they have had a hard life

[EMS R22]

Did they leave a 0 off the end when recording the hours !!!:confused:

[Head Turner]

Something wrong here! Looking at that blade the surface erosion of the failed laminate does not tie in with the small amount of erosion of the tip plate leading edge. Could be that the blade has been cleaned with some chemical that debonded the blade.

[heligreenhorn]

mabye some smart guy tried to put some type of buffing wheel on the leading edge after cleaning them with wax/cleaner
mabye the heat created by siad wheel caused the debonding
i also thought the blades were bonded at the trailing edge
watched them do it at the factory??????

[IFMU]

I have a slice of an R22 blade in front of me. The front is an extrusion, the top and bottom skins are two seperate pieces bonded to the extrusion, to each other at the trailing edge, and to aluminum honeycomb in the middle.

-- IFMU

[Graviman]

Can't comment on incident. I'm slightly suprised there isn't a groove designed into the extrusion for the top & bottom skins to tuck into. The skins look like aluminium to me. The discontinuity could then be sealed, to avoid tripping up the air flow. It just strikes me that bonding without some means to avoid peeling failures will at best limit design life.

BTW, as an aside does anyone know which CAD/Analysis packages Robinson use? No bearing on this thread, i just wasn't sure in conversation a while back.

Mart

[Twiddle]

CAD/CFD: Lick of a pencil and the back of an envelope......

Ah - that'll be the -5 blade then Sir...... Ka Ching.....

[IFMU]

I'm slightly suprised there isn't a groove designed into the extrusion for the top & bottom skins to tuck into. The skins look like aluminium to me. The discontinuity could then be sealed, to avoid tripping up the air flow. It just strikes me that bonding without some means to avoid peeling failures will at best limit design life.
Mart

Mart,

Robbies aren't the only ones with blade construction like that. Enstroms also have an extrusion in the nose (solid, heavy) and a top and bottom skin bonded on. Both the robbie and the enstrom have a step in the extrusion so the aluminum skin is flush with the nose, so it doesn't trip up the airflow unless it looks like the one in the beginning of this thread.

In my co-worker's collection there is also a metal bell blade, from a 47 I think. It has similar construction but then there is a skin that wraps around the nose up to about 1/4 chord or less. There is also a 300 blade, and that's like a 1-piece taco skin that wraps all the way around the extrusion in the front. Pretty nice design if you ask me.

I've heard some people say that "If it stays together it was bonded. If it comes apart then it was glued."

-- IFMU

[Heli Sport]

Imabell can you confirm that these blades are the new design that have been fitted this year?

The blades do seem to look like they have done over 300hrs going off the ware on the tip of the blade in view :suspect:

Also have heard a rumour that an Oz operator has been caught recently still having the old design of R22 blades still fitted to his helicopter and still flying. Won't say who but surely if this is true I wouldn't like to be in there shoes. Has anyone else heard anything about this? :=

[bellfest]

The blade to me looks like it has not done much more than 300 hours by the look of those caps. As for the stainless screws, that would only take one apprentice one balance with an old screwdriver tip to do that. The pilot obviously doesn't mind the dust but older blades not only wear the leading edge of that cap down, they erode a lot more paint further in from the tip. A good mustering pilot will have blades that look like that after a 1000 hours, one who is not so concerned or aware of what you see in the picture (just the erosion I mean) will do that quite easily in 300.

[Helijo]

from the wear of the paint it looks like a lot more than 300 hrs....unless operating in real dusty conditions..still thats scary as hell :eek:

[born2fly_au]

In my opinion i think it is about time Mr Robinson went back to the drawing board when it comes to the design of his rotor blades in both the R22 & R44. I cannot recall hearing of so many blade failures in one make or model before. maybe it is time to look at composite construction.