rotor/accident ?

[tx_swordguy]

I am just curious about this. I have only read about one incident involving a problem caused by rotors them selves. It involved a wide cord rotor on a gyro that basically over ran itself and had a rrpm in exess of 400. It was not a fatality. my question is this. how many of you are flying with less than brand new perfect condition rotors? I am not talking about rotors having obvious cracks or severe creases etc. I am talking about rotors that may have had a hard landing, a minor blade flap issue, ding from hanger door, dimples from various reasons that are only seen from certain angles. Basically minor imperfections that are in your blades. Or are you only going to fly with perfect blades and if so why? I have seen several pics of damaged blades that some have said trash and others (including manufactures) have said are completely safe with a minor change in aerodynamics. Most of the accidents I have read about are pilot created, weather created, medically created. I have not found (doesn't mean they arent there) a report of a gyro down due to mechanical/structural means (other than engine out obviously). It seems that our blades can take alot of abuse and keep going.

 

[phantom]

wide cord blades turn slower and the only way to make a rotor on a gyro speed up is to load it more and it will not run away, a rotor that is over balanced may feel weird to handle and a rotor that is under balanced can flutter or in some load/ speed conditions do an uncommanded flare but when you hear of a runaway rotor it was likely to be a rotor tach error. I have tested very wide blades and they were very rough and had very high stick forces but did not run away any more than narrow blades.

Norm

 

[WaspAir]

It involved a wide cord rotor on a gyro that basically over ran itself and had a rrpm in exess of 400.

My J-2 flew at around 425 rotor rpm all the time, with 26 foot diameter, so 400 rpm (without more) doesn't sound excessively fast in general.

And by the way, I am always very touchy about the condition of my blades on any rotorcraft, and don't even like having bugs on the leading edges.

In my experience, cleaning blades contaminated by bugs and such on an R-22 can cut the hover power required by half an inch of manifold pressure.

 

[Gyro28866]

Hello Mark:
I think the area where the ding is located will help determine if the blade is ok to fly or a paper weight!
There are a few dings on the bottom of my Dragonwings. They were appearently handled a little rough on the saw horses. These "dimples" which cover most of the cord width of the blade; are only on the botom. The blades fly just fine.
When the blades are flying, the lower skin is in contraction, so the lower skin is being "stretched" per-say. The minor ding is being streched, and does not present a structural problem.
However; if the ding was on the top of the blade. The top skin is in compression, when in flight. This ding may be all that is needed to allow a compromise of the longitudinal integridy of the blade, when in flight. And the blade may fold/break at the "ding" compromised area.

Do this test!!!
Get you your favorite beverage in a can.
Open and drink the beveage, being careful not to "ding" compromise the integrity of the side of the can.
After you finish your beverage.
Place the can on a secure surface, such as the concrete floor.
Slowly and carefully, place one foot ontop of the can.
slowly step up onto the can, balancing on the one foot; the can will support your weight.
Now, understand the sides of the can are in compression.
Now, slowly reach down and use the index finger of both hands to simutaneously "ding" the sides of the can.
This will impress upon you, how quickly the compromised material can fail!

 

[Ernie_B]

blade scratches/gouges

blade scratches/gouges

If there is a crease/scratch on the blade running from front to rear(leading edge.*to trailing edge) on the top and especially the bottom of the blade DO NOT FLY THEM!!!!!
On a tall tail type machine , the blades cross over the top of the tail at a place in the blade that has the max. amount of stress/ bending!
IT WILL BREAK OFF there at some time!!
Could be in a few minutes or a few hours , BUT IT WILL BREAK OFF!!!
You WILL NOT LIVE, if this happens, EVEN on a fast taxi!!
An oil can type dent MAY be OK, but NEVER a gouge/crease from LE to TE!!
I hope this clears this issue up
DON"T FLY THEM!!!!