Hangar Flying => Hangar Flying => Topic started by: Drew on June 29, 2005, 08:20:01 PM
Title: Bird Strike--in the news section
Post by: Drew on June 29, 2005, 08:20:01 PM
Are you sure it was a birdstrike? I don't see any evidence of blood/feathers (unless you cleaned it up). With the prop chewed up and the right aileron scuffed, I'm almost wondering if you shook/failed a piece of your prop, throwing it radially out towards the winglet----and scuffing the aileron in route. You would feel the vibration from the unbalanced prop. You then may have way oversped the unbalance prop, shaking the otherside loose.
Just guessing----and trying to figure out how all the evidence fits together.
Title: Bird Strike--in the news section
Post by: rglos on July 01, 2005, 12:46:13 PM
Jesus Eddie, your pucker factor must have been off the scale.
Both blades as well. Both blades at about the same point.
I have to agree with Drew though. I had a bird renting out apartment space on top of the engine and decided to leave only after I was crusing at 120 Kts.
It scared the hell out of me for what was a only few onces of blackbird. The engine shook bad until I cut power, then the vibration went away so I returned to the airport.
I can't imagine anything big enough to do this. I had blood all over the back of the blade and cowls in small droplets.
But once the blade strikes the bird, it throws it off ie it would not be there by the time the other blade comes around.
Maybe the blade broke free and the second one came around and hit the first one.
If is was a bird especially one big enough to do this, you will have lots of blood evidence.
Note: All the blood on mine was on the back side of the blade and on the lower cowl- I would not have expect blood droplets to go forward-go figure.
The pictures were well documented.
Thanks for sharing this with us & glad you got home safely
Rick
Title: Bird Strike--in the news section
Post by: longezdrvr on July 02, 2005, 03:14:02 PM
Hey guys just read the news and saw the pics on the "bird strike" I work for Southwest Airlines on the ground and have seen plenty of bird strikes we even had a 737 hit 5 snow geese what a mess that was. birds are very dense animals disspite there hollow bones they do an awful lot of damage at 200knts when you smash one. But ,there is absolutely no doubt that you hit a bird, it is a bloody mess. Even a sparrow leaves a greese mark. So no blood no bird. From the looks of the fiberglass on the winglet the geometry may suggest that your prop failed if you consider what you have. A broken prop, and a broken winglet. The only problem I'm struggling with is. The props natural coning is away from the winglet also you are moving away from the prop when it fails. So, I would agree that maybe the prop failed and before it actually fully departed it was struck by the opposing blade doing its best barry bonds into your winglet.
Tony
Title: Bird Strike--in the news section
Post by: Anonymous on July 02, 2005, 10:50:30 PM
The only problem I'm struggling with is. The props natural coning is away from the winglet also you are moving away from the prop when it fails. So, I would agree that maybe the prop failed and before it actually fully departed it was struck by the opposing blade doing its best barry bonds into your winglet...
Well, let me see if I can re-calibrate your intuition with some first hand experience (and some hand-waving physics).
A few years ago I had a small piece of music wire fall out of the back of the cowl, in flight. It was "U" shaped, with a total length of approximately 6 inches and a diameter of 1/8 inch. It fell more or less straight down for several feet before it was blown back approximately two inches to come into contact with the leading edge of my 62 in. diameter, B&T prop, hitting it ~5 inches from the tip. The wire cut a nice notch in the urethane leading edge material almost exactly to full depth, and only slightly crushed a small amount of wood directly behind the urethane LE at the impact point. The wire then ran roughly straight across the face of prop, leaving several significant gouges but nothing close to serious structural damage in it's wake.
The outer 6 inches of Urethane leading edge, since it had been disconnected from its inboard self, decided to come off. (Note that the leading edge on a B&T prop curves around the tip of the prop to the cord line, which is why 5 inches from the tip yields a 6 inch piece of LE; and that the LE urethane had a depth of about 1/4 to 3/8 inch where the wire hit.) As luck would have it, the LE piece impacted the left winglet almost exactly in its center. It made a goodly bang! There is absolutely no doubt that it was the leading edge that did the damage and NOT the music wire, because the LE left a perfect 'dusty "J" fingerprint' where it hit; and it was obvious that the LE piece hit the winglet almost flat. Think flyswatter hitting a table at ~800 fps and you'll have the picture. Despite wrapping around and cutting into the leading edge, the music wire was not much interested in flying outward after the hit, judging by its tracks on the prop face.
So what happened? The impact spalled the paint, primer and filler off of the winglet glass slick-as-a-whistle in a circle about 8 inches in diameter leaving a perfect, virgin glass surface that looked exactly like the day the glass was laid up. Zero damage to the glass, and zero damage to the finish outside the spall area. A little investigation, however, showed that the foam under the glass had been permanently crushed in about 1/8 of an inch in the vicinity of the impact point and (obviously) was debonded from the glass. An injection of flox slurry and local refinish fixed the damage.
So, that's ACTUAL experience, and now comes the hand waving (with sincere apologies to Joe Person with whom I agree on the undesirability of speculation).
Centrifugal forces acting on the propeller are huge (a significant fraction of the tensile strength of wood) in comparison to the trivial thrust loads (on the order of 100 lbf spread over the whole surface of the prop), which means that a piece of prop only wants to go straight out in the arc of the prop, not cone. (Think David's slingshot.) The most useful frame of reference moves with the plane, which places the winglet "in the line of fire", with a ~140 kt breeze blowing on the prop fragment, perpendicular to its motion, as it flies out toward the winglet. But the time available for this "breeze" to divert the flying piece of prop is practically nothing - (roughly 15 milliseconds at my guestimated 800 fps tip speed for the prop for a ~12 ft trip out to the winglet).
So here's my mental picture. In my case I had a fairly low-speed rifle bullet being fired in a 140 kt cross wind at a target a dozen feet away. I got lucky and the long, skinny "bullet" hit side-on, slapped the winglet and spalled off the finish. Yup, there was some wind drift, but not a lot. In Eddie's case he had a light-duty, cannon ball fired at the winglet. The result was about what you'd expect. Personally, I'm convinced that Eddie's "cannon ball" was a direct chunk of prop, and no chance that what hit the winglet was a either a "Barry Bonds bird" or "Barry Bonds prop chunk" (i.e., a secondary fragment). I'm inclined to agree with the idea that 'no sign of bird' suggests... no bird. But now I really am speculating, so I'll stop here!
Best,
Title: Bird Strike--in the news section
Post by: Dan Patch on July 02, 2005, 11:06:30 PM
But now I really am speculating, so I'll stop here!...
Oops, forgot to log on it seems. Since I don't much believe in anonymous posts, that should have been signed as:
Best,
Title: Bird Strike--in the news section
Post by: Drew on July 03, 2005, 06:54:52 AM
Went surfing around the NTSB NTSB site about the Dave Jones mishap and subsequently ran across this...
Identification: DEN05LA099 14 CFR Part 91: General Aviation Accident occurred Friday, June 24, 2005 in Santa Fe, NM Aircraft: Campbell Long EZ, registration: N84RW Injuries: 1 Uninjured.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.
On June 24, 2005, about 1000 mountain daylight time, a Campbell Long EZ, N84RW, piloted by a private pilot, was substantially damaged when it collided with a bird while in cruise flight approximately 5 miles west of Santa Fe, New Mexico. Visual meteorological conditions prevailed at the time of the accident. The personal cross-country flight was being conducted under the provisions of Title 14 CFR Part 91 without a flight plan. The pilot, the sole occupant aboard, was not injured. The flight originated at Double Eagle Airport (AEG), Albuquerque, New Mexico, and was en route to Los Alamos (LAM), New Mexico.
According to the pilot, he was cruising at 120 knots at 9,500 feet msl when he struck a bird. The impact separated the propeller blades at midspan. One or both blades then struck the trailing edge of the right aileron, bounced off, then hit the right vertical stabilizer, which also separated in flight. The pilot made an uneventful emergency landing at Santa Fe Municipal Airport (SAF).
Title: Bird Strike--in the news section
Post by: rglos on July 03, 2005, 08:35:59 AM
I took a second look at the images. From the top left the 2nd & 3rd shots are interesting.
The 2nd shows a large smudge on the front surface but the scratches are not following the rotation of the blade.
In the third shot, take a close look at the wood fibers. They are all straight.
If you strike something that fast with woodand it breaks, wouldn't you expect the fibers to be bent toward the clockwise direction. ( The prop is rotating CCW from this view)
Maybe it's just me, but the wood just looks old. Anybody else notice this?