jrice45516
Heliman
Location: SoCal
| 3/06/02
~flite 360 Had a close call, the bird got outa whack, barely saved it near the dirt, dragged the headspeed down so far I could easily see the blades, but ignored it & flew out the tank. On next flight, 1st woof I've had in a long time occurred. For fear of an in-flight boomstrike, i did not try goosing the collective to get rid of the 2-3in out-of-track condition & instead just switched out of IdleUp into Normal Flight Mode & descended; woof would not go away until landing AND bringing the engine down to idle.
Bird History - over the 359 flight (including 21 crashes) lifetime of this particular bird, virtually all of the original kit parts have been replaced at one time or another so, in a many ways, you could say it's new. ;-) OS32SX-H new, KSJ exhaust, Sullivan 12oz FlexTank w uniflow fuel system w 1oz bubbletrap, new SAB 550's, GY601, QuickUK swash & collar, Geo's slider & his clutch (unshimmed) in a bell w stock liner shimmed out w paper, all sleeves/bushings are JB'd to their respective bolts, metal sideframe joiners, CF frame stiffener, all else stock except not running boomstruts nor horizontal stab.
step 1. My reaction to the 1st woof to ignore it & fly again. Woof repeated.
step 2. Bench check reveals flybar is no longer straight. Straightened by hand. One BK0006 Mixing Lever bolt has backed out so tightened. Flew again, woof repeats.
step 3. Further bench checking reveals
a) flybar is not straight & previous bending & straightening has left it soft. Just flying causes bends in it. Restraighten by hand.
b) the lower ball link of one PV0005 Control Rod (aka oval link) is noticably worn & loose on ball. Replaced.
Woof repeats next flight. Is occurring at random orientations during mild aerobatics.
3/09/02
step 4. Further bench checking reveals
a) the Rocket City links on one PV0040 Double Link are unwound enough that the double link cannot pivot freely. Fixed.
b) BK0030 Mainshaft Lock Ring (aka collar) has slipped on the mainshaft (happened in close call) allowing minor collective play in the rotor head assembly. Fixed.
c) spindle is slightly bent (happened in close call). Replaced.
3/10/02
Woof repeats on next flight.
step 5. Tried a new pair of SAB 550's. No help. I would have switched brands but have only SAB's on hand. ;-(
step 6. Dampeners might be bruised. Replaced with new, lubed with a non-petroleum grease. Woofed again.
step 7. The flybar bend slightly in normal flying hinting that the metal may be fatigued near the seesaw. The exagerated flapping action during woofing can't be helping this. I go ahead & replace the flybar. The bird woofs again but this time temporarily & disappears without having to land. I fly the tank out but the OS8 burns up & i've left my plugs at home. Will fly again before making further changes.
3/12/02
Flew two tanks this afternoon with no woofs.
3/12/02 Removed mainshaft which was not as straight as i thought. Found 2-4thou bend in that mainshaft. Replaced. Been meaning to shim out the up/down play of the maingear on the BK0023 One Way Clutch Shaft (aka autorotation bearing housing) so put a clutch shim under the bottom circlip; shim is 0.007in; these clutch shims are good for something after all. ;-) Next flight should be interesting. It will be the 2nd time I've tested the theory that wah-wah's are maingear-play related. First try had absolutely no affect on wah-wahing as expected but we'll give it another try just to establish repeatability.
3/15/02 Woof repeats near end of 3rd flight in low-altitude flip, land, idle 'til flapping disappears, take off, woof repests in high altitude roll. I have not mentioned that at no time is my headspeed near the 2000rpm that many people believe is a contributor to woof. My headspeed is not over 1800. This time after landing, I give a little back cyclic while bird is woofing at or near idle & get a boomstrike, thumbsize dent in boom, no damage to SAB due to low headspeed. Call it a mini-poof. Barely any wah-wahs today so jury is still out on shimmed maingear. Replaced both boom & bent spindle. Tightened up front aileron servo mounting screws eliminating some side-to-side servo movement - u know i really ought to do more preflighting. ;-)
step 8. Changed out bladegrips but not bearing assemblys (thrustbearings don't feel knotchy). Wah-wahs are still there confirming my earlier experience with reduced maingear play.
3/17/02 Woof repeats on 3rd flight in mild pirouetting flip.
step 9. Replaced bearing assemblies, not new but different; will try them next time.
3/24/02 No help. Woofs again.
step10. So changed out the entire rotor ass'y with a spare. Again no help. Ah, but Scott points out an embarrassing crack in BK0017 Coll Cntl Arm which has been there who knows how long & allows major flex.
step11. Replaced BK0017.
4/23/02 87 woof-free flights since replacing broken BK0017. After 18 woof-free flights, i switched back to the original rotorhead ass'y. Looks like i found my "woof." If so, i have also found a way to induce wooflike flutter (not that you'd wnat to). And also, i may have found a way to avoid it next time - take more time to check the bird over after something weird happens. We'll be watching. So far, wah-wah's unreduced by reduction in maingear up/down play (it is unfortunate that people have given the name wah-wah to 2 totally different problems). What does this whole episode tell us about woof in general? Not much since the vast majority of woof victims are/were not flying with broken Collective Control Arms.
ideas now irrelevant
- replace bearing assemblies with new?
- weak servo(s)?
- no, i would not bother with flipping the grips as i had an in-flight boomstrike on my original R30 after flipping; the stock amount of Delta is fine.
- just fugedabowded & build the spare bird.
- 3/23/02 glue the bearings?...hmm...we'll see...yeah, alot of guys have liked that. If so, might as well use JBWeld..in for a penny, in for a pound...i think grease & shields will keep it away from the balls...but how do u know they're gonna set up straight, as in aligned? I guess you could spin 'em while the glue is setting up...no...that sucks...or maybe it's not that critical...i know, hang the blade/grip/spindle/grip/blade from the ceiling by one blade tip overnight...that should be straight enuff.
wish list:
- a trued BK0003 Main Rotor Hub would go a long way toward making the R30 fly right. Mine have always had an airframe shudder & long pushrods of unequal length. An untrue hub is very possibly causing this.
I am updating this post periodically.
signed,
Dances With Woofs |
