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10 comments:
Elevator and its trim tab had to take more force because
a) high G in the turns, and
b) the plane had been shortened by 10 feet, so less leverage.
Stu (CFI)
It is a sad day when a pilot or plan is lost.
The P51 does not to my knowledge have hydraulic assist to the controls it's done by human and a secondary flying tab that uses the airflow to make the elevator want to work with less force. Loose what I assume is the trim tab and trim is manual and heavy, loose the airflow assist tab and your fighting it and the stick will be hard to move. Additionally I believe the trim tab is coupled to the aeroassist tab making pitch control stiff and high operating forces. Add G forces and the inverted roll and it's going to be a bad day.
The plane was not shortend by 10ft.
The fuse is the normal length and The after deck is P51A (no rearward vis) style to provide better fairing. It had the wings clipped to 28ft and some inches (37ft is nominal).
See
http://www2.leewardairranch.com/racing/galloping-ghost-specs for detail.
Eck!
I couldn't find anything about when in the flight the image of the trim tab coming off was from. I assume it's from right before the crash, and the relative orientation of the plane makes me think it's from after it had pitched up and had begun its roll. So if the trim tab was the problem and the pitch up was a consequence, is it reasonable that the tab broke before the pitch up but didn't completely detach until the roll? (This isn't a rhetorical question; I really have no idea. My thinking is just that if it *is* reasonable, then OK; but if not, then what.)
That's what I'm wondering. What kind of elevator stick forces are generated in a P-51 at 450-500 knots, and whether the pilot would have enough muscle to overcome those forces if the trim tab broke off? I have no idea, but when I was training USAF pilots in the T-37 in the mid-1970s, my runaway trim technique was to take control of the airplane for a few seconds, and while I was pretending to be doing something else I'd run in full up or down trim, then hand the aircraft back to the student. I never experienced uncontrollable stick forces at any speed. But the dynamics on a modified P-51? Like you said, I wouldn't be surprised either.
I am wondering why the tail wheel was extended. It should have been retracted in the qualifying race.
Leeward was in second place when he declared Mayday and pulled up. That pull up was probably due to the nose-down trim the tab was otherwise providing to offset the the trim effects of high speed. The other tab was still there and may have contributed to the barrel roll.
It's been a while since I was schooled (informally) in Warbird control tech...but I think that the part which detached is called a "servo tab"...not to be confused with the "trim tab" next to it.
With a given control stick movement, the servo tab (or, colloquially, "flying tab") deflects opposite direction to create aerodynamic force on the trailing edge of the control surface which reduces the stick pressure that the pilot must exert to move the actual control surface. Servo tabs developed as planes got bigger and much faster toward the end of the "Golden Age" of the twenties and thirties.
I can imagine that the stick pressure at 4-500 mph without the assistance from that bit would be extreme. Having only a couple seconds to figure it out...perhaps with unbalanced forces on the horizontal stabilizer also creating the roll moment and/or jammed linkage due to missing/fouled parts, and high G-load...Jimmy Leeward had a problem that could easily called unsolvable. It must have been a God-awful ride for that last few seconds.
In view of Eck's comment, I withdraw ma remark b.poinedly
In view of Eck's comment, I withdraw my remark.
Goddamn comment SW screwed up my previous try :-(
An unpleasant thought...
These old warbirds are 65+ years old now. Yes, they're lovingly, even obsessively, maintained. But they're *old*.
I regularly ride with some Jeepers who are into the old classic CJ5/CJ7 series from the 1970's, the ones from before Consumer Reports made AMC put wide axles on it and eventually discontinue it in favor of the Wrangler. They are just as obsessive about their maintenance. Yet every trip, something breaks. 40 year old wiring frays and catches on fire, a leaf spring breaks at the eyehole where it bolts to the body bracket, the frame cracks at the steering box mount. Mechanical crap just ain't meant to last that long.
Thing is, those CJ's are on the ground, and all that happens if they break is that they stop moving -- we can pull them out with winches and tow straps or even weld them back together right there on the trail (yes, we have a guy with a welding rig on every run). But if something breaks on an aircraft, this is what you get -- not only a pilot dead, but innocent people on the ground maybe too. I'm wondering whether it's just time to hang it up for these old WW2 warbirds. Yes, putting them on static museum display or scrapping them seems a sad fate. But everyone dies, in the end, and everything, eventually, is destined to become dust. Raging against that fact is like raging against the rain, futile and of little purpose.
- Badtux the Mechanic Penguin
Asymmetrical control surfaces are never a good thing.
The poor pilot never stood a chance.
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