http://edition.cnn.com/2012/08/27/us/nevada-air-race-probe/
Apparently the trim tab that came loose had an old lock nut that loosened up, and it was fixed in position relative to the elevator with a screw instead of being independently movable as normal.
And that my friends is why you never, ever, ever re-use lock nuts, lock washers, nylocks, etc, etc... 
Still hard to say.....in the report they claimed it was going 530mph.....which is much more than the airframe was ever designed for.
It was just the perfect storm of something going wrong, at the wrong moment, and at the wrong location. Small things like that most likely played a part, but who knows how many times it had been raced like that before without incident.
This is a film the NTSB released last week.
http://www.avweb.com/avwebflash/exclusivevids/ExclusiveVideo_JimmyLeewardRenoCrash_NTSBReportVideo_207264-1.html
From AVWEB
NTSB: Flutter Led To Reno Crash
Last year's fatal crash of a P-51 racing aircraft at Reno was caused by compromised stiffness in the elevator trim-tab system, which led to flutter and loss of elevator pitch control at race speed, said the National Transportation Safety Board in in its probable-cause hearing on Monday. At last year's race, veteran air racer Jimmy Leeward lost control of his Galloping Ghost P-51 after the home pylon turn, causing a sharp pitch up followed by a dive into a spectator area, killing him and 10 others. The NTSB's investigation revealed that the aircraft was flying faster than it ever had by some 35 knots, with higher engine power settings than previously used. The board also found that there was evidence of ongoing structural failure during the race, including a cracked canopy. Further, Leeward and his crew had made major modifications to the aircraft, including the removal of the P-51's iconic belly airscoop, that compromised the structural integrity of the fuselage. The crew notified the FAA of only one of these changes, a boil-off system used to improve oil cooling. The NTSB probe found that screws used to attach one of two trim tabs to the elevator were old or loose, possibly having last been replaced in 1986. This allowed the trim tab to flutter, failing the tab control rod and resulting in an instantaneous pitch-up moment that generated a calculated 17 Gs, which the board determined was beyond human endurance. In a video posted on AVweb yesterday, the trim tab can clearly be seen departing the elevator, but by that point, the control rod had already failed and Leeward had no trim control. The board had issued 10 safety recommendations in April, so the race organizers would have time to act on them before this year's races, and no new safety recommendations were issued on Monday.
NTSB Chairman Deborah Hersmann referred to the aviation writer Ernest Gann in her closing remarks, and said "Fate is no longer the hunter" for pilots who can rely on a wide range of safety advances that weren't available in Gann's time. Spectators at aviation events also need an assurance that they will be protected, she added. "Innocent bystanders should never have to rely on fate for their safety," she said.
Wow! I have worked on racecar teams and have been used to "nut & bolting" everything before practice/qualifying/race. I have also had to do preflight inspections when I was taking flight lessons as a teenager. I would think when you merge these two fields together into air racing, they would "nut & bolt" the aircraft, if not before every session, atleast before every event and do proper preventive maintenance.
Come on, 26 years for some nuts/screws on the flight controls of a machine that can go 530 mph?! I wasn't in airframes in the military, but I can only assume that these nuts/screws should be replaced every few years, tops.
It's pretty ridiculous that it took something like for someone to say "oh hey maybe we can't just let safety up to these pilots". As much as I want to trust the pilot, I also want to trust the system of oversight that keeps me safe (hopefully).
In either case, I'd be very nervous watching an air-race even with these changes.
PHeller wrote: It's pretty ridiculous that it took something like for someone to say "oh hey maybe we can't just let safety up to these pilots". As much as I want to trust the pilot, I also want to trust the system of oversight that keeps me safe (hopefully).
Please, not again.
PHeller wrote: ...As much as I want to trust the pilot, I also want to trust the system of oversight that keeps me safe (hopefully)...
Do you honestly think these guys are interested in killing themselves?! Problems at over 500mph 50 ft from the ground are very bad. I cannot see any race pilot willfully bypassing safety issues. All of these pilots are very high time pilots.
yamaha wrote: ....Small things like that most likely played a part, but who knows how many times it had been raced like that before without incident.
That was it's first race after extensive modification. I am sure it was tested and it did do qualifying but that race was the first time they really "opened it up". It was going about as fast as anyone has gone on the course at the time of the. Not surprisingly the problem happened at the fastest / highest stress point on the course.
NTSB: Flutter Led To Reno Crash ..."Innocent bystanders should never have to rely on fate for their safety," she said.
That's a bit of BS. There is pretty much NO way you are going to assure someone is perfectly safe at an air race. FAR safer then they are driving to the event, but no way they are perfectly safe.
I agree aircooled, I didn't know they had just put the beans to it this race......also, isn't this aerodynamic flutter they reference the same issue they discovered back in the 40's when in a steep dive? Something about the inner edges of the wing approaching the machine barrier and creating a bubble over the tail's control surfaces. I only ask, because AFAIK, the p38 and p51 were the only two with this issue.
Flutter is usually an oscillation of the control surface due to flex in the linkages and structure around the control surface. Kind of like the high speed wobble you get in a badly worn front end. It's extremely destructive to an airframe. There is a fair chance that's what caused the wrinkle in the tail section that showed in one of the earlier pictures. At those speeds, the time from flutter to failure is probably measured in milliseconds. Unfortunately when people push the limits, bad things happen. Racing pushes the limits. If you can't stand the risk, don't go to the races. You probably better not drive to work either.
Back when I was flying RC planes, I've seen flutter rip the entire tail section off airframes. It usually happens in a dive, but overpowering a plane will cause it too. In the quest for speed, special attention had to be paid to control linkages and stabilizers. Any flex would spell disaster. We started using carbon fiber kite rods with ball joints for push rods and as stiffeners in the tail sections. No flex, no flutter...usually. Then there is always the usual trade off. Do I build it light, cheap or strong? Pick two.
All airplanes are subject to flutterat airspeeds beyond that which they are designed for. The WWII fighters had a bigger problem with compressability as they approach the speed of sound. the following film illustrates flutter. A very well respected test pilot that I know says that this Twin Commanche is within 4 or 5 knots of losing the tail.
http://www.youtube.com/watch?v=pEOmCkZyXzk
aircooled wrote: Do you honestly think these guys are interested in killing themselves?! Problems at over 500mph 50 ft from the ground are very bad. I cannot see any race pilot willfully bypassing safety issues. All of these pilots are very high time pilots.
Did not the NTSB report state that the pilot's crew had been alerted to improper/loose bolt multiple times?
PHeller wrote: Did not the NTSB report state that the pilot's crew had been alerted to improper/loose bolt multiple times?
Not alerted, but that the crew had retightened the worn nut multiple times, and that the fracture showed evidence of having existed for quite a while, perhaps years.
This is a transcript of the oral report. This is mentioned on pages 8-9 and 13-14. http://www.avweb.com/pdf/ntsb-jimmy-leeward-reno-probable-cause.pdf
People are focusing on this as the problem. While it is a major problem, it was far from the problem. This tab itself was modified and damaged, the other was locked in place. The plane had numerous other rather questionable modifications. This tab did ultimately bring the plane down. But the plane was in the process of bringing itself down already.
http://www.ntsb.gov/news/events/2012/reno_nv/index.html
http://www.ntsb.gov/news/2012/120827.html
pilotbraden wrote: All airplanes are subject to flutterat airspeeds beyond that which they are designed for. The WWII fighters had a bigger problem with compressability as they approach the speed of sound. the following film illustrates flutter. A very well respected test pilot that I know says that this Twin Commanche is within 4 or 5 knots of losing the tail. http://www.youtube.com/watch?v=pEOmCkZyXzk
Compressability......that was the word I was thinking of. Thank you, remembering that term was bugging me.
In reply to PHeller:
So what you are saying is, once again to put things into your perspective of comprehension, you wonder why the equivelant of taking your 60+ year old modified car to a dealer for a nut and bolt safety inspection didn't prevent this from happening? Your point on worn fasteners is still invalid as those were not what failed.
In reply to Aircooled:
Is it possible that the second trim tab that was fixed in place was due to the fact it was an air racer? At the higher speeds, I could understand wanting to limit turning radius due to Gforce. Only reason I can come up with to limit a control surface.
foxtrapper wrote: The plane had numerous other rather questionable modifications.
So what your saying is as a spectator, I should worry.
What worries me about air racing is that as a spectator, aside from watching behind a huge net or inside a reinforced building, if your close enough to watch the race with any excitement, your in the danger zone.
Compare this to a racing event where walls and fences can protect spectator. If a racer makes some questionable modifications, he only puts himself and other racers are risk. At least the racers are prepared for accidents to happen.
At an air-race, the spectator isn't really prepared for a several thousand pound vehicle to come crashing down on them.
Am I saying the event should be banned? No way. It's way too cool for that. Am I perfectly fine watching it on tv? Yep.
PHeller wrote:foxtrapper wrote: The plane had numerous other rather questionable modifications.So what your saying is as a spectator, I should worry.
As a spectator you should always be worried.....
yamaha wrote: Is it possible that the second trim tab that was fixed in place was due to the fact it was an air racer? At the higher speeds, I could understand wanting to limit turning radius due to Gforce. Only reason I can come up with to limit a control surface.
I suspect (don't know) that the reason they fixed the one tab was because the trim forces on a plane going that fast (the center of lift shifts as speed increases) can be rather extreme and they wanted to reduce the forces on the movable one. So essentially, the fixed tab was probably a safety modification to avoid pretty much the exact situation that happened.
Regarding safety at the event: Certainly there is very little you can do to keep planes from crashing into the crowd, much like an airshow. If you look at the size of the course though, you will see that the percentage of the course occupied by people is very small. Add to that the fact that a good percentages of crashes will likely be under some sort of partial control it reduces the chances further.
Considering that, the airshow portion of the races and standard airshows are likely as dangerous or maybe even more dangerous then the races. Do we need to stop airshows for public safety?!
Bottom line, spectators need to realize some sort of risk and frankly it would be nice to see something that isn't totally sanitized. A lot of the thrill of the race is seeing and hearing the planes go by so close. If you have ever been "buzzed" by a plane, you will know what I am talking about.
pilotbraden wrote: All airplanes are subject to flutterat airspeeds beyond that which they are designed for. The WWII fighters had a bigger problem with compressability as they approach the speed of sound. the following film illustrates flutter. A very well respected test pilot that I know says that this Twin Commanche is within 4 or 5 knots of losing the tail. http://www.youtube.com/watch?v=pEOmCkZyXzk
Re: that video: 
PHeller wrote: So what your saying is as a spectator, I should worry.
I'm pretty sure I said no such thing.
Life presents risks. Decide for yourself which risks you are willing to accept, and which you are not.
PHeller wrote: It's pretty ridiculous that it took something like for someone to say "oh hey maybe we can't just let safety up to these pilots". As much as I want to trust the pilot, I also want to trust the system of oversight that keeps me safe (hopefully). In either case, I'd be very nervous watching an air-race even with these changes.
pilotbraden wrote: All airplanes are subject to flutterat airspeeds beyond that which they are designed for. The WWII fighters had a bigger problem with compressability as they approach the speed of sound. the following film illustrates flutter. A very well respected test pilot that I know says that this Twin Commanche is within 4 or 5 knots of losing the tail. http://www.youtube.com/watch?v=pEOmCkZyXzk
I'm glad I wasn't in that thing. Even the tail skin is buckling.
I didn't go to Harvard or Yale or anything, but it seems that the specators would be safer inside of the circular race course than they would be on the outside of the circle as they were at Reno, due to simple centrifugal force if anything goes wrong.
In reply to aircooled: With the a10's stationed in Ft Wayne, like clockwork at 9am, a group or 2-4 will make mock attack runs on our farm buildings.....one morning as I was getting ready to head to work one made a run and a banking turn right over my house under 500ft.....I waved as I could see the pilot clearly....he circled back around and gave a waggle of the wings. Those planes have the roar to them only when close and the shrill shreaking of the fanjets as they pass........such a beautiful noise. Much better than the f16's that used to be in ft wayne
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