"Galloping Ghost" crashes at Reno Air Races

[Raindance 25]

"..is each elevator actuated by it's own bellcrank for redundancy?" Of course it would only be redundant if you had two cranks on a single shaft, otherwise there would be two potential failure points rather than one. It would be easier to just make everything stronger. On a different subject -- danger to spectators, I can't imagine that moving them further away would reduce the potential hazard to spectators from an out of control plane in the least, unless they were so far away that they'd need binoculars to see anything meaningful, unlike F1 where a strong enough barrier will stop a speeding car. The only hope is that it would give a (conscious) pilot more time to avoid the crowd if control was lost for some reason.

[scott967 62]

I assume you mean with the modifications made to these aircraft. Stock these planes were never designed to fly at the speeds in this race. Also remember they are over 60 years or more old!!

Yes. Though we don't know how much of the original aircraft was still present. I would think the original design was based on a designed power output, wing design etc, not at all what these unlimited class configurations have. And I suppose in WWII they maybe were willing to allow for some possibility of failure that wouldn't be acceptable in peacetime. But when another racer has what looks to be a similar failure mode, well that's something I think an engineer would want to look at. scott s..

[scott967 62]

On a different subject -- danger to spectators, I can't imagine that moving them further away would reduce the potential hazard to spectators from an out of control plane in the least, unless they were so far away that they'd need binoculars to see anything meaningful, unlike F1 where a strong enough barrier will stop a speeding car. The only hope is that it would give a (conscious) pilot more time to avoid the crowd if control was lost for some reason.

I saw some data suggesting that the facility met the requirements of FAA order 8900.1 3-151. In particular the section of the race course along the primary spectator area is designated the "show line" and 500' separation is required. In addition, a "scatter distance" is required to be computed for each class of aircraft and that distance must be applied for the "critical turn". In Reno's case the distance from the critical turn to the primary spectator area was 5000'. It seems like the criteria were developed based on the possibility of things falling off the race aircraft, and not on loss of control of the aircraft itself. scott s..

[Raindance 25]

"..I suppose in WWII they maybe were willing to allow for some possibility of failure that wouldn't be acceptable in peacetime." Quite likely I should think, at least in the sense that the planes would not be designed to have the long life expected in civil aviation. I'd have thought, though, that they would have been designed to cope with the sort of maneouvres that aerial battles would necessitate. So strong, but maybe not built to last. Just speculation though ;)

[Jeff Smith 0]

Nothing really new here, but here is the preliminary report from the NTSB... http://www.ntsb.gov/...917X22412&key=1

[scott967 62]

Sounds like they might recover some data, hopefully useful in the investigation. scott s..

[Bearracing 3]

I saw some data suggesting that the facility met the requirements of FAA order 8900.1 3-151. In particular the section of the race course along the primary spectator area is designated the "show line" and 500' separation is required. In addition, a "scatter distance" is required to be computed for each class of aircraft and that distance must be applied for the "critical turn". In Reno's case the distance from the critical turn to the primary spectator area was 5000'. It seems like the criteria were developed based on the possibility of things falling off the race aircraft, and not on loss of control of the aircraft itself. scott s. .

First of all, I'm no expert on the rules and regulations pertaining to air shows and/or air racing, but as is to be expected, we've been getting a lot of information on local television and radio about the crash a week ago at the Reno Air Races. With that in mind, I am only repeating what I have learned from those in charge of the Reno Air Races and from the FAA, as has been discussed over the last few days. They explained that in the specific case of the Unlimited and Jet course layout, the critical turn is mid-way threw pylon 7, with the distance to the most western grandstands is 5,200'. The minimum distance for the "show line" is 500', but Reno maintains a minimum 1,200' separation distance. There are two considerations for their determination of scatter, one is "scatter distance" (based on the average known aircraft race speed and average race altitude at the critical turn) and the presumed "scatter cone" in the event of a crash (relating to an expanding debris field from the point of impact). The Jets run a rather short course to keep their average speeds below 475 mph, while the Unlimited "Gold" classification aircraft run a longer course, where they average 475 - 505 mph. (in 2009, an Air Force F-16 completed a lap on the Unlimited course at an average speed of 612 mph) In all, there are 3 courses for the 5 classes (sport plane, sport biplane, formula one, jets, unlimited, and AT-6), with the sport biplanes & formula one on course 1. Jets, AT-6, and the sports planes run on course 2, with the Unlimiteds running on course 3. Pylon 7 and 8 being the only common pylons listed as being the critical turn for all 3 courses. The accident involving Jimmy Leeward's "Galloping Ghost", a highly modified P-51, was outside any of their prior computer modeling, as this accident scenerio had never been considered or anticipated. They are considering future regulation modifications, including a redesigning of the trim-tab system on those aircraft exceeding 300 mph (or some speed to be determined later) and the application of a dead-man throttle switch or control on "all" race aircraft. Steve (Bear) CartwrightReno, NV

[Guest jahman]

...They are considering future regulation modifications, including a redesigning of the trim-tab system...

Assuming the trim-tab caused an elevator assembly malfunction and not the other way around, as it could very well be elevator forces exceeed design forces when the aircraft wings ae shortened. Cheers, - jahman.

[mgh 89]

Why would pulling the same g with cropped wings necessarily increase the elevator forces?

[Raindance 25]

Why would pulling the same g with cropped wings necessarily increase the elevator forces?

Perhaps because with cropped wings the plane would have to fly faster to maintain the same lift, consequently pulling higher G forces in tight turns. Just guessing though.. Scratch that. Jahman's point (previous post) was that shortening the wings was done so that the aircraft could pull higher Gs -- important in a race -- but maybe the elevator was not correspondingly strengthened.

[mgh 89]

Pulling higher Gs requires more lift. How would cropping the wings - reducing wing area - help to achieve this?

[Guest jahman]

As I said in my original post, the wing is a cantilever wing, so if you make the wing shorter the wing spar is also shorter, and given the same internal structure the shorter the wing spar the more weight it can bear. With a shorter wing you can also fly faster because flutter-inducing aeroelastic effects will also be reduced because, given the same internal structure, a shorter wing is also stiffer. Cheers, - jahman.

[mgh 89]

If you shorten a wing then, yes, with the same total lift here will be a decrease in the root bending stresses. But the root shear stresses will be unchanged, and the stresses on the skin panels and attachments will increase because of the increased wing loading (lb/ft²). If you then increase the lift there will be an increase in all three stresses. The lift can't necessarily be increased by shortening the span.

[KevinAu 441]

I'm not following how the cropped wings have anything to do with the crash. As we all know, the elevator trim sets the speed for the plane. These planes are trimmed at speeds the NA engineers probably never imagined the plane would be sustainedly trimmed at. That means that tab is set at deflections higher than it was originally designed to be at. That could be simple reason enough for these tabs to keep breaking like this at the races.

[mgh 89]

I'm not sure I'm folloeing it either. On a slightly different point, who in the USA is responsible for maintenance and ensuring airworthiness of such aircraft? In the UK, such aircraft are only granted a Permit to Fly - not a full Certificate of Airworthiness. Also, maintenance, continued airworthiness and Permit-to-Fly renewal of this type ex-military aircraft are to be controlled by a suitable CAA approved BCAR A8–20 Organisation