RNO Air Races Crash

[WildcatFan]

The Fox news theory from a GA mechanic is disgusting. They even rotated the photo 90 degrees to fit their story. I realize this aircraft was highly modified but a stock Mustang seat, which I would guess is engineered to well in excess of 12 G, only adjusts in the vertical. The rudder pedals are adjustable fore and aft, not the seat. Typical lack of knowledge from a media organization in an attempt to get out in front of everyone else.

What's amazing is the quality and sharp focus of that photo (in a vertical dive). When I first saw it, I was convinced it was photoshopped and they forgot to erase the tailwheel, but apparently, it legit!

I agree. I doubt the seat failed and I doubt this aircraft has the control authority to fail the seat, but I consider it irrevelent anyway because an unexpected pull up in excess of 9 or ten G is enough to incapacitate the pilot. Fighter pilots sustain 9G only because they are ready for it. Even the G-suit doesnt help if you dont do your part first. You cant play catch up with 9 g's if you aren't on top of it first. Unfortunately, the pilot in the case most likely wasn't part of the equation after the initial pull up.

 

[charlie2]

I have personally experienced GLOC as a back seater in the F-4 during an airshow in El Toro many years ago. Going thru a divorce and was tired and only had coffee all morning are my excuses. After our part of the show was done the pilot reefed on more than the usuall G's during the overhead break and I didn't "wake up" until wings level on downwind so I'm estimating 4 to 5 seconds in la la land. It kind of looks like from high G pull up to impact it wast much more than that so I think you are right about the pilot not being part of the equation. I've always enjoyed those races and I think they will recover after this trajedy.

 

[Bringupthebird]

Todays WSJ echoed these sentiments. They're estimating a 10g uncontrolled pitch-up after the trim tab failed. That would knock out anyone. I would imagine that the seat would fail somewhere between 8-12g's as that would be more than enough for a pilot without a g suit. Also, strengthening a seat beyond that would add weight that they don't want to deal with.

Can anyone explain how a trim tab failure results in a 10G pull-up? How does the hinge fail before the bolt/bellcrank without taking the rear spar of the horiz stab with it. There's alot more area of the elevator trying to stay in one place than there is of the trim tab trying to move it.

 

[bubbers44]

My first thoughts too. Why couldn't he overpower the trim tab? Voodoo, an almost identical P51, had the same thing happen in 98 and pulled 10 G's with a much younger pilot and blacked him out too. He kept going up thousands of feet and as the speed fell off recovered.

 

[ackattacker]

Can anyone explain how a trim tab failure results in a 10G pull-up? How does the hinge fail before the bolt/bellcrank without taking the rear spar of the horiz stab with it. There's alot more area of the elevator trying to stay in one place than there is of the trim tab trying to move it.

I'll take a stab at it.

All conventionally rigged aircraft need more nose down trim the faster they go until you get into mach tuck regions. That's basic static stability, go faster the nose comes up. Remember that every stable aircraft has a basic speed it wants to fly which is determined by the position of the trim. If the trim tab is missing there's still a basic speed it wants to fly which is the same as a neutral trim position. Go faster than that speed it wants to pull up, go slower it wants to dive.

Unlimited warbirds are frequently modified with greater trim tab authority so they can go faster without running out of down trim. When they're going real fast the trim can be full down and applying considerable force to the elevator. Of course they may also play with the elevator incidence, maybe center of gravity to try to limit that, but fundamentally you need to make a compromise between high speed and low speed trim authority and basic stability.

The trim tab is servo tab applying force directly to the elevator not the bellcrank. When you're running at 490mph with the trim full down, the force on the elevator bellcrank is minimal. The force on the trim tab hinge is very large, it is forcing the elevator down and that's the thing opposing the natural tendency of the nose to come up. The elevator is fighting mightily to return to neutral, the trim tab is opposing it.

When that hinge fails due to the load, or the tab flutters and breaks off (which can happen in a fraction of a second), the elevator returns to neutral and suddenly the aircraft is nowhere near it's stable speed. It would require considerable down stick to hold the nose down. Maybe more strength than a man has. If you weren't right on top of it, the resultant pull up will knock you unconscious and the rest is history.

 

[HalinTexas]

The elevator is used to keep the nose up (more forward trim) as speed increases. Correct? While in a turn, more nose-up trim is used to hold the nose up? Correct? The question really is, What is that tab doing to the elevator while it's partially detached? Did it result in a control jam? What was the pilot doing with the trim while in the turn? Was he trimming? Remember, he was in a 70-80º bank, reference the other aircraft in the videos. Was the trim control jammed, and/or suddenly release, resulting in a pitch up. The other tab was still attached. Or, was the elevator jammed and the pilot using the trim, excessively, to try and trim the nose up while in the turn. I doubt we'll know until the investigators find that "magic BB." Lots of aerodynamics going on here that will make you dizzy.

As with most crashes, it isn't any ONE thing.

 

[HalinTexas]

I'll take a stab at it.

All conventionally rigged aircraft need more nose down trim the faster they go until you get into mach tuck regions. That's basic static stability, go faster the nose comes up. Remember that every stable aircraft has a basic speed it wants to fly which is determined by the position of the trim. If the trim tab is missing there's still a basic speed it wants to fly which is the same as a neutral trim position. Go faster than that speed it wants to pull up, go slower it wants to dive.

Unlimited warbirds are frequently modified with greater trim tab authority so they can go faster without running out of down trim. When they're going real fast the trim can be full down and applying considerable force to the elevator. Of course they may also play with the elevator incidence, maybe center of gravity to try to limit that, but fundamentally you need to make a compromise between high speed and low speed trim authority and basic stability.

The trim tab is servo tab applying force directly to the elevator not the bellcrank. When you're running at 490mph with the trim full down, the force on the elevator bellcrank is minimal. The force on the trim tab hinge is very large, it is forcing the elevator down and that's the thing opposing the natural tendency of the nose to come up. The elevator is fighting mightily to return to neutral, the trim tab is opposing it.

When that hinge fails due to the load, or the tab flutters and breaks off (which can happen in a fraction of a second), the elevator returns to neutral and suddenly the aircraft is nowhere near it's stable speed. It would require considerable down stick to hold the nose down. Maybe more strength than a man has. If you weren't right on top of it, the resultant pull up will knock you unconscious and the rest is history.

See, another theory. 5 minutes before mine. Entirely plausible, and probably more correct.

 

[Bringupthebird]

So Ack, you're saying that the entire airplane is riding on the bolt that holds the trim pushrod on? When I said bellcrank, I guess what I meant was the trim control horn, technically. Your explanation sounds plausible.

 

[Flopgut]

I've worked on and inspected my fair share of old airplanes. I'm not sure I'm 100% correct, but it might be time to park some of this WWII stuff? I know a good portion of the airplane has been replaced, but most of the mods are done to make it go faster. Racers might ought to be built from scratch and built just to race. The P51 was engineered to carrry weapons and fight.

 

[glasspilot1]

Ack, very well written explanation of how trim works. I think you hit the nail on the head; when that tab came off the nose came up so fast that he didn't have time to react before the G's took him out.

To HalinTexas, you trim for level flight, not for a turn. You're going way off the grid talking about turning and trimming.

 

[Fubijaakr]

I've worked on and inspected my fair share of old airplanes. I'm not sure I'm 100% correct, but it might be time to park some of this WWII stuff? I know a good portion of the airplane has been replaced, but most of the mods are done to make it go faster. Racers might ought to be built from scratch and built just to race. The P51 was engineered to carrry weapons and fight.

Exactly. Time to move on. Race F-86s!

 

[ultrarunner]

I've worked on and inspected my fair share of old airplanes. I'm not sure I'm 100% correct, but it might be time to park some of this WWII stuff? I know a good portion of the airplane has been replaced, but most of the mods are done to make it go faster. Racers might ought to be built from scratch and built just to race. The P51 was engineered to carrry weapons and fight.

I'd agree. With the INSANE amount of money and wealth these folks play with, they could easily design and build a purpose-built racing machine. Something that can actually tolerate 500 kts indicated and the associated G's!

 

[dustrpilot]

I was there also and saw the whole thing from the time of the initial pullup. My point of reference was the west side of the airport facing pylon nine about 100 yards away. He was coming around the last pylon when the aircraft snapped level and then violently pulled vertical, most likely 20 G's. That stress would have caused the tailwheel to fall out. My guess is that he was unconscious from that point. The aircraft continued a vertical climb and right roll until it was pointed straight down and horizontal to impact. At the top point inverted, you can see in the photo that the pilot is slumped forward in his seat face down. The subsequent photos right before impact, he is no longer visible in the cockpit. I agree that his seat and or harness failed because of the violent pitch change, but disagree that he was still capable of flying the aircraft, or that the aircraft stalled. It was producing full power and hit at 300+ mph.

If it actually hit 20 g's I believe it would have shed it's wings.

 

[HalinTexas]

Ack, very well written explanation of how trim works. I think you hit the nail on the head; when that tab came off the nose came up so fast that he didn't have time to react before the G's took him out.

To HalinTexas, you trim for level flight, not for a turn. You're going way off the grid talking about turning and trimming.

That may be true under normal flying conditions. But he's racing and in extended high bank turns. You trim for speed, as well. With the throttle most likely wide open and very steep banked turns, there will be some diminished speed in the turns as vertical lift almost disappears. Much like steep turns (45º bank) during training. I've never flown a P51 or any racer, I don't know what the control forces in a 70º bank turn are, but I can't imagine holding it for an extended period of time. I wouldn't be surprised if they're using quite a bit of trim adjustment even if in small amounts.

Reno course

If the grandstands are the southern end of this course, that is an extended turn coming off of a longer straight away. If the winds were out of north or NW, there would be considerable loading while making this turn to stay on the course as well as "in the race."

But you're right. I'm probably way off base.

 

[ultrarunner]

Interesting that with all the extensive mods, they still use that tiny little elevator trim tab, and a single one at that. Be relatively simply to add a second one, or better yet, get rid of them and go with stab trim instead.

But as someone else suggest, they guys ain't gonna add weight unless it adds speed.

So there you go.

 

[DznFr$$]

Obviously, no one knows at this point what the G-load was. Investigators say there was a flight data recorder on board. Maybe that will shed some light on the actual conditions. In any case, it was abrupt and violent. The plane was at its fastest coming out of the valley of speed around pylon 8 to 9 when it happened. The Mustang has a trim tab on each elevator. Interestingly, there is a full page photo of Galloping Ghosts tail on page 49 of the Reno Air Race program.

 

[Bringupthebird]

Be relatively simply to add a second one, or better yet, get rid of them and go with stab trim instead.
.

Loading up a jackscrew on a stab trim??

 

[wnplt]

"Loading up a jackscrew on a stab trim?"

That didn't go so well for Alaska Flight 261

 

[dougdrvr]

Interesting that with all the extensive mods, they still use that tiny little elevator trim tab, and a single one at that. Be relatively simply to add a second one, or better yet, get rid of them and go with stab trim instead.

But as someone else suggest, they guys ain't gonna add weight unless it adds speed.

So there you go.

I've heard from several sources that the pitch trim was modified to add electric actuation.

Ack's discription is well written and spot on.

 

[dougdrvr]

Exactly. Time to move on. Race F-86s!

There is a jet class. Anyone wants to race an F-86 could, if qualified and meet the safety inspections would be free to do so. Except for the "D" model (I don't think they allow afterburners)

 

[ultrarunner]

"Loading up a jackscrew on a stab trim?"

That didn't go so well for Alaska Flight 261

Sure didn't and that'll happen when you don't maintain a jackscrew properly!

But I stand by my comment. Some biz jets are capable of nearly 400 kts indicated at SL. Stab trim works great.

BUT, I agree....lighter is better. So yeah, while you could easily design something safer, you're gonna make it heavier, and slower. They rich boys ain't about slower!

Press on!

 

[SENECAII]

This video shows a different view of the tragedy.(No crash)

http://vimeo.com/29519344

 

[retired guy]

The P51 was designed to do about 440kts and had two trim tabs. This machine was doin` about 550 with one trim tab, the one on the right side was removed and replaced with a ground trimmable one, just to shed small amount of weight.That one was doing the work of two and at 100 knots faster than it was designed to do. Also, the airfoil is a laminer flow design, which added to the tendency to add more lift at high speeds. What I can`t figure out is why there was no explosion and fire.

 

[bubbers44]

They were pushing 500 mph, not knots. The telemetry said he was about 500 mph when he crashed. It happened over our heads so we saw the whole thing. The acceleration lift and possitive G's moved the crash from our seat section to in front of the stands in the front boxes.

Did Voodoo ever change back to two trim tabs after their first failure?

 

[SENECAII]

At 6:57 a similar problem is observed in turn 2 that happened just prior to the accident.

 

[Sandhawk]

There is a jet class. Anyone wants to race an F-86 could, if qualified and meet the safety inspections would be free to do so. Except for the "D" model (I don't think they allow afterburners)

Actually F-86 - D, K, & L models all have AB

 

[skid]

What I can`t figure out is why there was no explosion and fire.

I think this has to do with the cooling system onboard. I may be wrong of the liquid used but instead of the cooling scoop they used a boil off style system. They may have used an ADI, kinda like what is injected into the engine at race power. (One thing added to put 3500+ HP thru a merlin) I think this tub of liquid played a factor as it vaporized with the fuel they mixed and the mix does not allow ignition.

All I can say it is a sad thing! I feel for the families and would have loved to see her do what she was built to do!

 

[booo]

Exactly. Time to move on. Race F-86s!

My guess is that you have never been to the Reno Air Races............

The day that the last Merlin engine leaves Reno will be the death knell for the races.

The sound of the Merlin engine, passing over you at 500 feet and 500 mph, is visceral, romantic, spiritual, and patriotic. You feel it in your heart, your bones, and in your loins. No other man made machine will inspire you like the the Merlin engine.

Play the last 30 minutes of "Saving Private Ryan" at full volume on your home theater for a "taste" of it.

Unfortunately, most of the remaining Merlin engines are going to Thunderboats, such as "Miss Budweiser". What a shame!

 

[Mud Eagle]

Unfortunately, most of the remaining Merlin engines are going to Thunderboats, such as "Miss Budweiser". What a shame!

The shame is that you haven't checked in with hydroplane racing, apparently, since the early 1990s.

There haven't been Merlin-powered hydros for 21 years. The Bud hasn't been piston-powered since 1985 (starting in 1986 until the team went away in 2004 it was powered by a T-55 turbine engine), and even in those years leading up to '85 it was powered by a Griffon, not a Merlin.

As is, the last real 'thunderboat' was powered by an Allison, and that went away a couple years ago.

 

[wmuflyguy]

This video shows a different view of the tragedy.(No crash)

http://vimeo.com/29519344

Looked like the trim tab didn't depart til after the initial pull up. That isn't to say the control linkage hadn't failed and it was just fluttering in the slipstream.