Reno 2011 crash findings

[fly_tornado]

Credit: National Transportation Safety Board - NTSB WPR11MA454

 

Deteriorated Parts Allowed Flutter Which Led to Fatal Crash at 2011 Reno Air Races

 

WASHINGTON - The National Transportation Safety Board determined today that deteriorated locknut inserts found in the highly modified North American P-51D airplane that crashed during the 2011 National Championship Air Races in Reno, Nevada, allowed the trim tab attachment screws to become loose, and even initiated fatigue cracking in one screw. This condition, which resulted in reduced stiffness in the elevator trim system, ultimately led to aerodynamic flutter at racing speed that broke the trim tab linkages, resulting in a loss of controllability and the eventual crash.

 

On September 16, 2011, as the experimental single-seat P-51D airplane "The Galloping Ghost," traveling about 445 knots, or 512 mph, in the third lap of the six-lap race, passed pylon 8, it experienced a left-roll upset and high-G pitch up. During the upset sequence, the airplane's vertical acceleration peaked at 17.3 G, causing incapacitation of the pilot. Seconds later, a section of the left elevator trim tab separated in flight. The airplane descended and impacted the ramp in the spectator box seating area, killing the pilot and 10 spectators and injuring more than 60 others.

 

"In Reno, the fine line between observing risk and being impacted by the consequences when something goes wrong was crossed," said NTSB Chairman Deborah A. P. Hersman. "The pilots understood the risks they assumed; the spectators assumed their safety had been assessed and addressed."

 

Contributing to the accident were the undocumented and untested major modifications made to the airplane, as well as the pilot's operation of the airplane in the unique air racing environment without adequate flight testing.

 

The nearly 70-year-old airplane had undergone numerous undocumented modifications. The modifications, designed to increase speed, included shortening of the wings, installation of a boil-off cooling system for the engine, increasing the elevator counterweights, modification of the pitch trim system, and changing the incidence of the horizontal and vertical stabilizers.

 

Although the Federal Aviation Administration required that a flight standards district office be notified in writing of any major changes made to The Galloping Ghost before it could be flown, investigators could find no records that such notifications were made except for the installation of the boil-off cooling system. The undocumented major modifications were identified through wreckage examinations, photographic evidence, and interviews with ground crewmembers.

 

In April, while the investigation was ongoing and after the NTSB's investigative hearing in January on air race and air show safety, the NTSB issued 10 safety recommendations to the Reno Air Racing Association, the National Air racing Group Unlimited Division, and the FAA. These recommendations addressed:

 

requiring engineering evaluations for aircraft with major modifications;

 

raising the level of safety for spectators and personnel near the race course;

 

improving FAA guidance for air race and course design;

 

providing race pilots with high-G training and evaluating the feasibility of G-suit requirements for race pilots; and

 

tracking the resolution of race aircraft discrepancies identified during prerace technical inspections.

 

Although no additional safety recommendations were issued today, the Board reclassified nine existing recommendations as described below:

 

Eligibility Requirements for Aircraft with Major Modifications - recommendations A 12 9 and A-12-13 classified "Open—Acceptable Response"

 

Prerace Technical Inspection Discrepancy Tracking - recommendation A 12 10, classified "Closed—Acceptable Action"

 

Spectator Safety - recommendations A 12 14 and 15, classified "Closed—Acceptable Action"

 

High G Training, G-Suit Feasibility for Pilots - recommendations A 12 11, -12, -16, and -17, classified "Closed—Acceptable Action"

 

A tenth safety recommendation, issued to the FAA, which addressed air race and course design guidance was reclassified as "Open—Acceptable Response" on July 25, 2012.

 

"It's good news for the air races that so many of our recommendations have been addressed," said Chairman Hersman. "We will continue to push for the full implementation of all of our safety recommendations."

 

A synopsis of the NTSB report, including the probable cause and a complete list of the reclassified safety recommendations, is available at: http://www.ntsb.gov/news/events/2012/reno_nv/index.html.

 

 

 

[turboplanner]

So, our speculation was about right.

 

Pity such low cost items had not been maintained.

 

 

[fly_tornado]

I think the flutter was a significant contributor

 

 

[turboplanner]

Caused by?

 

 

[fly_tornado]

shortening the elevator

 

 

[turboplanner]

No

 

 

[David Isaac]

Worn locknuts on the trim tab attachment screws allowed the attaching screws to loosen and allow flutter to develop and cause loss of control and destructive trim tab failure.

 

 

[winsor68]

I wonder if the parts were 70 years old?

 

The BIG ramifications... it says the mods to Galloping Ghost were not documented and OKed. I believe she like many of the other Unlimited Racers was modified over the last 40 or so years... I imagine getting the paperwork in order will be a big cost and headache if the governing body requests it...

 

 

[M61A1]

I wonder if the parts were 70 years old?The BIG ramifications... it says the mods to Galloping Ghost were not documented and OKed. I believe she like many of the other Unlimited Racers was modified over the last 40 or so years... I imagine getting the paperwork in order will be a big cost and headache if the governing body requests it...

Working on military aircraft, we tend to change our hardware frequently, in the civvie world, hardware is expensive, so people try to get the most out of it. Regardless of the mods, I think one of the lessons here is that if you can screw a locknut on with your fingers, replace it, if it's still loose, change the bolt/stud too.

Try asking yourself, "what is the worst possible outcome if this bit fails?"

 

 

[turboplanner]

That's what got me so angry when it happened M61A1, I've seen guys in car racing spend thousands on a motor, then write the car off because they didn't fit lockwire on a suspension component. They could have saved the car by picking up some scrap from the floor.

 

To kill innocent spectators as a result of that is almost murder.

 

 

[facthunter]

The trim range called for is miles outside being capable of doing the job. A moving horizontal stabiliser is required, to have the authority going from high angle of attack in corners to overspeed on the straights. The planes are too ancient in design concept to do those speeds. While it may be hair on the back of the neck stuff to watch, it's a rich man's indulgence and not the right thing to do with a rare warplane. They should be built to new specifications specially for the sport. Too many spectators paid the price here. Nev

 

 

[dazza 38]

The thing that surprised me was how the wings didnt detach from the fuselage after the 17.3 G deviation.I guess the clipped wings helped abit, but that was unbeleivable.I being a warbird lover, would rather rare WW2 aircraft never be modified for racing and be restored to look and fly like their original designers envisaged.

 

 

[M61A1]

The trim range called for is miles outside being capable of doing the job. A moving horizontal stabiliser is required, to have the authority going from high angle of attack in corners to overspeed on the straights. The planes are too ancient in design concept to do those speeds. While it may be hair on the back of the neck stuff to watch, it's a rich man's indulgence and not the right thing to do with a rare warplane. They should be built to new specifications specially for the sport. Too many spectators paid the price here. Nev

One of the tricks for these racers is to get your CoG as far aft as you can without becoming unstable, the reason for that is so that they can unload the horizontal stab ( with the stab providing down force this adds to the wing loading). That done, they usually change the angle of incidence on the horizontal stab ( to align with the airflow, creating less downforce)), they do all this to reduce the drag involved. The fastest racers use the smallest necessary control inputs and the lowest ( but usually the most prolonged) G forces, as anything that increases AoA and G will cause drag and that is what they are avoiding.Information from a 2007 issue of Air & Space........possible techniques have changed since then.

 

 

[M61A1]

The thing that surprised me was how the wings didnt detach from the fuselage after the 17.3 G deviation.I guess the clipped wings helped abit, but that was unbeleivable.I being a warbird lover, would rather rare WW2 aircraft never be modified for racing and be restored to look and fly like their original designers envisaged.

Yes an F4U Corsair just doesn't look right with a tiny bubble canopy and half the rear fuse missing, it's awful. Not that P51's look any better with the same mods.

[fly_tornado]

Funny thing is that I saw galloping ghost racing on Thursday and it looked fine.

 

 

[turboplanner]

As they do FT. I've pulled many race frames apart and found a joint hanging by less than 10% of uncracked/uncorroded material.

 

 

[winsor68]

I guess there is a lesson in this... Again it comes back to culture and complacency... and I fully acknowledge it is always easy in hindsight.

 

They ran the Unlimited Racers often enough to create the "atmosphere" that it was safe... but in reality when you really think about it what is really surprising is that they didn't have a really close call before this major accident to compound the problem.

 

 

[fly_tornado]

Who would have thought it would happen? but it was just a matter of time.

 

 

[winsor68]

Who would have thought it would happen? but it was just a matter of time.

Exactly.. the two statements are direct opposites but as so often is the case fits this scenario perfectly...