On the Loss of Galloping Ghost...

[MaverickSawyer]

I know that there are a lot of theories out on the Internet on what happened at Reno on Friday last week, so let’s look at known facts.

KNOWN: 11 people have died, including the pilot.
KNOWN: More than 60 people were injured at various levels, ranging from minor scratches to traumatic amputations of limbs on the tarmac from flying debris.
KNOWN: Jimmy Leeward, owner and pilot of Galloping Ghost, had made dramatic modifications to the aircraft, including clipping a total of 10 feet off of the wings and installing a boil off engine cooling system.
KNOWN: Leeward called "Mayday" shortly before the trim tab separated.
KNOWN: The left elevator trim tab separated from the aircraft in the third lap shortly after Leeward had passed Rare Bear.
KNOWN: Nine seconds later, Ghost impacted into the tarmac in front of the VIP boxes, leaving an 8 ft. long, 3 ft. deep dent in the tarmac.
KNOWN: The tail wheel deployed in the course of the sudden maneuver.

In addition, I will discuss 5 assumptions that I have seen on this or other forums, or on the media.

ASSUMPTION #1: Leeward was unconscious, and not in control of the aircraft. (Courtesy of Hangar Talk Forum)
ASSUMPTION #2: Ghost was doing 475 mph at the time of the crash. (Courtesy of Yahoo News)
ASSUMPTION #3: Ghost suffered elevator flutter, which was the reason for the "Mayday" call. (Courtesy of Hangar Talk Forum)
ASSUMPTION #4: Leeward suffered a medical event that caused him to call "Mayday." (Courtesy of Urwumpe)
ASSUMPTION #5: The seat failed, and Leeward was unable to reach the controls. (Courtesy of FOX News, n122vu)


Let's look at the second assumption first.
Ghost had just passed Bear to take 3rd. We know that Bear was doing 450, so the assumption that Ghost was doing 475 mph is valid.

Next, the FOX News theory...
In the thread Vintage plane crashes into crowd at Reno air races, this theory arises on page 4, near the middle. It is a possibility, although a less likely one than the first assumption, which will be covered last.

The assumption that Urwumpe proposes, Leeward suffering a medical problem, leading to a "Mayday" call, will have to be determined by the NTSB, and they may have a hard time doing so, due to the amount of destruction caused by the impact. However, modern forensics can perform amazing data analysis, so we cannot discount this as a possibility.

Next, the assumption that I proposed, the elevator flutter, has more evidence than Urwumpe's. Veteran air race fans reported hearing a buzzing sound that was not related to an engine, and occurred just before the pitchup of Ghost. Once again, we have to wait for the NTSB to announce the results of their investigation. Again, we cannot discount this possibility.

Finally, the assumption that Leeward was unconcious.
Time for a little physics. Everything is easier if done in metric, so I will demonstrate the proper technique for those of you that have not taken college level physics of motion.

take your given figures:
475 miles/hour; 9 seconds from pitchup to impact; ~3/4 of a circular path taken by Ghost before impact.

Convert the velocity from miles/hour to meters/second using unit conversion.
(If you want to follow along, but do the math for yourself, skip the next couple of lines. If you want to learn how to do this, follow along.)

Start with your given: 475 Miles/Hour.
Multiply by 5280 feet/1 mile. Miles cancel out, leaving you with 2508000 feet/hour.
Multiply by 1 hour/60 minutes. Hours cancel out, leaving you with 41800 feet/minute.
Multiply by 1 minute/60 seconds. Minutes cancel out, leaving you with 696.6666... feet/second.
Multiply by 12 inches/1 foot. Feet cancel out, leaving you with 8360 inches/second.
(Still with me? Good. Now we convert to metric.)
Multiply by the conversion factor 2.54 cm/1 inch. Inches cancel, leaving you with 21234.4 cm/second.
Mulitply by 1 meter/100 cm. Cm cancel, leaving you with the velocity of 212.344 meters/second.

Whew! Lot of math there. But wait, it gets more complicated!

Now that we have the velocity, we must make an assumption that this velocity will remain the same until the fatal impact. (In reality, this would be the starting velocity, from which energy losses due to drag, gravity, and the actual manuever will remove velocity. For the sake of this post, however, we will neglect these losses.)

At 212.344 m/s, how far does the Ghost travel in 9 seconds?
Simple: V=D/T: Velocity equals Distance divided by Time.
Solving for Distance, we get D=V*T.
Inserting the values V=212.344 m/s and T=9s, we get a distance of:
1911.096 meters.

So how does this help us in understanding the accident? It allows us to find the G's Leeward was experiencing in the cockpit.
Take the distance we just found, and place it on the ~3/4 circle that the plane traced as it flew up, over, and then into the ground (and the VIP boxes).
3/4 Circumfrence=1911.096 meters.
Find the full circumfrence of that circle:
Circumfrence = 2548.128 meters.
Since Circumfrence=2πr (FYI: that's a pi symbol: 3.1415927...)
r=405.55... meters.

Still with me? Good. Prepare for some physics...

Radial acceleration (pulling G's in an airplane) is found using the formula:
A=V^2/r, or Acceleration equals the velocity squared divided by the radius of the circle. This is where the constant velocity makes this much easier.
Insert the values we have gathered so far into the equation and we get:
111.18 meters per second squared. Divide this by the force of gravity at the surface of the Earth, Fg=9.80665 m/s^2, and we get the final answer we have been working towards these last few minutes, the G's being pulled.
Leeward was pulling...
11.34 G's.

So, why does this matter? After all, the Thunderbirds and Blue Angels pilots routinely pull that much. The difference is, they are expecting it. They are ready for the onset of the G's. Leeward was caught off guard, and without a G-suit, he passed out. This is backed up by the experience of Bob Hannah, who was flying Voodoo, another Mustang, when the trim tab fell off during the 1998 race. He pitched up at more than 10Gs, and did not come around until several seconds after the G's backed off. Leeward was under continous load until impact. This is backed up by a photo of the cockpit of Ghost that was taken at the top of the climb. With a clear view through the canopy, the picture showed Leeward's head pinned against the instument panel, below the lip of the cockpit walls. Therefore, Leeward was passed out, and would never feel the crash.
Assumption #1 is TRUE. Physics doesn't lie.

Most importantly, what caused the trim tab to fail? The NTSB has the final say, but my (highly uneducated) opinion is the following chain of events occured:
1. Some emergency is detected in the cockpit by Leeward. He calls "Mayday", and swings wide to conserve energy, intending to trade airspeed for altitude before coming in for landing
2. Keeping the curve going, he heads for the inside of the course, and begins to level out. However, he crosses over the turbulent wake of the aircraft that have already been by. This turbulence causes an already overstressed trim tab on the left elevator to fail.
3. With the departure of the trim tab, the control stick snaps forward with enough force to drag Leeward along, causing him to bash his head on the forward console. He passes out.
4. The aircraft now performs a 11+G pitchup. Leeward remains unconcious as the plane executes a snap roll to the right, and begins to descend towards the crowd. At some point, the G forces deploy the tailwheel, resulting in the famous image taken of the left side of the aircraft as it plunges to the ground.
5. The plane impacts into the tarmac. A "mass casualty situation" ensues.

I am interested to see what the outcome of the NTSB report is, and pray that this is not the end of the Reno Air Races.

God bless those who died or were injured that day.

 

[Urwumpe]

The trim tab could also have failed already before the mayday. while it will make it nearly impossible to control the aircraft at that speed, it is not impossible that the plane was still controllable for a short time while he turned out of the circuit and went suddenly out of control alone by changing flight state. The trim tab assists in controlling the elevator, but you can fly without it, if you are slow enough.

It could also be the case that at that high speed, he was flying the elevator almost stalled and the lost trim tab only managed to cause trouble when he slowed down and laminar airflow over the trim tab resumed.

There are a few physical phenomena...and yes, the NTSB will possibly find out better than we can. We would already get at the limits of our competence by doing OpenFOAM simulations of a P-51 stabilizer with and without trim tab.

 

[MaverickSawyer]

The trim tab is what keeps the P-51 controllable at those speeds. It offloads the stick so that you don't have to fight the force needed to keep the nose level. You need quite a bit of nose down triim to remain stable at 450 mph.
Why that causes a sharp nose up movement is beyond my understanding...

 

[Urwumpe]

Simple causal chain:

Trim tab up makes the elevator go down and neutralize the upward moment caused by the excess lift. When trim tab breaks away, the elevator will go up and since it has inertia of its own, it will also go up higher than it would by itself.

Still, if the plane was in a strong curve and the elevator close to neutral, the trim tab loss wouldn't instantly cause trouble, since the elevator is fairly stable around that situation.

But then you get turbulence and resonance into the game. A good pilot can control the elevator for some time and keep the plane stable, but the behavior is now much more aggressive and chaotic. within a small range of parameters, all works fine, and you need to drop speed as fast as possible to widen this range.

Then, the pilot does something wrong, or the turbulence of another plane interrupts the stable situation. The elevator oscillates a bit in its own turbulence, like a flag in the wind, swings to full up. The elevator isn't really tiny and the P-51 had no hydraulic system, which also means the P-51 had a direct relation between elevator force and the force on the stick. Maybe the pilot was even hit by the control stick, when it suddenly flew backward at strong force.

Fact is: at that speed and after you lost the trim tab, the elevator has the tendency to go up. But it must not be instantly the case.

 

[Lou50]

I understand that GG was only flying with the left trim tab functional and the right one faired with the surface. Does anyone know why this decision was made and why they picked the one that would put the linkage in compression where if they had used the right side, that would have been in tension and more tolerant to the loads?

 

[Lou50]

The NTSB investigator indicates that Mr. Leeward did not make a mayday call. I would suspect this is true due to the tab departing the airframe and the 12.6G pitch up that would have taken the stick away from him and rendered him unconscious. It is interesting to note that the preliminary report released by the NTSB on the following Friday did not mention a Mayday one way or the other. "As with the memory cards, one of the authorities' first goals will be to determine whether these came from the plane being piloted by 74-year-old Jimmy Leeward. Countering earlier reports, Rosekind said Sunday that Leeward did not send a "Mayday call," indicating he was in distress." anyway anyone have an idea why they deactivated one trim tab?

 

[MaverickSawyer]

Thank you for the new info. I will post it on the thread.

 

[Lou50]

something for consideration:Last flight video http://player.vimeo.com/video/29519344?title=0&byline=0&portrait=0

From a friend of a friend of a friend

Quote
Our new crew member, Matt Jackson, is not only a race pilot,aircraft business owner and aircraft owner (he also takes care of Tom Cruises P-51) but he is also the VP of the Unlimited Racing Class and head of the Safety Committee.

We had a long talk about the Reno crash on the way to Mojave today.Matt believes the cause of the crash was due to The Galloping Ghost having a CG too close to the aft limit which resulted in pitch instability. There are in structions on the P-51 regarding no combat missions with the aft fuel tank full resulting in an aft CG problem. Instructions specify to empty the aft fuel tank first in flight.

During qualifying Matt watched Galloping Ghost from inside the cockpit of Furias and could not believe how much trouble Leeward was having in keeping the Ghost in a stable pattern around the course.

Since Leeward lives in Florida and the Galloping Ghost was modified for racing in Calif., when Leeward picked up the Ghost for the Reno races at the last minute, a complete flight test program had not been done based on available information.

There is a video of the entire last lap of the Ghost before the crash which Matt showed me. As Leeward was coming around pylon #8 at about 480 mph after passing Rare Bear, he hit turbulence which pitched his left wing down, Leeward corrected with hard right rudder and aileron. Just as the aircraft
was straightening out, he hit a second mountain of turbulence which caused the tail to 'dig in' resulting in a 10+ G climb rendering Leeward unconscious instantly and resulted in the tail wheel falling out. (broken tail wheel support structure was found on the course). As the Ghost shot upward the LH elevator trim tab broke loose. This can be heard on the tape,
so the trim tab did not cause the accident.

Since the Ghost was racing at 480 mph with full right rudder and the stick full right, this is where everything stayed when Leeward blacked out. Cockpit camera film that was salvaged from the wreck shows Leeward slumped over to the right in the cockpit. As a result, the Ghost climbed up and to the right, rolled over on her back and then headed for the box seats. Most in the box seats never saw it coming because it came in from behind them.

Matt has had long conversations with the NTSB who call the accident a 'fluke'. They are not going to recommend canceling future races. He has also talked to the insurance companies covering the races for Reno and they also say they are not going to cancel their coverage of future races. Now we waitfor the FAA to make a decision.

Ironically, Matt bought box seats tickets for his good friends who stayed with him for a few days before the races. They were the husband and wife who were killed.