In the words of Mark Twain:

"One gets such wholesale returns of conjecture out of such a trifling investment of fact" :ugh:

Re: Fuel supply? If dependent on atmospheric pressure in any way, or even with positive pressure electronic pumps, isn't the fuel mass going to be quite lethargic at 12 G? One suspects cavitation, or vapor lock.

RH elevator. With the trim tab set for ND on the LEFT side, the LHE has some of its up force relieved at the Bellcrank. The RHE has no such advantage, and the stress is greater at the RHE join. This reverses with Pitch, and there is a chronic war twixt the right and left sides of the torque tube joins. Each reversal of elevator position causes two of these torsional reversals rather than one. So fatique is doubled, and the throughbolts are not designed for this, imo. (Notwithstanding the design consideration does not include these torsional challenges, originally).

What results is an inadvertent "warping" effect, through the hinge line of the Horizontal tail. The design is counter to such a consideration, imo. Again, if the design were to be carried through, and there is no reason to abandon the idea, the Torque tube would be a unit, not halves.

I select the RHE for failure because of this stress bias against it. I take note of the quote above. Mark Twain was editor of the "Territorial Enterprise" in Virginia City, just down the road from STEAD AFB, so that makes him a local, and had he lived, he likely would be flying some "contraption" at RENO each September.

He was an accomplished PILOT. SteamBoat wise.

For the Merlin, then. Fuel Injection? For the Mustang, CFRP tail feathers and Fuselage? Tame the skin, lose the drag. And a Stout Torque Tube for the els.

Klink: Newton's Third? In failure,the stress is differential, not opposite, imho. The Third applies to the controls' NET effect on the airframe?

However this observation flies in the face of pictures showing the tail wheel doors on in the final dive. (The side view picture.) After reviewing the video of the aircraft, I have yet to see anything leaving the aircraft other than the trim tab.

C-C et al, just to go back to my earlier reference to the article by Space-Electronics; it refers to mass balancing of control surfaces,not specifically `tabs`,more as a unit and `Moment of Inertia`,but also considers Product of Inertia` being the spanwise distribution of mass balances on control surfaces.Also that this factor seems to be largely `ignored`.
In the Mustang case, the ailerons appear to be balanced along their span( indeed in `Wrench`s link to `Aircorps` there was an early modification to the Mustangs` ailerons to replace the left aileron mass balance,made of steel` with one of a non-magnetic material as it interfered with the compass detector in the wing.)
However, the elevators and rudder,have solid balances towards their tips in each case,and do not appear to be balanced along their span,,ie, not taking `product of inertia` into account.
In the event of `flutter` starting,for whatever reason I would suspect that there will be a very rapid and
strong torsional twisting between the elevators and along the elevators due to the mass balance concentration at the tips,and as visible in the `V` tail glider elevons.
I realise that the m-b weights may also be aerodynamic balances,and there is not a lot of room in front of the elevator to the rear spar unlike the ailerons which appear to be `shrouded` on top and bottom.Perhaps your contacts may know more about that.....Did NA miss a trick here when it was designed
ed; does anyone know of othe incidents of `flutter` on other types,either racing or airtesting,as it seems that Mustangs have had a few tab failures including rudders..?
NB.I have nothing against Mustangs,just want to explore all avenues if possible...

Little Clues
 

A few posts earlier I asked the question whether or not the Ghost had an elevator bobweight installed. I think I have found the answer, but look for yourself.
First Clue: From http://en.wikipedia.org/wiki/The_Gal...host_(aircraft)
600 lbs removed from a P-51 is a lot of weight, I think I have found where 20 lbs of that weight came from.

Second Clue is this third hand post from post 291 in this very thread: http://www.pprune.org/6736071-post291.html

Third clue is from TECHNICAL ORDER NO. 01-60J-29 found here: http://www.aircorpsaviation.com/Webs...ges/60J-29.pdf
Fourth clue from the same source:
http://home.comcast.net/~shademaker/P51ElevControl.jpg

The elevator control bellcrank assembly is mounted just aft of the cockpit on the flap torque tube. The twin up and twin down elevator cables run from the elevator control bellcrank assembly and attach to the two arms on the elevator bellcrank that we have seen previously. This was done for combat survivability reasons but it had certain other advantages as well.

Fifth clue is this picture from the tech order:
http://home.comcast.net/~shademaker/...llcrnkwBob.jpg

Here we see what the elevator control bellcrank looks like and what the bobweight added to the bellcrank looks like.

Sixth and final clue is this picture segment brightened a bit to show the shadowed area taken from the build up of the Ghost. Do you see the elevator control bellcrank? It is mounted on the slightly copper colored shaft. Do you see a bobweight? Do you think you should be able to see it if it is there?
http://home.comcast.net/~shademaker/...lBellcrank.jpg
Removal of the elevator bobweight could cause handling problems and could leave the elevators subject to flutter for the reasons just stated by sycamore since the bobweight acts to damp out oscillations in the inboard sections of the elevator, particularly if both pairs of cables are in place. I am fairly sure that the bobweight is not in the picture, but I am not 100 % positive.
Was it a victim of the long ago weight saving campaign? Could that be what happened to the starboard trim tab actuator as well?

Was the bobweight there for stability reasons, or was it the flutter balance weight?

Were there any other balance weights?

Bob weight
 

Modern aircraft have bob weights installed mainly to solve phugoid problems. The bob weight has no effect on mass balance. Given the amounts of turbulence likely to be encountered during the race and the speeds, the elevators would have been better balanced with the weight distributed along the leading edge and not with most of it located in the horn.

Machinbird. With respect, the Flap TT blocks the area where one expects to see the Bobweight. Flutter can happen with highly tensioned actuators, as these are not. Even with hydraulics. The cables would not be sufficiently robust to blank flutter, imho.I notice the default arm of the weight tensions Nose UP, curious the design thought behind that.

What a treat, your drawings, and comment, thanks.

Stressmerchant
It appears that the P-51 had a bit of a tendency to experience stick force lightening at higher g levels without the bobweight. The Technical Order specifically states,. So the bobweight was there for stability reasons and not for phugoid reasons.
Any tendency to stabilize the elevator was an added bonus.
Ideally you want the counterbalance mass evenly distributed and firmly attached to the control surface, but in practice this can be difficult. As I recall, my F-4 had rudder mass balances in a shielded horn near the tip and out of sight in the fuselage.
If you have time, read into this link about Strega and what happened when they switched to a "tube" engine. Tiger Paws

Lyman, I guess I'm looking at the drawing wrong, but the weight would want to rotate the bellcrank ccw (per drawing) thus pulling on the control rod on the stick actually moving it forward.....(nose down). Countering a severe positive g climb......or am I backwards? But could understand the need to remove some of it in racing conditions.

If you guys go to `keypublishing.com` and look at `historic aviation` ,there is a thread about the restoration of a TF-51. There are a lot of photos,some relevant but near the end of p.2 there is a photo of the lower controls with the bobweight.

Hi sycamore. I am basing my thoughts on a pushrod that is mounted above the pivot bearing of the stick, not below it. Hence forward stick pulls the pushrod forward, and the crank articulates CW. It is a guess, but it puts the minor bearing "inside" the Stick bearing, protecting it, and saving additional Stick length.

again, a guess.

The `exploded view ` of the mod. is looking aft,and also the photo at #54 on that thread.The bobweight is forward of the stick pivot,so under `g` loading it pulls down increasing the `stick-force per G increment,and the same for negative G.In the TF51 case it may be further back as it`s got full dual controls.
I would think that for the weight reduction for racing there would be a lot of extra hardware,ex-mil, that could be removed without touching the controls,or maybe just reducing the bobweight somewhat..

Three small hinges and 3 small screws held the trim tab in place.( on the original)

That should give an idea of the expected trim tab forces.

I am not surprised that the tab came off at the speeds and forces it experienced.

http://i997.photobucket.com/albums/a...vatorandTT.jpg

Sycamore, thanks for the link to the TF-51 build.:ok:

web find, that claims this is P-51

http://kr2seafury.com/resources/_wsb...trol-stick.jpg

Also, does anybody else hear a "POP" at the begining of the "medium speed" portion of the climb video, in addition to the "CLICK" heard later in the climb? Just wondering......

Oh, and thanks for the heads up on the tf-51 build up, thats pretty amazing stuff.

So does the bobweight double as the balance weight? Or is there a specific balance weight?

Perhaps out the fitting near the tip?

Does anyone know what the original (fabric covered) and later elevator balance limits were?

For those who may be interested, here are some excerpts from the original P51 flight manual


http://i997.photobucket.com/albums/a...ty/fltman1.jpg

http://i997.photobucket.com/albums/a...ty/fltman2.jpg

http://i997.photobucket.com/albums/a...ty/fltman3.jpg

http://i997.photobucket.com/albums/a...ty/fltman4.jpg

Excuse the absence. It's fall around here and the GF scheduled a cabin vacation. Surprise.

Have found some change orders from back in the day, and the bob weight is included;

Tech INFO - Aircorps Aviation

They strengthened the horizontal and vertical, but there are no tell-tale signs of any elevator problems, other than the plastic trim tabs and maybe the outer hinge. The mechanics would ensure the mods are complete on the current airplanes.

Also did a stress analysis of the torque tube and if I did it right, for a 9 g turn at Reno, it's only 5 kpsi. Yield for 2024-T3 is around 45 kpsi, so fatigue or outright failure of the tube is low probability. That leaves the attachment analysis. Contacted a restorer in Texas and will try to talk him into drilling off the D spar of a damaged elevator to get the attachment details. Or, if anybody has the blueprints, or details, that would be better.

I have found a picture of the ghost made during the engine run ups after joining the wing and fuselage. At that time, the bobweight is definitely not there.

The green circle marks where it would be visible. All that is there is the elevator control bellcrank upper arm.

A bobweight would mitigate the nose up input that occurred at the beginning of the accident.

http://home.comcast.net/~shademaker/Missing.jpg

I'm intrigued. If I read the documents correctly, when they changed from fabric to metal elevators, they refitted the original balance weights. Also, there does not appear to be any individual balancing instruction - they merely put the balance weight in place, no actual measurement of the imbalance. Is this correct?

Sounds like the bobweight may have been acting as an additional balance weight as well. Hardly a case of distribution along the hinge line, but it may have helped.

Does anyone know what the actual balance requirements were?

Clipped Cub

Per the picture of the torque tube install, it would appear to be a great deal more robust than its join to the elevator Rib. Going from torsion to shear to compression (at the elevator surface), the weak link looks to be the tube to Rib join. Focal stress on this area is chaotic, compared to the Tube's single stress purpose? (Torsion).

For wartime, the design is elegant. For racing, I keep thinking a full length torque tube, tip to tip, solves the problems of tab, elevator warp, and wear, plus asym roll? At some stage, an all new a/c will be needed. The nagging feeling is there, that to butcher these priceless relics beyond their designed purpose is arrogant, and obviously, risky.

imho

Lyman

Maybe they could modify the old warbirds more, but I am sure that anyone racing these aircraft wants to reduce the risk to anyone from structural failure.

As far as new built racers go, look at what has happened to the purpose built racers like Miss Ashley and Tsunami. I think that the sport is running up against the limits of technology and engineering.

Unless they restrict the big boys like the F1 Air-racing, they'll probably keep much as they have been.

gileraguy

No rules in a knife fight. "Unlimited". Leeward exhibited some instability that was noticed by another competitor, that could not be put down to wind. However it derived, clearly he was at the ragged edge of control.

IMO I think the a/c was rushed into the race, he had little time in it, plus he had shown some impatience to get it to perform well.

At some level, the competition becomes "Jackass IV", with certain injury, and the level of risk well above the reasonable return. "My wings are shorter than yours", "I have the hot set up cooling system", "I'm pulling 140 inches", etc.

The line, the LIMIT, if you will, stretches to a certain point, then crumbles, and people will be killed.

Don't get me wrong, I don't go to RENO to see the AT-6's. Or Sean Tucker. I go to feel the ground shake.

stressmerchant
After giving this some more thought, I believe that this is correct with the following observations:
For low frequency oscillations, the bobweight would be relatively tightly coupled to the elevator and would act to damp such oscillations.
For higher frequency oscillations, the bobweight would not be as tightly coupled to the elevator due to deflection of the intervening structure and the likely smaller amplitude of oscillation.

Non-use of the bobweight could then result in enhancing lower frequency oscillations affecting the center of the elevator. Lower frequency resonances are the most important ones to control.

Additionally, removal of the radiators and associated structure may have affected the aircraft's basic resonant frequencies in the aft fuselage and caused a new problem.
Have a look at the following FAA Advisory Circular. This applies to Part 23 certificated aircraft, but is good guidance for anyone contemplating aircraft modifications. http://rgl.faa.gov/Regulatory_and_Gu...C23-629-1b.pdf

Ghost's onboard cameras did not yield images.
 

Reported by EAA:

Is there update on this tragic event..?

NTSB held a briefing today in Reno with some preliminary findings and data, and some safety recommendations.

Link for their archives (April, 10 2012)

National Transportation Safety Board

Some very interesting info from some still photos regarding elevator trim tab positioning.....near as I can tell they are still trying to figure out what exactly caused the "upset" (as they are calling it) when the a/c over banks the turn.

Reno Update.

More info here.


Press Release April 10, 2012 - NTSB Provides Investigative Update and Issues Recommendations to Increase Safety at Air Races





Charlie

The findings of the National Transportation Safety Board suggests that the pilot had lost consciousness due to ‘overwhelming’ G forces. This occurrence in a modified 1940′s vintage aircraft is likely considering its high thrust to weight ratios amongst its contemporaries, with a structural strength of -2G to +9G, making it likely that G induced loss of consciousness (G-LOC) could have been the cause of this tragedy.

Yes, G-LOC can be a cause for a pilot to loose control of the aircraft. In a flight which (for that phase) seemed to be intended as primarily straight and level, something unusual had to cause the high G. Prevent that, and you've prevented the G-LOC. A pilot who knows that they are about to enter a high G maneuver, can plan for that event. A pilot who is surprized by it may have a much reduced tolerance...

Final Report likely soon.
 

Recently chatted with an NTSB investigator-not one of those working on this accident-who indicated that the final report is likely to be published within a month.

:confused:I understood that g-lock was caused by prolonged exposure to high g, normally happening in a military jet.

Without training (straining techniques, breathing) or equipment you can get G-LOC at as little as 5G. You don't need a military jet for that. Any WWII military fighter, and any half-decent aerobatic trainer, will do 5G with no problem.

The G-LOC onset curve is complex but in certain situations it can happen in less than four seconds. You don't need "prolonged" exposure. See the figure in this article:

G-LOC, COULD IT HAPPEN TO YOU?

Forgot about this but I’m not sure what any report can recommend that isn’t already fairly obvious.

So you have an aircraft, designed to be at the cutting edge of technology 70 years ago then gets cut and shut to a point where the people doing the cutting and shutting are accepted as the experts. There is a question over regulation. There is also a huge question over the amount of testing that was done. There should be a question over the physiological affects and what airmanship is demonstrated allowing 70+ year olds to compete. Then the positioning of the grandstand finishes it all off.

17.3 g!
 

NTSB released new documents yesterday.....


August 21, 2012

NTSB Releases Reno Documents

By Mary Grady, Contributing editor


http://www.avweb.com/images-avweb/clearpixel.gif

http://www.avweb.com/newspics/reno_ntsb.jpg

The NTSB on Tuesday posted online more than 900 pages of documents plus photographs related to its investigation of a fatal crash at last year's National Championship Air Races in Reno. Among the documents is a careful examination of a video shot by a spectator at the event, which concludes that the Galloping Ghost, flown by Jimmy Leeward, reached a maximum acceleration of 17.3 Gs after a roll upset, in which the airplane reached a roll angle of 93 degrees, left wing down. The documents also examine several photos that show the departure of a trim tab from the airplane's elevator. Leeward and 10 people on the ground were killed when the racer crashed. The safety board said it will release its final report, with a determination of probable cause, by the end of this month.


The docket contains summaries of interviews by NTSB investigators, maintenance records, a meteorology report, a report on "survival factors" and more. "The information … is factual in nature and does not provide any analysis," the NTSB said. In April, the NTSB released a half dozen safety recommendations, so organizers could consider implementing them for this year's races, which are scheduled for Sept. 12 to 16. The Reno Air Racing Association, which organizes the races, said changes have been made to the race course in an effort to better protect spectators. The insurance premium for this year's event increased by $1.7 million, according to the association's website.


All so sad.

MB

Factual medical information:-

The following information was obtained from the
FAA Forensic Toxicology Laboratory at CAMI:

"Ethanol, 58 mg/dL."


"FAR Section 91.17 (a) prohibits any person from acting or attempting to act as a crewmember of a civil aircraft while having 0.040 g/dL (40.0 mg/dL) or more alcohol in the blood. "

"Ethanol and methanol were however identified in muscle on postmortem toxicology. "

Do I infer from this quote that there is a suggestion of Mr Leeward having had a drink?????

Ethanol, and methanol, the base ingredient of the likes of Vodka, and Gin, is a derivative of oil. Ethanol for spirit production, is a refinement of the stuff you put in your car, or aeroplane.

Do you have figures for 'background' levels of either ethanol, or methanol, in every human, muscle tissue?

Evidence, as far as I know, of recent alcohol consumption, is taken from blood level, not muscle tissue.

This event was very tragic, and any suggestion that the pilot was not 'fit', is in my view ill placed.

I

I think that when you pick through the bones of this sorry tale you find in almost every element a casual attitude.



Be that themodifications to the aircraft, the flight testing, the positioning of spectators, the record keeping and the pilot – incidentally has anyone seen Leeward’s personal flying log book?



Now itseems there is ethanol in the tissue. Draw your own conclusion as to what that means. Why nobody tested for blood alcohol levels goodness only knows. What is very interesting is that when some guy wraps his Tiger up and goes to the pub there is a cry ofirresponsibility.

Quote:

---

Ethanol, and methanol, the base ingredient of the likes of Vodka, and Gin, is a derivative of oil. Ethanol for spirit production, is a refinement of the stuff you put in your car, or aeroplane.

---

Additional information provided by the
NTSB IIC:


The fuel used by the accident aircraft did not contain ethanol or methanol. The accident aircraft had a modified "boil ‐off" cooling system that contained methanol.

So no ethanol in the plane... so to use your own words we are left with Vodka or Gin..