Missing ONE horizontal stabilizer

[PR3D4TOR]

This 47D made it home after a mid-air collision.

[FLS]

My thought was that with one half of the tail missing the remaining half would under high G loads put a twisting load on the rear fuselage it wasn't designed for. I'd guess  US planes like the F4U might be less susceptible to this than European or Japanese aircraft. There is probably no meaningful data on this though so I doubt it will ever be a factor in AH's damage model.

The load is mostly on the wing not the tailplane. I don't know what the tailplane load would be but I assume any moments from the asymmetry would be handled by the ailerons and rudder. The twisting from aileron rolls seems like it would cause more stress with both tailplanes then any maneuver with just one.

This 47D made it home after a mid-air collision.

I wonder what the other guy looked like.   

[Bodhi]

FLS, I apologize for not getting back sooner.  I still have yet to grab IPB (keep forgetting to) but I dug through and found my pics of our old bird.  Here they are showing the rear attach fitting.  I also need to correct that the main rear interconnect fitting is forged aluminum with steel taper bushings and pins holding the steel fittings coming of of the Horizontals.  Had to look to refresh the memory.



In this photo, the pins are not in the fitting, but the taper bushings are.  It clearly shows that through the use of fittings, they make the spar actually continuous through the structure.

[4Prop]

This 47D made it home after a mid-air collision.

(Image removed from quote.)

I've seen 47s come home with alot worse then that. I saw a pic of 1 that had a 30mm hole in the wing

after hitting a chimney

http://www.flickriver.com/photos/damopabe/2772784512/

[FLS]

Nice pic Bohdi. That's quite a casting but it still looks like 2 spars attached to a reinforced bulkhead to me. I'm trying to understand why you see it as continuous but I'm not getting it. If they were attached to 2 castings, 1 for each side, it seems like they would function and perform the same.

The aluminum casting is interesting, it looks like if it failed it would happen just inboard of the pins.

[dirtdart]

Once joined they are a single spar as they are continuous.

[morfiend]

FLS, I apologize for not getting back sooner.  I still have yet to grab IPB (keep forgetting to) but I dug through and found my pics of our old bird.  Here they are showing the rear attach fitting.  I also need to correct that the main rear interconnect fitting is forged aluminum with steel taper bushings and pins holding the steel fittings coming of of the Horizontals.  Had to look to refresh the memory.

(Image removed from quote.)

In this photo, the pins are not in the fitting, but the taper bushings are.  It clearly shows that through the use of fittings, they make the spar actually continuous through the structure.

   Great pic Bodhi, I have a question for you if you dont mind.   What's the long yellow bolt on the left spar for?    You cant see the other side so I dont know if both sides have 1 or not but I'm curious as to it's function.

   Is it to put tension on the spar?


   

[Acidrain]

   Great pic Bodhi, I have a question for you if you dont mind.   What's the long yellow bolt on the left spar for?    You cant see the other side so I dont know if both sides have 1 or not but I'm curious as to it's function.

   Is it to put tension on the spar?


   

Attach points for the actual elevator?

[HighTone]

When I lose a horizontal stab it really wont affect the turning or snappiness of the A/C until you reach higher speeds. When it happens in a the Ki-84 your fine until the speed gets to 300mph, the she becomes real heavy. Same for the N1K and Zeke as well. The N1K2 is much better with both at higher speeds. 


I figure its a wash 

[Bodhi]

The point I was trying to make is that once joined via the forging, the spars become a continuous structure.  That is in turn attached to a sheet metal structure in the tail.

As for the those bolts, they hold the inbd elevator bearing cup which in essence is the attach point.  The tourque tube runs through a large diameter bearing which is seated in a aluminum casting which has a clevis bolt hold it in place.  Yet one more overly complex part of an overly complex aircraft.

[morfiend]

  Thx Bodhi,

   I thought it might be a mounting point for something but it didnt look like the elevator could pivot on it.. Oh and I guess you can see both,was on my laptop and didnt scroll sideways....

 Sure must be nice working on those birds but I bet it gets frustrating at time too.




   

[FLS]

The point I was trying to make is that once joined via the forging, the spars become a continuous structure.  That is in turn attached to a sheet metal structure in the tail.

What originally brought this up was whether a single tailplane could be stable and strong after damage removed the opposing tailplane and I think your picture shows that in the case of the F4U it certainly would be.

[Mace2004]

This has come up several times before. The retention of pitch authority after loss of both a horizontal tail and its elevator makes some sense from an aerodynamic perspective; however, to get the same pitch your remaining stab must be able to create twice as much force (in the form of downward lift).  Now there are two issues. First, is your single stab even capable of creating that much additional lift without stalling?  I doubt it. Assume it can, you still have to determine if it can handle the load from a structural perspective. All the force the entire tail was generated is now all on one side vice being equally distributed.  What formerly was a symetrical normal load on the tail now becomes an asymetric torsional load. All aircraft are designed with structural safety margins which explains the pictures you see of these heavily damaged aircraft that made it back. What you don't see are those that don't. Personally, I doubt the half tail could generate the required pitching moment to retain the aircraft's maneuverability and, even if it could, I doubt it could do it without twisting the entire tail right off.

[PR3D4TOR]

Mace, if you lose a stabilizer you lose half the stabilizing force acting on the tail in the horizontal axis, thus you only need half as much force to overcome it. Nifty since you only have half the control surface to do it with. If we leave the fuselage out of the equation for simplicity, you should be able to get the same amount of tail deflection with only one stab and elevator as with two of both. The aircraft will be slower to stabilize after you center the stick however, and you will lose much of the directional stability at low speed.

[mtnman]

This has come up several times before. The retention of pitch authority after loss of both a horizontal tail and its elevator makes some sense from an aerodynamic perspective; however, to get the same pitch your remaining stab must be able to create twice as much force (in the form of downward lift).  Now there are two issues. First, is your single stab even capable of creating that much additional lift without stalling?  I doubt it. Assume it can, you still have to determine if it can handle the load from a structural perspective. All the force the entire tail was generated is now all on one side vice being equally distributed.  What formerly was a symetrical normal load on the tail now becomes an asymetric torsional load. All aircraft are designed with structural safety margins which explains the pictures you see of these heavily damaged aircraft that made it back. What you don't see are those that don't. Personally, I doubt the half tail could generate the required pitching moment to retain the aircraft's maneuverability and, even if it could, I doubt it could do it without twisting the entire tail right off.

There wouldn't be any more torsional twist exerted by the single stab/elevator combo than there is from the stab/rudder combo.  There certainly wouldn't be nearly enough to twist the entire tail right off (unless there was structural damage, of course).

Of course, there is some twisting force (which is why aerobatic aircraft have a different rudder shape and location), but it's primarily going to be a yaw for rudder, pitch for elevator, even if one h-stab is missing (it gets pretty hairy though when an elevator is missing, but both h-stabs remain).

This topic came up a few years back, and was discussed quite deeply.  I had my own doubts back then.  I even had someone follow me in auto-level in the DA, so i could have them shoot single parts off of my plane so I could test.

After that, I went out and spent a few bucks on balsa gliders, so I could do even more testing...

End result?  AH is pretty gol-durn close to reality, from what I can see.  

I was actually tempted to purposely build an RC model to equate to "AH-damaged" to do some testing.  I never did, but I bet it would work.

A soda straw with a weight on the end, and some masking tape to make rudimentary stabs/elevators will show you the same thing.