Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Citabria on April 21, 2012, 02:27:06 AM
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I can't stand the other thread any more about 1 hstab missing and everyone on a tangent about vert stab gone....
heres the deal. when you shoot one HORIZONTAL STABILIZER off a fighter they gain instability and maneuverability that is close or better than having intact surfaces.
losing an entire control surface of one horizontal stabilizer and one elevator is preferable to losing just one elevator in Aces High.
I have no idea if this is accurate but it seems counter intuitive that when you damage an airplane it performs better.
the only clearly visible down side to losing one hstab is the aircraft can become uncontrollable in a stall or sub stall speed vertical maneuvers.
when missing one HORIZONTAL stabilizer you gain instability in that you can pitch the nose up and down quite quickly and to a greater degree than with both stabs on.
thus reduced stability equal maneuverability. instead of being wounded when hit in the tail the wounded plane is basically undamaged for all intents and purposes of the dogfight and in some instances even more dangerous.
given that the damage system while extensive does simplify many systems of aircraft to approximate the results of battle damage this leaves the horizontal stabilizer damage results feeling likely aerodynamically accurate yet not in keeping with the methodology of battle damage decreasing combat capability.
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Before HTC improved the damage model the F6F would frequently lose its whole horizontal tail. Now it usually loses half its horizontal stab which is a big improvement in survivability. I find being in this state makes very little difference to the F6F's sustained turn performance, particularly once I dump flaps. USN aircraft have very good control authority which helps. There is probably a gain on instantaneous turning, pulling for a snapshot. However I have to be careful doing this as as it easier to get into a nasty spin if I push it too far.
This seems fair enough to me in terms of aerodynamics. It is the wing that generates turning performance, the tail just points the aircraft. Structurally there might be a case for saying that losing one half of the stab might increase the chances of the rear fuselage or the rest of the tail spar failing under heavy G loading.
One other thing I've noticed is how much braver some opponents become once I lose half a stab. I had a bunch of planes bnzing me last night and only realised I'd lost half my stab after a couple of them made the mistake of trying to turnfight me. :D
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thanks fester :aok
the P51 turns better when missing ONE horizontal stabilizer, but like the F6F you have to be careful when pulling a snapshot :old:
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Before HTC improved the damage model the F6F would frequently lose its whole horizontal tail. Now it usually loses half its horizontal stab which is a big improvement in survivability. I find being in this state makes very little difference to the F6F's sustained turn performance, particularly once I dump flaps. USN aircraft have very good control authority which helps. There is probably a gain on instantaneous turning, pulling for a snapshot. However I have to be careful doing this as as it easier to get into a nasty spin if I push it too far.
This seems fair enough to me in terms of aerodynamics. It is the wing that generates turning performance, the tail just points the aircraft. Structurally there might be a case for saying that losing one half of the stab might increase the chances of the rear fuselage or the rest of the tail spar failing under heavy G loading.
One other thing I've noticed is how much braver some opponents become once I lose half a stab. I had a bunch of planes bnzing me last night and only realised I'd lost half my stab after a couple of them made the mistake of trying to turnfight me. :D
With or without 1/2 of your horz. stab, you are one hell of an opponent!
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I'd think that only having one of the horizontal stabilizers would make the remaining one very weak due to the loss of counterbalancing of forces as well as having the horizontal stabilizer's spar severed.
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Waitin' for HiTech's reply :D
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I'd think that only having one of the horizontal stabilizers would make the remaining one very weak due to the loss of counterbalancing of forces as well as having the horizontal stabilizer's spar severed.
Here's an F4U tailplane being mounted. Note the lack of spar. I don't see where the remaining tailplane would have a strength issue pushing the tail down. Other aircraft construction may vary but I'd be surprised if they didn't design them to tolerate the loss of the opposite tailplane.
(http://www.mediafire.com/conv/d922fa10313a7e08cc0e806831c420cc44319f8ba1b0298a268e9e65ff5507944g.jpg) (http://www.mediafire.com/imageview.php?thumb=5&quickkey=qo0129ug8z3gbtu)
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Thanks Fester.
That is the thing I wanted to post.
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Here's an F4U tailplane being mounted. Note the lack of spar. I don't see where the remaining tailplane would have a strength issue pushing the tail down. Other aircraft construction may vary but I'd be surprised if they didn't design them to tolerate the loss of the opposite tailplane.
(http://www.mediafire.com/conv/d922fa10313a7e08cc0e806831c420cc44319f8ba1b0298a268e9e65ff5507944g.jpg) (http://www.mediafire.com/imageview.php?thumb=5&quickkey=qo0129ug8z3gbtu)
That picture is misleading and makes one think the spars are not continuous when installed.
While they are indeed separate parts, the horizontals are mirror image assemblies, and in the F4u series have a rear and forward spar. They just are not connected conventionally like most are used to. Instead, the horizontals use a massive forged steel fitting that is mounted to the airframe to connect the rear spars. These connections are made with special bushings that are secured by taper pins. The forward spars are connected to the fuselage on each side by long steel pins into an aluminum fastener that is locked in with a dzus spring. Further, the inboard edges of the horizontals are further screwed into nut plates with counter sunk #10 screws that are attached to the structural fairing that forms the gap between the fuselage and horizontal. Beyond a shadow of a doubt, it is one of the toughest structures I have seen in an American Fighter.
In my opinion though, the complete loss of one side would be hard to accomplish without catastrophic damage to the other, as the elevators are connected completely through the assembly with the trim chain running on the sprocket halves in the center of the assembly.
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Thanks for filling in the details Bodhi. My point was the lack of a spar going through the fuselage. I don't see how the picture is misleading when there is not a spar connecting the tailplanes. You seem to be agreeing that each tailplane has a spar bolted to the fuselage and the spars do not connect the tailplanes to each other. I assume there is sufficient bracing in the fuselage but calling that a continuous spar seems more to describe an effect than an actuality.
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FLS,
The fitting in the rear does connect the rear spars together, as a continuous spar. The forward spars are connected through the forward fittings attached to actual structure, but not as "directly" or continuous, but they do connect through an intermediary structure.
Sorry for the confusion.
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This is what I'm looking at. It also shows the beam that connects the wings.
http://www.mediafire.com/download.php?b417jhtebj48jx2
I'm not saying you're wrong. I can accept a 3 piece spar, I'm assuming there's nothing major missing in the diagram, but not being an engineer I would describe this as 2 tailplanes bolted to a fuselage.
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FLS,
I worked on the -4 for a number of years and know it fairly well. I am not claiming to "know-it-all", I've just spent significant time around the airframe.
The IPB pages you are showing are just rough group assembly sketches. Let me see if I can dig up some photos, if not, I will be at my hangar on Friday and I will grab the IPB and scan the parts page for you showing what I am talking about. The spars carry through with alternate structure in the front and with a gigantic, 10 - 15 lb forging in the rear.
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I'll take your word for it Bodhi, I've never looked inside one. It would be interesting to see if it's not too much trouble.
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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.
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This 47D made it home after a mid-air collision.
(http://www.bigwing.net/images/56th%2022.jpg)
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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. :O
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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.
(http://i168.photobucket.com/albums/u191/bodhi83/DSCN6258.jpg)
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.
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This 47D made it home after a mid-air collision.
(http://www.bigwing.net/images/56th%2022.jpg)
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/
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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.
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Once joined they are a single spar as they are continuous.
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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.
(http://i168.photobucket.com/albums/u191/bodhi83/DSCN6258.jpg)
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?
:salute
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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?
:salute
Attach points for the actual elevator?
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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 :rock
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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.
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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.... :o
Sure must be nice working on those birds but I bet it gets frustrating at time too.
:salute
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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.
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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.
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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.
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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.
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I'm reading a book on VT-4 in WW2. I just read about a TBM that dove steeply, pulled out, and lost one stabilizor and elevator. Flew back and landed on the CV with no control issues.
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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/
lol at least that p47 was a gift :D