Doing aerobatics in bomb-loaded bombers

[bozon]

whats the difference between a p-38 with 2 1000 lb bombs on the wings verses an A-20 with 4 500 lb bombs on the wings ?
 or a mossi or a 110 ?
 i know for a fact that wings come off of A-20 alot easyer when you have bombs strapped on vs empty,is this same true for 38 ?
 i dont think i recall ever ripping wings off a 38 that was heavy trying to do a hard G turn,but if you try it in a A20 you are back in tower.
 so, i would say that there is definatly  a differance between modeling with bomb load compared to no bomb load.

Yes, AH breaks the wings at a given amount of force. Same G load with more weight means more lift is produced by the wings, so 6G in an empty plane may be fine, but 6G in a fully loaded plane will break the wings. Pulling high G in the Mossie with 2*500 in the bay is dangerous, especially with more than 50% fuel on board. I broke my wings many times.

The distribution of the weight is supposed to matter in RL, but I do not know how the game handles it. In principle, putting all the weight in the center (bomb bay) will increase the load on the wing root, as opposed to distributing some of the weight to the wings. So in principle, carrying bombs in the bay will make the wings more prone to bending and breaking at a certain G , than hanging the same load on the wings (and an empty bay). This is another reason for a variable pitch angle along the wing (and prop blades) so the root has a higher AoA than the tip - to distribute the stress along the wing and make it bend less. Again, I do not know if AH takes this into account or simply use a threshold for the total lift produced by the wing. By this logic, the P-38 with bombs hanging from the wing roots will suffer less at high G than A-20 with a lot of weight in the bomb bay. Then one has to factor in the actual construction of the wing to figure out how much stress can the wing root take.

[DaveBB]

A pilot and engineer on F-16.net claims that carrying bombs on the wings actually reduces the force on the wing when doing maneuvers.  So as the angle of attack increases, the wing generates more lift (ultimately creating so much lift that it exceeds its ultimate strength).  The weight of the bombs are in the opposite direction of this lift.

[Cthulhu]

Yes, AH breaks the wings at a given amount of force. Same G load with more weight means more lift is produced by the wings, so 6G in an empty plane may be fine, but 6G in a fully loaded plane will break the wings. Pulling high G in the Mossie with 2*500 in the bay is dangerous, especially with more than 50% fuel on board. I broke my wings many times.

The distribution of the weight is supposed to matter in RL, but I do not know how the game handles it. In principle, putting all the weight in the center (bomb bay) will increase the load on the wing root, as opposed to distributing some of the weight to the wings. So in principle, carrying bombs in the bay will make the wings more prone to bending and breaking at a certain G , than hanging the same load on the wings (and an empty bay). This is another reason for a variable pitch angle along the wing (and prop blades) so the root has a higher AoA than the tip - to distribute the stress along the wing and make it bend less. Again, I do not know if AH takes this into account or simply use a threshold for the total lift produced by the wing. By this logic, the P-38 with bombs hanging from the wing roots will suffer less at high G than A-20 with a lot of weight in the bomb bay. Then one has to factor in the actual construction of the wing to figure out how much stress can the wing root take.

What you're talking about is minimizing bending moments (and hence bending stresses) by distributing the load (either payload, fuel, or airframe mass) over the span of the wing. The trick is to minimize the separation between the aerodynamic forces (lift) and the opposing inertial forces (payload). Doing so keeps wing bending moments from building up. This is one of the structural advantages of flying wings.

The wing "variable pitch" you're referring to is called washout, and it typically has nothing to do with distributing wing loads. Washout is a design feature which allows the wing to stall "gracefully" at max Alpha while still allowing aileron effectiveness. it does help minimize root bending moments at the limit, but this benefit is purely secondary.

I'm guessing that in order to simplify the modeling of airframe failure, HT is simply using load factor vs aircraft weight, with a failure point for each airframe modeled.

[Cthulhu]

A pilot and engineer on F-16.net claims that carrying bombs on the wings actually reduces the force on the wing when doing maneuvers.  So as the angle of attack increases, the wing generates more lift (ultimately creating so much lift that it exceeds its ultimate strength).  The weight of the bombs are in the opposite direction of this lift.

The guy is right. As I said earlier, the only downside to carrying stores on the wings is the additional inertial loading due to rolling maneuvers. This is typically the designing load condition for wing mounted bomb racks and their attachments to the wing itself.

[mbailey]

Here is a story from I heard from a B-29 pilot.

They were flying over Tokyo on a fire-bombing run.  The fires generated such intense updrafts that, hitting one, his B-29 was slammed up several thousand feet and inverted.  To get out of it, he ended up pulling through a split S to recover.

Pilot Gordon Bennett Robertson Jr.'s first fire-bomb run over Tokyo in March, 1945 took him through boiling thermals produced by the burning city 5,000 feet below. They bounced his B-29 up and down and then flipped the sixty-ton bomber onto its back. He was able to recover only through a Split-S maneuver he'd practiced flying fighters in training.

Barrett Tillman tells this story in his book Whirwind

[Widewing]

In an A-20, you'd run the risk of being pulled off flight duties or maybe worse for doing aerobatics in the plane, loaded or unloaded.  Aerobatics were strictly forbidden in the A-20.

ack-ack

Of course, the USAAF didn't want inexperienced pilots killing themselves. That, however, doesn't mean that the A-20 wasn't capable of impressive aerobatics. It was stressed to 5g positive and 2g negative at max takeoff weight. Ultimate strength was closer to 7g.

Ever watch Bob Hoover do his demonstration in his Shrike Commander?
https://www.youtube.com/watch?v=PftNh_SShlg

[Cthulhu]

Pilot Gordon Bennett Robertson Jr.'s first fire-bomb run over Tokyo in March, 1945 took him through boiling thermals produced by the burning city 5,000 feet below. They bounced his B-29 up and down and then flipped the sixty-ton bomber onto its back. He was able to recover only through a Split-S maneuver he'd practiced flying fighters in training.

Barrett Tillman tells this story in his book Whirwind

From the B-29 manual... I'm sure he pulled it off, but the airframe isn't really designed for it. He probably yielded the structure in the process. Sure as Hell beats dying though

[Cthulhu]

Of course, the USAAF didn't want inexperienced pilots killing themselves. That, however, doesn't mean that the A-20 wasn't capable of impressive aerobatics. It was stressed to 5g positive and 2g negative at max takeoff weight. Ultimate strength was closer to 7g.

Ever watch Bob Hoover do his demonstration in his Shrike Commander?
https://www.youtube.com/watch?v=PftNh_SShlg

Widewing, do you know definitively what limit load was for the heavies? 5g's sounds perfect for the A-20, but I'd be surprised if the big guys were designed to that level.

And btw, what always blew me away about Hoover was what he did with the glass of water. 

[Arlo]

http://www.youtube.com/watch?v=-dOu674barc

[save]

What a bomber does with the bombs unloaded I can understand (example the A20).
Doing the same with half tanks filled, and bombs is what I want to prevent, if they could not do it RL.

The 500mph dives in formation should be subjected to losing drones in my opinion.
The rolling and switching planes to warp the drones should take at least the same penalty.

Shooting with any accuracy over say 2G should be prevented to give the AH fidelity the company claim.

Thanks for a good and civil discussion 

[Cthulhu]

Widewing, I have another question. This is shown in the B-29 manual table for stall speed vs weight for various flap positions. What's your take on this?

WARNING: DO NOT STALL THE AIRPLANE WITH THE COWL FLAPS OPEN MORE THAN 10°

[USCH]

1G is 1G and it does not matter one bit what the view from the cockpit is.

[Brooke]

Barrett Tillman tells this story in his book Whirwind

Hmm.  I might have read it then instead of hearing it, or it could have been from the talk Barrett Tillman gave at the Museum of Flight.

The Museum of Flight has had a lot of panels with WWII pilots.  I've listened to about 75 WWII pilots talk over the years there, and there have been amazing stories.  One was a panel of B-29 pilots.  One was a panel of pilots and Barrett Tillman.  Others have been with pilots of P-51's, P-47's, P-38's, P-40's, P-39's, Mossies, B-17's, B-24's, B-25's, F4U's, F6F's, TBM's, and Spitfires, but I missed my chance to talk to an Me 262 pilot.

[Cthulhu]

1G is 1G and it does not matter one bit what the view from the cockpit is.

Would you care to elaborate on that pontification?

[Karnak]

Would you care to elaborate on that pontification?

If you keep the loading at 1G through whatever maneuver you are doing it doesn't matter to the aircraft where the center of the local gravity well is.  The trick is keeping the G loading close to 1 through a roll or loop or what not.

The comment I referenced earlier about what the A-20 pilots were told, that the wings would fall off if they rolled it inverted, I have no doubt was simply a falsehood to encourage them to not try aerobatics in their A-20s.

As to laden maneuvering, Lancasters did perform the corkscrew evasive with bombs on board.