Doing aerobatics in bomb-loaded bombers

[mbailey]

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.

Bet that was great seeing/hearing Tillman speak.

[earl1937]

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°

In the 29, we never did any kind of stalls unless, first, close cowl flaps completely, as they tend to "blank" out the effect of the elevator!

[earl1937]

Would you care to elaborate on that pontification?

While I did not make the comment, maybe I can clear up a couple of points. #1, when you are standing on the ground, you are in effect, pulling 1 G, if you jump up into the air, you are now pulling a negative G. "Tex" Johnson pulled off the famous "barrel roll" in the Boeing 707, because he understood that as long as he was pulling 1.5 g's, he could sit a glasses of water on the instrument panel and it would not overturn. He understood the effect of "g" forces and how they affected the aircraft in flight. The roll it did, put no more stress on the aircraft than if it was flying straight and level.
Comment about the bomb loads on wings and their effect! The wing of an aircraft is designed to support a certain amount of weight and if you exceed that weight, you stand a good chance of wing failure. Example: If your 51D weights 13,500 lbs at takeoff weight, full fuel tanks, drop tanks and rockets, the add 2 1,000 lb bombs, you now have in effect a wing which is designed to carry no more than 13,850 lbs, which now weights 15, 500 lbs, you now are flirting with structural failure, if you add any "g" force, plus or minus because of the additional weight that the wing now has to support.
Don't confuse the antic's of these make believe aircraft in this game with the real thing, because in most cases, you would have  structural failure. Now, that is not to say that a lot of strange things have not happened to aircraft in flight, because we all know, those things do happen and if we knew how forces were applied by chance and God's guiding hand, then we would understand how the crews lived through the incidences.
Good post and some good comments though!

[Cthulhu]

In the 29, we never did any kind of stalls unless, first, close cowl flaps completely, as they tend to "blank" out the effect of the elevator!

Thanks Earl, I thought that's what it was, but I wanted to hear from someone more familiar with the 29.

[Cthulhu]

While I did not make the comment, maybe I can clear up a couple of points. #1, when you are standing on the ground, you are in effect, pulling 1 G, if you jump up into the air, you are now pulling a negative G. "Tex" Johnson pulled off the famous "barrel roll" in the Boeing 707, because he understood that as long as he was pulling 1.5 g's, he could sit a glasses of water on the instrument panel and it would not overturn. He understood the effect of "g" forces and how they affected the aircraft in flight. The roll it did, put no more stress on the aircraft than if it was flying straight and level.
Comment about the bomb loads on wings and their effect! The wing of an aircraft is designed to support a certain amount of weight and if you exceed that weight, you stand a good chance of wing failure. Example: If your 51D weights 13,500 lbs at takeoff weight, full fuel tanks, drop tanks and rockets, the add 2 1,000 lb bombs, you now have in effect a wing which is designed to carry no more than 13,850 lbs, which now weights 15, 500 lbs, you now are flirting with structural failure, if you add any "g" force, plus or minus because of the additional weight that the wing now has to support.
Don't confuse the antic's of these make believe aircraft in this game with the real thing, because in most cases, you would have  structural failure. Now, that is not to say that a lot of strange things have not happened to aircraft in flight, because we all know, those things do happen and if we knew how forces were applied by chance and God's guiding hand, then we would understand how the crews lived through the incidences.
Good post and some good comments though!

I've been a structural engineer with first General Dynamics, and now Lockheed Martin for the last 36 years. (Now they're the same company and the b@stards won't bridge my years of service #! $@*&#! ) Anyway, this is a subject which I feel compelled to weigh in on every time it comes up, because there's a lot of incomplete information, or outright BS floating around.

Thanks Earl for helping to explain the subject.

[Widewing]

Thanks Earl, I thought that's what it was, but I wanted to hear from someone more familiar with the 29.

I would imagine that this was quite a disturbing discovery for the test pilot who stumbled upon it for the first time......

[Karnak]

While I did not make the comment, maybe I can clear up a couple of points. #1, when you are standing on the ground, you are in effect, pulling 1 G, if you jump up into the air, you are now pulling a negative G. "Tex" Johnson pulled off the famous "barrel roll" in the Boeing 707, because he understood that as long as he was pulling 1.5 g's, he could sit a glasses of water on the instrument panel and it would not overturn. He understood the effect of "g" forces and how they affected the aircraft in flight. The roll it did, put no more stress on the aircraft than if it was flying straight and level.
Comment about the bomb loads on wings and their effect! The wing of an aircraft is designed to support a certain amount of weight and if you exceed that weight, you stand a good chance of wing failure. Example: If your 51D weights 13,500 lbs at takeoff weight, full fuel tanks, drop tanks and rockets, the add 2 1,000 lb bombs, you now have in effect a wing which is designed to carry no more than 13,850 lbs, which now weights 15, 500 lbs, you now are flirting with structural failure, if you add any "g" force, plus or minus because of the additional weight that the wing now has to support.
Don't confuse the antic's of these make believe aircraft in this game with the real thing, because in most cases, you would have  structural failure. Now, that is not to say that a lot of strange things have not happened to aircraft in flight, because we all know, those things do happen and if we knew how forces were applied by chance and God's guiding hand, then we would understand how the crews lived through the incidences.
Good post and some good comments though!

Yup.  Different aircraft designs have different failure points.  I seem to recall that for the USAAF fighters were supposed to be able to handle 11 Gs when combat loaded.  If combat loaded for the P-51D is 10,000lbs, that would mean an 110,000lb structural failure point.  Load it up with bombs and rockets and you'll hit that 110,000lb mark at well under 11 Gs.

[Cthulhu]

I would imagine that this was quite a disturbing discovery for the test pilot who stumbled upon it for the first time......

Disturbing is putting it mildly.  lol

Reminds me of the first test flights of one of the later Japanese fighters (can't remember which one). The test pilot was climbing out, raised the gear, and the plane promptly nosed over and crashed, killing the pilot. Soon after, another test pilot repeats the process in a second aircraft, complete with fatal crash. The THIRD test pilot tries his luck, but he has the good sense to climb to about 5k before raising the gear. Sure enough, the moment he raises the gear, hard nose over! But this guy has the time, and altitude to drop the gear, and the hard pitch over disappeared. So the guy lands, and tells the engineers what he thinks is the problem. Sure enough, there was an interference with the retractable tail wheel and the bell crank on the elevator hinge. The tail wheel would come up and jam the elevator hard nose down!

Now if I could just remember which plane it was. I read that story in one of William Green's books.

[colmbo]

In the 29, we never did any kind of stalls unless, first, close cowl flaps completely, as they tend to "blank" out the effect of the elevator!

On the B-24 if the cowl flaps were left open instead of in trail for takeoff you would get buffeting.  There was a crew during the war stateside that bailed from a new B-24 because of unexplained buffeting, turned out to be cowl flaps open.

[Cthulhu]

On the B-24 if the cowl flaps were left open instead of in trail for takeoff you would get buffeting.  There was a crew during the war stateside that bailed from a new B-24 because of unexplained buffeting, turned out to be cowl flaps open.

Now there's a guy who was looking at a career change once his tour ran out. 

[earl1937]

On the B-24 if the cowl flaps were left open instead of in trail for takeoff you would get buffeting.  There was a crew during the war stateside that bailed from a new B-24 because of unexplained buffeting, turned out to be cowl flaps open.

When taking off at Tinian, it was standard practice to close cowl flaps completely beginning takeoff roll, then as we passed 135knots on climb out would go to what ever engineer decided on, which was usually wide open, but at that high of speed, we still would have buffering on the elevators. Those big old R-3350 compounds would heat up in a heartbeat and if they did, we would level after takeoff, just to cool them down before starting a long climb. Sometimes during climb, we would level for cooling purposes.





not sure if these are good pic's of cowl flap positions but I tried to find some.

[Cthulhu]

When taking off at Tinian, it was standard practice to close cowl flaps completely beginning takeoff roll, then as we passed 135knots on climb out would go to what ever engineer decided on, which was usually wide open, but at that high of speed, we still would have buffering on the elevators. Those big old R-3350 compounds would heat up in a heartbeat and if they did, we would level after takeoff, just to cool them down before starting a long climb. Sometimes during climb, we would level for cooling purposes.
(Image removed from quote.)

(Image removed from quote.)


not sure if these are good pic's of cowl flap positions but I tried to find some.

Earl, any idea if the problem was even worse on the B-50? I'm thinking it would be.

[earl1937]

Earl, any idea if the problem was even worse on the B-50? I'm thinking it would be.

All I know about the B-50 are just things I heard! But I would guess that it was a serious problem to, because the B-50 had the P&W R-4360 engine, which was much larger than the 3350 and I would think the cowl flap openings were larger, but don't really know.

not a very good pic, have not learned how to enlarge photo's that I copied on line yet, maybe someone can tell me.

[Puma44]

Now there's a guy who was looking at a career change once his tour ran out. 

The way those things tended to go, the guy probably made all his future promotions and retired as a general officer.  

[FLS]

While I did not make the comment, maybe I can clear up a couple of points. #1, when you are standing on the ground, you are in effect, pulling 1 G, if you jump up into the air, you are now pulling a negative G. "Tex" Johnson pulled off the famous "barrel roll" in the Boeing 707, because he understood that as long as he was pulling 1.5 g's, he could sit a glasses of water on the instrument panel and it would not overturn. He understood the effect of "g" forces and how they affected the aircraft in flight. The roll it did, put no more stress on the aircraft than if it was flying straight and level.
Comment about the bomb loads on wings and their effect! The wing of an aircraft is designed to support a certain amount of weight and if you exceed that weight, you stand a good chance of wing failure. Example: If your 51D weights 13,500 lbs at takeoff weight, full fuel tanks, drop tanks and rockets, the add 2 1,000 lb bombs, you now have in effect a wing which is designed to carry no more than 13,850 lbs, which now weights 15, 500 lbs, you now are flirting with structural failure, if you add any "g" force, plus or minus because of the additional weight that the wing now has to support.
Don't confuse the antic's of these make believe aircraft in this game with the real thing, because in most cases, you would have  structural failure. Now, that is not to say that a lot of strange things have not happened to aircraft in flight, because we all know, those things do happen and if we knew how forces were applied by chance and God's guiding hand, then we would understand how the crews lived through the incidences.
Good post and some good comments though!

Since each additional g adds the total aircraft weight to the wing load you just have to reduce max g by 2.5 to stay within the wing limit for the P-51. Not saying something else won't break.

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.

Good luck flying a 1g loop.  I hope you mean keep some positive g when inverted.