High sulfur steel

The steel that was used for Titanic had a high sulfur content. This made it brittle, more like cast iron than modern steel. The problem was made worse by the cold water temperature of the North Atlantic. Thus, when the ship hit the iceberg the iceberg itself didn’t do a whole lot of damage, but because the steel was so brittle the plates cracked open and didn’t stop until the crack reached the next row of rivets. Nobody understood this until World War II when the same problem showed up in liberty ships that were taking cargoes to Russia’s Arctic Ocean ports.

Does anyone know if the same problem existed in World War II era aircraft which were exposed to cold temperatures during high altitude flights?

Metal fatiguewas a known issue. This applied to better quality steel also. During WWII the problem wasn’t well understood, but I believe the steel used in planes of that time would not have a high sulfur content and would have been better formulated to deal with the stresses involved. You can see from the wiki article that were two well established cases of mid-air breakups of de Havilland Comet jets due to metal fatigue.

The steel plates used for the Titanic’s hull had a high (compared to today’s standards) sulfur (and phosphorus) contents, which resulted in the steel becoming brittle at low temperatures. That is, steels with lower S & P contents are much less brittle, particularly at lower temperatures. This is not to say the steel used for the Titanic’s hull was sub-standard, but that the technology in steelmaking and testing has improved greatly in the last 100 years.

As you mention, the problem was similar to what caused problems with the Liberty Ships, although my understanding is the problems with the Liberty Ships had additional contributions from welding practices (the Titanic was riveted, not welded) and design issues that were employed in the manufacture of the Liberty Ships that allowed them to be produced at the high rate needed by the war effort.

The steels used for aircraft were made to different standards than those used in the ships. The steels used in aircraft were produced to much higher strength levels (to save weight) and as a result, had to be produced from steels that were not as brittle at lower temperatures. In addition, I don’t think welding was used as much in aircraft manufacture; most joints were riveted (think Rosie the Riveter). Although the nature of brittle failure was still not well understood, the steel processing and manufacturing practices used for aircraft were more resistant to brittle failure.

How much steel exposed to low temperatures would have been in a typical WW-2 aircraft?

There would have been some in the control system, but I’d guess rather little that was structural.


Other than engine blocks and landing gear legs, darn near everything big or structural in a WWII airplane is aluminum not steel. Other than those few big lumps, steel is used in bearings, bolts, braided tension cables & the like. By volume it’s a tiny fraction of the aircraft.

What kind of trade off was there in making aircraft from aluminum to save weight as opposed to steel which might have been able to withstand anti-aircraft fire better than aluminum? Considering what it took to train pilots and aircrews, was any thought ever given to armor plating on aircraft so fewer planes would have been shot down?

Weight, mainly, and therefore performance (speed, maneuverability, and fuel consumption). The added weight would mean heavier, more powerful engines, and more fuel to feed them. How much more engine power would an all steel plane take to have equal performance to an aluminum one, if possible? I don’t know, but it would have been a lot.

I don’t think that steel was ever seriously in contention to be used as a structural material in aircraft. The strength to weight ratio of both aluminum and steels has improved over the decades as new alloys were developed but both were roughly equal, and considering other manufacturability factors, aluminum wins out. An armored aircraft would not fly very well, if anything the only thing to protect are engine and control hydraulic lines.

There was (and still is) armor plate to protect various areas of aircraft. More specifically the pilot, but sometimes included some SMALL protection for the engine or oil/fuel tanks. Fuel tanks were usually self sealing instead of actually “armor” plated.

There couldn’t be too much steel in an aircraft, simply for weight savings. Too much weight, especially in the wrong areas severely affect performance, as it would require more engine power to overcome it, and the aircraft usually had the highest horsepower engines available already. If an aircraft is too slow or unmanuverable it would be MORE vulnerable then it would be with no armor at all. And going to extremes with armor won’t help, because you can’t protect from EVERYTHING.

The Japanese aircraft were notorious for this, because they took it to the extreme of having no armor at ALL or self sealing tanks, and even the structural members were taken to their limits of lightness. They had amazing performance for their time and horsepower (maneuverability, range), outclassing all the allied aircraft. However this could be beat by the proper tactics. And the Japanese aircraft were extremely vulnerable when under fire, often lighting up like torches.

American aircrews in Europe had some of the highest casualty/capture rates of any allied personnel. The War Department put more emphasis on destroying the Luftwaffe to make way for D-Day than it did on saving men and materiel. General Doolittle actually ordered fighter pilots to abandon the bombers they were escorting as soon as they encountered Luftwaffe fighters. The bomber crews, however, were not informed of Doolittle’s tactics. We sacrificed bombers and their crews in order to eliminate Luftwaffe fighter planes.

That’s IMO a totally invalid criticism probably based on some critical misunderstandings.

The US fighters were up there to protect the US bombers. But they don’t do that by flying passively alongside them. They do that by vigorously engaging any Luftwaffe fighters immediately upon detecting them; i.e. before they can get within firing range of the bombers. As well, once the Luftwaffe fighters are amongst the bombers, it becomes much harder for the bomber’s gun crews to fire freely when their formation is also full of US fighters. Fratricidal collisions also become an issue.

His real innovation was to send the US fighters out ahead of the US bombers by just a few minutes to clear a path through the Luftwaffe fighters. Given the response time of the Luftwaffe defenses, this was effective at eliminating the fighter opposition before it could get near the bombers while not giving the Luftwaffe time to launch a second wave to attack the bombers shortly behind. The net result was a reduction in bomber casualties, not an increase.

Had Doolittle refused to provide bomber escorts at all, and instead sent his fighters out on separate search and destroy missions you’d have a valid complaint. Recall also that Doolittle himself was a bomber general, hardly someone deaf to the needs of his men.
Fighters escorting heavy bombers is a tactic of the past. But even today modern fighter bombers / fast attack aircraft use similar tactics. Typically the first few aircraft in a formation are dedicated to counter-air while the bulk of the ground attack force follows hard on their heels. It worked then and it works now.

Yes. I recall seeing the results of recycling the planes after the war. By weight there was twice as much aluminum as steel, and most of the steel had to come from the engines. So hard points, hardware, and perhaps a small number of structural pieces.

Very true. The Germans did make a beefed up version of their FW 190, the FW 190 A-8 which had 5 mm plate armor around the cowling to protect the engine as well as the armored glass canopy from an earlier version as a bomber-killer to go after the B-17s and B-24s. The changes were documented in November of 1944. While it was more effective against the bombers, the added weight negatively affected performance vis-a-vis the P-51 which were escorting the bombers. These heavier bombers required their own escorts, lighter fighters to fight off the Mustangs, or at least that was how is was supposed to go in theory. When the FW 190 A-8s did get through the P-51s, they were more effective against the bombers, but the armor plating wasn’t popular with the pilots who were too worried about getting killed by the Mustangs.

And it should be noted that the while Zero was superior in maneuverability and range to Allied fighters (but not speed to Spitfire) at the start of the war, US advances with other models quickly equaled and then surpassed the A6M. The Japanese were not able to continue their aircraft development and finished the war with essentially the same ones they started with.

I don’t remember what I was watching, but the claim comes from a documentary that I saw either on the History Channel or PBS. Prior to D-Day the objective of allied bombing missions was to engage the Luftwaffe fighters and any damage the bombers could do on the ground was secondary.

Sounds likely that you understood the documentary just fine. And the goofballs at the False History Channel concocted yet another lame-assed story to generate eyeballs.

I’m inclined to hear a ring of truth in it. As long as Germany had fighter aircraft in significant numbers it would have been impossible for the Allies to invade France. But, until allied bombers could take out Germany’s industry so we could shoot down German fighters faster than the Germans could replace them, the only thing we could do was use our bombers as bait for the German fighters. What I find objectionable is not making it clear to the bomber crews that they were just there as bait. If the airmen knew this going in, they might not have been so willing to join the Air Corps.

My emphasis.

As LSLGuy indicated, it’s not wise to take False History Channel seriously.

This is another case where they have created something from whole cloth.

The Allies, in this case Britain and the US were conducting bombing raids over Germany well before they had long distant fighters to escort them. Those were the days when the casualties were the highest, much more so than after the US had long distant fighters, the P-51.

Casualties had gotten so high that the US had to suspend deep penetration raids. The Schweinfurt–Regensburg mission in August lost 60 B-17s of a force of 376, the 14 October attack lost 77 of a force of 291—26% of the attacking force. Losses were so severe that long-range missions were called off. This was suspended until they could get escorts.

Once they were able to escort the bombers, which helped, then the changed to the tactics you don’t like. When they did, it was remarkable effective. From wiki.

From Wikipedia:

Doolittle’s major influence on the European air war occurred early in the year when he changed the policy requiring escorting fighters to remain with the bombers at all times. With his permission, initially performed with P-38s and P-47s, as both previous types were being steadily replaced with the long-ranged P-51s as the spring of 1944 wore on, American fighter pilots on bomber defense missions would primarily be flying far ahead of the bombers’ combat box formations in air supremacy mode, literally “clearing the skies” of any Luftwaffe fighter opposition heading towards the target. This strategy fatally disabled the twin-engined Zerstörergeschwader heavy fighter wings and their replacement, single-engined Sturmgruppen of heavily armed Fw 190As, clearing each force of bomber destroyers in their turn from Germany’s skies throughout most of 1944. As part of this game-changing strategy, especially after the bombers had hit their targets, the USAAF’s fighters were then free to strafe German airfields and transport while returning to base, contributing significantly to the achievement of air superiority by Allied air forces over Europe.
In other words Doolittle did tell the fighters that they should leave the fighters without escort in order to concentrate on offensive actions against the Luftwaffe.

If you look at development history of almost any WWII aircraft, armor and survivability generally increased with each version of an aircraft. As vulnerabilities were identified they were dealt with. In many fighter craft it is quite obvious if you actually look closely. That flat oval at the front of many canopies was 2" thick armor glass. That isn’t a backrest behind the seat but armor plate protecting the pilot’s back. There was often also armor plate underneath the pilot, and sometimes on the sides.

In some cases armor was removed when the protection gained by it did not make up for the performance loss due to increased weight. There were many cases of field modifications where for example poorly working radios in Zeros, and ineffective wing guns in P39s were removed by crews for performance benefits.

Disagree. The 1941-1942 fighters that were air-cooled and only wing-internal tanks could take more punishments than, say, a P-51 D whose engine was water-cooled, and had an auxiliary tank behind the pilot. A pressurized cockpit was also very vulnerable.