There is not much to write about the Dornier Do 19. For two reasons: 1) Its career was very short and 2) you can get basic information about it in Wikipedia. As I continue to say, a GOT topic is not a Wikipedia article. It is for aircraft enthusiasts like you, and it is intended to give you information you otherwise won't receive. See below what I mean is interesting about the Do 19.
DID THE DO 19 HAVE PREDECESSORS?
Yes, Dornier was experienced also in building 4-engined landplanes. See pictures of the Do K and P below.
WAS THERE SOMETHING SPECIAL ABOUT THE DO 19?
Despite, or just because of its boxy outlook, the Do 19 was a lot lighter than its contender Junkers Ju 89. Especially the take-off characteristics were exceptional. After only 596 m take-off distance it reached a height of already 20 m.
Source: http://www.klassiker...er-do-19/583156(in German).
HAD THE DO 19 PREVAILED IF IT HAD SHARED IN THE WAR?
This is a bit of a difficult question. It depends on what one sees as success. The aircraft is a creation of the early 30s with all restrictions due to this period of time. For the early phase of the war, I mean it surely were a reinforcement for the Luftwaffe. Consider at this time no air force at all employed a four-engined bomber force. The performance must be seen in the light of its early development. Surely, the range was not enough to reach the Ural mountains, so the imagined use as "Ural bomber" was unrealistic. But the Luftwaffe could have made valuable experience with an aircraft of this size. For the sheer optical similarity I like to compare the Ju 89 with the Halifax, and the Do 19 with the Stirling. With 4 x 1,590 hp, the Stirling runs 419 km/h. The Do 19 did 315 km/h on 4 x 715 hp. Mounting the Stirling's Bristol Hercules [corrected on Kiwi's objection] on the Do 19, and using the cubic root formula, it would make 411 km/h. Without any armament. You see, some areodynamic redesign (probably especially of the wing) would have been required.
WHAT WAS THE REAL REASON FOR DROPPING JU 89 AND DO 19?
There were two reasons, one you can read in Wikipedia, the other not. Both have nothing to do with the death of Luftwaffe chief of general staff Walter Wever, what argument you can read so often. His successor Albert Kesselring in his book "Soldat bis zum letzten Tag", publishing house Siegfried Bublies, Schnellbach 2000, does not mention the four-engined bombers at all. He says he had a very good relatioship to Wever and he just continued the latter's work (page 39f).
The one thing was that a 4-engined, slowly flying bomber of medium range in Germany was seen as tactical fallacy. This lead to a new specification for a fast heavy bomber, which lastly resulted in the Heinkel He 177. This specification was spread on the day of Wever's death, so the drafting of it must have been done with Wever's knowledge.
The other reason is that the German arming process in early 1937 ran into a crisis. Especially the aircraft industry could not manage to educate all the new employees it had to, so the workforce rose in number, but the output languished or even sank. Also, the exports suffered, because most of the workforce was needed for the arming process. The monetary reserves dwindled, and valuable raw materials could not be imported, as the arming process, especially for the air armamant, would have needed them. So, in May 1937 (nearly one year after Wever's death), it was decided to stop the extension of the aircraft industry. The subsequent budget reductions also hit the acquisition of aircraft. Do 19 and Ju 89 were among the victims.
Source: Lutz Budraß (his name ending in another special German letter just to tease you), Flugzeugindustrie und Luftrüstung in Deutschland 1918 - 1945, publisher Droste Verlag GmbH, Düsseldorf 1998. Pages 481 - 483 to the crisis in the arming process, page 528f note 202 to the new bomber specification and the dropping of the long-range bombers. Budraß does not mention the Do 19 explicitly, he says: "...die Maschinen von Junkers und Dornier...". He mentioned the Ju 89 before, so there is no other solution that the one of Dornier he talks about is the Do 19.
There are nearly no good pictures of the Do 19 on the net. So we here have the paradoxic situation that the Do 19s predecessors deliver better pictures than the GOT-described aircraft itself.
#1: Do K (a passenger plane, source given):
#2: same (source: Dan Shumaker's collection):
#3: Do P (swiss-registered bomber, Germany was still not allowed to construct warplanes, source Nhungdoican's blog, but also available in Wikipedia):
#4: Do 19 (source: Klassiker der Luftfahrt):
All pictures a bit improved using XnView, as usual.
Hope you enjoyed, and regards,