- History of Dornier 17 (Rex's Hangar Youtube Channel)
history of Dornier 17
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- History of Dornier 17 (Rex's Hangar Youtube Channel)
Hi,
Thanks a lot for the link!
I really wonder where the author got his data from ... just 320 km combat radius for the Do 17Z-2 with Bramo 323P with a 1000 kg bomb load?
View: https://www.youtube.com/watch?v=grvkSRGIFu8&t=1877s
The Baubeschreibung for the type shows 1115 kg of fuel available for that case, and the Bramo 323P at maximum continuous power yields 600 HP at 226 g/HP/h. That's a fuel consumption of 136 kg/h per engine, or better than 4 hours of flight. At maximum continous power, the speed of the Do 17 Z-2 was well above 320 km/h ... obviously, combat radius should have been in excess of 640 km.
Looking at the Baubeschreibung data sheets, I wonder if the problem really is a misunderstanding of the original German range table ...
Funnily enough, there is indeed a value of "320" associated with the 1000 kg bomb load case.
However, if one pays attention to the "km/h" unit at the end of row, it's clear that this can't be a combat radius, but it has to be a speed. If one understands (technical) German, the Legend "v Reise bei G mittel" specifies that this is the cruise speed at "average" flying weight. ("Average" means the average between specified take-off and landing weight.)
The markings help to connect the data description (in ellipses) to the data values (in squares), with the red markings showing the 0 km altitude, 1000 kg bomb load case, and the blue marking the associated average cruise speed.
Now admittedly, that's the table for the Do 17 Z with Bramo 323A, so if this table is fact the basis for the suspect "320 km combat radius" figure, the author would have had to make the additional mistake of confusing this table with its almost identical twin showing the data for the Bramo 323P. (For perspective, it shows 1260 km range ... 100 km less than the Bramo 323A table ... and 342 km/h cruise speed ... 22 km/h more.)
Still, the 320 km combat radius seems too short by at least a factor of two. Even allowing for the possiblity that a Do 17 under operational conditions might not have performed according to the hand book numbers, I can't imagine the engines could have doubled their fuel consumption, or the aircraft have halved its cruise speed, to allow it to meet that 320 km comat radius! :-D
Regards,
Henning (HoHun)
Thanks a lot for the link!
I really wonder where the author got his data from ... just 320 km combat radius for the Do 17Z-2 with Bramo 323P with a 1000 kg bomb load?
The Baubeschreibung for the type shows 1115 kg of fuel available for that case, and the Bramo 323P at maximum continuous power yields 600 HP at 226 g/HP/h. That's a fuel consumption of 136 kg/h per engine, or better than 4 hours of flight. At maximum continous power, the speed of the Do 17 Z-2 was well above 320 km/h ... obviously, combat radius should have been in excess of 640 km.
Looking at the Baubeschreibung data sheets, I wonder if the problem really is a misunderstanding of the original German range table ...
Funnily enough, there is indeed a value of "320" associated with the 1000 kg bomb load case.
However, if one pays attention to the "km/h" unit at the end of row, it's clear that this can't be a combat radius, but it has to be a speed. If one understands (technical) German, the Legend "v Reise bei G mittel" specifies that this is the cruise speed at "average" flying weight. ("Average" means the average between specified take-off and landing weight.)
The markings help to connect the data description (in ellipses) to the data values (in squares), with the red markings showing the 0 km altitude, 1000 kg bomb load case, and the blue marking the associated average cruise speed.
Now admittedly, that's the table for the Do 17 Z with Bramo 323A, so if this table is fact the basis for the suspect "320 km combat radius" figure, the author would have had to make the additional mistake of confusing this table with its almost identical twin showing the data for the Bramo 323P. (For perspective, it shows 1260 km range ... 100 km less than the Bramo 323A table ... and 342 km/h cruise speed ... 22 km/h more.)
Still, the 320 km combat radius seems too short by at least a factor of two. Even allowing for the possiblity that a Do 17 under operational conditions might not have performed according to the hand book numbers, I can't imagine the engines could have doubled their fuel consumption, or the aircraft have halved its cruise speed, to allow it to meet that 320 km comat radius! :-D
Regards,
Henning (HoHun)
Of course 320 km or 330 km like wikipedia eng report ( https://en.wikipedia.org/wiki/Dornier_Do_17) was referred to maximum load of bombs for version Z-2 @ lower altitudes.
Hi,
Sorry, I don't actually consider Wikipedia a reliable source.
What the historic Baubeschreibung actually says is that the range of the Dornier Do 17 Z-2 with Bramo 323 P engine flying at (uneconomical) maximum continous power at at (worst case for range) sea level with a 1000 kg bomb load is 1260 km.
That would be equivalent of a combat radius in the region of 630 km. If you tell me it's just half that, I'm not going to believe that unless you provide a very good explanation based on reliable sources.
Note that the optimum range of the Dornier Do 17 Z-2 with Bramo 323 P engine carrying a 1000 kg bomb load flying at economic parameters is 1910 km.
Regards,
Henning (HoHun)
Sorry, I don't actually consider Wikipedia a reliable source.
What the historic Baubeschreibung actually says is that the range of the Dornier Do 17 Z-2 with Bramo 323 P engine flying at (uneconomical) maximum continous power at at (worst case for range) sea level with a 1000 kg bomb load is 1260 km.
That would be equivalent of a combat radius in the region of 630 km. If you tell me it's just half that, I'm not going to believe that unless you provide a very good explanation based on reliable sources.
Note that the optimum range of the Dornier Do 17 Z-2 with Bramo 323 P engine carrying a 1000 kg bomb load flying at economic parameters is 1910 km.
Regards,
Henning (HoHun)
i consider Wikipedia english reliable : i attach the mention of Chis Gross ( note 14° of Dornier 17 wikipedia) : from Dornier 17 Units WW2 - Osprey Publishing
Attachments
Hi,
Thanks for checking the foot note and providing a book source! That's much better than pure Wikipedia
Still, where does Goss get the figure from? Does he provide any reason why the combat radius was supposed to be so short, and what does he say about the combat radius of other versions?
As I said, without a very good explanation why the combat radius should fall short of the Baubeschreibung value by a factor of two, I'm not going to believe it.
The claim of a ca. 320 km combat radius was already in the first version of the Wikipedia article from 2003, and from all I know, Goss might have based his book on the Wikipedia article!
Regards,
Henning (HoHun)
Thanks for checking the foot note and providing a book source! That's much better than pure Wikipedia
Still, where does Goss get the figure from? Does he provide any reason why the combat radius was supposed to be so short, and what does he say about the combat radius of other versions?
As I said, without a very good explanation why the combat radius should fall short of the Baubeschreibung value by a factor of two, I'm not going to believe it.
The claim of a ca. 320 km combat radius was already in the first version of the Wikipedia article from 2003, and from all I know, Goss might have based his book on the Wikipedia article!
Regards,
Henning (HoHun)
Henning your reaction seems be biased: stay focus on topic. You will find more books of Chris Goss also on. Crecy.co.uk . I construe 320 km of combat radius with 1000 kg with lower altitude than 2000 m.
Hi,
Sure I'm biased ... I'm biased towards diligent research, transparent sources, and cross-checking the engineering realities of aircraft design.
Chris Goss is contradicting primary documentation ... if all he has in print is just that single number you quoted, that's not the "very good explanation based on reliable sources" I asked for.
You seem to have the book ... does he say anything on the background for this dramatic, catastrophical shortfall in predicted range?
This is engineering - range doesn't just decide to sneak out through the backdoor while you're not looking, there must be real physical engineering reasons if an aircraft doesn't perform as planned.
We know the amount of fuel in the tanks, the fuel consumption of the engine, and the cruise speed of the aircraft. We can calculate range from that. If the range is just half what it should be, either ...
- the tanks were just half as big as planned,
- the engines were twice as thirsty as advertised, or
- the cruise speed of the aircraft was only half as high as expected.
So what is it? If Goss tells us neither where the number is from nor why it is so low, it would be the mark of a poor researcher to take it at face value.
Based on what? That's not exactly transparent ...
Regards,
Henning (HoHun)
Sure I'm biased ... I'm biased towards diligent research, transparent sources, and cross-checking the engineering realities of aircraft design.
Chris Goss is contradicting primary documentation ... if all he has in print is just that single number you quoted, that's not the "very good explanation based on reliable sources" I asked for.
You seem to have the book ... does he say anything on the background for this dramatic, catastrophical shortfall in predicted range?
This is engineering - range doesn't just decide to sneak out through the backdoor while you're not looking, there must be real physical engineering reasons if an aircraft doesn't perform as planned.
We know the amount of fuel in the tanks, the fuel consumption of the engine, and the cruise speed of the aircraft. We can calculate range from that. If the range is just half what it should be, either ...
- the tanks were just half as big as planned,
- the engines were twice as thirsty as advertised, or
- the cruise speed of the aircraft was only half as high as expected.
So what is it? If Goss tells us neither where the number is from nor why it is so low, it would be the mark of a poor researcher to take it at face value.
Based on what? That's not exactly transparent ...
Regards,
Henning (HoHun)
Probably there are some conflicting data . On Wikipedia some voices are best explained in english , sometimes in italian or germany . Like a free encyclopedia is a good point to start for newbies and passionates . Surely Is not reliable @ 100%
Hi,
Well, I'm not so optimistic about Wikipedia, but there are in fact some good authors on there. The problem is, the Wikipedia is not designed to allow linking of content to authors, and accordingly, reliability is a real can of worms.
I absolute agree with your approach to cross-check the footnote against the book, and that it matches the article's claim is a good start. Over the years, I've discovered that's not always the case - but of course, I'm biased towards mostly checking the really suspicious ones
I have actually experienced "citogenesis" as shown in the comic I linked. I wrote some paragraphs for a Wikipedia article, they were lifted by a popular website that didn't indicate they got their text from Wikipedia, and soon after, the Wikipedia article received a footnote citing the thieving website as the source of the paragraphs I had written!
Probably the worst case, and I didn't mean to suggest that Chris Goss actually got his combat radius figure from Wikipedia. It's just that in the absence of information about his sources, we can't even rule out the worst case.
Quite possible, and I'm curious about the background of this issue! The Wikipedia article at least shows it has been around even before Chris Goss' book was published, and it's worth noting that the author of the video you linked also considered research on the Do 17 to be really difficult with several conflicting origin stories, so the Do 17 seems to be a tough nut for historians all around!
Regards,
Henning (HoHun)
Well, I'm not so optimistic about Wikipedia, but there are in fact some good authors on there. The problem is, the Wikipedia is not designed to allow linking of content to authors, and accordingly, reliability is a real can of worms.
I absolute agree with your approach to cross-check the footnote against the book, and that it matches the article's claim is a good start. Over the years, I've discovered that's not always the case - but of course, I'm biased towards mostly checking the really suspicious ones
I have actually experienced "citogenesis" as shown in the comic I linked. I wrote some paragraphs for a Wikipedia article, they were lifted by a popular website that didn't indicate they got their text from Wikipedia, and soon after, the Wikipedia article received a footnote citing the thieving website as the source of the paragraphs I had written!
Probably the worst case, and I didn't mean to suggest that Chris Goss actually got his combat radius figure from Wikipedia. It's just that in the absence of information about his sources, we can't even rule out the worst case.
Quite possible, and I'm curious about the background of this issue! The Wikipedia article at least shows it has been around even before Chris Goss' book was published, and it's worth noting that the author of the video you linked also considered research on the Do 17 to be really difficult with several conflicting origin stories, so the Do 17 seems to be a tough nut for historians all around!
Regards,
Henning (HoHun)
So wikipedia can be considereed for general knowlegde not for specific topic. For voice Do-17 seems be more reliable italian wiki and germany wiki topic about it. Obviously for more details books are essencials.
Hi,
While Wikipedia is very useful, I think one needs more cross-checking skills today than one needed in the past, when a long memory was more important
The Italian Wikipedia article on the Do 17 seem to be a good example for the conflicting information you mentioned:
Am I right that "autonomia" is best translated "combat radius"? If the same applies to "distanza massima operativa", we have at least two figures that match, though I'll admit that latter sounds more like "maximum operational range" to me.
This drawing shows the tanks for the Do 17 Z:
Note that the central tank is a bomb bay tank - it can be installed and removed as required for the mission, and when it's installed, it blocks on of the two bomb bays of the Do 17 Z.
In my opinion, someone misunderstood this completely and came up with a train of reasoning like ... "The Do 17 Z-1 had a long range but could only carry 500 kg of bombs, and then the Do 17 Z-2 came out with a more powerful engine, so it could carry 1000 kg of bombs ... but oh my god, its range was so short now! It must have been the fault of the engines."
This is of course nonsense ... compare:
Do 17 Z with Bramo 323 A, with 500 kg bombs and the bomb bay fuel tank installed: 8640 kg take-off weight
Do 17 Z with Bramo 323 A, with 1000 kg bombs and the bomb bay fuel tank installed: 8345 kg take-off weight
Do 17 Z with Bramo 323 P, with 1000 kg bombs and the bomb bay fuel tank installed: 8640 kg take-off weight
(The Bramo 323 P engines were 20 kg heavier in total than the Bramo 323 As, so the Do 17 Z-2 was fueled with 20 kg less fuel for the same take-off weight as the Z-1. The bomb bay tank was not filled to the brim in both cases - to do so without exceeding maximum take-off weight, the bomb load had to be reduced by one 50 kg bomb. There's a 450 kg bomb load case in the tables I posted above - now we know how they arrived at that odd number! .)
So the Do 17 Z-1 could carry the 1000 kg bomb load just as the Z-2, and the range of the Z-2 was for all practical purposes about the same the Z-1's for the same payload configuration.
The relevant engine parameters for sea level performance/range:
Bramo 323 A take-off power: 900 HP @ 2500 rpm/1.43 ata
Bramo 323 P take-off power: 1050 HP @ 2500 rpm/1.43 ata
Bramo 323 A continuous power: 585 HP @ 2100 rpm, 225 g/HPh specific fuel consumption
Bramo 323 P continuous power: 680 HP @ 2100 rpm, 217 g/HPh specific fuel consumption
So somewhat counter-intuitively, the Bramo 323 P, at equivalent power settings, was actually a more economic and less thirsty engine. The reason for this is that this engine model had a two-speed supercharger, compared to the Bramo 323 A's single-speed supercharger, so the Bramo 323 P at low altitude expended less of its power for pumping air while also running more efficiently.
In other words, the traditional narrative on the Do 17 Z history doesn't make any sense at all, it's not only the numbers that are off, but basically the entire story about the weak, disappointing Z-1 and the more powerful, thirsty, short-range Z-2. Not to say it's like that in Goss' book, as I don't actually know that ... I'm just summarizing what is a bit of a recurring motif in the various Wikipedia articles and other online sources.
Regards,
Henning (HoHun)
While Wikipedia is very useful, I think one needs more cross-checking skills today than one needed in the past, when a long memory was more important
The Italian Wikipedia article on the Do 17 seem to be a good example for the conflicting information you mentioned:
Am I right that "autonomia" is best translated "combat radius"? If the same applies to "distanza massima operativa", we have at least two figures that match, though I'll admit that latter sounds more like "maximum operational range" to me.
This drawing shows the tanks for the Do 17 Z:
Note that the central tank is a bomb bay tank - it can be installed and removed as required for the mission, and when it's installed, it blocks on of the two bomb bays of the Do 17 Z.
In my opinion, someone misunderstood this completely and came up with a train of reasoning like ... "The Do 17 Z-1 had a long range but could only carry 500 kg of bombs, and then the Do 17 Z-2 came out with a more powerful engine, so it could carry 1000 kg of bombs ... but oh my god, its range was so short now! It must have been the fault of the engines."
This is of course nonsense ... compare:
Do 17 Z with Bramo 323 A, with 500 kg bombs and the bomb bay fuel tank installed: 8640 kg take-off weight
Do 17 Z with Bramo 323 A, with 1000 kg bombs and the bomb bay fuel tank installed: 8345 kg take-off weight
Do 17 Z with Bramo 323 P, with 1000 kg bombs and the bomb bay fuel tank installed: 8640 kg take-off weight
(The Bramo 323 P engines were 20 kg heavier in total than the Bramo 323 As, so the Do 17 Z-2 was fueled with 20 kg less fuel for the same take-off weight as the Z-1. The bomb bay tank was not filled to the brim in both cases - to do so without exceeding maximum take-off weight, the bomb load had to be reduced by one 50 kg bomb. There's a 450 kg bomb load case in the tables I posted above - now we know how they arrived at that odd number!
.)So the Do 17 Z-1 could carry the 1000 kg bomb load just as the Z-2, and the range of the Z-2 was for all practical purposes about the same the Z-1's for the same payload configuration.
The relevant engine parameters for sea level performance/range:
Bramo 323 A take-off power: 900 HP @ 2500 rpm/1.43 ata
Bramo 323 P take-off power: 1050 HP @ 2500 rpm/1.43 ata
Bramo 323 A continuous power: 585 HP @ 2100 rpm, 225 g/HPh specific fuel consumption
Bramo 323 P continuous power: 680 HP @ 2100 rpm, 217 g/HPh specific fuel consumption
So somewhat counter-intuitively, the Bramo 323 P, at equivalent power settings, was actually a more economic and less thirsty engine. The reason for this is that this engine model had a two-speed supercharger, compared to the Bramo 323 A's single-speed supercharger, so the Bramo 323 P at low altitude expended less of its power for pumping air while also running more efficiently.
In other words, the traditional narrative on the Do 17 Z history doesn't make any sense at all, it's not only the numbers that are off, but basically the entire story about the weak, disappointing Z-1 and the more powerful, thirsty, short-range Z-2. Not to say it's like that in Goss' book, as I don't actually know that ... I'm just summarizing what is a bit of a recurring motif in the various Wikipedia articles and other online sources.
Regards,
Henning (HoHun)
Hi again,
I just noticed that Goss' book can be searched on Google Books:
The range figure is on p. 17 (not on p. 12, as stated in the Wikipedia).
Goss states no source, and doesn't seem to use footnotes either.
Further, the values he states (for the Do 17Z-2) are plain weird:
Max range:
- fully loaded: 330 km
- half bomb load, with auxiliary fuel tank: 1160 km
- empty, with auxiliary fuel tank: 3000 km
If one were to take that literally, that would mean that leaving out 500 kg of bombs (which are carried in the bomb bay, causing no parasitic drag) would almost triple the range of an 8-ton-aircraft.
Clearly, that has to be wrong.
Likewise, reducing the amount of fuel carried by 35% (by leaving out the auxiliary tank) and not dropping 500 kg of bombs after half of the flight is supposed to reduce the range to 28%.
Clearly, that has to be wrong, too.
In somewhat-of-a-weak-defense of Chris Goss, it might be that the terms "range" and "radius" got considered as synonyms somewhere along the line, like it's actually evident in the current version of the Wikipedia, too:
Clearly, to turn a 1570 km range into a 740 km whatever, you have to switch to radius.
Under specifications, the Wikipedia actually says about the Do 17Z-2:
But in the main text, it still says:
With the footnote referring to Goss p. 12, where no range is stated at all.
That's an example why I personally sometimes refuse even to talk about information someone pulls from Wikipedia ... not worth my time dealing with this kind of carelessly dumped bits of mostly unattributed or even falsely attributed information.
Regards,
Henning (HoHun)
I just noticed that Goss' book can be searched on Google Books:
Dornier 17 in Focus
Fotografisk bog om det tyske fly Dornier 17 og variationer heraf samt operationer med flyet på de forskellige fronter under den 2. verdenskrig.
www.google.de
The range figure is on p. 17 (not on p. 12, as stated in the Wikipedia).
Goss states no source, and doesn't seem to use footnotes either.
Further, the values he states (for the Do 17Z-2) are plain weird:
Max range:
- fully loaded: 330 km
- half bomb load, with auxiliary fuel tank: 1160 km
- empty, with auxiliary fuel tank: 3000 km
If one were to take that literally, that would mean that leaving out 500 kg of bombs (which are carried in the bomb bay, causing no parasitic drag) would almost triple the range of an 8-ton-aircraft.
Clearly, that has to be wrong.
Likewise, reducing the amount of fuel carried by 35% (by leaving out the auxiliary tank) and not dropping 500 kg of bombs after half of the flight is supposed to reduce the range to 28%.
Clearly, that has to be wrong, too.
In somewhat-of-a-weak-defense of Chris Goss, it might be that the terms "range" and "radius" got considered as synonyms somewhere along the line, like it's actually evident in the current version of the Wikipedia, too:
Clearly, to turn a 1570 km range into a 740 km whatever, you have to switch to radius.
Under specifications, the Wikipedia actually says about the Do 17Z-2:
But in the main text, it still says:
With the footnote referring to Goss p. 12, where no range is stated at all.
That's an example why I personally sometimes refuse even to talk about information someone pulls from Wikipedia ... not worth my time dealing with this kind of carelessly dumped bits of mostly unattributed or even falsely attributed information.
Regards,
Henning (HoHun)
