Project Martin A-30 Baltimore

my apologies for the poor choice of words.
i used "thoroughbred" only as the opposite of workhorse.
there was no comment about performance implied.
more that thoroughbreds get the press
and workhorses get the job done.
for example, the B-17 and B-25,
both excellent aircraft,
got most of the press coverage.
where as, the B-26, A-20 and A-187
are rarely mentioned...almost to the point
that one would hardly know they existed.
yes, that's an exaggeration, but,
i think you get my point.

i still find it amusing to watch a show
on the history or military channel
and hear the narrator speak
of one of the more glamorous aircraft,
only to see a group of A-20s or some such.

in the end,
we are fed stories about thoroughbreds
and little or nothing about workhorses.
why?
thoroughbreds are exciting.
workhorses, not so much
and there is a limited
amount of space
to write the story.

so much for the horse analogy.

oh wait...one more...
i think we've finished
beating a dead horse.
 
Hello Smilo,

Sorry if this looks like I am trying to revive the dead horse....
I have always had issues with analogies where the characteristics really don't match well or seem somewhat meaningless.
Perhaps that is why I had only fair grades in English classes even though my technical English is quite good.

Analogy of Thoroughbreds, Race Horses, Plow Horses, Cavalry Horses and the like is interesting but as I see it is pretty much a compliment that has no real meaning as far as technology goes. Genetics and heredity is how I interpret the terms and the only thing that I see that can carry on from one design to another is the design staff and that is no guarantee.

If you think about it, a True Thorougbred would havd been the Grumman Wildcat and Hellcat. Both were successful designs and both evolved from the ideas of a naval aviator and his company. Both came from long lines of similar designs....

We all like to think that past performance is an indicator of future results, but there are as many cases where that was not true and ones in which it was.

Another strange comment in my opinion is an analogy between the A6M Type Zero being a proper high class lady while the N1K2-J was a horny downtown girl. The image is vivid, but I am still at a loss as far as being able to put some kind of meaning to this in the context of aeroplanes. How do the characteristics translate between the two???

- Ivan.
 
the real question is,
should i keep this to myself?
apparently, not....

well, so much for trying
to gracefully back away
from a semantics debate
that i'm not interested in.
what more can i say?

flog away...if you must.

what i am interested in
is the forward progress
of the baltimore project.

i will now withdraw
back into my lair
and observe the show.
 
High class ladies and horny downtown girls

Hello Ivan, Hello Smilo,

Yes, we still haven´t killed the horse...

It´s funny, the human trait of insisting on assigning human attributes to things. Perhaps it comes from the English habit of calling ships "she" instead of "it", which then extended to aircraft and then even cars.

In my opinion it´s OK calling a pet a "he" or a "she", and adding human behaviour descriptions when talking about it in the park with other people and their pets, after all they are part of the family.

However, comments about a ship or a boat like "she rides the waves like...", or about one´s car such as "she´s ticking over nicely" sound rather affected. Is a captain married to his ship? Does a car substitute a woman? It sounds a bit wierd, to say the least, I´d say. But then, it´s so widespread, that talking like this is normal and everybody accepts it.

How is a high-class lady fighter going to behave differently from a downtown horny girl fighter? And worse, what do horny downtown girls or high-class girls have in common with certain fighter planes? I remember reading a comment about the Curtiss AT-9 beind compared to Jane Mansfield.

Then, even worse is the other way round, where the downtown horny girl would be described as "she goes like a sh**house door in a gale", or like being a dog, especially if she´s not too beautiful. What´s a dog supposed to think about this?

Popular expressions often completely lack in taste, I suppose, and some people have no remedy, but the origin of such expresions is of course, anonymous.

Anyway, at least, calling a plane a thoughrobred or a workhorse, are both compliments! ...and it won´t offend the horses.

Cheers,
Aleatorylamp
 
Baltimore spec + performance details

Hello Smilo,

As usual there is possibly incomplete or conflicting or contradictory information, in this case referring to the performance of the Baltimore. One thing is clear, that the first editions Mk1 to 4 had 1600 hp engines, whereas the 5th one had 1700 hp ones. Then, they got heavier with each edition, so the performance also changed.

For the Mk5 I have several different pieces of data which you may be able to clarify:

Engine:
a) Wright R-2600-29, some say R-2600-13,
1700 hp at takeoff, 1450 hp at 12000 ft (the latter also at max. power?)
b) Wright Cyclone GR-2600-A5B, 1660 hp, (geared), but most probably this was only Mk1 to Mk4.

Fuel tankage:
a) 407 USG
b) 490-1449 gal. (English gallons?) ...(some models had extra tanks?)

Top speed:
a) 305 mph at 11600 ft
b) 308 mph at 11500 ft
c) 320 mph at 15000 ft

Perhaps you have more reliable information at hand?
Thanks in advance for your efforts!
Cheers,
Aleatorylamp
 
Baltimore supercharger

Hello Ivan,

The massive P47 engine seems to have the best propellers to fit the impressive 2x1700 14-cyl supercharged engines (1700 hp at 2600 rpm) of the Baltimore. Ceiling appears to have been quite a considerable 25000 ft.

Putting in the cylinder capacity and compression ratio parameters, and adjusting the torque and friction tables, I get quite a close and possibly quite satisfactory 1720 hp at 2585 rpm.

The engines had a 2 stage supercharger, which for CFS1 will unfortunately have to be single stage, probably with only with approximations to fit performance at different altitudes.

I was looking for your thread on engine tuning, but haven´t had any luck yet.

As I have few details on the engine itself, I have to juggle around the P47 parameters relative to Boost Gain and Manifold Pressure a little. For the moment I have slightly reduced the P47 ones, but I feel like groping in the dark a bit.

I´m getting too much power at altitude, but reducing manifold pressure to adjust it, low altitude power drops considerably (of course...).

Without putting you out too much, perhaps you could recommend something, or maybe simply point me towards your engine-tuning thread?

Thanks a lot!
Cheers,
Aleatorylamp
 
at this point, this is the only document i have.
can you read or translate (i believe) Polish?
according to this document,
the MkV had 2xR-2600-29's
and farther down, notice
fuel...490 US gal=407.7 Imp. gal. at 2940.0 lb
oil...27.5 US gal=22.9 Imp. gal at 206.3 lb
 

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Hello Smilo,

Thanks for your information - it definitely clarifies the type of engine and tank capacity!

As regards the attached document, I´m afraid the resolution is too low for it to be legible.
My only remaining doubt at the moment would be the top speed.

If you can make out the info regarding speeds, maybe it´s easier if you just tell me instead of trying to send a picture in higher resolution of the document.

If all fails, I´ll just take the present info as Max. speed 320 mph at 15000 ft and 308 mph at sea-level, unless of course, being a supercharged engine, the speed could be the same at any altitude... Hmmm...

Thanks!
Cheers,
Aleatorylamp
 
i can barely read it either
and i'm looking at a 48 inch screen.

i was able to google some of the words
and got a few,

predkosc=speed
maks.=max.
wysokość= altitude
therefore, max speed altitude[mph/ft]=320mph/15,000ft

przelotowa=looped or cruising
therefore,
predkosc przelotowa [mph] might mean
cruising speed[mph]=224mph

pulop(?) i can't get a translation
praktyczny=practical
ft=25,000

zasieg normalny [mile/lb]=980/2000
zasieg=effect_range
normalny=normalmight, therefore be,
normal effective range
of 980 miles with a 2000 pound load.

these values are all in the MkV column.

that's about all i'm able to come up with.


ps...i do see that 308***/13000
in the MkI and MkII columns
unfortunately,
i am unable to read the footnote.
but, i can see 284mph/ 457, 1 km/ft
 
Hello Smilo!

That´s excellent! Thanks very much indeed. There´s no doubt anymore and I can proceed with this data.Pulop should mean ceiling then.

I found an interesting page mentioning some performance data. As I know you like the plane, and for the event that you haven´t seen this info, here it is:

QUOTE
With bomb-bay auxiliary fuel tanks (as used during ferry deliveries from USA via the Equatorial Atlantic route), a range of 5-1/2 hours was possible. By fitting a 700 gallon tank in the bomb-bay
we cold range out as far as the Dardanelles and into Northern Greece on recon.

The Baltimore was an aeroplane all pilots feared before they started flying them, mainly because noinstruction was available. You were given a dossier on the aircraft and when you thought you knewenough about it you took off.

Landing a Baltimore required a special technique and we all had trouble with the landings until we developed this technique. A flying boat skipper could have landed a Baltimore easily; the technique was the same:Come in low with power, then at one or two feet ease on more power until the wheels touched, then ease off power. Once on the ground it was imperative you kept absolute control because she was a vixen for group-looping.

Take-off in a war machine like a Baltimore or a Spitfire is an exhilarating experience. The acceleration is so great you feel you are being punched along. The stalling speed was 118 miles per hour so you had to be doing more than that before take-off.

The single engine control speed - that is, the speed if one engine cuts so you can still maintain control of the aeroplane - was 165 miles per hour. so there was a 47 miles per hour gap to make up before you could consider the flight under control. This period lasted a few seconds only due to the high rate of acceleration.

The undercarriage which always is a drag when suspended, would retract in a Baltimore in three seconds, and by the time the undercarriage locked in the "up" position the speed was only a second or two away from 165 miles per hour. Once it raced past that speed it was a glorious aeroplane to control.
UNQUOTE

It must have been quite an experience to fly the Baltimore!
Cheers,
Aleatorylamp
 
that was interesting, thank you.
speaking of the ferry tank,
here's a fron and side view;
 

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Hi Smilo,

Good, thanks. I had no idea it looked like this!

At the moment I´m tuning the engine to try and get the speeds right at low and high altitude. For the time being, I can only get one or the other to coincide.

I´ve finally found Ivan´s Engine Performance Tuning Tutorial again, and I´ve copied it all out to study it thoroughly. Upto now I could only get the gist of it, but now I´ll delve deeper.
With all that´s in there I should get the Baltimore´s performance bang on!!

Cheers,
Aleatorylamp
 
Oops!

Hello Aleatorylamp, Smilo,

I have been occupied with other things and had not been following this thread for a while.
The PC still crashes at strange times, but at the moment it is a matter of reviewing the P-40 AIR files and much of that can be done on other machines.

There seem to have been a great number of developments.

I am glad you found the Engine Performance Tuning thread. Too bad it is not a sticky.
You commented earlier that you could not find data for the Wright R-2600 engine.
I have actually found that most of the really essential data can be found on Wikipedia among other places.
The only thing missing from Wikipedia is the Manifold Pressure settings.

One way to cheat a little is to just use the numbers I have in my AIR file for the B-25C Mitchell.
It has basically the same engine though altitude ratings may be a bit different they are still going to be very close.
I do not recommend using the entire AIR file because I made a lot of changes to tune for the Anhedral on the Mitchell's wings.
One way to confirm data is to find the manual for another aeroplane that uses a similar model engine or perhaps you can find the SEFC as a separate posting somewhere.
I would need to do some poking around to see what model of engine and whether I have data.
I am pretty sure I actually have lots of data on the Baltimore.

Regarding Propeller tables, it might be worthwhile to calculate the Propeller Power Coefficients for each of the stock aircraft and find out which one is actually closest to the Baltimore. Just eyeballing the sizes and such doesn't work all that well because of the Reduction Gear Ratios. Also, operating speed ranges are important.

I actually have a much better and readable copy of the Table of data that Smilo posted.
Let me know if you need it.
The 284 MPH listing as a footnote is a Sea Level Speed if my phonetic Polish to Russian translation is accurate.
Even though the listing is for the earlier Marks, the value should be pretty good for all the versions IMO because 100 HP is not going to make a significant difference. Also, later aeroplanes tend to have more power but also tend to have more drag from equipment additions.

1700 HP at Take-Off is probably the equivalent of a WEP rating.
Be very careful about assuming that the 1450 HP at altitude is actually a maximum rating.
The changes are that it is not a maximum.
It is more likely to be a Military rating.

Regarding Engine Versions:
My guess is this:
This aeroplane was originally used as an export model to the French and British.
The US military was fairly uptight about sending out their latest and greatest engine (especially supercharger) designs.
The Curtiss-Wright typically used a designation of GR for reduction geared radial engines and a simple R for direct drive.
This can be seen in the Brewster export versions of the Buffalo which had both versions.
The GR-1820 designation was probably a commercial designation of an export cleared engine and other than the supercharger and minor details that we don't care about in CFS, dimensionally the same as the US Military R-1820.

Hope this helps.
Email me if you don't have a version of the B-25 Mitchell to check out.

- Ivan.
 
Ivan´s Engine Tuning Tutorial in one document.

Hello Smilo,
I actually thought it would be of interest to put all of Ivan´s Engine Turtorial posts into one document to make it more readable. I managed to put it all together, inverting the order of the posts to get the beginning at the top, also sifting out the off-topic material. Finally I made one .rtf format type document out of it - this way it keeps headings in bold type. Here it is, attached!

However, there were no longer any attachments contained in the thread, so there´s just the information in the posts themselves.
As regards the Table of Data: I´m afraid that´s not there either. ...however, maybe I don´t understand exactly what you mean...

Hello Ivan,
Thank you for your interesting (as always!) post on the Baltimore´s engines. They had a single 2-speed supercharger with a volume compression of 7 to 1 and 10 to 1. Early versions had geared props, but the Mk.V didn´t so there´s no problem as to the reduction ratio.
Thanks for the comments on altitude and power for these engines. So for maximum take-off power probably 1660 hp would be better, keeping 1700 hp for WEP.
The clarification on the sea-level setting being 284 mph is fantastic because it now coincides far better!
Conclusions from your comments:
1) Maximum speed of 320 mph at 15000 ft would then be without WEP.
2) One source quotes 329 mph at 15000 ft here, so perhaps this was achieved with WEP.
3) Possibly the widely quoted 305 or 308 mph max. speed refers to the sea-level performance under WEP.

Cheers,
Aleatorylamp
 
Last edited:
"I actually have a much better and readable copy
of the Table of data that Smilo posted.
Let me know if you need it."

is a quote from Ivan's #33 post above.
i was merely encouraging him to post
his "better and readable copy".
 
Hi Smilo,

I will need to coordinate with Anna Honey to pull the image out of a rather large PDF.
She has a full version of Adobe Acrobat on her machine.
I do not have a PDF editor / extractor and getting something useful out of a PDF is always a chore.

Hi Aleatorylamp,

I believe you are misinterpreting my meaning about the GR-2600 as versus the R-2600.
Wright called their engines R for direct drive and GR for reduction geared.
The US Military did not make any such distinction. ALL of their models were R-something.

The point I was trying to make was that the early GR designation on the early Marks was because it was not a US military version of the engine, thus it used the Curtiss Wright commercial designation.
The Mk.V used a R-2600-13 or R-2600-29 which was the US Military designation of basically the same engine though with a slightly higher rating.

While the R-1820 was used as both a geared and direct drive engine in the Buffalo, the R-2600 was a much bigger engine and probably was never used as a direct drive engine.
The R-1820 in the early versions had a very low maximum RPM (about 2200) so a direct drive with a small propeller on a rather slow fighter would not be too far out of range.

I did a bit of poking around last night in my downloaded manuals and found this:
The R-2600-13 was used in the B-25C/D models. (The version I built.)
The R-2600-13 OR R-2600-29 was used in the B-25J.
The Pilots Manual makes no distinction between the two engine models in operation.
The power output is identical between the two versions.

Here is a link to a copy of the SEFC that I found. It is for the B-25C/D, but as stated earlier, there is no difference from our point of view.
http://zenoswarbirdvideos.com/Images/B-25/B25SEFC.pdf

Gotta Run. Need to go do some grocery shopping.
Email me if you still need the B-25C AIR file.

- Ivan.
 
Hello Smilo,
OK, I understand!

Hello Ivan,
Thanks for the B25 engine specs. Very detailEd and useful!
I thought I saw your B.25 in the warbirds library, in order to get at the .air file, but I was mistaken. It would indeed be useful, so I´ll e-mail you to have a look inside! Thanks for the offer!

The reason for my thinking that only earlier versions of the Baltimore had geared engines was in the different spec sheets where I found the following mentions:

- Powerplant: 2 × 1700 hp Wright GR-2600-A5B geared radial engines.
- Engine: 2 x Wright-Cyclone R-2600-19 (1660 hp) (Mk.V: R-2600-29 1700 hp)

...but then a 3rd mention says:
MkI to MkIII: 2x 1660 hp Wright Cyclone GR-2660 A5B
MkIIIA and MkIV: 2x1660 hp Wright Cyclone R-2600-19
MkV: 2x1700 hp Wright Cyclone R-2600-13 or 29

The fist mention does not mention the model the geared engine was used on, and the second one probably omits it altogether, but the third mention does clearly state the geared version for the earlier ones. Also I see the number on the two mentions of the geared engines are different! Maybe unreliable?
Then, wouldn´t the B25 engine spec sheet state the fact that it was a geared engine if it was in effect geared? But as you said, perhaps the American specs did not make any distinction.
Anyway, geared or not geared, I suppose it wouldn´t make much difference in the .air file.

Thanks a lot again!
Cheers,
Aleatorylamp
 
Hello Aleatorylamp.

Check your email.

The reason I do not believe the Mitchell's AIR file is useful to modify into one for the Baltimore is because although the weights and performance and engine may be the same, I did a lot of odd tuning for the Mitchell.
The Anhedral of the outer wing panels resulted in a strange yaw to roll coupling that I was trying to duplicate.
There were a LOT of changes to get there and I believe you would do better to start fresh.

As for geared versus direct drive, there should be a serious difference in performance in real life.
Although it may not be shown in CFS, the large propeller and a high RPM direct drive means the blade tips will be supersonic and very very poor efficiency.

I still have not had a chance to borrow Anna Honey's computer for Adobe Acrobat yet.

- Ivan.
 
Hello Ivan,
Thanks for the Mitchell B25-C .air files. They are proving very useful.

I did not mean to use the whole .air file. Actually, only the engine manifold pressure and boost gain parameters, the torque and the friction tables, and the propeller efficiency and thrust coefficient tables.
The propellers on the Baltimore were smaller: 11 ft. The Mitchell´s were 12.58 ft, so perhaps they were not geared on the Baltimore?.

At any rate I´ve done some quick preliminary testing, trying them out as geared, and the performance seems to be fitting nicely within more correct speed ranges. One thing is good, I´m not getting the huge Hp increase any longer from 1700 Hp at sea-level to 1985 Hp at 15000 ft. Now it´s between 1660 and 1680 hp.

Tomorrow I´ll have some more exact results.
Good night!
Cheers,
Aleatorylamp
 
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