The Fake Difference in the Length

In addition to the side view of the SBD-5 presented in one of my previous posts, I have prepared side views of the earlier Dauntless versions: SBD-2 and SBD-3 (Figure 5-1):

Figure 5-1 Differences between the SBD-2 and SBD-3
Figure 5-1 Differences between the SBD-2 and SBD-3

(Here are the links to the high-resolution profile images of: SBD-2, SBD-3).

When you look into Dauntless specifications, you will find that all its models have the same span, but they often differ from each other in the length. This is a typical case, because the wing geometry determines the aircraft behavior. Thus, once “debugged” in the prototype (the stall characteristics etc.) it remains unaltered between subsequent versions. The fuselage shape is not so important, so it is often modified. In the effect, the length of the airplane often vary between subsequent versions.

In the previous post I described how the photos confirmed the different length of the SBD-5 (33’ 1/8”) and the SBD-3 (32’ 8”), listed in their specifications. The reason was the different engine mount, modified in the SBD-5. The same sources specify the length of the SBD-2 as 32’ 2”. This is something strange, because I cannot find any evidence of this significant, 6 inch difference between SBD-3 and SBD-2 on the photos!

The SBD-3 was a “quick and dirty” adaptation of the SBD-2 to the recognized requirements of the modern war. Douglas added armor plates to the pilot and gunner seats, self-sealing fuel tanks (reducing their capacity), doubled the rear guns. All the key elements of the design: the airframe and the engine, remained the same. Where is there the modification that changed the overall of length of the SBD-3 by 6”!?

I started to look for the sources of this information (the subsequent publications copy their specification data from the earlier ones, up to an ultimate source document). Ultimately it seems that it comes from the BuAer Performance Data Reports. There are two of such documents, created in 1942: one for the SBD-2 and one for the SBD-3. On their last pages you can find the measured airplane dimensions. The difference is there: LENGTH, LEVEL: 32’-8” in the SBD-3 report, and LENGTH, LEVEL: 32’-2” in the SBD-2 report. (Unfortunately, they did not specified the length on wheels for the SBD-2, so there is no double-check). Note that all other dimensions are the same. I speculated that the reason of these differences lies in the propeller spinner: it was often removed. If the tested SBD-3 had this spinner, and the SBD-2 didn’t — what was the eventual difference? I tried to check this option, but it shortens the fuselage length by less than 4”.

What’s more interesting: the only survived SBD-2 is owned by the National Navy Aviation Museum in Pensacola. On their web page the owner specifies the length of this airplane as 32’ 8” — the same as the SBD-3! Thinking further about it, I noticed the manual corrections of typing errors in other SBD performance data reports. So I have following hypothesis:

  • The SBD-2 and SBD-3 had the same length: 32’ 8”, as specified by the owner of the restored SBD-2 (NAM in Pensacola);
  • The typist of the BuAer Performance Data Report made a mistake (most probably —deciphering the handwritten measure results he/she read “2” instead “8”). The authors of the first publications about SBD Dauntless used this source, and the others used their publications. So the initial error was multiplied;

Thus I assumed that the SBD-2 length specified in Performance Data report is wrong. Basically it was the same as the SBD-3. It also applies to the SBD-1:

Figure 5-2 Side view of the SBD-1
Figure 5-2 Side view of the SBD-1

(Here is the link to high resolution profile image of the SBD-1). The only external difference between the SBD-1 and SBD-2 is the larger air scoop on the top of the engine cowling.

Conclusion from this little investigation (in fact, it took me a few days): do not trust blindly the specified width and wing span of a historical airplane! When you compare the different sources you will find that sometimes these figures are different. Always try to verify available data. The wing span is less error-prone because it usually does not vary between subsequent versions. Remember that the photos are always the ultimate evidence.

In the next post I will present the updated/verified Dauntless top view.

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