Photos Sbd 5 36175 B 22 Number 8 (rma Edit)
A close up view of the damage to the wing leading edge of SBD-5 Bu.36175 as it rises from Lake Michigan in September, 1994. The structure is crushed nearly flat against the main spar in the wing center section. Salvaging useable components from this area has been a challenge! (image via A&T Recovery)

Refurbish or Replace?

Pioneer Aero had to remove numerous small parts in order to separate the SBD's fuselage into its major subassemblies. While some members of the restoration team are focused on the larger assemblies, others have begun assessing the smaller items, refurbishing what is rebuildable and remanufacturing what is not.

There is an old adage in aircraft restoration which seems to prove true all too frequently: "If it ain't bent it's corroded, and if it ain't corroded, it's bent." Even so, it is often possible to save and refurbish damaged components, as the Pioneer team has demonstrated time and again on this project. The SBD's wing leading edges have proved a particular challenge, however, as the above image intimates...

. (photo Via Pioneer Aero Ltd.)
Removing what remained of the badly crumpled righthand wing leading edge from the center section, revealing the aircraft's main spar in the process. (photo Via Pioneer Aero Ltd.)

Crash Damage:

When our Dauntless ditched into Lake Michigan in January, 1944, the dive bomber's forward fuselage and wing leading edge took a pummeling as they struck the water. Indeed, the crash essentially crushed the wing's leading edge flat against the main spar in places. A couple of months ago, the restoration team carefully stripped back this structure on the wing's center section (see image above) as part of their preparations for separating the fuselage. More recently, they began disassembling this crumpled mass of metal to assess what remained, and began replicating the parts which proved beyond salvage.

Screenshot 2023 10 25 At 12.25.47 am Edited
An illustration describing the various assemblies which form the leading edge structure under the skin in the wing center section for the SBD and A-24.

Wing Leading Edge Structure:

The SBD's center section wing leading edge structure comprises many different subassemblies, as revealed in the image above from page 50 in the A-24 illustrated parts manual. The elements labeled #23 and #24 in the drawing are of particular interest in this update. These components are officially described as "Web Assembly - Center Section Wing Nose", with the left hand example having part number 5062769, while the right is 5062769-1. While these numbers may seem innocuous to many, Douglas Aircraft employed a useful logic in their parts numbering protocol, which is worth examining further.

Screenshot 2023 10 25 At 12.33.08 am Pano Edited
An original Douglas Aircraft Company manufacturing drawing for the leading edge web assembly (part number 5062769) in the SBD's wing center section. While it may seem complex, and hard to interpret, this drawing includes all of the details required to manufacture and assemble each of the individual parts involved (other than the fasteners). The Information Block in the lower right corner contains the "bill of materials" listing each of the parts required for the right and left-handed variants of this subassembly, along with the raw materials (with their dimensions) needed to manufacture them.

The Douglas Aircraft Company Part Numbering System:

To keep track of where everything goes, each of the many thousands of parts involved in the manufacture of an aircraft requires its own unique identifier - typically a number.

Different manufacturers each had their own methodology for part number assignment, but the Douglas Aircraft Company came up with a particularly effective one. While they too labeled each subassembly with a seemingly random number, Douglas reused this number as the basis for identifying the individual parts comprising that component, simply adding a hyphenated numerical suffix (e.g. "-23") to differentiate them from each other.

Furthermore, since aircraft are usually symmetrical, they have numerous, near-identical parts which are essentially mirror images of each other - oriented in either a right- or left-handed configuration. To simplify the process for the factory workers, parts with a righthand orientation had an odd-numbered suffix, while those on the left were even-numbered. This made it much easier for them to be certain they were working with the correct parts when fabricating a given subassembly.

Screenshot 2023 10 26 At 5.54.29 pm Pano
A closeup of the Information Block for the assembly drawing pictured earlier: Douglas Part Number 5062769 Web Assembly - Center Section Wing Nose.

Drawing Information Block - An Explanation:

The above image is a close up of the Information Block from the earlier drawing for Douglas part #5062769, the web assembly for the SBD center section’s wing leading edge. While this image is fuzzy, and perhaps a little confusing to those who aren’t used to reading manufacturing drawings, there are essentially four important areas of information depicted here.

  1. The block at the lower right delineates what the drawing describes, along with the names of the people who created and/or updated the drawing, as well as the dates of each release.
  2. The block at the lower left delineates the “change notices” in this version of the drawing, what they involved, who signed off on them, and when.
  3. In between these blocks at the bottom of the image, is another identifying the next assembly associated with the component this drawing describes, and the particular aircraft variant it involves.
  4. Perhaps the most important information, however, is featured in the “bill of materials” table at the top right. Reading from the left, the first two columns identify the part number suffix; odd numbers being for the right-handed components and the even for the left. The third column describes how many of that given part are needed. Adjacent to these three columns is information describing the material these parts are made from. This particular assembly primarily comprises parts made from either aluminum sheet stock or extruded aluminum. For the extruded parts, the bill of materials essentially identifies which extrusion profile to use, its length, material and temper state. However, for the parts made from sheet metal, there are a series of squares identifying the length and width of the material blank to start forming the part from, the thickness, alloy and tempered state of this material before manufacture commences, and then the material specifications the part must conform to following its completion.

Web Assembly - Center Section Wing Nose:

Douglas Part Number 5062769 essentially serves as a secondary spar, connecting ribs between the main spar and leading edge, while stiffening the structure over the wheel bays. As typical for its era, this component consists of a flat, sheet metal assembly (the web) with stiffeners (spar caps) running down its lateral extremities. Understandably, given how comprehensively the water impact crushed this area of the aircraft, very little of the original structure was salvageable, but what remained has served as a useful template (complemented by original factory drawings) for the remanufacture of replacement parts.

The following images describe some of the work underway to rebuild the web assembly. We have included closeup views of the earlier manufacturing drawing for Part Number 5062769, highlighting where each of these different components fit in the overall subassembly. Hopefully this provides a clearer idea of the work which the restoration team is undertaking, and how much effort is involved!

. (photo Via Pioneer Aero Ltd.)
The web section for the wing nose spar absorbed a lot of the crash impact, both crumpling and tearing in the process (as this image shows all-too-well). The lower part of this image shows the original right hand web assembly's primary sheet metal component (Part #5062769-3) along with its upper spar cap (Part #5062769-7), both heavily damaged. Using this original structure, complemented by the manufacturing drawing (seen earlier), Pioneer's engineers have begun remanufacturing a replacement, which is visible just above the damaged material. (photo Via Pioneer Aero Ltd.)
The assembly's newly remanufactured spar cap (Part #5062769-7) atop the sheet metal web section (Part #5062769-3). Note: the aluminum sheet which Pioneer works with arrives with a removable white plastic veneer to protect its surface finish during shipping. This layer also provides a useful surface for drawing the part outline and hole positions on it too, as is shown here. It will obviously be removed prior to installation, of course. (image via Pioneer Aero Ltd.)

Assembling the Web:

With parts for the secondary spar either refurbished or remanufactured, it was time to begin putting it all together.

The rebuilt web assemblies are almost complete in this image, just awaiting the final drilling and riveting together. (image via Pioneer Aero Ltd.)

Leading Edge Ribs:

The remanufacture of all the leading edge ribs for the wing center section is also underway now. Using Douglas Aircraft's ordinate table drawing, which tabulates the coordinates defining the outer profile for each rib, the team cut out an appropriately sized forming block to shape a sheet metal blank into a new rib. Once fully formed, the rib is ready for heat treating to significantly increase the material's tensile strength and hardness.

Screenshot 2023 11 14 At 10.59.09 am
The various 'cover assemblies,' or skin sections, associated with the forward wing center section. Pioneer Aero recently began remanufacturing the skin assemblies for the leading edges (part numbers 5090535-2 (left) and 5090535-3 (right)) which are identified as Callouts #01 and #02 respectively in this image.

Skin Assembly - Center Section Wing Nose:

Douglas Part Numbers 5090535-2 and 5090535-3 form the skins for the leading edge in the SBD's wing center section; Pioneer Aero has begun forming these key parts in recent days. Using the manufacturing drawing below (amongst others) the restoration team was able to create a jig-like cradle defining the cross-sectional profile for these skins. Using a combination of a rolling machine and an English Wheel, the engineers shaped a section of sheetmetal so that it conformed to the cutouts in the jig, a tool which they amusingly refer to as 'dinosaur bones', for obvious reasons. Once the team has completed and assembled the internal structure for the wing leading edge, they will rework and trim the skin section so that it lines up perfectly on top.

Wing Leading Edge Assembly 5090535
Wing Leading Edge Assembly 5090535