Technote: P-51 and P-39 Standards

During the development cycle of any aircraft the manufacturing standards tend to evolve and commonly change content, description and name. Keeping track of those changes is key to ensuring the defined parts are correct for the assembly of components.

Alongside the P-39 Restoration project, I still develop several aircraft components for other aircraft. This includes my old favourite, the P-51 Mustang. This example refers to the Quadrant Assembly for Engine Control; drawing #102-43005 for the early P-51B.

Many of the standard parts called up on this assembly use the early standard references. These are typically prefixed with “B”, like B1009, B1135, etc. These standards were later updated, and a new series of standards replaced them. I have correlated these in a spreadsheet, as shown below.

The spreadsheet only lists the standards that are available in the blueprint archive and may not be a complete record. For a more comprehensive listing, refer to the Erection and Maintenance instructions for the P-51A series (T.O. No. 01-60JC-2). Check the Conversion lists from pages 404 onward.

The CAD development of the Quadrant Engine Control is still a work in progress…created to the exact original dimensions.

My plan for the P-51 is to further develop the instrumentation for the early and later versions.

P-39 Update and Standards:

Over the last few months, the P-39N Restoration project has been my primary focus. We are close to completing the CAD work for the Cockpit instrumentation.

By contrast to the P-51 Mustang, we don’t have the same collection of Bell Standard part blueprints. We only have what is available within the manuals. However, the notations for the parts are similar for the industry as a whole. For example, a Spacer Part noted as Q065-6-20 shares the same notation for the dash numbers as the P-51 (standards 4s3 and 4S4). This in turn will define the spacer size…the first dash number sequence indicates the bolt size and the second is the length. In this case, it would be #6 bolt size. The length is defined in 1/32nd inch, making it 20/32″ (5/8″) long. This table derived from the iPart feature explains the designations in more detail.

The next time you come across a part reference you are unsure about, cross-reference it with other aircraft-known standards. Also, consult the comprehensive collection of AN and MS standards on Everyspec.com.