Details
This 22ND8-02 - Nut - Spline is in NS condition and has a nylon insert. AirCorps has and can provide manufacture certs if requested.
Spline nut part numbers can be a challenge to understand, here is a breakdown and some beneficial technical resources AirCorps can provide.
The actual thread for the 22ND8-02 spline nut is 10-32 or .1900-32UNJF-3B by current ESNA production & engineering specifications. In reference to 22ND8-02, the "8" is often mistaken for an 8-32 thread pitch, instead the shank length of the spline nut is what the "8" in the part number represents. We have provided a link below to the spline nut section of the ESNA catalog detailing the dimensions of the component. Fiber vs Nylon is a common question when procuring locking insert nutplates, nuts and spline nuts. While many original WWII era drawings call out 22D8-02 for example that early spline nut was produced with a fiber insert that has shown a propensity to crack due to age, ESNA added the "N" to the 22ND8-02 part number when the nut has a nylon insert. We recommend using nylon insert fasteners wherever possible.
22ND8-02 ON THE P-51 MUSTANG
There are 17 occurrences of this spline nut on the P-51D, and a total of 25 units per P-51D. Principally this product is most commonly known as the spline nut installed as a part of 73-22007 - FITTING ASSEM. - TRIM TAB HINGE. This assembly and the spline nut is the basis for the Mandatory Service Bulletin detailed below. There are a total of (15) 73-22007 trim tab hinges per P-51 with three units installed on each of the rudder, (2) aileron assemblies, and (2) elevator assemblies respectively.
Mandatory Service Bulletin P51-001 and Supplement 1 dated May 1, 2013 is issued by Cal Pacific Airmotive Inc. in cooperation with the National Transportation Safety Board (NTSB) as holder of Limited Type Certificate LTC-11-5 for the P-51B,C,D,K, F-51D and F-51K model aircraft. It is recommended that all P-51 & TF-51 model aircraft comply with this Service Bulletin, Including those with an experimental airworthiness certificate.
As referenced in the Cal-Pacific Supplement 1 (Page 9) there are some P-51 Maintenance manuals, and parts catalogs that incorrectly identify a screw with a #8-32 thread to be used with this spline nut. It is critical to use the correct NAS221 series 10-32 brazier head screws.
From P51-001 -Supplement 1.
- Refer to Parts Catalog AN 01-60JE-4 USAF Series F-51D, TF-51D and F-51K Aircraft dated March 10, 1945, revised May 15, 1953, page 20D figure 4B “Aileron Assembly” index no. 33 to install the correct part number structural screw NAS221 series (10-32 thread). This parts catalog is also reference for the P-51D thru P-51K aircraft. Length of screw may vary from those published in the North American Aviation & USAF maintenance and parts manuals if trim tab is original, rebuilt, phenolic or metal covered.
- When installing structural screws to secure the trim tab to the hinge fitting P/N 73-22007, make sure the screw shank does not bottom in the threads of the spline nut and at least one full thread extends through the locking nut insert.
