- How is the Cherry® Rivetless Nutplate (RNP) installed?
- A drill-quality hole is machined in 2024 aluminum and the RNP is placed in the hole. The installation tool engages the RNP mandrel, locating a guide surface between the mandrel and the RNP retainer. This positions the RNP assembly square to the work surface. The installation tool is actuated and the mandrel is pulled through the retainer and work surface. The mandrel is discarded after installation.
- What specifications does the Cherry® RNP meet?
- Nut plate performance is described in NASM25027, which sets minimum standards for these products. Among the qualification requirements are testing for torque-out, push-out, locking torque, as well as discontinuities in the assembly components. In addition, Agusta has created A900A/NTA903A specifications for the RNP. Airbus has also written ABS1295 referring specifically to the RNP product line.
- How does the Cherry® RNP work?
- The mandrel pulls through the RNP retainer, applying both radial and axial forces to the work piece. These forces cause the lobes on the Â retainer shank to form into the work piece material, while avoiding formation of stress risers. This design resists the torque-out and push-out forces well in excess of the minimum values established in NASM25027. Additionally, the RNP is manufactured in several "float" capabilities. "Float" is the term used to describe the installed nut plateâ€™s capacity to align with the mating screw or bolt. Float ranges of .030", .060" and .120" are commonly available.
- What are the benefits of using the Cherry® RNP?
- Conventional nut plates require three drilled holes and in some cases, two counter sunk holes. When using a solid rivet, two mechanics are often needed to perform the bucking operation. All this adds up to increased labor costs, and for each drilled hole, the potential for scrap or rework. The RNP requires a single drill-quality hole, and Cherry installation tools for a labor-saving efficient operation.
- Who uses the Cherry® RNP?
- Cherry is proud to recognize the quick acceptance of this new product by Agusta, Pratt & Whitney, Rolls Royce, Airbus, Raytheon, and Lockheed Martin, among others.
- How is the nut element replaced?
- The conventional Cherry® RNP features a floating, replaceable nut element. The retainer clip is easily removed and the NAS1794 nut element replaced. The retainer clip is then re-installed. Lightweight versions of the RNP do not have this replacement capability - the RNP must be removed and replaced.
- How is the Cherry® RNP replaced when the hole is oversized?
- Testing has demonstrated that the Cherry® RNP may be replaced in an existing hole that meets the original diameter requirements*.
If the hole exceeds the original diameter range, the replacement recommendation is to use a Cherry® RNP with a larger float, which corresponds
to a larger original hole diameter range, or to use the Cherry® RNP oversized retainer option. These will provide replacement capability for
holes up to .020" larger than the original maximum hole diameter.
*Cherry Aerospace recommends that an application-specific evaluation of this option be made, as every application is different and may or may not yield the intended results.
- What is the minimum material thickness that the Cherry® RNP can be installed in?Â
- The Cherry® RNP retainer is designed to engage in material thickness that will support its installed shank depth. This dimension is called the minimum grip and is specified on each Cherry® RNP standards page. To insure conformance to NASM25027, always install this product in its intended material grip range.
- What is the maximum material thickness that a Cherry® RNP can be installed in?
- While the Cherry® RNP design theoretically does not have a maximum material limit due to its proprietary shank design, there is a limit to the engagement area of the mandrel in relation to the installation tool jaw system. Material thickness that reduces the jaw engagement on the mandrel to less than full contact is considered to be above the maximum grip capacity and is not recommended. Short mandrel versions of this product will have reduced maximum material thickness limits.
- Why are Cherry® tools needed to install this product?
- The Cherry® RNP requires the use of dedicated design installation tool pulling heads to obtain the performance levels established in NASM25027. These pulling heads provide the controlled dynamics necessary for the radial expansion of the retainer shank. Only Cherry® tools specified in the standards pages are recommended for this purpose. Use the G704B power riveter or G750A hand hydraulic riveter for up to and including .2500-28 RNP products. Larger sizes require the use of G84 or G84-LS power riveters. See the RNP Standard Pages for specific information on the required tool systems.
- What information is needed to order a Cherry® RNP?
- The basic information required is the nut size/thread pitch, float capability, material thickness, counterbore requirement, nut material, and finish/lubrication preference. Cherry® personnel, both in the field and at the factory are ready to help explain the options.
- Can the RNP be installed in Titanium, Composites, or hard alloys?
- The Cherry® RNP was originally designed for aluminum structures, taking advantage of the interaction of its patented lobe design and its effect on 2024 aluminum. Subsequently, a version was developed to support composite structures. Increased interest in its use in other materials has highlighted the need to support these challenges, and our product development engineers are currently working on them. At this time, however, we recommend that the RNP be installed in composite structures and 2024 aluminum alloy only.
- What is the recommended removal process?
- Each Cherry® RNP has a tool designed to carefully remove the installed product. The tool is referenced along with the installation tool in the RNP Process Manual. We recommend the use of these removal systems to prevent damage to the work piece and to eliminate hole distortion.
- Where can I get more information on this product?
- Cherry® Aerospace supports its customers with regional representatives who are highly trained in the technical capabilities of our products, along with factory technical services personnel. Product Information may be found on our website, or by telephone at +1 (714) 850-6022.