The ratings of 4 Aerospace & Defense stocks are down this week, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, National Presto Industries, Inc.’s (NPK) rating worsens to a D from the company’s C rating a week ago. National Presto Industries, Inc. is a diversified manufacturing company. The company also gets F’s in sales growth. For more information, get Portfolio Grader’s complete analysis of NPK stock.

Rockwell Collins, Inc. (COL) is having a tough week. The company’s rating falls from a C to a D. Rockwell Collins, Inc. designs, produces, and supports communications and aviation electronics for commercial and military customers worldwide. For more information, get Portfolio Grader’s complete analysis of COL stock.

Esterline Technologies Corporation (ESL) gets weaker ratings this week as last week’s C drops to a D. Esterline Technologies Corporation is a worldwide supplier to the aerospace and defense industry. For more information, get Portfolio Grader’s complete analysis of ESL stock.

Slipping from a C to a D rating, Sparton Corporation (SPA) takes a hit this week. Sparton Corporation provides electronic manufacturing services, including design and/or manufacture of a variety of electronic and electromechanical products and assemblies. The company also gets F’s in operating margin growth, earnings growth, earnings revisions, earnings surprise, earnings momentum, and free cash flow. For more information, get Portfolio Grader’s complete analysis of SPA stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.