Boeing NB

The Boeing NB, also known as the Model 21, was a primary training biplane that Boeing developed for the United States Navy in 1923. It was a two-bay, equal-span biplane of conventional layout with interchangeable wheeled and float undercarriage, and the pilot and instructor sat in tandem open cockpits. The Navy's first prototype had proved too easy to fly and impossible to spin, so the NB-1 design added some instability; that made a spin possible but recovery from one nearly impossible, and a series of modifications was tried to reach a compromise. Production came in two batches, the first with Lawrance J-1 radial engines and the second with war-surplus V-8 engines from Navy stock, and Peruvian Naval Aviation also operated the NB-1.