The streamlined S.4 used a Napier Lion and recorded 239 mph before travelling to the United States, close to the speed of the victorious Italian Macchi. It later developed wing flutter during a practice flight, a dangerous positive-feedback instability that designers of the period could not yet predict completely. The estimated flutter speed is an engineering calculation rather than a measured result. At roughly 250 mph, it would place the aircraft about 11 mph above its recorded trial speed while Supermarine pursued a Schneider Trophy advantage.
Chapter · 13:53-17:29
The S.4's wing flutter exposed the risks of racing speed
Follow the S.4 from a 239 mph record to the wing flutter that ended its Schneider Trophy challenge during high-speed practice.