From
https://www.flightglobal.com/pdfarch...0-%201766.html
Inspired design led to the unique Lightning staggered-engine configuration—both engines being installed on the aircraft centre line, viewed from above, but with the upper engine to the rear of the lower engine, thereby giving an effective powerplant frontal area only 1.5 times that of a single powerplant. This configuration not only minimises drag but also eliminates asymmetric engine-cut effects and allows the possibility of low-altitude cruising on one engine, as well as providing the only chance of getting home to base after an engine failure. It also simplifies the duplication of essential services, allowing increased reliability.