The Tale/Tail of the Platypus
- Eric
- 3 days ago
- 1 min read
The Have Blue aircraft had a unique design feature called the "Platypus", often shortened to "Platy". This was basically a thrust deflection ramp aft of the engines that helped to mask the engine turbines from view as well as providing a nose-up pitching force on the aircraft. The F-117 has a similar design, but on the Have Blue test aircraft, these surfaces were movable.
There was a concern that the aerodynamics of the unconventional design could lead to a loss of control if the angle-of-attack (AoA) exceeded 12 degrees. The platypus was designed to prevent the aircraft from exceeding this AoA by dropping automatically and therefore changing the thrust vector of the engine exhaust. It was a rudimentary thrust vector control system.
The Have Blue kit provides parts for both the up and down position of the Platypus deflectors. When in-flight the Platy most often was up, but when the aircraft was powered down, the Platy often appears sagged in the down position, likely due to loss of hydraulic pressure. You can choose to make the model in either configuration.
