Model 133 'SMUT' (ATTT or AT3)
(Special-Mission Utility Transport)
Technology Tactical Transport)
Status: sub-scale tactical transport demonstrator
Powerplant: 2 x Pratt and Whitney Canada PT6A-135A
First flight: December 29, 1987
Known at Scaled Composites by its inhouse monicker "SMUT" (which
conveniently stands for Special-Mission
Utility Transport) the Model 133 Advanced Technology Tactical Transport
(ATTT) proof-of-concept demonstrator is a 62% scaled version of an airplane
designed to challenging
STOL and long range requirements. The ATTT was developed and test flown by
Scaled Composites, Inc. under contract to DARPA. Burt Rutan adopted a no-nonsense attitude in development contract negotiations with DARPA on the AT3 and managed to avoid much DoD red tape in consequence. Payments were to be linked to distinct milestones.
The initial flight test program
consisted of 51 flights with the original cruciform tail configuration (Model
133-3), measuring and refining performance,
stability and control, and handling qualities. The results of the fabrication
and test program were presented in a comprehensive report to DARPA.
In an effort to improve the aft loading capability of the aircraft and to
correct aerodynamic deficiencies discovered during the test program, the ATTT
aircraft was modified with a twin-boom tail whose general configuration was
similar to that of the Rockwell OV-10 Bronco (Model 133-4.62). This modified
configuration is shown in the accompanying photograph. Pratt and Whitney of
turboprop engines were attached to the twin booms in a tractor configuration.
A simple fully mechanical flight control system was installed, with full control
available from both seats. The Scaled-designed landing gear is actuated using
The Model 133 demonstrator used a unique flap system to enable its STOL performance.
The high lift configuration consists of eight Fowler-type flaps, each of 43%
chord. The flap system was designed to allow the initial takeoff roll to be
performed with the flaps extended, but at low deflections to minimize takeoff
drag. As rotation speed was neared, the flaps were quickly rotated to the maximum
lift position via a separate pilot action. The ATTT was a key program for Scaled.
It demonstrated our ability to perform a challenging aerodynamic and structural
design, and to build, test, and deliver what amounted to two different manned
research airplanes, including all design and flight test data, to DARPA for
less than 3 million dollars, including all recurring and nonrecurring costs.
The ATTT never received a popular name, although a source that once worked for Scaled once refered to it as another Grizzly. It is currently in storage at the Air Force Flight Test Center Museum,
at Edwards Air Force Base and is undergoing restoration for future display.
Population: 1 [N133SC]
- Scaled Composites official website