SCALED COMPOSITES MODEL 133 "SMUT" (ATTT)
The sub-scale demonstrator for the Air Force's future tactical transport had in fact little to do with it...

Two views of the "SMUT" in its original single-tail configuration.

The tail of the prototype was first fitted with small additional fins but even that wasn't enough and so it was replaced with a twin-boom tail. The original tail unit became Burt Rutan's personal mailbox for the time he lived in Mojave.

The clean and pleasant design of the Model 133-B demonstrator was particularly apparent when in flight.

 

Customer:DARPA
Main contractor:   Scaled Composites, briefly as part of Beechcraft (design and flight testing)

Type:  62% scale twin-engine demonstrator for tactical transport

Program:  ATTT, also known as AT3

Powerplant: 2 x Pratt and Whitney Canada PT6A-135A turboprops

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 was 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, 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, first with small additional fins but even that wasn't enough and so an all-new twin-boom tail was fitted, extending behind the engines and making the aircraft's general configuration similar to that of the Rockwell OV-10 Bronco (Model 133-B). This modified configuration is shown in the accompanying photograph. Pratt and Whitney of Canada PT6A-135A 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 electric motors.

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]

Specs: unknown

Crew/passengers: 2

Main sources:

Several views of N133SC at Mojave Airport circa 1989.

The ATTT looking in pretty bad shape on the Edwards Air Force Base south base flightline on October 25, 2003.