Sixty-three years ago this week, the USAF/Convair XF-92A Dart made its first official flight from Muroc Army Airfield in California. Convair test pilot Ellis D. “Sam” Shannon was at the controls of the experimental delta-winged aircraft.
The XF-92A Dart holds the distinction of being the first delta-winged, turbojet-powered aircraft in the United States. It was designed and produced by the Consolidated Vultee Aircraft (Convair) Company for the United States Army Air Force. Only one copy of the type (S/N 46-682) was ever built and tested.
At the time, the delta wing planform was something of a novelty. Convair designers chose this shape principally due to its aerodynamics benefits. For example, transonic wave drag is significantly lower than that of a swept wing of equal area. The delta wing also exhibits favorable lift-curve slope, center-of-pressure travel and ground effect characteristics.
The large chord of a delta-winged aircraft allows for static pitch stability to be realized without the use of a classic horizontal tail. Pitch control is obtained via wing trailing edge-mounted elevons; surfaces which combine the functions of an elevator and the ailerons. When differentially-deflected, elevons provide roll control.
The XF-92A measured 42.5 feet in length and had a wing span of 31.33 feet. Empty and gross weight were 9,978 lbs and 14,608 lbs, respectively. Early in its development, the XF-92A was powered by an Allison J33-A-21 turbojet which generated a maximum thrust of only 4,250 lbs. The final version of the aircraft was configured with an Allison J33-A-16 turbojet which produced a maximum sea level thrust of 8,400 lbs.
The XF-92A made its maiden flight on Saturday, 18 September 1948 from Muroc Army Airfield, California. Convair test pilot Ellis D. “Sam” Shannon did the piloting honors. Although the aircraft handled well, it was a bit over-responsive to control inputs. In addition, the XF-92A was underpowered.
Convair completed the last of 47 Phase I test flights on Friday, 26 August 1949. The Air Force conducted the first Phase II flight test on Thursday, 13 October 1949 with none other than Major Charles E. “Chuck” Yeager at the controls. Phase II testing was completed on Wednesday, 28 December 1949 by USAF Major Frank K. “Pete” Everest.
Following Phase II testing, the aircraft was re-engined with an Allison J33-A-29 turbojet capable of generating 7,500 lbs of sea level thrust. The Air Force continued to fly the XF-92A on various and infrequent test missions into February of 1953. Pilots of historical note who flew the aircraft include Al Boyd, Kit Murray, Jack Ridley, Joe Wolfe and Fred Ascani. It appears that the Air Force flew a total of 47 flight tests using the XF-92A.
The lone XF-92A was turned over to the National Advisory Committe For Aeronautics (NACA) once the Air Force was done testing it. The aircraft was promptly configured with an Allison J33-A-16 turbojet that generated 8,400 lbs of sea level thrust. NACA test pilot A. Scott Crossfield flew the XF-92A a total of 25 times. The type’s last flight occurred on Wednesday, 14 October 1953.
The XF-92A was not all that great from a piloting standpoint. Among other things, the aircraft had a severe pitch-up problem which produced normal accelerations between 6 and 8 g’s. The XF-92A was also plagued with landing gear failure problems. As noted previously, the aircraft was underpowered; a situation that was not uncommon for jet-powered aircraft of the era.
Inspite of its flaws, the design and flight experience gained from the XF-92A’s development led to an extensive series of delta-winged highly-successful aircraft produced by Convair in the 1950’s. These historically-significant aircraft include the F-102 Delta Dagger, F-106 Delta Dart, B-58 Hustler, XF2Y Sea Dart and XFY Pogo.
