F-89A "Scorpion"
Funds released by President Harry S. Truman in January 1949 enabled the Air Force to execute, during May of that year, a cost plus-a-fixed-fee contract amounting to some $48 million, excluding a fixed-fee of almost $3 million. The estimated costs stipulated in the contract covered modification of the second XF-89 (YF-89) and fabrication of the first 48 production aircraft (F-89As). Spare parts, ground-handling equipment, special tools, and one static test article were included. Northrop received an additional order for 27 F-89As on 19 September 1949.
Although damaged on 27 June 1949, because of the failure of its main landing gear, the experimental aircraft was repaired in time for Air Force acceptance in July 1949-1 year behind schedule. This aircraft, involved in a new series of trials since February, had been re-equipped with "decelerons," a split surface operating in one piece as a conventional aileron but which could be opened out to serve as dive brake and auxiliary landing flap. The decelerons, developed by Northrop, eventually became a standard feature of all F-89 productions.
On 22 February, during the second Phase II flight test of its ability to meet all-weather interceptor requirements, the XF-89 crashed and was damaged beyond repair. By that time, the second experimental F-89 (YF-89) was already in flight test, having been first flown on 15 November 1949 and accepted by the Air Force in January 1950.
Review of the XF-89's last flight test report aroused great concern. Despite substitution of the J-35-A 9 for the TG-1804 (J3bGE-3) engine (initially proposed by Northrop), the aircraft still lacked power; it also had poor takeoff characteristics and a slow rate of climb. In addition, the tests confirmed the existence of suspected deficiencies and disclosed that known failings had not been corrected. Shortly before the February crash, the aircraft had demonstrated little endurance, disappointing altitude performance, signs of instability, and questionable structural integrity. Moreover, although major changes had already been introduced in the second experimental aircraft (YF-89), the latter undoubtedly still carried many of the deficiencies recently identified in the lost aircraft.
Loss of the XF-89 prompted the modification of the YF-89 and addition of an "A" suffix. Among the changes made to improve performance was the substitution of even more powerful engines-J-3S-A 21s with afterburners in place of the J-35-A-9s that had powered the first experimental aircraft. The YF-89A also had a more pointed nose which lengthened its fuselage to 53 feet (3 feet longer than that of the F-89). The newly designated YF-89A first flew on 27 June 1950.
As pointed out by Northrop in mid-1950-immediately following the YF-89A's successful June flight--the F-89 was probably as good as "the state of the art at the moment would permit" and most likely surpassed any other aircraft currently in production. Although skeptical, the Air Force decided to reserve judgement until further testing of the Northrop second F-89 configuration could be made. For this purpose, one of the F-89As already manufactured was accepted on 28 September 1950, and two more before the end of the year. Meanwhile, production, which had been halted after the February crash, remained suspended.
With the understanding that unless solutions were forthcoming, other interceptor sources would be investigated, the Air Force reendorsed the F-89 program. The decision was accompanied by stringent conditions. Testing of the new YF-89A would be accelerated; early F-89A productions (particularly, the three aircraft already accepted) would be subjected to a series of special tests to determine if recently introduced modifications had eliminated earlier flutter problems; no other unproven F-89As would be accepted, and production would not resume until January 1951, Northrop's deadline for correcting all known deficiencies.
Satisfied with Northrop's progress, the Air Force finalized longpending negotiations for the purchase of additional F-89As. Procurement of the F-89As ordered in September 1949 was reapproved and a July 1950 letter contract was reactivated. Overall, though, the number of additional aircraft purchased was decreased because of the extra costs generated by recent configuration changes. In fact, the aircraft finally bought in 1951 differed sufficiently from early F-89As to acquire new model designations. They entered the Air Force inventory either as F-89Bs or F-89Cs and carried higher price tags than first anticipated.
Eleven total F-89As were accepted-37 less than ordered under the first production contract of May 1949. All F-89As were accepted in FY 51-between September 1950 and March 1951.
Because of their limited number, the F-89As contributed little to the Air Force operational capability. Most of them were used for extensive operational suitability tests that did not end until mid 1952. Nonetheless, some F-89As joined subsequent model series in the operational inventory of the Air Defense Command. The F-89A was phasedout in 1954
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