F-89B "Scorpion"
New features included in the F-89B were mostly internal changes and additional equipment, including Lear F-5 autopilot, a Zero-Reader, and an instrument landing system (ILS). The aircraft was first accepted in February 1951, more than 5 years from the date Northrop had been authorized to proceed with development of the F-89. The aircraft entered operational service in June 1951. ADC's 84th Fighter Interceptor Squadron, at Hamilton AFB, was the first to acquire the new aircraft.
The F-89B experienced intitial problems. Engine failures marred the beginning of the operational life of both the F-89A and F-89B aircraft and seriously affected the Air Proving Ground concurrent operational suitability tests of the two model series. This problem led to the use of modified engines (J-35A-21A) that eventually replaced the J35-A 21s, originally installed in the first 48 F-89s to emerge from the assembly line.
Modifications were necessary; all F-89As and Bs had externally mass-balanced elevators, adopted to overcome a severe high-frequency, low amplitude flutter induced by the jet exhaust, but elevators with internal mass balance were fitted to earlier models after being developed for the F-89C, which followed the B series from the production line. Most of the first 48 F-89s were included in the F-89C's post-production modification program. Productions was ended in September 1951 with the delivery of the final four aircraft. Nineteen F-89Bs were accepted in FY 51, and 18 during the first 3 months of FY 52 at a cost of: $1,086,882.00-airframe, $950,298; engines (installed), $90,364; electronics, $4,870; armament, $40,350. The F-89B was phasedout in 1954. Like the As, the F-89Bs left the Air Defense Command early in 1954. They first equipped the ANG's 176th FIS, replacing the squadron's elderly F-61s.
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