Aviation Ancestry - March 2011
The Northrop F-89 Scorpion, Part II
By Scott Schwartz
(Scott Schwartz)The decision to buy the F-89 was ultimately made after a USAF board recommended the acquisition of the aircraft during a meeting in September of 1948. Despite being fitted with more powerful engines, the XP-87 was still under-powered. Choosing the F-89 over the Curtiss F-87 marked the end of Curtiss-Wright as an aircraft manufacturer (today, the company builds aerospace components and pumping equipment). Nevertheless, the Air Force was not 100 percent confident in the XF-89, and it wanted alternatives. Accordingly, specifications for another all-weather fighter were issued at around the same time that the decision to buy the F-89 was made. In response to these new requirements, North American altered its F-86A by installing an after-burning engine and more sophisticated radar equipment. The resulting aircraft was initially referred to as the XF-95, but was later designated as the F-86D. Lockheed’s answer was a modified version of its two-seat TF-80C trainer, which eventually became the F-94.
October of 1948 saw the F-89 ordered into actual production – with then Secretary of Defense James Forrestal giving his stamp of approval. Forrestal also approved the construction of two Lockheed YF-94 prototypes and 150 production examples.
The money to build the F-89 and the F-94 was released in January of 1949, by President Harry Truman. Forty eight F-89s were to be built. During this same month, the Air Force approved the continuation of the XF-95 program, figuring that it would “supplement” the F-89 until the Convair F-102 entered service.
With the development of “back-up” aircraft set in motion, the USAF began testing the XF-89 in February of 1949.
All went fairly well during the first 48 test flights of the XF-89. However, it was during “Phase II” of the flight tests that an accident occurred. The date was June 27, 1949. Apparently, the main landing gear doors were not aligned properly, which caused the wheel wells to become pressurized This, in turn, forced the left main wheel out into the slipstream – during a high-speed, low-pass. The result of all this was the detachment of the left main landing gear from the rest of the airplane. A crash-landing ensued, and the aircraft was repaired in time to demonstrate it to the Air Force in July. Still, the F-89 was a year behind schedule at this point. Despite all this, the Air Force contracted for an additional 64 F-89As in October of 1949 – ordering another 122 F-86Ds during that same. Eventually, more than 2,500 F-86Ds would be built – nearly 500 more than the total number of F-94s and F-89s built.
First flying on November 15, 1949, the second Scorpion – the YF-89 – was accepted by the Air Force in January of 1950. Seemingly, the F-89 program was smoothing out. However, this illusion was shattered by another crash, which occurred on February 22, 1950. While Northrop pilot Charles Tucker was making a high-speed, low-pass in the XF-89 (this time in front of observers), the skin from the right horizontal stabilizer came off. This resulted in the whole empennage separating from the aircraft. Tucker was able to parachute to safety, but flight engineer Arthur Turton was not.
The old problem with the engines’ exhaust gases had reared its ugly head. The engine exhaust exit path had caused the horizontal and vertical stabilizers to flutter, resulting in their failure.
At this point, changes were made to the YF-89, and these included the addition (finally) of afterburning engines and the lengthening of the nose by three feet. How these changes solved the buffeting problem is unclear to this writer, but the airplane was re-designated as the YF-89A. The aircraft was also officially named Scorpion at this time.
Despite the delays and problems with the aircraft, the Air Force accepted the first production F-89A in September of 1950.
By the spring of 1950, three F-89As had been delivered to the Air Force, and the Korean War was heating up. With the departure of some of its fighter-interceptor wings to the Far East, and with the F-89 program behind schedule, interceptors were needed to fill the gap in U.S. air defense at home. To make matters worse, the first 18 F-89As that were scheduled for delivery to the Air Force, were not combat-capable. This is because the buffeting/fluttering problem had been “solved” by mounting external counter-weights on the aircraft. The Air Force authorized the production of the aircraft with this “fix” in place – that is, until the turbine failures started occurring in the Alison J-35-A-21 engines.
Enough was apparently enough, and John Northrop met with General Hoyt Vandenberg and his staff in November of 1950. At the meeting, Northrop was told that the fluttering problem had to be resolved once and for all by January of the following year; otherwise, the Air Force would not buy anymore F-89s. Further, production of the F-89 was stopped. Considering that the company had recently lost the RB-49 contract, things were not exactly looking up for Northrop.
Apparently, the Air Force was somewhat mollified, because production was resumed in January of 1951, with four more F-89As being delivered. Three of these were fitted with the six 20 mm cannons that were planned for the F-89B and C models. The fourth aircraft was equipped with a rotatable cannon turret in the nose, again, for test purposes. Ultimately, only 11 F-89As were actually kept as F-89As; these aircraft were flown for test purposes only. The rest of the aircraft built in connection with the initial order were upgraded to F-89B standards. F-89Bs were equipped with upgraded avionics, which eventually included the Lear (yes, that Lear) F-5 auto pilot, and the F-89B was the first Scorpion variant to be assigned to the USAF’s Air Defense Command. Deliveries to the Air Force began in February of 1951.
F-89Bs were soon replaced with F-89C models; the chief differences between the B and C models were that the elevator counter-balance weights were mounted internally on the F-89C, and the C model was outfitted with a fuel-system purge generator to prevent fuel vapor from accumulating in the fuel cells.
The first F-89Cs were delivered to the Air Force in November of 1951. By February of 1952 the first of several crashes due to F-89C wings separating from fuselages occurred. In September of that same year, the F-89 was grounded, after six of these incidents had occurred.
After an investigation, it was believed that the wing failures were due to pilots “over-stressing” the aircraft, and flying (albeit with some airspeed and “g” force restrictions) resumed.
All was apparently well until a few more F-89Cs were lost due to wing failures in July and in September of 1952. These problems, as well as the delays that were occurring with the F-102 program prompted the Air Force to look at the McDonnell F-101 (which was designed as a long range escort/fighter-bomber) as a possible interceptor aircraft for the Air Defense Command.
Nevertheless, Northrop began to re-design the F-89 in November of 1952, and the main changes involved strengthening of the wing spar and the installation of fins on the wing-tip tanks. The Air Force then began to return its F-89Cs to Northrop, so that the modifications could be made to existing aircraft. Besides having to do all of this extra work, Northrop was responsible for ferrying the aircraft back to the plants for the modifications; the Air Force refused to let its own pilots make these flights.
All-told, the F-89 wing modifications wound up costing roughly $17 million. Further, the first modified F-89Cs were not available for use by the Air Force until January of 1954. By the end of that year, the F-89 C was considered to be obsolete; consequently, the “C” models were transferred to Air National Guard squadrons.
In the meantime, one of the earlier F-89Bs had been re-built as a YF-89D. The F-89D differed from previous versions mainly in that it was armed with rockets only. The rockets were actually launched from the noses of the wing-tip fuel tanks. The wisdom of launching rockets from fuel tanks may seem questionable, but the danger was offset by venting the rockets exhaust gases and heat away from the aft section of the tanks. The F-89D was also equipped with a more powerful version of the Alison J-35 engine and an additional fuel tank in the nose.
Despite its perceived potential, the F-89D was initially included in the grounding order along with the F-89C. Once the order was lifted (in November of 1953), and the F-89D was flying in Air Force service, problems with even this variant became apparent. The wings were still not as strong as they should have been. This resulted in the airspeed being limited to 425 mph below 25,000, and maneuvers could not exceed 5 Gs. On top of all this, the engines lost power above 30,000 feet. Under these conditions, the aircraft made a fine interceptor, if the targets were to be piston-engine bombers. But, against faster jet bombers, the F-89 was virtually useless.
Things got even worse, when it was found that the rocket tubes would sometimes collapse after a rocket launch. This would cause a small explosion, rendering the remaining rocket tubes useless.
Roughly half of the 682 F-89Ds produced were sent back to Northrop for re-building as F-89Js. There were no newly built “J” models – all were formerly F-89Ds. The F-89J’s wing-tip tanks were just fuel tanks, and pylons for launching nuclear-tipped Genie rockets or Falcon air-to-air missiles, were mounted under the wings.
There was an F-89H, which was capable of launching Falcon missiles and small folding-fin rockets from its modified tip tanks. Unfortunately, delays in refining its fire-control system delayed the “H” model’s deployment until 1955. By that time, other interceptors had already surpassed it in performance. By 1959, the F-89H had been phased out of service.
The F-89J was the last version of the Scorpion produced and was the only aircraft ever to fire a live Genie nuclear rocket. Still, the F-89J was a heavy, somewhat underpowered aircraft; it could barely hit Mach .82 – which was comparable to the cruising speeds of the then-new 707 and DC-8 airliners.
Despite its limitations, the F-89J soldiered on with Air National Guard units until 1969. It was also used as a training and drone-control aircraft.
Given the problems that the Air Force experienced with the aircraft, it is hard to find anything positive to say about the F-89. As with many 1950s jet aircraft though, the F-89 was a melding of 1940s technology with the “cutting edge” advances in electronics and missile technology of the 1950s. This was a tall order, especially when one considers that this was the era when electronic equipment tended to be very heavy. This may explain some of the structural problems experienced with the F-89. It should also be remembered that the deployment of the F-89 to stateside squadrons freed the F-86 up for combat in the Far East, and that the F-89 was not the only aircraft to experience “teething troubles” during its development.
