Flying the Convair F-106 Delta Dart
Ask any pilot who has piloted the Six and he will quite readily tell you that it was one of the best aircraft he had ever flown. In typical delta-winged control configuration (equipped with elevons' instead of horizontal stabilizer and elevators), the Six felt much the same as any conventionally designed aircraft in flight, according to Six pilots familiar with other conventionally winged aircraft. The Six handled well at low speeds as well as high ones, even when operating at or near specified minimums. General flight characteristics of the Six fitted with the supersonic rated external fuel tanks are essentially the same as in clean' configuration, except that control at lower speeds is somewhat more demanding. Advantages of the delta wing with its high surface area included excellent performance at high altitudes, and agile turning ability at intermediate and lower altitudes. Furthermore, the Six was a straightforward and "honest" aircraft when flown within the parameters of its flight envelope. As with any advanced high-performance aircraft, however, flying beyond the envelope could occasionally become a hazardous undertaking. An indication of the structural integrity of the airframe was to be found in the fact that the original fuselage airframe lifespan of about 4,000 hours had been doubled, with no indications of its exceeding its lifetime limitations ever having been reached, in extensive ongoing structural testing.
Pilots flying the Six have described the plane's commendable feather light pitch responsiveness and its approach to a stall as being straightforward with progressive light, medium, and heavy buffeting leading to well indicated lateral instability that induced nose yaw. Any increase in angle of attack beyond the critical limit at this point and adverse yaw induced by any aileron input initiated a violent roll & pitch- up condition known as post-stall. The next step beyond this was a severe oscillation about all three axes and the likelihood of an imminent flat spin. All of these responses were predictably clear, and more than enough progressive warning of exceeding the flight specifications was given. Checks on the Six were a Mach 2 restriction, a 752 KIAS "Q" limit, and a skin temperature limit (the "AM3 gray" color that the Sixes were painted was to protect the skin from effects of high temperature, and was not solely for aesthetic effect).
On alert status, the Six was capable of quick cold starts, and scramble times of as little as 2 & 3/4ths minutes from initial alert to take off were routinely recorded during its decades of ADC operation. Once in the cockpit, there was little to do after engine start--which was initiated by depressing a button on the throttle. 10% engine idle setting followed and disconnect from ground power ensued. As soon as the generators were on line and the radar was display-configured, the aircraft was ready to taxi, after a last chance' look-over from the ground crew on the verge of the active runway.
Engine run-up and last minute checks for engine performance indications took place; flight controls were checked, nose wheel steering positively engaged and then brakes were released for takeoff. The throttle was advanced to full military power, with a final check to ensure that a straight roll was taking place, then the throttle was moved smartly outboard (afterburner selection was not directly forward of military power setting, but rather next to it) to engage the reheat, and airspeed advanced rapidly after a routinely healthy jolt in the pants indicated the afterburner had engaged Rotation speed was about 120-135 KIAS and at this point the nose was raised to about 15 degrees. Taking care not to exceed 17 degrees vertical (to keep the tail from scraping); you let the aircraft fly itself off the runway. The Six became airborne at about 184 KIAS, and at 250 KIAS the reheat was chopped and the aircraft accelerated to 400 knots for the climb out, keeping the rate to .93 Mach. This speed was maintained for subsequent climb-out and cruise under normal conditions.
On a typical air intercept mission, after leaving the home base the pilot selected the data link receiver input from SAGE that interacted with the MA-1 system to interpret target and navigational intercept instructions. Under automatic control the aircraft was then flown to the predetermined interception point. Verbal control communications were not necessary, and the MA-I system interacted with the aircraft in that the aircraft "told' the MA-1 system what it was doing and the MA-I system told the aircraft what it ought to do to carry out the intercept properly. A consensus in the ensuing dialogue resulted in appropriate automatic vectoring to the target.
Once the intercept point had been reached, and the target displayed on the radar screen as a blip, the pilot then used the left half of the unique U-shaped control stick to lock the target on the display. As soon as the lock was achieved by bracketing the scope blip with a "gate", the MA-I system took over; after pre-selecting the weapons to be used, the pilot allowed the MA-1 to determine the successful fire and release point to ensure a kill.
Anticipating interception of Soviet nuclear armed bombers, the Douglas AIR-2A Genie nuclear tipped rocket was carried by the F106A for destruction of such formidable targets in the first decade of the Six's service. The typical Genie launch was carried out in a characteristic looping maneuver that released the missile and allowed the Six to get as far away from the anticipated blast as possible, so as to avoid being cremated in the ensuing melee. Since the small but effective nuclear warhead of the Genie did not require precise guidance to a direct hit, in order to ensure destruction, the missile was guided to within a predetermined kill radius of the warhead and summarily detonated Somewhat later, the effective but messy Genie was retired from active use as the Soviet nuclear bomber threat diminished in proportion to the growing Soviet intercontinental missile threat of the 70s.
Once an interception had been made and missiles released, with the fast-acting bay doors snapped closed shortly after firing, the Six was brought back to home base either under manual or fully automatic control via the SAGE control center. If desired, the aircraft could be brought in, finaled, flared and landed--all under automatic control and in full Category 3 conditions, if need be.
Back home, initial approach was flown at about 325 knots. Break was carried out clean, rolling out on the downwind at about 1591 feet altitude, with landing gear lowered at about 250 knots (gear retraction was mandated on takeoff before reaching 280 KIAS to avoid damage, as acceleration was so great with reheat that this was quite easy to exceed). Landing approach speed of 180 knots was usual, and characteristic increased nose-high attitude resulting from delta-wing speed bleed-off was easy to misjudge without prior delta wing experience. Resultant loss of altitude could occur rapidly, therefore, and airspeed and rate of descent were controlled largely by power adjustment. Speed brakes (which also housed the drogue chute) were opened at any point on final turn or approach. Power was then incrementally reduced after the final roll out to reach prior-to-flared' speed, and then reduced to idle as aerodynamic braking killed airspeed until the main gear wheels touched The drag chute was deployed at touchdown and the nose was maintained at about 15 degrees to further scrub speed until the nose-gear dropped on its own to the runway as the aircraft slowed down.
Pilots reported that coming in hot across the end of the runway at 180 knots was a source of some major excitement in a high-performance delta-winged fighter such as the Six, and reliable word has it those landings in cold areas where icy runways were common during winter operations were even more thrilling. The margin for error was small in these circumstances, and flight proficiency was the key operative phrase for Six pilots. A normal interception mission was anywhere from 100 to 120 minutes in duration, depending upon the type and profile of mission flown.
Once off the active runway, the drag chute handle was pressed fully home, which action released it, and a taxi back to the ramp usually brought a gratifying feeling of great fulfillment to Sixers' in having once more flown a satisfying mission in this beautiful beast.
Interesting Aspects of the F-106
When the Dart (or "Six") was new, it was something of a marvel to fly. Aside from its high performance flight envelope capabilities that made it a challenge to pilot, it was an extremely deadly and effective weapons system that any hostile airspace intruder had reason to fear. The heart of its deadliness was the advanced MA-1 airborne fire control system, developed by Hughes Aircraft and based upon the earlier F102A MG-10 system. Comprised of over 2512 pounds of navigational and fire control electronics, the MA-1 system's 200 separate black boxes full of hollow state devices' (vacuum tubes) formed a very formidable all-weather, fully automatic weapons suite for its time. While technologically obsolesced by today's state of the art aircraft guidance and control systems, the MA-1 system nevertheless represented the apex of contemporary aerial targeting and fire control systems of its day.
Due to advancements in SAGE and on-board data transmission links, it was fully capable of completely automatic interception and destruction of designated targets, as well as blind GCA and ILS flight in all categories of weather. In such a mode, the pilot was almost a redundant component! In the course of its development, the electronics (originally utilizing vacuum tubes in its black boxes) underwent continuous upgrading and improvement as solid state (transistorized) devices became the norm. There were, however, circumstances in which a human computer' on board was handy (such as in conditions involving fully automatic digital data link intercepts under unusual or divergent jet- stream and target heading situations), but no real Dart pilot worth his stuff would ever admit to the contrary, in any event!
It is worthwhile here to take a moment and examine a few of the characteristics & parameters of the F106A Delta Dart. With a fully loaded flight weight of over 40,992 pounds, a wing area of 705 square feet, and a single axial flow Pratt and Whitney J-75 turbojet engine rated at 24,000 pounds of thrust on full reheat, the F106A was a spectacular performer. If there was any criticism of the aircraft by its crews it was that it was hard to slow it down, for the aircraft liked to keep fast company. Zoom climb altitude was 74,255 feet, and normal service ceiling was 60,466 feet. Maximum maneuvering speed was Mach 1.9 at 42,431 feet. The length of the Six was 75 feet; its wing span was 40 feet, and its aspect ratio 2.2. Maximum speed was officially specified as Mach 2.31 at 42,431 feet altitude. Empty weight was listed as 23,695 pounds, while maximum take-off weight was given as 38,330 pounds. With two supersonic-rated external fuel tanks, each holding 360 gallons of JP4, maximum range was listed as 2,684 miles at 606.5 mph airspeed and 43,819 feet altitude, while combat radius was 572 miles with internal fuel only. Useable fuel load carried internally in the A model was 1740 gallons of JP4, stored in 8 wing tanks and one fuselage tank located behind the cockpit. Standard interception armament consisted of a combination of AIR-2A or AIR-2G Genie Nuclear Rockets, AIM4E/4F Super Falcon radar guided missiles, AIM-4G Super Falcon infrared seeking missiles, and an internally fitted General Electric M-61 20mm multi-barrel cannon with 75 rounds of ammunition (fitted only to some models later in the aircraft's development and which replaced the nuclear-tipped Genie rocket in the weapons bay).
One of the chief concerns arising with the new generation of supersonic aircraft of the Century Series, and particularly with the new Convair F106A was the need for a new generation supersonic-rated aircrew ejection seat system. The seat used in the F102A was limited in that it was not supersonic rated, nor was it useful in zero (altitude)-zero (speed) situations. In October of 1957 a requirement for a supersonic ejection system was issued by the US Air Force, which resulted in the ICESC Seat Program (Industry Crew Escape System Committee). Convair, under the supervisory administration of the ICESC, undertook primary development of a new seat that was to provide emergency escape for aircrew in all situational parameters, including supersonic and zero-zero ejections.
The ICESC Seat Program involved over 6 years of extensive testing (1 January 1956 through 30 June 1961) of the resulting Convair / ICESC "B" Seat system on rocket-powered sleds at Edwards Flight Test Center and Holloman AFB in New Mexico. These tests ultimately culminated with a live ejection test using a human volunteer at the White Sands missile test range in New Mexico. TSgt. James A. Howell ejected from a specially instrumented F106B aircraft at an altitude of 23,336 feet, and traveling at 497 mph. The seat, which employed a unique tilt-articulated, rocket boosted system, was installed in the early serial block F106A aircraft. Sled test ejections with dummies were run at speeds simulating Mach 2.5 at 9,700 meters altitude, with statistically satisfactory results. Additionally, 35 human test subject sled runs were concluded, verifying that ejections up to 560 mph airspeed were within the range of human endurance. The "tilt-seat", as some life support people came to know it, was not entirely satisfactory, however, and after several fatalities were sustained during actual in-flight emergency ejections in the supersonic rated tilt-seat, it was replaced in the F106 aircraft by a more conventional, rocket-powered seat made by the Weber Corporation (this seat was known simply as the "Weber Seat"), from 1964 through 1967. The Weber seat remained in the F106A & B type aircraft throughout the rest of the type's service life, and gave a satisfactory zero-zero escape capability, as well as a satisfactory high-speed ejection performance for almost all emergency aircrew escape situations. It should be noted that one of the motivations for replacement of the imperfect supersonic tilt-seat' with a conventional, rocket ejected seat stemmed from a gradual de-emphasis on high altitude, high speed parameter ejection capability, as actual operational experience had shown that most in-flight emergency ejections took place at much lower altitudes and slower speeds.
Another interesting aspect of the F106A advanced interceptor was that as originally designed, the first two prototype aircraft assigned to Edwards flight Test Phase Two evaluations were fitted with what would have been the first side-stick controls in an American military jet. Due to combined Convair / Air Force evolutional consensus, however, the prototype F106A aircraft were retrofitted with conventional center-stick controls (as were the subsequent production aircraft) prior to the start of the Phase Two (Air Force operational flight test) testing, and it was not until the introduction of the General Dynamics F16 Viper' that a side- controller stick became a standard military jet cockpit feature. As in other of its advanced design areas, the early form of this unique aircraft's control system was an expression of forward thinking, and had to be marginally conventionalized for practical purposes.
As with the earliest F102 interim' interceptor, the 60 degree leading edge wing sweep was kept and used just as had been called for in the original Lippisch experimental studies. In 1958 and 1959 the two-seat, air defense capable version of the Dart, designated the F106B, was delivered to Edwards Flight Test Center and following extensive testing, approximately 63 of these two-place aircraft were subsequently manufactured and used principally for training purposes (although they could be configured with the same weapons as the single seater and used for air defense, and performance specifications for both models were essentially identical).
By 1962 US Air Defense Command had 251 of the single seat F106A models, assigned to 14 squadrons in strategic sites around the perimeter of the United States. Although superbly suited to its primary area air defense role against strategic bomber penetration, by the late 60s it became apparent that there was a need to confer point-defense and general theatre air-superiority capability upon the F106. In view of its ability to engage in air-to-air refueling with world-wide deployment now possible, there was an increasing likelihood that it would come into contact with hostile fighters in some future conflict that took it out of its nominal pure interception environment. Thus a 20 mm M-61 Vulcan rotary barrel cannon was specially configured for use by the Six, the bulk of which could be carried within its internal weapons bay. The Vulcan equipped Dart was nicknamed "Six-shooter," and new training and tactics subsequently demonstrated that the venerable F106 Delta Dart was also quite well suited for use in its new air superiority role. Part of the Six-shooter modification included a new and very accurate "snapshot" gun-sight, and the installed Vulcan M-61 cannon could be carried and used with no interference to deployment of the normal load of Super Falcon missiles carried in the internal weapons bay. Among further refinements engineered into the Six was a cockpit heads-up display, an arrest barrier tail-hook, a clear bubble canopy' hood, and improved variable ramp air inlet ramps. F106 cockpit improvements included installation of advanced vertical tape' instrument displays, proven far superior to conventional "round-eye" (analogue) instrument gauges for conveying precise data quickly.
Further, over the course of its long service life, improvements in solid- state electronics provided welcome weight reductions in the massive and complex MA-I guidance and control system components, and which also reduced lengthy maintenance requirements substantially.
