The F-106 was powered by a single Pratt and Whitney J75 axial-flow, dual compressor J75-P-17 turbojet engine producing 16,100lb's of thrust, 24,500lb's of thrust in afterburner. The original engine used duringearly testing was the J75-P-9, but the -17 later replaced it. The J75 was a scaled up J57 and first flew in 1955. This turbojet was in production from 1956 through 1967 and was the same engine which poweredthe Republic F-105 Thunderchief.
The -17 model included a modified afterburner exhaust shroud with a redesigned exhaust called the Idle Thrust Nozzle. The exhaust shroud wrapped the entire exhaust cann encasing the entire afterburner exhaust area andhoused the exhaust eyelids or the or Converent-Diverent Nozzle. The eyelids were closed between idle and full-mil throttle, but opened when going into afterburner during take=off and at altitudes below 30K feet.Above 30k feet there was no delay when the afterburner was selected as the nozzle did not open prior to A/B light off. When they did however, at take-off, the 2 second delay between fullmil throttle and AB light off wasto allow for the eyelids to open. If they didn't - - eyelids all over end of the runway, which did happen on rare occasions. This eyelid process was automatic.
The actual shape/design of the shroud exhaust was to limit the motors idle thrust, which tended to blow everything everywhere on the ramp and while taxiing, so for the -17 model Pratt Á Whitney reesigned theexhaust with the Idle Thrust Nozzle.
One Pratt Whitney J75 P-17
24,500 pounds thrust with afterburner
Maximum speed: 1,587 mph
Cruising speed: 650 mph
F-105 Thunderchief by Republic J75-P-19W with Water Injection
U-2 Draon Lady by Lockheed
The F-106 Delta Dart featured a Variable Inlet Ramp ("vari-ramp") System designed to modulate airflow to the Pratt & Whitney J75-P-17 turbojet engine, allowing for optimal performance across a wide speed range. These ramps managed the engine's intake to avoid supersonic air, which a jet engine cannot digest. The vari-ramp system was a key differentiator in performance for the "ultimate interceptor," enabling it to efficiently operate at high altitudes and speeds that surpassed the F-102 and in top-end speed, the F-4.
Function and Purpose: The vari-ramps were critical for ensuring that, at supersonic speeds, the air entering the engine was slowed to subsonic speeds while maintaining high pressure at the engine face.
Operational Mechanism: Intake ramps began closing at Mach 1.4 to restrict airflow to the front compressor.
Performance Optimization: The system was designed to handle the airflow needs of the engine up to top Mach. Some analysis indicated that while the system worked well, a steeper ramp angle could have optimized performance even more at speeds above Mach 1.8.
Design Characteristics: The ramps were crucial for stabilizing the inlet airflow. Similar to the F-4 and other Cold War-era supersonic aircraft, the F-106 relied on these mechanical, variable-geometry components to manage shockwaves.
Maintenance: The "vari-ramp" system, along with the engine and intake splitter plates, was a key component of the F-106's high-speed interceptor performance, often requiring specialized maintenance and careful monitoring of engine intake runs.
The first F-106A 56-0451 was finally available by the end of 1956, making its first flight on December 26, 1956. The second F-106A 56-0452 followed on 26 February 1957. These first two aircraft were not equipped with the MA-1 system. Thet carreid nose ballast to compensate for that missing weight. The test and development work on the F-106 was divided into six phases. Phase I was conducted by the contractor, and Phase II was conducted by the Air Force. Phase II tests were carried out between May and June of 1957.
These first 12 aircraft off the production line were devoted to tests at Edwards AFB in California. They differed from the prototypes in having J75-P-9 engines. Early testing reached a speed of Mach 1.9 and an altitude of 57,000 feet, but this was still well below expectations. In addition, the F-106A's acceleration was significantly below Convair's estimates, and it took almost 4 1/2 minutes to accelerate from Mach 1 to Mach 1.7 and another 2 1/2 minutes to accelerate to Mach 1.8. With such poor acceleration, it was felt that Mach numbers above 1.7 would not be tactically usabl
The poor speed and acceleration was cured by altering the aircraft's air intake cowling and charging ejectors. The capture area of the intake ducts was enlarged and the duct lips were thinned down. There were also problems with the reliability of the J75-P-9 engine. Eventually, the more powerful J75-P-17 engine was substituted, rated at 17,200 lbs thrust dry and 24,500 lbs thrust in afterburner. There were further problems with the MA-1 fire control system and with the cockpit layout. Originally, the control column had occupied the traditional center location, but was later moved to the side at USAF insistence in order to ensure an unrestricted view of the Horizontal Situation Indicator. This arrangement turned out not to be viable, and the control column was later moved back to the center and equipped with a two-handed grip for both radar and aircraft control. The right-hand grip was used for control of the aircraft and the left-hand grip was used for operation of the radar. A button in the middle of the yoke gave the pilot control of the radar antenna, and another button on the left grip enabled the pilot to put the pipper on the target by following directions on the radar scope. The pilot selected the missiles to be fired by using a switch on the left console, with the trigger that was used to launch the missiles being on the right hand grip.
Early test aircraft had explored both conventional round-faced instrument panels and panels with vertical-tape instruments. However, the first three squadrons of F-106As were sent to the field with analog or round instrument dials. Eventually, the vertical tape instrument set, know as Integrated Instrument Display (IID), was made standard starting with aircraft 58-0759. Some of the early aircraft were subsequently upgraded with IID, but many never got the vertical tapes. Initial aircraft had wing boundary layer fences as on the F-102, but production aircraft had wing leading-edge slots instead
