The Cold War was alive and well early in 1975. In January, Russia broke its trade agreement with the United States and the next month, the two superpowers traded nuclear tests.
"Cold" was also the operative word at Grand Forks Air Force Base in North Dakota, where average daily temperatures that time of year range from the high teens to several degrees below zero. And that's where a small team from the U.S. Air Force, McDonnell Douglas and Pratt & Whitney had gathered to attempt to shatter eight "Time to Climb" aircraft records and reestablish the country's dominance in the skies.
The records - measures of time to reach specified altitudes from a stationary start on the runway - were particularly important to the Air Force since a Soviet aircraft, the MIG-25 "Foxbat," held the three highest ones, having been set in 1973. (The five lower altitude records had been held by the Air Force's F-4 "Phantom" since 1962.)
Forty years ago and over 16 days, an F-15A fighter jet, dubbed the "Streak Eagle," set the "Time to Climb" records in distances ranging from 3,000 meters to 30,000 meters. Powered by twin Pratt & Whitney F100-PW-100 turbofan engines, together producing almost 48,000 pounds of thrust with full afterburner, the eight marks weren't just beaten, but shattered by wide margins. The records were possible because the aircraft was the first combat fighter to have a thrust-to-weight ratio of greater than one.
Retired U.S. Air Force Col. Scott Willey was the Air Force's production manager for the F-15 and F-14B engine programs, in charge of production and quality assurance in East Hartford, Connecticut, during the "Time to Climb" event. "The Air Force was adamant about establishing air superiority against anything the Soviets came up with," he said. "The F100 team had a mission to produce the best engine and it was important to all of us. We worked hard, it was fun and 'Streak Eagle' was part of it. There was a mystique to this new aircraft. It wasn't nervousness; we were confident that the airplane could set the records. With a good cold day and the best airplane in the world, there was no doubt about it."
Steve Shobe, currently Pratt & Whitney's manager for F100 International Engineering, is a 42-year employee and has spent his entire career in Engineering on the F100 program. "The 'Time to Climb' records were a big deal at Pratt because of the Cold War and because we were determined to provide the best engine for the best fighter in the world," he said. "There was a lot of publicity here about the records because we played such an integral role in making it happen."
"It was a case of talented people working together on an important goal with a singular purpose, in an efficient and friendly manner," said Dennis Enos, a 27-year-old flight test engineer at the time who headed up the Pratt & Whitney team in North Dakota and who retired in 2006 as vice president of Commercial Development Programs after almost 38 years with the company. "We were willing to take significant risks, but we were never willing to take risks without thorough analysis and thought."
The "Streak Eagle" story actually began with test flights at the McDonnell Douglas factory facility in St. Louis in the summer of 1974 on the 17th F-15 produced. Eleven flights occurred before the plane was ferried to Edwards Air Force Base in late summer for further testing.
The testing was important because the "Streak Eagle" was such a unique aircraft. While the F100 engines being used were production power plants, the F-15 was significantly modified for the record attempts. To reach the various altitudes in record time meant minimizing the aircraft's weight by removing what was deemed to be unnecessary or redundant equipment. The tail hook and ladder to the cockpit came off, as did flaps, the air brake, guns and fire control system avionics. Redundancies resulted in the hydraulics and the environmental bleed system being attached to only one engine. Something that wasn't redundant, but was deemed to be expendable, was most of the cockpit navigation instrumentation. Because of that, clear skies were a necessity when ferrying the Streak Eagle to various sites or when attempting its record flights.
At Edwards, more than 30 flights took place. "We had a lot of testing to do at Edwards," Enos said. "For example, we knew the engines would stall at the higher altitudes when we were attempting the records. So the pilots practiced 'dead stick' landings on the dry lake bed to be ready in the event the engines couldn't be restarted. In addition, it had to be ensured the batteries were operating properly for the hydraulics if we needed them when the engines were out. The pilots also had to gain proficiency in all aspects of the mission profiles. For example, they had to get used to accelerating at near sea level up to 500 miles per hour at 10 to 20 feet off the ground before pulling up."
The "Streak Eagle" arrived at Grand Forks just after Thanksgiving in 1974. The team of pilots was led by Pete Garrison, chief development test pilot for McDonnell Douglas, and U.S. Air Force Maj. Roger Smith (an Edwards Air Force Base test pilot). Joining them as "Streak Eagle" pilots were U.S. Air Force Maj. Dave Peterson (an Edwards Air Force Base test pilot) and Maj. "Mac" MacFarlane (a Tactical Air Command pilot). U.S. Air Force Maj. Joe Higgs flew the F-4 chase plane for the record flights.
For each attempt, the plane was taxied to the end of the runway and hooked up to a hold-back bar. The pilot throttled to full afterburner, the explosive bolt was released and the aircraft shot down the runway, lifting off after a take-off roll of only about 400 feet. To lessen even more weight for the attempts, only enough fuel to complete each flight was on board. With less fuel and by eliminating unnecessary or redundant equipment, the aircraft thrust to weight ratio neared 2 to 1.
A few practice flights were held for each of the pilots, and brand new production engines were used that had been specially adjusted for altitude starting. "But Grand Forks in the winter isn't the best place for clear weather and we needed good conditions to fly," Enos said. "For three straight weekends, we had blizzard conditions. We spent a lot of time waiting for the weather to clear."
"There wasn't a lot of nervousness or tension," Enos added. "We had almost a total level of trust on the team. Granted, there was pressure to get through all the record attempts given the amount of time we were there. But we'd get critical information from 'back home,' make decisions and we'd go. The message from Pratt management was very clear – we will fully support the 'Streak Eagle' program. If we made a request, it was taken care of in a very timely fashion. Everyone was behind it."
Enos added that the small size of the team helped build trust and camaraderie. "There were five pilots; two engineers from McDonnell Douglas; myself and Jim Miles, who took care of all the engine logistics, from Pratt; and the 15-20 person Air Force and McDonnell Douglas maintenance team that supported the 'Streak Eagle' and chase planes. The technical challenges were big, with a significant amount of risk to the aircraft and the pilots. However, there was never a decision that wasn't fully analyzed and evaluated. Only then would the decision to move forward be made."
More than 60 flights were flown leading up to and including the record attempt. Record flights were flown, in ascending order at meter intervals of 3,000/6,000/9,000/12,000/15,000/20,000/25,000 and 30,000.
January 16, 1975, was historic, as records for the first five altitudes fell in the space of six hours, with the three in the middle all occurring on the same flight. On the first record flight, the "Streak Eagle" was flown to the 3,000 meter height in 27.57 seconds, eclipsing the old mark by a margin of 6.9 seconds.
The 6,000 meter record of 39.33 seconds (by a margin of 9.5 seconds); 9,000 meters in 48.86 seconds (by a margin of 12.8 seconds); and 12,000 meters in 59.38 seconds (by a margin of 17.7 seconds), were all set on the same flight. Maj. MacFarlane flew this record flight. "He lifted off in the blink of an eye, level accelerated just a few feet off the ground, pulled up into a vertical climb and accelerated through the speed of sound easily while in the vertical climb," Enos said. "The airplane and engines operated perfectly."
For the record attempts at 15,000 meters and above, pilots wore high-altitude pressure suits. At these higher altitudes, the Streak Eagle was 10 seconds faster to altitude than the Apollo Saturn Rocket moon shots. The 15,000 meter record of 77.02 seconds (by a margin of 37.5 seconds) was flown on a profile similar to the lower record flights. The last three record flights had similar profiles – a level acceleration at just above ground level, followed by a constant G pull up to a vertical climb, and then an "Immelmann turn," an aerobatic maneuver that results in level flight in the opposite direction at a higher altitude, followed by an acceleration to the target Mach number, then a constant G pull up to the optimum climb angle. Incredibly, on the 30,000 meter record attempt, at the time of the Immelmann, the aircraft was about 21 miles down-range and through Mach 2 speed - only two minutes after take-off. On that flight, a promotional U.S. Air Force video reported that the "Streak Eagle" was on a "nearly ballistic flight path."
The 20,000 meter record of 122.94 seconds (by a margin of 46.8 seconds) was set on Jan. 19 and the 25,000 meter mark of 161.02 seconds (by a margin of 31.6 seconds) was set on Jan. 26. The historic 30,000 meter record of 207.80 seconds (by a margin of 36.1 seconds) was set on Feb. 1. The first attempt at 30,000 meters, however, was unsuccessful. "We analyzed that we needed a cold day to break the record," Enos said, "and that if we got one, we would do so not by a little but by a lot. The first attempt came on a warm day and we just missed it. We needed a seven degree centigrade cold day at altitude, and we waited for it. And when we got it, we crushed the record."
The 30,000 meter flight profile was the most difficult one. Acceleration was made to Mach 2.2 and the optimum climb angle was approximately 55 degrees. The maximum altitude reached was approximately 103,000 feet as the aircraft "coasted" above the record. The engines were flamed out at this altitude, but were restarted inflight. This was important because had they not restarted, the recovery was to "dead stick" the plane back to the airport in Fargo.
Enos noted that, after the last flight, "We were all full of joy, but also a bit sad because we realized that we would, in all probability, never in our careers again experience something that was as technically challenging, dangerous, the center of such focus and as much fun. I will always be grateful for the opportunity given me by Pratt, at just 27 years old, to be given such a challenge and such responsibility. Specifically, I am grateful to Ed Ford, Paul Wilson, Jack Hill, Tom Wiegel and others for their help and support." [Note: Enos rose in the company to become Pratt & Whitney's vice president of Operational Military Engines, before his retirement from the Commercial side of the business.]
The records would not stand forever. In 1986, the Soviet's Sukhoi P-42 fighter jet, a prototype of the Su-27 "Flanker," would erase the "Streak Eagle's" marks. Yet while the "Time to Climb" records might not live on, the F-15 and its F100 engine are as relevant today as they were 40 years ago.
"When we think of our current customers, they operate in some of the most dangerous areas of the world," said Jeff Zotti, Pratt & Whitney's director of F100/J52/TF33 Programs. "Records are great, but the key is that our F100 engine helps defend freedom all around the world, every day. That's what's really important."
Pratt & Whitney has produced more than 7,000 F100s (more than 4,000 of them still in service today) and supports the air forces of 23 different countries. Five customers operate F100-powered F15s, including the U.S. Air Force, Israel, Japan, Saudi Arabia and South Korea.The U.S. Air Force has said that it plans on operating its F100-powered F-15 fleet until at least 2045, and international customers are looking to operate even longer.
"Today's F100-229 model has a more impressive thrust-to-weight ratio than earlier engines and is much more reliable, saving time, money and improving readiness," Zotti added. "It also has a tremendous safety record. As long as the F100 remains in service we'll continue to look at ways to improve performance and quality, and reduce cost."
Zotti noted that today's F100-229 generates more than 29,000 pounds of thrust. "Today's F100 would blow through the records of 40 years ago," he said, with pride.