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The Joy of High Tech


Rodford Edmiston

Being the occasionally interesting ramblings of a major-league technophile.

Please note that while I am an engineer (BSCE) and do my research, I am not a professional in this field. Do not take anything here as gospel; check the facts I give. And if you find a mistake, please let me know about it.

Credit Where it is Due

Part 2: Starfighter

Y'know, sometimes we humans manage to do something right. Many of the examples come from aviation. That's partly because in aviation, if you get something wrong the results tend to be fatal. Some of the most remarkable aircraft - the "most right" - of all time were members of what came to be known as the Century Series. The majority of these fighter planes were huge, actually serving as interceptors, attack planes and bombers, but there was one which stood apart. One which is still in use today, continuing to serve its original purpose well into the 21st Century. A plane which one technical writer stated can "still show its heels to most front-line fighters."

In the early Fifties jet fighters were rapidly growing larger and heavier. Many rivaled WW II light and medium bombers in weight and carrying capacity. There were many reasons for this, some technical, some tactical, some strategic... and some psychological. For instance, the Fifties was the era of the "bigger is better" mindset. As mentioned above, though, there were legitimate technical reasons for the size increases. Jet engines of the era worked best in a certain size range, and the jet aircraft built then were so expensive that in order to get the taxpayer's money's worth the bean counters decided that in addition to fighting the planes should also perform other duties. Of course, the extra equipment needed for these duties made the fighters even larger and more expensive. Then there was the concept of the fighter as missile platform.

Technical optimists felt that (then-) modern missile technology had made the gun-equipped fighter obsolete, and that bullets could be omitted from consideration. Later experience proved this to be very untrue. Even today this goal has not quite been reached, though modern missiles are much more reliable and capable than those of the Fifties and Sixties. While the classic fighter dogfights where guns would be needed have just about been eliminated, guns are still useful for strafing. And if you do get into a dogfight... But in this period it was felt that fighter aircraft should no longer have guns; any strafing could be done by dedicated ground attack aircraft. Instead, fighters should carry lots of missiles and big radar sets for detecting the enemy, as well as lots of fuel to get to where they could launch the missiles. And since they were already big enough, add the capacity to carry large bombs, too. (The F-105 in fact had an internal bomb bay, which was almost never held bombs in service.)

Some companies bucked the trend. One of them was Lockheed. Company personnel - including Clarence "Kelly" Johnson - talked with fighter pilots (many of them veterans of Korea, where the US had been unpleasantly surprised by the MiG-15) and asked them what they wanted. To the astonishment of no-one except the Air Force brass, these men stated they wanted something fast, agile and equipped with a good punch (which meant a gun in addition to effective missiles). Adding to the motivation at Lockheed for moving away from the "bigger is better" approach favored by the Pentagon was the sour taste left by the failure of the company's huge XF-90, a mammoth plane designed to fit official requirements. So while other design teams were planning such monsters as the F-105 Thunderchief (as heavy as a WW II light bomber and actually intended to deliver a single nuclear weapon dropped from an internal bomb bay, mentioned above) Johnson and his team sat down and started with a clean sheet of paper and the pilots' requirements.

In November of 1952 Lockheed submitted an unsolicited proposal for a new, lightweight fighter. Although the Air Force had no official requirement for such a plane they had enough faith in Lockheed and Johnson to issue a General Operational Requirement to replace the aging F-100 Super Sabre. Johnson and his crew set eagerly to work. Johnson's team studied many options and variations. Finally, they picked a concept - the minimum airframe to hold the engine, pilot, weapons and avionics, plus enough fuel to get the plane there and back. Then they decided on the upcoming J79 for the engine. And what an engine that was (and still is)! The team wanted plenty of thrust margin, in case the J79 didn't live up to expectations, and for the inevitable growth in airframe weight. As the A-10 was later wrapped around its Great Honking Gun, the new plane was wrapped around a Great Honking Engine. Everything else about the airframe was small, especially the wings. After some final adjustments, the designers realized they had a winner. On paper, at least.

The gun chosen was the then-new Vulcan. This is a 20mm, multiple-barrel rotary weapon, basically a motor-driven Gattling gun firing a small cannon round. This had such a high rate of fire it could put more rounds on target in the same interval than the multiple .50 caliber machine guns used by US planes in the Second World War and Korea. Even better, those rounds were not only larger but carried an explosive charge.

Another departure from the norm came with those thin, tiny wings. Supersonic wind tunnel data showed that swept wings made transonic flight easier than the nearly straight, tapered wings then in use on prop-driven and most early jet craft, and delta wings were better yet. Most companies were going with a delta-wing configuration. However, a delta wing has a lot of supersonic drag, and the new plane was intended to operate supersonically, beyond the transonic realm where deltas were best. The same data also showed that a very thin, straight wing had most of the advantages of deltas, plus some others, such as low supersonic drag. (The Bell X-1, for example, had thin, straight wings.) Also, Lockheed had plenty of experience with this configuration, having used it successfully on the X-7 ramjet research vehicles, which had thin, straight, trapezoidal wings. (Note that a target drone developed from the X-7 had such extraordinary performance that it was almost impossible for the plane/missile combinations of the day to shoot down.) Many long and heated discussions, accompanied by research and testing, went into the exact design of the wings and their fit to the aircraft as a whole. Part of the difficulty was making sure takeoff and landing speed were not excessive, which necessitated adding blown flaps and other lift-improving devices. After a rather short and very hectic design and construction period, two prototypes flew. These prototypes proceeded to set several speed and time-to-climb records, even though they were under-powered with a J65 engine. (With the afterburning version of the J65 the second XF-104 prototype reached Mach 1.79 in level flight.) Using the data from these planes the design was modified (primarily by being enlarged) and several YF-104A service trial aircraft were produced.

There were many criticisms of the design, some of them involving the downward-firing ejection seat. Because the F-104 had a t-tail with a high-mounted horizontal section the designers felt that the upward ejection seats of the Fifties would not be able to get the pilot clear in all flight modes. So the unhappy solution of a downward ejection seat was used. This meant that if a pilot had an emergency at low altitude he had to either ride the plane in or try to roll upside down and eject. Neither of these were satisfactory solutions, and Starfighter pilots were an especially tense lot during takeoffs and landings until later models switched to an improved, upward-firing ejection seat. (Note that other t-tail fighters from this era also faced this problem.)

Switching to the present for a moment, there have been many interesting claims made about the F-22 Raptor (or Rapier, according to some sources). Unfortunately, in their enthusiasm the new fighter's supporters have said some things which just aren't true. The F-22 is capable of maintaining level flight at Mach 1+ in what is known as supercruise mode; that is, flying supersonic without using a fuel-hungry afterburner. (Maximum supercruise speed for the F-22 is listed by some sources as Mach 1.53. It is most likely less than that, perhaps significantly less.) While most supersonic planes designed before the F-22 were built to exceed the speed of sound for short dashes only (bombers and attack craft to get in and out, and fighters to close or escape, with some supersonic dogfighting) some could do better. The term itself came around long after the F-104 (and a few other aircraft) did it.

Many of the Century Series fighters could supercruise, though most of those just barely. (As a rule of thumb, any plane which can exceed Mach 2 with afterburner can probably exceed Mach 1 without.) Starfighters with the J79-19 engine can - at altitude - maintain about Mach 1.1 in level flight in military power (maximum throttle without afterburner). This isn't surprising when you realize that the J79 engine was vastly improved during the long production lifetime of the F-104, with later versions producing nearly as much thrust without afterburner as early models did with. (In his comments on the F-22, retired Colonel Everest Riccioni (one of three legendary "Fighter Mafia" mavericks who forced the Pentagon to produce the F-16, to improve U.S. air superiority, who flew 55 different types of military aircraft, and worked in the defense industry for 17 years managing aircraft programs, including the B-2 bomber) compared it unfavorably to the F-104-19 in several categories, including supercruise range.)

To give an idea of how far a Starfighter could go at supersonic speeds, an F-104A with no external stores could take off, climb to 20,000 meters, accelerate to Mach 2 and fly for fifteen minutes, and still have plenty of reserve for descent and landing. (Just be sure to bring your pressure suit along.) Adding wingtip tanks increased the fuel available with little effect on top speed, in spite of the drag they created. (Tanks and missiles on the wingtips also helped the plane turn tighter, since they acted as endplates on those stubby wings.) Later models had improved J79 engines with better fuel economy, plus increased internal tankage, so they could cruise supersonic for even longer. They also had more military (dry, or non-afterburning) thrust, making the Zipper’s supercruise capability less marginal. Some F-104A aircraft were later modified to take the J79-19 engine, originally developed for the F-104S. Since the A was the slickest and lightest production version of the plane it had spectacular climb and acceleration with the new engine.

The top speed of most fighters - even today - is limited by thrust (the F-16 has a higher thrust-to-weight ratio than the Starfighter, but it also has a huge delta wing which is optimized for maneuvering and generating lift to carry large amounts of external stores, not for supersonic flight). The F-104 is generally restricted by heat in the compressor section of the engine and certain parts of the airframe. Early Starfighters could not exceed Mach 2.2 without potentially damaging the engine; on later models with the -19 engine this was increased to Mach 2.3. The canopy limit is around Mach 2.6. The airframe on late models is stable out to Mach 2.8. As top speed is approached in the F-104 the pilot must throttle back to keep from exceeding the safe limits, unlike almost any other plane. One US Air Force pilot wrote that in his experience the F-104 was the only plane he had ever flown where even the squadron dog could exceed all the red lines. For comparison, the normal top speed of the F-15 is Mach 2.3, with a time-limited pursuit mode of Mach 2.6. It can do this carrying some missiles, but not with drop tanks. (Later models of the Eagle with improved engines may be able to.)

Keep in mind that the low-altitude record for flight speed was set in the Seventies with a slightly modified Starfighter. Which was owned by a civilian group, Darryl Greenameyer's Red Baron racing team. They went to the high desert and set the record at 988 mph, averaged from four passes, each at a height above ground level of less than a hundred meters. The record requires that this be done without landing or exceeding an altitude of 300 meters between passes. On one set of passes the plane averaged just over 1000 mph, but due to a fault in the timing equipment this is not official. Before this, military pilots of two-seat models given the task of taking some VIP for a ride liked to return to base on the deck and casually mention that they were exceeding the official world low altitude speed record. The F-104's thin wings not only have low drag, they are less affected by turbulence. It is the only plane around with the combination of endurance, handling and speed for setting such a record.

You will read in some references that the F-104 is not very maneuverable. Well, down low and going slow, it isn't. However, high and fast - which was how it was designed to operate - it is just about untouchable. The secret is energy maneuvering, repeatedly trading speed for altitude and vice versa. Pilots of other aircraft flying practice dogfights against a Starfighter get left behind when their opponent makes a vertical maneuver they can't match. While they are trying to relocate the tiny plane, it suddenly dives on them from behind. Repeated slashing maneuvers leave opponents riddled, while providing little opportunity for retaliation. (Members of one squadron of F-105 pilots participating in dissimilar aircraft exercises complained that the only reason they came in second was that the F-104s kept going up and down, instead of turning hard like real airplanes do. One F-8 pilot in another dissimilar aircraft exercise chased down what he thought was a lone F-4 - which also used the J-79 engine - only to see an F-104 break off from close formation, going into a vertical climb. He lost that match.)

The plane is no slouch at turning, either, given the lift-enhancing mechanisms built into that small wing (including flaps which are deployable up to 540 knots under all conditions; that's above Mach 1 at high altitude). In some parts of its envelope the F-104 can actually turn inside the F-16. Of course, that statement is hardly fair, since its envelope is larger than the Falcon's. As for combat range, in Vietnam, when the F-105 Thunderchiefs flew low-level, deep penetration bombing missions, the Starfighter was the favored escort. The F-4 Phantoms could not keep up with the Thuds if they carried enough fuel for the mission, and the Thud pilots were not about to slow down. Also, as was true all during the War, when the Starfighters took off, the MiGs landed. The F-104 had a very poor kill record in 'Nam for the simple reason that the MiGs refused to engage it. Because, unlike most US fighters of the time, it was a pure fighter, not burdened with the need to drop bombs, and the Russians knew this. There are certain advantages to specialization...

The F-104 is optimized for supersonic flight. In fact, the inlets don't even start working right until the airspeed gets above Mach 1.4, at which point pilots describe the plane as "going into passing gear." Also, above Mach 1 those tiny wings work very well, indeed. The plane is so supersonically smooth that pilots have reported passing Mach 1 by accident, and not even realizing it until they checked their instruments.

The Starfighter is not an interceptor; it was intended from the beginning as a point-defense fighter, a plane designed to deal with enemy fighters, bombers and attack craft trying to destroy an important facility. Yes, the plane is hard to fly, but a pilot who works at learning how can chase down or get away from almost anything else in the sky. It validated the concept of the lightweight jet fighter, long before the F-16.

So what did the Air Force brass tell Lockheed, after the plane had proven itself to be everything the company claimed? To make it carry bombs. Big ones, including the heavy nuclear weapons of the day.

Does it seem to you that someone missed the point?

Well, Johnson did it. His team even devised a way for the F-104 to carry a single large nuclear weapon under the belly. The thing nearly scraped the ground during taxiing, but the plane could deliver it as asked. The US Air Force unenthusiastically ordered a handful of Starfighters. Fortunately, it was also cleared for export. Many nations were interested – West Germany especially.

Unfortunately, the Bundes Rebublik Deutschland (the Federal German Republic, ie the West German government) air force promptly crashed a large number of them. Many claimed this was because the plane was inherently dangerous. As it turned out, the problem with the German Starfighters wasn't the planes but improper pilot training. (During this same period, Spain crashed none of their Starfighters. Flying similar missions in similar conditions. Most other nations acquiring the F-104 also had a lower accident rate than that of West Germany.) Turns out the German pilots had been trained in the US high desert, with clear skies and lots of room. Once the German instruction regimen was changed to something appropriate for central Europe the safety record for the F-104 improved to something typical for fighters of the day. However, by this time the US military had already decided that the F-104 was not for it, that real fighters were big and heavy and carried bombs. (Though some A models were brought back into service and outfitted with the J79-19 engine later, as mentioned above, due to Vietnam sucking up so many military aviation resources.) This attitude would remain until the Lightweight Fighter concept became popular a few years later (the result of campaigning by what came to be known as the Fighter Mafia), eventually resulting in the adoption of the F-16.

The Starfighter was still popular in many other countries - including Japan and Italy - though, and remained in production for several more years. In fact, Italy flew it as a front-line aircraft until 2004, having worked with Lockheed to develop a new model, the F-104S. This model, modified multiple times to eventually produce the F-104S-ASA-M, still shone as a fighter until the day its unhappy pilots had to turn their planes in. (You can trust the Italians to recognize and appreciate a sports car, even if it does have wings.) It was replaced by rented F-16s until the Eurofighter is operational.

Most countries which flew the F-104 have since declared it surplus. Not because it can't do the job, but usually because they bought into multinational production programs for other aircraft. (Such as the Eurofighter, mentioned above.) Also, parts were getting hard to come by. Italy made parts for its F-104S, but this plane is not completely compatible with the older models. However, while enough parts to keep an entire air force's supply of older Starfighters running are hard to find, scrounging what is needed for individual aircraft is pretty easy. Especially if the planes are demilitarized.

For instance, there is a private company which does flight testing for NASA, such as evaluating improved Shuttle thermal tiles. They have an F-104B, the first two-seat version. Without armor, weapons and heavy military avionics, once the plane is below half its internal fuel it has a thrust-to-weight of better than 1:1. The pilot says he loves the reaction he gets when the control tower advises other pilots approaching the airport where the plane is based that there is a F-104 in the pattern behind them.

There's a Florida-based airshow demonstration team which flies two ex-Canadian Starfighters. One airshow where they appeared was hosted by a US Air Force F-16 base. An aviation photographer saw one of the base pilots watching the team make a low-altitude, high-speed pass. The young man was obviously impressed. The photographer asked him how it felt, knowing the fastest planes on the base were owned by civilians. There is no record of an answer.

A pilot for this team mentioned doing a Mach 0.9 pass in front of the grandstand (at another airshow) and pulling up into a vertical climb. By the time he reached the top of the airshow box at 6000 meters he had lost only a few knots and the speed of sound was dropping with the decrease in air pressure. He checked his manuals later and doesn't think the plane would have gone supersonic if he'd kept climbing straight up. But he sure would have liked to try...

Even today, the performance of the F-104 seems almost mythical. Even early models could fly at altitudes far above the listed service ceiling. An ex-US Air Force pilot reports that he and his wingman, flying F-104A aircraft refitted with the -19 engine, could maintain level flight at Mach 2 and 22 kilometers altitude, if the air temperature were lower than usual. They surprised a U-2 pilot during a practice intercept doing that. The U-2 was flying at a bit above 21 kilometers, and the F-104s came in from above. The F-104 pilot stated that the U-2 pilot's comments on this were the only time he ever heard one of the Dragon Ladies break radio silence. (Best lift-to-drag speed for a clean F-104 is around 273 KEAS (knots equivalent air speed) and wingtip Sidewinders wouldn't affect this much. At 21 kilometers, on an average day, that works out to just about exactly Mach 2.)

Note that while Starfighter is the official name of the F-104, most of its pilots call it the Zipper. Because it... well, you get the idea.

Some critics say the F-104 doesn't have enough range. Maximum range, using 4 external tanks - which are dropped when empty - and best range cruise of Mach 0.9 is around 2400 km (planes with the -19 engine can do better). With the same 4 tanks, climbing to 21 km and accelerating to Mach 2, the plane can cover nearly 2300 km. With 1300 of that at Mach 2. While the plane's range isn't impressive, how fast it can cover that distance is. Which was the intent all along.

By the way, don't get the wrong impression about the comparison I made above between the F-104 and the F-22. The latter plane is an improvement over the Starfighter in just about every way. But then, it was designed some 40 years later.

This material is Copyright 2005 Rodford Edmiston Smith. Those wishing to reprint this material can contact the author at: stickmaker@usa.net