Sounding off about the Zipper

Walt BJ, Zipper pilot, ret

F-104 - you got that right. I spent a year in Greenland and the knowledge my first two choices for a follow-on assignment were the two 104 squadrons kept my spirits up through that tour. 3rd choice was the 106. I got my first one!

I feel like sounding off about the Zipper, so hang on.

So few people really know what that bird could do, and how easy it was to keep in commission. We always had payday afternoon off and very seldom ever flew Saturdays to get the time in. Engine change done in about 2 hours. All the electronics including the radar T/R (Transmit/Receive) [1] package could be changed in minutes. The radar itself was a simple set: range-only, limited to 20 miles by design. It worked about 99.95% of the time. The gunsight was very accurate. Parts were the only thing that could ground a bird for more than a day. It had VOR, TACAN and ILS and was a very good instrument aircraft. Also very good in formation flying. Note: overlapping the wings got you very close - the wing panel from fuselage fillet to missile rail was just about 75". Wing loading was about 145 lb/ sqft [2] but nevertheless with the boundary layer control bleed air in Land Flaps she could be brought in at 150 and touched down about 140. (No-crosswind; about 135) but the ailerons were pretty weak that slow. Doing that and using the drag chute, you could easily stop in 3000 feet after touchdown without punishing the brakes.

I spoke of old and new engines. The F-104A was the first aircraft in service with the GE J79-3B engine. The Zipper had a pretty poor record until GE cured two serious bugs. One was an oil leak would let the engine exhaust nozzle go wide open. Then at full power you didn't have enough thrust to maintain level flight. When you got too low you had to get out and walk. The other was the engine inlet vanes which would crank wide open if its control failed. Now if you reduced power below say 90% she'd start stalling. No more thrust. They got that fixed after a year or so. Meanwhile about 50 or so 104s were lost. The -3B engine had 15,000 and 9800 pounds of thrust in afterburner or in military (max without AB). The -19 engine had 18900/12500 pounds, same conditions. It also had a more efficient nozzle and a higher compression ratio. Since a 104 weighs about 14,000 pounds empty and just over 20,000 pounds sitting on alert (Pilot, about 5,500 pounds fuel, two missiles, 750 rounds of ammo) you can see that new engine gave it sparkling performance.

The Lockheed C-2 ejection seat was capable of a safe ejection once over 200 Kts on takeoff (which was pretty dang quick - 3000 feet give or take a couple hundred.) By the way that seat also protected you if you had to eject at high IAS. Cables pulled your feet in and deployed webbing restrained your elbows and arms. A couple seconds later the 'butt snapper' kicked you out of the seat and if your zero-delay lanyard was hooked to the D-ring it deployed the chute for you right then.

Brake release to .97 Mach was 43 seconds at Sea Level and 85 Fahrenheit in our re-engined birds. 45,000 feet in 90 seconds after brake release - I did it once. .97 Mach in military power on the deck, about 1.25 in burner, again on the deck. Would accelerate past 1.0 Mach at 25,000 in military - no AB needed. Did that, too. Cruised at 2.0 Mach (310 KIAS) at 73,000 feet burning 100 pounds per minute. ‘BT, DT' [3]. Using T/O flap setting would out-corner the F-4. Plus that flap setting limit was 550 KIAS/1.8 Mach (whichever you hit first). We used T/O flaps for tight turns; then on relaxing stick to zero-G A/B on and flaps back up to regain energy back - quickly!

Red Lines - 710 KIAS, 2.0 Mach. 100 degrees Centigrade CIT, and a SLOW light that comes on when the generator cooling air reaches 120° Celsius. All, repeat ALL are artificial and serve as the manufacturer's statement that if you go faster and something bad happens don't complain to them. 710 KIAS was for compressor case strength, 2.0 Mach was for the directional stability damping coefficient dropping below 0.003, the USAF limits; 100° Celsius for aluminum skin. Every single one of our aircraft, single and two-seaters, would far exceed every one of those limits. The old J79-3B engine (15,000 pounds in burner) when new would take the bird out to 2.36 Mach; the newer -19 engine (18900 pounds in AB) to the far side of 2.5 Mach. Both are too fast for an all-aluminum airplane. I was somewhat handicapped by being a husband to a fine woman and father of two great daughters and also the custodian of a damn fine dog. I only saw about 750 on the deck and 2.2 up high. Two guys in my flight saw 2.5 Mach at 50,000, another good friend and ferocious fighter pilot was getting into some F-106s and saw 825 KIAS at 25,000 feet on his first pass.

Beauty - in flight - wow! I was going through the transition phase and about ride 6 or so I had to take it out to 1.7 Mach. Well. I'd been out to 1.3 Mach in the Deuce but - the old -3B engine had a 'T2 reset' to cope with the temperature change as the CIT rose - it would suddenly push up the revs about 3%. That is about 10% more thrust and you can definitely feel it as a solid push. Also at that speed the directional stability is degrading and she begins to wag her tail slightly - a 1/2 second oscillation. Like she's telling you how fast she's going. Neat! Anyway there I was going a hell of a lot faster than I'd ever gone before, knowing there was even more speed on tap, and - I was also flying as a target for 4 of the outfit. All of a sudden I hear them all calling "MA" (Mission Accomplished - weenie-speak for Kill) ) to the GCI controller and then ZIP x 4 - those hightailed stub wing beauties, bunched up tight, blew right past me about a hundred feet out on each side.

Later on I went out to Mach 2.0 as part of the check-out – as #4 while we all intercepted a 1.7 Mach target. We got him, went out a couple more miles and Lead said Zoom Now! Of course we were wearing P-suits but it was a thrill arcing up over 75,000 feet in spread formation!

The F-104 had none of the newer control system kluges [4] that compensated for airspeed changes, what you felt was what you got. Thus at slow speeds - 300 on down - she took a lot of stick motion to maneuver about. But at 450 she felt great and up at 700 she still felt great. She was not too sensitive, jumpy, even over 750 right down at 50 feet AGL. She was also a good strafing bird; at 450-550 you could move the pipper a half a mil or so.

With tiptanks we could go from Homestead direct Kelly (to refuel) then direct Palmdale, IFR. The 104s didn't have in-flight refueling (except a weird stuck-on affair with the probe hanging out all the time) but you could take the wings off (5 bolts each, take off the aft section (4 bolts) stuff the whole setup in a 141 cargo plane with a bunch of spare parts, pilot, crew chiefs, and fly that anywhere in the world. Take about 3 hours to disassemble and then 3 more to reassemble.

We regularly made hot scrambles in 3 minutes. My first two years at Homestead we were averaging two hot scrambles a day. (First man to the runway led - average pilot flying time was about 2400 hours - we were screened for the job.)

A word about the Gatling gun- the dispersion was 3 mils - all the bullets inside a 3 foot circle at 1000 feet; that also means a 9 foot circle at 1000 yards. 67 rounds a second, 4000 rounds a minute. There were 750 rounds in the ammo cans. The gun was driven by a 15 horse electric motor, thus the 'slow' rate of fire. It had a radar-ranging gunsight and the system was very accurate. Some unfamiliar with the gun claim it is slow getting up to speed. My experiences on the firing-in butts say no. There was one bullet up and left - the first one out the spout. All the others were randomly spotted inside that 3 foot circle. (So was that first one, it was just outside the perimeter of the others. It was neat firing it on the ground. The bird was jacked level and chained down - recoil force was about 3000 pounds. 50 rounds went out so fast it was all over before the first empty case dropped out the belly. BRRRRMP!

BTW we scheduled and flew 36 air to air gunnery sorties a week, so we got and stayed proficient. Our target was the "Dart", towed by another 104 on a 1500 feet cable. This thing was about 12 feet long, 5 feet wide at the tail and looked just like a pair of grade-school paper dart gliders glued belly to belly, giving a + cross section. You focused your eyes on it, flew the airplane to bring the sight pipper up onto the target, tracked the dart smoothly and shot a half-second burst. The key was keeping your eyes on the dart and never looking at the pipper itself; that led to chasing it by pumping the stick which about 95% of the time guaranteed a miss.

BTW the bloody F-4D/E took about 120 miles to get from .9 to 2.0 Mach, we did it every engine change. The old -3B engine was about the same, maybe 20 miles shorter, both taking about 4 minutes plus. The -19 engined bird took about 27 miles, about 1'45", and burned 1000 pounds of fuel doing it. I zoomed an F-4D once starting at the end of that Mach 2.0 check run - 67,000 feet tops. Boo hoo. The -19 bird went off the top of the altimeter still going up at a great rate. That 3-needle altimeter has a mechanical stop at 86,000. GCI height finders routinely read out 95,000 plus when zoomed without regard to minimum IAS. (I used between 125 and 175 and zero-G over the top, being a trifle cautious by nature.)

People knocked the Zipper for its short range. Very few people knew that with four external tanks the 104 could fly a low-low-low mission about half again as far as the F-4. That was the NATO F-104G's mission in Europe - and it carried one bomb along with the fuel tanks. We were intercept-only with no bomb or rocket capability. We scheduled 1:20 hour for the old engined-birds minus external tanks. That went up to 1:30 hour with the new and more efficient engine. That equates to 8 1/2 miles a minute cruise giving about 700 miles for the old-engined birds; 800 for the -19 birds. Considering it was designed for a point-defense interceptor using lessons learned in the Korean War - well, it met that criterion just fine. Another point was that it was not an all-weather interceptor. True, but then the Earth is not all that cloudy; about 85% of time (so I heard) the weather would be adequate for a 104 intercept. Radar could lead you to the target; if you had at least half-mile visibility you could fire Sidewinders at him. Using radar plus the simple infra-red sight you could shoot at him once in gun range.

What else? The only bird with a faster roll rate was I believe the T-38/F-5 at about 470/sec. The Zipper - 420 or so, for one roll. Too many rolls and you would get into roll-yaw coupling - not good. To use full aileron at 400 KIAS you had to grab the underside of the canopy rail with your left hand to keep yourself from being thrown to one side by inertia and probably taking out some aileron as you inadvertently dragged the stick towards neutral, To roll out on a point after full stick deflection you had to lead the rollout about 45 degrees.

There was a slight but definite burble as you got close to a stall. Get too ham-handed here and she would pitch up - if you managed to ignore first the stick shaker and next the stick kicker which would push the stick forward to reduce the AOA. Note - if the auto pitch control (APC) system was inoperative, it was pretty easy to ignore that little burble in the heat of simulated combat. I did - once. Snap reaction of jamming the stick into the radar hood brought the nose back down smartly. Engine gyro force kicks the nose right as she goes up; back left when recovering smartly. Note two - there is zero warning supersonic - no burble whatever. Oh, and it flames out as you pitch up - duct stall. But she lights up immediately once you get the angle of attack to zero and hit the dual ignition switches.

Note 3; the APC system can be negated by trimming way nose high - the kicker is then reduced to tapping the stick. The shaker is shaking away but ineffectively. As the AOA increases you can feel the aero center moving forward nearer the CG and pretty soon you are pushing the stick forward of neutral to keep the AOA under control. (I think the broad shoulders of the intakes are also generating lift at this high AOA. This is essentially a useless maneuver as almost every other airplane in the world save maybe the 101 can out-slow you.

We flew in pairs, always. We practiced the USN Double-Attack tactics, otherwise known as Loose Deuce. Basically it is a system of alternate attacks as the tactical lead switches back and forth depending on what the opposition is doing. Looking at it historically, it's Fluid Four without the wingmen - you keep each other clear and as one attacks and forces the opponent to react the other guy is repositioning to become the attacker as the first guy repositions. We usually repositioned straight up, bellying up through 40-50 thousand if needed as our attack speed was usually well over 550 KIAS - as high as 675-700 fighting F-106s and Crusaders. (the -19 engine afforded amazingly very quick zero-G acceleration.) We also practiced high angle off gunnery as our radar sight was accurate and a little mod I got the radar troops to kluge up gave us instant lock-ons. We could adjust the lock-on sensitivity in flight - up until it locked onto air, back it off until it wouldn't, then it'd give an instant lock-on as you got your nose on the bogey. It was almost impossible to set it correctly on the ground because of clutter.

There were at that time about 125 Mig-21s down in Cuba. We never saw one. We never worried about them; we were confident our airplane, skills, and training gave us the edge. We had a good clear ROE; never had to use it. Everything I intercepted was friendly. One funny thing - any intercept we made south of latitude 24 was head-on, supersonic. Lead (eyeball) would pass about 500 feet below the bogey; #2 would lag about 4 miles as the shooter if needed. If the bogey had been a bandit (hostile) Lead would have pitched straight up to reposition while 2 maneuvered to engage the bandit.

Well, I've become a genuine old coot talking about the good old days - damn, they were GOOD! It's all your fault, you got me thinking about my favorite airplane.

Walt BJ
weapons training officer in the 102 and the 104


[1] What our radar techs did was run wiring from the on-target bias control which controls sensitivity of radar lack-on up to the pressure suit face mask heat control on the right side of the cockpit. That let the pilot adjust the lock-on sensitivity precisely while airborne, something that was just about impossible on the ground. We had done the same thing to our F-102s years earlier so we could operate close to the ground where too much sensitivity had you locking onto everything on the ground. By reducing the sensitivity enough we could fly lower and look up and lock on to a target flying at 300 AGL. Yes, we were lower.

[2] Penalties were to be paid for its role transformation, wing loading increasing from the 96 lb/sq ft of the clean F-104A interceptor to no less than 158 lb/ sq ft for the ultimate multi-role derivative, the F-104S, in fully laden condition.

[3] 'BT, DT' - short for 'Been there, done that'

[4] 'Kluges' are clever tricks (from the German word: klug) - the slang came from early work in radar when the original design wasn't good enough.