First, a war story: (I must make the following disclaimer: This story contains very vulgar language…er…um…that is, it would were it not for my own sense of decorum and yahoo’s requirement that we keep it to at worst a PG rating. I shall therefor substitute the dreaded “F” word with the word “eff”.)
It had to have been in late 1979, my bird- 68-116- had landed IFE (In Flight Emergency) with one very scary hydraulic problem. Serious enough for the aircrew to have to use the emergency landing gear system which injected 3,000psi of air pressure into the landing gear system, effectively “blowing” the gear down for landing.
It doesn’t take a rocket scientist to figure that blowing air through a hydraulic system ain’t good on many levels. First, you have to purge the entire system, fix the inevitable leaks, replace all the blown seals, valves, etc., wash out all that hydraulic fluid that filled the main landing gear well (the stuff’s corrosive as hell, and just as sticky as it dries), replace accumulators, actuators…yeah, it’s a real nightmare.
Anyway, after Wing Safety released it from impound (after the investigation), we started the process. Hydraulic Specialists worked hard day and night for several days and nights to get THE COWTOWN TERROR back in service.
With everything repaired, replaced and put back together it was time to “ops check” the system to make sure it would work as advertised before an “FCF” (Functional Check Flight) could be flown and the aircraft deemed airworthy again.
So, here we are, in hangar 121, with the airplane up on jacks, hooked up to various types of equipment to provide electrical power, cooling air for the avionics, and hydraulic power. This last piece of equipment was called an MJ-01 Hydraulic Test Stand, or Mule. So called because they were notorious for various types of tantrums. Anyway, here I am, in the left seat, a hydraulics guy in the right. My job was to cycle the gear up and down and move the flight controls around while hydraulics troops monitored everything. If all went well, an FCF would be scheduled. If not….back to the ol’ drawing board.
The guy running the whole show was a buddy of mine, Ssgt Bill Champion of Tyler, Tx.a Hydraulic System Specialist with the 27th EMS (Equipment Maintenance Squadron). We powered up, got hydraulic pressure on, and started checking this thing out. Right in the big middle of it all, I feel a slight shudder through the airframe. “Uh-oh,” I said, thinking one of the jacks holding the plane up was failing. We were wheels up at the time.
Then I hear through the headset, “EFF!!”
“Champ, what’s going on?” I asked
“EFF! This effin’ effer’s effin’ well effed!” He says. I was awestruck.
The problem was simple: The mule had backfired, sent a surge of hydraulic pressure through the system and crapped out completely.
Well, the mule was replaced, all checked well, she flew her FCF next day and got a clean bill of health.
My buddy, Champ got an award for the most effective use of the “F-bomb.”
True story, swear-to-God!
The Air Force Soldiers on…
With the Navy now out of the TFX program, the Air Force was all alone in 1968 with what can best be described as a shaky program. SecDef Robert McNamara’s imposition of all those restrictions and requirements for a dual-service aircraft had the project seriously hamstrung and speculation was rampant as to it’s survival.
Considering however, the amount of taxpayer dollars already expended on the F-111, I guess the Air Force figured they better make good on the investment. So, they set themselves to resolving the many issues that are inevitably raised when developing new technologies and pushing the envelope of existing technologies.
Among the first of these issues were the engine problems mentioned in part 1. The Pratt and Whitney TF30 engines were the first turbofan engines cleared for supersonic flight. Up until the advent of the TFX program, everything flew with turbojet engines. While the basic principle of jet propulsion applies to both engine types, there are differences between the two. Each has advantages and disadvantages. The most obvious of these differences is the size and complexity of the turbofan vs the turbojet, a much simpler design tried and true by the early 1960’s. The turbofan, by contrast is a much larger diameter engine with a maze of ducting, turbine shafts, bearings, pumps, and you-name-it-it’s-there moving parts. It can be a very labor intensive engine.
Of course, the TF30 is also far more fuel efficient than its turbojet contemporary, the General Electric J79. Anybody that has ever watched an F-4 Phantom II or early B-52 (both turbojet powered) probably noticed the huge trail of black smoke these planes left behind them. That’s caused by burning engine oil and incomplete fuel combustion, noticeably absent or greatly minimized in turbofans. I’ve worked on both Aardvarks and Phantoms, and I don’t recall the Aardvark using anywhere near as much engine oil as the F-4.
The problems encountered in early test flights, violent compressor stalls and surging, revolved around the design of the intakes- roughly the shape of a large pie slice (about 1/4 of the pie). What happened is this: at certain angles of attack, the airflow into the engine becomes restricted or disrupted. Vortices (itty-bitty tornadoes) form in the intakes and cause all kinds of hell with airflow into the engine, either too much air is introduced at unstable pressures or not enough air gets in. With one you get a compressor stall, which is a loud, violent blowout, while with the other, the engine RPM’s surge wildly out of control. Either event is not only scary as hell, it can be seriously dangerous.
To correct the problem, General Dynamics, utilizing data and recommendations from NASA test pilots and engineers redesigned the intakes, moving them away from the fuselage, incorporating a sliding forward end of the intake which could be moved fore or aft depending on how much air the engines needed in various flight regimes and angles of attack (nose up or down) and incorporating small air fences known as “vortex destroyers” inside the intakes. Later models incorporated Triple Plow II intakes, a further improvement incorporating suck-in doors approximately a foot back from the lip of the intake replacing the early sliding section, a blossoming spike that opened or closed as needed to control airflow and placed even further out from the fuselage.
On the cutting (or ragged) edge
The Aardvark was by far the most sophisticated aircraft of it’s time, what with all those computers and black boxes: the AN/APQ 110 terrain following radar that allowed the aircrew to take their hands off the stick and let the plane fly itself at ridiculously high speeds at ridiculously low altitudes going up, over, around and down whatever obstacles the terrain put in it’s way, the first-ever airborne doppler radar and the first-ever inertial navigational system. Then there was the AN/APQ113 Attack Radar System (ARS) that could accurately identify targets and put ordinance on a dime. These were all-new technologies in the ’60’s, and caused more than one engineer more than one lost night’s sleep as they were being developed. They also caused more than one Aardvark to slam into the ground, with the loss of more than one two-man aircrew.
While other tactical aircraft came equipped with the likes of Martin-Baker ejection seats (“meet your maker in a Martin-Baker”), the F-111 had an ejection capsule: essentially, the entire cockpit separated during ejection sequence. It was designed to act as a life raft at sea (by pulling a pit-pin at the base of the pilot’s stick, the stick was converted to a bilge pump) complete with attenuation and flotation bags that both righted the capsule and added to its buoyancy. On land, it provided shelter and the same bags cushioned the impact of landing. No other aircraft in the world was so equipped (true, the B-58 and XB-70 had individual encapsulated crew ejection systems, but not the entire cockpit). In the ’70’s, the B-1A prototypes had a crew escape capsule, but it was not incorporated into the final design of the B-1B.
Off to ‘Nam
In the Spring of 1967, 18 RDT&E (Research, Development, Test and Evaluation) F-111A’s were tested at Edwards AFB, Ca and Eglin AFB, Fl during Combat Bullseye, a program to test the bird’s weapons delivery systems. The Aardvark exhibited superior accuracy and indications of it’s future capabilities during the program, raising Air Force hopes for the troubled aircraft.
Buoyed by their performance in Combat Bullseye, the Air Force transferred five of the test planes to Nellis AFB, NV for two more programs: Harvest Reaper, in June 1967 intended to identify any continuing problems with the plane and prepare it for combat in Vietnam, and Combat Trident in July to train an initial cadre of combat veterans to fly them.
Harvest Reaper commander, Col. Ivan “Ike” Dethman, an experienced fighter jock and veteran of B-26 missions in WWII, flew his F-111A from Ft. Worth, Tx to Nellis AFB, some 1,047 miles at a constant altitude of 500 ft with the TFR in autopilot. The only time, he reported, that he flew the plane manually was takeoff and landing. The man was positively thrilled with the bird!
The unit, Detachment 1 of the 4481st Tactical Fighter Squadron (later redesignated the 428th) recieved new F-111a’s with improved TF-30-P3 engines at the rate of one a week until all six were in place and ready to fly.
Twenty-two pilots and seven instructor pilots (IP’s) trained in the aircraft as they developed the tactics the F-111’s would use in Vietnam. Even if the pilots, all veterans of Korea and Vietnam were quite skeptical at first- especially of flying low-altitude with the TFR on and their hands in their laps- they soon found themselves converted into whole-hearted believers in the new aircraft. They began to resent the criticism of the plane in the media, as well as that from politicians. One was quoted as saying, “The guys who badmouth this airplane are the guys who never got in the cockpit.”
The aircrews’ enthusiasm carried over to the ground crews whose task it was to keep the multi-million dollar Aardvark flying. And believe you me: it can be quite a task…I speak from experience. But, by God they got ‘em flying and kept ‘em flying to the tune of 58-60 hours a month, which was twice the amount of flying time of anything else at Nellis.
Even so, the press and the politicians kept up the snottiness about the F-111, and turned it up a notch or two putting pressure on the Air Force to produce a solid demonstration of the aircraft’s capabilities. This constant pressure was one of the factors leading to the decision to deploy the F-111 to Vietnam under Combat Lancer. Combat losses experienced by F-4’s and F-105’s were another factor leading to the decision, in early 1968, to deploy before training was completed and discrepancies with the aircraft cleared.
On the morning of March 15, 1968, C-141 Starlifters loaded ground crews and support equipment and along with six F-111A’s, took off for the Aardvark’s trial by fire in Vietnam.
Coming up in Part 3: The politically motivated and ill-fated operation Combat Lancer begins and deals the F-111 program a serious setback. In the meantime, check out the F-111 on the Discovery Channel’s series “Wings” in five segments