by Brian Carlin
At about an hour and a half into the test, the heavy blanket of silence was broken by the sound of a chair being scraped on the floor as someone stood up. The invigilator looked up expectantly as one of the examinees approached him and handed over his completed paper. After a short interval, another chair scraped and another paper was turned in. I was still struggling through the test, racking my brains on many of the questions, as I tried to match them to correct alternative answers. Even if you knew the subject like the back of your hand, the question could still be answered incorrectly due to carelessness in reading it or the answers. And if all the answers to a question appeared equally correct, it was a clear sign that you were in deep trouble, leaving just one tried and tested option—eeny, meeny, miney, mo…
The frequency of papers being handed over increased, until finally I was able to put an “X” on my selection to question number 100. A quick look over the question paper, which was so fleeting as to be worthless and I was done, one way or another. This time it was my chair that made a noise as I stood up and handed my hopes and dreams over to the invigilating officer. I noticed that a good few still remained bent over their papers, so I tiptoed out of the room as quietly as possible. Then it was back to the billet and the inevitable post-mortem with the other lads. We recalled questions from memory and then discussed what answers we’d given. Sometimes my heart sank as I realized that a particular answer I had selected was wrong and at other times my spirits soared when I was able to confirm that I’d got one right. All in all, I felt I had a fair chance. Not a “dead-cert” pass, but a feeling that I’d done all right. But, of course, we had yet to face The Board.
If sitting for the Paper was nerve-racking, it was at least civilized and predictable by being set for a certain time of day, for a particular duration and consisting of no more or less than 100 questions. But not so with taking the Board, which involved spending an unpredictable amount of time alone with one of the formidable senior NCOs from TSTS, the Trade Standards and Testing Section, who could ask as many or as few questions that he considered necessary to ascertain the extent of our knowledge. Since there were only a few of these examiners and many of us, we were obliged to wait until called individually. Awaiting my turn to be marched in front of a firing squad could have been worse, but only marginally so.
There were two waiting areas, which were used in serial fashion. The main holding area was our classroom in Workshops. Here we sat, frantically going over our notes and quizzing each other on how certain types of equipment and complex circuits operated. A TSTS senior NCO would come into the classroom every hour or so and read off perhaps half a dozen names from a clipboard. The chosen few would then rise and follow him to a smaller holding area close to where the Board was actually being held.
My name was eventually called as one of a group of six, so I dutifully stood up and followed the Senior Technician who had come to summon us. All six of us were as joyless as condemned men being herded to the scaffold. Only Charlie, the class swot who wore his beret pulled down over his forehead, seemed to be excited by his anticipation at what was to come. We were led to a small cubicle in the main practical application area of the workshop where, over the past few months, we had undergone practical training on the equipment. Consoles of aircraft electrical apparatus surrounded us on all sides and in the centre of the workshop stood the grounded Hawker Hunter jet fighter that I’d crawled over many times during various phases of instruction. The sight of all this was very familiar, since we had spent many hours in that same location. That investment of time would now be put to the test, when the TSTS examiner began prying and probing to determine the depth of knowledge that we had managed to absorb.
On entering the cubicle, we were told to wait there until an examiner came and called for us by name. And so, having brought our notebooks with us, we settled down once more into the relentless task of trying to cram every last little scrap of knowledge into our heads.
Very soon, a Chief Technician appeared at the door of the cubicle and announced a name. A boy entrant stood up and then followed the grim-faced NCO, who had turned and walked off in the direction of the equipment consoles. Shortly afterwards, another NCO came to the door and our number was reduced by one more. We waited for perhaps a quarter of an hour before a third examiner came into the cubicle, looked at his clipboard and then called out the name of the third victim. Another agonizing period of waiting and then the first boy came back. He looked ashen and as he came into the cubicle we all anxiously asked him: “How did you do?”
He rolled his eyes upwards as he picked up his belongings, “Tough,” was the only response we got before he hurriedly exited the area.
“Carlin!” Oh my god, it was my turn. I looked up to see the grim-faced NCO who had made an appearance after our initial arrival in the cubicle, now framed in its doorway. Just my luck, I thought.
“Chief,” I responded, whilst rising from the uncomfortable wooden chair. As before, he turned and started walking away from the cubicle, apparently confident that I was bringing up the rear. He came to a halt on reaching the equipment consoles and turned to face me, clipboard poised in one hand and a pen in the other.
“Carlin?” He asked.
“Yes, Chief.”
“What’s your service number?” I told him and he wrote it down on the clipboard. He continued writing for a few moments as I stood there, feeling awkward, exposed and vulnerable. When he had finished he lowered the clipboard and started walking towards one of the consoles.
“Okay, let’s start here,” he announced. “Can you name this piece of equipment?” As he said this, he placed his hand on a black-painted metal object that consisted mostly of nine-inch square cooling fins. Its rectangular base was bolted to a paxoline board and the various electrical wires connected to its terminal strip were banded neatly together, before disappearing into a hole drilled through the paxoline. They re-emerged through similar holes drilled at other locations on the console, from where they were connected to the terminal strips of adjacent black boxes. The colour of the equipment wasn’t particularly significant, since all aircraft electrical equipment of that time was painted black.
“It’s a type 23 voltage regulator, Chief,” I responded, knowing that this was only the preliminary question to a whole series that would test the depth of my knowledge, probing for chinks and flaws.
“What does it do in this circuit?” He asked.
I then went on to identify the circuit as the P3 generator power circuit used on four-engine aircraft and that the output voltage of each engine driven generator was controlled by one of these type 23 “slave” regulators, in a “master-slave” control system. A question and answer session ensued, during which I was able to confidently explain that the “master” regulator controlling all four slaves was a type 32 voltage regulator. We then got into the intricacies of voltage equalizing and load sharing and as I answered his questions, it felt as though there were two people inhabiting my body. One, a kind of stranger, was confidently expounding on all of this knowledge in answer to the Chief Tech’s questions and the other, whom I perceived as the real me, was watching with mouth agape in awe at this amazing performance by my alter ego. Luckily for me, the examiner was only aware of the first persona as we finished with the P3 generator circuit.
A feeling of calm confidence had descended on me by this time and in a way, I was enjoying the experience. We moved along the row of consoles to where another type of voltage regulator squatted on the flat workbench. Here, the vertical paxoline board behind the bench wasn’t equipped as a console furnished with aircraft electrical components. Instead, it was configured as a tool-board of a type known as a shadow-board. Silhouettes of various common hand tools had been painted on the board to visually indicate which tool belonged in that space. The tools were held on the shadow-board by spring clips on or around the “shadow.” All of the tools were in place as we approached the bench, so the shadows weren’t plainly evident. We stopped in front of t
he voltage regulator and the Chief Technician looked down at it. I followed his example.
“I want you to do a mechanical setting on this,” he said, placing a hand on top of the regulator for emphasis, as he had done before.
The task was an easy one. The basic aircraft voltage regulator of that era was an electro-magnetic device that compressed or relaxed a “pile” of carbon washers in order to increase or decrease the current flowing to the generator’s magnetic field. The mechanical setting was a coarse initial adjustment, from which finer adjustments could be made to achieve the correct output voltage from the regulator when power was applied to the unit. We had been taught the procedure, which involved screwing the magnetic core all the way into the regulator until it bottomed and then screwing it out until two threads showed. Then, at the other end of the regulator, screwing the pile compression screw in until it gently made contact with the pile and then unscrewing it three-quarters of a turn and locking it. That was the extent of the mechanical setting. But simple though it seemed, there was a need to be wary because this type of question concealed a hidden trap that our instructors had frequently warned us about—although we had been taught the procedure, we weren’t supposed to perform it from memory. Instead, we were required to refer to the appropriate servicing schedule and follow a step-by-step set of instructions whilst performing the task. If I didn’t ask for the servicing schedule, I would lose marks.
“Can I please have the servicing schedule, Chief?” I asked.
Without a word, the Chief Tech immediately opened a drawer in the bench and produced a sturdy cardboard binder containing the servicing schedule, which he handed to me. Then he made a notation on his clipboard. Turning to the first page of the servicing schedule, which I had laid on the bench beside me, I proceeded to make the mechanical setting, using the special non-magnetic screwdriver required by the servicing schedule. It’s fair to say that I would probably have forgotten about the special screwdriver if I had failed to read the servicing schedule and that would have been two marks against me for the price of one.
We moved on to other things. Sometimes, I was asked to
trace out complex circuits on wiring diagrams and explain how the circuits operated. At other times, I was instructed to perform other servicing tasks and as with the voltage regulator, there was always a need to be conscious of using the correct procedures and observing appropriate safety precautions.
For one such task, the examiner set me to perform a battery change on the Hunter aircraft that stood in the centre of the workshop. The job itself was easy, needing only a little exertion to lift the heavy batteries. But I was also being examined on whether or not I used the servicing schedule and observed the safety precautions that it included, with regard to working with batteries. Handling them was one thing, because of the corrosive acid they contained, but there was also a need to observe certain precautions when connecting and disconnecting them from the aircraft’s electrical system. The negative battery terminal is always connected to the metal airframe, just as the same terminal of a car battery is always connected to the car body. The main reason for this is to save weight and expense by using the metal of the airframe as the return conductor to carry the current back to the battery for all circuits. When disconnecting battery cables, the negative side is disconnected first, to electrically isolate the battery from the airframe. This makes the creation of a hot spark due to an accidental short-circuit much less likely, which could otherwise easily happen if something metallic—perhaps a spanner—accidentally touched against some part of the aircraft frame while it was being used on the positive battery terminal. Sparks of any kind are something to be avoided around aircraft, where easily ignited aviation fuel is ever-present.
I disconnected the negative cable first, then the positive cable, before loosening off the bolts that clamped the two heavy lead-acid batteries in place. At this point, the examiner stepped forward and told me to assume that I had already removed the old batteries from the battery bay and had replaced them with new batteries. Now he wanted me to finish the installation. I then performed the procedure in reverse, first clamping the batteries in place and wire-locking the wing nuts that bolted them securely to the battery trays. Then I connected them up to the aircraft electrical system, reading the servicing schedule as I went along and making sure that reconnecting the negative cable was the very last item of the procedure.
I was now supposed to go into the cockpit and make sure that the instruments powered up when the battery isolation switch was operated to the “on” position. This action required that another very important safety precaution was observed. I climbed the ladder leading up to the cockpit. The Perspex canopy had already been slid all the way back on its rails, allowing free access into the cramped one-man space within. It only required a foot to be planted on the seat cushion down inside the well of the cockpit, followed by the other foot, before sliding down onto the seat while holding on to the top of the windscreen frame for support. Oh so easy! But there was one important thing to check first. Was the seat safe? Were the safety pins in the right places, making accidental operation of the ejection seat impossible? So, whilst still standing on the ladder and with one hand on the outside of the canopy, I peered through the clear plastic and saw that the large red metal disc attached to the pin was threaded through the triggering component of the ejection-gun firing mechanism, at the very top of the seat, to prevent accidental operation. So far, so good! Now, before stepping in, I needed to look down along the side of the seat to make sure the drogue gun pin was in place and then check for a safety pin in the alternative firing handle down on the front edge of the seat pan. Yes, they were both in place. I turned to Chief Tech Grim-Face, knowing full well that he was watching me like a hawk. “I’ve checked the seat Chief and it’s safe.” He nodded in understanding as I swung a leg over the lip of the cockpit and proceeded to enter. Then he came up the ladder after me, looking into the cockpit as I flicked the toggle of the battery isolation switch upwards and was rewarded by hearing a satisfying clunk coming from somewhere underneath the cockpit as the battery circuit breaker closed. Immediately, the aircraft’s electrical circuits energized. Gauges suddenly sprang to life, gyros started to whir as they spun up to speed, the “generator failure warning light” glowed red and all three “undercarriage locked down” lights glowed green. The artificial horizon chattered erratically for a few moments before settling down and the G4B compass card whirled crazily until I reached out to press a small button that brought it to an immediate stop.
“Battery functionally checked Chief,” I announced.
“Okay. What do you need to do now?” He asked.
“Sign the seven-hundred, Chief,” I responded, referring to the aircraft’s servicing record.
“Okay,” he said, “turn the battery off and then go and do that.”
We walked together to where the 700 lay on a bench near the Hunter. I searched for the correct page and then made the appropriate notation in the log.
The Chief Tech watched as I signed and dated the entry and then beckoned that I should follow him as he made his way to another console.
“I want you to perform a functional check on this circuit,” he announced, indicating a console that was wired up as an engine starting system. Everything was there except the engine and the electric motor that turned it during the initial phases of a jet engine start-up.
The starting system was designed to rotate the engine slowly at first and then cause it to speed up in two separate stages, in much the same way that a car is taken from standstill to normal road speed through successive gear changes. But the speed changes in this case weren’t achieved by changing gears. Instead, the electric current to the starter motor was initially kept low by inserting a very large resistance in the circuit. Then, when cued by a timing device, some of the resistance was automatically removed, causing the motor to turn a little faster. Finally, all of the resistance was removed and the motor was free to run up to it
s full speed. When the fuel in the engine ignited and made it turn faster than the electric motor, the starter system shut down.
Of course, all of this involved the participation of several electrical devices to make it happen and most of them were wired together, in faithful reproduction of the real thing, on the console that now confronted me. Other than the absence of a real engine and starter motor, the only other difference was a group of small, coloured indicator lights used to indicate the various stages of resistance as they were switched in and out of the starter motor circuit.
I asked for the servicing schedule and started reading it. All I needed to do was turn on the supply voltage to the console and then press the engine start button. The circuit should step through its three stages and then stop. But this was an exam and things weren’t going to be that easy!
The first indicator light glowed, showing that the resistance had been inserted into the motor circuit and, in real life, the motor and engine would be starting their initial rotation. I could also hear the whir from the clockwork timing mechanism as it was being electrically wound up, but when several seconds had elapsed and the second indicator light remained dark. Uh, oh, I thought, looks like we’ve got a snag! The servicing schedule wasn’t going to help here; this came down to tradecraft and the ability to think and work logically in order to track down the cause of the problem and then fix it.
First, I needed to check the obvious, although I knew in my heart of hearts that the cause of this fault was going to be anything but obvious. The second light hadn’t come on, so the most obvious and the simplest course of action was to check for a failed bulb. I didn’t know what Grim Face’s expectation might be. Maybe I was supposed to deduce that it wasn’t a simple bulb failure because of other less evident symptoms, so there may have been marks against me instead of marks in favour, but I had chosen a certain course of action and was determined to stick with it. I unscrewed the indicator light’s lens cap and removed the small bulb. The tiny filament looked intact when I held it up to the light but I flicked a finger gently against the glass envelope anyway, just to check for the telltale vibration of a broken end. It still looked okay, but that didn’t mean there wasn’t a fault.
