Saturday, June 27, 2015

The Engine Run

I can honestly look my grandkids in the eye and tell them I have sat in the driver's seat of a jet fighter, capable of Mach 2 plus, and started the engine. Then I have pushed the throttle as far forward as it would go, lifted it to engage the afterburner, and pushed it to max, and felt the aircraft kick as I did so. If I left it at that and they asked no questions I'm sure they would stand in awe and tell all their friends about the exploits of their grandfather.

Running aircraft engines, either installed or in a test stand, was simply a part of the engine fitters, or Sumpies, job. And, of course, are part of a sumpy's memory.

Richmond, 1975
I will start with a Caribou story. Of course, names where used, may have been changed to protect the guilty. I was posted to 38 Sqn in March 1974. Flight Sergeant Bill was the instructor on our Pratt and Whitney R2000-7M2 Caribou engine conversion course and, like most sumpies,a great bloke.

After gaining experience on type it came time to be authorised to do engine runs. Again Bill was our instructor. He had drilled us well in the classroom on engine run procedures, so when he asked ‘What steps do you take in the event of engine fire’ we quickly spat out the answer. ‘Close the throttle, turn off the fuel pumps, turn off the magnetos.’

‘Wrong’, said Bill. ‘You take big ones and plenty of them. Firies are paid to put out fires, you’re not.’

Williamtown, 1970/71
My first posting after Wagga was 77 Squadron and during that time I spent 6 months in Engine Repair Shop (ERS), 481 Maintenance Squadron. Following servicing at 481 the Atar engine was taken to the engine run area for final testing prior to installation in a Mirage. But as flying squadrons also ran uninstalled engines sometimes this incident may have occurred any time.

Uninstalled engines were run in a purpose built stand. This was under cover, as it was at Butterworth. The engine was run from an air conditioned control room with a couple of fitters outside the room working on the engine.

Instead of referring to engine speed on the Atar as RPM, or revs, we used N - for number of revolutions. This was may have been a unique French thing, given the origin of the aircraft. In the test room N was indicated by a digital tachometer.

On one run I recall the sergeant in charge of the crew had a weakness for poker machines. On a visit to RAAF Edinburgh in South Australia, so it was said, this gentleman had ‘acquired’ a two cent poker machine from that bases’ Sergeants’ Mess. Be as it may, after all tests and inspections had been completed the sergeant would not let the operator shut down until he had lined up 7777 on the tachometer. For those whose lives have been sheltered, four sevens on a poker machine is - or was - a jackpot.

Darwin, 1970/71
Regular deployments to the top end were a part of life for members of 77 and 3 Squadrons. For ground staff this meant a long flight from Williamtown in the back of a C130 Hercules. Conditions were a little cramped as we were packed in around the ground support equipment, spares and other equipment considered necessary for the few weeks we would spend in the tropics.

The Mirage was not designed to facilitate engine repairs with the engine in situ. With some exceptions, any work requiring the replacement of an engine component required removing the engine from the air frame. Following removal and replacement a test run was required.

On this occasion we were landed with a repair job after the last sortie of the day - something that was not uncommon. We worked well into the night the finish the job and, some time after midnight towed the Mirage to the run up area. This night the Corporal took a turn in the driver’s seat. After all checks were completed he said - we had communication via cable plugged into the aircraft - ‘If its good enough for me to be out of bed at this time in the morning’ and pushed the handle through to full afterburner and let it stay there for a minute or two. Who knows if we woke anyone up that morning.

Butterworth 1971/74, 77/80
I have memories of Butterworth:

  • Swinging Sisters; and
  • Heat.

Swinging Sisters
The engine run area was surrounded by grass covered mounds as a noise control measure. The grass was regularly cut by local women that we called the Swinging Sisters. These women, covered from head to foot with scarves and sarongs toiled endlessly  in the hot sun. They were so  named because they worked with a scythe held in one hand, swinging it in a continuous circular motion over their heads and down to the next few tufts of grass.

We wore hearing protection and kidney belts - the latter to supposedly protect the fine blood vessels in our kidneys. Now a jet engine in full afterburner is one of the loudest things on the planet - well above the pain threshold. But this did not deter the sisters who continued their toil as we did ours. I often wonder what hearing loss they suffered, not to mention the wear and tear their shoulders must have endured.

The Heat
It goes without saying that Butterworth was hot. Part of the engine run procedure was to contact the control tower for the temperature of the day. This determined some of the settings we had to make on the engine. At Butterworth it was almost a waste of time as it hardly varied.

But the worse part of the job was sitting in the cockpit for the run. For some reason known only to the Mirage's designers the cockpit air conditioning only operated when the jet reached something like 90 miles per hour and we had to keep it closed. If my memory is correct, on my first tour no shade was provided and we could sit in the cockpit for perhaps up to an hour. While I have no knowledge of anyone passing out it must have been a real possibility. By the time the run was finished the shorts of the bloke in the cockpit looked as if they had just been pulled out of a tub of water. No wonder sumpies at Butterworth had a real thirst.

On my second tour a shade cloth had been erected but this only provided shade for a couple of hours in the middle of the day. Even then it made little difference. I remember one bloke taking a bottle of Coke into the cockpit one day. When he finished it he put it under the seat and it was forgotten until a pilot came back from a sortie complaining about a Coke bottle rolling around the cockpit.
Mirage Fuel Consumption
One check we performed was the fuel flow in full afterburner.  This had to be 60 gallons per minute - approximately 270 litres for those unfamiliar with Imperial measures. Now you can talk about the kick you get from your hot set of wheels when you floor the accelerator but it is nothing like the power surge when full afterburner is selected. And for that experience I thank the Australian taxpayer who footed the bill for that 60 gallons a minute.


  1. The Debi? meter use to be a blur ...

    1. Debimeter - a term I haven't heard for a long, long time.