Shake Bottle Well Before Pouring

Contribution by Chris Bester

In aviation, as in life, small things can sometimes make a huge difference. We learnt this lesson in an interesting way thanks to some large drums of engine oil.

At one point in our operations, Safair used to purchase engine oil for the Herc engines in two pint tins. Due to sanctions we were forced to change our suppliers and the new suppliers we found didn’t produce these smaller tins and so we were required to purchase our oil in large 44-gallon drums.

Around the same time, there was an operational need to increase the operating altitudes. Necessary approvals were granted and ops implemented the new procedure but there was a problem: the aircraft simply couldn’t achieve the new altitude due to a loss of engine oil pressure.

Many weeks of intense discussions followed as we tried to figure out what the problem was. Physical inspections were performed on engines and systems but absolutely nothing yielded any positive findings.

Eventually, we made a breakthrough.

The engine oil used in the Herc engines includes an anti-aeration additive of 2%. This additive prevents the oil from forming bubbles at high temperatures and pressures. This is essential because bubbles in the oil will result in reduced engine oil pressure.

The trick is that the anti-aeration additive tends to settle in the oil and so whenever the oil is topped up, it’s important to shake the tin to ensure that the liquids combine and that the dosage is correct. Since we were now getting oil in these massive 44-gallon drums, nobody was shaking them, and so the anti-aeration additive was being left in the bottom of the drum. The result was these low engine oil pressure issues at higher altitudes and the solution was pretty simple: “shake before pouring”.