Engineering problems from a practical perspective.

2. - Idiot Proof Engine Design

Lubrication of all engines is important and for high-power aero engines especially. In order that oil gets to all the required areas the Merlin engine is fitted with an oil pump that forces oil through the lubrication system.

Packard/Rolls-Royce circa 1942

Rolls-Royce Merlin engines manufactured by Packard in the USA were delivered to an RAF station in Canada for acceptance testing prior to shipping to the UK.

One batch of engines started to fail within minutes of being run up and it was obvious that there was a systematic problem and that the failure was a result of poor lubrication.

A cursory examination seemed to show that everything was in order but then a more experienced eye noticed that the oil feed and return pipes to the engine block weren't in the normal position, indeed they appeared to be reversed.

That was surprising as 'by design' it was impossible to swap the pipes  as they had different diameters and threads. Unfortunately this safety feature relied on the appropriate pipe adapters being screwed into the engine block in the right positions, the tapped holes in the engine block having the same size and thread.