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The following image, from the Qantas Heritage Collection (via aussieairliners.org), shows the flight crew inspecting the 'Pod-Pak' prior to departure:

enter image description here

Based on the angle of their heads, I'd assume it's the engine-looking device to the right of frame.

Also, what are the rocket engine-like tubes at the left of frame?

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A Pod-Pak is a aerodynamically shaped enclosure to transport an extra engine under the wing.

From 'Flying Magazine', Nov 1959:

Spare engine in “Pod Pak” is the airlines' modern method of transporting extra engines to maintenance points. Nine major airlines flying Boeing 707s have ordered Pod-Paks. This spare suspended below the wing of a Qantas Airline's 707 shows the Pod Pak suspended from the airplane's front wing spar by means of two fittings and to the landing geard support rib by four bolts. Fairings streamline ends of the engine and normal engine cowls enclose the sides. No structural changes are required in the airplane's wing and, when not needed, Pod-Pak can be removed completely.

The exhaust pipes of the Pratt & Whitney JT3C turbojet engine on the left of the picture are an attempt to reduce the noise of the engine. They should aid in the mixing of the core exhaust stream and the freestream air which is quite a noisy process.

The successor to the JT3C, the JT3D, was a turbofan. In a turbofan there is a layer of bypass air between the core exhaust stream and the freestream which reduces the noise and increases the efficiency. Later B707s fitted with the JT3D engines did have not have the 20 pipes exhaust. Most of the aircraft which were originally fitted with the JT3C where later retrofitted with the JT3D.

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