Imagine you’re an airline and one of your flights has a technical issue with an engine at a remote airport. The quickest way to get a replacement out to them in the past was to use a spare engine pod.
This comprised of a streamlined container with an extra engine inside, which was bolted to the bottom of the wing at the ferry hardpoint. Often they were called the “fifth engine” as it was originally an aircraft with four engines transporting them.
The Spare Engine Pod
Once the jet age began, Australia’s Qantas pioneered the use of the spare engine pod on their Boeing 707 aircraft. Whilst cargo planes could probably have done the job, it was a lot faster to strap a fifth engine onto another jet and send it on its way.
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- Qantas Boeing 707-138 N31239 during testing in June 1959. This became VH-EBA, which still exists in a museum in Australia today as it was the first jet ever registered down under.
Engines were carried inboard of the other engines to minimise yaw. Of course, there was a penalty in carrying an extra engine, as the added weight reduced range and increased overall fuel consumption.
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- Blink and you’ll miss it! A CP Air Douglas DC-8-43 carrying a fifth Rolls-Royce Conway in the pod.
In addition to the Boeing 707 and Douglas DC-8, the British entry into the long-haul arena in the 1960s also had this capability. You can see it on a Vickers VC10 below.
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- An East African Airways Super VC10 in a London Heathrow hanger in 1974.
Naturally the Boeing 747 also permitted this, which you can see at the top of the article. It must have been interesting for the passengers to see their special plane with five engines at the gate!
How About The Fourth Pod?
Trijets were all the rage during the late 1960s and 1970s, with the Boeing 727 and Hawker Siddeley Trident operating short routes. These could not carry an extra engine, but their larger widebody cousins could.
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- A fourth engine snuggled under the wing on an Air Lanka Lockheed TriStar 500
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- Looking good on this Canadian Airlines Douglas DC-10.
Both the Lockheed L-1011 built in Palmdale, California and the Douglas DC-10 from Long Beach, California had a ferry hardpoint. Not sure how often you would have seen these, but the capability certainly existed.
Overall Thoughts
Air freight has moved on since the 1980s and these days passenger aircraft no longer need a ferry hardpoint. Engine reliability is also much improved since the first turbojets entered airline service in the 1950s. That means no more spare engine pods or planes with a weird number of engines flying about.
While that is a shame for people who might like interesting aviation, life moves on. No doubt in today’s social media age, people would be gawping, photographing and posting online as soon as they spotted these… if they noticed at all, of course!
Have you ever flown on board a plane carrying a spare engine pod or know more about them? Thank you for reading and if you have any comments or questions, please leave them below.
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Featured image via Reddit.
Qantas Boeing 707 via Aussieairliners.org.
CP Air Douglas DC-8-43 by Gary Vincent on Airliners.net.
East African Super VC10 by Steve Fitzgerald on Airliners.net via Wikimedia Commons.
Air Lanka TriStar 500 by Felix Goetting on Airliners.net via Wikimedia Commons.
Canadian Airlines Douglas DC-10 via Reddit.
I was on a TWA 747 when it ferried an engine to Europe
Nice! That would have been a relatively rare thing.
On your photo at the top of he page, are you sure this “extra” engine is not being tested? As opposed to being a spare?
I’m very sure, because the engine is only able to be bolted to the wing at that point. There is no provision for fuel pipes, controls and all the rest that are required to run an engine there.