Retrotechtacular: The US Air Force Has The Biggest Fleet

When it comes to the superlatives of aviation, there are aircraft larger than the C-5 Galaxy. [Howard Hughes]’s Spruce Goose has the largest wingspan, and the Soviet and now Ukranian Antonov AN-225 Mriya has the largest cargo capacity. When it flies in the next year or so, Scaled Composites Stratolaunch – a twin-hulled beast of a plane designed to haul rockets up to 30,000 feet – will be the aircraft with the largest wingspan and the greatest cargo capacity.

These superlatives, while completely accurate, fail to realize these huge planes are one of a kind. There is no plan to build a second Stratolaunch, and the second airframe for the AN-225 is rusting away in a field. If you want to find a fleet of enormous aircraft, there’s only one contender: the C5 Galaxy, the largest plane in the US Air Force inventory.

This video, from the USAF Archives circa 1968, goes over the design, construction, and operation of the C5 Galaxy. It covers the program beginnings, the shortcomings of earlier aircraft, and – of course – completely disregards the initial problems of the C5.

While not the largest aircraft to take to the skies at the time, or the heaviest, the C5 featured an enormous number of technological innovations. Not least of these was the massive Ge TF39 engines hanging off the wing. Before this engine, turbofans had very low bypass ratios. Lower bypass ratios for a turbofan means lower efficiency. The TF39 changed this with a bypass ratio four times larger than any before it, leading the way for modern aviation powerplants. Just look at a few old pictures of jet airliners – you’ll notice the older aircraft used long, skinny engines. These were still turbofans, but highly inefficient. Look at modern airliners, and you’ll see engine nacelles nearly as large as the fuselage itself. These high bypass turbofans run cleaner and more efficiently, and they were first found on the C5 Galaxy.

Of course the C5 wasn’t without its problems. Initial tests of the wing revealed structural weaknesses, which lead to the Air Force derating the cargo capacity of the first generation of C5s. This was due to poor aluminum forgings in the wing, and while this was fixed in later airframes (and earlier airframes modified with the new wing spars), this problem led to the C5 being called a massive blunder. Cost overruns plagued the project, and congressional investigations investigated the problem.

Despite these initial problems, and calls for the cancellation of the program, the C5 is a remarkably successful aircraft. Few other aircraft have the payload capacity or volume of the C5, and there is no other fleet of larger aircraft. The C5 will be in service until at least 2040 – 70 years since its introduction – and will go down in history as one of the most successful aircraft development projects of all time. Keep that in mind when you hear about the Air Force’s latest snafu over a new aircraft program.

Filed under: Hackaday Columns, Retrotechtacular