With most commercial aircrafts using turbofan engines which makes it faster. Why do a portion of military planes still uses propeller engines? I think the C-130 is the best example.
In: Engineering
>With most commercial aircrafts using turbofan engines which makes it faster.
Because speed isn’t the only thing to optimize for.
Turboprops are considerably more efficient at slow speeds and lower altitudes. This also makes them capable of taking off from shorter runways.
Also it’s considerably safer to take off from a dirt runway with a turboprop than a turbofan because you don’t have to worry as much about the engine ingesting rocks or whatever.
You sometimes want a plane that can fly slower and lower and more fuel efficiently and cheaper. Great for training, surveillance, austere situations, firing platforms, parachute launch.
For most military purposes, propeller planes are used because they require a shorter runway to take off. C-130s deliver cargo all over the world; they don’t always have the luxury of fully-built modern runways
Jets and turboprops both have different use scenarios. Jets are more efficient at moving things far, high, and fast. Turboprops are more efficient at shorter distances.
The props provide a huge amount of lift to the wings which allows it to fly at lower speeds. This is useful for refueling helicopters, dropping people via parachutes, and search and rescue activities, among the benefits others in this thread have mentioned
Those propeller aircraft still have jet engines, they are just connected to a propeller instead of a ducted fan. That gives them different trade-offs, propellers (turboprops) are slower but have better efficiency.
A new type of engine we might see in the next decade or so is an unducted fan engine like the CFM Rise, which aims to combine the efficiency of a turboprop with the speed of a turbofan.
The C-130 is a roughly 70 year old airplane. At the time when it was designed, the large, highly efficient turbofans that power our commercial airliners didn’t yet exist.
Other commenters have pointed out several other good reasons (such as efficiency at low speed/low altitude) to pick turboprop engines for similar roles. The Airbus A400 is a contemporary example. One reason that hasn’t been mentioned yet is that turboprop engines are typically more tolerant of sandy/dusty environments versus turbofans.
For smaller “general aviation” aircraft like a Cessna 172, the reason they’re still propeller-powered is two-fold: jet engines are much more expensive and maintenance intensive than radial/cylinder engines that produce similar amounts of thrust, and small jet engines are also EXTREMELY inefficient for the amount of thrust that they produce.
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