8
$\begingroup$

In this article by CNN, the C-130 involved in the unfortunate crash in Savannah, GA is referred to as a "jet." Is this considered proper usage? I'm not looking for public opinion here but official categorization, if one exists. Perhaps there is an USAF or FAA document I've not been able to find which delineates such things. I would imagine that there is also an engineering or academic definition of such things.

The AV.SE description of the Turboprop tag states that it should be considered "as opposed to a jet engine."

Wikipedia says that "Turboprop engines are jet engine derivatives." which really sort of muddies things but the actual turboprop article notes that "the exhaust jet typically produces around or less than 10% of the total thrust" It never occurred to me that the thrust produced by a turboprop engine is even measurable. Would this factor, then, be the delineation between jet and prop? Should it be a matter of whether the exhaust gasses or rotating components propel the aircraft?

So to restate my question, Should a C-130 be called a jet even though a significant percentage of its propulsion is derived from a propeller?

Note: Please consider JATO/RATO outside of scope of this question.

Improve this question
$\endgroup$
3
  • 13
    $\begingroup$ Media reports are not renowned for their technical accuracy, aviation is no exception. $\endgroup$
    – fooot
    Commented May 3, 2018 at 15:28
  • 1
    $\begingroup$ Anedocte: years ago a airplane crashed on take off and the cause was quickly pointed as wind shear happens in portuguese this is called "tesoura de vento" (literally "scissor of wind"). Well all newspapers actually buys news from a news agency and that news was written as "tesouro de vento" (literally "treasure of wind"), maybe only a typo but I cannot find a single newspaper in portuguese language without that error $\endgroup$
    – jean
    Commented May 3, 2018 at 16:32
  • $\begingroup$ I imagine it was a casual use of slang in the same way one might refer to a motor car as a ‘wagon’ even though it is clearly not pulled by horses. $\endgroup$
    – Arkhem
    Commented Jul 26, 2021 at 7:25

5 Answers 5

Reset to default
9
$\begingroup$

CNN actually called it a jet with four turboprop engines, if you can believe that.

ICAO is probably as universal a source as you will find. They list the C130 as turboprop/turboshaft. Their table of aircraft type designators allows selection of engine types from this list: Jet, Turboprop/turboshaft, electric, piston and rocket. There are no associated definitions.

Improve this answer
$\endgroup$
3
  • 1
    $\begingroup$ Yes and they also seemed to imply that the fact that the plane was high-wing was salient to the final few seconds of flight. The only reason I can think their statement would make sense is if an average person were to compare the shape of a C-130 to other things at an airport. It is closer in size to jet than to a B1900 or a Dash8, which are the turboprops most people would see on the apron. Also, your answer is exactly what I'm looking for. ICAO doesn't let you pick more than one type from that list, does it? $\endgroup$
    – user28387
    Commented May 3, 2018 at 17:59
  • 1
    $\begingroup$ Years ago when I was in the military and worked C-130’s, a new commander, who was very unliked, took command. Being in maintenance, and her coming from a non-related career field (personnel or something), we always bristled when she said “We’re going to get those jets in the air!” Or something to that effect. I wouldn’t normally care, and would probably forgive the slight mischaracterization, but for someone leading us, to fail to make that distinction, was something we took seriously. $\endgroup$
    – Frank
    Commented May 3, 2018 at 20:05
  • 1
    $\begingroup$ @Pilothead, Thanks, it is indeed what I was looking for. I prefer to wait a few days to let extra votes trickle in. I think you'll find that my record for accepting answers is reasonable. $\endgroup$
    – user28387
    Commented May 4, 2018 at 12:51
6
$\begingroup$

No. CNN incorrectly reported that is was a jet. Most likely it was a staff writer with little background in aviation who posted the story in haste. Contact them and they’ll be happy to issue a correction.

The C-130 aircraft is a turboprop powered aircraft. To be fair, sometimes turpopropeller engines are called ‘prop jets’ because they use a gas turbine engine similar to the gas generator core of a jet engine to drive the propeller. While the gas core of a turboprop does produce some reactive thrust from the exhaust gases leaving the jet pipe or exhaust stubs, the vast majority of the engine power output is sent to the propeller gearbox and converted into thrust by the propeller.

Improve this answer
$\endgroup$
5
$\begingroup$

According to the manufacturer, Lockheed Martin the C-130 is a turboprop multi-role aircraft powered by Four Rolls-Royce AE 2100D3 4691 shp turboprop engines.

Since the manufacturer itself classifies the 130 as a turboprop, I would tend to lean in that direction.

The dictionary.com definition of a turboprop is "an aircraft powered by one or more turbo-propeller engines". Turbo-propeller engines are further defined as "a jet engine with a turbine driven propeller that produces the principal thrust, augmented by the thrust of the jet exhaust".

The major difference between turbofan engines and turboprop engines is that in the turboprop engine, the exhaust is routed across internal turbines connected to a shaft that then turns an externally mounted propeller from which most thrust is derived.

In a turbofan engine, that same exhaust is still routed across turbine blades attached to a shaft, but instead of spinning a propeller, the shaft spins a very large fan on the front of the engine and that is what produces the majority of thrust, at least in today's high bypass turbofan engines.

A great video can be found here that does a good job of explaining how a turbofan engine works and here is a good overview of the GE turboprop engine.

Improve this answer
$\endgroup$
0
2
$\begingroup$

Is it incorrect to refer to a C-130 as a jet?

Yes, it is incorrect.

First things first, let's go over some terminology. A "turbine" is a kind of engine used in aircraft. There are 3 variations of the turbine engine: turboprop, turbofan, and turbojet.

In aviation, the term "jet" is used to refer to turbojet or turbofan engines. There is probably no official definition of this term, but this is how it is commonly used.

Improve this answer
$\endgroup$
0
0
$\begingroup$

YES ! - It is technically correct to call any axial or centrifugal combustion engine a "Jet". The power originates from single cycle "jet" gas reaction but in the case of a turboprop or fan-jet is converted to other mechanical thrust.

The FAA Pilot's Glossary defines a Turboprop...

TURBOPROP AIRCRAFT− An aircraft having a jet engine in which the energy of the jet operates a turbine which drives the propeller.

Turboprop, turbofan, and turbojet refer to the manor in which the chemical energy is converted to mechanical thrust i.e fan, prop, or gas exhaust - not the combustion principle. All three use intake, compression, power, exhaust in what is commonly called a single cycle or "jet". Therefore they are all "jets".

A pure jet (turbojet) derives all its thrust from exhaust reaction. A turbo-prop or turbo fan translate the jet power to a prop or fan. A typical modern Aerobus/Boeing turbo-fan engine only produce about 10% thrust from exhaust reaction and 90% thrust from prop or fan propulsion! Mechanically a fan and a prop use the same mechanical principle for thrust, a prop has fewer wider blades that turn slower, while a fan has more thinner blades at a higher rpm.

A turbo-prop is a "jet" engine with a gearbox attached to a small number of blades (prop). The aircraft is primarily driven by the reaction of air through the "prop".

The "jet" used on Aerobus and Boeing (i.e fan jet) is a a jet without a gearbox but has at least one auxiliary spool and bearing that "slips" in place of a gearbox and drives a many bladed prop (fan).

The power producing "jet" of a jet, turbo prop, turbo jet, and turbo fan, primarily differ in the bypass ratio and rpm but the power is produced by the same "jet" single cycle combustion principle. A jet can be defined as a single cycle intake, compression, ignition, and expansion of combustible gas.

Improve this answer
$\endgroup$
3
  • $\begingroup$ While perhaps technically correct per the pilot glossary you quote, this answer goes against conventional wisdom. The C-130, and all turboprop aircraft, are commonly called turboprops, (not jets!) by everyone with credible aviation knowledge and experience. I believe that every place you put "jet" in quotes, a more appropriate term would be "turbine". Again, maybe technically correct, but not useful or accurate in common parlance given the context of the question, therefore I have downvoted. $\endgroup$
    – Michael Hall
    Commented Jul 24, 2021 at 17:20
  • $\begingroup$ Would you also call a gas turbine in a power station a jet? Like a turboprop engine, it is a gas turbine built to provide torque. One does it for a generator, the other for a propeller (and a much smaller generator). The purpose of a jet, however, is to accelerate a stream of working gas (such as air). Following the logic of your answer, a stationary gas turbine is also a jet. $\endgroup$
    – Peter Kämpf
    Commented Jul 26, 2021 at 10:01
  • $\begingroup$ @jwzumwalt, to your credit you drafted a well thought out response that has merits to it, it's just that your conclusion and root answer of "yes" is 180 out from every standard definition. And I think you were mislead by the AIM quote - yes, there is an internal stream of gas, or "jet", driving a power turbine, but the (turboprop) aircraft itself does not derive primary propulsion from it like a pure turbojet, or even turbofan engine driven aircraft does. (the ones that are correctly called "jets" for shorthand...) $\endgroup$
    – Michael Hall
    Commented Jul 26, 2021 at 16:14

You must log in to answer this question.