does jet engine pull or push the plane thru the air ?

Answer 1

The corect answer to your question is a bit more complex than you may expect.

In physics, there is really no such thing as suction - there are only pressure differentials. What may appear as suction is really a greater pressure in one area than an other. Let's look at a vacuum cleaner - it is not really sucking, it is just creating a low pressure area by pumping air in the opposite direction that is filled by ambient pressure - the resulting movement of air moves the dust from your floor into the vacuum cleaner.

Now what do vacuum cleaners and suction have to do with jet engines? A jet engine "pumps" exhaust out the back. The exhaust is a mixture of fuel introduced in the "hot section" and air that came in the front (intake) to replace the air that was being consumed in the air-fuel combustion process. In a high bypass turbofan engine (which all modern jets use) the "exhaust" is a combination of hot burned gases from the "hot section" as well as unburned air that has gone through the bypass fans. The difference in the pressure between the rear of the engine and the front of the engine is called the "exhaust pressure ratio" or simply "EPR."

Therefore a jet engine definitely does not "pull" - but it also doesn't really "push" either. Only a small part of the thrust is a result of the pressure differential between the rear of the engine and the front of the engine.

The real driving force on a jet plane has to do with Newton's third law - for every action there is an opposite and equal reaction. That is why the power produced by a jet engine is measured in thrust and not horsepower.

Let's look at a Boeing 767-200, a plane that I am most familiar with. There are two turbofan engines that each produce about 63,000 lbs of thrust (the exact number depends on the type of engine, as there are several types available.) So, at full power, the aircraft can displace 126,000 pounds of exhaust rearwards. Newton's third law states that action of moving 126,000 pounds of air and exhaust must have a reaction, and the reaction is the plane moving forward.

Same principal on spacecraft - the rocket motor (essentially a jet engine except that it needs its own oxygen supply) exhausts its gases in one direction, and the spacecraft moves in the opposite direction. Clearly, there is no "pushing" or "pulling" in space, its Mr. Newton showing up again.

If that still doesn't make sense, imagine you are standing on a skateboard holding on to a large rock. If you don't move, the skateboard is not going to move either (assuming the ground is level and there is no wind). Now you throw the rock behind you. Where does the skateboard go? Bingo!

So the answer to your question is that the vast majority of a jet plane's thrust is the reaction to the exhaust.

I think "A Guy" is talking about something different from what you are asking. Most single engine planes (like a Cessna 172 or Piper PA28) have the engine up front, and that is sometimes called a "puller." A plane such as the Republic Seabee has the engine mounted on top, with the propeller behind the engine, and that is sometimes called a "pusher." Then there is the Cessna 337 "Mixmaster" which has one of each, and that is affectionately called the "Push me pull me!"

Answer 2

It depends on what you're asking. If you're talking about the jet engine's effect on the airplane respective to its position then it would depend where on the airplane it is positioned. If at the front (very rare) it would "pull" the airplane, and if at the back (common) it would "push" the airplane.

However, since the jet engine is a part of the airplane I don't like this explanation. More appropriately, the jet engine's THRUST pushes the engine forward which is attached to the airplane, thus causing forward motion on the airplane. However, since the jet engine in NO WAY is a force acting on the airplane, I would say it neither pushes nor pulls the aircraft. Maybe this is semantics, but to me the question shows a lack of understanding of how the airplane works in general.

Trebor: My statement about "Pull" had more to do with a simplistic view of the job of the engine. Like the wagon, if you are at the front you are "pulling" the wagon, whereas at the back, you are "pushing" it. However, you'll notice that I dismiss this answer as entirely too elementary. I didn't know what the question was he was asking, whether he was talking about engine placement (which could constitute a "pull" in his head) or simply the real action of the engine vis a vis the plane.

DJVC: I always learned it as "Suck, Squeeze, BANG, Blow". I find that way to be easier to remember since all of the words have similar double meanings.

Answer 3

Push Pull Plane

Answer 4

Everything mechanical is a "push"... The jet engine creates thrust and the engine is connected to the aircraft, so the engine is pushing the aircraft forward, regardless of how or where the engine is mounted. The wings provide the lift for it to fly through the air. But, anything mechanical is going to be "push"... there is no "pull" in things mechanical. (Think about it. If you're pulling a wagon, then your fingers are really pushing against the handle.) I think pulling is only possible with magnetics, electromagnetics and gravity.

Answer 5

Good question. I've never thought of it. To function, a jet engine needs to pull air from the front, then blow it out of the back, so there's a pull and a push involved.

But whenever I hear about engine power, it's always referred to in thrust, the amount of push coming from the rear of the engine. Maybe a jet engine pushes and pulls, but "thrust" is used to rate engine power because the engine's push is easier to measure.

Answer 6

Basically, a mix of both. The turbines of the jet pull air into its combustion chamber, thus pulling the aircraft slightly. Then, the now superheated air races out of the engine through the back, pushing the plane along.

Answer 7

A jet engine pushes a plane through the air with thrust coming form the rear of the engine. Air inters the front and is compressed by a series of rotating blades, fed through the combustion chamber were fuel is added and ignited, it exits through another set of rotating blades witch also compresses the hot gases and creates thrust out the rear. This second set of blades is what keeps the engine running.

Answer 8

Mostly push. The engine creates a lower pressure area in front as it ingests air, so some propulsive force arises from the engine being sucked into it. But the far larger part comes from the air exhausted behind, whose velocity has been substantially increased by the engine. The increased velocity gives increased momentum, and by Newton's law of reaction, imparts a push on the engine.

Answer 9

The engine definitely pulls the aircraft through the air, by pushing fast moving air out the back.

Think of it hypothetically this way, that if the engine was released from the aircraft while running it would accelerate away from the airplane.

Answer 10

jets work like this:

suck, squeeze, burn, blow

the intake [SUCK] of air inside is mostly taken care of by forward motion of flight [obliviously there is no forward motion on ground and as a precaution don't stand next to jet turbine intakes!]. in fact, at supersonic speeds intake air must be slowed down by variable geometry moving parts before hitting the compressor [SQUEEZE] blades, which can have up to 5 or 6 fan sections of blades. more oxygen equals more power. fuel is added to the mix to ignite the oxygen [BURN] and the rapid expansion is the thrust [BLOW] out the back of the engine.

that is about as simple as i can put it. hope that helps!