Why doesnt an aeroplane have a reverse gear?

Question

Why doesnt an aeroplane have a reverse gear?

Answer 1

Because aircraft engines only turn one direction and the only gears are to reduce the prop speed on prop driven aircraft.

Helicopters have transmissions though, and they are used to change the angle of the power from the engines, because the engines don't line up with the rotor shaft.

Although they don't have a reverse gear in the same sense as your car, jets with thrust reversers and prop driven planes with reversible pitch props can back up.

Answer 2

If you're speaking of moving on the ground, aircraft wheels aren't gear driven like a car and they don't have a geared transmission like a car. The wheels just carry the aircraft along while the engine(s) motivate it.

Some aircraft do have the capability of going backwards on the ground. Jets with clam shell type thrust reversers can do it. The pilot activates the thrust reversers and they redirect engine exhaust slightly forward, pulling the aircraft backwards. Years ago it was an acceptable procedure for a such a jet to powerback off the terminal gate while being guided by the ground crew, but I haven't seen that done in 14 years.

Also, some propeller driven aircraft, such as the C-130 transport, have reversable propellers and are capable of going backwards on the ground.

Answer 3

To back out of a gate, an airliner has a tug push it out, and if you've seen an airplane, not a helicopter, going backwards, it's considered a maneuver. Wings are designed for lift while the aircraft is going forward.

Answer 4

First of all there is no need for it to go backwards. Yes from the gate in airport it goes back a little bit, but it is not done by the aircraft itself. Rather it is 'pushed' back.

Moreover as someone has mentioned here it is designed to fly forwards, so while in flight, it is totally ruled out to move backwards.

And 'reverse gear', it doesn't have a gear at all for its movement :-) I mean to say the wheels are not powered.

Answer 5

Some do:

http://youtube.com/watch?v=DZSs_Fmyvx4

http://youtube.com/watch?v=ZwDkhHNRQiE

http://youtube.com/watch?v=qgCUQ51oGhE

http://youtube.com/watch?v=pG_6tABPMHk

Answer 6

1. They don't need one...are they parallel parking or something?

2. Wings and tail surfaces are designed to work in a forward direction only (see #1). If airplanes had two-directional lift surfaces, where would the flight controls (ailerons, elevators) be located?

3. In a sense, some airplanes do have a "reverse"- thrust reversers - that are deployed after landing to help slow the aircraft down. They are not used for taxiing or gate pushback.

Answer 7

Due to aerodynamics and the way Aircraft are designed, having the ability to reverse might cause the Aircraft to tilt backwards if an Aircraft tried to reverse. But Airplanes do have thrust reversers which are used for slowing down the plane, not moving backwards.

Answer 8

because it defeats the principles of "flying"

planes fly "forward" they only go backwards to leave the gate and they are "pushed back" by that funny looking tractor thing while a guy directs him with hand signals.

they just have no reason to go backwards on their own.

Answer 9

I think they do.  How do they back out from the departure gate?

THERE is not always a "tug".  Once the pilot said, "I think one wheel is stuck in a hole, or one brake is locked.  I will try to POWER out of the hole.  If that doesn't work, we will be delayed for a while". unquote.

EDITED:  after receiving 6 thumbs down (thank you) I have read a lot on the subject.  Now I understand, "POWER OUT" of the hole.  I understand why reverse thrust isn't allowed, or safe at the departure gate.

Sources below for reading.  I will definitely VOTE for best answer here, now that I am better informed.

Answer 10

the airplanes do not have powered wheels, so they do not need any reversing "gear" like in the car. of course they have means to propel the aircraft backwards, but this is done through various powerback gadgets like negative proppeler pitch or thrust reversing.

Answer 11

The engines themselves are never geared, so theres no "reverse" Theres also no "forward" gear.  There is just an engine that spins a shaft (or two or three) on which either propellers or compressor fans are attached.  Some have the ability to thrust backwards, some don't.

On turboprops, the ability to tilt the propellers backwards is usually installed and helps slow the plane down after landing.  This is sometimes referred to as "Beta" (I don't know why it just is)

The propeller is connected directly to the engine's power supply.  However, the blade pitch is changed and can be tilted to a negative value, effectively thrusting backwards.

In jets, the fast-moving jet air coming out of the back of the engine can be ducted or deflected to act forward, also allowing the plane to slow down.  This is known as "thrust reverse."

Nowadays, most planes never  use this to actually back up.  They get pushed back or just drive away.  Reverse thrust kicks up a lot of dust and debris that could be ingested into the engine causing damage.  Reverse is almost never used at low speeds for that reason.  It is possible, but due to the danger of hitting things or damaging the engine, no companies currently allow it.

Answer 12

Would you believe I have seen a aeroplane flying in the air, motor going, and going backwards. This is true.

Answer 13

Lots of goofy ideas above, and a couple of correct answers.

Jet airliners have thrust reversers, used to slow down after landing; in some cases these can be used to move backward on the ground.

Many propeller driven airplanes have reversible pitch propellers that can be used to slow the airplane during a steep descent or after landing.  A propeller that can be reversed in flight is called a "beta prop."  It cannot be used to fly backward.

Reversible pitch propellers can be used to taxi backward.  The problem with pushing back in any airplane, of course, is that the person at the controls can't see where she is going.  So trained crew members on the ground and good hand signals are essential.

No airplane can fly backward, except as an occasional stunt that depends on having a strong wind.

We used to back our DC-6s and Convair 240s routinely.  I actually backed a DC-6 into a hangar one time, with about six guys giving hand signals outside.

So if that satisfies you that airplanes have "reverse gears," you are now better informed.

Have a great day, and rejoice in the memory of the golden age of aviation.  (Wasn't that long ago.  I was there, and I am still alive.)

Answer 14

Its aerodynamic design would rupture if flown against the wind. It is more practical for an airgoing vessel to just 180 and turn around, than to design it in such a physical way so as to make it "twin-tipped."