Why dont paasenger planes have bigger engines? Ive seen videos of planes struggling at take off and crash. Maybe more thrust would help?

Maybe add some small emergency rockets to provide lift in case of emergency

Best Answer:

vic: I take it don't fly much?

Modern airliners have PLENTY of power, and a twin engine jet can still take off with just one engine. So it already has 2X the power it actually needs to get airborne.

You are watching a video and thinking "Meh, that thing is slow". When you are sitting in the back of an A380 and the pilot opens iit up for take off you are physically pushed back into your seat. By the time the place rotates you are doing about 170mph.

But when you watch that video, it seems to be "struggling" and barely moving. It's just an illusion due to the size of the plane. You are still sitting there being pushed back in your seat.

So any crashes aren't caused by lack or power. They are mechanical failures (more serious than a simple engine failure). Bird strikes that take out both engine (Hudson river crash) . Pilot error, (forgot to set the flaps for take off or used the wrong runway). Ice on the wings ( no lift) Control surface failure etc. None of those things would have been avoided by simply fitting more powerful engines.

Other answer:

I'd love to know where you are seeing these videos. Airliners have more than enough thrust to avoid "struggling at takeoff".

In fact, every time a jet takes off, the pilot has calculated the balanced field length. He or she knows that the if one engine stops at the worst possible moment, the plane will ether be able to stop on the remaining runway or continue the takeoff and have adequate climb performance with only the remaining engine.

If you see a plane "struggling at takeoff" some thing else is wrong, its not a lack of thrust.

Vincent G:
Because bigger engines weight more and consume more fuel.
The higher thrust would also require reinforcement of the structure, making the plane heavier still. And since you have a bigger plane at that point, one would be tempted to have more payload.
Which is basically what we engineers do when asked to design a *bigger* plane.

The art of engineering is making things the *right* size.

Passenger airplanes (= airliners) have sufficient power with their engines –
Airline pilots know exactly what the maximum weight is on a runway they takeoff from –
They find that in the airplane performance pages, or publication called "runway analysis" –
So. for runway length X meters-long, X temperature, X altitude they know the maximum weight –

Airlines operating at high altitude airports, warm temperatures have engines with more power –
That is an option that an airline has when they order new airplanes –
When I was flying 727, we had 14,500 lbs/thrust engine, max takeoff weight was 169,000 lbs –
But Mexicana or Sterling had 727 with high power, 17,500 lbs/thrust, max weight 210,000 lbs –

The first 747 types I flew (the oldest) had 46,000 lbs/thrust per engine –
The last type of 747 I flew had 53,000 lbs/thrust engines –

So you see, there are "options" for more power with the "same engine" –
If you look engine specifications, it is indicated by different "dash number" on the designation –
For the 747 I mentioned, old ones 747-121 had JT9D-7A, the 747-287 had JT9D-7Q –
Max takeoff for the 747-121 was 734,000 lbs while the 747-287 could takeoff at 833,000 lbs –

And airlines also use reduced takeoff power when full power is not needed –
So they save on wear and tear when using reduced power –

What idiot on "Youtube videos" would takeoff with ICE ON THE WING ?

There are airliners equipped with JATO rockets for additional power in case of engine failure –
The Mexicana 727 were so equipped –

I think many of these take off crashes are caused by pilot error such as forgetting to set flaps, overloading the aircraft, blocked pitot tubes giving false speed readings are quite often the causes of these accidents, but bird strikes and engine malfunctions just at the wrong moment can be disastrous but thankfully is quite are quite rare.
You can strap all the f^&*()_ engines on a car and it still won't fly without an airfoil, just like a plane with ice on the wings.
More thrust helps in the bedroom too
Not sure why.