We all know that heavy planes like B777, A340 etc. cannot fly initially @ FL410. BUT: Is it possible, with....

Question

..... enough speed (and i think the speed must be above Mach 1), and maybe with an increased angle of attack, that the plane can make this altitude?

(Because, when going higher, the air gets thinner, but with an increase in speed and angle of attack, you could make it)?

Answer 1

Big planes can fly at high altitudes (witness the SR-71), but the aircraft you're talking about are designed to get people from point A to point B as cheaply and efficiently as possible, and they fly at the altitudes at which they are most efficient as far as lift, drag and fuel consumption are concerned.  Don't ask a plane to do what it's not designed for.

Answer 2

Anything can theoretically fly at ALMOST any speed or altitude. The limitation is in the materials, the technology, and the business logic that must be conformed to for this performance capability to be of practical value.

There are a few things to consider...

1. Compressibility of air - Lift factor. This is the most significant factor for a heavy aircraft. A propeller and a wing are both airfoils and therefore have certain things in common. There is a limit to the amount of thrust/force that can be efficiently generated by both. There comes a point where if the air is too thin you cannot get enough lift using an  airfoil of a fixed size. This is the case with a heavy 747. You would have better luck putting vertical rockets on the 747's wings or making the wing surface area MUCH larger than they already are (looking more like a Concorde).

2. Compressibility of air - Thrust Factor. Generating enough thrust, to generate enough speed, to generate enough lift to carry a heavy airplane HIGHER in thinner air is not just an uphill battle. Its almost vertical. Don't be surprised if increasing power output by 50% still doesnt result get the results you want. You could even carry the plane into the supersonic realm of flight and STILL not have enough lift.  

3. Compressibility of air - Maneuvering. If the air is thin and the aircraft is heavy enough, controlling the airplane will become an even bigger nightmare.

The point is that if not designed for all this the airplane will fall apart, dreaming of something it just wasnt designed to do. You are basically talking about a CONCORDE the size of a 747.

Answer 3

It was talked about prior to the B747, back in the 707 days.

First couple answers say it best.

Answer 4

You can fly the 777 at FL410, but it has to be much lighter than maximum takeoff weight. It's not a matter of engine power or speed. it's safety and economy that has us flying at lower levels. At heavy weights (long flight--lots of fuel) it takes more thrust to keep the jet flying at higher altitudes. More thrust = more fuel burned = high cost.

The main factor, though is that the low stall speed of the wing gets very close to what's called the Mach stall speed. At heavy weights and high altitudes, these 2 speeds may be only a few knots apart. That means if we speed up a bit...or slow down a bit...the wing will stall.

Air carriers usually dictate a minimum "spread" between these two speeds for their operations. We use a chart to determine what weights will give us the spread at what altitudes.

Hope this hasn't confused the issue.

Answer 5

flydog_3 is right.

Add more engine thrust, and the next thing you know you can carry more people on it, then you're back to square one.

Answer 6

increasing speed is not possible due to the ENGINE limitations the planes reaching their ceiling are loitering between minimum and maximum speed which in fact are equal when on ceiling level. the engines cannot give more output so the plane cannot fly any faster.

as for the higher AoA, the angle of attack produces more lift only to a certain value behind which the turbulent flow accurs and the wing stalls.

if the plane is not able to reach such altitude by normal /aerodynamic/ means, it can still be driven there dynamically... you fly as fast as you are allowed i the horizon, then pul up.. breach the ceiling level, and the plane stiill dynamically rises - like a balistic rocket. as the speed drops the plane would eventually reach the zenith of the curve and turns downdards, to the earth.

our air force had been doing that with the jet fighters in the past, it was some kind of aircraft interception technique.

I doubt that airliners are sturdy enough to fly such maneuvers.

Answer 7

To be able to get that high, they will have to upgrade the engine so that it can operate at that altitude. The engines they have on there are not designed function well at that altitude and speed.

Simply if you want a B777, A350 etc to go that high and fast, upgrade engines, strengthen structure to withstand all aerodynamic forces that come with high speed, and then you will be up there before the company goes broke due to cost.

Answer 8

Thudley's got it spot on. He's describing what's known as the "coffin corner." This phenomenon was stumbled upon when Boeing came out with the B-47, and there are some pilots flying RJs today that have no clue as to what it is.