Is a vertical loop possible with a modern large airliner?

[d3mm]

I have asked many times this question to many people and have many different answers:

Let X be a widebody jet airliner like an Airbus or Boeing, larger than a typical business jet. Can X do a vertical loop manoeuvre? If X cannot, what is it that stops X?

 

[russ_watters]

Some might be able to but most cannot and the reason is a low thrust to weight ratio.

 

[AlephZero]

I suspect the main limitation is the low g-load design rating and the lack of aerodynamic control authority to fly a tight loop. The thrust/weight ratio of an "empty" A340 for example is about 0.6, which is better than most WWII fighters. (Note that the dynamic thrust from a propellor is less than the static thrust at zero airspeed)

But you can't throw an A340 around the sky the same way as a Spitfire - even if you override the computer system that stops you from trying!

 

[marty1]

Even if an airbus could handle the g force and you could bypass the computer, I doubt the elevators have the degree of freedom (or surface area needed) to pitch the aircraft to the point of flying in a loop.

 

[d3mm]

What would the g-loading be? Around 3-4g? This is for an inside loop, of course.

 

[AlephZero]

A typical commercial aircraft wuld be certified for -1 to +2.5g steady loading. (Of course it will withstand more than that for transient loads like air turbulance, heavy landings, etc)

To put that in context of doing aerobatics, it's about half as much as a first world war biplane can handle.

Assming you start at the bottom of the loop at crusing speed (mach 0.85), I make the loop at that speed radius about 11,000 ft for 2.5g. Obviously the radius would decrease as the speed drops, but it's still going to be a very big loop.

The WWI biplane also wins the aerobatic contest because its stall speed is probably about 25kt compared with 125kt for the airliner, which also makes a very big difference to what's possible.

 

[d3mm]

That is what I thought. Given this, it should be possible if the fly by wire allows it.

 

[Mithrandir13]

I bet it would...

lol