Is a vertical loop possible with a modern large airliner?

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Discussion Overview

The discussion centers on whether a modern large airliner, specifically a widebody jet like an Airbus or Boeing, can perform a vertical loop maneuver. Participants explore the theoretical and practical limitations of such an action, considering factors like thrust-to-weight ratio, g-load ratings, and aerodynamic control.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that while some widebody jets might be capable of a vertical loop, most cannot due to a low thrust-to-weight ratio.
  • Others propose that the main limitation is the low g-load design rating and insufficient aerodynamic control authority to execute a tight loop.
  • It is noted that the thrust-to-weight ratio of an "empty" A340 is about 0.6, which is better than many WWII fighters, but this does not equate to the maneuverability of those aircraft.
  • Concerns are raised regarding the elevators' ability to provide the necessary pitch control for looping, even if the aircraft could handle the g-forces.
  • Participants discuss the expected g-loading for a loop, estimating it to be around 3-4g for an inside loop.
  • One participant mentions that typical commercial aircraft are certified for -1 to +2.5g steady loading, which is significantly less than what aerobatic aircraft can handle.
  • There is a consideration of the loop's radius, suggesting that starting at cruising speed would require a large loop radius, which would decrease as speed drops.
  • One participant expresses that it should be possible if the fly-by-wire system allows for it, indicating a belief in the potential for such maneuvers under specific conditions.
  • A light-hearted comment suggests a belief that it might be possible, but without serious technical backing.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of a vertical loop with large airliners, with no consensus reached on whether it is possible or the specific limitations involved.

Contextual Notes

Limitations include the dependence on specific aircraft models, the assumptions regarding fly-by-wire systems, and the unresolved nature of aerodynamic control capabilities in this context.

d3mm
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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?
 
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Some might be able to but most cannot and the reason is a low thrust to weight ratio.
 
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!
 
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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.
 
What would the g-loading be? Around 3-4g? This is for an inside loop, of course.
 
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.
 
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That is what I thought. Given this, it should be possible if the fly by wire allows it.
 
I bet it would...

lol
 

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