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This subject has been partially covered before here Is it possible to do a barrel roll in a large aircraft like a B737? and here Is it safe to roll an airplane that isn't approved for it?

If a airliner such as say a 777-300 had enough height, could it theoretically do a loop or similar aerobatics?

I am supposing that there is no passengers, luggage, hostesses and minimum fuel on board etc - so minimum weight.

Also, taking into account the loop - if it couldn't achieve the loop by pulling up - could it achieve it by going nose down instead?

IE: The aircraft goes nose down till it is upside down then pulls up - a mirror version of a normal loop basically.

The other questions go over the reasons why not to roll a large aircraft, I want to know if other aerobatics (specifically loops) are theoretically possible.

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    $\begingroup$ You'd have to disable the envelope protection first though. $\endgroup$ – ratchet freak Jun 2 '15 at 11:12
  • $\begingroup$ Not a duplicate I think - the question is asking specifically about either inside or outside loops, which have different limitations. $\endgroup$ – Andy Jun 2 '15 at 11:40
  • $\begingroup$ @PeterKämpf the others only go over rolls - I want to know about other aerobatics - specifically loops $\endgroup$ – CalvT Jun 2 '15 at 11:53
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    $\begingroup$ NOT a duplicate question, because the answers are different! Roll, yes, it's a 1-g maneuver. Loop, likely no because of the higher g-loading. How in the world is that a duplicate question??? $\endgroup$ – Ralph J Jun 2 '15 at 13:34
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    $\begingroup$ Read up on Federal Express Flight 705. When a crew member attempted to murder the pilots and crash the plane (a DC-10), the pilots (who were former Navy/Air Force) basically used the aircraft as a weapon to throw the hijacker about the plane and keep him incapacitated. It's an amazing story! There's a Seconds From Disaster episode on it too. $\endgroup$ – JMK Jun 3 '15 at 13:42
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Design

The key point is that these vehicles are not designed to perform such maneuvers.

A coast-guard lifeboat is designed to self-recover from a capsize and can roll through 360 degrees without significant structural damage. A cruise-liner would not survive being rolled over completely.

If a vehicle is not designed to perform a high stress maneuver it is safe to assume an unmodified vehicle cannot do so without incurring severe damage.

Inside loop

Regarding an inside loop, the world's smartest man says

Looping a 747 or a DC-10 would be trickier [than rolling one ...] Boeing suspects its planes could make it, but since no one has ever been silly enough to try, there's no way of knowing for sure.

Outside loop

An outside loop is much much more stressful on airframe and pilots as it involves negative G. Airliners have flight envelopes that have much less capability under negative G. There must be a very high probability the aircraft would break up when attempting an outside loop.

Roll

A barrel roll is a less stressful maneuver.

60 years ago, in 1955, "Tex" Johnston, a Boeing test pilot performed a barrel roll in a Boeing 707. So far as I can find out, no one has since deliberately attempted to replicate this stunt in a commercial airliner. At the time of publishing his autobiography, the pilot claimed in a newspaper report that the stunt was planned by him but unknown to his boss.

in 1985 China Airlines 006, a 747, inadvertently executed a half roll but suffered structural damage. It rolled to 60 degrees before the pilot disengaged the autopilot, the pilots suffered spatial disorientation and the roll continued into a dive. The pilots obviously weren't flying the aircraft within its limits - meaning you can't read a lot into this, other than it might be easy to break up the aircraft while attempting this sort of maneuver.

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    $\begingroup$ Note that the same article states: "there once was a Boeing test pilot who, in a moment of frivolity, took it into his head to execute a barrel roll in a 707. He made it" and then regarding the 747 (not 707) "The consensus at Boeing seems to be that a 747 would probably survive a barrel roll" $\endgroup$ – Fattie Jun 3 '15 at 4:15
  • $\begingroup$ @JoeBlow: Barrel roll is special in that it is low positive G throughout and the only unusual condition is moderate amount of side-slip. So it does not put too much stress on the airframe. $\endgroup$ – Jan Hudec Jun 3 '15 at 7:37
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    $\begingroup$ @JoeBlow: IIRC the barrel roll in 707 was some demo, so the "moment of frivolity" was more like "we can't obviously approve it, but it would be cool, so we are going to pretend we don't know what you are planning". $\endgroup$ – Jan Hudec Jun 3 '15 at 7:39
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    $\begingroup$ A German registered 707 crashed in 1964 on a training flight during an attempt to fly a (barrel?) roll. Apparently one roll was successfully completed, but crew lost control of the second one: aviation-safety.net/database/record.php?id=19640715-0 $\endgroup$ – Cpt Reynolds Jan 13 '18 at 21:30
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    $\begingroup$ @CptReynolds To be pedantic: that accident was a Boeing 720, not a 707. $\endgroup$ – MichaelK Aug 20 '18 at 6:12
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Probably not, due to structural strength issues. A barrel roll is one thing; they can be performed at a positive load factor through the whole maneuver (assuming sufficient control authority).

Loops on the other hand will need much greater loadings in the "fast" portions in order to keep the loop "round" and to allow the maneuver to be completed without stalling.

Inverted loops are even more extreme as the aircraft is accelerating into the maneuver, requiring potentially greater loads on the airframe.

Outside loops... might as well forget it, the negative G-Loads are more or less guaranteed to cause an airliner airframe to fail; negative Limit Load Factor for Part 25 cert requirements is -1 G and Ultimate Load Factor is -1.5.

Who knows, maybe Boeing over-engineered enough to allow a 74- to take the 4+ Gs it would need to in order to complete a loop, but I'm skeptical they could build that much strength into the structure, for weight reasons if nothing else.

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It's going to be hard to provide a hard answer, because it would vary from aircraft to aircraft. But, let's take a Boeing 737 as a reference, simply because it's quite common, and small(ish), so one would assume it would be more likely to survive than a larger jetliner.

According to this guide on executing a loop (pdf), you want to maintain roughly 3.5 positive g's when executing a loop (and this is best case, in the hands of an experience pilot.) Bearing that in mind, Boeing lists the maximum positive g's for a Boeing 737 at +2.5g (with flaps retracted). Which leaves us an entire unit of earth's gravity short of being able to safely execute the maneuver.

So, in the case of the 737, the answer is a resolute no. And I think it's safe to assume that most commercial aircraft are not much stronger (In fact, in doing some more checking the Boeing 747-400 and the Airbus A320 have the exact same g load characteristics, here and here respectively.)

So we can probably assume that no commercial jetliner can safely handle a loop.

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    $\begingroup$ The 2.5G seems to be certification requirement. And designing the plane stronger makes no sense, it would make it heavier. $\endgroup$ – Jan Hudec Jun 3 '15 at 7:52
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    $\begingroup$ +2.5G is the positive Limit Load Factor, i.e. high risk of permanent deformation of the airframe if exceeded. The Ultimate Load Factor is 150% of the LLF and also part of certification requirements; the danger in exceeding it is that there is a substantial risk of outright airframe failure. $\endgroup$ – habu Jun 3 '15 at 12:42
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    $\begingroup$ There was an incident where a B757 unintentionally flew a 3.5G manoeuvre without serious damage - in fact it was allowed to remain in commercial service for several months afterwards without a technical inspection, until Boeing did some further analysis of the flight data recorder. See "Icelandair Flight 315" at en.wikipedia.org/wiki/Icelandair#Accidents_and_incidents $\endgroup$ – alephzero Aug 3 '15 at 19:43
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    $\begingroup$ @alephzero Nifty, nice find. Though, as always, I feel obligated to point out that "one incident doesn't make a sample size". They were probably lucky more than anything else... $\endgroup$ – Jay Carr Aug 3 '15 at 20:04
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Airplanes can sustain more positive G forces than negative G forces because of their construction. Your described opposite loop is only for very advanced aerobatic airplanes and pilots because negative G forces are involved. I think normal loops are possible if performed by a skilled pilot like a test pilot, but are too risky or too expensive (in case of failure) to try. A Boeing 777 costs $300 million. Who will want to over-stress an airframe that costs millions just for a loop?!

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They are not designed for aerobatics. Design limit loads of 2.5g are too low for performing inside loops. Ultimate load is 1.5 times limit load = 3.75 g, which could be enough for an inside loop if expertly done, eating into the safety margin and playing with structural failure and death.

But that is with a standard plane, at full load. An aeroplane specifically kitted out might be able to do an inside loop:

  • The best candidate would be a shortened version of an aircraft, like the B747SP or the F70: wing loading is less than design load which results in additional g tolerance.
  • Structural loads on the wings could be reduced further by installing tip weights.
  • The aircraft must be stripped of all unnecessary items such as passenger seats to make it as light as possible.

The manoeuvre loads should be kept inside the limit load, leaving the 1.5 factor to the ultimate load as the safety margin it is intended for. It should be possible to achieve an ultimate load of around 6g (limit load of 4g) for a modified plane, given what happened to China Airlines flight 006. Flight control authority needs to be verified, and all structural elements including the tail, fuselage, flight control surface hinges etc. that were designed to the same loading specs will need to be scrutinised and possibly modified to make sure they don't fail at the higher load.

But with such a modified plane and an expert pilot, it should be possible, yeah.

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Check out Tex Johnston's 707 prototype barrel roll. While it isn't large by today's standards, it did involve a plane that became an airliner.

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    $\begingroup$ Tex's barrel roll was the first thing that came to mind when seeing this question. This is a classic moment of aviation history. $\endgroup$ – J... Jun 2 '15 at 15:10
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    $\begingroup$ Tex Johnston's (note spelling) barrel roll is implicitly acknowledged in the question by linking to other questions that discuss it. The question specifically asks about "a loop or similar aerobatics" and, as the other answers point out, a barrel roll isn't at all similar to a loop. $\endgroup$ – David Richerby Jun 2 '15 at 16:28

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