Can a passenger jet do a loop the loop?

Answer 1

legally no - safely and ethically no - technically most large passenger jets no though a few might if done very carefully with minimal fuel and no passengers (in otherwords as lightly loaded as possible)

planes are certified for certain flying conditions based on the forces they are designed to withstand - the stronger a plane is built the heavier it has to be - the heavier it is the less payload (cargo and passengers) it can carry - passenger jets need to carry as much payload as possible so are built as light as safety permits which means no sudden or severe forces are allowed or damage will result (such as the Chicago ohare crash quite awhile back where the copilot made several sudden rudder movements that caused the tail section to break off)

a loop requires a fast speed when first entering since the speed drops rapidly as altitude is gained - otherwise the vertical altitude gain would have to be done entirely by the engines and as powerful as the big jet engines are they don't even have the power to hold it still let alone push it up like a rocket - problem is the heavy jets need to be doing a very fast speed, at least 400 to 600 mph to start the loop to have enough speed to finish it - which means any sudden change in vetical speed puts a huge force on the already very heavy wings - going up at a steep rate of climb for a loop at say 500 mph will rip the wings off almost any heavy jet

next problem is descending from the top of the loop where the weight of the plane can cause it to overspeed since the heavies don't have airbrakes and you cant reverse thrust at those conditions without ripping them apart and flaps are too weak for those forces to use as breaks - when a plane reaches its maximum speed it startes vibrating/shaking and would eventually shake itself apart

all this said it may be possible for some of the smaller jets (737 etc) under controlled conditions and a bit of planning to be able to loop - i don't know if its ever been tried but it may be possible - but then the plane would probably not be airwothy anymore due to the stresses it undergoes so its not likely any one will try it with a multimillion dollar commercial aircraft - wonder if anyone wants to risk their personal 737?!

Barrel RollA barrel roll is when the planes flies on one heading and rolls over upside down as if the a/c is rolling inside a barrel. Test Pilot "Tex" Johnson barrel rolled a Boeing 707 airliner.

Link to a video of this event:

http://www.YouTube.com/watch?v=Ra_khhzuFlE

During the hi-jacking of a FedEx cargo DC10-30, the flight crew rolled the a/c almost inverted in order to throw the hi-jacker off his feet, while he was fighting one of the crewmembers.

Reference "Hijacked" by Dave Hirschman

Answer #3

Probably at least some of them could. It might not be a classic, circular loop, but with the right entry speed and enough altitude it probably could be done. Of course you'd have to find someone willing to risk a $40M+ airplane (in the case of a 737; more for larger airplanes) on a rather stupid stunt, and also a pilot willing to fly it.

Of course, the airplane manufacturer would probably have a fit over the liability issues . . .

Airshow pilot Bob Hoover used to do such stunts with Aero Commander 500s and Sabreliners; it should be possible with even larger airplanes. YouTube has a video of Bob Hoover looping his unmodified, straight-stock Commander 500--with the engines shut down:

http://www.youtube.com/watch?v=9ZBcapxGHjE

During his routines he never exceeded 2Gs on the airplane, which is well within the certification limits of all transport-category airplanes. Looping an airliner should be possible without damaging the airplane. It's just the thought of what might happen that's kept anyone from actually trying it.