three flags 747

[forufes]

it was possible in flight simulator 95.

our fluid mechanics professor says it isn't.

well?

[InigoMontoya]

Hard to say even assuming flight computer would allow it (or could be over-ridden). Limiting factors are likely to be structural.

 

But it is worth noting that a

. Edited January 4, 2011 by InigoMontoya

[insane_alien]

i think the limits are on its manouverability rather than structural. It doesn't have the control surface area to rotate fast enough to make it over. you might get up to about 80 degrees or so but by then you'll be going so slow you'll be in a stall. but, i suppose if you replaced the engines or added some larger control surfaces it would be possible.

 

the structural integrity of the 747 would be more than sufficient. you can perform loops without ever broaching 1.2g.

 

and a note of curiosity, i think 2 (at least one anyway) 747's have been measured going over mach 1 albeit while crashing.

[tomgwyther]

Probably not. The 747 is quite a big bird and so manoeuvres quite slowly. From level flight at full thrust; the weight of the plane pulling it down would exceed the thrust pushing it up. as Insane Alien said, 'It would probably get to about 80 degrees and then stall.

 

A 747-400 weighs about 600,000 lbs

All four engines at full throttle generate about 250,000 lbs.

 

That said, you may be able to generate enough airspeed by angling the nose down 45 degrees, then at full throttle, pull up sharply. This might give you enough momentum to perform a loop, or maybe an angel-fall*

Rather like a roller coaster going downhill before a loop. IIRC this is how you perform a loop in a glider also.

In any of these scenarios; I'd want a free upgrade afterwards!

 

 

Angel-fall - When a plane flies vertically until it stalls, then bank hard left (or right) rudder to fall over sideways and fall nose first

Edited January 5, 2011 by tomgwyther

[forufes]

actually my professor brought it up when we were studying external flows, the specific case of an incompressible flow over a horizontal flat plate.

sigh, before i go any further, anyone knows anything about boundary layers?

if yes then he[the prof] reasons that by increasing the tilt angle of the wing the separation layer will come closer till it engulfs the whole area of the wing and the flow becomes fully turbulent.

i think he might be wrong because the angle of tilt is[i think?] relative to the mean wind direction.

[tomgwyther]

i think he might be wrong because the angle of tilt is[i think?] relative to the mean wind direction

 

I'm inclined to agree with you, as the wing's leading edge would - more or less- always be facing the direction of airflow; as in the glider/roller coaster analogy.

With regards to the 747, it seems the control surfaces would be insufficient to pull the aircraft into a tight enough loop; and the airspeed, too slow to maintain low enough Re.

In my limited understanding of boundary layers; the turbulent far exceeds the laminar when performing aerobatics in large aircraft. Unless you have a very fast jumbo-jet with enormous elevators.

Edited January 5, 2011 by tomgwyther