Why can you fly a Biplane upside down and not a Monoplane?

Question

This is one thing i have ALWAYS wanted to know.

Answer 1

Theoretically, almost any airplane can be flown upside down, but in practical terms, inverted flight must be limited to aircraft in the aerobatic category (as opposed to the normal, utility, or transport categories).

All of the answers above that say the fuel/lube systems are the reason any given airplane cannot be flown inverted are wrong.

Only aerobatic category airplanes can legally be flown inverted.  The difference is the construction of critical wing attachment points, the tail structure, and various stiffeners and extra bolts that make the airplane strong enough to take the "G" loads that occur in aerobatic maneuvers.

The difference in an aerobatic airplane is structural strength, not the fuel system.

If the airplane does not have a fuel and lubrication system designed for inverted flight, there is a limit (typically ten seconds) to how long the airplane can be kept inverted.

You will hear macho ballzo stories about "my cousin flew a Cessna 150 upside down."  Unless it was the aerobatic model, the maneuver was highly dangerous, and sooner or later will result in a fatal structural failure.

There was an aerobatic version of the Cessna 150, and also one of the Beech F33 Bonanza.  Sales were disappointing, and there were only a few made.

Airliners are strong enough to perform aerobatic maneuvers, but it is prohibited by the FARs and the owners.

Most competition aerobatic airplanes now are monoplanes, not biplanes.

Answer 2

You can fly ANY airplane upside down if the engine and fuel system is suitable (i.e., rated for acrobatics).  The Cessna 150 Aerobat is an example.

Answer 3

You can fly a monoplane upside down. (here's proof)

http://www.flickr.com/photos/-jon-/15115...

Answer 4

Any flying upside down restriction would due only to fuel and lubrication system limitations, not aerodynamics ones. While it is true airplane fly better right side up, there is usually enough aerodynamic margin before a negative loading stall occurs, so virtually any airplane can aerodynamically fly upside down.

Answer 5

HUH!. Any plane will fly upside down.  A Boeing testpilot actually rolled a jet passenger plane once.

Most stunt planes are monoplanes today and they have inverted oil and fuel systems for sustained inverted flight.

Answer 6

Who ever said that? You can fly many jets upside down. It uses a lot of fuel, and you can't fly upside down for more than about 10 seconds, but it is doable.  

Answer 7

Back in the days of biplanes, most had radial engines like the Stearman, etc. These engines had fuel and oiling systems that were supplying a round engine so they could be flown in any attitude. No a days we are using engines that were not designed the same. The aircraft has to be certified as an aerobatic aircraft to fly more than a few seconds upside down.

The early airplanes were actually overbuilt because aircraft design and engineering were just beginning to understand all of the science.

Answer 8

Ducks can`t fly upside down -if they did they would quack up

Answer 9

False premise.  All planes can be flown upside down, regardless of the kind of oil and fuel system.  Gliders fly upside down.  Hanggliders fly upside down.

Answer 10

Never heard that one before.  All planes can fly upside down.  Now, you may come across problems with the engine if it's not made to be flown in that orientation (fuel and oil), but physics don't somehow prohibit a monoplane from flying upside down.

Answer 11

You CAN fly a monoplane upside down.