Inverted flying

An easy (?) explanation is that when the nose is pointed up the airplane will go up. This is true whether the airplane is right side up or up side down.

or read this
http://en.wikipedia.org/wiki/Lift_(force)

 

Another way of putting it is to visualize the airplane inverted with the tail slightly lower than the wing. This angles the wing against the wind, creating lift by deflection rather than lift by airfoil.

 

It's all about angle of attack. Many race planes and aerobatic machines have symmetrical airfoils so to produce lift, the wing must be at an angle to the airflow. Flying right side up, the wing is set at positive angle by virtue of being set that way on the fuselage (incidence) or by horizontal tail trim. Flying inverted, one must do the same thing, trim things so that there is an angle to the airflow that will produce a reaction in the direction that the pilot wants to go. Flying right side up with an airplane that has a positive cambered airfoil or a symmetrical airfoil, push forward on the controls and it will go in the direction that the pilot calls down. Roll the airplane inverted and push the controls forward the airplane will go in the direction that the pilot calls up. The airplane doesn't know up from down or sky from ground, the wing just reacts to airflow and produces lift. And even the positive cambered airfoil will produce lift when it is " inverted", it just ain't as pretty as it is right side up.
Now, if you understand all this gibberish, please write it down (or up) and send it to me so I can decipher it. Never know when somebody asks me about it again. I made it all up anyway.

 

what has been said only deals the aero aspects of a plane... not all planes are equipped for inverted flight, the various systems that guide and power a plane in normal flight may not be designed for inverted operation...one needs to read the fine print in the "how to" book on the design limitations before attempting inverted flight... a lot can be screwed up in a plane designed for normal flight

 

Here, I drew a picture:



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Of course, you should also evaluate how your engine performs when inverted.

During the Battle of Britain, British pilots had to be careful, because their carbureted Merlins would cut out when inverted, unlike the Germans' fuel-injected DB601s. I suspect that modern engines are less likely to have such problems.

 

They will if there is no inverted oil system. In the stock Stearman or equivelant you basically have a carburetor bowl's worth of gas for inverted flight time. At 14 gallons an hour it's not very long before it sputters from fuel starvation then you roll it around for another bowl fill up.

 

I thought about this aspect but the question was about the aerodynamics of inverted flight. When I saw the trailer about the new " Flight" movie with the MD80 type of airplane cruising by inverted, I immediately thought about all the systems in a big jet that would be totally messed up...fuel vents, hydraulic system reservoir, engine oil feed constant speed drive, cabin stuff, lavs,etc. When Tex Johnson barrel rolled the 367-80 he made certain that it was a 1G positive maneuver all the way around or there would have been some serious damage to the airplane. I can't remember what the max inverted structural load is on a commercial jet but it isn't very much. Gatorrari ?

 

Every transport category airplane I've been involved with had a structural limit of -1g. I think that may be a certification requirement.

I know NASA flies their 707s to 0g regularly, as do the guys in Florida with the 727. The Alaska 261 guys spent some time inverted, but I don't know how long they were inverted before the stab came off (which wasn't because they were inverted).

I would think the big question would be what the engines do. However, for a few seconds I'm sure there would be enough fuel in the lines to keep them running.

 

I should add that, after looking at the transcript, it appears that the engines quit on Alaska 261 after a short time inverted.