F1 Car upside down - What about planes?

[Ken H.]

The other thread about an F1 car on the ceiling reminded me of a similar thing I’ve never quite understood – how can a fixed wing airplane fly upside down? I understand how the pressure delta across the upper vs. lower surface of the wing creates lift, so how can it work when upside down?

[David]

The attack angle of the wing is altered. Lots more drag, but that creates the lift.

[smiller]

Also there are some considerations in airfoil design that make inverted flight easier. Some wings are asymmetrical (more rounded on the top side than the bottom) which tend to be more efficient and stable in flight and others are symmetrical (rounded on both sides) which have less inherent stability and efficiency but perform well in aerobatic flight since they create equal (or at least closer to equal) lift in either orientation. For example a trainer/general purpose airplane such as a Cessna will have a fairly asymmetrical wing while an aerobatic plane such as a Pitts will have a symmetrical wing design. There's a lot more to it of course but that's one basic element.

[KDeline]

Shouldn't you be riding?

[Mike05]

Shouldn't you be riding?

 

He's got a point, especially before winter sets in!

 

Think come January you & Donna need to come visit us in Texas!

[Joe Frickin' Friday]

The other thread about an F1 car on the ceiling reminded me of a similar thing Ive never quite understood how can a fixed wing airplane fly upside down? I understand how the pressure delta across the upper vs. lower surface of the wing creates lift, so how can it work when upside down?

 

In straight/level flight, the plane is pushed away from the ground because the wing shoves air toward the ground. Roughly speaking, if the trailing edge of the wing is closer to the ground than the leading edge, then air gets shoved toward the ground. So if you want sustained inverted flight, then you roll the plane over and adjust the aircraft to a slightly tail-down position (i.e. tail closer to ground than nose). As Seth noted, the typical aircraft wing is optimized for right-side-up flight and will be less efficient at negative angles of attack, but an aerobatic plane sacrifices some right-side-up efficiency in order to have reasonably good performance even in inverted flight.

[John Ranalletta]

In straight/level flight, the plane is pushed away from the ground because the wing shoves air toward the ground.

Hmmmm...

 

I thought lift was provided by a Bernoulli effect rather than wing pitch.

[David]

Lift is technically more created as the wing is sucked into the vacuum created by less dense air created by spreading the same volume over a longer distance at the top of the wing.

 

Wings take their shape mainly to minimize drag. If all we cared about was lift, you can just change the angle of attack. It's the chorded distance that matters, created by a shape with maximum efficiency.

 

That's why rear flaps or front slats are merely temporary changes in the shape of the wing. Very inefficient, but good to accomplish something more important than fuel preservation.

 

Flying upside down with the same wing shape that is optimized for non-inverted flight is going to burn lots of fuel because of the angle of attack required to create enough differential in the chorded distance.

 

Now even I'm bored.

[tobyzusa]

This is an interesting read. Here's, a related but different question. The other day I was watching model aircraft flying. Several of the helicopter pilots would invert their craft and leave it stationairy, so obviously, there cannot be an attck angle factor. So in this case, would the answer be symetrical rotor blades? It was very cool to watch, but I was perplexed as to the physics involved.

[Boffin]

Rotary wing angle of attack is controlled by the rotor controls, not aircraft attitude. The model helocopters would have to have a lot of 'down' on the collective to achieve that - more than you find in real choppers.

 

Andy

[Steve1962]

The other thread about an F1 car on the ceiling reminded me of a similar thing I’ve never quite understood – how can a fixed wing airplane fly upside down? I understand how the pressure delta across the upper vs. lower surface of the wing creates lift, so how can it work when upside down?

 

I can provide the most scientific , well tested answer to this question .........

 

Paper aeroplanes fly upside down , therefore so can real ones ..........

 

I'm just off now to be Superman ..........

 

Steve

[John Ranalletta]

...but, doesn't flight (inverted or not) depend upon having lower air pressure above the wing than below regardless how that's achieved, i.e. wing design or angle of attack?

[David]

...but, doesn't flight (inverted or not) depend upon having lower air pressure above the wing than below regardless how that's achieved, i.e. wing design or angle of attack?

 

Yes, it does require a differential air pressure, which requires a differential in distance. But...

 

How the WING itself achieves that is about shape, and that's dictated by efficiency.

 

The RELATIVE ANGLE OF ATTACK is about how severe any given wing shape is applied in creating the lift in a given situation.

 

====

 

Take the same wing shape and get greater lift by passing more air over it OR by magnifying the differential with a different angle of attack.

 

Wing shape is optimized for a given relative air speed and power setting. Raise the power and relative angle of attack and the plane achieves the same lift with slower airspeed because of the increased drag.

[motoguy128]

...but, doesn't flight (inverted or not) depend upon having lower air pressure above the wing than below regardless how that's achieved, i.e. wing design or angle of attack?

 

Yes, it does require a differential air pressure, which requires a differential in distance. But...

 

How the WING itself achieves that is about shape, and that's dictated by efficiency.

 

The RELATIVE ANGLE OF ATTACK is about how severe any given wing shape is applied in creating the lift in a given situation.

 

====

 

Take the same wing shape and get greater lift by passing more air over it OR by magnifying the differential with a different angle of attack.

 

Wing shape is optimized for a given relative air speed and power setting. Raise the power and relative angle of attack and the plane achieves the same lift with slower airspeed because of the increased drag.

 

What I find interesting is "relative air speed". So at very high altitudes, most comercial planes, which are only designed for subsonic flight, are at the edge of where slowing down will stall the wing, but increasing speed will cause the plane to go supersonic. The airframe and I thin in particular turbofan engines are NOT designed for supersonic operation. I think going supersonic would stall the engine... and i think it would cause the control surfaces to become inopperable. Is that correct?

 

I beleive that was an issue with the Air France flight that crashed a few months ago in the Pacific. It's beleive the air speed indicators became inoperable due ot ice, and the plane likely stalled or went supersonic nad control of the plane was lost, or it suffered damage and rapidly lost cabin pressure. It appears that it didn't break apart in flight. Unfortunately the black boxes weren't recovered, so we may never know the exact events.

[Joe Frickin' Friday]

What I find interesting is "relative air speed". So at very high altitudes, most comercial planes, which are only designed for subsonic flight, are at the edge of where slowing down will stall the wing, but increasing speed will cause the plane to go supersonic. The airframe and I thin in particular turbofan engines are NOT designed for supersonic operation. I think going supersonic would stall the engine... and i think it would cause the control surfaces to become inopperable. Is that correct?

 

I beleive that was an issue with the Air France flight that crashed a few months ago in the Pacific. It's beleive the air speed indicators became inoperable due ot ice, and the plane likely stalled or went supersonic nad control of the plane was lost, or it suffered damage and rapidly lost cabin pressure. It appears that it didn't break apart in flight. Unfortunately the black boxes weren't recovered, so we may never know the exact events.

 

This was interesting:

 

http://www.timesonline.co.uk/tol/news/world/us_and_americas/article6446268.ece

 

[Mister Tee]

...the exception being a Lynx, as in the Red Bull aerobatic helicopter, which is capable of inverted flight. I'm pretty sure that's the only real helicopter that can do it though.

 

The other issue with inverted flight is wing dihedral, which adds to stability in level flight. You will find most aerobatic airplanes also have no dihedral, in addition to a symmetrical airfoil. I have about 40 hours of stick time in an Extra 300L, which as a symmetrical airfoil wing that has a zero angle of attack in reference to the airframe.

 

Flying it in straight and level flight is a little different than in a normal non-aerobatic aircraft. You can't fly it hands off and maintain level flight, and the nose attitude of the plane in level flight is higher than in a normal plane. But handles almost exactly the same way upside down as it does right side up.

[smiller]

...the exception being a Lynx, as in the Red Bull aerobatic helicopter, which is capable of inverted flight.

Capable of a loop, but not true inverted flight. I'm not sure the latter is aerodynamically possible in a (real) helicopter, or at least not in any practical sense.

[der Wanderer]

Yep the coffin corner. If flying high enough, there might only be 50 knots or less between the stall speed (due to air too thin at altitude) and the critical Mach speed (technically the corner is when the two speeds are equal and flight is no longer possible). Not a good place to be if you don't have reliable air speed indication.

[der Wanderer]

As for flying inverted, the wings are typically the least of the issues. Most planes are just not designed for it from a fluids and engine aspect and the last thing I'd want is to have an engine cut off on me while inverted...

That said I assume you are aware of the 707 inverted flight video, over Lake Washington, probably in the late 50s? If not, it's on YouTube and pretty cool...

[motoguy128]

Yep the coffin corner. If flying high enough, there might only be 50 knots or less between the stall speed (due to air too thin at altitude) and the critical Mach speed (technically the corner is when the two speeds are equal and flight is no longer possible). Not a good place to be if you don't have reliable air speed indication.

 

I remember a really old F-18 flight simulator I had on my PC, and as you approached 60,000ft, it struggled to maintain altitude at full throttle... meaning it likely needed more power to push it past Mach 1 to get enough lift. IT was a neat simulator. you could loa up various weapons lods and fly different mission including using a Nuke to take out a hydroelectric plant. You also had a FLIR pod for aiming the weapons. I think that was in 1994... not long after the Gulf War. I thnk I still have the game...I wonder if it will paly on XP??? I do remember that landing on a carrier was a B****. I don't think I was sucessful more than a couple times. I'd try to fly the ball, but still ended up stalling half the time or landing short. It was really hard if you took damage from AAA and had a couple major systems malfunctioning.

[bayoubengal]

Enough with all the scientific explanations. It is pure majic.

 

Now go ride, or fly...

[Ken H.]

Shouldn't you be riding?

 

He's got a point, especially before winter sets in!

 

Think come January you & Donna need to come visit us in Texas!

Holed up in the hotel for the night on our way back to Edmonton from the UN. (Taking the long way!)

 

Was one of those things I was thinking about as we were droning along on the slab...