I always thought the bf109 could fly inverted?

considering that it is fuel injected I always assumed the 109 could fly inverted no problems ? I recall the spitfire had problems because it was not fuel injected.

I did some testing and got some strange results

Aircraft are usually only equipped with limited fuel feeder tanks, for inverted flight.
Early Spitfires couldn’t even do negative G even briefly, because of the float type carburettor being flooded.

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There’s the fuel problem but there’s also the oil problem. If you fly inverted for too long, usually the oil pressure will drop dramatically as the oil pump is no longer able to pump oil from the reservoir into the circle. Bad things will ensue shortly afterwards, but I’m not sure if Il-2 simulates this.

If you think about it, there really is no reason to fly inverted for prolonged times, safe for aerobatics. The measures to enable it on the other hand are rather complex.


One of the more innovative solutions for the the negative g carb float issue on spitfires and hurricanes.


So if you stayed inverted it would blow the engine?

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Whatever the failure mode is for the particular engine if you starve it of oil. Most likely piston seizure.

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I always heard about this problem, never read about the solution, thanks
I know it happened in steep dives right?

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As far as I’m aware it was any amount of neg g. All dives had to include a half roll or starvation would occur as soon as the float bowls emptied. Later marks had pumper carbs which solved the issues entirely

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Mostly seize, oil is a lubricant but primarily a coolant in engines. Remove both of these features and you get a really hot, really dry area where metal is contacting other bits of metal at high speed. Eventually a cylinder will expand enough to seize itself up against the cylinder walls.

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Probably…but even if it doesn’t, landing that way can be problematic…just say’n. :scream:

In the Robin I used to fly (R2160), there was a placard in the cockpit that stated inverted flight was limited to 20 seconds, and this was an oil consideration. When I flew inverted it would be less than 10 seconds due to the engine starting to carry on due to it having an updraft carby, never did want to push my luck.

I did some hours (very little) in a Mudry CAP10 which had fuel injection and a pressurised oil system. You could fly inverted for a bit…always a really weird feeling to have all your body weight on the two shoulder straps, really hoping the bolts holding the straps didn’t go anywhere.

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How long have you had a pilots license? that’s a big accomplishment!
In australia it cost close to 30k for a private pilots license now!

Yeah! I never got used to that. Did try some inverted flight in the Grob 115 at flightschool. The sensation of hanging up-side-down wore off quickly. The blood pressure in the head. The shoulder straps. The feet falling off the pedals. It was just uncomfortable.
Oh! And all the things falling «up» in the cockpit! :upside_down_face:
And pushing it beyond -1G just hurt!


Negative g does not agree with me. We have a healthy respect for each other now. I have to take control fairly often to settle myself lol

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Hey cool - that’s the plane I’ll be doing my PPL with! Well, mainly 2120…but the club has a couple of 2160s too. Did you like flying it?

It was a delight to fly. Very responsive, the fuel tank is behind the seats, not in the wings so there is no “sluggishness/sloshiness” when manoeuvring. The rudder is huge (relatively) which gave lots on control authority in the vertical axis.

It TAS’d at 120knots, which is impressive for that size aircraft and that size engine with fixed pitch prop.


Nice. I hadn’t made the connection between responsiveness and the fuel tank placement but that makes perfect sense.

There are lots of different inverted systems. For fuel, my Pitts has a 2 gallon header tank between my legs under the main tank. It is probably good for ten minues although I don’t believe I have flown continuously inverted for more than two. Other airplanes just use a flop-tube in the main tank—not as elegant IMO.

For oil, I have a Christen Inverted Oil system. Its pretty simple. There is a 3-way valve that uses a steel bearing to direct oil to/from the bottom of the crankcase, the top of the crancase or out the breather. There is also an Oil Separator in the system (sometimes called a “slobber pot” due to the foamy nature of oil mixed with crancase gases). I am lucky in that I get zero loss of oil pressure when switching G. The only drawback to this system is that in 0g and knife-edge, I loose a lot of oil (true of all Christen systems) out the breather. I typically loose 1/2 a quart after 20 minutes of hard acro. We half jokingly consider this an oil change after 10 hours.

Shoulder straps should NEVER bother you in aerobatic flight. Shoulder straps are to keep the pilot’s face off the panel in a crash, in flight, they must be loose or you will quickly damage your back.

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I tried securing the lap belt as hard as I could, but i ended up hanging by the shoulders (and lap), anyway.

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Speaking of flying inverted.

Craig Hosking’s Pitts S-2 “Double Take”


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