how do air planes fly upside down and not mess up the oil flow?

[cryptokid]

if u take a 4 stroke and turn it the wrong way oil engulfs the pistons.
i could see ways of keeping contant oil flow to the engine by specialy mounting the pickup tube, but i do not see how one keeps oil off the pistons.

this would be espically a concern in a ultra light which it is popular to use a subaru or vw car engine.

so how do u do it?

 

[Ed]

An airplane set up for inverted flight will have what's known as dry sump. The engine doesn't store any oil, the Oil is contained in a separate tank and is pumped through and back out of the engine without any accumulating in the crankcase.
Lot's of other things have to be done also for sustained inverted flight.

 

[Bror Jace]

"Lot's of other things have to be done also for sustained inverted flight."

Yes, like fuel injection. If you know a lot about the Battle of Britain in WWII, you will find that the German ME-109 had an advantage over the British Spitfire and Hurricane as they could push the stick forward and go into a dive (pulling negative Gs) while the British plane had to bank and roll over often losing the German plane it was pursuing.

Anyway, you can find out more about dry sumps if you look at "real" purpose-built race cars like those in F1, CART or IRL (Indy).

--- Bror Jace

 

[MolaKule]

You could also sump from the heads if you have a gravity valve that forces the oil pump to suck oil from the heads when inverted. The valve covers are modified and linear pick-up tubes are placed in there for sumping.

We do this all the time with Buick V6's in the local homebuilt/kit flying club. We also use only Redline for these engines, since we need good AW additives.

 

[Steve S]

Very carefully!!!! Really aircraft are to me amazing. I have been in fleet type mechanic work,now called technician to you young people . I have spent 21 years working at a forklift dealership ,o.k. money but more fun than any vacation I have ever been on . With rental accounts at San Francisco International Airport I was around lots aircraft . After a while the A.P mechanics would show me all sorts of stuff about aircraft and the best part would be to sit in the cocpits of the 747's and I would pretend I was flying it.They are big jets.

 

[Bror Jace]

Steve S, that sounds like fun. I'm a long ways from retiring but I have my (part-time?) retirement job all picked out: grounds keeping at our County airport. Mostly mowing grass, weed whacking, painting the buildings, repairing cracks in the sidewalks, taxiways, runways, etc ...

Of course, I'll maintain all the equipment …

… and I’ll get to be around aviation the entire time.

'Kule, I take it you folks use the Buick V6s (turbo?) because of the power-to-weight ratio. Hmmm ... knowing only some about the application (sustained RPMs) I'd probably opt for a Mazda rotary engine ... but what do I know?

I have this prejudice against pushrod motors ... just like I do against McPherson struts on cars. I know they can get the job done but I just think we need to move beyond them already, especially for high/sustained RPM operation.

Anyway, how would the crankcase in that valve-cover-becomes-sump application be vented? I’d guess all dry sump systems are vented at the filler cap or some other type of vent on the main oil holding tank … but that’s just a guess.

Is there some type of vent somewhere on the motor itself that would work without covering the motor and engine compartment with goo?

--- Bror Jace

 

[Cujet]

I operate 2 Extra 300L stunt planes. They are fully aerobatic and can fly inverted for quite some time, about 15 minutes if power is managed well (this is due to the size of the aerobatic fuel tank).

That said, the engine is not dry sump. It is an aerobatic version of the Lycoming 540. AEIO540 if memory serves me correctly. The 14 quarts of oil do splash around internally while flying inverted or on it's side. Loss of oil pressure is prevented by the addition of aerobatic oil pickups inside the engine. They work very well, as no loss of oil pressure is noticed in normal aerobatic flying.

Chris

 

[Jay]

quote:

---

Originally posted by Bror Jace:
'Kule, I take it you folks use the Buick V6s (turbo?) because of the power-to-weight ratio. Hmmm ... knowing only some about the application (sustained RPMs) I'd probably opt for a Mazda rotary engine ... but what do I know?

I have this prejudice against pushrod motors ...

---

The Buick V6 is an attractive engine for experimental aircraft mainly because it packs a lot of cubic inches in a very compact area. The pushrod design is a big advantage here because OHC engines are more bulky. Aviation engines are very low rpm engines. The Mazda Wankel is attractive for the same reason but the power pulses are harder to tame--torsional vibration problems are more of an issue, and the Wankel needs a big muffler so some of the size advantage is lost. A piston engine will deliver better economy than the Wankel for the same amount of power, so the weight advantage is compromised also.

 

[MolaKule]

Bror,

In our case (the wet sump), the actual engine is mounted inverted for the nomal "pilot-up" position. A tbi is ususally installed for fuel supply. The valve covers are solid aluminum billets with special Neoprene gaskets torqued like crazy with eight 5/16" bolts for each valvecover/sump. Sump tubes or pipes run inside the covers about an inch above the special valve covers with standoffs/holders. Oil drain passageways are enlarged. Gravity valves control sumping for normal and inverted flight.

Gravity venting valves do the venting for normal and inverted flight in the case of the wet-sump configurations.

Other guys use the dry sump configuration with a higher volume oil pump and venting is part of the reserve tank.

 

[Cujet]

As an aside, auto engines in aircraft very often seem to lack performance. What is calculated to be 160HP on a car engine seems to act like less on an aircraft. There is a good reason for this. The packaging, cooling, intake and exhaust, and RPM is often limited to a reasonable number to assure life. This generally limits HP to realistic numbers. Also, HP to weight is often far worse than typical aircraft engines, as is engine life. There are a few good auto engine conversions, for instance Orenda built a V8 turbo with up to 600HP. It took them millions of dollars to get the engine to live. The first engines they built lasted 5 minutes. Not good in an aircraft!

Chris

 

[cryptokid]

i fail to see how a dry sump would help keep oil from being thrown around everywhere when your upside down.

all a dry sump is is the oil is stored in a tank externally. this wouldnt stop oil from sloshing the pistons and such in inverted flight. to do that would require some sort of complex baffling system to be installed around the pistons and crank.

the extra 300 guy makes alot of sence by saying multipule areobatic pickups are installed.

molakule also makes sence with his v6 valve cover/oil pan modifications.

but how does a dry sump do this? i cannot nderstand that. i have worked on dry sumps before, from porsche 911 to harley's and i just cant see how a dry sump would keep oil off the pistons.

 

[Cujet]

If you think about the EA300L, the aircraft is capable of flying on it's side. It is a horizontally opposed wet sump engine, so all of the oil is actually on top of those 3 pistons on the down side. There is nothing to keep the oil from going there.

It does not seem to matter, the engine runs just fine in any attitude.

Chris

 

[tom slick]

one thing that has not been mentioned is that radial engines have cyls that operate upside down no matter what attitude they are operating. the engines just have really good oil scavenge systems.

 

[Propflux01]

Another thing to consider is the pistons are going up and down faster than the time alloted for oil to accumulate, Hence the 'splash lubrication' mentioned earlier. Flexible pick-ups with weight on the ends always point down no matter the attitude of the aircraft. This scavenges the rest of the oil that does accumulate. As for the radials, piston speed dictates the amount of oil that falls on them also. they don't use oil ( normally) in flight, but start up a DC-3 and watch it smoke for the first few seconds from all the oil that accumulated on the lower cylinders when the engine was shut-down and oil accumulation overcame piston speed allowing what little oil left in the engine to slide to the lower cylinders..

 

[Jimbo]

Big radials use plenty of oil in flight. The old Connies had a 40 gallon tank for each Wright 3350 and a reserve tank so that the flight engineer could pump extra oil to the engine that ran out during a long flight, such as New York to Paris.

 

[Robert R. Wilson]

Check valves in the crankcase breather, fuel lines and the oil in a flat engine just changes sumps again with check valves.