roadrunner20

roadrunner20

Well Known Member
Other than inverted flight, is there any basic aerobatic manuevers I should restrict without flop tubes?

I'm about to take my first aerobatic training session.
Up to now, I've been honing my skills on steep turns, wing overs & chandelles.

As others, to begin, I'm looking at spins, aileron rolls, loops & barrel rolls.
 
Good to hear that you're getting training. A smart move.

None of the items you list are a problem without inverted systems. You'll know you have it licked when you can do Cuban 8's and maintain alignment along a road or other feature on the ground. Those are fun. As is the first time you get a loop "right" and hit your wake vortex as you complete the loop.
 
If you are hanging in the straps you are doing something wrong. If you finish with zero or less than zero G on your G meter you are doing something wrong.

You need to keep some +G; light in the seat, less than one is ok but don't go zero or neg.
 
Kyle Boatright said:
Good to hear that you're getting training. A smart move.

None of the items you list are a problem without inverted systems. You'll know you have it licked when you can do Cuban 8's and maintain alignment along a road or other feature on the ground. Those are fun. As is the first time you get a loop "right" and hit your wake vortex as you complete the loop.
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Dont you go a bit negative with a Cuban 8 on the down side of the loop? I was taught to hold the inverted line for a bit before rolling over. Probably not a problem without inverted system due to the short time you are there but if you dont have inverted oil or some kind of oil return your going to get a belly full of oil I would think.
 
JonJay said:
Dont you go a bit negative with a Cuban 8 on the down side of the loop? I was taught to hold the inverted line for a bit before rolling over. Probably not a problem without inverted system due to the short time you are there but if you dont have inverted oil or some kind of oil return your going to get a belly full of oil I would think.
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To complete a Cuban to competition standards, yes, you'd go slightly negative on the 45 downline. But we're talking recreational acro here, so you'd probably roll slightly ahead of the 45 downline and not actually draw an inverted line. Everything remains positive. Watch the Aeroshell Team. What they do is comparable to the type of (positive) maneuvering RVs are good at.

To the original question, you'll know pretty fast what you'll want to avoid w/o inverted systems. Some people don't mind engine sagging or a little oil thrown out. Fuel starvation for a moment never hurt anything. I would worry more about oil pressure drop. A properly done hammerhead, though not inverted, but zero G, will cause your oil pressure to drop to nothing for a bit even though the engine never misses a beat. I quit doing those pretty fast. RVs roll fast enough that you can do a respectable slow roll with just a momentary engine sag through inverted. Can't think of any other basic maneuver to restrict. Most can be cheated and kept positive.
 
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I don't have flop tubes or any inverted systems -- just regular fixed pickup tubes.

In my airplane I have done the following maneuvers:

Lazy 8s, Cuban 8s, Immelmans, Rolls, Loops, Hammerheads and really crappy vertical rolls. Obviously I would never win an IAC competition or anything, but I always am able to keep a little positive G on the plane. I've never even seen the oil pressure drop and never gotten an oil pressure alarm. So far I've had no regrets not putting in inverted systems.
 
We have no flop tubes, an IO-360 engine, non-aerobatic prop.

Without any inverted oil system, it did dump a fair amount on the belly / out of the breather with negative / zero 'g' (slow rolls, Cuban / Horiz 8 with inverted "check", stall turns).

We have now added half a Raven system - the 4" breather tank and sump return but without the inverted oil pickup etc. Now seem (early days) to be able to do all the above with very little oil loss. A "long" slow roll sees Oil Pressure fall off and Prop start to increase in RPM... but that's as much / more than enough negative 'g' as we want. Fuel system has never caused any problems...

HTH
Andy & Ellie Hill
RV-8 G-HILZ
 
Inverted oil

Anyone know how much an inverted oil system weighs ?

Also, what would be a recommended system for a -8 ?

Thanks

Steve
 
If you don't have a metal prop, and you get any negative at all, the prop may stop - especially at low speed as in a hammerhead. No big deal, the engine should start up with a twist of the key.

As others have said, if you keep the maneuvers to recreational style, you can do lots without a full inverted system.

Full inverted for me when the time comes :D
 
Andy Hill said:
We have no flop tubes, an IO-360 engine, non-aerobatic prop.

Without any inverted oil system, it did dump a fair amount on the belly / out of the breather with negative / zero 'g' (slow rolls, Cuban / Horiz 8 with inverted "check", stall turns).

We have now added half a Raven system - the 4" breather tank and sump return but without the inverted oil pickup etc. Now seem (early days) to be able to do all the above with very little oil loss. A "long" slow roll sees Oil Pressure fall off and Prop start to increase in RPM... but that's as much / more than enough negative 'g' as we want. Fuel system has never caused any problems...

HTH
Andy & Ellie Hill
RV-8 G-HILZ
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Each time you do that you are playing russian roulette and adding cumulative damage to the engine. Just a matter of time, perhaps when you least expect it, a rod will come busting out of the case.
 
Just to clarify the above post...

The sort of aeros we generally wish to do sees Oil P maintained at a normal level... I have once seen, as above, Oil P start to fall off, but in fact maintained above the "minimum" quoted in the Engine manual (50psi), and 2400RPM start to increase to, say 2450RPM... both of which I consider "undesirable" and shows where the limit of this setup lies...
 
The oil goes from the pickup screen to the pump (without the inverted pickup). When you unload or go neg enough for the oil to come out the breather and see a drop in pressure and the prop starts going faster the pump is sucking air. Don't kid yourself and think you are not going to hurt the engine. It takes a few moments for the restrictor (all restrictors are not the same), hose, and transducer to bleed down. Just because the indication you saw didn't go below the low limit doesn't mean that the big gulps of air going through your oil system will not do any damage. A rod busted through the case will make a big impression on you and you will stop doing that. Same problem when guys have all the inverted stuff installed and fly around gulping air at zero G. There really should be a limitation like this: No inverted system: minimum .25G; With inverted system: no steady state flight -.25 to .25G. The inverted system when installed needs the check valve ball to swap ends and the oil to be available out the breather to work.
 
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