Hammerhead oil loss

Diana

Diana

Final Approach
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Diana
Tom captured the oil spray from one of my hammerheads today on video. He told me that he has seen it from the ground before, but I couldn't imagine that it would be that visible from that far away (3000' AGL). Here's a short clip of it. You can see the spray coming out as a mist as the tail swings around on the top of the pivot (about 12 seconds into the video). This wasn't the best hammer of the day, but it was the most interesting.
 

Attachments

  • Hammerhead oil loss.wmv
    3.2 MB · Views: 154
Diana-

Interesting, that's quite a cloud, I suspect the engine was briefly running rich as you went over the top and what we see is actually coming from the exhaust rather than the breather.

Tom-
 
Skyport said:
Diana-

Interesting, that's quite a cloud, I suspect the engine was briefly running rich as you went over the top and what we see is actually coming from the exhaust rather than the breather.

Tom-
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Looks like oil to me. IMO, that grey color is the clue. A rich mixture would produce carbon which is a lot darker.

Dianna I assume you still don't have an inverted oil setup and without that oil loss is likely. Even with a good system like Christen, you will lose some doing acro, but at least you'd have oil pressure most of the time.
 
D - shouldnt the plane be a mess if its oil?
How much oil is it using?
 
Skyport said:
Diana-

Interesting, that's quite a cloud, I suspect the engine was briefly running rich as you went over the top and what we see is actually coming from the exhaust rather than the breather.

Tom-
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Tom, I would actually feel better if it wasn't oil. Never even thought of it being anything else. It was more visible than usual because of the angle of the sun behind me. My husband has seen it from the ground a few times in the past when the sun hits it just right. Actually, this was my third hammerhead right before landing and I don't usually go straight vertical anymore (I normally keep it slightly positive) because of concerns about oil draining to the bottom (back) of the engine case when going vertical or beyond to slightly negative. I could hear a pop as I throttled back on the way down...I think you can hear it in the video, too. I try to throttle back gently, so I don't know why it popped this time.
 
Ken Ibold said:
Was it in fact oil? What was the oil level before and after the flight?
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I just ran out and checked. I used about 1/3 of a quart of oil on that flight that lasted 0.6 hours with 2 spins, 2 rolls, 3 loops, 3 hammers, and low and slow lake patrol.
 
lancefisher said:
Dianna I assume you still don't have an inverted oil setup and without that oil loss is likely. Even with a good system like Christen, you will lose some doing acro, but at least you'd have oil pressure most of the time.
Click to expand...
Yeah, we decided not to change the setup. But, we are going to have an extended breather tube (with a whistle hole) installed when it's down for the recover.
 
Let'sgoflying! said:
D - shouldnt the plane be a mess if its oil?
Click to expand...
Yep, it was this time. Looks like I'll be washing oil off today. I hadn't been getting much oil on the airplane lately since I've usually been keeping it slightly positive with the hammerheads.

I've been taught to put in full throttle as soon as I get vertical. Don't know how much of an effect that has on running rich or oil loss.

Btw, here is the best hammer of the three, even though I was slightly positive. I'm open to suggestions as to how to make them better. At least I don't fall out of them anymore or try to pivot 4 seconds too soon. That string has helped a lot. :)
 

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  • Best hammer April 17.wmv
    4 MB · Views: 70
Diana-

I have always used full throttle in a Hammerhead, the throttle position wouldn't be the cause but the fact that you have a float carburator, which relies on gravity for proper function, as you go negative the float will rise and cut of fuel then when positive G's return the fuel comes rushing back in. And the location of the cloud seems consistant with the return of positive G's.

The color is really insignificant in this case because even a very rich mixture will look grey, or white, when disbursed in a cloud of this size. The size of the cloud, and the relatively small amount of oil lost, are good indications this is mixture related. Unless smoked, as in injected into the hot exhaust it would require a very significant amount of oil to create such an obvious cloud of oil, remember that breather oil is misted NOT smoked.

In addition to mixture there is a slight possibility that some of the oil sloshing around the crankcase got into the cylinder, possibly thru the rings at the bottom of piston travel, and got smoked. I have seen occasional puffs of oil smoke in Stearmans from manuvering and must assume it occurs in other aircraft with the exhaust out of view.

Tom-
 
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Skyport said:
I have always used full throttle in a Hammerhead, the throttle position wouldn't be the cause but the fact that you have a float carburetor, which relies on gravity for proper function, as you go negative the float will rise and cut of fuel then when positive G's return the fuel comes rushing back in. And the location of the cloud seems consistent with the return of positive G's.

The color is really insignificant in this case because even a very rich mixture will look grey, or white, when disbursed in a cloud of this size. The size of the cloud, and the relatively small amount of oil lost, are good indications this is mixture related. Unless smoked, as in injected into the hot exhaust it would require a very significant amount of oil to create such an obvious cloud of oil, remember that breather oil is misted NOT smoked.
Click to expand...
Thanks for the explanation Tom...that makes sense the way you explained it. I hope it doesn't have any long-lasting impact on the engine.
 
Skyport said:
Diana-

I have always used full throttle in a Hammerhead, the throttle position wouldn't be the cause but the fact that you have a float carburator, which relies on gravity for proper function, as you go negative the float will rise and cut of fuel then when positive G's return the fuel comes rushing back in. And the location of the cloud seems consistant with the return of positive G's.

The color is really insignificant in this case because even a very rich mixture will look grey, or white, when disbursed in a cloud of this size. The size of the cloud, and the relatively small amount of oil lost, are good indications this is mixture related. Unless smoked, as in injected into the hot exhaust it would require a very significant amount of oil to create such an obvious cloud of oil, remember that breather oil is misted NOT smoked.

In addition to mixture there is a slight possibility that some of the oil sloshing around the crankcase got into the cylinder, possibly thru the rings at the bottom of piston travel, and got smoked. I have seen occasional puffs of oil smoke in Stearmans from manuvering and must assume it occurs in other aircraft with the exhaust out of view.

Tom-
Click to expand...
Are there carbs that prevent this or does one just use fuel injection?
 
Diana-

Nothing to be seriously concerned about, as we have discussed before it is always good to be gentle with the throttle, avoid rapid full ON/OFF power changes as much as possible, BUT always keep in mind that safety is more important and aerobatics will at times require rapid power changes.

Tom-
 
HPNFlyGirl said:
Did you loose oil pressure during that?
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Brook, I don't know for sure. I'm so busy looking out at the outside visual references from the different phases of the maneuver that I don't look inside after the dive and the 4 G pull. The oil pressure is OK when I come out of it.
 
Scott-

The pressure carb will function in negative G's, while inverted, as will fuel injection. Pressure carbs were used extensively on large radials, fuel injection was rare on radials, many of the larger horizontally opposed engines, in the 50's-early 70's, used pressure carbs also but they are rare today. I have a friend who has one on a Ranger powered Great Lakes he performs in because Rangers were never injected.

Tom-
 
smigaldi said:
Are there carbs that prevent this or does one just use fuel injection?
Click to expand...

A pressure carb wouldn't be affected very much by negative G (assuming you had a header tank with flop tube) but that's essentially the same thing as throttle body injection.
 
Skyport said:
Scott-

The pressure carb will function in negative G's, while inverted, as will fuel injection. Pressure carbs were used extensively on large radials, fuel injection was rare on radials, many of the larger horizontally opposed engines, in the 50's-early 70's, used pressure carbs also but they are rare today. I have a friend who has one on a Ranger powered Great Lakes he performs in because Rangers were never injected.

Tom-
Click to expand...

I had never heard of those. I'll have to do a little research and learn about them Thanks!
 
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