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  #1  
Old 12-30-2017, 09:08 AM
tracy tracy is offline
 
Join Date: Dec 2012
Location: chattanooga,tn
Posts: 149
Default Acro in an 8

Got a wild hair yesterday and performed a hammerhead in my o360 8. During the rotation, I noticed smoke boiling behind/around me. After landing I realized why by the amount of oil on my belly (Case vent just above exhaust). Am I hurting the engine performing this maneuver without inverted oil?
Second, whatís the word on doing tailslides if we prevent elevator from slamming full deflection.
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  #2  
Old 12-30-2017, 11:15 AM
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Gash Gash is offline
 
Join Date: Aug 2009
Location: Goodyear, Arizona
Posts: 626
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Hi Tracy,

If done correctly, a hammerhead should not do any harm to your engine since you are not flying inverted or negative G. Also called a "stall turn" in the Queen's English, a hammerhead turn is simply an abrupt 180 change of direction using gravity and the rudder; you just happen to be flying straight up when you start the turn. None of this will harm an engine without an inverted oil system.

Some considerations are worth pointing out though. The RV-8 initiates hammerheads quite nicely around 30 knots. Don't get to zero airspeed and then kick the rudder, since you might get into a tail slide or fall-on-your back regime. Keep "some" airspeed (like 30 knots) on the airplane so that you have rudder authority. On the other hand, don't start the maneuver too fast or you'll "fly over" instead of pivoting the turn.

Another consideration is the direction of turn. Because the Lycoming engine rotates to the right (as viewed from the cockpit), the gyroscopic effect of the propeller makes it so that you'll want to do hammerheads to the left. Experiment with both directions and you'll see what I mean.

Be sure to look carefully to see if the airplane is vertical before and after the turn. Use not only rudder, but aileron and elevator to finesse this. When finished, check that the wing trailing edges are perpendicular to and on the horizon when vertical down, and that you're perfectly vertical (not slightly positive or negative pitch).

On your last question about tail slides, the answer is no. Vans RV aircraft are not designed for tail slides. Definitely not recommended.

Finally, get some good aerobatic instruction if you haven't already. This is important. It will really enhance your enjoyment of aerobatics, as well as make sure you're doing it correctly and safely.

There are quite a few aerobatic RV pilots out there. I hope you have a great time with it. I also encourage you to join IAC if you haven't already. You will meet many more RV aerobatic pilots and learn more about the "art and science" of aerobatics. It's really fun to explore the capabilities of these wonderful airplanes, and aerobatics helps you to be a more capable pilot in every flight condition.
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Last edited by Gash : 12-30-2017 at 11:20 AM.
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  #3  
Old 12-30-2017, 01:00 PM
oaklandaviator oaklandaviator is offline
 
Join Date: Dec 2014
Location: Somerville, Tn and Little Rock, Ar
Posts: 47
Default Vertical flight

While flying vertical up and not pulling or pushing, the oil can pool in the accessory case, which is where your crankcase vent is located. Positive crankcase pressure and gravity can cause quite a bit of oil to escape through the vent. I would suggest at least a half system or oil separator in the vent line to prevent the loss of oil.
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  #4  
Old 12-30-2017, 02:56 PM
skylor's Avatar
skylor skylor is offline
 
Join Date: Aug 2009
Location: Southern California
Posts: 582
Default Wild Hair Aerobatics

Quote:
Originally Posted by tracy View Post
Got a wild hair yesterday and performed a hammerhead in my o360 8. During the rotation, I noticed smoke boiling behind/around me. After landing I realized why by the amount of oil on my belly (Case vent just above exhaust). Am I hurting the engine performing this maneuver without inverted oil?
Second, what’s the word on doing tailslides if we prevent elevator from slamming full deflection.
A hammerhead is probably not a great maneuver to attempt on a "wild hair". At the very least, you need to be proficient in inverted and upright spin recoveries before attempting them. A late correction of an overshoot of the vertical line can easily result in an inverted spin since your are: 1. attempting to push the nose back to vertical with very low airspeed over the wings, and 2. Using rudder to kick the turn. These are pro-spin control inputs. Since I see that you used to own a Pitts, you probably already know all of this.

Also, are you running a fixed pitch or constant speed prop? Temporary oil starvation can cause runaway engine speed with a non-counterweighted constant speed prop.

Regarding tail slides: If you ever have a chance to look closely at something like a Sukhoi or Extra undergoing an annual inspection, you will gain some appreciation as to why RV's aren't good candidates for tail slide maneuvers. The control linkages, bell cranks, push rods, etc. are massive (especially on the Sukhoi) compared to the RV's. In addition, RV tail surface hinges are not well suited to the type of loading that reverse aerodynamic flow can impose on them.

Fly Safe,

Skylor
RV-8

Last edited by skylor : 12-30-2017 at 03:03 PM.
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  #5  
Old 12-30-2017, 03:42 PM
F1R F1R is offline
 
Join Date: Nov 2010
Location: ____
Posts: 538
Default Tame those wild hair's

I have a friend who flew air displays in a few different Pitts over several years.

About the time he was ready to move on to other life ventures , he managed (on purpose) to do an extended tail slide and allowed gravity to build excessive airspeed in reverse. Actually a lot more than he planned on. Before the nose finally did change ends the air speed was high enough it tore much of his bottom cowl and some of his exhaust & hangars off in the process. The air flow took the parts through the propeller arc. After he got it back on the ground, the pitts moved indoors for several years and he went farming full time.

What Gash said about getting some good instruction is spot on.

Edit

I see you had an S2 so you likely have lots of aerobatic time.... The RV 8 is not an unlimited machine like the Pitts. A humpty bump is about as close as you can get.

Last edited by F1R : 12-30-2017 at 10:12 PM.
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  #6  
Old 12-30-2017, 04:44 PM
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ronschreck ronschreck is offline
 
Join Date: Mar 2006
Location: Gold Hill Airpark (NC25), NC
Posts: 1,238
Default We need you!

Tracy,

Where have you been hiding? You are just 80 miles from one of the finest IAC chapters in the country. IAC Chapter 3 is in Rome, Georgia. Some of the best aerobatic pilots in the country are available to teach you everything you ever wanted to know about aerobatics. Contact Mark Fullerton (markpcc2003@yahoo.com) and tell him I sent you. They are having a fly-in meeting on January 6th.

Just to be clear, no tail slides in RV's.
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  #7  
Old 12-30-2017, 09:42 PM
spatsch spatsch is offline
 
Join Date: Nov 2014
Location: Randolph, NJ
Posts: 158
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Quote:
Originally Posted by oaklandaviator View Post
While flying vertical up and not pulling or pushing, the oil can pool in the accessory case, which is where your crankcase vent is located. Positive crankcase pressure and gravity can cause quite a bit of oil to escape through the vent. I would suggest at least a half system or oil separator in the vent line to prevent the loss of oil.
To add to this even if you had an inverted system at 0g (which you should have on a straight up or down line) the valve on the breather line will not be properly closed in either direction so some oil loss is difficult to avoid just the volume changes (substantially) with an inverted system.

As for if the engine cares. I have a fixed pitch IO360 and looked at oil pressure at various positive, neutral and negative G loads using my Dynon before I installed my 1/2 inverted system. Oil pressure stays well above Lycoming minimums for way longer then you spend on a hammerhead so I wouldnít be to worried about it. On the other hand I donít have a constant speed prop nor am I an engine expert.... .

Oliver
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  #8  
Old 12-30-2017, 10:06 PM
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DonFromTX DonFromTX is offline
 
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Location: La Feria Texas
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Wow, am I ever impressed with your resume!! But please tell me in language I can understand exactly what or how that photo of you in your RV8 translates. I just cannot figure it out!

Quote:
Originally Posted by spatsch View Post
To add to this even if you had an inverted system at 0g (which you should have on a straight up or down line) the valve on the breather line will not be properly closed in either direction so some oil loss is difficult to avoid just the volume changes (substantially) with an inverted system.

As for if the engine cares. I have a fixed pitch IO360 and looked at oil pressure at various positive, neutral and negative G loads using my Dynon before I installed my 1/2 inverted system. Oil pressure stays well above Lycoming minimums for way longer then you spend on a hammerhead so I wouldnít be to worried about it. On the other hand I donít have a constant speed prop nor am I an engine expert.... .

Oliver
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  #9  
Old 12-30-2017, 10:30 PM
spatsch spatsch is offline
 
Join Date: Nov 2014
Location: Randolph, NJ
Posts: 158
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Quote:
Originally Posted by DonFromTX View Post
Wow, am I ever impressed with your resume!! But please tell me in language I can understand exactly what or how that photo of you in your RV8 translates. I just cannot figure it out!
Thatís from my phase 1 flight testing. Simple top of a loop with a go pro from the wingtip. As you can see looking at my body I was carrying way to many positive Gís I hope I improved somewhat since ..... .

Oliver
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  #10  
Old 12-30-2017, 11:24 PM
tracy tracy is offline
 
Join Date: Dec 2012
Location: chattanooga,tn
Posts: 149
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Quote:
Originally Posted by ronschreck View Post
Tracy,

Where have you been hiding? You are just 80 miles from one of the finest IAC chapters in the country. IAC Chapter 3 is in Rome, Georgia. Some of the best aerobatic pilots in the country are available to teach you everything you ever wanted to know about aerobatics. Contact Mark Fullerton (markpcc2003@yahoo.com) and tell him I sent you. They are having a fly-in meeting on January 6th.

Just to be clear, no tail slides in RV's.

Ron, I was just down there 3 weeks ago for their flyin breakfast. Plan on returning to the next one!
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Chattanooga, Tn
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