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  #11  
Old 07-23-2022, 08:20 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
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RVSM runs from 29K-49K', not 18K. And yes, RVSM aircraft do have critical areas around static ports.
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  #12  
Old 07-24-2022, 06:53 AM
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gmcjetpilot gmcjetpilot is offline
 
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s
Quote:
Originally Posted by Majorpayne317641 View Post
I did not go into a full spin. The ball was dead center each time including when my instructor tried.

Sorry the second comment is not correct for fighter jets...
OK. Cool (no pun intended) and surprising it makes that much difference. In general if you are totally coordinated at stall the break should be more or less without massive drop off, unless the plane is out of rig. Not saying your plane is out of rig, but apparently your cowl flap produces yaw? Yet your ball is center? Also re reading your OP you are 50 degree nose up? Really read the Standards for Commercial Pilot. You should not need to be at that pitch. Start at a slow speed and raise nose slowly for a bleed off of 2 kts a second. If you yank it vertically you are doing an aerobatic maneuver not a power on stall. RV's do have lots of power and low stall, and at full power may not stall at all. You have to cheat it into a stall.

If you pitch real slow it will stall at a much lower pitch attitude than 50 degrees, way lower. It may not stall at all!!! CFI's who only have only flown in lower performance planes like Piper Arrow and never flown an RV-8 don't understand the RV's characteristics. It does not make them bad a CFI, but what works in a Piper Arrow is not going to work in a RV-8. A high powered RV doing a power on stall from cruise is going to result in excessive pitch up, unless your rate of pitch change is real real slow. Even then it may not stall but just mush (sink). You have to initate stall recovery when you have zero ROC. If you pitch up too fast you are doing a "wing over" or humpty bump. This is why there is the tendency to hurry this maneuver and pitch up fast to WING OVER land to force a stall that is not coming, because an RV takes too long to slow down and the maneuver will take way too long. That is why you start at slow speed, pitch up quickly at first so speed does not build. Then pitch more slowly at a rate of 1 to 3 kts a seconds. The key is start the power on stall maneuver at slow flight speed and don't let it accelerate when you add full power, This way the "stall" will not take too long. Pitch control is important. Learn what your pitch attitude is when it starts to mush or stall power (at min pitch), but 50 degrees is way too much IMHO. You can finesse this maneuver but ham handedness will result is weird and less than pretty maneuver. That finesse is what COMMERICAL rating is to teach, precise pitch, bank and yaw control though out the total flight envelope. The reason RV's do not stall easily is the airfoil NACA 23013.5, high power weight ratio, effective controls, so the power on stall is power on sink. You have to just break the "stall" when your ROC goes below ZERO. It still may not have "stalled" but going to excess PITCH to get a real stall break (that may not come), is really just low airspeed sink or an impromptu aerobatic maneuver. I don't understand why your plane does the right roll/yaw with cowl flap down and not up up. However your 50 degree pitch seems excessive and your cowl down issue may go away if you follow some of my suggestions. Just my opinion.

I don't know if Van's Aircraft will care, but if you get a chance you should reach out to them, one of the managers, not whomever answers the customer service number. I find over decades Van's can be a little dismissive of criticism or suggestions.

It would be goodness and interesting to repeat this experiment (one of the pillars of science, repeatable experiments) with another RV-8 with same cowl flap. I have very few RV-8 hours, but over 1000 hrs in the RV-4. Two people made the RV-4 a very different plane. Solo I was near forward CG limit. Two people could push it to aft limit. My girlfriend is tiny so we could fly two up and bags, although some baggage was in cockpit for long x-country camping trip. RV-8 is similar but better with the fwd baggage area. If I were doing maneuvers or aerobatics two up I would put ballast in Fwd baggage to drive the CG Fwd. This typically improves yaw stability and spin recovery.

Does it do this solo? Has any one spun the RV-8 with aft most CG and determined spin recovery response?

Quote:
Originally Posted by Walt View Post
RVSM runs from 29K-49K', not 18K. And yes, RVSM aircraft do have critical areas around static ports.
Who said RVSM starts at 18,000 feet RVSM. Anyway my RV goes up to FL410, at Mach 0.82. Oh wrong plane. ha ha. Thanks for the correction. The point was in response to surface finish on the spinner being a factor. My opinion is it will have nil effect, as the prop beating the air to death has the biggest effect on aircraft aerodynamics and control (P-factor, Torque, Slip Stream Spiral and Gyroscopic Precession) or LEFT TURNING tendencies. The fact he is rolling/yawing right and he thinks it is the cowl flap, not sure. I think is in my bold dissertation above.
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Last edited by gmcjetpilot : 07-24-2022 at 08:24 AM.
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  #13  
Old 07-24-2022, 07:25 AM
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gmcjetpilot gmcjetpilot is offline
 
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Originally Posted by smt6 View Post
Oh really Mr. Jet Pilot? Do educate us.
I get $145 an hour to teach. I am trying to be funny.
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Last edited by gmcjetpilot : 07-24-2022 at 07:32 AM.
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  #14  
Old 07-25-2022, 04:01 AM
Majorpayne317641 Majorpayne317641 is offline
 
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You are right that an RV8 power on stall is hard to do. Easing into the power on stall is what I would do each time. Max power and slowing pulling nose high, it takes almost 50 degrees to get the plane to start to slow to a stall speed. The instructor I have built and flies his own RV8. He has a few hours in those aircraft. He also said you need to cheat a little to do a power on stall or any other maneuver for the commercial as this airplane is over powered to do them according to the ACS. For example the lazy 8s, he demo'd a lazy 8 as it was done in a t37, vastly more aggressive than what the FAA wants, but the rv8 handled it so well that it actually was easier to do. Either way, whatever is going on would require testing, with strings, tape and go pros. I don't have the time to flush it out other than to be aware of it. The plane is not mis rigged, it is straight and it flies straight. All the suggestions you have make sense and was exactly what my instructor already brought up. I just didn't want to bore everyone with those details.
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  #15  
Old 07-31-2022, 08:21 AM
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cfiidon cfiidon is offline
 
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Location: Goodyear, AZ
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Default Could not duplicate

I have two cowl flaps on my -8, on the bottom, either side of the 4 pipe exhaust.

I tried to duplicate this yesterday beginning from about 75kts, pitch up, smoothly applying full power, wings level, straight ahead departure stall.

The first two times I had a boot full of right rudder to keep the ball centered, perhaps even maxed (felt like it anyway). I had a normal straight ahead stall break around 50kts IAS. I recovered immediately.

The third time I had significant right rudder but probably not ball centered. At the stall break around 48 kts IAS the right wing dropped but not much at all. Again... immediate recovery.

I suppose there are many differences that might affect this (nose gear, louvers, scoop, etc.)

Nonetheless it was a fun exercise.
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