RV-8 Static Longitudinal Stability

Disclaimer: I'm probably ten years away from flight testing anything other than my recliner, so please bear with me on this long-winded post.

In a (vain) attempt to educate myself, I've been poring over the articles on the CAFE Foundation website over the past few days -- WOW is that place an online goldmine! -- and I came across the Aircraft Performance Report for the RV-8A (PDF). Actually, I think I had read it at some point before, but today I was trying to compare numbers with some of the other popular kitplanes that had been profiled.

The thing that caught my eye in particular was the Static Longitudinal Stability graph (reproduced below), which compares stick forces at various airspeeds and CG positions.


According to the CAFE APR Intro/User's Guide (PDF):

The static longitudinal stability graph shows the character of the pitch stability as follows:

A line running 'downhill' to the right indicates positive stability, i.e., the aircraft wants to stay at trim speed and requires the conventional pull on the elevator stick to slow down or push to speed up from trim speed. A steep downhill line means the positive stability is strong and thus that aircraft would be more suitable for cross-country flying, while a gradual downhill line would indicate an aircraft more suitable for aerobatics.

A line running horizontally would indicate neutral stability, i.e., the aircraft requires zero elevator stick force to change speed -- very undesirable.

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You'll notice from the graph that in the aft-CG condition, at 140 mph IAS (purple line), the stick force curve actually reverses! I remembered reading on this forum in places that aft-CG flight testing was very important with RVs, and that the procedure should be approached with caution, and well before flying around with passengers.

Here's what C.J. Stephens, the test pilot, had to say on the subject:

Static longitudinal stability was measured by trimming to Va (140 mph indicated) and measuring stick force required to hold speeds in ten-mph increments from 70-190 mph, while maintaining altitude by adjusting power. Note that for the forward cg condition, the result was a very substantial positive force gradient as speed varies in either direction from the trim condition.

In the aft-cg test, however, a reversal of the force gradient was encountered as speed was reduced from 140 to 70 mph indicated, with the maximum force occurring at about 110 mph. It is generally desirable that some positive force gradient exists as speed deviates more and more from the trim point, and imperative that no actual force reversals occur.

I would recommend that pilots explore aft-cg stalls with some care to familiarize themselves with stick force behavior in this region. We did not conduct tests with loadings further aft, but the trend would indicate that the gradient reversal observed would become more pronounced, and stick force during stalls at the full aft limit could be near zero when trimmed for a normal approach. (Emphasis mine.)

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As you might imagine, this really caught my attention. My questions are:

(1) What "interesting" flying qualities have -8 drivers noticed while testing in this region?

(2) Did you make substantial deviations from Van's aft CG limit recommendations (29% chord/16.8" aft leading edge/86.82" aft datum) when writing your POH?

(3) If a guy was building an RV-8 and intending to fly around with two Bubbas (200+ lbs.) onboard every once and a while, what modifications (i.e., battery in back or front) might he consider?

Thanks in advance!

Stick force gradient is not the same as static longitudinal stability

This will probably start a hail storm. It is so often stated in books and flight teting, but it is not true. Static longitudinal stability is the STICK FIXED pitching moment gradient ( d_CM/d_CL). It relates changes in pitching moment to changes in angle of attack with the stick fixed at a trim condition.

To some degree, stick force gradient should correlate with static stability, but there are other important factors that affect the stick force gradient. The hinge moment characteristics of the elevator have a dominant effect - and things like the amount of aerodynamic balance of the elevator, the elevator camber, trim tab position, all affect the hinge moment, and feed through to the stick force.

But none of those factors which influence the elevator hinge moment influence the STICK FIXED stability characteristics.

The plot shown here was for a condition where the airplane was trimmed at 140 kt, and then stick force measured over a broad speed range. So there is a lot of elevator deflection at speeds other than the trim speed. The shape of the curve far away from the trimmed speed point is not very meaningful. IF the test were repeated with the airplane trimmed at 90 kt, the curve would be shaped differently.

I have not flown my -8 at aft c.g. yet, so I can not say what the stick force gradients will be. I will report as soon as I do. I am aware of a glider that has negative stick force gradients because of negative camber in the elevator and a large aerodynamic balance tab. It is unpleasant to fly, but it is not statically unstable.

By the way, an easy fix to a negative stick force gradient is to put positive camber in the elevator, or a trim tab that is bent down at the trailing edge. Note that in the plot here, if the airplane were trimmed at 90 kt, that would move the elevator trim tab down. I promise that will give a positive stick force gradient at 90 kt, if you are trimmed at 90 kt.

What is a W10?

I would be much more worried if I had a W10 - I don't know what that is, but it sure has light control forces. That may or may not indicate poor stability, as discussed above.

scsmith said:

I would be much more worried if I had a W10 - I don't know what that is, but it sure has light control forces. That may or may not indicate poor stability, as discussed above.

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I believe a W10 is a Witman Tailwind...

Karl

RV8N said:

I believe a W10 is a Witman Tailwind...

Karl

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That is correct.

I think this plot shows very well what many RV-8 pilots have experienced on their first landing with a passenger - the airplane is clearly more sensetive with a full-sized body in the back, but not surprisingly so when they are up and away at speed. Then they come in to land, and as they slow down over the fence, there is this feeling of the bottom falling out and the airplane pitching up - which is exactly what you'd expect if the stick force did what the plot shows.

I think Karl was the first one to tell me about this on my very first RV-8 flight (in the back seat of his -8). Most people end up carrying more speed down final when they have a passenger as a result - and learn to handle pitch very gingerly. An attempt at a three-point in this loading condition is a very good prescription for a HARD tail-first landing, followed by a bone-crushing main gear arrival.

That's a great plot - I've been flying the -8 for almost 1,000 hours, and this is the first time I have got a good, clear way to describe what I know intuitively is happening.

Paul

You know, Paul, when I studied that plot I thought the very same thing.

Is it just very light, or is it twichy?

Paul's and Don's comments have me wondering with some concern -- and I'm not far from being ready to go fly at aft c.g. and find out -- but:

Does the control force just get really light, or does it actually get twichy - meaning, is it actually hard to hold a constant pitch attitude, or do the forces just get really light? If I flare to 3-pt attitude and hold it there, will it not stay there?



As a follow-on to the point about stick force not necessarily correlating to static stability, consider a radio control model airplane. It can be perfectly nice and stable, but the stick force gradient is essentially zero on the control box ( unless you add some synthetically). None of this is to devalue the observation that weak stick force gradient is not as nice to fly, and negative stick force gradient is downright spookey.

scsmith said:

Paul's and Don's comments have me wondering with some concern -- and I'm not far from being ready to go fly at aft c.g. and find out -- but:

Does the control force just get really light, or does it actually get twitchy - meaning, is it actually hard to hold a constant pitch attitude, or do the forces just get really light? If I flare to 3-pt attitude and hold it there, will it not stay there?

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No, I wouldn't say it's twitchy - it just gets incredibly light - like close to zero force. If you aren't ready for it in the flair, then you'll over control, the nose goes higher than you want, and if you're close to the ground - bang!

The more I think about it, the more I think this is one strong reason more -8 pilots like to wheel land - it keeps you from getting into this hole when you have a passenger.

Paul

One more thing to keep in mind when looking at those plots from the CAFE Foundation - they didn't do a pure longitudinal stability test. They did the test in level flight, varying the power to achieve the desired speed change.

There are significant changes in stick force at a constant airspeed if you change the power. The way the CAFE Foundation did their tests makes the result = the sum of stick force changes due to speed + stick force changes due to power. It is interesting to look at, but doesn't necessarily mean anything.

The right way to do the test is to leave the power constant as you go to the off-trim condition. This implies that the altitude will change, but it avoids having the pitching moment from power changes pollute the test results.

I haven't done any testing further aft than mid CG yet. I was just staring a series of tests to walk the CG back over a number of flights when I had my big engine overspeed. Then after putting the engine back on I was back into engine break-in. I should start back at the aft CG envelope expansion this weekend, I hope.

RV-6

I have a vivid memory of the first time I flew an RV-6. It was with Mike Seager in "Old Blue." When I did the first stall I was startled enough that I mentioned it to Mike and he did a stall just to check it out.

What got my attention is that as I slowed to a stall the stick force stopped increasing at some point which was something I was not used to at all.

I was exposed to it and assured it wasn't a big issue. I'm not sure if my RV-6 does it or not. It was just different than the factory airplanes I had flown to that point.

I have found that with aft CGs the six also needs care in the landing. Just as Paul spoke about, it is easy to get into a too high nose attitude and the stick forces do get a lot lighter.

Stick Force

Ironflight said:

No, I wouldn't say it's twitchy - it just gets incredibly light - like close to zero force. If you aren't ready for it in the flair, then you'll over control, the nose goes higher than you want, and if you're close to the ground - bang!

The more I think about it, the more I think this is one strong reason more -8 pilots like to wheel land - it keeps you from getting into this hole when you have a passenger.

Paul

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I once ferried a friend to a nearby airport to pick up his Barron after some radio work. He's 5ft 20in. tall and weighs 2XX lbs. I was right at the aft CG limit.

No problem with take off and cruise but on landing, (I chose to wheel land with a little extra speed) I had to use forward force on the stick to keep from over rotating. It was not a lot, but much different from the normal back pressure on the stick on landing.

The -8 is a different animal when landing with a heavy pax in back.

mannanj said:

The -8 is a different animal when landing with a heavy pax in back.

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And hopefully folks will first experience this in the flight test phase, using well secured ballast to simulate the weight of a passenger. That way you can do several flights, moving the CG a bit further aft on each flight, rather than doing it all in one big step when you first fly with a passenger. The first aft CG test flights should be flown solo, rather than with a passenger on board.

Ballasting in Phase 1

I am getting ready to start shifting my cg aft during my phase 1 test flying and had a question about ballast and arm. My plan was to start securing sand bags to the rear seat, but I was unsure of what the actual "arm" of the rear seat would be. My thinking is that when you place a passenger in the rear seat, some of his weight is actually forward of the seat pan since his legs are going forward quite a bit. Am I over-thinking this?

scsmith said:

...if the airplane were trimmed at 90 kt, that would move the elevator trim tab down. I promise that will give a positive stick force gradient at 90 kt, if you are trimmed at 90 kt.

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Does this mean that an aft-CG 3-pointer would be easier/more controllable if you "over-trimmed" it for finals - i.e. trimmed it for a speed slower than your approach speed - meaning you'll have to fly the approach with some forward stick force.

Just thinking out loud here, would a servo tab* improve the stick-force gradient under these conditions, or perhaps just bugger up the forward-CG condition?

A

*no, I really don't want to have to build another trim tab!

Wow, this is a great discussion; thanks everyone for chiming in!

It sounds like the light stick forces with aft c.g. are a fairly common occurrence with RVs of all types, and pilots are simply making adjustments to their technique when flying with an aft c.g. The other CAFE RV performance reports seem to confirm this phenomenon as well (and RVs aren't the only planes that were displaying this).

I guess I'm still unclear about what's really going on here aerodynamically. Is the flow separating at the tail? What actually causes the lighter stick forces? (I guess maybe Steve did try to answer this question, but I'm probably too dumb to get it.)

Also, I noticed several people had comments like Larry's: "It was just different than the factory airplanes I had flown to that point."

Now I know these are "Experimental" aircraft, but if we were all real military/factory test pilots or engineers (and some of you guys are, no doubt), what would our recommendations to the designers be? Would it be, "Well let's just include a footnote in the POH about handling qualities at aft c.g.," or "Let's shorten the c.g. envelope a bit," or "Houston, we have a problem."?

Is there a danger of "deep stall" in this condition? I keep thinking of the Discovery Channel video of Mike Melvill doing the first stall series with SpaceShipOne and his "exciting" findings.

I don't mean to sound like I'm making a big deal about this, because you've all seemed to adapt well to it, and I'm not all that concerned about it myself, it's just that I hate it when I don't understand the "why" of something. Thanks again.

Even when I'm solo and full fuel, my -8 has light stick forces when I get below 80 kts. I'm usually eyes-outside when I'm in the pattern and this is my first indication that airspeed is getting too low. It's time to get the nose down or add power (or both).

IO-360 (angle valve), Hartzell C/S, rear battery

Karl

aeropunk said:

I guess I'm still unclear about what's really going on here aerodynamically. Is the flow separating at the tail? What actually causes the lighter stick forces? (I guess maybe Steve did try to answer this question, but I'm probably too dumb to get it.)

Also, I noticed several people had comments like Larry's: "It was just different than the factory airplanes I had flown to that point."

Now I know these are "Experimental" aircraft, but if we were all real military/factory test pilots or engineers (and some of you guys are, no doubt), what would our recommendations to the designers be? Would it be, "Well let's just include a footnote in the POH about handling qualities at aft c.g.," or "Let's shorten the c.g. envelope a bit," or "Houston, we have a problem."?

Is there a danger of "deep stall" in this condition? I keep thinking of the Discovery Channel video of Mike Melvill doing the first stall series with SpaceShipOne and his "exciting" findings.

I don't mean to sound like I'm making a big deal about this, because you've all seemed to adapt well to it, and I'm not all that concerned about it myself, it's just that I hate it when I don't understand the "why" of something. Thanks again.

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Brian,

Aerodynamically, there is no problem. The RV's get light in pitch when the CG is aft simply because they don't run huge tail areas, and we do fly them right up to the practical aft limit (not limited by FAR criteria).

A simplified explanation: The lighter stick forces are because there's less trim load on the horizontal tail to keep the airplane in a balanced flight condition. At forward CG, the tail must provide more down-force to balance the airplane, and that requires more elevator deflection. More deflection requires more control force from you, the pilot. Said another way, when nose heavy, the tail must work harder to maneuver the airplane in pitch, requiring more force on the stick.

As Steve pointed out, there are a number of factors related to the control surface design, the trim tab design, and the fixed surfaces themselves that contribute to stick force (or feel) characteristics. The designer can modify lots of things to change stick gradient, but IMHO the RV's are done right and I wouldn't personally advocate a change to the design to try and modify pitch feel in these airplanes.

As you've noted, we adjust our technique when we're tail heavy. Its part of the challenge of being a good sport pilot!

scsmith said:

This will probably start a hail storm. It is so often stated in books and flight teting, but it is not true. Static longitudinal stability is the STICK FIXED pitching moment gradient ( d_CM/d_CL). It relates changes in pitching moment to changes in angle of attack with the stick fixed at a trim condition.

To some degree, stick force gradient should correlate with static stability, but there are other important factors that affect the stick force gradient. The hinge moment characteristics of the elevator have a dominant effect - and things like the amount of aerodynamic balance of the elevator, the elevator camber, trim tab position, all affect the hinge moment, and feed through to the stick force.

But none of those factors which influence the elevator hinge moment influence the STICK FIXED stability characteristics.

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Yes, but you cannot measure d_CM/d_CL directly in test flight without the hand of God imparting a disturbance and having the aircraft connnected to a device to measure the moment generated. The restoring moment that is required due to a change in airspeed from trim can only be measure by the test pilot as a required change in stick position. i.e. as stated in the parlance of flight testing "Positive longitudinal static stability was "indicated by" the requirement for increasing forward stick with increasing airspeed from trim and increasing aft stick with decreasing airspeed from trim." Also note that it is stick position in the statement. Also, you can only discuss static stability of being positive, negative, or neutral based on these tests. You cannot discuss anything about the strength of static stability wihtout doing a different test. The many reasons that you cannont directly measure strength with this test are mentioned in the comment above with the additin of gearing ratios which are very important in helicopters. d_CM/d_CL is refering to both sign and strength of static staiblity. The graph can only provide insight to the sign of static stability.

scsmith said:

The plot shown here was for a condition where the airplane was trimmed at 140 kt, and then stick force measured over a broad speed range. So there is a lot of elevator deflection at speeds other than the trim speed. The shape of the curve far away from the trimmed speed point is not very meaningful. IF the test were repeated with the airplane trimmed at 90 kt, the curve would be shaped differently.

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A very important point and one that student test pilots frequently misunderstand early in our course. There are no local areas of negative static stability or reversals of slope. You can only discuss static stability about the trim point and the slope of the line between trim at 140 kt to 70 kts is still indicating positive static stability. If you are concerend by the area between 70 and 90 kts you trim at 80 and do it again. Also it is better to plot position and force on different y-axes. They may actually tell different stories.

scsmith said:

I have not flown my -8 at aft c.g. yet, so I can not say what the stick force gradients will be. I will report as soon as I do. I am aware of a glider that has negative stick force gradients because of negative camber in the elevator and a large aerodynamic balance tab. It is unpleasant to fly, but it is not statically unstable.

By the way, an easy fix to a negative stick force gradient is to put positive camber in the elevator, or a trim tab that is bent down at the trailing edge. Note that in the plot here, if the airplane were trimmed at 90 kt, that would move the elevator trim tab down. I promise that will give a positive stick force gradient at 90 kt, if you are trimmed at 90 kt.

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The reason so much is made of force gradient is that humans are biomechanically not terribly accurate at determining positon as they are force as a means of feedback. In irreversible or partially reversible systems systems, a great deal of effort is expended in generating forces that make the aircraft feel statically stable even if the stick position gradient is flat or negative. We call this "apparent static stability." We can talk about position and force cues to off tirm speed conditions and whether or not that cueing is adequate, but we still can't say how strong static stabiilty is based on the plot.

Maybe a stupid question

In the RV-8 (or 8A) the pilot is sitting pretty much over the main wing spar. The CG of the pilot in the front seat would be a little aft of the spar so the arm is very short and a change in weight in the front seat shouldn't change the aircraft's CG much. When you put someone in the back seat the CG change can be substantial.

I've often wondered if it would be better to set it up to fly solo from the rear seat for CG reasons. Then when you take a passenger in the front the change in CG would be minimal. This of course would require engineering changes I'm not going to make and mine will be like the rest; pilot/solo from the front. I've just wondered about this from time to time.

In gliders we almost always fly with passengers in the front seat and solo from the front. Piper Cubs fly pilot/solo from the rear seat probably for that reason.

tinman said:

I am getting ready to start shifting my cg aft during my phase 1 test flying and had a question about ballast and arm. My plan was to start securing sand bags to the rear seat, but I was unsure of what the actual "arm" of the rear seat would be. My thinking is that when you place a passenger in the rear seat, some of his weight is actually forward of the seat pan since his legs are going forward quite a bit. Am I over-thinking this?

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Your observation with the location of the CG of the pax is correct. I haven't measured the location of the rear seat to see how it compares to the arm that Van has used for the passenger. The only way to really sort this out, I think, would be when doing the weighing. With the aircraft leveled and on the scales, weigh it twice - once with both seats empty, and once with a typically shaped human in the rear seat. Then a bit of math can tell you were the CG of that human was. This will give you a reasonable arm to use for CG calculations with rear seat pax.

For your ballast, simply measure the location of the centre of the ballast, figure out how far aft that is from the datum, and use that as the arm in your CG calculation.

Bill Wightman said:

A simplified explanation: The lighter stick forces are because there's less trim load on the horizontal tail to keep the airplane in a balanced flight condition. At forward CG, the tail must provide more down-force to balance the airplane, and that requires more elevator deflection. More deflection requires more control force from you, the pilot. Said another way, when nose heavy, the tail must work harder to maneuver the airplane in pitch, requiring more force on the stick.

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Thanks, Bill. That makes more sense.

Fantastic discussion

This is indeed a great discussion, with many good comments from everyone. I thought I would resonate with just a couple of them.

One of the main reasons that stick force gets light when you are slow is that there is just less dynamic pressure, so it takes less physical forces for everything. Of course this is true of certified airplanes too. So various things are often done to augment the stick forces for feel. In my sailplane, the stick forces are completely synthetic, with springs. The elevator is so small, I doubt you would feel much of anything without the springs. I know the Cirrus SR-22 is full of springs too, perhaps other GA airplanes are too.

The RV's have a pretty low aspect ratio wing, which puts lots of downwash on the tail. The change in downwash with angle of attack reduces the stability contribution from the tail, but not the control effectiveness. I have not thought all the way through how this would effect trim forces, but it may partly explain why RV's are more sensitive to c.g. change than certified airplanes usually are.

Rob Byers hit it perfectly with the distinction of stick position vs stick forces. If you give me the stick position for trim vs speed, I can do a set of companion aero analyses (vortex-lattice) that, in combination with the data will tell you the static margin. I've occasionally thought about trying to set up a quick-and-dirty system for measuring stick position.

AndyRR brought up a question about servo tab. Yes, that is one of the reasons that tabs are used for is to modify the stick feel. I wouldn't suggest doing that to an RV - its a somewhat subtle business to get the tab gearing right, etc. to do all good things and not bad.

AndyRR brought up another thing that is worth discussing, and relates to everyone's comments about just being ready for the light forces and/or force reversal. Up-trimming on downwind, so that it takes some fwd force to stay at approach speed, and then during flare, the fwd force is reduced. This is a worthwhile human-factors question - does it help the human to have already biased toward forward pressure moderation, rather than moderating aft pressure and suddenly adapting to force reversal? Based on my experience with gliders, when you are on tow, you usually have fwd pressure. You adapt to it fairly quickly. Once adapted, that might be a better condition to start with as a human in the loop controlling the flare.
The trade-off would be the increased risk of getting too slow on approach when lots of things are happening and you might loose track of speed. So this is definitely a pilot judgement/skill/workload issue, but worth considering.

I hope everyone takes to heart Kevin's point about exploring this progressively with sand bags instead of loved ones in the back. I certainly will. And I guess I better learn how to wheel land better too

Thanks everyone, this has been very timely for me and, sounds like a few others, that are just approaching this step in phase I, and nice to know what to look out for.

I've spent the last few flights progressively moving the CG aft with ballast, doing some testing and circuits at each loading. Yesterday I finished the testing at the aerobatic aft CG limit.

I found the following stick free static longitudinal stability results:

With full flap, at idle power, trimmed for my current final approach speed (70 kt IAS), the stick free static longitudinal stability is almost neutral for speed reductions. The stick force to stabilize at 60 kt was an estimated 0.1 lb pull force. The longitudinal stability for a speed increase was slightly stronger, but still quite low. A 0.5 lb estimated push was required to stabilize at 85 kt.

With full flap, with power set for a -3 deg flight path angle (e.g., a standard ILS approach), the stick free static longitudinal stability is essentially neutral, with zero stick force required to stabilize at 60 kt after having trimmed at 70 kt. The stick force required to stabilize at 85 kt was an estimated 0.1 lb push.

At typical cruise speeds, and at high speed, the stick free static longitudinal stability was quite positive at both idle and full power.

At Vy with flaps UP, and full power, the stick free static longitudinal stability was noticeably negative for speed reductions. The aircraft was trimmed at 95 kt, and an estimated 1 lb push was required to stabilize at 80 kt. If the stick was released, the speed would continue to decrease to the stall. If the speed was increased to 115 kt, with the aircraft trimmed at 95 kt, an estimated 0.5 lb push force was required, indicating light positive stability for the speed increase.

At Vx with 1/3 flap, stick free static longitudinal stability was quite negative for both speed decrease and speed increase.

Bottom line - at aft CG at low speed, and especially with high power, pilots must pay very, very close attention to airspeed. You can't simply trim the aircraft for a speed and expect it to stay there. Climbs at Vy in IMC require particular attention.

Notes - as expected, these tests showed the classical destabilizing effect of power on a propeller aircraft with an engine on the front of the fuselage. Aircraft with lower powered engines (mine is 200 hp) and/or a fixed pitch prop would probably show slightly better stability at high power. But, I suspect they would still exhibit negative stick free static longitudinal stability at low speed with maximum power.

Things will be even worse at the full aft CG limit. I haven't decided yet whether I will go to the trouble to find some more dense ballast to allow me to ballast to even further aft, as it looks like the CG range I have tested will cover all the loadings that I will ever need.

Kevin Horton said:

At Vy with flaps UP, and full power, the stick free static longitudinal stability was quite negative for speed reductions...


... Climbs at Vy in IMC require particular attention.

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Would it be too alarmist to suggest that this is verging on dangerous?

I cannot imagine you want negative stability in a potentially high-stress, high-workload inadvertent IMC scenario where climbing away from known(?) terrain might be a sound solution (in a valley, for example)

Andy_RR said:

Would it be too alarmist to suggest that this is verging on dangerous?

I cannot imagine you want negative stability in a potentially high-stress, high-workload inadvertent IMC scenario where climbing away from known(?) terrain might be a sound solution (in a valley, for example)

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I do agree that this is not a good characteristic, and you can certainly imagine situations where this could lead to an accident. But, the accident history so far suggests that pilots are either able to deal with this characteristic, or perhaps there are not many climbs at low altitude in IMC.

There are a few things working in our favour here:

1. The pitch attitude must get ridiculously high before the aircaft will stall with full power.
2. The airspeed must get very low before the aircraft stalls (I saw stall speeds with flaps UP and full power of about 48 kt IAS, at about 1780 lb weight).
3. The stall is quite noticeable (sharp left wing drop and nose down pitch on full power stalls, on my aircraft), and the aircraft recovers quickly from the stall if the pilot applies conventional inputs.

Safety will be improved if pilots are aware of this characteristic. Hopefully all RV owners are doing a full set of flight tests that cover the whole CG envelope, rather than simply "flying off the hours". Note that I use the word "owners", rather than "builders", as these tests are just as important for the guy who bought an already flying RV as they are for the guy who built his.

Outstanding work Kevin - I knew we'd all be benefiting when you got back in to Phase 1!

Your quantified data correlates very well to the qualitative handling qualities evals I did.

Paul

Ironflight said:

Outstanding work Kevin - I knew we'd all be benefiting when you got back in to Phase 1!

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.....and Kevin, might I add that we are all very thankful to have someone with your brains and particular job skill set here on VAF.