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It’s an RV-15 Grin - an interview with Van's test pilot Axel Alvarez

Q. I'm with Axel Alvarez from Van's Aircraft. Good morning, Sir, how are you doing? A. Well, yourself! Q. Good. Alex, team Vans has the RV-15 prototype here again like last year with some changes. I remember a wonderful article in Kitplanes by Paul Dye, describing the nomenclature often used in the development arena, from a test unit all the way through the pre-production prototype. With that said, where would N7357 lie within those stages?Axel Alvarez- A test pilot for Vans Aircraft A. So, the aircraft that you see here ahead of you is the one that we brought last year with some quotation mark changes, It's a prototype. It was always intended to be a platform where we could make changes, push the boundaries, and find answers. For example, it's the same fuselage however, this is the fourth horizontal stab that we put on it. The vertical is the second vertical stab that we put on, and the rudder is the third rudder. So, we've continued to find answers to make the model better. On the horizontal, we've extended the area 10 inches on either side, which gave us 4.3 square feet of additional area. When we brought the aircraft here, it was tested to a very small, limited envelope. So, flaps two, was the flaps setting that we chose to use to get the airplane here (2022), and now we tested it to flaps four, which is 50 degrees, and that made us think, okay, we may need a little bit more area here. The other thing that we did with the tail was we tied the horizontal trim tab and the anti-servo tab together. Before they were independent, and they could potentially move in opposite directions, now we have additional area and coupled. The rudder was really light, and by just resting my foot on the pedal, it would throw the ball off. So, we cut the counterbalance way down to half its area, and it was still too lively. That's why we removed it completely, and now the forces are closer to where we want it to be. Throughout the airframe, what we've done is try to get the airplane to be close in forces, so one axis is not heavier or lighter than the other. The first flights, the forces were too light, and the ailerons forces were heavier. We've been changing the hinge points on the ailerons, to lighten those forces up. So those are some of the changes that we've made. However, we want to keep some ratios (wing to tail). We're going to move the wing aft in order to allow for a larger range of engines, so it can accommodate an engine from something that is 340-ish, with a light Cato prop to an IO-390 with a constant speed prop. In order for us to do that and allow weight in the baggage area, we have to make something change, but we have to keep the same geometry so the tail needs to move back to same amount. The landing gear point moves back at the ground four inches. Q. Alex let's recap the changes. A. So, the tail changes have been done and the wing move we can't do on this fuselage. Q. Because that's such a large change. A. Yeah, the movement of the wing is a significant thing. So, we will build a prototype kit. Basically, using the same techniques and the same things that we will release to a customer. So that's what's next in our roadmap. Q. Will you be at a pre-production prototype at that point? A. Yes. Q. Speaking of flight dynamics, this is a two-part question. Are you the only test pilot, and that job can be subjective in terms of how the airplane feels, however, you're also using sensors to get actual feedback via data logging, what forces/data are needed to get more of a numerical sense as to where you want to be? A. I am the only person that's actively looking at new data. So, from the test pilots' point of view, I am reaching for new data, bringing it back to the team, we make choices, and we go back at it. However, I am not the only one that's flown the aircraft. Several other folks have flown the aircraft at this point for half an hour, an hour here and there, but as far as actively searching for new data, it's just me. Once we do something that I feel as though it's a big change that's positive, then we get Van, Ryan, or Scott to fly it. So, the data they're collecting is a different type of data. It's within the envelope that I've already cleared for the aircraft. Second part of that question, the data side. So, data comes in, in many different ways, right? Data can be how we perceive something. Q. Ah, Human perception. A. Yes. You know, we want what we call the "RV Feeling", but what does that mean? It's just nice balanced forces, easy to fly, just a joyful experience. So how do you describe that? You can't, and when I originally said, hey, the forces have to lighten in pitch, the folks had asked me how much and I will be guessing. At one point, I told one of the guys 3.5 pounds, that's just a guess. And the only way I could do that was we went and grabbed a fish scale, I closed my eyes and pulled, and I said, that's about what I feel and he looked at the number it was 3.4. So, I wasn't too far off, but that's not real data. So, we were figuring a way to add a load-cell to the aircraft. If you look at the aircraft, or take pictures of it and see it, you'll see a black stick, and a red one. The red one is a load-cell, and we can real time monitor how much force we're putting into the system. So, I know if it's 10 pounds, or five pounds, and it's also being recorded at 16 hertz through the system, and it's time synced to the maneuver. We also figured out a way to use the autopilots, the servo, and the throw of the servo to allow us to know where that control is throughout flight. So, at the beginning of the flight, I indexed all the corners and now we know the envelope. We know how many clicks are in between all those things and we have a full capability, we know exactly where the stick is, where the ailerons are, and where the trim tab is throughout the flight and we know the forces. So now we make a change to the airplane to reduce, improve, or increase the forces and we could go yeah, we went from nine pounds at that test point to eight and a half, or we went to 10 pounds. So now it's a numerical type answer instead of just a yeah, it feels about this. So, out of all the RVs, I think it's going to end up being one of the most tested RVs in our company because of the capability that all these advanced systems are bringing, they are really helping us right now. Q. With the aviation community being very diverse in terms of their careers, but one might say there's a propensity of people that are interested in things mechanical, vehicles, and the development therein. For that audience, this interview will be a lot of fun to hear. However, on your end, to notice the progress when you make changes, it's got to be real rewarding, we made a change, this is working great, etc. With that as a background, could you comment on the post flight debrief process with the team? A. Yes, so let me let me address a couple of things that you said there. Yes, here's the deal. It is gratifying, and it can also be very, very frustrating. Q. Yes, R andamp; D can have its moments. (As a side note, I spent a few years assembling prototypes of inventions, I can relate!) A. The control forces for the pitch for example, and I'll speak for myself are one of the most underrated things, and I did not put enough effort into thinking through that. We've spent a considerable amount of time making that right, making all those control forces work for us, and to be balanced. So yeah, it's great when you get it, is really frustrating when you spend weeks, and many hours of flight trying to go through the small changes and nothing's improving. You're not having an aha moment where it's like we knocked it out of the park with this. But when you get to that point where things work, it's amazing. So, let me address the other thing you mentioned, do we sit in a group and talk. So, in the test program I have purposely not done that with people, we have a very small core, it's myself and a chase plane. So, what I'm trying to say to you is this, on purpose, when someone is scheduled to fly it, I say the airplane is safe, these are your test cards, go fly. I don't tell them the performance, I don't tell them what I think until we come back, and then we debrief! The reason I've been doing that is because I personally don't want to plant a seed in their head of, it's too light, it's too heavy, harmonically is not right. And as soon as I do that, then they're already going to have that seed in there, and it may drive them to an answer, that it's not their own answer. So, we've been really careful with that, in fact that some of the pilot dailies that I send out after a flight, only go to the core people, and some of those folks haven't even flown the airplane yet. Once we fly, we spend some time debriefing, talking it through and how we're going to improve it. Q. In regard to the airplanes mission, it is definitely back country, however I don't think I've heard anyone on team RV-15 refer to it as STOL. A. Some folks go watch YouTube, and they think STOL is landing in 20 feet and taken off and 6 to 10 feet, you know, and that's great. But we also want to use the aircraft for a mission, and that mission is not just to land or takeoff short. It gets you there with your stuff, and then be able to do something with it afterwards.RV-15 Q. Sure, and with that said, I have an interest in aerodynamics and one of the arenas that interests me is the adaptation of droop leading edges for enhanced performance in the slow flight arena. Has this tech ever been considered as something to be incorporated during the RV-15's design and development program? A. So, designing an aircraft is all a compromise, right? So, you make those compromises in order to build your mission, whatever you want to support. If someone wants to build that into their missions, and that is a requirement for them, then they could do that on their own. For us, the way that we try to approach things and you'll hear folks around the company say no band aids. We just want to make a really clean aircraft design, that works. If someone wants to do something else, they can do that on their own, but we're going to try to give you the cleanest design possible with no band aids. And I'm not saying that that's a bad thing. I'm not saying a slat is a band aid, but we need to understand when you do something, how that affects the compromise, right? We put droop-tips, and now maybe the aircraft's handling qualities becomes not as docile, right, you can't roll this as fast, it's more stable than you want it to be in some cases, or, you know, you start putting slats on the aircraft, and now you can't see necessarily where you're going to land, right. So, all compromises are compromises, make it nice and clean, and then go enjoy it. The biggest thing for us is to have balanced controls throughout the flight envelope, and we will work continuously until those forces are beautifully harmonic. Once we get there, then we can start adjusting things aerodynamically to optimize it here or there. But if we could get to that goal that it just flies great, The RV Feel, then we're doing our job. The biggest thing I'm trying to explain to people is what it is like, because RV builders and pilots have never experienced an RV like this. So, you know that the phrase RV-Grin is out there, and we all know what that means, right? Well, this is going to be an "RV-15 Grin". That is just a different "Grin". It's you land in 140 feet, and you don't touch the brakes, and you just keep taxiing to the exit. When you take off, you're climbing 1800, 2000, 2200 feet per minute, at a 22-degree angle and you're looking around, just giggling inside, right! It's an RV-15 Grin, and I'm sure that will coin that at some point. People will understand what that means later. Q. On that note, you've given me the title for this interview, thank you my friend. A. Very well. Thank you, Anthony. 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