---------------------------------------------------------- RV4-List Digest Archive --- Total Messages Posted Fri 07/06/07: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 03:58 AM - Re: Landing a loaded RV-4 (Rob Ray) 2. 04:38 AM - Re: Landing a loaded RV-4 (Steve Schlieper) 3. 06:34 AM - > Re: Landing a loaded RV-4 (Oldsfolks@aol.com) ________________________________ Message 1 _____________________________________ Time: 03:58:50 AM PST US From: Rob Ray Subject: Re: RV4-List: Landing a loaded RV-4 Jim, In simple tems I use a limit of 200lbs total aft of the roll bar in my 160HP wood prop RV4.Carrying heavier folks I add fuel which helps CG. A Landoll dampener, changing to an Odessey batter and mounting it on the firewall all helped. I personally only give rides to cute girls under 115 lbs...your call... Rob Ray 15,000 gallons burned, RV4 jamesbaldwin@dc.rr.com wrote: James Baldwin wrote: > Pat - > From a theoretical point of view I'll give you one answer: the real simple version. I don't have my reference book in front of me but what we're obviously talking about here is called static longitudinal stability. It has everything to do with what you are experiencing and is strictly a function of loading and the resultant location of the center of gravity (CG). As the CG moves rearward it approaches the location of the lift line of the main wing. The tail, for positive static stability, acts downward and (I am ignoring some cases where unusual moments or other aerodynamic effects alter this case) is the variable controlled by the force at the control, or in the case of an RV, the stick. Obviously as we all experience, the forces required by the horizontal tail vary with airspeed, thus the need for trim. As the CG gets close to the lift line location longitudinally, due to passenger or baggage loading, the force required downward by the horizontal tail is less and less. Since the downward force required is becoming smaller as we load more into the rear seat and baggage area it becomes more sensitive to small stick movements. At the neutral point the tail does nothing but you'd better HANG ON! > That's a real simplistic description of what is going on here. RV4s with lightweight starters, wood props, no mags, etc already have a rearward bias to the location of the CG and thankfully the arm for these weight savings is pretty small. I know of one RV6 in particular that has the opposite problem since he is using an IO360 angle valve with a CS prop. He runs out of elevator in the flare! He can't do a full stall landing. What's the solution? Well, put a CS prop on it. Put an O360 up there. Is the battery located way up front? Doing something like this is pretty radical so the other way to look at it is to actually measure the location of the CG and compare it to what Van dictates as practical limits. I'm going to guess that you guys are exceeding the rearward limit that Van specifies as acceptable for decent handling. I don't have the weight and balance information in front of me but if I remember I think the limits were something like 15 to 30% MAC (of the mean aerodynamic chord). The way you find out where you are REALLY flying is to get three scales and fully load the airplane in a level attitude just the way the builder did when he finished building, only do it with a load the way you actually fly it. You and your pax (or weights) sit in there and then you do the math after getting the weights from the scales. Now you know what the problem is if my suspicions are correct: you are outside the weight and balance limits set by Van for your aircraft. Van knew enough to put a margin in there for all of us but he also flew enough stuff to know he had to demand handling characteristics for the "least common denominator" pilot. If I were you, I'd find out where my CG REALLY is and quit trying to defeat the physics of flight we all must deal with. Out of the envelope operation can only lead to disaster when coupled with other factors such as wind, weather, low fuel, short runways, engine out, etc. Using a forward trim does not change the effects of a poor loading scenario. In fact it does not change the slope of the plot of the longitudinal stability (dcm/cg) line either, it just makes the controls feel better. > My guess is you'll discover you are operating your airplane outside the planned envelope and probably you need something more capable. Go see John Harmon -- he has this thing called a Rocket. JBB > > ps -- a big ps here: I can imagine there maybe might be one or two cases out there where some error in building might bias the CG or wing location which would adversely affect the normal passenger load handling characteristic, but probably not, it's probably plain and simple weight and balance. > > PGLong@aol.com wrote: >> Help.......I have an RV-4 and am experiencing landing problems with a rear seater present. I installed a Landoll Harmonic Balancer and according to weight and balance, should be able to tote a 225 pounder and stay within CG limits with correct fuel loads. Even with a 120-150 pound person in the rear seat, the elevator controls are so light it's almost like moving nothing. Not sure if I'm over controlling, but it is so easy to get a hip hop dance down the runway. Friend said to try and use a significant amount of down elevator trim to help. Haven't tried that yet but will next flight. What works for others? Just stick with wheel landings? Lots of friends that would like a ride, but hate to threaten them while I learn new techniques. >> >> Pat Long >> PGLong@aol.com >> N120PL >> RV4 >> Bay City, Michigan >> 3CM --------------------------------- Looking for earth-friendly autos? Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center. ________________________________ Message 2 _____________________________________ Time: 04:38:59 AM PST US From: "Steve Schlieper" Subject: Re: RV4-List: Landing a loaded RV-4 Pat, What is your empty weight for your RV4? Mine is 995, which is about 80 lbs heavier than the planned target of 905-913. With that in mind and running my own W&B numbers I never even considered anyone over 150 pounds for the rear pax with full fuel and an empty rea comparment. I only have about 25 hours in mine, so some insight would be valuable. I have an 320H2D up front with fixed pitch prop, so I am pretty much standard with a standard VFR panel. Steve D. Steven Schlieper 8 Homeplace Topsham, Maine 04086 Tony Blair's comment... In case we find ourselves starting to believe all the anti-American sentiment and negativity; we should remember England's Prime Minister Tony Blair's words during a recent interview. When asked by one of his Parliament members why he believes so much in America, he said: "A simple way to take measure of a country, is to look at how many want in... and how many want out. Only two defining forces have ever offered to die for you: 1. Jesus Christ 2. The American G. I. One died for your soul, the other for your freedom." ----- Original Message ----- From: Derrick Aubuchon To: rv4-list@matronics.com Sent: Friday, July 06, 2007 12:09 AM Subject: Re: RV4-List: Landing a loaded RV-4 Hi Pat, I have about 500 hours on my 4, and this is what I have picked up over the years,, 225lbs,, for MY airplane, is pretty much at the maximum I would have in the rear seat. My basic, "no-brainer" limit is 200lbs. Anything over that, then I have to start some serious figuring. That 200lb self-imposed limit assumes my usual load of stuff in the baggage area,, small tool kit, canopy cover, quart of oil,, etc. Above 200lbs,,, everything in the baggage area comes out. Next is fuel. As the fuel burns the aircraft cg slips aft, which exacerbates the situation. So I will always start with full tanks and keep the legs short with a heavy load in the back As mentioned in your post, the forward trim trick is very important. It gives the stick somewhat of a "preload," for lack of a better term and negates most of the effects of hardware slop in the control system. As an added bonus, after time,,, you will be able to get a feel for the effectiveness of the trim, and adjust the airspeed over the fence accordingly. Just my two cents,, Derrick Aubuchon RV-4: N184DA Jackson/Westover -Amador County (O70) daubuchon@volcano.net On Jul 5, 2007, at 11:25 AM, PGLong@aol.com wrote: Help.......I have an RV-4 and am experiencing landing problems with a rear seater present. I installed a Landoll Harmonic Balancer and according to weight and balance, should be able to tote a 225 pounder and stay within CG limits with correct fuel loads. Even with a 120-150 pound person in the rear seat, the elevator controls are so light it's almost like moving nothing. Not sure if I'm over controlling, but it is so easy to get a hip hop dance down the runway. Friend said to try and use a significant amount of down elevator trim to help. Haven't tried that yet but will next flight. What works for others? Just stick with wheel landings? Lots of friends that would like a ride, but hate to threaten them while I learn new techniques. Pat Long PGLong@aol.com N120PL RV4 Bay City, Michigan 3CM Do Not Archive ------------------------------------------------------------------------- --- See what's free at AOL.com. href="http://www.matronics.com/Navigator?RV4-List">http://www.matronics .com/Navigator?RV4-List href="http://forums.matronics.com">http://forums.matronics.com ________________________________ Message 3 _____________________________________ Time: 06:34:37 AM PST US From: Oldsfolks@aol.com Subject: RV4-List: > Re: Landing a loaded RV-4 I have landed our first RV-4 with a 240 pound pass. and had to use FORWARD pressure on the stick on short final to keep the tail up !! I haven't done THT again but the RV-4 has a lot of control authority. You are talking mostly about flying techniques. The trim should be used to set your airspeed for the pattern when you are downwind and slowed to the proper speed ( I like 60 MPH) then I like to carry about 1000 RPM to control descent rate ( More if needed). If you don't slow down to a full stall landing , you will bounce and go flying some more. Wheel landings are for those who can't fly a proper approach and can result in a broken prop ,or worse, if you get ham-handed. Bob Olds 700 hrs in our first RV-4 and 63 in the second ( From our 1100 foot grass strip ). ************************************** See what's free at http://www.aol.com. ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rv4-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RV4-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rv4-list Browse Digests http://www.matronics.com/digest/rv4-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.