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Weight in back ?

Hello -
I'm considering the purchase of a 4. I have little - make that no - experience with them. One thing I've been told is weight and balance can be tricky. Plane weighs about 1000lbs. o-360 and metal prop on the front. What should I expect for the max weight for a passenger, with nothing in the baggage compartment?
Thanks.
 
You will need to run the W&B for your particular airplane, pilot weight and fuel load scenarios. Maybe some -4 drivers can give you an estimate, but it will be just that.
 
W&B RV4

My RV4 was 980# 0320 and CS up front. Plane sold and don't have my W&B numbers anymore. I could carry a 220# passenger, no luggage and I was fine. When I added a CS prop to the plane it changed the CG a lot.

Steve
 
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I have a 360 with constant speed. I can go up to almost 300 in the rear. However, I never would. With my 230lb son in the back it is real twitchy.

You will need to run the numbers on each plane, they very a lot by equipment and equipment placement. The more weight in front the more you can put in back. Prop type and material, battery type and location, starter type, mags or electronic all make a big difference.

Bob burns
 
http://www.vansaircraft.com/public/rv4specs.htm

1080+192(fuel)+220(passenger)=1492 lbs, without a pilot.
Were you a newborn at the time? ;-)

Van says empty weight should be 905-913. Admittedly, not many even come close to that, so unless someone used a higher number for gross weight when they got their a/w certificate, plus-sized passengers are going to be a problem from a legal standpoint, if nothing else.

I've owned two -4s; the 1st was 930 empty, and the current one is around 910. Both are O-320/wood prop a/c. Back when I'd just bought the 1st one, with only a few hours in it (lots of T-18 & Swift time earlier) I unknowingly took up a 235 pounder (he was...densely packed). Let's just say it was an adventure, getting it back on the ground. I was never in doubt that I'd get it right eventually, but he sure was, and he had been a back seater in F-4s.

Since then, with a lot more experience, I've flown several 200+ lb passengers. But absolutely no acro, no short strips (for takeoff), and caution on landing. With that much weight in back, the wood prop versions change from being pussy cats to demanding respect. Pitch forces get a lot lighter, even in normal flight. The 360 & metal prop will obviously help CG, but really eat into gross weight.

If you ignore the legal implications, and you're a good stick (in *that* plane; I've had a Marine fighter pilot scare me in the -4), then it will fly with 200 lbs in back. If it's a c/s prop, that obviously helps with takeoffs at high weights.
 
I recently looked at a -4 for a friend that was originally certified at #1500 gross. Over the course of 15 years the gross weight had arbitrarily been increased to #1600 and then #1700. All of this was done merely by the stroke of a pen. Experimental or not, this is totally illegal and unsafe! As others have stated, they become very twitchy (unstable) in the pitch axis as the CG moves aft. If you are the least bit skeptical about the W&B numbers on a particular aircraft, then have it weighed. They all seem to gain a few pounds over the years, but a glaring discrepancy should raise a big concern.
 
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Thanks much!
I realize W&B calculations are necessary. I would not fudge the numbers and want to fly me and anyone else safely. So - I was looking for some idea of how they fly from those who know. Certainly appreciate your help.
 
Setting aside all the WB, gross weight numbers and such, I can say from my experience in my -4, when you have a heavy back seat passenger, you need to learn the light pitch control inputs, as aggressive pulls in flight will easily over G the airframe, and when slow/landing one can end up nose high very quickly. I have a personal limit of 200lbs for a pax, but also have smoke oil tank behind.
 
My experience

I put 500 hours on a -4. In my experience, the Van?s published range is a pretty solid guideline to stay within. The handling feels best at the aft end of the range, but at that point, you?ll notice that not much rearward stick pressure is required in the flare.

Push the CG back any farther, and you?ll be pushing the stick forward in the flare, which puts you in a pretty narrow window of controllability.

When loaded with aft CG, I always found it best to use little or no flaps and land in a full 3-pt attitude (or even tail first).

I think the long gear setup is a slight advantage in tolerating aft CG landings.

Also keep in mind the CG moves aft as fuel is consumed.

(Opinion alert!) With these considerations, I have a slight preference for a more forward empty CG configuration in any RV-4 with a mission involving travel. Anything you put in the plane besides the pilot moves the CG aft, so a plane optimized for acro with an aft CG really can?t gross out in pax or luggage. Not that I would know, but in real safety terms I think most RVs have a much higher tolerance for exceeding gross weight than for exceeding aft CG.

Hope this bit of detail in addition to earlier posts is helpful.

Matthew
 
IO-320, Catto prop. 1500 max gross, 971 empty weight, 71.44 empty weight CG. With full fuel and me (180 lbs) my max back seat weight is 158 lbs using Van?s recommended CG.
 
0320 w/wood prop & 4" spacer; 1020 GW / 1500 Max / No more than 200lbs behind the roll bar for me. No acro at those weights. I've done light stuff (aileron rolls and lazy wing overs) with my mom that clocks in at maybe 105lbs. I've flown with my buddy ~230lbs in the rear; pitch wasn't scary sensitive but certainly noticeable. Plane flares itself after level off and never reached the regime of needing forward stick but I kept it to 3pts; a wheel landing definitely would have required it.
 
Spreadsheet

Happy to share an RV-4 weight and balance spreadsheet that allows you to input wheel weight and arms. These data should be available for any airplanes you are considering purchasing and you can run your own numbers...accuracy of the data varies, however. That’s why a trust but verify technique may be warranted and you should consider reweighing any “new to you” RV. Drop a PM or email and I’ll be happy to send it to you.

Each airplane is going to be a bit different, but handling characteristics do change with CG. If it’s a light nose airplane (O-320/wood or composite fixed pitch prop), you can experiment with different size crush plates to change the empty CG. If it’s a heavy nose (O-360/constant speed prop), empty CG is likely further forward, but you can run into max gross weight sooner. Just depends!

One other consideration is footwells, if you’ve got ‘em it’s easier to accommodate folks with longer legs, regardless of their weight—otherwise their knees can interfere with the canopy bulkhead behind the pilot’s seat.

If a four doesn’t meet your requirements and you like the tandem configuration, an eight might. The handling characteristics of a light nose four are as close as you can get to a three and occasionally share the fun with someone else...lots of discussion about CG effect on handling characteristics in the training manual over on the safety page...good luck!

Cheers,

Vac
 
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Wheeler or three point?

Ours has an O-320 and Catto prop, so not all that heavy on the nose. We've only gotten her a few months ago, and I fly mostly solo. My girlfriend (125 lbs), her 15-year-old daughter (about the same weight) and my 15-year-old son (not a whole lot more) have been the only passengers up till yesterday. And sure, she got a bit more pitch sensitive, but nothing to worry about.

Going with the Vans numbers, I could have someone up to 200 lbs in the back, so combined with the above experience, I didn't think much of putting a 170 lbs friend in the back. But boy, does that feel differently! Especially when flaring for landing.

I'm not exactly sure what happened. I started to flare lightly to make a slick threepointer. Or so I was planning. The nose shoots up in the air and I end up way behind the power curve. So I correct by pushing the nose down. No response. If anything, the nose went up further and for a moment it felt like control responses were reversed. Smaller inputs then, plus a dab of throttle to get some air over the tail and prevent me from dropping in from 10 feet. That seemed to smooth everything out, and a second later I was down on the runway safely.

It happened very quickly, and I find it hard to determine what happened. The gusty wind might have something to do with everything, but I feel the backseater certainly was a factor. I think next time I have a passenger, I'll wheel it on, rather than threepoint.
 
0-320E2D, Whirlwind GA prop 1988 RV-4.

195lb front seat pilot
228lb passenger
0lbs rear baggage

Using Foreflight W&B calculator (incredibly complicated to set up) yields 76.6 takeoff (full fuel), and 77.4 inches (zero fuel CG). Design limits as we know are 68.7 to 77.4 inches aft of datum.

My personal limit is 210 behind the roll bar. The Rv-4 goes from being a lamborghini to a Cadillac when you add a rear passenger.
 
Going with the Vans numbers, I could have someone up to 200 lbs in the back, so combined with the above experience, I didn't think much of putting a 170 lbs friend in the back. But boy, does that feel differently! Especially when flaring for landing.

I'm not exactly sure what happened. I started to flare lightly to make a slick threepointer. Or so I was planning. The nose shoots up in the air and I end up way behind the power curve. So I correct by pushing the nose down. No response. If anything, the nose went up further and for a moment it felt like control responses were reversed. Smaller inputs then, plus a dab of throttle to get some air over the tail and prevent me from dropping in from 10 feet. That seemed to smooth everything out, and a second later I was down on the runway safely.

It happened very quickly, and I find it hard to determine what happened. The gusty wind might have something to do with everything, but I feel the backseater certainly was a factor. I think next time I have a passenger, I'll wheel it on, rather than threepoint.

Hans I found keeping a little power to touchdown helped with pitch control. More airflow over the elevator. With a backseater, the -4 is a different airplane.
 
A couple of tips

I have 1100 hours in my -4 now, it weighs 975 (or so) with an O-360 and Catto prop. I did a couple of things to be able to haul a heavy passenger / (bags). First, I moved the battery into the engine compartment, in the right cheek. This allows a forward baggage compartment between the rudder pedals, so you can add weight forward of the CG. I usually put a bag of tools and heavy stuff like my O2 tank, oil, tie downs, etc up there.

Secondly, if I know I am aft CG, I always run the trim forward (down) so that I have more stick force and feel when I get slow with flaps down.

I like to land with half tanks or more if rear loaded.

I hope this helps.
 
-4 Question

I fly a -4 with a Sensi FP prop (43# w spacer). Empty wt is 1000#.
Am thinking about selling the Sensi, and installing a wood Prince, Pacesetter, or Catto. Will lose about 23-25# on the nose. I weigh 135#. Wife weighs 125#.
With half to full fuel, will I notice much difference solo vs 2 up?
With the Sensi, don?t notice much diff......
 
This is the CG/ Weight and Balance for my RV-4


WEIGHT & BALANCE DATA

Make: Van?s Aircraft
Model: RV4 Serial # 4354 Registration # N359DM

Datum= 60 inches forward of wing leading edge. (L.E.)
Design C.G. Range = 15% to 29% of wing chord, or 8.7? to 16.8 inches from L.E., or 68.7 to 77.4 inches aft of Datum.
Wing L.E. = 60?aft of datum.
Main wheel, right = 60?aft of datum.
Main wheel, left = 60.3?aft of datum.
Tail Wheel = 237.5?aft of datum.

Aircraft weighed empty in level flight attitude.

Weight (lbs) Arm (ins) Moment (lbs. in)
Right Wheel 484 60 29040
Left Wheel 499 60.3 30089.7
Tail Wheel 50 237.5 11875
Total: 1036 70997.08

CG=70997.08/1036 / = Empty moment of aircraft 68.53? aft of datum



Weight and Balance Work Sheet

Datum= 60 inches forward of wing leading edge. (L.E.)
Design C.G. Range = 15% to 29% of wing chord, or 8.7? to 17.4 inches from L.E., or 68.7 to 77.4 inches aft of Datum.
Wing L.E. = 60? aft of datum.
Oil = 40? aft of datum.
Fuel = 70? aft of datum.
Pilot = 82.5? aft of datum.
Passenger = 107? aft of datum.
Baggage = 130? aft of datum.

Gross Weight CG

Weight Arm Moment
Aircraft 1036 68.53 70997
Fuel 192 70 13440
Oil (8 qts.) 15 40 600
Pilot 180 82.5 14850
Passenger 160 107 17120
Baggage 5 130 650
Total 1588 11765.7
CG 11765.7/1588 74.09?

Most Aft C.G. (Gross Weight Min)

Weight Arm Moment
Aircraft 1036 70997
Fuel 30 70 2100
Oil (8 qts.) 15 40 600
Pilot 180 82.5 14850
Passenger 160 107 17120
Baggage 5 130 650
Total 1426 106317
CG 106317/1426 74.56? aft


Most Forward C.G. (Two Occupants.)

Weight Arm Moment
Aircraft 1036 70997
Fuel 192 70 13440
Oil (8 qts.) 15 40 600
Pilot 180 82.5 14850
Passenger 120 107 12840
Baggage 0 130 0
Total 1543 112727
CG 112727/1543 73.06 aft

Most Forward C.G. (Std. Pilot Wt.)

Weight Arm Moment
Aircraft 1036 70997
Fuel 30 70 2100
Oil (8 qts.) 15 40 600
Pilot 170 82.5 14025
Passenger 0 107 0
Baggage 0 130 0
Total 1251 87722
CG 87722/1251 70.12? aft


RV4 Weight and Limits ? easy Reference
Recommended Gross Weight 1650 lbs
Aerobatic Gross Weight 1375 lbs
Forward CG Limit 15% of cord or 8.7? aft of leading edge
Aft CG limit 30% of cord or 17.4? aft of leading edge
Aerobatic Aft CG limit 27.5% of cord or 15.9? aft of leading edge
 
Four-ward CG...

Hello -
I'm considering the purchase of a 4. I have little - make that no - experience with them. One thing I've been told is weight and balance can be tricky. Plane weighs about 1000lbs. o-360 and metal prop on the front. What should I expect for the max weight for a passenger, with nothing in the baggage compartment?
Thanks.

Bernie,
Good considerations. I finished my RV4 25 years ago after reading a magazine ad from Vans touting "Total Performance." The plans back then were pretty specific concerning aft CG and Aft of Datum loads. Building an RV4 gives you a distinct advantage as to the CG loading but it varies greatly depending (as mentioned above) on weight out front.
If nothing else, find a builders manual and read it through. You'll be glad you did.

My RV4 weighs 945lbs with an 0-320WD firewall mounted Odyssey battery, lightweight starter/alt and Catto prop out front. I set my max weight aft of the roll bar of 200 lbs. This was attained after several flights with a heavy passenger or some large parts I carried with the back seat removed. This included an air compressor, a disassembled 0-320, Honda Trail 70, etc...
I've flown just about every RV4 iteration over the years. The 0-360/Hartzell combo airplanes are a bit nose heavy solo but fly sweet with a 100lb pax. The 0-320/composite or wood, fly incredible solo or with a lighter weight pax. (pretty girls, grand kids etc)
I personally use fuel to manage CG as the tanks are forward of the datum which is right under your butt. Heavy load? Add fuel, empty back seat, fly lighter.

Like the F16, the RV4 for me is the most fun CG-wise approaching relaxed static stability, or the aft datum. :)

V/R
Smokey

PS:personally after 3000 hours, 25 years and alot of "yanking and banking", the 0-320/fixed pitch composite or wood is the preferred mode, but again, my mission may be different than yours.
I like simplicity, light weight and enjoy the occasional 1V1...
 
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I have been trying to shift weight forward in my RV7. Vans tool box kit was a fun project for my son and I and it fits well on the floor between our feet. I made some hold down brackets and painted it so it blends in with the floor. Now, all the tools I used to keep in back are up in front. Shifted CG forward with no change in flying weight.
 
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