Tail a dragging

I am in the test flight mode in my new RV-4. I know this model is pitch sensitive so before giving rides I want to make sure I know how this airplane flies with weight in the back. I have gradually added weight to the rear seat and today i was carrying 160 lbs. Take off was as expected. No problem. The landings were an adventure. My approach speed was around 85 mph. When i got to the normal 3 point landing configuration the nose wanted to pitch up more that usual. Knowing i could not push the stick forward i kept pulling it back until it quit flying and plopped down on to the runway. It did not feel stable or safe and was not pretty. What am I doing wrong? I had two notches of flaps. Should I use full flaps? Should I come in with more speed and use two pint landings?
Thanks, in advance, for your help.

What do you mean by, "When I got to the normal 3 point landing configuration the nose wanted to pitch up more than usual?"

Did you receive an uncommanded pitch-up? Or are you judging "the normal 3 point landing configuration" by reference to stick position, and got more pitch than you were expecting?

How close are you to the aft c of g when you have 160 lb in the back?

- mark

In my -4, I’ve flown as heavy as 235 lbs in the rear.. when I do, I wheel land it,

Sully73 said:

...the nose wanted to pitch up more that usual. Knowing i could not push the stick forward i kept pulling it back until it quit flying and plopped down on to the runway...

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Not a TD guy here, but have landed with far aft CG. Why do you state that the stick can only go backward? IMHO, the pilot needs to move the stick to whatever position is necessary in order to keep the pitch attitude where it needs to be for that phase of flight. In a far Aft CG scenario, that is going to be more stick fwd than in a Fwd CG state. You can think of CG as an elevator multiplier - Aft CG is additional up elevator and Fwd CG is like down elevator. If the nose pitches up too far, why would the stick not go forward to bring it back down? what am I missing here? Your logic seems counter to the basic elements of flying and following that would seem to be a recipe for inducing stalls. Stalling at 70 MPH is going to start creating PIO's (pilot induced oscillation) for you. Not a CFI either, so not providing instruction here.

My 10 has a pretty wide CG envelope. With just me (fwd CG), I have the elev trim 3/4 of the way to full up. At gross (Aft CG), the elev trim is neutral. Landing the plane is a completely different experience between just the pilot and full gross. WAY less elev pull at gross (aft CG)

Pitch forces naturally become lighter as the CG moves aft. You just have to be more careful with the amount of elevator force you use in the flare with an aft CG. It might be better to plan on making wheel landings when loaded that way until you get comfortable with the feel. No, I don’t think you need more speed. 85 mph (74K) should be about 1.4 vs at your gross weight, which is a little fast if on a non maneuvering leg in the traffic pattern (final). You might want to try a few stalls at your loaded test condition up high, like 5,000’ agl. Practicing slow flight in that configuration is a good idea too. Make sure you do a weight and balance calculation first to make sure you’re in the CG envelope, and realize that your CG moves aft as you burn fuel.

newt said:

What do you mean by, "When I got to the normal 3 point landing configuration the nose wanted to pitch up more than usual?"

Did you receive an uncommanded pitch-up? Or are you judging "the normal 3 point landing configuration" by reference to stick position, and got more pitch than you were expecting?

How close are you to the aft c of g when you have 160 lb in the back?

- mark

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Hi Mark,
The aft edge of the CG window is 77.4 and i am currently at 76.4 with 160 lbs and 27 gallons of fuel. So I am inside the envelope but nearing the aft edge.

When I say "pitch up".. after I flare I typically hold the nose up until I touch down. When I have 160 lbs in the back seat the nose seems higher than normal. I probably need more practice.

Scott Hersha said:

Pitch forces naturally become lighter as the CG moves aft. You just have to be more careful with the amount of elevator force you use in the flare with an aft CG. It might be better to plan on making wheel landings when loaded that way until you get comfortable with the feel. No, I don’t think you need more speed. 85 mph (74K) should be about 1.4 vs at your gross weight, which is a little fast if on a non maneuvering leg in the traffic pattern (final). You might want to try a few stalls at your loaded test condition up high, like 5,000’ agl. Practicing slow flight in that configuration is a good idea too. Make sure you do a weight and balance calculation first to make sure you’re in the CG envelope, and realize that your CG moves aft as you burn fuel.

Click to expand...

Thank You Scott, All good advice. I will head out to the practice area today for stalls and slow flight. In the current configuration my CG is at 76.7 and the aft edge of the envelope is 77.4.

lr172 said:

Not a TD guy here, but have landed with far aft CG. Why do you state that the stick can only go backward? IMHO, the pilot needs to move the stick to whatever position is necessary in order to keep the pitch attitude where it needs to be for that phase of flight. In a far Aft CG scenario, that is going to be more stick fwd than in a Fwd CG state. You can think of CG as an elevator multiplier - Aft CG is additional up elevator and Fwd CG is like down elevator. If the nose pitches up too far, why would the stick not go forward to bring it back down? what am I missing here? Your logic seems counter to the basic elements of flying and following that would seem to be a recipe for inducing stalls. Stalling at 70 MPH is going to start creating PIO's (pilot induced oscillation) for you. Not a CFI either, so not providing instruction here.

My 10 has a pretty wide CG envelope. With just me (fwd CG), I have the elev trim 3/4 of the way to full up. At gross (Aft CG), the elev trim is neutral. Landing the plane is a completely different experience between just the pilot and full gross. WAY less elev pull at gross (aft CG)

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Hello and thanks for your reply. TGs are quite different from tri-cycle gear. Always an adventure for me ;-)

Taltruda said:

In my -4, I’ve flown as heavy as 235 lbs in the rear.. when I do, I wheel land it,

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Thanks Tom, I will practice wheel landings today

Sully73 said:

Hi Mark,
The aft edge of the CG window is 77.4 and i am currently at 76.4 with 160 lbs and 27 gallons of fuel. So I am inside the envelope but nearing the aft edge.

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How about with 5 gallons of fuel? Remember, as stated before, your CG moves aft as fuel is burned!

Sounds to me like you may have been too high when you tried for the 3-point. Remember, you have another control at your disposal called the throttle.

Personally, I always prefer wheel landings, even if the tail is just about to touch down. I like flying the aircraft all the way through the landing.

-Marc

Landing an RV-4

Sully73 said:

I am in the test flight mode in my new RV-4. I know this model is pitch sensitive so before giving rides I want to make sure I know how this airplane flies with weight in the back. Knowing i could not push the stick forward i kept pulling it back until it quit flying and plopped down on to the runway. It did not feel stable or safe and was not pretty. What am I doing wrong? I had two notches of flaps. Should I use full flaps? Should I come in with more speed and use two pint landings?
Thanks, in advance, for your help.

Click to expand...

First: The RV-4 is a sweet-flying airplane.

I have tried several modes of landing and have found, regardless of loading, SuzieQ is MUCH happier with wheel landings. Usually with tail low but wheel landings. You can float down to the runway and just hold her off and she will settle onto the runway without a lot of bounce back. I can't remember the last time I three-pointed either SuzieQ or the Cub. SuzieQ likes to quit flying with the tail wheel on the ground and slam down the mains. I always use full flaps on final for a better view of the runway, and slower more controlled landing speeds. And use the throttle!! It is one of your "controls"!

Van has said more than once that EVERY time you go up, you should practice SLOW FLIGHT. Go up and wallow around near the stall speed and do some stalls, no power, power on. Get use to what your (new) airplane feels like at different speeds and weight distributions. I have had 190 back there. It was....different....but never felt out-of-control. You just need to be aware it will be WAY more sensitive with aft loading.

IMHO, YMMV

this is not an issue specific to the RV-4 or tailwheel aircraft, if you are inside the CG envelope as you stated, wheel land.

It helps if you increase your speed. And at some aft CG location you may find that you are pushing the nose down to stay on your flight path.

All the way at the rear CG, I use 75 KIAS and push the stick forward on final to wheel land. Good luck!!

When I have a lot of weight in back...

I add nose down trim to give more control feel just for the reason you are stating. Not too much, but enough to require a definite light pull to raise the nose.

I don't really want to admit the weight of the heaviest person I've flown with in back, but when I did I added weight to the battery compartment. Also, I moved my battery to the right side engine mount.

What Brent said..

I almost always fly 2 up in my -4, and have had plenty of 200 pounders in back. I always fly full or above half full tanks for added FWD CG with backseater. My speeds aren't really changed at all for landing, but I always use enough down trim that I'm actually pulling pressure slightly. if your trimmed for normal zero stick pressure, the first go-around you make will likely frighten you, as the nose will sky rocket and you will be hard pushing the stick to keep the nose down. I have long gear on my -4 and almost always 3 point..it will "roll on" the tailwheel first sometimes. You will get used to the pitch sensitivity, and it will be a non-event after a few times.

The weight in/on the back seat is irrelevant. What matters is the CG location.

plenty of light -4s out there with wood props and 320s. there is no way to put the same amount of weight on the back seat that you would be able to in a constant speed 360 -4. That 320 configured aircraft would be out of CG limit. some have helped their situation by adding a 17-18 lbs crush plate.

just trying to make sure you don't use those numbers for passengers blindly.

It is possible that you are experiencing "negative stick force gradient" near the aft end of the c.g. envelop.

This is not unheard-of for RV-4s and RV-8s at aft c.g.

The characteristic is that as you slow from a trim setting, the airplane wants to continue to slow more and it takes forward stick pressure to keep the airplane from pitching up further. This can be quite disconcerting.

As others suggested, it would be good to go up to altitude and do some slow flight to explore the situation. One way to alter this characteristic temporarily while exploring slow flight at aft c.g. is to set the elevator trim to different positions. For example, try trimming for a speed slower (more nose up) than your slow-flight speed. This way, you will have forward pressure to maintain a constant speed. Then see if reducing the speed results in more forward pressure or less. Next trim for a speed that is faster than slow-flight speed. It will require back pressure on the stick to maintain slow-flight speed. Then see if more or less back pressure is required to fly a little slower or a little faster.

If you do find that you do have negative stick force gradient at low speed with aft c.g., you can PM me to discuss possible remedies.

Axel is right

AX-O said:

The weight in/on the back seat is irrelevant. What matters is the CG location.

plenty of light -4s out there with wood props and 320s. there is no way to put the same amount of weight on the back seat that you would be able to in a constant speed 360 -4. That 320 configured aircraft would be out of CG limit. some have helped their situation by adding a 17-18 lbs crush plate.

just trying to make sure you don't use those numbers for passengers blindly.

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Agreed. Yes, you still must do a weight and balance...

My 2cents worth

Sully73 said:

I am in the test flight mode in my new RV-4. I know this model is pitch sensitive so before giving rides I want to make sure I know how this airplane flies with weight in the back. I have gradually added weight to the rear seat and today i was carrying 160 lbs. Take off was as expected. No problem. The landings were an adventure. My approach speed was around 85 mph. When i got to the normal 3 point landing configuration the nose wanted to pitch up more that usual. Knowing i could not push the stick forward i kept pulling it back until it quit flying and plopped down on to the runway. It did not feel stable or safe and was not pretty. What am I doing wrong? I had two notches of flaps. Should I use full flaps? Should I come in with more speed and use two pint landings?
Thanks, in advance, for your help.

Click to expand...

With over 1,000 hrs in my -4, I found that with a full sized passenger in the back, it was difficult for me to be very smooth in my touch down. Despite lots of pilot inputs, the tail would "squat" down just before touchdown as my speed bled off. At one point, I warned "full-sized" passengers to expect a plop vs a greaser.
Found that wheel-landings with passengers were up to my smoothness standards.
My -4 had a IO-320 with a constant prop, so plenty of weight up front.

CG rules (as Axel stated earlier).
Daddyman

The characteristic is that as you slow from a trim setting, the airplane wants to continue to slow more and it takes forward stick pressure to keep the airplane from pitching up further. This can be quite disconcerting.

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Encountered the same on my 6.9i. Took off MTOM on aft limit CG, and kinda surprised at the airplane rotating on its own.
The bigger surprise came when, brain certainly subdued by the awesome scenic floating icy bits in the chilled waters of the Davis Strait, exiting a first loop I had to positively push forward to prevent a second one from happening...

Rear CG definitely can change neutral into negative stability, beware.