Tricks for moving the CG aft:
Move weight aft: relocate battery, ELT,strobe power pack farther aft. Replace battery with heavier model. Carry spares aft (tire & tube), ditto tool kit. Heavier MLG tires if aft of CG.
Lighten up everything you can ahead of the CG: lighter nosewheel tire, alternator,starter,spinner. Remove vacuum pump & gyro's. Remove old boat anchor avionics.
I lightened my airplane up from 1,271# at 32.07" CG at purchase time, to the current 1227# at 33.23" CG. A lot of the changes involve only a small amount of weight or CG shift, but it all adds up.
Good luck with it,

Eric

Not my C175, mine is based at T27, is white, gold & bronze. You couldn't get field approval for a larger nose fork? That sucks. I too, am looking at going to a 6 inch on the nose and 700's on the mains. Oh well, I guess my next upgrade will be a sportsman's cuff.
Dave

Jaerl wrote: With just me in it with full fuel, I am right on the line of the forward limit. With two in it, I am out of the forward limit without anything in the baggage compartment.

Perhaps I am confused but if you can get within the forward CG limit while empty then adding fuel and pax will just bring it further aft. everything is aft of the datum; front seat +36 rear seat +70, fuel +48, and baggage is +95. So adding a pax will bring the cg further aft not forward.

I am dealing with a PMI at the Salt Lake FSDO and he is a really good guy and has been extremely helpful. They must have some reason for not being willing to do a field approve for you.

Whee Your right, everything you add moves the CG rearward. But the more the plane weighs, the farther aft the CG needs to be to stay within the envelope. My empty CG is at 35.70. The Pilot and passenger are at 36.0. The CG Envelop for my plane is almost a 45 degree angle. So when I add a passenger in front the weight goes up a lot more than the CG (or moment) goes back. With just me in there, I start out on the forward line so that's why it goes out of the forward limit.

I have dealt with two inspectors in Salt Lake and they have been helpful but neither will do either the Alternator or Nose Wheel. I have had a couple of guys here offer to help me with Field Approvals and I will do probably do that when the plane is ready to go somewhere. The reason the DER was given for not approving the Front fork is that it will add more weight and a longer lever. Thus, putting more stress on the firewall. I understand the longer lever part but if the plane is on the ground, the ground bears the weight. Seems like more rolling momentum should make it less prone to damage. The Alternator is a non TSO'd part made for an experimental.

I got the prop back on. It still has some vibration but everything has helped a little. Dynamic balance is next. The vibration is probably is just me comparing a low compression 6 to a high compression 4. My mech works on another one on the field and he said it seemed to shake too when he did a runup on it. Maybe just another characteristic of the conversion. I know the front of the engine is in the same place and I lost the two back cylinders with the conversion. Makes sense that the motor mount is longer and that could amplify any vibration in the engine or prop? I am going to check the motor mounts next time the cowl is off.

Rangeflyer, What model is yours, mines a "B"? I am out of town right now but I can send you some 337's if you want. I have two or three with different tires and one with the one piece 206 nosefork, 6:00 on the front and 8:00's on the mains. I also have one where the guy did his own extended baggage but the way things have gone with Salt Lake, I figured it was a waste of time. If I ever get my tires approved, your welcome to a copy of it too.

Jaerl wrote:Rangeflyer, What model is yours, mines a "B"? I am out of town right now but I can send you some 337's if you want. I have two or three with different tires and one with the one piece 206 nosefork, 6:00 on the front and 8:00's on the mains. I also have one where the guy did his own extended baggage but the way things have gone with Salt Lake, I figured it was a waste of time. If I ever get my tires approved, your welcome to a copy of it too.

Yes, mine is a "B" also. I would appreciate copies of the 337's, I may have better luck with the Albuquerque FSDO. I may be passing through that way on a trip to Oregon next month, where are you located exactly?
Dave

Hi Dave

I am at PVU or U77, just South of Salt Lake. I'll PM you my contact info. I am on the road right now but I can email copies of the 337's I have for 175's when I get home.

Jerry

I kinda remembered those cg charts from ground school but I have never used one and couldn't remember if the cg limits changed with weight. my plane is so simple that you dont have to calculate the cg as long as you are within gross weight, per the TCDS.

The PMI I am working with guided me to this:
http://fsims.faa.gov/PICDetail.aspx?docId=5FA5237B49DF80078625760800658B77
It is what they use for guidance when reviewing a field approval. In theory you can follow it and it will tell you if you are going to need a STC, DER, or just a PMI review with a 337.

My 205 required 19" and 2450 rpm to maintain elevator and rudder authority. I put micro vg's on the wings, vertical and horizontal stab, and what an improvement. I don't know what it would do for your plane, but this is what happened for me.

Pre VG's. Almost no authority at 75 indicated and potential trouble when near 70 indicated.

Post VG's: Can slow fly at 55 indicated with 40 deg flaps and make a 30 deg bank turn without a stall. Can cross the fence at 60 indicated (a bit noisy with the stall warning howling), but I have aileron, elevator and rudder control with the nose up in a comfortable position. It only gets better when I have it loaded for a camping trip.

Rich

Don't know what year 175 is being discussed, but the Microaero STC adds VG's not only along the wing, but on the vertical & horizontal stab's to add tail authority. That might do the trick, esp if you can bump the CG aft a bit by replacing or relocating some components. $1450 for the kit: microaero.com

As has been noted here, a weight and balance is critical. With the Avcon conversion and a C/S prop, you will find that you are out of CG forward. Now I have had to add weight to the tail on a Cessna 170B Avcon conversion and two 175TW Avcon conversions in order to get it into the envelope and make it land the way it should. After over 6000 hours of flying "off airport" with no problems with lead well secured in the tail, I would suggest that is solution. You need to bring the CG back in, otherwise it will take a lot of weight in baggage to do the same thing. The necessary amount of weight in the tail is the safer solution. My testing was done with a case of oil behind the back seat. Those of you who do not have this weight and balance problem in your airplane, don't have a real handle on the fix. A well balanced airplane is the safer and easier flying airplane. I have never had a ground loup either.

Fly 175B with 360 and constant speed. Most of the time the rear seat is out. Nose heavy and run out of trim. Changed to a light weight starter and did not feel much change. The CG calc did not change much either. It is hard to land without power. I do give power just as I start to flair. When traveling. Everything is against the rear cargo cover. I do carry a folding bike and small tool box, so the aft weight is there. I will think about a 35 battery when I have to change the battery box(soon). Will have to look at the STC to see if that is allowable. Battery is behind the cargo cover.
With two in front seats full fuel, it is a handful to keep the nose up on landing.
I know no help but weight in the aft seem like something that should not happen. the arm is harder to figure and torque is even harder. Fly and learn to keep the nose up and power is your friend.

This thread got me thinking (again) about adding Micro VG's to my C150/150TD. I have pretty good aileron authority (partially thanks to aileron gap seals) and pretty low stall speed already, but of course it never hurts to improve either one. I do seem to be lacking rudder authority when slow- if I push the tail up early in the takeoff roll, I don't have enough right rudder to overcome the P-factor & it'll head off to the left. The VG's up the vertical stabilizer should improve this situation. The VG kit for the 150 does not include VG's on the horizontal, but I seem to have plenty of elevator authority already so that's OK. Interestingly, while the kits for the 4-place Cessna's list at $1450, the kits for the 120,140, & 150 list at $695.
My main concern with adding VG's is that I mainly fuel out of 5 gallon cans, & it looks like the VG's would be in the way & constantly getting beat up. Anybody with VG's have comments pro or con on this?

Eric

Had VG's on my 182 and now the Bonanza and fuel out of cans regularly. The VG's are pretty tough. Put a towel down if your worried.

You guys are a bunch of help. I was afraid my plane might be set up different but looks like all the Avcon Conversions, and a lot of other planes, have the same characteristics. It wouldn't bug me so much but the 150 and my old 172 were balanced right in the center. It was easy to land either of them with the power off, stall horn blaring while keeping the nose wheel off the ground. I have always practiced landing as slow as possible and to keep the weight off the nose. Sometimes I practice touch and go's without touching the nosewheel at all in the 150. These 65 over the threshold, floating, tire squealing landings I don't like much. Won't be much good on short rough strips either.

Feedpro, how much weight do you put in the tail and where is it mounted? I have read that a lot of people do this and it seems the logical choice if I want to stay as light as possible. One guy took lead and used an old tail section of a wrecked plane, he poured lead in the tail and used the tie down ring to attach it. That would put the weight at 230" so it shouldn't take a lot of weight to pull the CG back.

The VG's sound like they might help too but I wanted to get a Sportsman STOL since I will never see the Horton I bought. Are the VG's removable if you decide to put on a STOL Cuff or paint your plane, and can you reinstall them on the STOL Kit once you take them off? If you guys had the choice of the two, which one would you get. Thanks

Jerry

used an old tail section of a wrecked plane, he poured lead in the tail and used the tie down ring to attach it.

That was my advice to you on a different forum. That method allows the lead to slide to the very back of the tail cone directly under the horizontal angles, then with a lengthen tie down bolt through this mass, it is secure. The amount of weight depends on what you need. 15 pounds worked for me on three different airplanes, 170B, and two 175 tail wheel.

To those of you who are happy that you can still land with power holding the nose wheel off, what are you going to do when you have to make an emergency landing in rough ground without power? Why fly an airplane that will not glide and flair to a slow landing and is not in center of gravity. With weight in the tail cone, it is just barely in forward CG, however, I had removed the back seat and carried around 200 lbs of camping gear in that area, using F. Atlee Dodge jump seats folded against the wall. The plane flew extremely well with that loading. All gear in the back was secured by a cargo net, including my Dahon folding bike.

The Sportsman STOL leading edge is the best of the group that I have found. I have thousands of hours flying with a Horton cuff, which is a good cuff as well, but Sportsman wasn’t out back in those days (70s). I had Micro vgs on my last 175 in addition to the Sportsman, but could not see any change except that it made me feel better about keeping flow over the ailerons and rudder.

Benefits of STOL are not accumulative with each new STC you install. You need to talk to Micro Aero about removing VGs.

Karl

Hey Karl, I did read your post on another forum but I didn't have my plane at the time. I was thinking of doing a conversion to the 172 at the time. I am going to PM you my number and if you have time could you give me a call. I would like to get some more details of how you built and fastened the weight. Thanks

Jerry

Micro's VG kit for the 172/175 lists at $1450, and is a pretty easy install. Their website sez "the installation takes one day for a mechanic who has never installed Micro VG's before". You could most likely install it yourself under your mechanic's supervision, with him doing the logbook entry & 337.
Stene Aviation's Sportsman STOL kit lists for about $2K, and installation sounds pretty time-consuming (riveting the new leading edge in place on both wings). Check their website for the installation instructions.
According to Stene's website, the Sportsman kit adds 15 pounds at 22", which wouldn't help your nose-heavy situation problem. The VG's pretty much weigh nothing.
I am more inclined toward the VG kit for my airplane, but others with the Sportsman cuff swear by it.

Eric

Karl,

I fly a Cessna 170 with AvCon conversion, and no lead in the tail. It's also a fairly light airplane. I have never considered putting lead in the tail, and would be VERY hesitant to do so, unless as you state--you can't land the thing power off. My airplane flares just fine, power off with no ballast in the tail. My airplane has no back seat (modified with a FAS sling seat, which I leave out) and it has a Selkirk aft baggage. I've flown probably eight or nine of these airplanes similarly equipped, and I've never flown one that I thought needed ballast weight in the tail. If that's the case, start looking at the equipment in the plane. Before I put ANY lead in the tail, I'd do the math on a Selkirk aft baggage, and see if ~25 pounds of survival gear at that station wouldn't fix the CG problem. I'd rather be carrying around 25 pounds of survival gear all the time than 15 pounds of useless lead in the tail.

I also have VG's and I WOULD NOT go there again. They did not change the slow speed handling of the plane all that much. They did mellow out the stall a LITTLE BIT. I could detect NO change in stall speed. They are a very real threat to your wrists while fueling. The thing I really HATE about them is that it is now difficult to impossible to feel the stall buffet on approach. As a result I wind up landing this airplane faster than I used to pre-VG's. I would NEVER put a set of VG's on one of these airplanes again.

Go with the Sportsman cuff--it's the REAL deal, and works a LOT better than the VG's. I should have installed the Sportsman rather than the VG's.

MTV

I found the W&B figures for my old 170, so just for grins I looked up the CG limits online. The old girl weighed in at 1,318# empty (zero fuel), with the CG at 38.65". Per the TCDS, the forward limit for the 170 loaded up to 1,733# is 36.3", max weight for utility category is 1900# with a forward limit of 38", & max for normal category is 2200# with a forward limit of 40.9". Aft limits at all weights are 40.3" for utility & 45.2" for normal. I know at the time I did some sample loading scenario's & it was possible to load it out of CG, but you had to work at it a little -- for most situations it was well within limits.
I'm curious as to the empty weight, empty CG, & CG limits for the C175 which was the original subject of this thread. I know some of the C172 180-horse conversions (like Air Plains & Penn Yann) can be fitted with fixed pitch props instead of constant speed-- you're giving up some performance there, but the trade-off is keeping the weight and cost down along with keeping the CG back in a more favorable location.

Eric

Eric, My 175B is 1416 lbs and the CG is 35.7. When it came out of the factory the CG was almost 3" back farther. At 1416 lbs my forward moment limit is 52" so I'm not even close to the envelope. At gross (2350 lbs) the forward limit is 97". I have found that a position change that seems obvious sometimes does actually very little because the weight goes up.

If I switched to a fixed prop that would make a world of difference but I hate to do that especially since I just had mine gone through. When I get get all the bugs out and I'm using the plane more, I am sure I will find some way to make it work. I had a good talk with Karl and he has tons of experience with 175's. Got a lot of good advise. I'll just keep plugging along till I get it right. I did get my second oil test back and the engine still looks good so I'm happy about that.

I stopped in Poulson MT to talk to Steen's about the Sportsman STOL the other day but I got there at 4:30 and they weren't there. I did notice the pilot's bathroom in Poulson has a shower if anyone cares. I talked to someone at Steen's last year and they said it is about $2000 for labor too. I asked if I could help and he told me that was fine and a lot of people do that . He said I just need to pay for anything I break. Most 175's have Horton's because the Sportsman wasn't approved on the 175 till last fall.