Landing Problems

dacker · Post by **dacker** » Tue Oct 04, 2005 3:36 am

Today I took 84A out for the second flight for the engine break-in. Flew great, purred like a kitten. I flew for an uneventful 1.6 and came back in for a landing on 16, winds 09 at 5. Came in with a little power, left wing down right rudder, ballooned just a little, corrected and three pointed it, and pulled the throttle to ground idle. Then all hell broke loose! It started a hard veer to the left even though I had almost full right rudder ( I didn't seem to have any appreciable drift when I touched down). Just when I thought I was going to ground loop ( I was pulling the yoke into my chest and had full right rudder and brake) it straightened out just a little and then I thought I was just going to take out a taxi light

. I over corrected that to find myself in the beginnings of a right ground loop. Full brakes and left rudder straightened me out, still on the runway, in one piece.
Granted this was only my second landing in my 170 in almost a year but this was ridiculous

! I ran into a problem like this a year or two ago when my tailwheel chains got caught on the bracket that is on the leaf spring ( I think it is labeled the tailwheel steering chain guard). The bolt is on the bottom and it was pulling the tailwheel so that when I landed it would make me veer before breaking over. I think it should be on the top of the leaf spring.
I guess the point of this is to ask for input. In the 175 hours I have flown this 170 I have always thought it squirrelly compared to the few other tailwheel airplanes that I have flown. This is the only one that I have flown that I don't feel like I have absolute positive control on wheel landings (hard to keep straight) and I have probably done 1000 landings in it over the past three years ( I practice T&Gs a lot).
Are there other things I should be looking at? Toe-in/Toe-out?
I am going to fast taxi up and down the runway a few times tomorrow to see if anything is out of the ordinary. I really don't want to spend a lot of time on the ground since I only have a couple of hours on the engine and I am still trying to break it in. Any ideas or experiences would be appreciated.
David

russfarris · Post by **russfarris** » Tue Oct 04, 2005 4:35 am

David - CHECK YOUR GEAR ALIGNMENT!!! Do a search on "landing gear alignment" and check out my experience with this, about a year ago. Having the gear correctly set-up made a huge difference in the way my airplane handled. The procedure for doing this is in the discussion. Russ Farris

CraigH · Post by **CraigH** » Tue Oct 04, 2005 4:40 am

David, with only 6+ hours in a 170 I find it one of the easiest handling taildraggers I've ever landed. Most of my tailwheel time is Tcraft, 140 and Citabria but I've got smaller amouts of time in 10 or so others. I would also suspect some sort of gear alignment problem.

JJH55 · Post by **JJH55** » Tue Oct 04, 2005 6:29 am

Dacker,
I had a similar experience too. After repacking the wheel bearings and replacing the wheel I didn't get the axle nut completely seated against the wheel bearing. On the first landing, it got pretty exciting with a resulting hard right turn just after touchdown. Effectively. any side load on that wheel was causing a misalignment with the disk in the caliper and effectively actuating the brake. When I removed the cotter pin I only needed to turn the nut a half turn to bottom out. You might want to check and see that there's no movement of the wheel on the axle.
Good luck.

dacker · Post by **dacker** » Tue Oct 04, 2005 1:33 pm

Thanks for the comments. After I posted my message I thought about the bearings. As part of the year long annual I repacked the bearings. I was thinking possiby that I had them too tight, but too loose would be more likely. I appreciate not being handed "landing lessons", not that I don't feel like I can always improve. I feel like the amount of time that I have flown this little airplane and the effort that I have put forth in landings should at least allow me to stay on the runway in a small crosswind.
I replaced my tires also, didn't notice any unusual wear patterns other than the inboard portion of the tires wearing more than the outboard. I attribute that to most of my flying being solo and light, and not depressing the mains enough to put the rubber on the ground evenly. (Does that make sense?) I am going to Brenham now to jack up my airplane to check tire rotation and talk to the mechanic on the field to help me check the toe in/out. The Cessna service manual has a lot devoted to this.
Thanks,
David

russfarris · Post by **russfarris** » Tue Oct 04, 2005 5:17 pm

David-according to Cessna very little tire wear is due to camber (top of the tire tilted inboard or outboard.) The reason I checked my gear alignment was heavy wearing of the inboard half of each tire. Cause: excessive toe-in.) Once I corrected this to the correct zero toe-in and zero camber my tire wear problems went away and my airplane turned into a ground handling pussycat! I forgot how to post a link to it, but please read my experience with this searching under "landing gear alignment" I'll bet you have too much toe-in. It's easy to check! Russ Farris

dacker · Post by **dacker** » Tue Oct 04, 2005 8:57 pm

Russ, I checked my toe-in today in the three point attitude and it was close to neutral on the left and between 1/4" and just less than 1/2" on the right. The mechanic said that it would have to be checked in the level attitude. I haven't checked the service manual to back this up yet.
I also made a tail wheel chain guard for the shackle on the leaf spring, I didn't have one (I checked a 170A on the field to see what his looked like). I guess that is why it is called a guard, to keep the chain from hanging up

. I jacked up the left wheel to check for bearing drag or anything else that might have been causing problems and didn't find anything.
I did a couple of aborted take-offs but nothing really stood out other than it just seems sloppy. The winds for RWY 16 were 08 at 8 so I didn't have the guts to try any T&Gs. It is hard putting ego aside for crosswinds that I normally would find just good exercise not something that could potentially wreck my airplane. At this point I don't know if it is just a combination of my stagnant skills or the airplane or both.
David

dacker · Post by **dacker** » Tue Oct 04, 2005 10:40 pm

Russ, I just reread the posts on your experiences and Bela's. It sounds like we all flew the same airplane. The problem I am having is getting a mechanic to take me seriously. All of the mechanics around here are so darned busy with high dollar bonanzas and the like that they are afraid to spend any quality time with a real airplane. I think the first thing they think is pilot technique and that a little toe in or out couldn't possibly be a problem

. Since I have spent a rather large fortune on trying to make this airplane "right", I am not ready to settle for squirrely, I want a pussycat too!
When I measured the toe in and camber it was empty and light, only about twelve gallons, so I think that I need to do it again at the average operating weight.
I believe that I am going to do this myself with a little input from the mechanic that has done most of the work (he got another job but is OK with signing off my work since I have worked him for a couple of months).
In one of your old posts you said that your airplane was "darty", that pretty much describes it.
David

mrpibb · Post by **mrpibb** » Thu Oct 06, 2005 7:16 pm

I had the same problem, my caster/camber toe in/out was every which way but right!!! after some new shims and about 3 hours of flipping and swapping shims, my 170 tracks like it's on rails.
I did mine at the annual so being the interior was out I had loaded up the cabin with sand bags and blocks to get the 2000#

check out "landing gear alignment" on the forum.

rudymantel · Post by **rudymantel** » Thu Oct 06, 2005 7:23 pm

David, listen to Russ- he's 100% right on this subject. I was going to tell you the same thing.
When checking the alignment the book says to place the weheels on greased plates. This is messy - several layers of newspaper work quite well to allow the wheels to find their natural toe-in or out. There should be NO toe in. A tiny bit of toe-out is ok. The camber should be slightly positive-ie, the top part of the tire tilted a bit outboard. I believe this mainly affects tire wear. And the tire pressures should be correct. Most folks use 35 psi.
Of course also check your tail wheel- the chain springs should have equal tension. And the vertical swivel axis should be close to vertical. This can be adjusted by (cold) bending the main leaf spring.

When I bought my airplane it handled horribly. The previous owner thought all 170's were like that. It took me a while to adjust out all the misalignments and the airplane is now a delight.

I feel sure the problem is with your airplane, not with you.
Rudy

rudymantel · Post by **rudymantel** » Thu Oct 06, 2005 7:29 pm

PS- and of course buy at least one of the three shims that Cessna makes.
There might be a bit of trial and error to get the alignment just right.

You're right in doing this work yourself. It's not difficult. Modern mechanics have no clue about our conventional landing gear.
Rudy

Post by **GAHorn** » Thu Oct 06, 2005 8:33 pm

The specification for main tire pressure is 24 psi, and for Scott 3200 tailwheel is 34 psi. The "zero" toe-in should be measured at 2,000 lbs and in the three-point attitude.

rudymantel · Post by **rudymantel** » Thu Oct 06, 2005 10:56 pm

I meant buy at least the three shims sold by Cessna-
Rudy

dacker · Post by **dacker** » Fri Oct 07, 2005 1:03 am

Thanks guys! The newspapers sounds worth trying, I didn't seem to have much luck with the garbage bags. From initial measurements it seems that I definitely have over a quarter inch toe-in on the left main, on the right maybe none, and oh yeah, no shim either. Camber looks to be fairly close to neutral while light, which means it is probably negative at heavier weights or when being depressed on landing. I was planning on installing steel axles pretty soon and will wait until I do that to try and align everything. I also think that I need to measure everything while on some kind of frictionless pad to get more accurate measurements. To get to 2000 lbs I will need full tanks and quiet a lot of weight. My "calculated" gross is 1300, I think 1400 is probably closer. From the violence of my bad landing I really believe I had something pulling me over there, I strongly suspect the chain hanging up. I also found the left rudder spring had come loose, though I don't think this caused the swerve.
Yesterday I ordered a new universal joint and new bushings for the yoke. I am going to work very hard at taking out all of the slop in the ailerons. I adjusted the tailwheel chain yesterday by adding back a link, it was a little too tight. I figure everything is cumulative and it is making my bird harder to control than need be. My mission after rebuilding darn near everything else is to fine tune it now and turn it into that pussycat we were talking about!
David

rudymantel · Post by **rudymantel** » Fri Oct 07, 2005 2:13 am

George, are you sure of that 24 psi ? That seems awfully low. I use 40 psi as it makes the airplane easier to push out of my T-hangar. And 50 in the tailwheel.
Rudy