185 trim issue

[Tom3holer]

Hi,
I have a 73 185 that has had an issue with the trim as long as I have had it over 7 years.
Unless I load the rear extended baggage compartment with my 15l-20lb tool bag nose down trim is VERY difficult above about 160mph. Even then its still difficult.
My question is how could an aircraft get certified that you cannot trim up to vmo. The tail with the tool kit in the back is tail heavy to the point, as I touch down in a wheel or semi 3 point landing the tail so quickly drops enough to send me airborne again unless I am really ready for it.. The other day i placed the tool kit just behind the rear seat. I was on a grass strip, where keep the plane, and it was soooo nice. I was ready for the tail to drop but it didn't and was just a nice landing like my 58 180 used to do.

I would think that with more weight in the tail, further aft cg, forward trim should be more difficult not less.

The plane has a sportsman leading edge and vortex gens and holds 100 gal of fuel but fuel loading does not seem to make a big difference.
It cruses at 160mph true at 7500 LOP at 12gph.
One thought is perhaps the wing incidence is not correct.

Can anyone shed some light on this? It would be greatly appreciated.
Tom

 

[BC12D-4-85]

Maybe it's me but the term "difficult" is confusing. Try to describe what that means to you? Are you saying aft or nose up trim is insufficient at certain CG's and airspeed? Have you kept track of the loaded CG vs issue? The wings, controls, and trim are all adjustable as I recall. It's in the Cessna Service Manual.

Gary

 

[Tom3holer]

Gary,
Sorry if I was confusing. I ment as the speed picks up and approaches 160 mph it is very difficult to keep trimming nose down to compensate for the increasing speed. Very difficult is, the point where I feel it will break something i I try any further nose down. The cables have been checked for the trim and they are at spec and a bit more and the clicker is in good order. We have removed the rudder and went all over the jackscrews and it works very easily on the ground. Nose up trim is no issue.
As I mentioned the fuel loading does not make much of a difference.

 

[BC12D-4-85]

https://backcountrypilot.org/commun...a-a185e-forward-trim-bind-above-130-kts-25874 (?) Here's some advice. I flew a couple an didn't have the issue, but the planes were pretty young and inexperienced. The one with a Sportsman did make more lift IMO, so maybe more nose down trim might be needed.

Gary

 

[aflyer]

By difficult to trim, you are referring to how much force it takes to turn the trim wheel? That is normal Skywagon, and actually is why the later models came with clickers. I can understand how moving the center of lift forward with the Sportsman STOL would make that trait worse.
I do not understand why adding weight in the rear would help.

 

[wagondriver]

"VERY difficult" may be a problem but it Skywagons certainly require more effort to trim at higher speed than at slower speeds. This is the nature of the beast. I am concerned when you suggest it is VERY difficult. Mine, and most others that I have flown, require more force at higher speeds to the point where you may feel that you roll in several "clicks" of forward trim and it may even revert a click or two each time. The key for me and most operators is to get ahead of the trim before the speed builds...as I near leveling off, I roll in nose down trim to the likely point of level trim and then only do a quick adjustment, if required, once cruise speed is hit.

I agree with you that too much force doesn't feel good on the equipment.

The difference between VERY and normal difficult should be confirmed with another 'Wagon pilot for a cross-reference and if it is agreed that it is abnormally tough to trim I would suggest in order: a) trim cable tensions (sounds like you have done this), b) verify the eccentrics in the jack screws are set correctly and not causing any binding at any position in the stabilizer. A good excuse to check your hocky-stick AD is to remove the horizontal and then do a reset on the whole system.

 

[mvivion]

Interesting….of the ten or fifteen 185s I’ve flown, none ever got close to those speeds, but they were always wearing tires, skis or floats, so....

You don't state in your question specifically WHERE the CG is, with and without the tool bag. Bear in mind that these were designed as working airplanes, so, when empty, they are by nature, far forward CG airplanes. Any 185 I ever flew was generally equipped with at least thirty or so pounds of survival gear, generally located as far aft as practical. Even then, a quick check of CG would typically put the airplane very near the forward limit with just the pilot aboard. Anything you put in those airplanes then moves the CG aft.

Be careful to use the proper datum when calculating CG....some use a distance forward of the leading edge, some use the LE.

As to the landing experience you described, that sounds like spring gear at work more than a CG issue. Touch tail low-the main gear gives, then rebounds.... There are waaaay too many variables there to make an assessment on CG from a few landings, frankly. I seriously doubt CG was at play there, but maybe. I generally avoid three point landings in these planes in any case, except in certain circumstances.

It sounds to me like you are operating close to the forward CG limit, which is what I'd expect with just one person aboard (my assumption, since you didn't offer that info) and fuel. Fuel in the wings of most of these planes will move the CG aft as you burn off fuel, but not a huge amount.

Trim forces can be high in a 185. As someone noted above, that's why they installed the ratcheting trim control. Here's an experiment every 185 driver should experience.....preferably at altitude the first time: Try an approach to land with an empty plane, trim for hands off approach, full flaps, power near idle. Now, execute a full power go around. That can be a deeply moving religious experience close to the ground. Hence I always carry some nose down trim on approach, and hold some back pressure.

These are “muscular“ airplanes. But, again, I’ve never been that fast in a 185….too scary for me.

MTV

 

[hotrod180]

....Be careful to use the proper datum when calculating CG....some use a distance forward of the leading edge, some use the LE. ...

FWIW Cessna uses the firewall as the datum for the 180,
pretty sure the same is also true for the 185.

It sounds to me like you are operating close to the forward CG limit, which is what I'd expect with just one person aboard (my assumption, since you didn't offer that info) and fuel. Fuel in the wings of most of these planes will move the CG aft as you burn off fuel, but not a huge amount.

FWIW the fuel in my C180 (48") is aft of the empty CG (34.9").
As fuel burns off, the CG moves forward, not aft.
With just 2 people aboard, burning off 200# of fuel moves the CG fwd by just over an inch.
I assume the same is true of the 185.

 

[mvivion]

Datum is wherever the mechanic who prepares the W & B certificate puts it. Some of our planes the datum was set way far forward to eliminate negative numbers.

But, the point here is that the answer to his question regarding trim forces is impossible to determine without knowing the CG at the time and loading that his stated trim condition occurred.

 

[DENNY]

Separate the two issues. The higher the speed the more resistance you will feel when trimming even my 180 does that. As far as tail motion MTV is correct lots of factors to consider. Flaps/Rpm/CG/Airspeed. If you are just letting the tail fly on its own it will naturally drop and if you are landing 10 MPH over your stall speed (which makes for the nice smooth/spot wheel landing everyone likes) Ya you will fly again if the tail comes down. Look up the MAF technique and when the mains touch pin them with the yoke. Put the tail down when you want it to come down. Nothing wrong with getting a good 185 driver to fly with you and work on the landings.
DENNY

 

[BC12D-4-85]

The thread I linked in #4 notes some bushings that can require inspection, plus aligning the tail parts so they fit w/o interference. Also mentions static loading the stab with water filled buckets to simulate heavy inflight down loads, then running the trim to see if it gets stiff.

Like Post #6 my trimming was almost done by the time I leveled off in cruise. Three quick palm rolls forward or back of the trim wheel (or something close to that) with the control yoke slightly pressured to help, then released. Add a click or three to let her fly hands off as fuel is burned.

Gary

 

[Tom3holer]

Thank you all for all the input, it is greatly appreciated.

One thing, I should have made the "160mph True" in all caps, I can see where that could be easily missed. The point I was trying to make is that it flys close to book TAS although I am never near GW. Generally myself and occasionally one passenger, usually full fuel; 100 gal.

I am quite sure it's not the gear legs. The other day when I moved the tool kit forward, as mentioned in my original post, I made several landings at a nearby grass strip. I approached at the same speed 65 ish mph in a semi 3 pointer approaching the ground at the same rate as I try to do and it just landed beautifully with no quick forward yoke movement to keep the tail from dropping. I do trim for slightly nose down on all landings. On paved runways and always when windy I do wheel landings with a bit more speed.
I had always read that you need weight in the tail; a case of oil was mentioned many times.
My 58 180 did get stiffer when trimming forward but nothing like the 185.
Perhaps I should have my mech check the wing angle of incidence.

Again thanks for all the thoughts and advice.

Tom

 

[OLDCROWE]

Even after a complete trim overhaul, my 180's trim is pretty firm at those speeds but moves easily at slower. When I'm cruising at or near Flank Speed, I usually give it a little help by pushing slightly on the yoke as I trim nose down in cruise (typically 145TAS at 8500') as fuel burns off and such.

 

[BC12D-4-85]

There's much noted via Internet searching re wing rigging (for example). The SM has the procedure. Cuffs can change aerodynamics near the LE, and may move the center of pressure relative to the factory's design.

I'd have a look at the position of the current wing eccentrics. Raising the trailing edge should slightly reduce lift, may increase speed, and may reduce trim forces (a guess). The 2nd C-185 I flew had a Sportsman and wings rigged for max lift with the TE full down. But the gear (wheel skis and floats) prevented speed so lift with load was primary.

In the end the traditional design of control harmony (1-2x-4x; aileron-elevator-rudder) via resistance to movement may not apply to Skywagons. They fly like workout day at the gym in my experience.

Gary

 

[stoldriver]

My 180 trim got very difficult to move. I could unload the airplane a little and it would be easier. I pulled the stab off to find out what was going on. Found a number of issues from a previous owner but the big one was one of the jack screw had unscrewed and was disconnected so I was down to one. Not good. My suggestions as a result is to pull it apart if it changes. I'd also say if it is very hard to trim, pull it apart and check. It just isn't that difficult to pull tail feathers and it's worth it to take a look and grease the screws. Mine was very easy to trim after i finished. We also have the AD to prompt us so every time you pull the tail, it's worthwhile to do that too.

Wayne

 

[DENNY]

You don't need sudden movements of the yoke to pin the tail. Do the MAF technique and just keep increasing braking or yoke pressure to keep the tail where you want it. Landing at 65 mph you are going to have a longer run out until you slow enough that it does not fly again when you put the tail down. Even longer if you don't raise the flaps on touchdown. Slow down and fly the tail all the way to the tie down the 20 lb tool bag location is not the issue. Wheel landings do not have to be done any faster than a 3 point landing.
DENNY

 

[dryfarmer]

I know a gal that had the same problem you described, she replaced the jack screw problem went away

 

[hotrod180]

You don't need sudden movements of the yoke to pin the tail. Do the MAF technique and just keep increasing braking or yoke pressure to keep the tail where you want it. Landing at 65 mph you are going to have a longer run out until you slow enough that it does not fly again when you put the tail down. Even longer if you don't raise the flaps on touchdown. Slow down and fly the tail all the way to the tie down the 20 lb tool bag location is not the issue. Wheel landings do not have to be done any faster than a 3 point landing.
DENNY

Here's a synopsis of the MAF wheel landing technique, as per a Bill white article about it from about 20 years ago.

 

[hotrod180]

Perhaps I should have my mech check the wing angle of incidence.

Let's say your mechanic decides the wing AOI is wrong-- then what?
IMHO the wing AOI adjustments (eccentric bushings) are designed to correct a heavy wing.
If you think the stab trim is heavier / bindier (is that a word?) than it should be,
even after reading where everyone finds the trim forces heavy at full cruise speed,
I'd suggest checking the trim mechanism-- including stab attach points, jackscrews, cables, & trim wheel.

 

[a.crane]

Let's say your mechanic decides the wing AOI is wrong-- then what?
IMHO the wing AOI adjustments (eccentric bushings) are designed to correct a heavy wing.
If you think the stab trim is heavier / bindier (is that a word?) than it should be,
even after reading where everyone finds the trim forces heavy at full cruise speed,
I'd suggest checking the trim mechanism-- including stab attach points, jackscrews, cables, & trim wheel.

I agree with this, eccentrics are to adjust for heavy wing. Sounds like you need to pull the horizontal and check the jackscrews out. Something is causing the resistance somewhere. I’ve had jackscrews with a very slight bend in them cause binding. That was on a 185 on a part 135 cert. Don’t ask me how they got bent. Could also see the above scenario happening where one comes unscrewed due to improper assembly that would not be good. McFarlane sells a pretty nice kit with new boots and everything. Check out the trim wheel too

 

[Tom3holer]

We have removed the rudder and stab and went all over the jackscrews and it works very easily on the ground as mentioned before.
It is smooth and easy from one end to the other.
Denny, I have read a lot of your posts and have a great deal of respect for your knowledge. I found moving the tool bag made a BIG difference in landing as I reported.
Tomorrow is supposed to be a beautiful day so I will be doing some practice on the MAF wheel landing procedure.
Will report back.

 

[hotrod180]

Datum is wherever the mechanic who prepares the W & B certificate puts it. Some of our planes the datum was set way far forward to eliminate negative numbers.

If someone is preparing a weight & balance for a skywagon using anything other than the firewall as a datum,
they need to read the TCDS.

 

[flywhatever]

Interesting….of the ten or fifteen 185s I’ve flown, none ever got close to those speeds, but they were always wearing tires, skis or floats, so....

You don't state in your question specifically WHERE the CG is, with and without the tool bag. Bear in mind that these were designed as working airplanes, so, when empty, they are by nature, far forward CG airplanes. Any 185 I ever flew was generally equipped with at least thirty or so pounds of survival gear, generally located as far aft as practical. Even then, a quick check of CG would typically put the airplane very near the forward limit with just the pilot aboard. Anything you put in those airplanes then moves the CG aft.

Be careful to use the proper datum when calculating CG....some use a distance forward of the leading edge, some use the LE.

As to the landing experience you described, that sounds like spring gear at work more than a CG issue. Touch tail low-the main gear gives, then rebounds.... There are waaaay too many variables there to make an assessment on CG from a few landings, frankly. I seriously doubt CG was at play there, but maybe. I generally avoid three point landings in these planes in any case, except in certain circumstances.

It sounds to me like you are operating close to the forward CG limit, which is what I'd expect with just one person aboard (my assumption, since you didn't offer that info) and fuel. Fuel in the wings of most of these planes will move the CG aft as you burn off fuel, but not a huge amount.

Trim forces can be high in a 185. As someone noted above, that's why they installed the ratcheting trim control. Here's an experiment every 185 driver should experience.....preferably at altitude the first time: Try an approach to land with an empty plane, trim for hands off approach, full flaps, power near idle. Now, execute a full power go around. That can be a deeply moving religious experience close to the ground. Hence I always carry some nose down trim on approach, and hold some back pressure.

These are “muscular“ airplanes. But, again, I’ve never been that fast in a 185….too scary for me.

MTV

Spot on reply Mike! Exactly as I would have stated.