Takeoff Trim Setting - New to me 1970 M20F

[Shadrach]

19 minutes ago, cliffy said:

C model- fwd CG and trimmed on final at about 70 mph to the flare -  When taxiing out for T/O it takes about 1/2 turn nose down for T/O trim

to be acceptable for me.

Many Mooneys have their pitch system rigged incorrectly.

It takes jacks to level the airplane and correct tools to rig the pitch system correctly.

Especially rigging the spring bungees for the correct elevator up position when the stabilizer is set to the proper LE down angle.

Not many shops know how to rig the pitch system on a Mooney.  Maybe I'll make a utube on it sometime. 

Just as a word of warning- IF the pitch trim is set full nose down on takeoff the nose wheel will never leave the ground.

There's not enough elevator force at full up to lift the nose in that condition 

Several Mooneys have suffered this fate and run off the end of a runway at high speed. 

When ever I’m doing panel work I trim full nose down. It pulls the yokes right up against the panel and out of the way. I can imagine there is very little authority to raid the nose in that position.

[DCarlton]

There have been a few threads like this one, and I always wonder what I’m overlooking.  I usually take off with the trim set exactly where it was when I landed.  It seems to work fine.   No hard pulls, no wheelbarrowing.  Don’t know what I’m missing.  

[PT20J]

In cruise flight with the trim full down, I used a spring scale to measure 40 lb of force required to fly level in my M20J.

[DCarlton]

1 hour ago, PT20J said:

In cruise flight with the trim full down, I used a spring scale to measure 40 lb of force required to fly level in my M20J.

Why?  I try not to pull on anything that hard made in 1967.   

[Barneyw]

8 hours ago, Fly Boomer said:

And, conversely, if the pitch trim is set full nose up on takeoff (quite likely if not re-trimmed after landing) with full power and flaps up, the airplane may be uncontrollable.  At least one crash that I know of appears to have suffered this fate.

That's the reason why I spend some time on the runway resetting things on a touch and go.

I'd be interested in hearing from anyone who flies IFR regularly on how they set up for an instrument approach and why plus whether you have manual or electric gear.

[Z W]

1 hour ago, Barneyw said:

I'd be interested in hearing from anyone who flies IFR regularly on how they set up for an instrument approach and why plus whether you have manual or electric gear.

My practice, with electric gear:

Gear comes down when the glideslope is one dot high, set descent power, then half (takeoff) flaps.  I leave the flaps there and do not go full flaps unless I have broken out and a landing is assured.  The plane lands just fine with half flaps or even no flaps.  

This is to avoid the high workload that comes with a full-flap go-around.  If you have to go around from 75 KIAS with gear and full flaps, and you're trimmed properly for that (near full nose-up), the pitch-up action is very strong, so you have to do partial power, put in some nose-down trim, raise the flaps to half, let the plane stabilize a bit, raise the gear, more power, more nose down trim, raise the flaps.  It's a lot to do while bumping around in the clouds in IMC near the ground, trying to fly a missed approach and not run into a tree you can't see.  

Leaving the flaps at half removes pretty much all the workload.  You won't be trimmed as much nose-up.  You just go full power, establish positive rate of climb, gear up, flaps up.  I don't usually do touch-and-goes in the Mooney but my practice is the same for those.  They're easy with half flaps, lots of work with full.

It's good to practice full-flap go arounds because you may need to do one someday.  Obstacle on the runway, someone pulls out in front of you, etc.  But I don't want to do it in IMC.  And if you're flying an instrument approach, there is pretty much always plenty of runway so landing with half flaps is fine.

I also only use half flaps if the wind is gusting more than 5 knots or so.  Really reduces the plane's tendency to balloon up off the runway in a gust.

I have about 2 hours in a manual gear Mooney but don't think I'd do anything different. 

[luv737s]

I fly a lot of no flap approaches and find it smoother and easier to land.  It also prepares me for formation flying where no flap landings are the norm.  As far as instrument approaches, show me an instrument runway with less then 3000 ft available.  I don't find the flaps in my old C to be significant.  I know later models are different.  I also carry 50lbs of ballast (SOLO or 1 Pax) in the baggage compartment after did the W&B and find it makes a difference.

Know YOUR plane

 

[PT20J]

11 hours ago, DCarlton said:

Why?  I try not to pull on anything that hard made in 1967.   

I was curious to see if the airplane was controllable in that configuration. I wanted to measure the force with full up trim at various airspeeds, but it is more difficult to rig a measurement device for that condition. According to CAR3, the elevator controls have to be designed to take a force of at least 100 lbs.

[Barneyw]

5 hours ago, Z W said:

My practice, with electric gear:

Gear comes down when the glideslope is one dot high, set descent power, then half (takeoff) flaps.  I leave the flaps there and do not go full flaps unless I have broken out and a landing is assured.  The plane lands just fine with half flaps or even no flaps.  

This is to avoid the...

Thanks Z W that's a helpful and useful response.

Cheers

[ProtoFly]

Annual will happen in December, at which time there's a laundry list of things I'll be going over.  One of which is the rigging, to see that everything is 'in spec'.  Meanwhile, I'll fly what feels 'right' for the CG in the plane, and maybe add some ballast in the back to see how that affects things.

Thanks everyone for the various replies.  

[cliffy]

Move CG rearward and you gain speed!  :-)

[M20F-1968]

What you describe in your initial post descibes a clear problem.  On take-off the plane should be trimmed so that with a slight pull of the yoke on take-off roll,  flies itself off the runway with take-off flaps at about 65 kts.  It should be that easy.

The Trim indicator is simply a cable that reflects movement of the trim wheel.  Its position means nothing unless it is set at a place and in a manner that is interpretable by the pilot.  A small change in the trim wheel makes a big difference.  The take-off "Range" as marked in the trim indicator is not much help.  I have my trim indicator set so that the line between the grey take-off Range, and the black background color of the J model indicator is my take-off position.  It is that specific and that reliable.  

You may need to use the travel board to adjust per specifications.  But then, you will. need to find your ideal take-off trim and adjust the cable of the trim indicator to align with a specific spot on the indicator.

It is not much more complicated that this.

John Breda

[RoundTwo]

9 minutes ago, M20F-1968 said:

What you describe in your initial post descibes a clear problem.  On take-off the plane should be trimmed so that with a slight pull of the yoke on take-off roll,  flies itself off the runway with take-off flaps at about 65 kts.  It should be that easy.

The Trim indicator is simply a cable that reflects movement of the trim wheel.  Its position means nothing unless it is set at a place and in a manner that is interpretable by the pilot.  A small change in the trim wheel makes a big difference.  The take-off "Range" as marked in the trim indicator is not much help.  I have my trim indicator set so that the line between the grey take-off Range, and the black background color of the J model indicator is my take-off position.  It is that specific and that reliable.  

You may need to use the travel board to adjust per specifications.  But then, you will. need to find your ideal take-off trim and adjust the cable of the trim indicator to align with a specific spot on the indicator.

It is not much more complicated that this.

John Breda

The Mooney service manual has a specific method for adjusting the indicator. It is definitely not “find your favorite setting and adjust the indicator to match”. Too much chance of damaging the indicator if it’s set outside design travel limits.

[M20F-1968]

1 minute ago, RoundTwo said:

The Mooney service manual has a specific method for adjusting the indicator. It is definitely not “find your favorite setting and adjust the indicator to match”. Too much chance of damaging the indicator if it’s set outside design travel limits.

To be hones, I have not touched that adjustment in about 9 years.  It was likely first set my my mechanic.  I did however reset that cable housing so that the take-off position is set to a specific line in the indicator, and not the grey take-off "Range".  In essence and in practice I limited the already set take-off "range" to a more limited line line which I have used repeatedly for 9 years.  It seems with that mechanical cable, even with that limitation, there is some variability in the setting and I wanted to keep the variability to a minimum.

John Breda

[super-fly]

My CFI’s M20G and my M20C both like to take off (and land) with about 3/4 nose-up trim, not even close to the marking on the indicator.  Maybe they’re out of rig; we just tried different settings until we found what felt “right”, then use that every time.

[TCW3]

On 8/20/2024 at 7:08 PM, AndreiC said:

I was told that many people set their trim indicator so its *bottom* edge (it is a white square in my plane, probably in yours as well) lines up with the *top* of the trim position marked on the window.

Spot on. I have a 1970 M20F and it is very nose heavy. I always put the bottom edge of the indicator at the top of the take off position marker. This helps get the weight off the nose and reduce the amount of muscle needed for initial lift-off. 

You'll notice when landing that you're maxed out on elevator trim in a lot of cases. Be very careful during touch-n-go landings. The elevator trim (at least on mine) is slow when adjusting. 

[AndreiC]

34 minutes ago, TCW3 said:

You'll notice when landing that you're maxed out on elevator trim in a lot of cases. Be very careful during touch-n-go landings.

Strange. After I land, most times I do not need to adjust the trim at all; the trim indicator is split about half-way by the top line of the marking on the side. (My transition training drilled the poem "flaps/flaps/mixture/switches/trim" into my head, and I do this after each landing; i.e., flaps up, cowl flaps open, mixture rich or leaned for ground ops, fuel pump and landing light off, trim adjust to take-off setting. But most times I do not need to adjust the trim at all.)

I don't do touch and goes. If I am at my base field, where the runway is short (2900 ft) I always taxi back. If I am practicing at KMSN (10000 ft runway) I stop on the runway, do the poem above, and then go again. Too many touch and go incidents end up in gear ups.

[Ragsf15e]

9 hours ago, AndreiC said:

Strange. After I land, most times I do not need to adjust the trim at all; the trim indicator is split about half-way by the top line of the marking on the side. (My transition training drilled the poem "flaps/flaps/mixture/switches/trim" into my head, and I do this after each landing; i.e., flaps up, cowl flaps open, mixture rich or leaned for ground ops, fuel pump and landing light off, trim adjust to take-off setting. But most times I do not need to adjust the trim at all.)

I don't do touch and goes. If I am at my base field, where the runway is short (2900 ft) I always taxi back. If I am practicing at KMSN (10000 ft runway) I stop on the runway, do the poem above, and then go again. Too many touch and go incidents end up in gear ups.

Mine is typically at the takeoff setting when trimmed for landing as well.

[Pinecone]

Do you guys fly with back seats filled or a lot in the baggage compartment?  ie Aft CG?

In my 252, I am at full nose up trim and holding backpressure on landing with 2 people up front and maybe 20 pounds in the back

[Ragsf15e]

3 hours ago, Pinecone said:

Do you guys fly with back seats filled or a lot in the baggage compartment?  ie Aft CG?

In my 252, I am at full nose up trim and holding backpressure on landing with 2 people up front and maybe 20 pounds in the back

Well I think your 252 is a totally different beast than the older E/F/Js I think we were talking about.  Hanging a bigger engine out front could change where that trim setting is.  Fwiw, my F varies a little bit with me in front (fwd cg) vs loaded up with aft cg, but not more than the thickness of my trim indicator.  Trimmed for takeoff is trimmed for landing.  One other thing that probably affects it… I almost always use full flaps on landing.  Maybe it would be different on a nf or to flap landing?

[Hank]

5 minutes ago, Ragsf15e said:

Trimmed for takeoff is trimmed for landing.  One other thing that probably affects it… I almost always use full flaps on landing.  Maybe it would be different on a nf or to flap landing?

That's how my C is, but I usually land with Takeoff Flaps, close enough that I rarely need to adjust for the next takeoff. 

It's partly flap setting, partly CG and partly empty CG. The more forward the CG, the less trim should be needed to descend for landing, right? 

I found out that Fs land much better with Full Flaps, so it's also a body length thing. (I have no G time to compare O vs IO for weight differences.)

[MikeOH]

14 minutes ago, Ragsf15e said:

Well I think your 252 is a totally different beast than the older E/F/Js I think we were talking about.  Hanging a bigger engine out front could change where that trim setting is.  Fwiw, my F varies a little bit with me in front (fwd cg) vs loaded up with aft cg, but not more than the thickness of my trim indicator.  Trimmed for takeoff is trimmed for landing.  One other thing that probably affects it… I almost always use full flaps on landing.  Maybe it would be different on a nf or to flap landing?

Interesting, as I land my '70F with full flaps, as well, but with quite a bit of nose up trim (just me and not much in the back, so forward CG).  Definitely NOT the same as TO trim.  I'm trimmed for hands-off on short final at 75 mph, full flaps.

[Ragsf15e]

1 minute ago, MikeOH said:

Interesting, as I land my '70F with full flaps, as well, but with quite a bit of nose up trim (just me and not much in the back, so forward CG).  Definitely NOT the same as TO trim.  I'm trimmed for hands-off on short final at 75 mph, full flaps.

That little trim indicator is pretty much infinitely adjustable and you can probably set it to show “takeoff trim” no matter where your trim is set.  Possibly ours is just set slightly differently.  Or maybe we have different empty cg?  Or possibly it’s the extra 5mph i carry? I’m normally 80mph target on final?  

[MikeOH]

1 hour ago, Ragsf15e said:

That little trim indicator is pretty much infinitely adjustable and you can probably set it to show “takeoff trim” no matter where your trim is set.  Possibly ours is just set slightly differently.  Or maybe we have different empty cg?  Or possibly it’s the extra 5mph i carry? I’m normally 80mph target on final?  

I'll have to play with approach speed a bit to see if that's the difference, but I doubt it.  Very true the CG difference between our planes would explain it.

As far as indicator position, that would only be true if the trim did NOT need to be adjusted again for TO.  But mine does, by quite a few turns of the trim wheel after I Iand in order to get back to my take-off setting.

[Ragsf15e]

3 minutes ago, MikeOH said:

I'll have to play with approach speed a bit to see if that's the difference, but I doubt it.  Very true the CG difference between our planes would explain it.

As far as indicator position, that would only be true if the trim did NOT need to be adjusted again for TO.  But mine does, by quite a few turns of the trim wheel after I Iand in order to get back to my take-off setting.

Well sure, but suppose your to setting and mine are not the same but our landing settings are… maybe our planes feel a little different on takeoff and we’re just use to it?  Try leaving your setting from landing and taking off with it.  I suspect it’ll feel different but fine.