Takeoff Trim Setting - New to me 1970 M20F

[MikeOH]

5 minutes ago, Ragsf15e said:

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.  

Well, I'm one of those 'evil' pilots that does touch 'n goes, so I've already run that experiment!  No way I'm taking off with the landing trim setting...I'd end up in a stall! I have to crank the trim back nose down before applying full power to take off.

[Ragsf15e]

4 minutes ago, MikeOH said:

Well, I'm one of those 'evil' pilots that does touch 'n goes, so I've already run that experiment!  No way I'm taking off with the landing trim setting...I'd end up in a stall! I have to crank the trim back nose down before applying full power to take off.

Weird how they are different.  I do t&gs on occasion too and it doesn’t seem bad to me.  I still think it could be perception… if you are trimmed for ~80mph on final, you should still be trimmed for 80mph on takeoff.  I doubt you’d stall, but I agree youd have to trim forward as you accelerate above 80.

[MikeOH]

Just now, Ragsf15e said:

Weird how they are different.  I do t&gs on occasion too and it doesn’t seem bad to me.  I still think it could be perception… if you are trimmed for ~80mph on final, you should still be trimmed for 80mph on takeoff.  I doubt you’d stall, but I agree youd have to trim forward as you accelerate above 80.

Yeah, I'm really curious how much it's perception vs. an actual difference.  Take off is back to TO flaps and I do get a pretty significant pitch down when I go from TO flaps to Full flaps when I'm on final. That's when I start to roll in more up-trim, and then a little more as I slow from 90 mph to 75 mph.  I suspect that flap change is responsible for most of trim change needed when I take off again.

[Hank]

1 hour ago, MikeOH said:

Yeah, I'm really curious how much it's perception vs. an actual difference.  Take off is back to TO flaps and I do get a pretty significant pitch down when I go from TO flaps to Full flaps when I'm on final. That's when I start to roll in more up-trim, and then a little more as I slow from 90 mph to 75 mph.  I suspect that flap change is responsible for most of trim change needed when I take off again.

Man, you mid-body folks are so complicated! I fly downwind at 90 mph, Takeoff Flaps, drop gear and back off throttle at the numbers; turn base still at 90 mph; turn final and roll wings level at 85 mph, slowing to 75 mph over the mystical / mythical fence, minus 5 mph for every 309 lbni am below gross for that landing. Throttle to idle, maintain speed, raise the nose to slow and touch down. If the wind is really low or calm, I'll often have to add additional flaps to maintain desired descent / glideslope / VASI lights if present.

Yes, all of our planes move nose down with the addition of flaps; adding more flaps  moves the nose down more. But you should get a lot of that back when you round out and flare, right? Or do you just maintain the descent rate, lift the nose with trim and yoke, and plonk down onto the runway? 

[MikeOH]

11 minutes ago, Hank said:

Man, you mid-body folks are so complicated! I fly downwind at 90 mph, Takeoff Flaps, drop gear and back off throttle at the numbers; turn base still at 90 mph; turn final and roll wings level at 85 mph, slowing to 75 mph over the mystical / mythical fence, minus 5 mph for every 309 lbni am below gross for that landing. Throttle to idle, maintain speed, raise the nose to slow and touch down. If the wind is really low or calm, I'll often have to add additional flaps to maintain desired descent / glideslope / VASI lights if present.

Yes, all of our planes move nose down with the addition of flaps; adding more flaps  moves the nose down more. But you should get a lot of that back when you round out and flare, right? Or do you just maintain the descent rate, lift the nose with trim and yoke, and plonk down onto the runway? 

Sounds like you just want to pick a fight.

You win; buh bye

[cliffy]

Here's a question for those with near or full up trim on landing-

Have you ever figured your CG position with the load you are landing at just to see where it sits?

Maybe you might run the actual numbers and report back I'm interested in knowing what others see for CG with the front seats only filled 

If I put 2 big guys  in the front of my D/C with full fuel (still under MGW) I show my CG  out front of the envelope. 

This could/would account for your need for lots of up trim.

With just me and my wife up front we are aft (but not by much) of the FWD CG line. 

If I have bags in the back and the CG goes further aft I have less up trim on landing and my speed can increase up to 5 kts in cruise (less trim drag). 

[Pinecone]

Running the numbers, with full fuel and 2 - 235 pounders in the front seats, 20 pounds baggage and 5 in the hat shelf, I am at Max Gross and 44.5 inches on the CG.

CG moves forward with fuel burn.

M20K 252/Encore

[Shadrach]

32 minutes ago, Pinecone said:

Running the numbers, with full fuel and 2 - 235 pounders in the front seats, 20 pounds baggage and 5 in the hat shelf, I am at Max Gross and 44.5 inches on the CG.

CG moves forward with fuel burn.

M20K 252/Encore

Yup.  Same here. The only time I hit the aft trim stop is when landing with minimum fuel and two up front…and then only on short final…and then it’s only likely because I fly slower approaches than most. Loaded as described I’m crossing the fence at <60KIAS.

[MikeOH]

@cliffy

I took a look at my solo W&B; 40 gal. fuel, 25 lb. baggage, 10 lb. hat shelf, and me...45.6" CG, 45.0" when my wife is aboard.  Forward limit is 41.0"

Doesn't seem to explain my need for nose-up trim on landing.  Maybe it's my slow approach speed? 75 mph on short final, 70 mph over the fence?

[PT20J]

3 minutes ago, MikeOH said:

@cliffy

I took a look at my solo W&B; 40 gal. fuel, 25 lb. baggage, 10 lb. hat shelf, and me...45.6" CG, 45.0" when my wife is aboard.  Forward limit is 41.0"

Doesn't seem to explain my need for nose-up trim on landing.  Maybe it's my slow approach speed? 75 mph on short final, 70 mph over the fence?

I think that's it. If I'm light and fly the final at a speed where I won't float much (60-65 KIAS in my M20J) I will be about one turn of the trim wheel nose up compared to the takeoff setting. If I come over the fence faster, I can land at the takeoff setting. 

[cliffy]

13 hours ago, MikeOH said:

@cliffy

I took a look at my solo W&B; 40 gal. fuel, 25 lb. baggage, 10 lb. hat shelf, and me...45.6" CG, 45.0" when my wife is aboard.  Forward limit is 41.0"

Doesn't seem to explain my need for nose-up trim on landing.  Maybe it's my slow approach speed? 75 mph on short final, 70 mph over the fence?

I might agree with PT20J   "Approach speed"  I too use about 65 to 70 MPH over the fence but Ill have to relook at my settings next flight. 

Just as a guess only-  are you sure all your elevator settings are correct ? I've seen them screwed up on several airplanes 

BTW- I lost a good friend many many years ago at KPOC in a Comanche at night in the rain. Used to fly there a lot from KSMO  taking the boss in his Navajo, 

[MikeOH]

7 hours ago, cliffy said:

I might agree with PT20J   "Approach speed"  I too use about 65 to 70 MPH over the fence but Ill have to relook at my settings next flight. 

Just as a guess only-  are you sure all your elevator settings are correct ? I've seen them screwed up on several airplanes 

BTW- I lost a good friend many many years ago at KPOC in a Comanche at night in the rain. Used to fly there a lot from KSMO  taking the boss in his Navajo, 

@cliffy

Thanks.  Never really thought about this issue until this thread; many saying that take-off and landing trim are close has a bit concerned.

Are the elevator settings something that should be found during annual?  Pragmatically, if something is 'off', then after 7 annuals I guess no one has been checking!

Yeah, KPOC seems to have had more than its share of fatals; there were two just a few months apart about two years back.  Both stall/spins IIRC.  Not a lot of options on departure, hills, tress, and a lake...I figure I'm going swimming as close the shore line as possible if the fan quits.

[cliffy]

Unless the shop has a trim board for checking the elevator and stab angles and willing to jack the airplane to level fore and aft  it won't get done during any annual.  

Airplane has to be leveled

Stabilizer set to a specific Leading Edge down setting using the trim board 

AND then the elevator up angle is checked and set by adjusting the spring bungees on the 

inboard ends of the elevators (adjusting the fwd ends of the bungee control rod and NOT trying to adjust by the spring retainer nuts at the aft edge of the bungee unit!!)

This is all spelled out in the Mooney TCDS (Type Certificate Data Sheet) a portion of which I have clipped below. You will notice that the elevator up angles and the P/N of the bungees are different via serial number. You being a 1970 model I believe you will fall in the after 680001 number field.

Be sure to look at the cautionary note on the extension springs at the bottom if you decide to have someone adjust these settings.

You will also notice that the later Fs have a higher elevator bungee angle than the earlier ones. Something to think about if you have pitch trim issues. 

 

Control Surface Movements  Stabilizer (L.E.)................Up.......½° to 1'.............Down ........5¼° to 5¾°

Elevator Trim Assist Unit (for Aircraft with Serial Nos. to 680001): With stabilizer set at 3½' negative setting to the thrust line, adjust trim assist unit 740128 for elevator up angle of 5' =/-1'at the zero spring travel position.

VII. Model M20F (cont’d) Elevator Trim Assist Unit (for Aircraft with Serial Nos. 680001 and up): With stabilizer set at 3' negative setting to the thrust line, adjust trim assist bungees 740188 for elevator position of 19' +/-1' at the zero spring travel position of the bungees. (This rigging to be obtained before installation of the 740171 extension springs).

Leveling means Edge of skin splice over aft fuselage radio access panel. Spirit level is used to level.

 

[MikeOH]

@cliffy

Thanks very much!

[Ragsf15e]

1 hour ago, MikeOH said:

@cliffy

Thanks very much!

As an aside, I got an annual done several years ago at one of the shops you use for annuals.  Good shop. Expensive.  They found an issue with one of my trim rods requiring replacement (thank goodness Mooney was quick-ish).  They replaced the rod and finished my annual.  When i picked it up, I did a very thorough inspection and noticed that the paint below the tail pivot seemed different but I really wasn’t sure.  Trim was set to the middle (to) position.  I was disturbed by the fact that the tail and the trim indicator might be different and they told me, yeah it might be out of whack after we had the trim all apart. Let us know how it feels and we can adjust the indicator.  Well, I thought it through and took off with the trim centered.  Airplane was trimmed very nose up so it was exciting but i was mostly ready for it.  After landing I looked and the paint was lined up as I thought it had use to look but my trim was way off center.  I had them set that to TO trim.  So maybe it’s not an exact science…

[cliffy]

A final word of caution (as I've noted before) NEVER try to takeoff with full nose down trim!

There is no way that the airplane will rotate! You WILL go straight off the end of runway if you don't get stopped before then end.

This has happened to several Mooneys over the years.