tail tiedown weight

[Sabremech]

Hi Bob, I don't think there's going to be a revision to the Service Instructions, I would proceed with caution going outside of the published instructions, but at a minimum check the tie down hardware. 

Thanks,

David

[jamesm]

Seems to me the newest service instruction/bulletin method  is least safe option as other have stated compared to  tail weight and/prop stand which have been used for years.

how much heavier would be be if Mooney were to retrofit a  later model engine mount  to for the earlier and smaller Lycoming engine  models where there is tubular extension  jack point on the the engine mount.  then all is needed is a bottle jack. Seems like much safer and could be a one and done solution  rather than keep  producing instruction/bulletins less safe that prior one.

James

[jetdriven]

Where's the data it's safe to pull the front of the airplane up by the engine lifting eye. How about the stress on those rubber engine mounts, the tubular engine mount itself, and those 1/4" bolts that hold the engine mount to the firewall.  You know mine were bent when I changed them at time I overhauled the engine. 

[Bob_Belville]

We're pretty close to the "beating-a-dead horse" stage of this thread but I want to make one further point based upon my report yesterday that when I step on the entry step while the plane is on jacks and the cowling is removed the tail goes down. There is very little play in the tail hold down clevis pin so it can only move 1/4" or so. The tail attachment stabilizes the plane whether the tail want to go up or down with CG changes. 

When a tail stabilizer is replaced with a chain fall on the engine lift "ring" what happens when the CG moves behind the jack points? Removing weight from the nose end, e.g. nose wheel comes off for maintenance, cowl removed, maybe starter or alternator, etc. and weight is added behind jack points - someone steps up on the step, someone is in the plane working  in rear seat area, etc, I hope a jack stand of some kind is used to keep the tail from going to the floor which well might cause the wing jacks to do nasty stuff.

As I observed a couple of years ago, the evidence is pretty clear, if only circumstantial, that Mooney's SI was precipitated by Lycoming's warning re prop jacks. It was not issued out of any particular concern about the use of tail hold down weight.  

[jamesm]

 My point  was to have jack point off the engine mount like later model Mooney's have make the most sense to me. IMHO having the airplane   suspended from engine hoist by a  chain (swing moment)  is the least safe option,  climbing up and down on the airplane while on jacks   makes me   extremely paranoid.  If I remember correctly there isn't much holding the bulkhead   that has the tail tie down eye bolt nut plate  which attaches to  the rest of the airplane  I think there was 1   rivet each  side  1/8  diameter. It would be nice to come up with method that doesn't cost and arm and leg and doesn't become superseded every few years.  

[N201MKTurbo]

It could probably be done, but it would take a reworked motor mount, would require an STC to install it and about 10 hours of labor. All in all it would cost at least a few AMUs. Not worth it in my estimation.

[RLCarter]

For stability my jacks under the wings are pinned (can't bleed down), the nose is raised with chain hoist from an A-frame, as a third precaution there is a screw type jack stand under the tail. Very solid when lifted and I sleep good at night when I leave the hangar and it's not setting on the gear. Everyone is happy, aircraft was raised per service bulletin, no stress on the prop, hub or crankshaft, and I'm happy that it does not teeter when getting in or out of the cabin.

[Guest]

21 hours ago, jetdriven said:

Where's the data it's safe to pull the front of the airplane up by the engine lifting eye. How about the stress on those rubber engine mounts, the tubular engine mount itself, and those 1/4" bolts that hold the engine mount to the firewall.  You know mine were bent when I changed them at time I overhauled the engine. 

I asked the Lycoming Tech guys at Oshkosh about lifting the plane with the engine lift ring.  They advised against it.

Clarence

[Hank]

So in a nutshell when jacking up our Mooneys for maintenance:

1. Do not lift the nose by the prop.
2. Do not lift the nose with the (incorrectly named?) engine lift ring.
3. Do not hold down the tail.

So we are relegated to magically balancing the plane on the two tiny jack points while climbing in and operating the gear, then exiting. Pity on those souls with manual gear, or rigging the gear; those who need to rig manual gear are just S.O.L.

I will continue to ignore the recent flurries of contraindicated advice and use the tried-and-true tail tie down weight.

[HRM]

13 hours ago, Bob_Belville said:

As I observed a couple of years ago, the evidence is pretty clear, if only circumstantial, that Mooney's SI was precipitated by Lycoming's warning re prop jacks. It was not issued out of any particular concern about the use of tail hold down weight.  

This is what I have always heard in this regard.

[Bob_Belville]

11 hours ago, RLCarter said:

For stability my jacks under the wings are pinned (can't bleed down), the nose is raised with chain hoist from an A-frame, as a third precaution there is a screw type jack stand under the tail. Very solid when lifted and I sleep good at night when I leave the hangar and it's not setting on the gear. Everyone is happy, aircraft was raised per service bulletin, no stress on the prop, hub or crankshaft, and I'm happy that it does not teeter when getting in or out of the cabin.

I don't get the jack high enough to pin them. One of my old jacks does bleed down a little over several days so I do not leave the gear up when I leave the plane overnight even though the jack would bottom out in a safe position.

[RLCarter]

Bob, I didn't like going that high on the jacks so I built my own jacks, a-frame and tail stand, 2" after the donuts relax is good enough to retract the gear

[bonal]

I knew that when lifting mine they use an engine hoist and this thread got me thinking about the attachment as it turns out they use a large strap that loops through both ends of the engine mount frame. 

[PTK]

Mooney engineers say don't weigh down the tail to lift the nose. So I don't do it! Who am I to argue?

McCauley engineers say don't push or pull the plane by the prop. So I don't do it! Who am I to argue?

Aeroshell chemical engineers say don't contaminate our oils with aftermarket additives. So I don't do it! Who am I to argue?

I don't consider it productive to argue with pros who are more knowledgeable than I am! But that's just me.

BTW, the "...it has been done like this for a long time..." argument is irrelevant and invalid imo.

 

[Hank]

Just did my annual, should have taken a picture but I was busy. Got ready to jack the plane, realized we didn't have a tail weight. So we stacked 3 cases of oil, a detergent bottle of used oil, a gallon of water, a box of tools and a couple dozen old, bound approach plates on the horizontal stab. The plane balanced great! Actually had to lift the tail a little bit after raising the gear, but it was really easy to hold.

[Hank]

1 minute ago, PTK said:

Mooney engineers say don't weigh down the tail to lift the nose. So I don't do it! Who am I to argue?

McCauley engineers say don't push or pull the plane by the prop. So I don't do it! Who am I to argue?

I don't waste my time arguing with the pros who are more knowledgeable than I am! But that's just me.

The "...it has been done like this for a long time..." argument is irrelevant and invalid.

 

Lycoming engineers say to not lift by the engine.

McCauley says don't lift by the prop.

Mooney says don't hold the tail down.

When you jack a Mooney, the jack points are not at the CG. How do you hold the plane level? We slid my large plastic trashcan under the tail while re packing wheel bearings, with all the stuff above stacked on it.

[Bob_Belville]

10 minutes ago, PTK said:

Mooney engineers say don't weigh down the tail to lift the nose. So I don't do it! Who am I to argue?

McCauley engineers say don't push or pull the plane by the prop. So I don't do it! Who am I to argue?

I don't consider it productive to argue with pros who are more knowledgeable than I am! But that's just me.

BTW, the "...it has been done like this for a long time..." argument is irrelevant and invalid imo.

 

Uh Huh. There is at least a remote possibility that the fellows pulling the strings of your "engineers" are actually lawyers whose pronouncements are based on CYA, not strength of materials and structures.

But hey, whatever suits you and your A&P.

[DonMuncy]

I'm beginning to think we not supposed to work on Mooneys. Can't tie down the tail. Can't lift by the engine. Can't lift by the prop.  I'm assuming we can't put a jack under the engine either.

Has anyone blessed wrapping a strap around the engine mounts.

[bonal]

If you look close in my photo you will see we are lifting by the motor mount frame not the engine. I think this is a good approach to the problem 

[Bob_Belville]

Just now, bonal said:

If you look close in my photo you will see we are lifting by the motor mount frame not the engine. I think this is a good approach to the problem 

I noticed. But I'm not sure what the engineering authority is for that. That's Don's question. Are the mounts designed for load in that plane? 

[Ron McBride]

Bonal     Your plane looks great. 

 

I have used in the past, the engine hoist hooked to the engine mounts, and weight under the tail.   The engine hoist concerns me, about the tail being able to go down when climbing on the step,  Tail stand stops that.

Ron

[HRM]

3 hours ago, PTK said:

Mooney engineers say don't weigh down the tail to lift the nose. So I don't do it! Who am I to argue?

McCauley engineers say don't push or pull the plane by the prop. So I don't do it! Who am I to argue?

Aeroshell chemical engineers say don't contaminate our oils with aftermarket additives. So I don't do it! Who am I to argue?

Having made a living and a career out of 'engineering engineers,' don't believe everything they tell you because often they have an attorney standing behind them with a stick in hand. 

Trust but verify is something of an engineering mantra...

Engineering is a team activity, this is why our accrediting agency (ABET) puts so much emphasis on it in engineering education. You don't need to be an engineer to have a valid engineering opinion. At the end of the day, physics and math will have the final say on the matter and they are Mom Nature's kids and obey her.

[HRM]

One other thing...nothing is foolproof to a sufficiently talented fool.

[Hank]

7 minutes ago, HRM said:

One other thing...nothing is foolproof to a sufficiently talented fool.

As a Manufacturing Engineer, writing product specifications and work procedures, I used to keep that taped to my computer monitor at work.

truer words have rarely been written . . .

[bonal]

55 minutes ago, Bob_Belville said:

I noticed. But I'm not sure what the engineering authority is for that. That's Don's question. Are the mounts designed for load in that plane? 

I don't know the answer you would have to ask my shop but since they have jacked up more Moonies than perhaps any one on the planet earth I trust their approach. Seems regardless one method vs another someone has an opinion that it's not the right way. Anyway as we raise the airframe the hoist isn't lifting much compared to the jack points and the tail stand is only an inch from the surface when we start to lift. The nose lifts right as the tail stand makes contact. I guess there is no perfect solution.