Tail stand design

[N201MKTurbo]

1 hour ago, MikeOH said:

I can't say I've read every post, but I haven't seen the actual weight required to hold the tail down.  I've seen barrels of concrete at 600 pounds discussed...but, does it really take that much??

Back in the day (late '70s) we used to move C150s, C172s, and even occasional C182 (not me, I was too light!) around by just pushing down on the tail to lift the nose (Yeah, in your best Apocalypse Now voice, "Oh, The HORROR, THE HORROR").

Yeah, a Mooney ain't a Cezzna (Thankfully), and you want a little 'extra', but what weight is really required?

Assuming the jack points are approximately at the fuel arm. The furthest forward CG is 4 inches ahead of the jack point. So 4 X 2740 = 10960.

The approximate distance from the jack points to the tail hook is 136" so 10960/136 = 80.5 Lbs

So you will need more than 80 Lbs to hold the tail down. Less than most people think. 

 

That was the furthest forward CG at max gross. It is worse at furthest forward CG at 2300 Lbs, that is at 7 inches ahead of the fuel for a moment of 16100

For that situation you would need 118 Lbs.

[MikeOH]

@N201MKTurbo

Thanks

Roughly 100 lbs. sure sounds more like it

[N201MKTurbo]

1 minute ago, M20Doc said:

That weight might work until you crawl up on the wing to raise the gear.

That is the most forward CG allowed for the plane which would be two people in the front seats. I think that would cover someone climbing into the plane.

Brice bought a 300 Lb fish scale we used to rig the gear on his 310. I could borrow it and actually measure the force. I think in most cases you would be nowhere near those forces.

If I have the tail tied down with a chain, I have to be careful stepping on the step, because the plane will tip up a bit if I put too much inertia onto the step.

[Z W]

I once had a flat nose tire after landing.  Luckily went flat after I taxied off the runway, but was stuck on the ramp.

A&P came out with a dolly and a couple of jacks.  We jacked the wings up.  I then pushed down on the tail to lift the nose wheel while he slid the dolly under it.  Not ideal, but it wasn't exactly an ideal situation at the time.  Tube had a hole in it and the tire wasn't holding pressure to move anywhere.

It took most of my body weight (220 lbs or so) to lift the nose long enough to slide the dolly in. I wasn't hanging on the tail, but it also wasn't all that easy to just push it down like a 172 is.  No damage to anything, it was fine, not that I'd want to do that on a regular basis.

When we later built a tail stand, we used a large plastic tub and about 350lbs of concrete sitting on a furniture dolly.  Wouldn't want any less weight back there while climbing around on the wings and raising and lowering the gear.  I'll try to remember to snap some photos next time I'm at the hangar.  It turned out very well.  It's rock solid and seems to be about the right amount of weight.

[Pinecone]

Going with the minimum weight for tail hold down is probably not the way to go.  

[N201MKTurbo]

32 minutes ago, Pinecone said:

Going with the minimum weight for tail hold down is probably not the way to go.  

Oh, come on, it would be fun! You could grab the spinner and tilt the whole plane up and down with very little effort.

[A64Pilot]

On 7/12/2023 at 3:13 PM, MikeOH said:

Back in the day (late '70s) we used to move C150s, C172s, and even occasional C182 (not me, I was too light!) around by just pushing down on the tail to lift the nose (Yeah, in your best Apocalypse Now voice, "Oh, The HORROR, THE HORROR")

Yes we all did, and we were breaking the internal structure of the horizontal doing so, usually the nose ribs. but also the spar. I don’t anymore.
https://www.faasafety.gov/gslac/alc/libview_normal.aspx?id=158943

So as I consider the internal structure of the horizontal as important, yes the horror, the thought of the horizontal failing in turbulence gives me the willies.

If you have to lift the nose with your body for whatever reason, lay across the empennage (remove your belt first)

Edited July 15, 2023 by A64Pilot

[MikeOH]

58 minutes ago, A64Pilot said:

Yes we all did, and we were breaking the internal structure of the horizontal doing so, usually the nose ribs. but also the spar. I don’t anymore.
https://www.faasafety.gov/gslac/alc/libview_normal.aspx?id=158943

So as I consider the internal structure of the horizontal as important, yes the horror, the thought of the horizontal failing in turbulence gives me the willies.

If you have to lift the nose with your body for whatever reason, lay across the empennage (remove your belt first)

Yes, I’m sure the accident rate caused by tails falling off has dropped significantly since we’ve ceased doing that

[PT20J]

31 minutes ago, MikeOH said:

Yes, I’m sure the accident rate caused by tails falling off has dropped significantly since we’ve ceased doing that

The problem was with C-172 and C-175. After numerous SDRs for cracking tail components, Cessna issued a SB. The recommendation is not to push on the stabilizer anywhere to maneuver the airplane. If you absolutely have to move it by the tail, push on the tailcone bulkhead rivet line.

[MikeOH]

4 hours ago, PT20J said:

The problem was with C-172 and C-175. After numerous SDRs for cracking tail components, Cessna issued a SB. The recommendation is not to push on the stabilizer anywhere to maneuver the airplane. If you absolutely have to move it by the tail, push on the tailcone bulkhead rivet line.

Not saying it was ever a good idea.

But I'd be curious if the data shows SDRs dropped in a statistically significant way after the SB came out.  The engineer (and cynic) in me is curious, especially as it was a model specific issue, if the SDRs were on high time airframes?  Another data point might be if the SDRs showed whether the cracks were predominately on only one side of the tail.  While not definitive I, and everyone I observed, always pushed on the pilot's side of the tail; an asymmetry in the SDR data would support the tails being actually damaged by the practice.

[A64Pilot]

On 7/12/2023 at 6:40 PM, M20Doc said:

That weight might work until you crawl up on the wing to raise the gear.

I stick my arm through the storm window to raise and lower the gear. I just don’t like climbing around on an airplane on jacks.

I used to do a C-210, on that airplane I stood on a ladder and reached in to raise and lower the gear, a 210 on jacks is really wobbly.

But I agree, I see nothing but disadvantages to having just barely enough weight to hold the tail down, before I decided to lift the nose I was going to install an anchor into the floor.

Edited July 15, 2023 by A64Pilot

[EricJ]

1 hour ago, MikeOH said:

Not saying it was ever a good idea.

But I'd be curious if the data shows SDRs dropped in a statistically significant way after the SB came out.  The engineer (and cynic) in me is curious, especially as it was a model specific issue, if the SDRs were on high time airframes?  Another data point might be if the SDRs showed whether the cracks were predominately on only one side of the tail.  While not definitive I, and everyone I observed, always pushed on the pilot's side of the tail; an asymmetry in the SDR data would support the tails being actually damaged by the practice.

I have similar curiosity.   It was still common practice to sit on the tail and maneuver airplanes around on the ground, especially in tight quarters, when I was a lineboy, so we did it all the time on both C150s and C172s.   C150s are especially easy to wrangle around this way and saves a ton of time compared to wrestling with a tow bar.   You also have a better view of the tail and wingtips for avoiding obstacles.    So I've always mourned the demise of that particular technique and wondered whether it was really an issue or not.

[Fly Boomer]

1 minute ago, M20Doc said:

The cracks I’ve seen in 172 horizontal stab’s radiate from the lightening hole in the main spar below the fin. 

Ever seen tail damage on a Mooney from pushing down on the horizontal?

[A64Pilot]

1 hour ago, MikeOH said:

Not saying it was ever a good idea.

But I'd be curious if the data shows SDRs dropped in a statistically significant way after the SB came out.  The engineer (and cynic) in me is curious, especially as it was a model specific issue, if the SDRs were on high time airframes?  Another data point might be if the SDRs showed whether the cracks were predominately on only one side of the tail.  While not definitive I, and everyone I observed, always pushed on the pilot's side of the tail; an asymmetry in the SDR data would support the tails being actually damaged by the practice.

I believe pushing down on the tail was a Cessna approved technique and Cessna ate some crow from the damage caused later.

https://www.tennesseeaircraft.net/2016/11/13/cessna-approved-bad-training/

 

[RoundTwo]

On 7/10/2023 at 6:30 PM, Kelpro999 said:

I use lead bars above and below with a telescoping square tube stand pinned at whatever height I need.

With more lead on top of the stab too.

[Kelpro999]

9 hours ago, RoundTwo said:

With more lead on top of the stab too.

Yes, I weight the top side enough so I can easily lift the prop and feel the tail eye to pin clearance. With the base over weighted it can’t lift (nose down) by accident. The telescoping tail stand / weight allows lifting at any attitude for whatever I’m doing.

[GLJA]

So glad I had the forethought to put a retractable hook in the floor of my hangar. It’s reinforced 6” down with 12” rebar horizontally. Now, I just use a cable turnbuckle with A threaded clamp on each end. Completely adjustable and stable. 

[N201MKTurbo]

8 minutes ago, GLJA said:

So glad I had the forethought to put a retractable hook in the floor of my hangar. It’s reinforced 6” down with 12” rebar horizontally. Now, I just use a cable turnbuckle with A threaded clamp on each end. Completely adjustable and stable. 

I prefer chains. They aren’t infinitely adjustable, but they are incrementally adjustable. And I feel they are more reliable.

[MBDiagMan]

Several years back, I simply set two lag nuts from Home Depot into the hangar floor.  I then used segments of chain, bolting one end into the lag nuts and the other to the tail eye.  When not in use I simply thread a bolt in to keep trash out of the hole. Works great and cost very little. 

[LOCOLJ]

I probable overdid this, but wanted something portable that I could remove weight easily and store.  Works with fitness weights or paver blocks from HD.  Started with a 55g drum dolly and welded a plate to some square tubing with a telescoping mate.  This was mostly scrap I had on hand. 

[Fly Boomer]

12 minutes ago, LOCOLJ said:

I probable overdid this, but wanted something portable that I could remove weight easily and store.  Works with fitness weights or paver blocks from HD.  Started with a 55g drum dolly and welded a plate to some square tubing with a telescoping mate.  This was mostly scrap I had on hand. 

 

That’s a nice looking stand.

[Jpravi8tor]

Here is my Hobo freight stand in action

[Jpravi8tor]

someone please tell me the reason the pics don't upload correctly, do I need to pre-rotate them before upload?

[47U]

On 7/27/2023 at 7:13 AM, Jpravi8tor said:

someone please tell me the reason the pics don't upload correctly, do I need to pre-rotate them before upload?

I’m not sure why pics load rotated.  After posting, save the picture to your photo album, rotate it from the edit menu, save and repost it.  You can then delete the image from the post that’s not oriented correctly.  That method seems to work on my iPad…