Aircraft jacking poll

[Shadrach]

6 minutes ago, A64Pilot said:

I can’t lift my J, I just tried, but can easily a 172 with an O-360 on the nose

Well, there is a pretty large delta in weight from plane to plane. Mine weighs 1681lbs.  I’m betting Skips plane is >200lbs heavier than mine.  As I recall, the only way I could lift mine was to face backwards and reach over the just ahead of the tail. 

[PT20J]

5 minutes ago, Shadrach said:

So skip is saying 639lbs on his nose wheel. I have not done it in a long time, but I am pretty sure I was able to lift the nose of my F and I was well under 200 then.  Heavier than lifting the nose of a 172 as I recall but able to lift all the same.

The distance from the jack points to the tail tie down is approximately twice the distance from the jack points to the nose wheel. So, if the weight on the nose wheel is 639 lbs, the weight at the tail to create a balancing moment would be about 320 lbs. You’d want more to offer stability. I guessed that the tail weight I use is about 400 lbs. of concrete plus the frame and wheels, so maybe 430 lb. total. Someone in the other thread mentioned using a tub filled with water. It would take 48 gallons of water to get 400 lbs.

[A64Pilot]

Only relevance to tail weight if you chose to go that route is to have enough, any extra is just additional insurence.

But over 300 lbs is not an insignificant amount of force on the tail tie down, but then over 600 lbs isn’t insignificant on the nose either.

I used to lift the entire aircraft by the engine mount on my Maule when I’d change from 7” tires to 29” tires, I used a forklift at the plant. I’d guess 2,000 lbs?

[Guest]

1 hour ago, PT20J said:

According to the Lycoming Operator’s Manual, the IO-360-A1B6D weighs 330 lbs. When we reweighed my M20J, the weight on the nose wheel was 639 lbs.

I was going to say about 1/3 of the empty weight sounds reasonable.  So the engine lift ring is being asked to support almost double the engine weight.

[carusoam]

+ 1 for straps around the engine mount, properly…  this way the stresses aren’t applied to the engine…

Google says the IO360 weighs 325LBs…

Hartzell prop weighs 71Lbs…  (updated post to reflect Ross’ input below!)

in case anyone is thinking in more minute detail….   

Best regards,

-a-

 

[FlyingDude]

I think in M20E models, nose gear is at -1" from datum point and main gears are at 66".  CG is at 46".  That's 20" between the CG and mains.  CG doesn't move much by loading fuel.  The overall length of the plane is 278".  I don't know at what station the tie-down hook is at.  However, the length of the plane is 8.5cm on paper whereas that point is 4cm from the main gear.  Rough estimate shows that it's at station 278*(4/8.5)=130" from the mains. Assuming that the plane is jacked up with only 10gl fuel, weight: 1660lbs.  Therefore, 1660*20/130 = 255lbs down force is needed to pivot the plane on the mains and balance nose level.  I don't know if jack points are aligned with the wheels, though.

 

[Shadrach]

42 minutes ago, carusoam said:

+ 1 for straps around the engine mount, properly…  this way the stresses aren’t applied to the engine…

Google says the IO360 weighs 325LBs…

Hartzell prop weighs 150Lbs…

in case anyone is thinking in more minute detail….   

Best regards,

-a-

 

 

I must’ve been hit with a strong dose of gamma radiation in my youth, because I have hung my prop several times with no physical assistance. Your prop number seem heavy by about 100lbs.

[Shadrach]

6 minutes ago, FlyingDude said:

I think in M20E models, nose gear is at -1" from datum point and main gears are at 66".  CG is at 46".  That's 20" between the CG and mains.  CG doesn't move much by loading fuel.  The overall length of the plane is 278".  I don't know at what station the tie-down hook is at.  However, the length of the plane is 8.5cm on paper whereas that point is 4cm from the main gear.  Rough estimate shows that it's at station 278*(4/8.5)-1=130" from the mains. Assuming that the plane is jacked up with only 10gl fuel, weight: 1660lbs.  Therefore, 1660*20/130 = 255lbs down force is needed to pivot the plane on the mains and balance nose level.  I don't know if jack points are aligned with the wheels, though.

 

You don’t notice a difference in approach trim based on fuel load? I feel like when light on fuel it takes more nose up trim but I could have my wires crossed.

[carusoam]

2 minutes ago, Shadrach said:

 

I must’ve been hit with a strong dose of gamma radiation in my youth, because I have hung my prop several times with no physical assistance. Your prop number seem heavy by about 100lbs.

Prop and hub….

Ross, You check your skin color… be on the look out for some Hulkish green….  

I’ll check the Hartzell website to get a better number than what Mrs. Google offered…

Best regards,

-a-

[FlyingDude]

8 minutes ago, Shadrach said:

You don’t notice a difference in approach trim based on fuel load? I feel like when light on fuel it takes more nose up trim but I could have my wires crossed.

Sure I did. I didn't say that loading fuel doesn't add weight.  I said that the CG doesn't move much, because the fuel cell station is aligned with the empty CG of the plane.

At full fuel, the CG moves to 47".  So, the math becomes: 19" between CG and mains.  still 130" between mains and tiedown point.

2575 * 19/130 = 376lbs down force needed.

EDIT:

This much downforce IF the plane were pivoting around the mains.  I think the lift point is not aligned with the mains.  I think the lift point is a little further front than the mains.  So, obviously, the down CG arm is shorter and down tail arm is longer, therefore in flight, the tail is not pushing down that much.  

[carusoam]

Ross,

Prop weights below….  54Lbs… to 71Lbs….

Thanks!

-a-
 

Applicable Models:
M20J (200 hp)

Specifications:
74 inch diameter 3-bladed aluminum hub propeller
2400 hour / 6 year TBO
71 pounds (propeller and spinner)
Diameter reduction allowable to 73 inches
Placard -“Avoid cont. ops. below 15″ btwn. 1950 and 2350 rpm”

Replaces:
Hartzell HC-C2YK-1BF/F7666A-3Q – 73 in. dia. 2-bladed prop
Q-tip, no diameter reduction allowable
2000 hour / 5 year TBO
59 pounds (propeller & spinner)

McCauley C212 or C214 – 74 inch diameter 2-bladed prop
Diameter reduction allowable to 73 inches
2000 hour / 6 year TBO
54.3 pounds (propeller and spinner)
Placard – “Avoid cont. ops. below 15″ btwn 1500 and 1950 rpm.”

[Shadrach]

8 minutes ago, carusoam said:

Prop and hub….

Ross, You check your skin color… be on the look out for some Hulkish green….  

I’ll check the Hartzell website to get a better number than what Mrs. Google offered…

Best regards,

-a-

Just checked TCDS. My prop and hub is 53.75lbs. Spinner is 3.6lbs. David Banner not needed!

[BDPetersen]

Somewhat related story. Helping a buddy with his Bonanza on jacks and the gear retracted, he sent me up to the cockpit for some reason. As I reached the door, the bolt attaching the tail weight finished slipping out and I went for a brief, memorable ride as it pitched forward, nose to the floor. My friend had been under the nose but some how got out of the way. Quite a sight with the V tail up in the hangar trusses, the jack on one wing punched through the lower wing skin.

Never was sure if the bolt hadn’t been fitted with a nut or if it had worked loose. A fair amount of bouncing takes place scrambling on and off the wing. I never look at an aircraft on jacks the same. Makes me nervous. 
 

Always make sure your weight is secure.

[Hank]

When I used a traveling IA, he brought jacks but nothing for the tail. So I stacked almost 2 cases of oil in the horizontal stabilizer (one on each side of the vertical stab), with a stack of approach plates and a roll of wrenches. Then it was a simple task to push down in the tail with one hand for the retraction tests.

I was even able to squat under the tail while holding the tail and take video of the gear going up and down while the IA reached in the storm window. And I'm not The Hulk . . . .

[Jpravi8tor]

I have jacked my aircraft once and wanted to learn what others have been doing, I used a 5 gallon bucket of concrete but needed 2 additional lektro tug lead acid batteries to make it work

[Shadrach]

1 hour ago, FlyingDude said:

Sure I did. I didn't say that loading fuel doesn't add weight.  I said that the CG doesn't move much, because the fuel cell station is aligned with the empty CG of the plane.

At full fuel, the CG moves to 47".  So, the math becomes: 19" between CG and mains.  still 130" between mains and tiedown point.

2575 * 19/130 = 376lbs down force needed.

EDIT:

This much downforce IF the plane were pivoting around the mains.  I think the lift point is not aligned with the mains.  I think the lift point is a little further front than the mains.  So, obviously, the down CG arm is shorter and down tail arm is longer, therefore in flight, the tail is not pushing down that much.  

Center of pressure depends on flap position. It moves aft as the flaps are deployed.

[Guest]

3 hours ago, Shadrach said:

 

I must’ve been hit with a strong dose of gamma radiation in my youth, because I have hung my prop several times with no physical assistance. Your prop number seem heavy by about 100lbs.

Two blade propeller installation alone isn’t too bad, three blades are more of a challenge and four blades require a hoist, but as I’ve aged I let the younger guys lift them now.

[RLCarter]

I made jacks for the mains that can be pinned at 1” intervals, I lift the nose with an A-frame and chain hoist (can’t bleed down) with nylon strap around the engine mount, once up in the air I use an adjustable tail stand I made. With 4 points it’s rock solid and I sleep well knowing it can be left jacked up and there is nothing to bleed down

[FlyingDude]

6 minutes ago, RLCarter said:

can be pinned at 1” intervals

Could you share some pictures? Thanks

[RLCarter]

2 minutes ago, FlyingDude said:

Could you share some pictures? Thanks

[DGates]

I use an engine hoist attached to the engine mount.  I've used web straps but have also just made a loop out of some rope to connect the engine mount to the jack hook.  Can't use the engine hoist hook directly on the engine mount tubing, no room for the hook.  I'm a bit leery of using the tail tie down ring, as one is putting a 1/4-20 thread in tension and hoping that it holds.  Going ker-splat on the nose would be painfully expensive to repair, likely several months of down time so I'm trying to minimize risk as much as possible.  I'm always nervous when i have the plane on jacks, too... I do it as required, but I jack it, do the necessary, then get her back onto the tires and *certainly* don't leave it jacked up overnight....

[PT20J]

4 hours ago, DGates said:

I use an engine hoist attached to the engine mount.  I've used web straps but have also just made a loop out of some rope to connect the engine mount to the jack hook.  Can't use the engine hoist hook directly on the engine mount tubing, no room for the hook.  I'm a bit leery of using the tail tie down ring, as one is putting a 1/4-20 thread in tension and hoping that it holds.  Going ker-splat on the nose would be painfully expensive to repair, likely several months of down time so I'm trying to minimize risk as much as possible.  I'm always nervous when i have the plane on jacks, too... I do it as required, but I jack it, do the necessary, then get her back onto the tires and *certainly* don't leave it jacked up overnight....

Actually, there are two AN4 bolts which are 1/4-28. AN bolts have a tensile strength of 125,000 psi., so a 1/4 inch bolt in tension should be good for about 4000 lb before it fails based on a minimum cross sectional area of about .0364" at the bottom of the threads.

[DonMuncy]

42 minutes ago, PT20J said:

Actually, there are two AN4 bolts which are 1/4-28. AN bolts have a tensile strength of 125,000 psi., so a 1/4 inch bolt in tension should be good for about 4000 lb before it fails based on a minimum cross sectional area of about .0364" at the bottom of the threads.

Don't you just love it when someone uses facts and calculations rather than just gut feelings.

[N201MKTurbo]

12 hours ago, DGates said:

I use an engine hoist attached to the engine mount.  I've used web straps but have also just made a loop out of some rope to connect the engine mount to the jack hook.  Can't use the engine hoist hook directly on the engine mount tubing, no room for the hook.  I'm a bit leery of using the tail tie down ring, as one is putting a 1/4-20 thread in tension and hoping that it holds.  Going ker-splat on the nose would be painfully expensive to repair, likely several months of down time so I'm trying to minimize risk as much as possible.  I'm always nervous when i have the plane on jacks, too... I do it as required, but I jack it, do the necessary, then get her back onto the tires and *certainly* don't leave it jacked up overnight....

Why not leave it on jacks overnight? My jacks will barely fit under the wings when all the way down so if they droop all the way down nothing bad happens. I’ve left it on jacks for weeks.

[A64Pilot]

9 hours ago, PT20J said:

Actually, there are two AN4 bolts which are 1/4-28. AN bolts have a tensile strength of 125,000 psi., so a 1/4 inch bolt in tension should be good for about 4000 lb before it fails based on a minimum cross sectional area of about .0364" at the bottom of the threads.

Until it’s been fatigued, by something like I don’t know, being tied down in high winds? I’ve seen broken main spars from fatigue, spars who’s tensile strength is measured I’m sure in the millions of pounds, but broke with not much more than 5,000 lbs.

Obviously failures are rare, but things do happen.

Says the guy with a Staph infected total knee replacement, Doc said don’t worry it’s not a concern, infections are so rare it’s not a concern.