Using prop to jack up airplane?

[carusoam]

Great pic, Dustin!

Fabulous follow-up.

Best regards,

-a-

[Mooneymuscle56m]

If you ever witness a gear up recovery, the ones I’ve seen do the least damage is lift gently by the motor mount.  Top cowl off, two guys on the tail.  
 

YouTube has a video of a Mooney getting picked up by the wing root, not pretty. 

[Alan Fox]

On 12/11/2019 at 8:48 AM, GeeBee said:

I have to say I have seen a very well known and respected MSC use two jacks under the wing, and an engine hoist with fan belts around the prop for the nose.

 

SL 231 (hartzellprop.com)

[Alan Fox]

On 12/11/2019 at 8:48 AM, GeeBee said:

I have to say I have seen a very well known and respected MSC use two jacks under the wing, and an engine hoist with fan belts around the prop for the nose.

 

Time to find a new shop... SL 231 (hartzellprop.com)

[OR75]

I am surprised that there is no service letter saying that flying may lead to an unsafe flight condition 

[Mooney-Shiner]

Thank you. This thread helped me to take the wheels off for rotor/tire/tube replacement and wheel repaint. Not to hijack the thread (no pun), but does anyone know what metal these wheels are made of? I was going to strip them, bake them in the oven (to pull the humidity out) and paint them.  

[N201MKTurbo]

The wheels are made of magnesium. 

They are cad plated. If all the plating is gone, you need to paint them. Back when you could get it, zinc chromate worked great. I'm not sure what to use these days.

[N201MKTurbo]

Why did you remove the brake caliper? Now you will have to bleed the whole system. If I do remove the caliper, I quickly cap the hose. I fill the caliper with fluid and quickly reconnect the hose. A couple of peddle pumps out the bottom and the brakes are good as new.

[PT20J]

Repainting procedure is in the Cleveland manual. 
AWBCMM0001-12.pdf

[N201MKTurbo]

1 hour ago, PT20J said:

Repainting procedure is in the Cleveland manual. 
AWBCMM0001-12.pdf

They don't give a lot of guidance on the type of paint or primer.

I have been using the magnesium conversion coating, but it doesn't seem to work as well as zinc chromate. I would definitely cook them in an oven before painting to drive the moisture out of the magnesium. 

They seem to list every kind of paint. It's nice to know I've been masking them properly all these years.

[PT20J]

37 minutes ago, N201MKTurbo said:

They don't give a lot of guidance on the type of paint or primer.

I have been using the magnesium conversion coating, but it doesn't seem to work as well as zinc chromate. I would definitely cook them in an oven before painting to drive the moisture out of the magnesium. 

They seem to list every kind of paint. It's nice to know I've been masking them properly all these years.

They give some paint specs in here.

WBtech.PDF

 

[PT20J]

2 hours ago, N201MKTurbo said:

It's nice to know I've been masking them properly all these years.

That's because you have a lot of experience and know what you are doing. I don't have your experience, so I have to look this stuff up 

[Jim F]

On 12/11/2019 at 8:11 AM, PT20J said:

Mooney doesn't want you to hold down the tail or lift from the prop  (SIM 20-114). Someone posted that Lycoming doesn't want you to lift more than the engine weight from the engine lift point. So may the Force be with you.

Many shops attach a weighted tail stand to the tail tiedown with some shot bags on the horizontal stabilizer. Last time we swung the gear, we lifted at the engine. I know Don Maxwell puts a fan belt around each blade shank. Over all the years of using various techniques, has anyone heard of a problem attributed to the lifting technique?

Skip

Hi Skip,  

Four or more years ago, I saw someone post here a pic of a Lycoming with a crack in the case right under the lifting eye.  At the time, I thought the only possible reason for the crack was jacking the nose of the aircraft with the engine lifting eye.  

Jim

[OR75]

so we are left with magnetic levitation ? with the engine being aluminum ... i am not even sure that even would work

[PT20J]

1 hour ago, OR75 said:

so we are left with magnetic levitation ? with the engine being aluminum ... i am not even sure that even would work

You can put a heavy strap around the engine mount and lift from there -- no one has said not to do that. 

[Fly Boomer]

3 minutes ago, PT20J said:

You can put a heavy strap around the engine mount and lift from there -- no one has said not to do that. 

I'm thinking I might take half of the weight on the engine, and half on the tie-down.

[Hank]

You aren't supposed to use anything but wing jacks. Mooney says to not pull down on the tail; Lycoming says not to lift the nose by the engine hoist points; Hartzell and McCauley say don't lift the nose with a prop jack.

So use the jack points under the wing, and the plane is supposed to magically balance while someone climbs in to operate the gear and get back out, and be steady enough to remove the wheels . . .

We all just need large pouches of fairy dust!

P.S.--I wouldn't lift by the engine mount! That outs force.90° to the bolts, and they aren't designed for that. Having a couple of overstretched engine mount bolts break in flight could be unrecoverable!

[philiplane]

Neither the prop hub, nor the engine lifting lugs, are designed for lifting the entire airplane weight. Only for their own individual weights.

Wing jacks on the jack points, or airbags under the wing spars, are suitable.

Wood blocks and a jack under the firewall area are acceptable to lift the forward part of the airplane's weight. 

The engine mount itself isn't made for lifting either, though it will take more abuse than the engine lifting lugs or the prop hub or crankshaft.

[PT20J]

The engine mount on my M20J is attached with 4 AN4 bolts which each have a shear strength of 3730 lbs. The engine and prop weigh around 400 lbs and with a 1.5 factor of safety and a max load factor of 3.8 g that’s the equivalent of 2280 lbs. When we weighed my airplane, the weight on the nose wheel was only 639 lbs. Seems like the engine mount is plenty strong. However, I do what 90% of mechanics do and use a tail weight. 

[carusoam]

The long bodies take this discussion to the next level…

The Ovations have a jack point designed into the engine mount…

 

and for total confusion of the new mechanic…. The placard on the outside of the cowling simply says ‘jack point’

it would have been a bit nicer… if the placard said ‘Jack point on engine mount, under cowl, look in the baggage compartment for a set of points used for jacking’ 

 

Losing a part of a prop blade in flight… will surely test the strength of the bolts holding things through the firewall….

 

My M20C broke the welds off a lower leg of the engine mount, releasing 1/4 of the connections to the firewall…

Flying around for a few months not knowing of its new condition… was interesting…

The signs were not extremely obvious to the casual observer….

1) variable engine sag, slightly more than usual one day, then near rubbing on the cowling the next…. Then back to slightly more than usual….  Problems don’t usually fix themselves… not even partially…

2) small air bubbles vibrating in the compass… but no obvious increase of vibrations being felt.

3) Last flight was to an MSC….  When an ordinary mechanic could have seen what was happening…

 

yikes…

Decision to upgrade one way or another followed that experience… 

 

PP thoughts only, not a mechanic…

best regards,

-a-

[Pinecone]

8 hours ago, Hank said:

P.S.--I wouldn't lift by the engine mount! That outs force.90° to the bolts, and they aren't designed for that. Having a couple of overstretched engine mount bolts break in flight could be unrecoverable!

Bolts are supposed be loading in shear when possible.  That is, 90 degrees to the length of the bolt.

With lifting by the mount, I would be more worried about bending a mount tube.  So I would make sure the strap is at a cluster of tubes.

[wombat]

Are the jack points in front of or behind the main gear?    Is the engine lifting loop in front of or behind the nose wheel?   @PT20J helpfully notes the weight on the front wheel isn't all that much more than the engine.

What does the fuselage do if you remove the engine?  If the plane will fall back on its tail from the jack points if the engine is removed, then lifting by the engine hoist is acceptable.  

 

Why not do multiple things?    Add a bunch of very aft weight....   120# in the luggage area and 25# on each side of the horizontal stabilizer.    Given their arms relative to the jack points, the remaining weight to be lifted by the engine hoist would be less than the engine weight.        In that case you are not 'lifting the aircraft by the engine hoist', you are partially lifting the weight of the engine, which is 100% acceptable from the engine manufacturers.

 

I don't know if putting mass on the horizontal stabilizer is acceptable.    Of course the downward force on the structure is fine (How do you think you lift the nose when taking off?) but putting even soft weights on the tail might bend the skin or crush a rib. 

[Hank]

10 hours ago, wombat said:

I don't know if putting mass on the horizontal stabilizer is acceptable.    Of course the downward force on the structure is fine (How do you think you lift the nose when taking off?) but putting even soft weights on the tail might bend the skin or crush a rib. 

I've done that a couple of times. A case of oil on each stab, some old bound approach plates, my roll of wrenches, etc.

[A64Pilot]

On 12/11/2019 at 1:18 AM, DustinNwind said:

Can you safely jack an airplane up by it's prop to get the front wheel off?

 

Thanks,

 

Dustin

Yes, but as you found out a piece of 3/4 “ pipe and a jack is better.

There is not as far as I have been able to discover any approved method for lifting a mid body Mooney for retract tests.

However as PT20J points out lifting the engine mount isn’t prohibited, that was how I used to lift my Maule when going from 8.5” to 29” tires, it lifted almost the entire aircraft that way due to it being a tailwheel aircraft. Engine mounts are very strong.

Personally I lift my McCauley prop with two soft nylon straps I got at Harbor freight, each rated I believe for at least 5,000 lbs. They each wrap three or four times around each blade.

I think if done correctly all methods are fine, but any if done incorrectly can cause damage.

Personally I’m uncomfortable lifting from the engine lift point, now if someone built one that connected to two bolts or built a spreader bar that attached to at least two points like used on turbines then I’d be more comfortable, it’s just that a possible crack in the case is SO expensive it makes me nervous but then I’m risk averse.