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Prop clearance


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Ok, got some issues here on my M20C. Got new prop and I got only 8” clearance, it should be 10.5”

here are some photos of measurements. Naturally, you will go for new  shock desks, however, if I install new ones, I’ll gain only 1/4 inch at gear. Would that be 2.5” at prop, I don’t believe so. I do have Correct tire 5.00-5.

sugestions welcome

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1851BBD1-1381-46DF-965B-E571EDC307A1.jpeg

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Looking at your windows in another picture you have posted, you have an early 'c model.  Mine also has cruddy prop clearance.  One thing you might check is the motor mounts...  How much is that engine sagging?  looks somewhat significant from the picture above.  I hear replacing the motor mounts is a speed mod...

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Things to check...

1) Diameter of new prop... compare to the original...  (document search)

2) Donuts look a bit compressed, but not 2 inches... (age of donuts?)

3) Speaking of compression, how much weight is in the plane? (Fuel full?)

4) You can always Check to see if the nose is low on the ground...  the seam on the side by the baggage area should be near level...

5) Engine Mount donuts being worn will drop the prop kind of low... large gap at the top, small gap at the bottom

6) what made my C drop the engine low was a broken engine mount.  One of the lower bolts wasn’t holding the engine up...  this caused the prop to be really close to hitting the lower lip of the cowl... took a few flights to recognize what was happening...

7) The POH has a few measurements early in the first few pages... see if you can match some of these...

8) Lastly, What is the hole with the missing fastener? Doc will be along later... :)

PP thoughts only, not a mechanic...

Best regards,

-a-

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Albatros; Is that a top prop I have been hearing about ? Have you flown it yet ? I am thinking on installing one on my aircraft after my recent experience, I believe the weight is slightly more than the OEM prop. I do not think it will drop your clearance that much, but I would check for diameter difference if any from your old one as Carusoam says.

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Albatros’ prop has the decal of hartzel and the curves of a TopProp...

Check their website for prop options...

for the IO550 there are three options that weigh differently... thick blades, thin blades, and composite blades...

The composite blades drop pounds off the nose.

Compare to what MT has to offer.

Best regards,

-a-

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According to the Type Certificate the original propeller was 74” diameter, and 72.5” for repairs.  The new top prop shares the same measurements.

Clarence

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Hey, the other owner of the Mooney in question here...

So the prop is the correct one, and same diameter as the one before. Engine mounts.. we'd have to look into that, but that would not be causing our problem here, because the entire airplane is sitting nose low. The tail is about 5 inches higher than other models on our field. 

No damage to the nose gear.

It is the correct tire

Donuts are 12 years old... but per measurements with other airplanes are still like new. 

So it's not the prop. Not the engine mounts. Not the tire (it maybe could be inflated a little more to give us 1/4 to 1/2 inch at the most). With the tail being high 5inches or so (again compared to all the other Mooneys at our field), it seems to be something in either the nose gear or main gear that's not rigged properly. 

One mechanic we talked to said that there's a bushing in the nose gear that if it's upside down, will lower the height of the nose... anyone know how to check this?

Albatros has tons of pictures of measurements and different parts in the nose gear. 

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53 minutes ago, yvesg said:

Nose gear issue for sure. Look at this picture which is similar in angle to yours. We see the whole shock disk assembly. On yours it is not coming out of the wheel well

I think it’s the angle of the picture (air intake). My C sits a lot flatter than a longbody. Not sure what models @AaronC is comparing to. 

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albatros,

Prop clearance on the C model Mooneys is aprox 9 3/4 inches. worn engine mounts is usually the big contributor to low clearance followed by worn landing gear biscuits.sounds to me like you have a combination of the two. my C with new mounts biscuits and prop has just a bit over 9" of clearance.

Brian

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2 hours ago, AaronC said:

Hey, the other owner of the Mooney in question here...

So the prop is the correct one, and same diameter as the one before. Engine mounts.. we'd have to look into that, but that would not be causing our problem here, because the entire airplane is sitting nose low. The tail is about 5 inches higher than other models on our field. 

Be careful which other Mooneys you compare with. Long body planes (beginning with the M model [Bravo, etc.]) sit tail down compared to ours, about a 4° higher angle of attack. E, F, J, K should be quite similar, not sure about Rockets and Missiles. 

Let us know what you find.

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4 minutes ago, Hank said:

Be careful which other Mooneys you compare with. Long body planes (beginning with the M model [Bravo, etc.]) sit tail down compared to ours, about a 4° higher angle of attack. E, F, J, K should be quite similar, not sure about Rockets and Missiles. 

Let us know what you find.

There's another C, F, and a J that we're looking at.

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Just now, AaronC said:

There's another C, F, and a J that we're looking at.

Something's not right. Check the easy stuff first:

  • Biscuits--ok
  • Nose gear--ok
  • Engine mount sag
  • Gear pushrods in the belly not bent
  • Gear preloads
  • Swing the gear and watch everything move
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2 hours ago, Hank said:

Something's not right. Check the easy stuff first:

  • Biscuits--ok
  • Nose gear--ok
  • Engine mount sag
  • Gear pushrods in the belly not bent
  • Gear preloads
  • Swing the gear and watch everything move

I will add tire pressure as an easy check as well - overinflation on mains/underinflation on nose.

Do you know for certain what clearance you had with the previous prop, or does this one maybe just look lower than before because of the new shape changing your view of it?

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It's hard to tell from the pictures but those tires look like they might be overinflated.  IIRC it should be 30 PSI for all tires on an M20C.  When I inflated the tires on my M20D to 30 PSI they always looked a little flatter than what I see in your pictures.

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Recheck time....

recheck the model number on the prop... see if it matches the paperwork...

recheck the paperwork to make sure it is all correct... proper for the M20C...

recheck the clearance to the ground on a level surface with a level on the seam line...

Recheck the clearance listed in the POH...

If this is all as expected... you have a real gear mystery!  

Best regards,

-a-

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1 hour ago, mooniac15u said:

It's hard to tell from the pictures but those tires look like they might be overinflated.  IIRC it should be 30 PSI for all tires on an M20C.  When I inflated the tires on my M20D to 30 PSI they always looked a little flatter than what I see in your pictures.

Yiu are right--M20-C tire pressure is 30/30/30 psi for nose/left/right tires.

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It does look like the lower part of the nose gear has a greater angle aft than others. Two of the m20-202 spacers on the nose gear tower would do that.  That spacer adds caster to the nose wheel to make it track down the runway smoothly. Two could cause a larger angle aft on the lower nose gear and reduce prop clearance. It’s not difficult to check. 

Edited by jetdriven
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52 minutes ago, yvesg said:

Here is another photo. Still think it is a nose gear issue.

088E8C0B-5C1A-4DC3-B029-2A328621CA10.png

Your prop is off-center toward the ground. It should be almost even with the top of the cowl opening, not the bottom. This is indicative of engine mount sag, corrected with spacers (not requiring removal, just loosening of bolts).

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