Is this true or a rumor?

[Glen Davis]

My friend had the nose wheel tire on his K model go flat this evening upon landing. Fortunately he was able to make it off the runway so the airport did not have to be closed down. I asked him if it caused a prop strike. He said no and that is because (and here is my question) to be certified a plane has to have 9 inches of proper clearance even if the nose wheel is flat and the strut is completely compressed”. Well I actually did not measure it but I don’t think I have 9 inches of prop clearance in my J model even when everything is in perfect condition. Any truth to this certification requirement? And as a follow-up question, what type of suspension system does the nose wheel on a J model or a K model have? Is it a piston or rubber donuts or some thing else?

 

 

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[Mooney in Oz]

49 minutes ago, Glen Davis said:

what type of suspension system does the nose wheel on a J model or a K model have? Is it a piston or rubber donuts or something else.

All M20’s have rubber donuts.

[PT20J]

Almost, not quite. Here’s the reference in CAR 3 which is the basis of certification for the M20 series.

[PeteMc]

10 hours ago, PT20J said:

Here’s the reference in CAR 3

So out of curiosity...  Is the 9" clearance on a tail wheel aircraft while the tail wheel is touching the ground?  (e.g. parked or slow taxi)  Or while in the takeoff roll when the tail is elevated.  And if it is 9" when the TW is down, does it then have a 7" clearance on the takeoff roll?  (Some day I gotta get around to that endorsement...)

 

[A64Pilot]

31 minutes ago, PeteMc said:

So out of curiosity...  Is the 9" clearance on a tail wheel aircraft while the tail wheel is touching the ground?  (e.g. parked or slow taxi)  Or while in the takeoff roll when the tail is elevated.  And if it is 9" when the TW is down, does it then have a 7" clearance on the takeoff roll?  (Some day I gotta get around to that endorsement...)

 

Level takeoff or taxi, whichever is most critical. I don’t believe 7 inches plays into anything on a conventional gear airplane.

[PT20J]

59 minutes ago, PeteMc said:

So out of curiosity...  Is the 9" clearance on a tail wheel aircraft while the tail wheel is touching the ground?  (e.g. parked or slow taxi)  Or while in the takeoff roll when the tail is elevated.  And if it is 9" when the TW is down, does it then have a 7" clearance on the takeoff roll?  (Some day I gotta get around to that endorsement...)

 

Just read it again…slowly 

[PeteMc]

3 hours ago, PT20J said:

Just read it again…slowly 

Duh!   Thanks.

[carusoam]

Glenn,

The nose gear is tall enough to protect the engine from a prop strike under most conditions….

For all Mooneys…

But, with a missing tire… the blades will be closer to the ground than usual….

 

Where Mooneys have had prop strikes…. Holes in the ground.  Pot holes in the pavement, or washed out soil taxiing off the pavement….

The hole required to cause a prop strike just got a few inches smaller, as the tire deflates….

MS experiences only, not mine…

Best regards,

 -a-

[Glen Davis]

Thanks, all.  I thing it's a good idea to measure the distance from the tip on the prop to the ground to see if the donuts in the nosegear are up to snuff.

[Fly Boomer]

On 7/24/2022 at 11:38 PM, PT20J said:

Here’s the reference in CAR 3

I read 7 inches with air in the tire and "positive clearance" when flat.

[A64Pilot]

11 minutes ago, Fly Boomer said:

I read 7 inches with air in the tire and "positive clearance" when flat.

And the critical gear (nose wheel here of course) fully compressed

But we have all heard or seen prop strikes on level hard surface runways, without flats, so it can be done.

[Hank]

5 minutes ago, A64Pilot said:

And the critical gear (nose wheel here of course) fully compressed

Our rubber pucks don't compress much. Unless you hit the runway with a whopping descent rate . . . .

[OR75]

Anyone still have the shock absorber on the nose wheel ?

 

[Hank]

Not me

[carusoam]

7 hours ago, OR75 said:

Anyone still have the shock absorber on the nose wheel ?

 

 

Hard to find on any MSer planes…

Many reasons to remove…

No reasons to keep…

All documented around here somewhere…

Best regards,

-a-

[OR75]

12 hours ago, carusoam said:

Hard to find on any MSer planes…

Many reasons to remove…

No reasons to keep…

All documented around here somewhere…

Best regards,

-a-

What would be the reasons to remove ? 
apart from a few lbs saving 

I still have it installed 

[jaylw314]

21 hours ago, Hank said:

Our rubber pucks don't compress much. Unless you hit the runway with a whopping descent rate . . . .

Have you SEEN some of my landings?? 

[A64Pilot]

7 hours ago, OR75 said:

What would be the reasons to remove ? 
apart from a few lbs saving 

I still have it installed 

There are times when I’d like to have one, specifically sometimes I get into bumps that get the nose pogoing up and down, not dangerous, but annoying. Slow down quickly and it stops, I’m talking walking speed not fast taxi.

A shock would dampen this resonant movement

[BobbyH]

On 7/26/2022 at 1:58 PM, OR75 said:

Anyone still have the shock absorber on the nose wheel ?

It was my understanding that "shock absorber" is actually a shimmy damper.  If you look at the picture the rubber disks are still there. 

[carusoam]

11 hours ago, OR75 said:

What would be the reasons to remove ? 
apart from a few lbs saving 

I still have it installed 

This thing is technically the shimmy damper….

A bolt on device for a problem we don’t have…

Proper set-up of the nose gear keeps the shimmy out…

If it doesn’t, there are wear items that get replaced…

Taking the parts off is a maintenance procedure…

The savings… must be a whole LB UL.   

The device is soooo old.  It probably doesn’t provide any shimmy absorption… like a 50 year old shock absorber…

PP thoughts only…

-a-

[OR75]

maybe remove it and see if there is  a difference . put it back if if i don't like how it feels 

[alextstone]

3 minutes ago, OR75 said:

maybe remove it and see if there is  a difference . put it back if if i don't like how it feels 

I did that first part with a spouse once who refused to fly with me....there was a difference, in a good way

[Fly Boomer]

17 hours ago, BobbyH said:

If you look at the picture the rubber disks are still there. 

And the disks are going to limit travel with or without the other gizmo.

[Pinecone]

Shock absorbers are not typically for travel limit, but they an do wo.

They are to dampen motion.  So that the nose does not continue to bounce up and down after hitting a bump.

[Rjfanjet]

When I replaced my engine mounts, got to the magic 9" clearance. Before was 7.