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Ground clearance

bob888

Well Known Member
Just finished the nose wheel fairing and note only 1.25 in clearance from ground to forward edge of wheel opening. Is this enough? I can get more clearance by opening up the space around the tire but uncertain if aerodynamic penalty. There is more clearance for the mains, about 2.25 inches. Advice?
 
A little over a inch doesn't seem right. I'd have to go to the hangar to measure mine. I think all three of mine are about the same distance from the ground, but I don't recall ever measuring them.

My openings are about 3/4" all around the tire. I used my thumb as a guideline for spacing.

I have a set of wheel chocks from SteinAir that just fit under all three wheel pants. I went to look for the chock dimensions on SteinAir's site, but they weren't listed.
 
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Your decision

You can make this opening as tight or as large as you want.
If you think most of your operations are going to be out of paved runways,
Then less clearance is ok.
If your are planning grass runway operations, more clearance would be preferable.
Like Bob said, run your finger all around the opening and call it good.
A little speed penalty could be expected if you trim back several inches
 
You can make this opening as tight or as large as you want.
If you think most of your operations are going to be out of paved runways,
Then less clearance is ok.
If your are planning grass runway operations, more clearance would be preferable.
Like Bob said, run your finger all around the opening and call it good.
A little speed penalty could be expected if you trim back several inches

I think you guys are talking about two different things here.
The OP was asking about clearance up from the ground not around the perimeter of the tire.

Clearance around the tire is for tire deflection under dynamic load (tire deflection at touch down), so you would only do it differently for different runway surfaces, if you only planned to land harder on grass runways.

Trimming for a larger gap to the tire around the perimeter would have a small effect of changing the clearance above the ground, but not much.

As for an answer to the original question... I do not know what the norm is without taking a measurement, but 1.25" sounds a little close.
 
I'm not at the airport, but I would guess that mine is about the same, with weight on the front tire. As I recall, you can't quite push a 1.5" chock under there. I've flown off grass without problem, so far.
 
Ground clearance - I think this can vary with nose tire inflation pressure, and/or tread thickness (e.g., Monster re-treads).

Scott, I'd think nose tire clearance would take into account not just touchdown loading, but also subsequent bumps on less than perfect grass strips.
 
Wheel pant ground clearance RV10

Just one more data point. My nose wheel pant has 2.25" clearance at 45lbs. Mains have just under 2" at 48lbs

Gary
 
I think you guys are talking about two different things here.
The OP was asking about clearance up from the ground not around the perimeter of the tire.

Clearance around the tire is for tire deflection under dynamic load (tire deflection at touch down), so you would only do it differently for different runway surfaces, if you only planned to land harder on grass runways.

Trimming for a larger gap to the tire around the perimeter would have a small effect of changing the clearance above the ground, but not much.

As for an answer to the original question... I do not know what the norm is without taking a measurement, but 1.25" sounds a little close.
I think this nails it relative to perimeter clearance and field type as well as perimeter versus ground clearance.

I operate off a pretty rough grass field and kept my clearance 'thumb like'. Even in the mud, the pant perimeter and clearance is not really a factor.

The real factor in ground clearance are the chocks. If you travel and your plane routinely ends up being chocked, moved and otherwise handled by FBO folks, a too low ground clearance will result in a busted pant sooner or later.

Mine are low enough to always require "the short ones" wherever I go for both mains and nose. And they usually aren't short enough but I no longer get any cracks after some trimming.

I'm going down now and will measure with the hope of getting the actuals back here later.

Bill
 
I measured mine and have 2.5" in front and 2.25" clearance with the mains. Even with that, I cracked a main wheel pant somehow. This is with 40psi. Less than 2 inch clearance would be too small in my opinion if you are operating on anything other than very smooth taxi ways and runways.

I still can cruise at 175 ktas at 12,500, 19" and 2250 so it does not seem to affect performance much.

TJ
 
Just measured mine:

Front Wheel
3" at front
2.75" at sides
1.5" at rear

Main
2" at sides
2.5 inches front and back

The 2.5" on the mains in my experience is the minimum to survive "the chocks"

The 1.5" on the rear in the front is too low for "the chocks" and it constantly gets hung up. Fortunately most places don't bother to chock the front (I focus on tie downs)

Otherwise this setup has survived 5 years of rough field work.
 
Well I just got done fitting front wheel pant and thought I was doing a nice symmetrical job all the way around but after completing and rough finishing with plate nuts and screws I realize that my pant to floor height is 3 1/4 to ground all the way around. That makes for a nice 3/4 inch around sides of tire but more like 1 1/2 at front and rear. I could add more material at the bottom all the way around but would it be necessary? Am I now defeating some of the aerodynamic advantage of the wheel pant? Am I overthinking this? Should I just realize this will be better for grass strips?
 
OK since I got carried away with the trimming now I will be adding a skirt layup to the bottom and then cutting that back so I have a ground clearance of about 2 inches. Two steps back for another step forward.
 
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