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Laning strip

 
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Gary Raser



Joined: 29 Aug 2015
Posts: 51
Location: Reading PA

PostPosted: Sat Apr 18, 2020 3:29 pm    Post subject: Laning strip Reply with quote

Hi All
I am looking for some help, I am putting a strip in my back yard, about 4 miles north of Morgantown Pa O03. I have taken the trees down and am meeting with an excavator to get it leveled out "some". My question is what do you think a reasonable up slope would be and how much left to right slope would work. It is about 1,500 ft long with about 1,100 feet usable, it will be a one way strip because of rising terrain after landing, with a heading of about 240 degrees.
I have a M7-235 C on 8.5 X 6 tires
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gbarrier
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Joined: 14 Jul 2011
Posts: 1441
Location: North Carolina

PostPosted: Sat Apr 18, 2020 4:36 pm    Post subject: Reply with quote

As flat as you can and cut down those darn trees at the ends. A clearway after the runway of less than 3 degrees is preferable.
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VA Maule
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Joined: 03 Feb 2013
Posts: 358

PostPosted: Sat Apr 18, 2020 4:49 pm    Post subject: Reply with quote

Now Gary you know that he only needs to cut those trees if he wants some of them "C" brand flyers to be able to visit Wink these Maules will jump right over them trees on the way out & forward slip back in over those trees like they are yard bushes Very Happy
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andy
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Joined: 06 Aug 2007
Posts: 1171
Location: Lake James, NC, USA

PostPosted: Sun Apr 19, 2020 2:07 am    Post subject: Reply with quote

Clearing some of the trees at the ends is a good idea. If the trees at the ends are tall, you'll need a steep, slow approach to clear them so that you can actually use the 1,100 feet of airstrip. You should be able to land or take off in 500 - 700 feet or so with an uphill strip. But there will be days when the wind won't cooperate or you'll be hot and heavy or not completely on your game. That's when you'll be grateful for the extra tree clearance. I've been in that situation several times.

You didn't mention the field elevation or how high and close the terrain is to the airstrip but in the mountains, density altitude can be a problem in Summer. Your 235 hp engine will climb out steeper than my 180 hp engine but it doesn't help you on landing distance. I've operated at a 1,000 foot one-way airstrip with a 16% gradient and tall trees at the end of the runway on a cliff near 6,684 foot Mt Mitchell. It only takes about 100 feet to land and about 300 ft to take off in that situation. However, the wind needs to cooperate. You don't want to take off with a strong tail wind. A 3% gradient will slow you down on landing but a steeper grade will slow you down faster.
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Andy
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andy
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Joined: 06 Aug 2007
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Location: Lake James, NC, USA

PostPosted: Sun Apr 19, 2020 2:48 am    Post subject: Reply with quote

Forgot to ask if your 1,100 foot usable already includes the unusable portion caused by the descent angle over the trees.

If not, then you might only have 926' of usable runway. Let's say that you have 50 foot trees on the approach end of the runway and you want to clear them by 20 feet. The opposite side of the right triangle is 70'. A steep but do-able approach angle could be 10 degrees. The FAA considers anything over 4.5 degrees to be a steep approach angle but Maules can easily better this. Most GA aircraft can handle a 10 - 15 degree approach angle although you may have to use power to arrest the descent rate before touchdown. Calculating the adjacent side of the right triangle results in 174' of unusable runway. Now your 1,100 foot strip is only 926'.

If you clear 174' more of the trees, then you'll get your 1,100 feet of usable runway back.
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Andy
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andy
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Joined: 06 Aug 2007
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Location: Lake James, NC, USA

PostPosted: Sun Apr 19, 2020 3:13 am    Post subject: Reply with quote

You'd think a math major wouldn't make mistakes with a spreadsheet and trigonometric functions. The correct length of the adjacent side is 397' not 174'. So the 1,100 foot airstrip is actually only 703' long with a descent angle of 10 degrees. You'd need to clear 397' more of the trees on either end to get your 1100 feet of usable airstrip back.
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Gary Raser



Joined: 29 Aug 2015
Posts: 51
Location: Reading PA

PostPosted: Sun Apr 19, 2020 1:36 pm    Post subject: Reply with quote

Thanks Andy
The field elevation is about 440 feet at the touchdown point and about 530 feet 1,100 up the hill at the fence-row/ property line. You mentioned an airstrip with a 16% gradient. that was 1,000 feet long. Does that mean that the difference was 160 feet from the high end to the low end? I am not really concerned about the trees on the approach end, after the trees I have about 400 feet to the touchdown point and the base of the trees are about 50 feet lower then the touchdown point.
I have a meeting with an excavator and I am thinking I will tell him it needs to be graded to a incline of 9% or less and left to right not more then 2%
Do you think that would work?
I have landed on some up hill strips and seem to land with tail first but I don't know how to find out what % of slope they are, Do you know how to get that information?
Thanks,
Gary
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andy
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Joined: 06 Aug 2007
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Location: Lake James, NC, USA

PostPosted: Mon Apr 20, 2020 2:03 am    Post subject: Reply with quote

Percent grade is calculated as rise (opposite) divided by run (adjacent). A 16% grade is the same as the tangent of a 16 degree angle (opposite/hypotenuse), which is around .29. 1000 foot hypotenuse (airstrip length) * .29 = 299 feet of rise.

In your case if you want a 9% grade, that would be the same as a 9 degree angle. Your rise would be 1100 * .1584 = 174 foot rise.

You tend to land tail first on an uphill grade because you see the ground rushing up at you faster than expected and you flare more to avoid bouncing.

The easiest way to get the slope is with Google Earth. Zoom into the airstrip in Google Earth and hover the cursor over the downhill end of the airstrip to get the elevation. Then hover the cursor over the uphill end to get the elevation. Subtract the downhill elevation from the uphill elevation to get the rise. Then measure the length of the airstrip in Google Earth with the ruler in feet. Then you know the opposite and hypotenuse sides of the right triangle. Lookup the sine of opposite/hypotenuse on the Internet. Then lookup the arcsine of that sine to get the angle, which is also the % grade.

Using he data that you gave me for your airstrip, the rise is 90'. The length of the airstrip is 1100'. The sine is 90/1100 = .0818. The arcsine of .0818 is around 4.7 degrees, which is your grade.

On an uphill grade you want the strip to be as level laterally as possible. It's hard enough to deal with an up-sloping runway without also having to deal with a side slope.
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JerseyJim



Joined: 19 Feb 2018
Posts: 29
Location: New Jersey

PostPosted: Mon Apr 20, 2020 2:11 pm    Post subject: Reply with quote

Hey Gary we are practically neighbors. I’m at N85 Alexandria Airfield.
If you haven’t gone to 9N1 Van Sant check it out. It’s a grass field. It has an upslope at the eastern end, it also has a slight side slope near the middle. Affectionately nicknamed Van Slant.
We should try to get a lunch flyin when the restrictions get lifted. Butter Vally 7N8, Sky Manor N40, Blairstown 1N7 or Cherry Ridge N30. Can probably get a few of the other Maule locals to join as well.
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Gary Raser



Joined: 29 Aug 2015
Posts: 51
Location: Reading PA

PostPosted: Mon Apr 20, 2020 3:22 pm    Post subject: Reply with quote

Thanks Andy and getting together sounds good Jim I will go check out N85
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andy
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Joined: 06 Aug 2007
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Location: Lake James, NC, USA

PostPosted: Tue Apr 21, 2020 12:16 am    Post subject: Reply with quote

I flew my Maule to Van Sant a while ago and did a J3 checkout. I remember the landing in the Maule. Runway 07-25 is a beautiful, large grass field with a side slope. The Maule wanted to turn downhill as soon as it touched down. When I did my preflight planning I didn't see any reference to the side slope. It's hard to detect in the air due to the fact that it's a large grass airstrip surrounded by trees without much background that displays the side slope. It's easy to handle once you're prepared for it.
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Andy
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JerseyJim



Joined: 19 Feb 2018
Posts: 29
Location: New Jersey

PostPosted: Tue Apr 21, 2020 3:23 am    Post subject: Reply with quote

Here is a good video of the upslope on runway 25 approach. (Not me)

https://m.youtube.com/watch?v=8mtSXnEkQ4c
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