The International Cessna^® 170 Association

I need help with math.

Trying to determine the angle of inclination of asphalt apron in front of hanger door.


My strength is not what it used to be. I cannot push aircraft out of hanger alone. Apron slopes UP.

I measured a distance of 14 ft from hanger door lip. The height of line was 4 inches at hanger door.


I made good grades trig and algebra many years ago. Never used much math.

Perhaps there is an engineer among us that could tell me what degrees of incline based on knowing two dimensions.


regards

1.3639 degrees, I think

http://en.m.wikipedia.org/wiki/Grade_(slope)




W.

Easy problem: Rise divided by Run will provide the gradient. 4 inches divided by 168" (14') equals 2.3% slope.
Note this is not the same a degrees. , where a 100% slope is a 45-degree angle. (100% rise over run)
Therefore (rounding-off) slope in degrees can be divided roughly in half, therefore your 4'/168" would be about a 1-degree rise from horizontal...if the horizontal were truly FLAT.
Since the EARTH is a curved surface...(and the reason green airplanes fly being due to their takeoff surface being curved downward) ... it may slightly be more than that.

gahorn wrote:Easy problem: Rise divided by Run will provide the gradient. 4 inches divided by 168" (14') equals 2.3% slope.
Note this is not the same a degrees. , where a 100% slope is a 45-degree angle. (100% rise over run)
Therefore (rounding-off) slope in degrees can be divided roughly in half, therefore your 4'/168" would be about a 1-degree rise from horizontal...if the horizontal were truly FLAT.
Since the EARTH is a curved surface...(and the reason green airplanes fly being due to their takeoff surface being curved downward) ... it may slightly be more than that.

I haven't chimed in here for quite some time, but I find it hard to let an engineerng question just pass by.

Grady,

George's math calculating percent slope is actually more useful than the trigonometry. For the small angle involved, the percent slope is the the percent of the weight of the airplane you have to add to the force it takes to drag it on the level. In your case, it would take about 36lb more to drag a 1500lb airplane up your hangar apron than to drag it on the level (assuming no wind of course ).

What I did for pulling a plane into the hangar up a slope that gets a bit slippery when it is icy. Was to mount a electric winch to the back wall of the hangar. That with a line with loops about 10-12 feet apart and a hook on the end makes the effort a mater of pushing a button.

Thank you for the computation.

I'm embrarassed 1.36 degrees does not seem like much . I was thinking 4 or 5 degree incline out the hanger door.

Maybe I could use my son's weight lifting equipment. I should be able to handle 1.36 degrees.

Regards

Grady,

Check your tire pressure. If I recall correctly, I kept my tires at 24 psi (it has been two years sans 170, so I may be off). Regardless, when they got 4-5 psi low, it was not really noticeable to the eye, but it became very difficult to push the airplane, like the weight almost doubled. Refill the tires and things got easy again. We also had a small incline going into the hangar so it was obvious when things were amiss. My first indication of low tire pressure was my aching back and legs! Good luck.

Bruce

GOOD ONE, Shipp!

(And think of your take-off performance next time you think the ol' preflight seems the tires are just "OK".)