30 year journey to my PPC

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k9flyer

Filing Flight Plan
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Dec 27, 2015
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k9flyer
Hello All,

I have been chasing my PPC since late 1987 (had 59 hours). Not for lack of money, but time. When you own a business (oops, I mean when it owns you) one has to stoke the fires (if ya know what I mean!!)

I bought a C150 back in Aug 2015. I have a flight instructor with over 10K hours of teaching and is an A/P as well. Great guy!

I have been studying ground school via King Schools, (actually I have ASA too). Solo'd Dec 14, 2015 and did it in 13 hours. My last solo was in Minot ND long ago with 18hrs.

I have a challenge that I will ask for some assistance with.

They are math or calculation problems using my 1967 C150 POH.

1. Determine Landing distance required to land at a 4000' msl airport, with a temp of 90 degrees and a headwind of 6 kts. How many feet to land? I'm stuck.

2. What is the no wind range for my plane using 65% of power at 6000 ft.

Here is the URL for the charts:

Can I solicit some help?
 
Good luck on your training! Do some ground with your CFI and he'll be happy to answer your questions.
 
I'll give you a little help but its going to take me a few minutes to write up the response.
 
Welcome to POA and good luck with your training.
 
k9flyer said:
1. Determine Landing distance required to land at a 4000' msl airport, with a temp of 90 degrees and a headwind of 6 kts. How many feet to land? I'm stuck.
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The landing distance table gives us some info, but it's not at 4000' or 90*, or 6kts of headwind, so first you just need to interpolate the values in the Landing Distance table for 4000ft.

Given:
2500ft & 50*F - GND Roll = 470 & Total to Clear 50ft = 1135
5000ft & 41*F - GND Roll = 495 & Total to Clear 50ft = 1195

So we know that at 4000ft our standard temperature will be somewhere between 41 and 50 (probably 43 or 44) and our distances will be ~ 490 & 1170 (Guestinterpolating here)

Mathmatically y-y1=m*(x-x1) where m=(y2-y1)/(x2-x1). So lets figure out the standard temperature using this (there are other easier methods too for this one)
x1=2500
y1=50
x2=5000
y2=41

m=(41-50)/(5000-2500) = -9/2500 = -0.0036

solving for y, y=m*(x-x1)+y1 so y=-0.0036*(4000-2500)+50 =-5.4+50=44.6F

Continue this same process with the landing distances.
2500ft & 50*F - GND Roll = 470 & Total to Clear 50ft = 1135
5000ft & 41*F - GND Roll = 495 & Total to Clear 50ft = 1195

So for total to clear 50ft would be
x1=2500
y1=1135
x2=5000
y2=1195

m=(1195-1135)/(5000-2500)=60/2500=0.024
y=0.024*(4000-2500)+1135=36+1135=1171

So for 4000ft/45F we get a distance of 1171

Now we need to adjust for temperature, we are instructed to increase the distance by 10% for each 60F above standard. @ 90F we are (90-45) = 45* above standard which is 3/4 of 60 so we need to increase the distance by 45/60*10% = 7.5% so we get our distance by multiplying 1171 by 1.075 and we get ~1260 ft.

Finally we need to adjust for headwind. Our note states to DECREASE the distance by 10% for every 4 knots of headwind. We need to decrease the distance by 6/4*10% which is 15%. 1260*(1-.15)= 1070ft.

I may have made a math error somewhere. If you don't understand then you just need to sit down with a CFI. The toughest part is interpolating to figure out the numbers in between the numbers in the table.
 
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k9flyer said:
2. What is the no wind range for my plane using 65% of power at 6000 ft.
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Well one way to figure it out would be to fly along on a no wind day and wait and see when the fan quits turning, but that wouldn't be much fun would it?

This is another one that to get the precise answer requires a lot of interpolations. The relevant data we are given in the "CRUISE PERFORMANCE" table is listed below

| Alt. | %BHP | Rng22.5 |
--------------------------------------------
| 5000 | 66 | 515 |
| 5000 | 58 | 545 |
| 5000 | 65 | R1 |
| 7500 | 68 | 515 |
| 7500 | 61 | 540 |
| 7500 | 65 | R2 |

Use interpolation as discussed before to figure out R1 @ 65% and R2 @ 65%. I'm just going to guess and say R1 = 520 and R2 =525.

Then you'll interpolate again between 5000ft and 520 and 7500ft and 525 (Altitude doesn't really have a huge effect though) and a quick guess of 524 would probably be right.
 
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Wayne F, I DO appreciate the time you took to do these problems for me.
 
I hung out with my grandpa in his hangers and he took me flying in his experimentals when I was 7-10 yrs old. I loved every second of it and then he died. This was 1976.

I didn't get inside another small plane til my discovery flight several weeks ago. I've got 10 hrs now, am getting close to solo, and will have my ticket sometime in 2016.

Of course I didn't start training back in 1973 but that's when the interest was sparked. 43 yrs.

Got married and started a family decades ago, kids are raised, college is paid for, business running fine, TIME TO FLY!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
k9flyer said:
Wayne F, I DO appreciate the time you took to do these problems for me.
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No problem, although I hope you understand the concepts and can work through the problems yourself. For your pp training you should know how to work these. Once you get your PPL you can get close enough by looking at the surrounding ranges of values, or just take the worst case number instead of interpolating. It's usually not too far off from the interpolated values.
 
If you're asking for help on the the performance questions because you need to be able to demonstrate the ability to interpolate, then the presented answer is great.

If, however, you need it for r/w performance planning...then the variation of 20ft on the performance figure isn't worth calculating. Use the higher number and you're good to go.
 
coma24 said:
If you're asking for help on the the performance questions because you need to be able to demonstrate the ability to interpolate, then the presented answer is great.

If, however, you need it for r/w performance planning...then the variation of 20ft on the performance figure isn't worth calculating. Use the higher number and you're good to go.
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Yep. I agree with this. I haven't calculated the exact numbers (aside from this exercise) since my private pilot checkride. Just use the most conservative numbers that are close to your numbers.
 
It took me from Feb '79 to Dec 31 '01. 23 years. I swore I'd never do another rating like that. Got my instrument before the next year was up doing a 2 week accelerated course.
 
I just started ground school 1981. Got blindsided by a Redhead. Redhead won hands down. Took me almost 30 years to get back to it. Got my cert in 2015.
 
Ghostflyer1 said:
I just started ground school 1981. Got blindsided by a Redhead. Redhead won hands down. Took me almost 30 years to get back to it. Got my cert in 2015.
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Yeah, but the tortoise won the race! Good for you.
 
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