Mental math question

D

Dalma459

New Member
Studying for delta interview and can't find a good mental math for fig out distance between two lat and long? Anyone got one? Also anyone have one for a good acceleration distance check on the runway as well?
 
~60 nautical miles between each degree of latitude. Longitude doesn't work well because it's dependent on your latitude. If you're looking for the direct distance between two lat/longs, I'd mark the two points on the side of a piece of paper, then use the 60 mile rule to get a rough ballpark using degrees of latitude.

Or just make it easier and use your plotter. :)
 
Here's one for you geniuses... How do you solve this? It's not in the mental math book unfortunately.
You are on the 090 radial at 20 DME. What heading would you fly to go direct to the 60 DME fix on the 190 radial of the same VOR?
 
juxtapilot said:
Here's one for you geniuses... How do you solve this? It's not in the mental math book unfortunately.
You are on the 090 radial at 20 DME. What heading would you fly to go direct to the 60 DME fix on the 190 radial of the same VOR?
Click to expand...
Pencil trick
 
The way we used to do problems like that in the Navy is actually pretty easy. You can even do it on a piece of paper. Imagine a compass, RMI or VOR and draw the 090 and 190 radials (The VOR, RMI or compass will be the center of your paper). Since 60 miles is 3 times the length of 20 miles, the 60 mile mark will be 3 times the distance from the VOR as the 20 mile mark.Take a straight edge and connect the two points (the 20 and 60 DME points). Then, slide the straight edge over the direct center of the compass, RMI or VOR at the same relative angle as you just established connecting the two points. The edge of the straight edge will now line up on the outer heading numbers to show you the heading you need to fly to connect the 090/20 and 190/60 points. You should be able to get it within a few degrees. Then, compensate a little bit for the wind and you'll nail it. Try it a few times, it gets easier.
 
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juxtapilot said:
Here's one for you geniuses... How do you solve this? It's not in the mental math book unfortunately.
You are on the 090 radial at 20 DME. What heading would you fly to go direct to the 60 DME fix on the 190 radial of the same VOR?
Click to expand...

Dugie8 said:
Pencil trick
Click to expand...

Type XYZ/190/60 into your FMS and then go direct to fix that is generated :)

Or you could do the Pencil Trick like @Dugie8 suggested. (EDIT: and Bill beat me to posting a better example of by 5 seconds)
 
wildfreightess said:
Oh my God, I am far too stupid to work at Delta.
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Possibly me too. Can anyone verify the practical application of this mental math? I'm not opposed to learning it, but I want to know that I'll be using it realistically. I was pretty sour about having to demonstrate NDB approaches 14 years ago and I have never ever shot one in actual to this day, so I still kind of resent it.
 
There is no practical application for this in today's flying environment. I do 3-1 (or sometimes 2-1!) math for descent planning almost constantly, but that's because of the flying I do. The guys flying into airports with arrivals and vectors for a downwind don't even have to do that very much.

It's used as a screener that you can think analytically and that's about it.
 
I had a book that has long since gone out of print that did that in programs written in Basic. It was intended for both sailing and flying. Unfortunately, I couldn't find that book in the house. However, doing a Google search I found a lot of those type resources oriented towards sailing. Here is one:

http://www.movable-type.co.uk/scripts/latlong.html

Personally, it has been so many years since I've done any serious math that just looking at the formulas makes my head hurt, but you might find them useful.
 
Most of this type stuff is not math based it's more spacial orientation recognition. If you are on the ABC VOR 180 radial at 100 miles and they want you to hold on the ABC 110 radial at 40 miles, you really have to have some basic knowledge on how to get there. It's really not that hard to pick up once you've been shown it a few times. Try looking at a RMI face as if you were looking down on it, not at it. Find where your airplane is on it and then find out where you want to go. Draw an imaginary line in your mind as to what direction it will take to get there....you won't be off by more than 5 or 10 degrees. Seriously, don't make it harder than it is.
Without thinking much about it, I bet a heading of about 025 to 030 would get you pretty close. That's doing it the manual way. Fortunately the FMCs today do all the work for you but you still need to have a basic understanding of doing it the old way. It sucks, I know.
 
Cal Goat said:
Possibly me too. Can anyone verify the practical application of this mental math? I'm not opposed to learning it, but I want to know that I'll be using it realistically. I was pretty sour about having to demonstrate NDB approaches 14 years ago and I have never ever shot one in actual to this day, so I still kind of resent it.
Click to expand...

BobDDuck said:
There is no practical application for this in today's flying environment. I do 3-1 (or sometimes 2-1!) math for descent planning almost constantly, but that's because of the flying I do. The guys flying into airports with arrivals and vectors for a downwind don't even have to do that very much.

It's used as a screener that you can think analytically and that's about it.
Click to expand...

The test is making sure you can do that level of mental math.

100% of my arrivals are backed up via mental math energy management to this day. Of course never have I done mental math directs.... they just want to know that you can function on a higher level which ensures reliable function on the normal levels.
 
BobDDuck said:
There is no practical application for this in today's flying environment. I do 3-1 (or sometimes 2-1!) math for descent planning almost constantly, but that's because of the flying I do. The guys flying into airports with arrivals and vectors for a downwind don't even have to do that very much.

It's used as a screener that you can think analytically and that's about it.
Click to expand...
I can think of one reason to actually use it in the airplane, besides making sure you can think that way, and it's to "sanity check" a "Southernjets 1253, fly heading (___), direct (____) when able" instruction, in the absence of drool-proof moving maps and advanced RNAV. "You are here, which way do you turn, roughly, to go over there?"

Basically, what @CaptBill said.
 
The way I looked at the lat/lon problem was to use the pythagorum theorum a2 + b2 = c2. Each degree is 69 miles so if you were to connect the two points with a line then also connect them with a vertical and horizontal line to create a right triangle you can solve for the long (c) distance. This was the only way I could figure out this problem manually.
 
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