Mental math question

[Flyjustin]

Holy crap. I haven't taken a math class since highschool, and they stopped teaching mental math in 5th grade.... Deltas out for me.

 

[Autothrust Blue]

Holy crap. I haven't taken a math class since highschool, and they stopped teaching mental math in 5th grade.... Deltas out for me.

Though math is involved (especially to finesse it), this is more lateral situational awareness.

 

[ian]

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.

only problem is the delta test choices will be like:
a. 022
b. 025
c. 028
d. 035

 

[PeanuckleCRJ]

only problem is the delta test choices will be like:
a. 022
b. 025
c. 028
d. 035

IIRC, a calculator is allowed. Draw a triangle, hit up some simple trig and you'll be right on it.

 

[ian]

IIRC, a calculator is allowed. Draw a triangle, hit up some simple trig and you'll be right on it.

nope, pen and paper, that's it....assuming they do it the same at DL that the did at CPZ.

 

[CaptBill]

only problem is the delta test choices will be like:
a. 022
b. 025
c. 028
d. 035

Go with B. My dead reckoning skills say it's a little more than 22.5 and less than 028. 025 should just about do it. I'll punch it in the FMC tomorrow and see if I'm right. Maybe we can have a 15 minute point to point seminar at NJC. Sounds fun eh?

 

[Trip7]

IIRC, a calculator is allowed. Draw a triangle, hit up some simple trig and you'll be right on it.

Not anymore

 

[Screaming_Emu]

I'm right there with you. Perhaps if I'd went to college. I still wouldn't be good enough to land in Juneau though.

I went to college...still lost on all of this.

 

[juxtapilot]

Okay nerds.

Besides doing a bunch of trig to figure this one out, what do you think the correct answer is?

KTAS=300. Aircraft is going to teardrop outbound on the 060 radial and wants to roll inbound on the 100 radial. If the aircraft must start to turn at 20DME, what constant bank will roll you out on the 100 radial?

My Delta gouge says it would be 14 degrees.

But, according to math, the gouge is wrong. The correct answer is just shy of 10 degrees. Is there a general rule of thumb?

 

[CaptBill]

Go with B. My dead reckoning skills say it's a little more than 22.5 and less than 028. 025 should just about do it. I'll punch it in the FMC tomorrow and see if I'm right. Maybe we can have a 15 minute point to point seminar at NJC. Sounds fun eh?

My trusty FMC said a 027 heading would get you there. I would think + or - 5 degrees would make any employer happy.

 

[TrustMeI'maPilot]

Serious question... If your RNAV drops out mid flight, and ATC gives you direct to some point in the sky that requires trigonometry on your part, can you even legally accept the clearance?

This seems to me like giving a /A plane direct a VOR outside the service area, legally you can't accept it right?

 

[BobDDuck]

Okay nerds.

Besides doing a bunch of trig to figure this one out, what do you think the correct answer is?

KTAS=300. Aircraft is going to teardrop outbound on the 060 radial and wants to roll inbound on the 100 radial. If the aircraft must start to turn at 20DME, what constant bank will roll you out on the 100 radial?

My Delta gouge says it would be 14 degrees.

But, according to math, the gouge is wrong. The correct answer is just shy of 10 degrees. Is there a general rule of thumb?

My estimating skills don't get it all the way through, but this is what I've got...

Basically, a turn from a point outbound on the 60* radial to a point inbound on the 100* radial is a 180* turn... kind of. The distance between radials at 60 DME is 1 mile, so the distance at 20 DME is 1/3nm. There are 40 radials between 60 and 100 so that gives you about 13 miles between the two points at 20 DME.

To find the distance you'd have to travel in the 360 degree turn with those two points you multiple 13 by pi which gives you about 40. Half of that (180 degree turn) is about 20. 20 miles at 300 knots takes 40 minutes. A standard rate turn (3*/sec) takes 1 minute to do 180 degrees so we are talking about a 1/4 standard rate turn (4 minutes instead of 1) which is .75*/sec.

To find bank angle for a given rate of turn involves solving for the tangent of bank angle and at that point I am lost.

 

[CaptBill]

Is it legal? I would think so, but it's not likely to happen. They (ATC) may ask if you can accept that clearance but most guys wouldn't accept it because frankly, most guys aren't that familiar with point to point navigation absent an FMC . If you don't have /E capabilities, they (ATC ) would likely give you a vector for where they want you to go. To answer your question directly, you can't accept a clearance that your aircraft doesn't have the capability of performing within acceptable standards. If you have the instruments and the know-how to manually navigate a point to point clearance, you can accept it. If you're not sure, don't accept the clearance. Don't ever be afraid to say unable or I can't accept that if you aren't comfortable doing so.

 

[juxtapilot]

My estimating skills don't get it all the way through, but this is what I've got...

Basically, a turn from a point outbound on the 60* radial to a point inbound on the 100* radial is a 180* turn... kind of. The distance between radials at 60 DME is 1 mile, so the distance at 20 DME is 1/3nm. There are 40 radials between 60 and 100 so that gives you about 13 miles between the two points at 20 DME.

To find the distance you'd have to travel in the 360 degree turn with those two points you multiple 13 by pi which gives you about 40. Half of that (180 degree turn) is about 20. 20 miles at 300 knots takes 40 minutes. A standard rate turn (3*/sec) takes 1 minute to do 180 degrees so we are talking about a 1/4 standard rate turn (4 minutes instead of 1) which is .75*/sec.

To find bank angle for a given rate of turn involves solving for the tangent of bank angle and at that point I am lost.

@charlie1017

This is a more simple explanation of your nonsense.

@BobDDuck You got about as far as I did... Neither of us can work at Delta.

 

[BobDDuck]

@BobDDuck You got about as far as I did... Neither of us can work at Delta.

We can both hold out for the "acquired not hired" tag still!

 

[ian]

Okay nerds.

Besides doing a bunch of trig to figure this one out, what do you think the correct answer is?

KTAS=300. Aircraft is going to teardrop outbound on the 060 radial and wants to roll inbound on the 100 radial. If the aircraft must start to turn at 20DME, what constant bank will roll you out on the 100 radial?

My Delta gouge says it would be 14 degrees.

But, according to math, the gouge is wrong. The correct answer is just shy of 10 degrees. Is there a general rule of thumb?

i've found a lot of the answers on the DL gouge are wrong....

 

[charlie1017]

Ha @juxtapilot ! You asked me to solve the problem, not solve it like a Delta genius!!! LOL. Either way I'm toast if I were to take that Delta test.

 

[Autothrust Blue]

Serious question... If your RNAV drops out mid flight, and ATC gives you direct to some point in the sky that requires trigonometry on your part, can you even legally accept the clearance?

This seems to me like giving a /A plane direct a VOR outside the service area, legally you can't accept it right?

Uh, with radar monitoring, "fly heading (___) and direct Volunteer when able" is perfectly legal.

Direct to a radial-DME fix, not so solid.

 

[juxtapilot]

Ha @juxtapilot ! You asked me to solve the problem, not solve it like a Delta genius!!! LOL. Either way I'm toast if I were to take that Delta test.

I swear if I get that question I'm going to make sure I have a bunch of equation sin/cos/tan BS on my scratch paper.

 

[Maurus]

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.

It is being used but only on a Delta test...


The Delta test ultimately isn't too bad as long as you put in some effort with your studying. I scored fairly high when I took the test as a result of my studying. Most questions are way more applicable than say the FAA's ATP written. They do throw in random questions like these buy I didn't find too any of them when I took the test.

With the lat and long question they seem to typically give you point nearly directly North and South with makes "60" rule work easily. Just might need to add a mile or two for the slight offset.