I've been studying for my CPL written. While going through The Canadian Commercial Pilot Answer Guide 6th edition, I came across the following question (navigation):

215.
When flying north of the VOR, you have selected 090 degrees on the top of your OBS. The needle is centered, but there is no TO/FROM indication. If you turn your OBS to 100 degrees, what would the respective needle and flag indications be?
1. Right/"TO"
2. Right/"FROM"
3. Left/"FROM"
4. No change would show. Your VOR must be unserviceable.

The answer in the back 2. Right/"FROM", but I don't think this is right. In my opinion it should be 1. Right/"TO".
Have they made a mistake, or have I made an ass of myself for posting this?

Thanks.

I believe you are correct, Right with a TO indication.

Its "TO"

ETOPS wrote: Have they made a mistake, or have I made an ass of myself for posting this?

Thanks.

Neither! I think both previous posters are wrong, but asking does not make you an ass, it will make you understand something. I think very few questions can make someone an ass for asking so don't worry!

You are heading north, so at OBS 90 degrees, you VOR tells you nothing. When you put 100 degrees, the needle deflects to the right and there is a FROM indication. What are you doing exactly when intercepting that radial? You are either going to the VOR with a heading now of 280 (assuming no wind), and the needle will be deflected left when you actually need to go right, or you are going away from the VOR with a heading that is the same as the radial set on the OBS, and therefore the CDI will not be reversed.

I don' t know if my explanation was clear, not used to write that in english!

BTW, there are not a lot of mistakes in that practice book except in the theory of flight section, where they often confuse things like lateral stability and stability on the lateral axis (the later being stability in pitch, since it rotates around the lateral axis). There is also many questions where two choices are actually true, but one being maybe a bit more important...

There is no mistake. Its RIGHT AND TO.

Perhaps you don't know how a VOR works trampbike?

Perhaps, so would you explain it to me please?

EDIT: spelling

It is most definitely RIGHT and TO.

You can use this sim to help confirm things maybe
http://www.visi.com/~mim/nav/

So it would be a TO when on 0 degree radial, but as soon as you start turning right, it switches to a FROM.

Without going through technical stuff, the best way to do this is to draw it on a piece of paper.

Imagine a given radial (radials are always FROM the VOR) In the above case, draw a cross and label each end N E S & W.

Draw a little airplane north of the station (N). That would be your "N" on your OBS.

Assuming you select the 360 radial, look 89 degrees to your left and 89 degrees to your right. This is your FROM sector.

At 90 (E or W) in this case, you hit the Zone of Ambiguity. This zone is like a cone and gets larger as you get further from the station. This is why you don't get a TO/FROM because the receiver it not sure where you are.

Anything past that is a "TO" therefore if you select 100 (like in the question) it would indicate a "TO" and the CDI would show right because its telling you which way the new selected radial is.

I hope I didnt confuse anyone.

Thanks Tango. It's so much better to explain in a couple of sentence than just laughing at people eh?

I really thought about the question as "once I turn right, what will it show?", which was obviously not the question!

When flying north of the VOR, you have selected 090 degrees on the top of your OBS. The needle is centered, but there is no TO/FROM indication.

I agree this is a bullshit question, I understand the concept they are trying to test.. but the manner of the question is terrible.

Explain to me how you can be north of the VOR with an on course indication of 090 or 270? Im assuming the mag variance to be 0

The basic concept here is to be able to determine what qaudrant of the "range" you are in. its really a piece of cake however BS questions seemingly make it difficult.

Add to that the mistake in the book! At first when I did this question I had the "good" right/to answer, but I was forced to think as thought the question was intended to mean something a bit different since their answer was right/from!

You know, I learned something today...

There were a few questions that I got in some CPL study books that made me just sit there and redo them about 10 times, because I knew I was right, but the book was giving an incorrect answer. Either way, like Strega said, they're just horribly worded and designed questions for a concept that you likely know well, but can't figure out because someone was an idiot while writing it.

years ago, when I wrote my Inrat exam, I got up at the start of the "NAV"section and complained to the biddy at the front desk..

The whole nav portion of the exam was not a "LEGAL" flight,,,,

They had you flying on an HF airway, with only one ADF on board, and the MEA for the VHF airway was something like 17000 and you did not have O2 or a pressurized cabin. With only one ADF on board, you would not comply with the CAR that states you need to have navigational equipment on board that will allow you to still be able to navigate in the event of a failure.. (if you ever see an old navajo or chieftan that has 2 adfs installed, this is why)

Anyways the biddy had no idea what I was talking about and I just continued on with the BS....

TC's way I guess...

Without reading all the posts, the answer is RIGHT and TO.

As with any written exam question like this... draw a picture on the scrap paper they give you...

Thanks everyone. I was actually hoping that I was wrong and that the answer in the back was right. Now I've just lost faith in this answer guide.
Here is another question I have some doubts about (once again, its from the 6th edition):

275.
Station A is located 500 feet above sea level. The temperature is 33 degrees C and the dewpoint temperature is 23 degrees C. Convective clouds are forecast for late afternoon. If formed by air rising from the surface, at what height above MSL will these clouds be based?
1. 4000 feet
2. 3500 feet
3. 4500 feet
4. 7100 feet

The answer in the back is 3 (4500 feet), and I have no idea how they came to this number. I would think the base of the clouds should be somewhere around 3800 feet (or more exactly 3833 feet) above MSL. That's just using a DALR of -3 degrees/1000 feet.
Can you guys shed some light on this one?

I could very well be wrong with this. But dewpoint decreases about 0.5 degrees every 1000,' and we know the DALR is -3 degrees, therefore the two will give a decrease of approximately 2.5 deg per 1000.’

33-23=10
10/2.5=4

So, 4000agl or 4500asl.

AUGER9 wrote:But dewpoint decreases about 0.5 degrees every 1000,'

You are correct. the Temp/Dewpt spread decreases by 2.5 per 1000'.

In the FGU it says take the Temp/Dewpt spread and multiply by 400. This will give the base of convective clouds in height AGL.

In our case, 33 Temp - 23 Dewpt = 10.... 10 x 400 = 4000' AGL.
Answer is 4500 ASL.

Ahh, I missed the dewpoint drop.

Thanks!

I 'd like some more info here ...
About the VOR question ... how could the needle be centered on the 90deg radial if you're north of the VOR ?
I assume, being north of the VOR means NOT being on the 90deg radial or its reciprocal.
Wouldn't the needle centered and no to/from mean that the plane is actually right on top of the VOR ?
unless the no to/from indicator also means that the needle position is unreliable ?
Thx.

trampbike said

You know, I learned something today...

Not to answer questions you don't fully understand?

Here is a sim for those learning the VOR;

http://www.visi.com/~mim/nav/

Nope, I learned that when trying to explain something you partially understands, you understand it better afterward and others will help you understand even more.

I'm looking for help too on the Canadian Commercial Pilot Answer Guide Sixth Edition. Would anyone have the solution for question 195?

Question 195: A pilot en route to the Vancouver VORTAC via V342 and maintaining a heading of 248 degrees, tunes in the Abbotsford NDB and obtains a relative bearing of 220 degrees. He quickly tunes in the White Rock NDB and obtains a relative bearing of 310 degrees. Where is he?

a) Between ANTLR and COGLE.
b)Over the Langley airport.
c)To the right of track and between ANTLR and COGLE.
d)To the left of track and between SAFOL and COGLE.

I'm pretty sure the answer for #195 is correct (2. Over the Langley airport). You have to assume the heading of 248 is magnetic.

Your bearing to station (BTS) will be equal to your relative bearing plus your magnetic heading.
Abbotsford BTS-> 248 + 220 = 468 (minus 360 equals 108)
White Rock BTS -> 248 + 310 = 558 (198)
The bearing from station (BFS) is what you need to plot you location. BFS is the reciprocal (+-180) of the BTS.
Abbotsford BFS = 288
White Rock BFS = 018
So get a protractor out and draw the lines. They'll intersect more or less right over Langley.

Or you can just freestyle it with a protractor.
Center it over the NDB. Align North on the protractor with your magnetic heading (248), and draw a straight line from the relative bearing through the center to the opposite end (extending it past the center acts as the reciprocal BFS). Repeat for both stations and locate the intersection.

Probably a convoluted explanation but at least I tried. Hope you can get something out of it.