CFII

SFCC/UND

Well-Known Member
Is there some sort of secret FAA IFR book somewhere. I finished my oral for my CFII and I had three FAA guys sitting in. Two of them were OJT and the other one has over 40 years of experience. One of the OJT was quizzing me, while the other two were taking notes. After we were done the senior dude pulled me aside and said that I were lucky because he would of failed me on everything I said because of my knowledge, not lack of teaching. I asked him I got all my information from the AIM and twenty other FAA books. Told me something about the GPS that it has to be within a nanosecond and if one second off you would be 178,000 miles off course, I think, but he still haven't answer my question. Any good ideas.
 

SteveC

Really?
Staff member
...I said because of my knowledge, not lack of teaching. I asked him I got all my information from the AIM and twenty other FAA books. Told me something about the GPS that it has to be within a nanosecond and if one second off you would be 178,000 miles off course, I think, but he still haven't answer my question. Any good ideas.
Slow down a little. Try asking that (those?) questions again with a little more explanation and we'll see if we can help.

:)
 

tgrayson

New Member
he would of failed me on everything I said because of my knowledge, not lack of teaching. I asked him I got all my information from the AIM and twenty other FAA books.
Without hearing the questions and your verbatim answers, it's impossible to judge whether the inspector's criticism has any merit or not. The thing about the nanosecond is silly.

Depending on how interested you are in his criticisms, you might consider setting up a meeting with him to discuss what he considers to be knowledge deficits. I'm not particularly recommending that, but the value of it would depend on how "safe" the inspector is.

Also: I'm skeptical that the senior guy would have failed you. The reason is that your passing was up to him in the first place. He was there to evaluate the OJT guys and could have overridden any decision they made.
 

SFCC/UND

Well-Known Member
I understand the 24 satellites and the CDI 1NM departure, 5nm en route, within 30nm of FAWP 1nm, and then 2nm from fawp it becomes .3nm. But then he asks me the accuracy of the GPS itself, I think he told me 30 meters or 10 feet can't remember, also then starts asking me about what will you see on the GPS when you are 2nm from FAWP and the RAIM is not working, now I know that it will show approach on the gps. That where talks about the nanosecond. It hard for me because I haven't flown with GPS yet and I'm not an expert, I just go by what the book tells me.
 

tgrayson

New Member
But then he asks me the accuracy of the GPS itself, I think he told me 30 meters or 10 feet can't remember, also then starts asking me about what will you see on the GPS when you are 2nm from FAWP and the RAIM is not working, now I know that it will show approach on the gps. That where talks about the nanosecond. It hard for me because I haven't flown with GPS yet and I'm not an expert, I just go by what the book tells me.
You said that "he would of failed me on everything", but you're only mentioning the GPS stuff. Is it only on this subject on which he criticized you?
 

SFCC/UND

Well-Known Member
There some small issues on other items, but it wasn't that bad, on some things he wanted me to describe a little bit more. It was mostly the GPS that he had a problem with. Tell you the truth I just wanted to go flying instead of doing the oral!!! It hard enough trying to teach three FAA how to fly on instruments.
 

tgrayson

New Member
It hard enough trying to teach three FAA how to fly on instruments.
I'm very sure that it is. You must have done just fine, in spite of the criticism you received. Remember that those asking questions always seem very knowledgeable because they know the answers to the questions they ask. I'd bet you could ask them a lot of questions they didn't know the answers to. But it might not hurt to spend a bit more time mastering the GPS stuff anyway. ;)
 

Douglas

Old School KSUX
But then he asks me the accuracy of the GPS itself, I think he told me 30 meters or 10 feet can't remember, also then starts asking me about what will you see on the GPS when you are 2nm from FAWP and the RAIM is not working, now I know that it will show approach on the gps. That where talks about the nanosecond. It hard for me because I haven't flown with GPS yet and I'm not an expert, I just go by what the book tells me.
If you don't have RAIM, you will get an alert.
Accuracy - for GPS (95% of the time) is 110 feet, WAAS enabled GPS is 10 feet. (for comparison, and VOR is a rough 475 feet.

AOPA has an excellent interactive course on this.
http://flash.aopa.org/asf/gps_ifr/swf/flash.cfm?

Shake it off. :bandit:

Edit: why did you decide to do your II at the FSDO? Is this your initial?
 

SFCC/UND

Well-Known Member
No this is my second. The DPE I used before was busy with charter work and I didn't feel like waiting and paying three hundred dollars. But I might go to the DPE to do my flight, since my examiner who did my oral will be out of town for awhile on a secret FAA mission. A funny thought the senior guy did my initial and said I did a good job for my CFI and no bad comments, but I guess maybe he was on his period, who knows. Since I passed the oral I'm happy.
 

T56Maniac

Member
What are you basing that on? The error is bigger the further away from the VOR you are.
Read from the AOPA web site:

"475 feet within 1nm from the station and 9,500 when 20 miles away from the station."

Guess this is the 60:1 rule of thumb??
 

tgrayson

New Member
Read from the AOPA web site:

"475 feet within 1nm from the station and 9,500 when 20 miles away from the station." Guess this is the 60:1 rule of thumb??
That makes more sense. Let's see, the circumference of a circle is Pi*diameter, = 3.14 * 2 nm = 6.28 nm. In feet, that's 6.28 * 6076 ft/nm = 38157.28 ft. So every degree is worth 38157.28/360 = 106 ft.

Now, Wikipedia says that >99% of the time, the VOR error is less than .35 degrees, meaning an error less than 106 ft * .35 = 37.1 feet. That isn't taking into account any sort of error in your VOR receiver, which can be off by 4-6 degrees, even when it's within tolerances.

Does AOPA say how they came up with that number?
 

T56Maniac

Member
That makes more sense. Let's see, the circumference of a circle is Pi*diameter, = 3.14 * 2 nm = 6.28 nm. In feet, that's 6.28 * 6076 ft/nm = 38157.28 ft. So every degree is worth 38157.28/360 = 106 ft.

Now, Wikipedia says that >99% of the time, the VOR error is less than .35 degrees, meaning an error less than 106 ft * .35 = 37.1 feet. That isn't taking into account any sort of error in your VOR receiver, which can be off by 4-6 degrees, even when it's within tolerances.

Does AOPA say how they came up with that number?
No. It's just a statement with no reference. But I like your thought process above. I have to admit, I'm a "brick" at math :(
 

tgrayson

New Member
No. It's just a statement with no reference. But I like your thought process above. I have to admit, I'm a "brick" at math :(
The IPH says this:

The navigation system information includes navigation facility radial alignment displacement, transmitter monitor tolerance, and receiver accuracy. All of these factors were considered during development of en route criteria. From this analysis, the computations resulted in a total system accuracy of ±4.5° 95 percent of the time and ±6.7° 99 percent of the time.

So if we use the 4.5° figure and my 106 ft/ degree, we get 4.5 * 106 = 477, which is pretty close to the 475. And I rounded by 106 number up slightly.
 

braunpilot

What day is it?
Guess this is the 60:1 rule of thumb??
I know this is the quick rule of thumb but does anyone know where to find this information? Is there any reference to this anywhere so that I could point this out to a student. Other than talking about the computations resulted in a total system accuracy of ±4.5° 95 percent of the time and ±6.7° 99 percent of the time.

Just wondering? Thanks
 

tgrayson

New Member
I know this is the quick rule of thumb but does anyone know where to find this information? Is there any reference to this anywhere so that I could point this out to a student. Other than talking about the computations resulted in a total system accuracy of±4.5° 95 percent of the time and ±6.7° 99 percent of the time.

Just wondering? Thanks
What exactly is your question?
 
Top