Anyone got an answer?

[deano14]

Ok - I keep getting asked awkward (well at least for me) questions by my CFI:

Who can tell me how you figure this one out?
You stand on the beach looking out to sea; you're 6' tall and you can see the horizon which, due to the curvature of the earth is a distance of 12nm away. If you now stood on a hill (or were flying) and were 1,000' AMSL looking out to sea, how far away would the horizon be?

I must be thick cause I don't even know where to begin with this one. HELP! (please)

[Hompy]

try this

Try this link.

http://www-istp.gsfc.nasa.gov/stargaze/Shorizon.htm

Isn't Rotorheads great?!

Hmp

http://www.maths.eril.net/1.05%20PythagProbs.pdf

[Sir HC]

Deano, Tell him that you would only be able to see as far as the visibility would allow. If that doesn't work, I calculated 33.64 Nautical Miles. Then again, my maths was never that good.

[MD900 Explorer]

Visibilty question

deano14

Only as far as the visabilty allows on the day

Sir HC



MD

[Winnie]

On radio range it is 1.23 x Square root of your altitude (height)

On visibility I think it is 1.20 x Square root of your Altitude (Height) if I remember correctly from my theory books.

[pa42]

next time you're in the flatlands . . .

At Bonneville Salt Flats (Great Salt Lake, Utah) one can stand on the Interstate and look east at the endless row of telephone poles gradually shortening with distance around the Earth. Last one disappears about 30 miles out (or so I used to teach it) if visibility is good enough (that is, nearly every day).

That's 6' of you and 45' of pole, the math gets daunting. Want more? Go to a coffee shop near your favorite university, look around for a female math major, offer her a coffee for a brief expansion. Soon you'll be involved in interesting research other than mathematical . . .

OR: Any text on the (sadly) obsolete art of celestial navigation will have correction tables for "dip." (But then you'd have to convert the angular-error-to-the-horizon into feet-of-height. Hey, are you still awake out there? Wake up!)

[SASless]

Sounds to me like a CFI is overly impressed with himself....and that question definitely falls into the catagory of.....Who gives a rats hind end!

But then while doing the UK ATPL I discovered there were loads of questions like that.....nifty info for those foggy mornings when the crew room was chock a block with tea drinkers waiting for the duty time window to run out....but having no merit other than that.

[Gainesy]

...as a drill instructor said (shouted) to/at me in basic:

"You see the horizon boy?"
"Yes Corporal".
"Well go and f***in sit on it!"

[sycamore]

D(nm) =1.05 x(sq.rt) H(feet)
from Vol 1 Radio Aids.......

[Ascend Charlie]

To get revenge on your instructor, point to the old wind-up clock on the panel and ask him:

"How long will an 8-day clock go without winding?"

He replies "8 days" and your response is:

"It doesn't go at all if you don't wind it!"

and then run for cover.

[Gaseous]

Deano,

I must be missing something. I dont know the answer to this and I think I am a fairly experienced and competent helicopter pilot.

I do not think that if I knew the answer I would be a better pilot.

This is the sort of crap that the CAA, smartarse instructors and examiners love but is fundamentally useless. These people piss me off.

I think that is controversial enough.

[Winnie]

Sycamore: you're correct (I was wrong, but then again I am a lousy instructor... )

Ascend Charlie: You had me in stitches, if my student did that, I'd roll of the seat laughing, and have to send him solo, for not being able to fly!

[deano14]

So....thanks for the replies guys. You blokes crack me up! I'm an instructor too but have never come across this one before. I agree that the whole exercise seems to have no value still, I try to please and if I can some up with some sort of half-baked answer then all the better - at least I've tried. As to the value of questions like this, I too wonder. Maybe you're right that the CFI just thinks too much of himself and wants to show how much better he is than little old me. Who knows. He's got decades more experience than I do so I just accept what he says and ask you blokes for advice now again. Hope that's ok with you!

Thanks to all who replied.

Regards.....

[Arm out the window]

You only have to use a bit of imagination to see how it could be useful.
For example, instructor teaching students medium level nav - "How far's that lake away?"
"No idea"
"OK, roughly how far's the horizon away from you at this height?"
"ummm...about 30 miles?"
"Close enough. OK, if the horizon is 30 miles away, how far's the lake?"
"About 10 miles?"
"Good enough for a start point; can you find it on the map"....etc etc

[Gordy]

As for the question of whether the original question had value----It got students thinking and got their heads in the book!!!!
Also can be helpful to figure out radio range, ie Why wont' the tower answer me? As a rough guide
1600ft will get you 50nm radio range
6500ft will get you 100nm radio range

[ShyTorque]

The answer is 45.235019875 nm.

Approximately.

[Whirlybird]

Hmmm....

I've had more experienced instructors try to show me how much more knowledge they had than I do...not difficult, since I have the world's worst memory. I could have answered deano14s question when I was doing my CPL exams, but not now. And yes, ultimately I suppose all knowledge could be useful for students.

OHOH, I've had a 10,000 hour instructor who doesn't need to prove how great he is give me advice on better ways to teach hovering, how to give students confidence that it IS possible when they're at the point that they know they'll never hover in a million years. Or various ways students might kill you that you hadn't thought of, and what to do about it.

And I know which kind of CFI I'd rather have imparting his knowledge to me on a rainy non-flying day.