Struggling with a question

[giladal]

Hi Guys,

Wondering if anyone here can help me figure out this problem. I dont know what the formula is to figure out height below gs when considering dot deviation.

-- Question --
An aircraft is on an ILS approach and indicated half full scale deflection on the glide slope, giving a fly up indication. At 2.2NM range from the threshold there is an obstruction of 285ft above the threshold level. What will be the vertical clearance from the obstacle when the aircraft passes over it on a 3 degree glide slope?

Looking forward to hearing from you,
CG

[optimus.Prime]

Well the basic formula is Ht = (Distance * 6080 * G/S) / 60.

Btw, is the answer 305 ft of clearance?

[giladal]

Thanks for the info. Actually the answer is 380ft. You were close

How do i figure the GS in your equation?

[optimus.Prime]

Well thats quite puzzling since if you substitute the correct values in the formula :

Ht = 2.2 * 6080 * (3-0.35) / 60
= 590 ft

Ht of obstruction is 285 ft.
Hence , the clearance would be 590-285 = 305 ft.

Wonder how the answer would be given as 380 ft.?

[giladal]

Ah.. i think i found what the problem is. you are not including the 1/2 scale low gs indication in your formula right?

Never mind, you did.. 0.35 .. hmm

[Foghorn Leghorn]

The question is poorly written. It is asking what the height will be when you are on the G/S of 3deg. The first part of the question about the G/S and fly up command is irrelevant. Using the figure of 3deg gives an answer of approx 380ft.

[giladal]

I reread it. You are right. The full scale deflection is irrelevant as it asks "what will be the vertical clearance from the obstacle when the aircraft passes over it on a 3 degree gs".

Thank you all.

While I am at it. Here is another problem i am having a hard time to solve.

IAS reads 150Kias, position error is +6kts, instrument error is +8kts, FL150 (SAT = -15C. What is the TAS?
My answer is : 203.3 but its in correct.
I just added the errors to the IAS and then plugged in the PAL of 15,000, Temp of -15c and CAS of 164 and got 203.3.

Is there something I am doing wrong?

[ayush konisetty]

My answer came out to be 197kts

Heres how i did it..

IAS is already corrected for instrument errors so i added only 6kts to IAS to get CAS/RAS which i further substituted in the following formula to get TAS.

TAS = CAS/RAS + (1.75% of CAS/RAS per 1000ft)

[giladal]

hi

Sorry to disappoint, but the answer they give as right is 205Ktas...

I sent you A PM..

Gil

[Wenth]

instrumentation question

Hey Guys,

I didn't want to open a new topic for this, so let me ask a question here:

A pilot wishes to turn left on to a northerly heading with 10° bank at a latitude of 50° North. Using a direct reading compass, in order to achieve this he must stop the turn on an approximate heading of: (???)

In the AviationExam.com database the correct answer was 30°, but I've done some research on the net and it ended up by getting different correct answers (like 15°e.g.)...

So, my question is, to get is straight finally, what is the correct method to determine your approximate heading to roll the plane out?

Thanks in advance for your help!

[Lightning Mate]

Seemples.

When turning through the nearest pole role out 30 degrees early.

When turning through the furthest pole role out 20 degrees late.

This is all-inclusive for acceleration error and liquid swirl at mid latitudes and rate 1, as supplied by France who originally set the questions.