Approach plate briefing

[cnumb]

Gday, please help with reading profile view correctly and with calculations of my descent say from 3000 feet, what distance to start descending to shoot the approach correctly.

Thanks

http://imagizer.imageshack.us/v2/xq90/43/o3pc.png (https://imageshack.com/i/17o3pcp)

[jamesleaman]

If you've got a desired airspeed and Vertical Speed then this is quite a simple thing to work out.

Just use S = D/T and some simple conversions.

Say your at 3000ft, you want to be at 1800ft by the start of approach.

That's 1200ft to descend. If you do 200ft per minute you'll reach 1800ft after 9 Minutes.

Distance = Speed x Time

Let' say your speed is 80knots. Convert your knots into mph by multiplying it by 1.15 (to two decimal place)

80knots x 1.15 = 92mph

Distance = (92MPH x 9Minutes)/60

Distance = 13.8NM

Therefore at 13.8NM from the start of your approach starting descending at a vertical speed of 200ft per minute.

[GClooney]

What has your instructor taught you? If you're in training, it's not the most straightforward I've seen. Jepp is much easier to read if you have access with pre-calculated target vertical speeds for different ground speeds.

[MarkerInbound]

You'll notice there is a requirement to remain within 10 miles of LAKAN intersection. Two hundred feet per minute could, in theory, get you killed.

From the FAA Instrument Procedure Handbook:

For short runways, arriving at the MDA at the MAP when the MAP is located at the threshold may require a missed approach for some airplanes. For nonprecision approaches a descent rate should be used that will ensure that the airplane reaches the MDA at a distance from the threshold that will allow landing in the touch- down zone. On many IAPs this distance will be anno- tated by a VDP. To determine the required rate of descent, subtract the TDZE from the FAF altitude and divide this by the time inbound. For example if the FAF altitude is 2,000 feet MSL, the TDZE is 400 feet MSL and the time inbound is two minutes, an 800 FPM rate of descent should be used. To verify the airplane is on an approximate 3°glide- path, use a calculation of “300-foot-to 1 NM.” The glidepath height above TDZE is calculated by multi- plying the NM distance from the threshold by 300. For example, at 10 NM the aircraft should be 3,000 feet above the TDZE, at 5 NM 1,500 feet, at 2 NM 600 feet, at 1.5 NM 450 feet, etc., until a safe landing can be made. In the above example the aircraft should arrive at the MDA (800 feet MSL) approximately 1.3 NM from the threshold and in a position to land in the touchdown zone.

[Tinstaafl]

Like Marker indicated: It's near-as-dammit a 3 deg profile which equates to 300'/nm. Add 300' for each mile away from the the threshold (but comply with any specified minimum/required altitudes during the approach.

For the descent rate use Groundspeed x 5** = ROD.

eg GS on approach = 120kts so target ROD = 600'/min.


**some find it easier to do the maths mentally by using 'half the GS then tag on a 0'. eg 140 kt --> 70. Append a '0' --> 700'/min.

[Cobalt]

This is a tricky one because of the 1,800ft altitude, which is above the 1,500ft altitude at the FAF.


To answer your question


1) How to read the profile view


This has three descent segments
- once you are outbound from LAKAN, you can descend to 1,800ft.
- once established on the inbound track (after the procedure turn), you can then descend to 1,500ft
- once back at LAKAN, you can then descend to the MDA


2) How to fly this in practice


Assuming you are in a light aircraft, and unless you have a lot of time to prepare, here is how to best fly this:


- leaving LAKAN, start your descend to 1,800ft and start the procedure turn; don't wait too long to start your turn otherwise you will bust the 10NM procedure turn limit. I would like a CAT D aircraft try that, btw...
- the procedure turn should take approx. 2 minutes, so 500 feet per minute should see you at or above 1,800 ft when inbound
- continue your descend to 1,500ft, LEVEL OFF
- fly to LAKAN, the FAF, at 1,500ft
- then [as tinstaafl said] fly the approach from the FAF down as you would fly any 3 degree approach, ie., take the ground speed (from the DME) GS x 5 and make that your rate of descent in fpm.

[Tinstaafl]

I should add that my description was for a constant descent method. You may prefer 'dive & drive' ie expedite descent to each altitude limit then level flight until the next descent (or missed approach) point. By expedite, I mean something greater than the GSx5 ROD, generally never more than 1000'/min, and a good idea to be rather less than that when below 1000'.

But frankly, with a DME or equivalent distance, you're better off just adding 300' for each nm from the threshold and aiming to hit that height at each mile mark, using the GSx5 guide + or - a bit for corrections.

[GClooney]

I should add that my description was for a constant descent method. You may prefer 'dive & drive' ie expedite descent to each altitude limit then level flight until the next descent (or missed approach) point. By expedite, I mean something greater than the GSx5 ROD, generally never more than 1000'/min, and a good idea to be rather less than that when below 1000'.
Except it's asking for a 2.94 degree profile after the FAF...again, speak to your instructor..

[Tinstaafl]

It's a non precision approach so it lacks GS guidance. How you get down is your own affair as long as limits are complied with. The profile design is close enough to 3 degrees for GSx5 & 300'/nm and similar guides. 'Dive & drive is also an accepted method.

[cnumb]

Thanks all for your inputs, appreciate it!

I just started instruments training and non precision approaches are not coming easy to me. I'll review all posts and I'm sure the picture will become clearer.