#instrument approach

[nocternalrandomness]

”Santa’s Approach Plate”

[rotorsexual]

What never gets old is a student's first exposure to the different types of instrument approaches when you fly IFR. Everybody reacts with a similar confusion and frustration that they have no choice but to accept.

You start them off gently by explaining that there are two categories of approaches - precision and nonprecision. The main difference between them is that a precision approach has lateral and vertical guidance and a nonprecision approach only has lateral guidance. Both types will get you lined up with the runway but how they get you down to land is different.

The precison approach has a glideslope indication that allows you to follow a constant descending path down to a minimum altitude, like going down a ramp. The nonprecision approach has you descending to a lower altitude as you pass each waypoint, like going down a staircase.

Easy enough, right? Then you list out the types of approaches in each category.

Precison approaches include: ILS, PAR, and GLS

Nonprecision approaches include: LNAV, LNAV/VNAV, LNAV+V, LPV, LP, LOC, VOR, SDF, LDA, NDB, ASR

Ok that looks a lot worse now. So then you start explaining each one like how a LNAV approach is just using your GPS to navigate laterally instead of using a ground based beacon. And LNAV/VNAV is the same thing except it gives you vertical guidance too. Thats when they slam on the brakes and say "I thought that was a nonprecision approach and so it doesn't have vertical guidance??" Yeah thats kind of a lie. A few of those do actually have vertical guidance but are still considered nonprecision.

So then they go on about why is that the rule in the first place if there's so many stupid exceptions, and all you can do is shrug and say yep get used to it now. And then the frustration just builds when they learn that an LPV approach can be as precise or even more than an ILS.

Eventually they make it through the five stages of grief and accept the reality. The FAA is just really slow to update things. And these GPS approaches that are very accurate and reliable nowadays are still held back from 25 year old legislation that didn't trust them back then.

The real answer for why some approaches are accepted as being precision vs nonprecision is actually down to the paperwork attached to each one.

[globalair]

A common skill for pilots is knowing how to properly brief an instrument approach. 

Read "How To Brief An Approach"