Flying
IFR, Lesson 4
Enroute
The enroute part of IFR flying isn't tremendously complicated.We'll be spending most of our time tracking airways and intercepting new ones. Occasionally we'll be handed off to a new Center controller and in rare circumstances, we'll be asked to hold. Let's first talk about airways tracking As we learned before,
airways are simply imaginary paths which are based on
radials to and from VORs. We try to fly as directly as
possible, but VORs aren't always going to be in straight
lines between where we're starting from and where we're
going. So, we're going to have to piece together the
airways which will take us to our destination. Along the
way, we'll have to be diligent to maintain our course and
be aware of when our next changeover I is coming. Now,
airways are protected 4NM either side of the centerline,
so we have a little room to play with before getting
ourselves into danger of obstruction interference, but
that doesn't mean we should get sloppy with our tracking
skills. So, let's take a look at a sample flight from
Vero Beach to West Palm Beach International(PBI) We'll assume that, like our ``Departures" example, we've gotten radar vectors to join our assigned course. Now we're established on V159 and we're tuning our radios to intercept V531. We know that TBIRD is 31DME from VRB, so we don't actually need a second NAV radio to define TBIRD. We could simply fly until 31DME, switch to the Palm Beach VOR frequency, tune the new radial, and turn on course. But, for the sake of backup and practice, we'll also use dual NAVs to fly our courses. So, established on V159, we're proceeding along course with NAV2 set to VRB radial 182 FROM. We've set NAV1 to PBI radial 147 TO(reciprocal of 347 FROM).
Once the needle on NAV1 centers and the DE(set to NAV2) reads 31, we know that we've reached TBIRD. At that point, we'll turn to track NAV1 and continue inbound towards PBI. Also, at this point, we need to start our descent down to 3000ft. ATC expects that we know the rules and will be expecting us to make our descent. However, we still need clearance to vacate any assigned altitude. So, we could call Center and ask for clearance, something like ``Miami 9246F would like a descent to 3000" to which they would reply ``9246F descend and maintain 3000ft". We would then report leaving 4000 for 3000.
I should also note that any ATC clearance supercedes the course/altitude rule. If ATC tells us to maintain 4000ft, even though we're now on a magnetic course that dictates we fly odd thousands, we do it. Now that we're established on V531, I'd begin the arrival procedure which we will discuss in the next lesson. I'd set NAV2 to the ILS frequency in preparation for the approach and continue inbound.
So that's about all there is to enroute flying. I've decided not to discuss holding procedures at this point. The reasons for this are first because we aren't asked to hold in X-Plane. Second, understanding holds is very difficult without proper visual aids. Holding itself is quite simple, but visualizing how to enter and maintain a hold is difficult for the beginner and it's not at all uncommon for someone to bust an instrument ride due to poor holding. So, I will work on creating some better visual aids to facilitate understanding of my discussion and I will present holding at a later time. Thanks and enjoy! © 1999 - AVSIM
Online and Andrew Ayers |
Near
the top, you'll see Vero Beach. West Palm Beach is off
the chart to the southeast. If you look at ``D",
you'll see that it says ``Palm Beach 115.7". This
indicates that the airways which are going off the map at
this point are based on the Palm Beach VOR(which is on
the field at PBI). So, if you look back up at Vero Beach,
you'll see that V3 runs in a straight line directly from
the Vero Beach VOR to the Palm Beach VOR. This seems like
the logical choice for us to use then right? Well, sure
it is, but you're not getting it. Unless you're flying
high, there's too much VFR traffic coming up and down the
coast in that area, so ATC isn't going to want to keep
and eye out for you the whole time. Instead they'll bring
you out and then back in when you get near Palm Beach.
So, let's assume that we were given this clearance:
``9246F is cleared to the West Palm Beach International
airport via Victor 159 TBIRD Victor 531..." So,
looking on our chart at ``A", we see that V159
extends south along the 182 radial FROM Vero Beach. At
31DME, it passes through TBIRD intersection(``B").
From there, we see that V531(``C") extends southeast
bound 35DME to the Palm Beach VOR via radial 327 FROM.
Alright, now that we know how we're supposed to proceed
to PBI, let's talk a bit about altitudes. You'll remember
that going on a magnetic course of 180-359 degrees, we've
got to fly even thousand feet intervals. VOR radials are
magnetic, so along V159, we're going to be going on a
magnetic course of 182 degrees. We see that the MEA along
that segment of V159 is 2500ft, so we'll have to go at
least 4000ft. That'll be fine for us, so we'll plan on
that. However, once we cross TBIRD, we'll be proceeding
along a magnetic course of 147 degrees(the reciprocal of
327 FROM). So, now we've got to fly an odd thousand foot
altitude. The MEA along this segment of V531 is 3000ft,
which will work fine for us, so we'll plan to make a
descent to 3000ft after passing TBIRD. This brings me to
an important point which applies more to climbs, but also
to descents. If you are proceeding along an airway and
you're about to cross into a section with an MEA higher
than your present altitude, you are expected to start
your climb to your new altitude UPON crossing into that
segment. Some intersections have Minimum Crossing
Altitudes(MCAs) which indicates that you should climb to
the higher altitude BEFORE crossing into the new segment.
You'll see an ``X" with an altitude by it at those
intersections, but they're not all that common. OK, let's
go flying!
