“Radar Required” on Approach Plates

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BeaconSlash@reddit

This gets *extremely* nuanced... I apologize in advance, but I just can't ELI5, and I haven't seen any replies discussing TERPS, so...

TL;DR - For modern GNSS equipped aircraft, "RADAR REQUIRED" is effectively obsolete and you can basically disregard it. Its roots are from the time before GPS.

I will dive in below:

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First, P/CG:

RADAR REQUIRED− A term displayed on charts and approach plates and included in FDC NOTAMs to alert pilots that segments of either an instrument approach procedure or a route are not navigable because of either the absence or unusability of a NAVAID. The pilot can expect to be provided radar navigational guidance while transiting segments labeled with this term.

But what's the origin of this? Let's look at FAA Order 8260.3G, TERPS (Terminal Instrument Procedures). Specifically, Paragraph 11-2-2 Radar Approaches - Feeder Routes and Initial Approach Segments:

a. Feeder and initial segments do not need to be established when navigation guidance and obstacle clearance are provided by ATC radar vectors during the transition from the en route to the terminal phase of flight.

Basically, because radar service was/is consistent available, and necessary ground-based navaid structure was/is lacking to create published routes from the airway structure to the published approach (e.g., feeder or Initial Approach Segments starting at an airway fix), the approach gets labeled as "RADAR REQUIRED".

Traditionally (before GPS) this meant ATC must vector you to join the approach course since, without appropriate VOR coverage, there was no way to get from the airway environment to a published approach otherwise. Nowadays, there are potential alternatives.

You might be cleared direct a fix on the approach if you're suitably equipped. ATC should keep you in radar contact until you are established on the instrument procedure per our rules. 7110.65 4-4-2 Route Structure Transitions (emphasis mine):

g. Clear RNAV aircraft between designated or established ATS routes via random RNAV routes to a NAVAID, waypoint, airport or fix on the new route. ***Provide radar monitoring to aircraft transitioning via random RNAV routes. ***

EXCEPTION. GNSS−equipped aircraft /G, /L, /S, and /V on point−to−point routes, or transitioning between two point−to−point routes via an impromptu route.

See though that ATC can even create a route out of thin air between two published RNAV waypoints. AKA - ATC can create route structure out of thin air now for GPS equipped aircraft. This effectively makes RADAR REQUIRED obsolete since ATC has the rules and means to legally separate you from traffic and terrain even out of radar coverage, and you have the ability to navigate laterally and vertically per their instructions until you hit the published approach.

In short... if you lack GPS, RADAR REQUIRED means you'll get vectors to final. If you have GPS, it'll probably be like any other approach.

I'm open to correction if someone knows better.

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randombrain@reddit

Excellent addition, I didn't know all that nuance but it makes sense.

Not to doubt your knowledge, but /u/kmac6821 is our charts guy and I find myself pinging him more and more these days.

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kmac6821@reddit

Thanks. I thought that was a good overview.

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kmac6821@reddit

I suppose the summary of what you said would be something like: A procedure designer has to get you from the enroute structure to the final approach course via ground-based NAVAIDs, radar vectors, or RNAV. For a conventional procedure, you need NAVAIDs or radar vectors. When a fix on a procedure cannot be identified and flown to using only conventional navigation, then radar is required to get you to where you can resume your own navigation.

The 8260.19 has several examples that drive the “radar required” note.

This also came up recently in something else, but for the life of me I cannot remember where that was (in the legend maybe?). If I remember I’ll edit this.

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Basic_Wishbone6605@reddit

ATC need equipment to make approach happen. We no worry as pilot if we get approval

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appenz@reddit

This is the correct answer.

But why it is on the plate? Usually, only stuff that pilots need to know should be on there. I guess if I heard that all radar if the NYC area was down, I would know that my radar-required approach into EWR is not happening. But diagnosing adequate radar coverage based on NOTAMs wasn't exactly on my PPC syllabus.

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bustervich@reddit

I don’t know if it’s still the case but I’ve seen a few times either late at night or early in the morning when approach is closed that center doesn’t have the detail on their radar screens to give vectors to final.

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TinCupChallace@reddit

Center (typically) needs to start you over an IAF unless the approach is depicted on our scope (we can toggle ILS on and off our scope). So expecting vectors to final from center for an RNAV isn't going to happen. It's also hard for center to vector you in nice and tight because our radar only updates once every 12 seconds instead of every second like approach has. So there's an art in vectoring because you need a buffer to account for the radar delay.

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Hour_Tour@reddit

Oh interesting, I had the vague impression that FAA had fusion or whatever (multi radar source and ads-b position) and updated the position more or less continuously, guess that's nowhere near true for everone.

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randombrain@reddit

Speaking to the Terminal environment, you are correct. We have multiple radars and we also have ADS-B. We don't see continuous updates because apparently when they did a focus group the controllers were wigged out by it, but we do have one-second updates.

For the Enroute guys, though, they still stick with 12-second updates. That was, and still is, the sweep rate of the long-range radar. Even when they're supported by ADS-B and/or terminal radar sites, they only get 12 seconds.

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Hour_Tour@reddit

Thanks

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TinCupChallace@reddit

I don't know a ton behind the scenes but I know that our scopes combine all of the sources and then display the result on our scope. We don't see the raw radar, we see what the combined product is programmed to show us.

That being said, we still only get 12 second updates (at center). I guess they figured it's been that way forever, why change it?

It takes time to get used to. You turn an aircraft and the first sweep might not pick up the turn, then you have to wait another 12 seconds before you see it. Altitude changes are always behind as well. Speed changes take 3-4 updates.

There's very little difference between adsb and non adsb equipped aircraft on the scope. It'll put a small red A next to your call sign if I select that option. Otherwise they look identical and update at the same frequency.

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Hour_Tour@reddit

Interesting, 12 seconds is wild to me. I have 4sec updates doing approach, but our backup is only 6 or 8 seconds and that feels absolutely terrible!

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Independent-Reveal86@reddit

You probably want to know whether a procedure will be available. If you look through the NOTAMs preflight and see the radar service is not available at your eta then you need to factor that in to which, if any, procedures you can use when you get there.

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__joel_t@reddit

It generally means there's no ground-based NAVAID to transition from the en-route to the approach, so it requires ATC to vector you, and that requires radar. Typically, if you have RNAV, that will act as a substitute to ATC radar vectors. RADAR REQUIRED is now being phased out of RNAV approaches because you will by definition have appropriate RNAV to transition to the approach.

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randombrain@reddit

Not fully true, or at least it would behoove you to be a little bit more careful than that.

In the general sense "[xyz] required" on an approach plate is just like any other notation on an approach plate, such as "procedure NA at night" for example. By that I mean it is the pilot's responsibility to ensure compliance, NOT the controller's responsibility. The 7110.65 is clear (4–8–1a Note 2) that ATC issues or withholds approach clearances based on traffic alone. Having a clearance for an approach is necessary but not sufficient for a pilot to execute that approach.

For example, if an approach is notated "DME required" and the DME is out of service, the pilot is responsible for either 1) making sure they understand and are compliant with the applicable GPS substitution rules or 2) rejecting the approach clearance.

"Radar required" is very slightly different because it's the ATC equipment that is required, and common sense tells us that ATC would know this and wouldn't issue the approach clearance if the radar wasn't working. But it's still in your best interest to make sure you were, in fact, issued "radar contact" at some point before starting the approach. Which you almost certainly were, these days.

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otterbarks@reddit

I’d assume ATC asking you to make position reports would also be a giveaway that you’re not getting radar services. ;)

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randombrain@reddit

You aren't wrong!

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DanThePilot_Mann@reddit

If you leave radar coverage should you always expect to hear “Radar services terminated” or “contact lost” of sort?

Only been flying for 6 years, so my experience with non radar environments is exclusive to operating in a non radar delta, or uncontrolled fields

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randombrain@reddit

Yes, that is correct... except for the exceptions, 7110.65 5–1–9b. Which is a terribly written list, right up there with 5–6–1 as one of the worst lists in the .65, but it's relatively straightforward aside from that.

The biggie is that when you get hit with "Change to advisory frequency approved" that always means radar service is terminated, because you aren't on our frequency any more so we can't provide you the advisories that make up "radar service."

Of course that will only happen after you've been cleared for the approach and established on the procedure. At that point radar is no longer required for the approach. See AIM 5–4–5a3(b), which does mention that "radar required" could also mean "radar required for the missed approach." You won't get that at non-towered airports, though, and I feel like it's pretty rare to see even at towered airports... usually the procedure is designed assuming non-radar.

PS, regarding the missed approach and radar procedures: No matter what the published missed says, if you're at a towered airport you can EXPECT to be given a heading and altitude rather than the published missed.

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LeftClosedTraffic@reddit

I love when ATC people come in and answer questions in such a detailed manner. Thank you!

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SATSewerTube@reddit

Pretty much just means ATC has to have you in radar contact for the approach.

Went somewhere a long time ago during an outage that occurred as we were entering the terminal environment. Got switched to airways, flew that to a DME arc, onto an ILS for different approach (Y vs Z or something like that) that didn’t have “RADAR REQUIRED” on it, and made all the required no radar calls.

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Vessbot@reddit

It's about the later seasons of MASH.

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DanThePilot_Mann@reddit

Gotta have your Wx radar turned on

/s

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ps2sunvalley@reddit

Having radar required on all plates at a field went into the calculation of whether you need an alternate or not even in good weather.

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Ok_Witness179@reddit

This was definitely one of my favorite questions when giving instrument stage checks. People would come up with all sorts of fun lmy theories lol. I'm just like "...seems like potentially an important thing to understand before we shoot this approach?", and they're just like "yeah, probably so" 🤣

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Pseudo-Jonathan@reddit

Usually it's because there is no way to navigate from the en route structure (a.k.a. airways) to any initial approach fix (IAF) without a controllers assistance. If the controller has no radar, he won't be able to get you there legally

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mflboys@reddit

Yeah one that I’m familiar with is an ILS with no pt/hilpt depicted. The only way to join would be VTF or direct the IF, which is a loc/vor intersection. But in our rules, if we clear you via the IF, we have to monitor you on radar until you’re established.

So no way to do it without radar.

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