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You're Given A 'Descend Via' Clearance. How Low Can You Go?

It's a question you can be asked on your checkride. Find the lowest altitude you can fly to on a descend via clearance. It might sound simple, but there are a few 'gotchas' you should be aware of...

Live from the Flight Deck

Find The Lowest Crossing Altitude, And Don't Descend Below It

The question is: "What's the lowest altitude you can descend to when given a 'descend via' clearance?" You're given the following STAR chart to review (pictured below).

On the BEREE 1 Arrival into KDFW, the lowest published crossing restriction is a mandatory 11,000' crossing at DIETZ. The lowest crossing restriction is the lowest you can descend with a 'descend via' clearance, so in this example, you can't go lower than 11,000' without further instruction from ATC.

Notice there are two fixes after this, WHOOT and HEDMN. Between them, the Minimum En Route Altitude (MEA) is 4,000 feet and the Minimum Obstruction Clearance Altitude (MOCA) is 2,100 feet.

You cannot descend to these altitudes on a descend via clearance. If you haven't flown a lot of STARs yet (most instrument-rated pilots haven't), this is a common question that might trip you up. You must stop your descent at 11,000 feet at DIETZ and wait for a lower assigned altitude by ATC.

Of course, all of this goes out the window if you ever hear ATC say "descend via the XXXX Arrival, EXCEPT maintain XXXXX feet."

Understanding Runway Transitions

Here's where things get a little tricky. If you're flying the BEREE 1, it's hard to mess up your minimum altitude if you understand the difference between an MEA and a crossing restriction. But what happens when a STAR connects directly with a runway's instrument approach?

Take a look at Cleveland's BRWNZ 4 Arrival below. The last crossing restriction on the STAR for KCLE landing runways 24L/R is at LLROY: 5,000 feet and 210 knots.

Approach control might let you know to expect Runway 24L/R, but unless ATC clears you for the ILS to Runway 24L/R, you cannot descend below 5,000 feet. An "expect" runway assignment does not give you permission to descend.

Report: Crew Misunderstands A Runway Assignment For A Clearance To A Lower Altitude

It can get confusing when there's a mix of STARs, runway assignments, and instrument approach transition routes. We found the following NASA ASRS report and it's a good example of what happened to a crew flying into Atlanta:

On the STOWAL1 arrival into ATL. It is a complicated arrival that we are still working the bugs out of. We were cleared to descend via the STOWAL1 arrival except to maintain normal speed, 300 knots, then cross STOWL at 280 knots. The restriction at STOWL is 12000 feet and 280 knots. Between fix STOWL is STERN then ARMMY and the restriction at ARMMY is 280 knots and 12000 feet. We descended at 300 knots and the aircraft slowed to 280 knots as anticipated in managed speed, managed nav, managed descent. Between STOWL and STERN the aircraft slowed to nearly 260kts. I selected speed 280 knots.

We were discussing why this would happen when approach gave us a frequency change. We checked in and were told we were cleared via the STOWAL1 arrival runway 26R. I dialed the lower altitude of 2700 feet for the approach, after verifying the charted crossing restrictions of either 5000 feet or 4000 feet at the start of the approach. I mentioned to verify that we slowed to 250 knots since we were in selected speed below 10,000 feet.

The Captain said he thought our altitude should be 12,000 feet and I thought that when given a runway identifier it implies that you are cleared for the transition to that runway. We descended as low as 10,500 feet without proper clearance. My mistake was not resetting 12,000 feet and verifying our clearance with ATC since there was a question about our clearance. We were given a phone number to call after landing and spoke to the TRACON supervisor who discussed the arrival with us including ATC clearances and expected pilot actions. He told us he would not press pilot action, even though this nearly created a traffic conflict with aircraft climbing to 10,000 feet on departure.

Has This Happened To You?

If you're ever in doubt about a clearance, ask ATC for clarification. Until you're cleared to a lower altitude, or cleared on an instrument approach, you cannot leave the last crossing restriction of a STAR following a descend via clearance.

What airports have arrivals that make this confusing? Have you ever flown a STAR straight into an instrument approach? Tell us in the comments below.

Swayne Martin

Swayne is an editor at Boldmethod, certified flight instructor, and an Embraer 145 First Officer for a regional airline. He graduated as an aviation major from the University of North Dakota in 2018, holds a PIC Type Rating for Cessna Citation Jets (CE-525), and is a former pilot for Mokulele Airlines. He's the author of articles, quizzes and lists on Boldmethod every week. You can reach Swayne at swayne@boldmethod.com, and follow his flying adventures on his YouTube Channel.

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