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Chart Exercise – Departure: Setting the Radios

Departure procedures can often involve changing radios and radials several times in less than 10 minutes. Setting up the GPS and radios in advance can make the process much easier. I’m still learning so I like to write out the entire departure procedure and think through what happens at each altitude and turn.

If you have two radios, it’s even easier. Set the top radio up as the one to use for contacting the airport tower/CTAF and ground. If you are using a GPS for the first radio, these frequencies are easy to find and load from the database. The VOR should be set to the course to be flown. Set the bottom radio up for en route. The VOR on the bottom radio should be set to the radial that defines the first intersection.

The KSBP CREPE3.PRB departure is fairly straightforward so we’ll start with that. The NACO chart is below. Click on it for a larger version or here for a printable PDF version. Note that we’ve already covered the departure minimums here.

CREPE3 Departure

The departure uses the localizer for the initial climb out. Set the first radio to 109.7 and the OBS to 290°. Because it is a localizer, the OBS setting has no effect, but it is a good habit to always set the course index when using the CDI. We can identify it on the ground.

We need the second radio to identify CREPE. Set it to 114.3 and put 196° at the top of the CDI. We can’t identify it on the ground, so turn the volume on just a little so we’ll hear it when it comes in. The VOR is on our right so the needle will start on the right and move to the center. We can estimate when it will come alive by knowing that each dot on the CDI is 2° so full scale deflection is 10°, possibly 12° when the needle starts moving to the center. The CDI measures angular deviation, so the farther from the VOR you are the greater the distance from the course.

Lateral Course Deviation
by Distance from the VOR
Distance from VOR Dots Lateral Distance
1 nm   1 dot   200 feet
2 nm   1 dot   400 feet
30 nm   1 dot   1 nm
60 nm   1 dot   2 nm
Full Deflection
1 nm   5 dots  1,000 feet
2 nm   5 dots  2,000 feet
30 nm   5 dots  5 nm
60 nm   5 dots  10 nm
Full Deflection – Miles
6 nm   5 dots  1 nm
12 nm   5 dots  2 nm
18 nm   5 dots  3 nm
24 nm   5 dots  4 nm

CREPE is 22 nm from PRB. We are not approaching it on a DME arc, so the distance from PRB to our track is greater than 22 nm and decreasing as we get closer to CREPE. From the chart above we see that we the needle should start to move about 4 nm from CREPE. At 120 kts, this is about 2 minutes. From the table above, we can see that full deflection follows about a 6:1 rule, while 1 dot deflection follows a 30:1 rule.

For CREPE3.PRB we make a right turn as the needle hits the outer edge of the center ring of the CDI. We are on the 196° radial and we’ll fly a heading of 016° TO the VOR so we want 016 at the top of the #1 OBS. So before we leave the ground, we want to set PRB in the standby position. After we make the turn, ident the VOR and do the 5 T’s—Turn, Time, Twist, Throttle, Talk. Since we don’t have any information on the next leg, there is nothing to guide us on selecting the standby position for the #2 VOR.

CREPE3.MQO gets a little more complicated, but not much. Set the radios up as before. Now when we get to CREPE we turn left, and fly outbound on the 196° radial. The #2 VOR is already set and identified, and we are only flying 5 nm so if we fly the #2 radio and have MQO in standby on #1, it will simplify the workload. Identify MQO and put the radial we are intercepting at the top of the CDI, with a FROM indication. The VOR is on our left, so the needle will move from left to right. We are only 8-10 miles from the VOR so full scale deflection is about 1.3 nm. We’ll only have about 40 seconds while the needle goes from full scale to centered. (At 120 kts – maybe less time if we are out of our climb and flying at cruise speed.) Turn and twist the OBS to to 090° TO.

CREPE3.FRAMS is set up about the same way as CREPE3.PRB. Set the radios up the same as CREPE3.PRB. Now when we get to CREPE we twist the OBS to 204°. The needle should be just to the left of the fourth dot. When the needle hits the outer edge of the circle, turn left, and fly outbound on the 204° radial. Fly the #2 VOR for 2 nm. If MQO is in standby on #1, it will simplify the workload. Identify MQO and put the radial we are intercepting (292°) at the top of the CDI, with a FROM indication. The VOR is on our left, so the needle will move from left to right. We are only 11-12 miles from the VOR so full scale deflection is about 2 nm. We’ll only have about 60 seconds while the needle goes from full scale to centered. (At 120 kts – maybe less time if we are out of our climb and flying at cruise speed.) Turn and track outbound on the 292° radial.

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