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Flight Training Instruction - Cnatra - U.S. Navy

Flight Training Instruction - Cnatra - U.S. Navy

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T-6B PRIMARY INSTRUMENT NAVIGATION CHAPTER SIX<br />

DME/Radial Rate of Change<br />

1. When the needle is closer to the heading index than the 90º benchmark, i.e., above the 45º<br />

benchmark, the DME will change faster than the radials. The opposite is true when the needle is<br />

nearer the 90º benchmark, i.e., when the needle is below the 45º benchmark.<br />

2. Remember, when the head of the needle is above the 90º benchmark, the DME will get<br />

smaller. When the head of the needle is below the 90º benchmark, the DME will get larger. The<br />

only exception to this rule is in the case of strong winds.<br />

3. To get DME to “speed up,” turn to place the needle closer to the heading index. This will<br />

slow the rate at which the aircraft is crossing radials. When going inbound, you will be working<br />

the head of the needle.<br />

NOTES<br />

1. When going outbound, reference the tail of the needle.<br />

2. With needle at the 45° benchmark, rate of DME and radial<br />

change are equal. With needle anywhere else, DME and radial<br />

change rates are inversely proportional (if DME rate is increased,<br />

radial change rate decreases).<br />

4. You will not necessarily be able to determine the exact heading to roll out on as you are<br />

adjusting heading, but that is not as important as altering heading before it is too late. Once on<br />

the new heading, let things settle down (i.e., cross a few radials; let a few tenths of DME pass)<br />

then update again by trying to determine if the aircraft will hit the radial or DME first.<br />

Remember, the goal is getting as close as possible to the point. Continually update until crossing<br />

the point. If the solution does not work out exactly, plan to arrive either at the desired DME or<br />

radial prior to the fix. If arriving at the DME first and within 30 radials of the desired radial,<br />

turn to arc toward the fix. If arriving at the radial first, turn to track inbound/outbound to the fix.<br />

Common Errors.<br />

1. Failing to expedite the first three steps. Remember, there is plenty of time to refine the<br />

solution once proceeding in the general direction.<br />

2. Reversing the direction of the imaginary no-wind heading line by extending the imaginary<br />

line from the fix through the present position.<br />

3. Failing to make frequent updates. As the aircraft gets closer to the station, more frequent<br />

updates will be required to ensure an accurate solution.<br />

4. Placing the wrong fix at the outer edge of the HSI card.<br />

5. Proceeding to the reciprocal of the radial/DME instead of the radial/DME.<br />

ENROUTE PROCEDURES 6-13

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