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Pin Head

7th Oct 2017 02:27

B737NG Vertical NPS scales

Hi

The default value is 125fpm on the vertical scale.

Can I ask were this value comes from? There is a reason as years ago heard some refer to it.

Thanks

victorpapa

7th Oct 2017 06:27

From FCTM
For airplanes with NPS, the flight crew may enter 125 feet for vertical RNP. While there are no vertical RNP values published on the approach chart, the use of 125 feet will cause the NPS amber deviation exceedance alert to occur at 75 feet or slightly less deviation, since vertical ANP will be at least 50 feet at all times.

Sciolistes

7th Oct 2017 17:52

And 75 feet is the vertical deviation limit for RNP approaches.

aterpster

8th Oct 2017 12:51

The Baro VNAV Vertical Error Budget (VEB) gets smaller with lower RNP minimums; i.e. 0.10 or 0.20 vice 0.30. The scaling should follow suit for the final approach segment.

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