Hand flying a SID...?
12-18-2015 | 08:27 AM
#12
Gets Weekends Off
Joined: Feb 2010
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I have worked at some companies that require the AP to be on for an RNAV SID and now I work for one that does not. In my experience, the AP can do just as bad of a job as a hand flying pilot. This is largely due to pilots not paying attention to their increasing ground speed and/or shallow bank angles.
If there is a sharp turn after departure, the FMS calculates when to start the smart turn so the flight director will roll the airplane out exactly on course. If the FMS does that calculation assuming your ground speed is static (let's say 160 kts shortly after takeoff), but during the turn your ground speed goes up to 250 kts, you will roll out off course with or without the autopilot engaged. Similarly, if you are hand flying, and your bank angle is too shallow, the same thing will happen.
When I use the autopilot, I make sure to keep my ground speed constant prior to and during the turn by keeping a high pitch angle. If I am hand flying. I do the same, but also make sure I start out with a 30* bank right away and shallow it out as required.
If there is a sharp turn after departure, the FMS calculates when to start the smart turn so the flight director will roll the airplane out exactly on course. If the FMS does that calculation assuming your ground speed is static (let's say 160 kts shortly after takeoff), but during the turn your ground speed goes up to 250 kts, you will roll out off course with or without the autopilot engaged. Similarly, if you are hand flying, and your bank angle is too shallow, the same thing will happen.
When I use the autopilot, I make sure to keep my ground speed constant prior to and during the turn by keeping a high pitch angle. If I am hand flying. I do the same, but also make sure I start out with a 30* bank right away and shallow it out as required.
12-18-2015 | 08:37 AM
#13
Prime Minister/Moderator
Joined: Jan 2006
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From: Engines Turn or People Swim
True. But your airplane/OPSPEC/FMS may not be authorized to fly a non-RNAV SID using the FMS. The usual workaround is to also display raw NAVAID data to verify that the FMS (and AP) is tracking correctly.
12-18-2015 | 08:38 AM
#14
Prime Minister/Moderator
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From: Engines Turn or People Swim
12-18-2015 | 08:57 PM
#15
Gets Weekends Off
Joined: Nov 2011
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From: Volleyball Player
For non-RNAV departures, there is no requirement for automation of any kind (A/P, FD, LNAV etc.).
For RNAV 1 departures, AC 90-100A, item 10 provides guidance for flight crew operating procedures. It states in paragraph (9): Pilots must use a lateral deviation indicator (or equivalent navigation map display), flight director and/or autopilot in lateral navigation mode on RNAV 1 routes. Lateral mode guidance should be engaged no later than 500 feet.
AC 90-105 covers RNP 1 departure procedures, and the flight crew guidance is the same as RNAV 1 departures.
Furthermore, both AC 90-100A and 90-105 state:
For normal operations, cross-track error/deviation (the difference between the RNAV system computed path and the aircraft position relative to the path) should be limited to ± ½ the navigation accuracy associated with the procedure or route (i.e., 0.5 nm for RNAV 1, 1.0 nm for RNAV 2). Brief deviations from this standard (e.g., overshoots or undershoots) during and immediately after procedure/route turns, up to a maximum of 1 times the navigation accuracy (i.e., 1.0 nm for RNAV 1, 2.0 nm for RNAV 2), are allowable.
While autopilot isn't required for an RNAV or RNP procedure, it might be a good idea depending on the departure, as some now include RF legs.
RNAV 1 departures require the accuracy of RNP 1. However RNP 1 departures, in addition to the RNP 1 accuracy requirement, also have a containment of RNP 2 (2x the RNP) and a crew alerting and monitoring requirement. This containment width is what the used for terrain clearance.
For RNAV 1 departures, AC 90-100A, item 10 provides guidance for flight crew operating procedures. It states in paragraph (9): Pilots must use a lateral deviation indicator (or equivalent navigation map display), flight director and/or autopilot in lateral navigation mode on RNAV 1 routes. Lateral mode guidance should be engaged no later than 500 feet.
AC 90-105 covers RNP 1 departure procedures, and the flight crew guidance is the same as RNAV 1 departures.
Furthermore, both AC 90-100A and 90-105 state:
For normal operations, cross-track error/deviation (the difference between the RNAV system computed path and the aircraft position relative to the path) should be limited to ± ½ the navigation accuracy associated with the procedure or route (i.e., 0.5 nm for RNAV 1, 1.0 nm for RNAV 2). Brief deviations from this standard (e.g., overshoots or undershoots) during and immediately after procedure/route turns, up to a maximum of 1 times the navigation accuracy (i.e., 1.0 nm for RNAV 1, 2.0 nm for RNAV 2), are allowable.
While autopilot isn't required for an RNAV or RNP procedure, it might be a good idea depending on the departure, as some now include RF legs.
RNAV 1 departures require the accuracy of RNP 1. However RNP 1 departures, in addition to the RNP 1 accuracy requirement, also have a containment of RNP 2 (2x the RNP) and a crew alerting and monitoring requirement. This containment width is what the used for terrain clearance.
12-19-2015 | 09:43 AM
#17
Are we there yet??!!
Joined: Apr 2006
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I was just happy to have an autopilot that could track and hold altitude (not kidding).
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