Archived

This topic is now archived and is closed to further replies.

3-2-1-Now

PROF vs. ALT HOLD

Recommended Posts

Hi,I've got the AP figured out I think, and can now get the aircraft doing what ever I want without hassle.One thing I noticed with it however is that once it reaches an altitude as set in the FCP, it enters HOLD mode.This is fine, but it appears you need to intervene to get it to return to PROF mode for say, a step climb. Is there a way to arm PROF mode, with a higher altitude in the FCP ALT window, so at the appropriate time, it climbs on its own?If it is a manual process, that is fine, but I'm just curious. I don't seem able to set a maximum FL in the FCP (e.g. FL410), and for it to level off before then and use the FMS altitude constraint.Best regards,Robin.

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

From what i understand from ground school, During the FMS Setup, when you enter the initial cruise altitude, you also need to enter the expected step altitudes e.g. 330/350/370/390. Once you do that, MD11 will calculate the step climb points and all you need to do (cruising in PROF mode) is set the initial cruise altitude in the FCP and when nearing the S/C point set it higher and MD11 should step climb on her own.

Share this post


Link to post
Share on other sites

Robin, For climb or cruise with step climbs, you can set the FCP altitude at the last (highest) cruise altitude. With PROF mode engaged, the aircraft will level off and hold at altitude restrictions. The FMA will say HOLD but this doesn't mean that you are not if PROF mode. Since HOLD is in magenta color this means that you are still in PROF mode. It is the color that tells you if you are in PROF or not. The altitude mode can be T/O THRST, CLB THRST, HOLD, PROF or IDLE but if the color is magenta these are all modes handled by PROF. Notice, that when you set the FCP altitude higher thena a climb restriction there is a small fornt PROF TO XXX (XXX = the FCP altitude) annunciation that indicates that although the active target altitude is the one shown next to the mode, PROF mode is "armed" to climb to the FCP altitude when conditions allow.When you sequence the waypoint that has the altitude restriction you will see the FMA mode flash for 5 sec and then the aircraft will resume climb to the FCP altitude or the next altitude restriction. The same happens with step climbs. And the same with descent restrictions, but in this case the "armed" FCP altitude will be lower than the restriction altitude. Note however that under no circumstances will PROF mode allow the aircraft to climb above the FCP dialed altitude. It will wait until you raise it. In PROF mode you should always just dial the FCP altitude, never push or pull as this will disengage PROF mode.

Share this post


Link to post
Share on other sites

Just to add here, since it kinda belongs to same topic.I can't get the Speed to into PROF mode (magenta color) Should I press the FMS SPEED button for it to go into PROF? Philip Schmidt.

Share this post


Link to post
Share on other sites

Philip,Yes you should. The speed will not go to "PROF" mode but to "FMS SPD" mode, which means it will be controlled by the FMS. However, PROF mode and FMS SPD mode can be applied indepedent of each other, although obviously PROF will not be able to peform well in descent staying on the vertical path if the FMS speed for which the path is computed is not applied. One exception:In take-off mode (before thust is reduced from T/O to CLB THRST) engaging the PROF mode will also engage the FMS SPD mode. In all other cases you have to press both buttons.

Share this post


Link to post
Share on other sites

Hi Michael,Thanks for the note! The times I've seen it, it has been HOLD in WHITE, with the altitude in MAGENTA (and it has climbed there as a result of a PROF climb, which is what is confusing me.I'll be flying again this evening (shorter flight this time) so I can check this out. There might be a possibility I'm pulling without realizing it, although I don't know where I'm getting that from as follows a similar procedure on the MD-82 [ set new cruise altitude, do *not* PUSH to arm ALT CAP, press VNAV (PROF on MD-11) to start cruise-climb. Results are thrust mode to EPR CRZ limit, FMS to new cruise altitude set in altitude window. If altitude lower, starts descent phase ].Best regards,Robin.

Share this post


Link to post
Share on other sites

Robi,Note that taget colors (altitude, speed) do not denote that PROF or FMS SPD is engaged. They are magenta if they happen to coincide with the FMS computed targets, even if the mode in not FMS controlled.Also, check that PROF mode is available. If for some reason predictions cannot be calculated (you see dashed ALT, SPD, ETO, values in the ACT F-PLN page) PROF disengages.

Share this post


Link to post
Share on other sites

>> Also, check that PROF mode is available. If for some reason >> predictions cannot be calculated (you see dashed ALT, SPD, ETO, >> values in the ACT F-PLN page) PROF disengages.So if I have say 4 waypoints with auto or hard altitudes, it will remain in PROF, but if the 5th waypoint is ---/----- it will drop out on that waypoint? Does it go to V/S or FPA mode, maintaining present V/S or FPA at the time of mode change? If so, I have not seen this yet.Best regards,Robin.

Share this post


Link to post
Share on other sites

Well, a type rating course will be very welcomed since it seems to me that these modes are a little confusing. Who knows!!! Leonardo

Share this post


Link to post
Share on other sites

Hi,Got it figured!!!! If it says HOLD ALT in MAGENTA, then simply changing the altitude causes PROF NEW ALT to appear above the HOLD ALT in the vertical mode area of the FMA.If HOLD is in white, it is in FCP HOLD mode.If HOLD is magenta, and the altitude is white, it is because HOLD is the PROF mode, and the altitude does not match either the current waypoint altitude restriction of the FMS or the cruise altitude of the FMS.Best regards,Robin.

Share this post


Link to post
Share on other sites