A310 Profile Descent - Speed Question

[JRHorse]

Good day,

I've returned to flying the A310 in the sim and just had one question, as I can't seem to find an answer to it.

I have not run into this scenario yet, but is there any way to modify the descent profile of the A310 ahead of time to change its speed (like can be done on, say, A320 or 737NG), or is that done strictly from the FPLN pages in the case of the A310?

The scenario I may run into is on STARs to certain airports that have the speed instruction to maintain mach number until 280 knots (or whatever the chart says) then maintain the speed in knots until slowed by the STAR. So I am wondering if, say, I could set a descent speed of "mach number / knots number." 

Thanks for any assistance,

Jose

[bear.is.flying]

You can change the target speed anytime via the TACT page. 

[JRHorse]

I just completed a flight from ORD to DEN in the A310 and tried the TACT speed intervention, setting the 280 knot speed as called for in the star. Unfortunately, this did not stick (it went back to ECON speed after passing a waypoint). Changing this a few times resulted in the aircraft flying too high off of the descent path and not respecting altitude restrictions on the approach. The PROG screen also got stuck on ECON CLB, which is a first for me; not sure if it resulted from what happened here.

[Deleted Account]

I think the easiest way to achieve this (and probably how pilots do it in the real world) is to fly the descent manually with V/S or LVL/CH and a set speed.

[JRHorse]

Thanks, I experimented with V/S and Level change on my return trip to Denver. Seems I have some homework to do on these descents; some descent restrictions were met while others were missed. While following the vertical deviation at times, I noticed it fluctuated from waypoint to waypoint. I'm guessing this is normal behavior?

[JRHorse]

I did a A310 flight from KDEN to KDFW with a pretty straightforward route. After reading your comment and doing my homework, looking at some very interesting cockpit videos on YouTube, and reviewing a fascinating document I came across on google about the A310 autoflight system, the method I took to using the autopilot was as follows:

-Climb in Profile
-Cruise in ALT.HLD
-Descent starting in VS using descent calculators, then eventually changing to LVL/CH before configuring for approach and landing

The V/S Dev showed I was way below the descent path, but at least I hit all of the altitude restrictions properly this time. 😅

One thing I noticed on the descent was that I could not set a pre-set speed in knots in the speed display, and was wondering if this was a bug. Pre-set speed worked fine before departure (setting my V2 and then using Pre-set to select 250 knots). On descent, when the plane was descending in VS and Mach and I attempted to pre-set a speed of 290 knots (so it could capture 290 knots on the descent per the STAR), the Pre-Set button did not light up and the display read 000 knots, spooling the engines down at that point. Clicking the black button to the left of that display returned me to mach, and the engines were revving up again. I ended up just leaving it in Mach speed until 290 knots was indicated, then selected the black button to change Mach to Knots.

Many thanks for your insight and feedback!

Edited September 12, 2023 by JRHorse