Descent FMA on Beta 13

[emerydc8]

I agree. So, once you are back on path, it will go to IDLE||VNAV PTH and if no thrust is required it will go to HOLD||VNAV PTH? If thrust is required it will say SPD||VNAV PTH?

In other words Beta 23 logic for the path capture feature (below the path and close the speed window) will be the same eight steps you lsted above when you commence an early descent and eventually intercept the path from below at 1250'/min?

[Hardy Heinlin]

I agree. So, once you are back on path, it will go to IDLE||VNAV PTH and if no thrust is required it will go to HOLD||VNAV PTH? If thrust is required it will say SPD||VNAV PTH?

IDLE engages whenever VNAV SPD changes to VNAV PTH for an idle descent while the throttles are out of idle.

In other words Beta 23 logic for the path capture feature (below the path and close the speed window) will be the same eight steps you lsted above when you commence an early descent and eventually intercept the path from below at 1250'/min?

Yes, except for the 1250 figure; that may be shallower to get the half path angle.


|-|ardy

[emerydc8]

If I could figure out how to post two thumbs up I'd do it! Thanks, Hardy.

[emerydc8]

Beta 23 Review:

Beta 23 seemed to be working correctly under the scenarios that I tried out. I was using my descent situ going into SFO starting at FL350. The FMC command speed for the descent was ECON at 284.

Scenario 1: Regular Descent (speed window closed)

Upon glide path intercept, it went IDLE/HOLD||VNAV PTH
Bracketed the path within the VPP (+/-400'). Most of the time it was within +/-300'. I pulled the speed brakes at one point when it was about 300' low and it correctly came in with power as it got to 268 knots (more than 15 knots slow). The FMA then indicated SPD||VNAV PTH. As speed returned to 284 knots and back on path, it went to HOLD||VNAV PTH.

Scenario 2: Speed Intervention at FL340 to 330 Knots.

On speed intervention, it went to HOLD||VNAV SPD and pitched down to capture the 330 knots that I dialed in. When it was 3000' low, I closed the speed window. Observed THR||VNAV SPD as aircraft pitched for 284 knots. Descent rate was around 600 FPM. It added power to around 65% N1, then went to HOLD||VNAV SPD. Captured the path, then went back to IDLE/HOLD||VNAV PTH.

Scenario 3: Modification -- /12000" at SKUNK (this creates a new path well below the aircraft)

When leaving FL340, executed the modification. It went to HOLD||VNAV SPD and pitched for 284 knots. I speed intervened to 330 knots and added speed brakes. As it converged on the path from above, I closed the speed window. It went to SPD||VNAV PTH and pitched for 284 knots. Then went to HOLD||VNAV PTH.

Scenario 4: Late Descent (late to reset MC altitude until 2000' high)

When flying past the ToD it went to SPD||VNAV ALT. Then, when I reset the MCP altitude to 7000' and altitude intervened (pushed the alt knob), it went to IDLE/HOLD||VNAV SPD and pitched for 284 knots. I pulled the speed brakes out and descended for the path from above. On path capture, it went HOLD|VNAV PTH.

From what I can tell, the descent logic and FMA's are working correctly. Thanks, Hardy!

[Hardy Heinlin]

Thank you for the test :-)


Cheers,

|-|ardy

[emerydc8]

Thank you!