Possible vnav speed bug

Hello IPACS Team,

I would like to report a possible VNAV/FMS issue affecting multiple Boeing aircraft.

During climb with LNAV, VNAV, and autothrottle engaged, the aircraft initially accelerates normally above 10,000 ft to around 300–310 knots. However, shortly afterward, the FMC/autopilot commands the aircraft back to 250 knots and keeps it there even during higher-altitude climb and cruise phases.

This eventually causes the autopilot to pitch up aggressively while attempting to maintain altitude, resulting in severe speed decay and near-stall conditions at higher altitudes.

I first noticed this issue in the Boeing 777, but after testing the Boeing 747 on different routes, the same behavior still occurs. This suggests the problem may not be route-specific or aircraft-specific, but instead related to VNAV/FMS logic in general.

Additional observations:

- LEGS page does not show any visible 250-knot speed restriction

- Autothrottle remains active

- The issue occurs repeatedly on different routes

Possible causes:

- VNAV speed management bug

- FMC incorrectly maintaining below-10,000-ft speed restriction logic

- Hidden or incorrectly interpreted speed constraints

- Climb profile/autopilot issue affecting Boeing aircraft

Thank you for your continued work on the simulator.I have attached the image of the route which I was flying.

Version of simulator -1.06.03.03

Device-Redmi Pad Pro 5g

I first though it might be a mistake by me so I tried the copilot but it still persisted.

Quote from Jet-Pack (IPACS)

Thank you, we will look into this.

On the cockpit screenshot autothrottle is not active though, LNAV is also not active. Did you disengage the copilot or autothrottle manually?

I did disable it to try and speed up on my own.Here is another sc with copilot enabled .Also I used timeskip shortly after takeoff.

Quote from 777Driver

Stating the obvious here, but there are no waypoints in the route. The FMC is looking at the first waypoint of the STAR into Delhi 'IGINO' and restricting the airspeed. An en route waypoint is needed since the Aerofly FMC is simplified.

I see this on short routes where the SID/STAR is all that is required; I still have to add a waypoint shortly before the first STAR waypoint.

Using that same route, the FMC is predicting I should be at 254 knots

I reinstalled the simulator and did the same route ,without adding any additional waypoints and now it's working as it should.