Airspeed indicator is unavailable after CDU WARM START, how to fix it?

[EviLHuAi]

I have tried restarting the CDU and recalibrating the NAV INFLY, but to no avail

 

While taxiing at the airport, I entered the grass which caused slight shaking of the airframe, leading to a CDU WARM START. I believe the aircraft itself did not sustain any damage. However, since then, the airspeed indicator has stopped working.

 

Edited October 11, 2024 by EviLHuAi

[Yurgon]

As far as I'm aware, the airspeed indicator is fed by the pitot-static system and is completely independent of the CDU and the jet's more modern functions and systems. A CDU warm start, the INS alignment status, EGI and EAC - none of these should have the least amount of impact on the airspeed indicator (both the steam gauge and what's shown in the HUD).

In fact, if you take an air start machine like in the Instant Action Free Flight missions and switch off all the fancy avionics (EAC, CDU, EGI), the airspeed indicator should be entirely unaffected.

My first guess was that this might be a case of pitot tube icing, but the second screenshot shows PITOT HEAT ON.

That leaves us with probable damage to, or blockage within, the pitot static system. If you have a track or a recording, I wouldn't be surprised to see the pitot tube missing or bent on the right wingtip.

This is further backed up by the lack of any caution on the caution light panel and the fact that EGI is selected on the NMSP, plus you do have a TVV visible in the HUD.

The only way to get the airspeed indication back in such a case would be to repair the jet on an airfield.

However, provided that EGI is up and running and aligned, you could switch the IFFCC menu to the test position and there select the HUD airspeed indication to show GS or ground speed, then switch IFFCC back to ON. This speed readout in the HUD is then fed by the GPS/INS and should be fairly accurate. Especially when you have a somewhat accurate weather report and know the prevailing winds at various altitudes, you should be able to fly at a suitable airspeed based purely off of the ground speed readout. Just be super careful because wind will have a massive effect here; if you're used to flying an approach at, say, 150 knots, and now you're desperately trying to maintain 150 knots groundspeed, your actual airspeed, depending on wind, might be as high as say 200 or as low as for example 100 knots (if there was a very, very strong head- or tailwind), meaning you'd either have a very hard time to land, or have an even harder time staying airborne.

[EviLHuAi]

Thank you so much for your patient explanations!

Since I restarted the mission using Shift+R in the game, there is no longer a track or recording. If the situation occurs again, I will try using the method you mentioned to switch the airspeed to GS in the IFFCC as an alternative speed detection solution.

Thanks for letting me know that GS is measured by GPS/INS.