[arghwhat]

> In this case the F–35 has three independent displays that can all redundantly display the same information

This is not true. The standby display is just a tiny artificial horizon by the pilot's right knee, so when HUD and primary display is out, all you're left with is your speed, altitude and attitude. This cannot in any way or form be considered "the same information" as the primary flight display of an F35B, and leaves you without a lot of control.

Whether you can limp along with such backup system depends entirely on what is going on at the time the primary flight displays go dark. In a fighter jet, that display may in some cases just tell you what angle and velocity you are going to die at. Furthermore, in challenging conditions you might have to make a decision very quickly and might not have time tuning yourself into the standby display and its degraded information.

This type of degraded backups exist in many aircrafts - you don't want the pilot of an Airbus you're in to be confronted with the plane dropping to mechanical law, or even direct law if taking off or landing, even if these modes are technically flyable and well documented.

[db48x]

The standby display is only “tiny” in comparison to the primary flight display, which is a 25” LCD panel. It’s actually the same size as the artificial horizon in most general aviation planes. The information shown on it was not degraded in any way. The accident investigators concluded that the pilot could have and should have relied on it to fly the plane. He just didn’t.

Furthermore, it’s not appropriate to compare the standby instruments with the alternate control law of Airbus airliners. I don't know if the F–35 has anything comparable with Airbus’s alternate law or direct law, but if it does it wasn’t activated during this incident. The pilot did not experience any loss of control of the aircraft.

But I agree with you that a lot of incidents involving Airbus aircraft have been related to alternate law. Pilots get caught out by it all the time, apparently.

[arghwhat]

As said elsewhere, it’s not that a plane can be kept in level flight with an artificial horizon that matters. As with the airbus pilots, it’s the surprise - especially when it happens in already stressful situations.

In this case we’re also dealing with an instrument SVTOL landing in terrible weather which cannot be flown with just an artificial horizon, repeated electrical failures in a short timespan, a disbelief that the aircraft correctly reverted from SVTOL to winged flight mode with all relevant instruments to confirm out - as the site says, “extremely challenging cognitive and flight conditions”. And, a manual that says if the aircraft goes out of control at low altitude, you must eject.

At a high altitude cruise it could have been flown just fine by the horizon while things get diagnosed and possibly diverted to a landing suite suitable for the remaining equipment.

[ExoticPearTree]

> ... all you're left with is your speed, altitude and attitude.

Which is all you need. You have the same information in any other aircraft, most only have airspeed and altimeter info. An attitude indicator is of great help when you're flying through clouds so you can check that you're actually flying in level flight - it is pretty weird to find out you're actually flying banked but because you have coordinated flight you don't feel it.

[arghwhat]

Have you flown a modern fighter jet while suddenly your helmet integrated flight displays and navigation went out and you had to reorient yourself and rely entirely on nothing but your knee-mounted false horizon mid-maneuver, while attempting instrument landing under - and I quote - “extremely challenging cognitive and flight conditions” where you due to repeated electrical glitches have lost faith in the aircraft and in particular its ability to transition back from SVTOL to regular flight operation? Because that was the situation that you claim was fine.

You can keep an otherwise fully functional aircraft in stable level flight using a horizon, but that’s neither interesting nor relevant. This was not a lightweight aircraft cruising above the clouds with nothing around it.