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Comment by liendolucas | Hacker News Reader

Asking just out of curiosity/ignorance. The author mentions that the F35 has a completely digital touchscreen to basically do anything on the aircraft (I assume). I can also image a powerful gun damaging it, then how does pilot manage if that screen stops working at all? Compare the same situation in the F4. The hit would only break/damage the instruments on that line of fire, correct? So in one case you would be totally screwed while in the other one you would partially lose some instruments, right? I must obviously not be taking into account something (or many things) for the F35, but in my mind having a 100% digital aircraft seems pretty scary.

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Generally, if the cockpit is getting hit with damage to the instruments, there is a very good chance the pilot has also been injured or killed, and doesn't care about the instruments anymore.

In old gun fights (which just don't happen anymore), shots were likely to come from behind (so, they intersect the pilot) or the top (so, through the canopy if they're hitting the instruments). This has to do with the orientation both planes are probably in if one is shooting at the other. Go back farther and you get shots from the front, not from fighters (head-ons are very difficult to pull off outside of videogames) but from bomber tail gunners - very old planes from WWII even had bulletproof glass in front of the pilot for this reason. If the F35 has gotten into a gunfight, the pilot has fucked up, it's not a dogfighter and wasn't designed to be one.

Even nowadays, if the missile or flak pops next to the cockpit and has managed to damage the instruments, there is a very strong chance the shrapnel has also hurt the pilot to the point that they're not flying home that day. This is the most likely way for the F-35 to be damaged in the modern era.

There are obviously scenarios where the instrument panel gets damaged but the pilot is okay, but it's such a low probability scenario that they likely deemed it to be less harmful than the benefit they foresee in a glass cockpit.

Thanks for replying! As other mentioned I was missing/not considering the most important case that the pilot is assumed to be dead and that the plane is not supposed to receive such fire.

The relevant question strikes me as less extreme outlier combat scenario, more routine safety of flight upon primary display LRU failure. See this reply[1].

[1] https://news.ycombinator.com/item?id=41683263

Can't speak for the F35, but for the fighter I work on we basically consider the pilot dead if you have shrapnel damage in the cockpit. For instance, the FCS is located behind the pilot. That being said, I would assume the F35 display being at least dual redundant (think two displays merged together, which can be done seamlessly) for flight safety reasons.

If the displays are merged seamlessly, how will you know if one has failed?

I assume both displays in use, but have failover to one only if a display goes “dead”and then the single display can still display the most critical information/controls to the pilot; to me that seems like the only logical implementation. Giving 1 of the 2 screens failing. It should be fairly easy to set up a redundancy failover process, I’ve done that many times in embedded coding where we failed over to a backup system.

Reduction in brightness?

I assume they're using LCDs, where the brightness is provided by the backlight.

> I assume they're using LCDs, where the brightness is provided by the backlight.

Presumably that also would be duplicated. Why go to all the effort of having two displays but still have the risk of a single backlight going out and making both displays useless?

Uhh, the pilot will notice that the right half of your display is black and you have to move the displayed data to the left one?

Uhh, that's not "seamlessly blending two displays", that's just having two desplays. If you've seen photos of planes, they don't just have an empty screen next to a working one anywhere.

Ah, I misunderstood - it's not uncommon to have those "big" screens also put together from two different screens side by side.

This is actually what I meant by "merged together". They are two separate displays controlled by separate computers, with separate power supplies etc. During normal mode operation they're synchronized somehow and can draw a large image over the entire display area, but in emergency mode you can display crucial flight data on only one of them if the other stop working.

I have never really thought much about it, but I guess the actual LCD thingie is manufactured in one piece and the control signals just being split between different computers somehow, but I don't know anything about how these things are made! :)

Here's a paper on a redundant display for military aircraft. Each LCD panel has redundant inputs, driver circuits, and power supplies. The two displays are built on a single LCD substrate, so there is no line between the two. https://www.mrcy.com/resourcehub/displays/dual-redundant-dis... https://www.mrcy.com/legacy_assets/siteassets/product-datash...

The backup for the display is an integrated standby instrument system (ISIS), which combines several essential instruments into one small digital display. An ISIS typically has its own sensors and a battery backup, so it should stay operational even if the main display fails. https://en.wikipedia.org/wiki/Integrated_standby_instrument_...

Oddly, no one has mentioned HMDS[1] in discussion yet.

[1] https://www.collinsaerospace.com/what-we-do/industries/milit...

They're not just regular screens. They're highly hardened, redundant, specialized displays, it's a whole industry.

There are companies that make displays that have clear conductors over the screen so they can heat them so they can be used and maintain function even when on the deck of an aircraft carrier in the arctic.

There are companies that still make CRTs for specific military purposes.

These screens are safer, more reliable, and durable than the mechanical systems they replace.

The displays aren't that much special. Probably the main two things that are special about them are color rendition and contrast and the rest is just about the certification process. And extrapolating from automotive experience, the color rendition and contrast is about some team of engineers being solely dedicated to simulating various lightning conditions and verifying that the screen remains legible, does not interfere with night vision and does not cause reflections on other instruments that would make them hard to read. In automotive this kind of simulations use multiple terabytes of reflectivity data for various mostly “dull” materials (gigabytes upon gigabytes of data on what the driver might wear…), so extrapolate from that to “most advanced fighter aircraft”.

They kinda are:

https://viewpointproducts.com/products/?gad_source=1&gclid=C...

Basic flight instruments almost always have a backup. In case of F-35 there's a small square screen in centre console which shows attitude indicator and flight parameters. Needless to say, if main screens are out you are turning around and looking for the nearest airport.

I'd imagine the ejection system is going to be activated by traditional handles, and not a screen. Same with the basic flight controls; there's no reason to move to a touch screen throttle or flight stick.

The F35 is not meant to be a dogfighter. If it has gotten shot such that the control screen in unusable, something else has gone wrong.

It's a high performance fighter with a gun and SRMs, so...

...so you turn around and go home long before you're forced into a gun fight.

Sure, the F-35 is a multirole fighter aircraft with a gun - so is the F-15E, but that doesn't make it a dogfighter. If you're in a position where a guns solution is your only kill option in an F-15 or an F-35, something has gone terribly wrong. Pretty much everything about both jets is designed to operate in a theater with extremely high levels of air support and friendly materiel. It is assumed that they won't get into a dogfight because it is extraordinarily rare for an F-35 to exhaust two AIM-120s in a single sortie, let alone the 6 it can carry in stealth mode or the whopping 12 AMRAAMs that the F-15 can lug along.

Even as far back as the Vietnam War, forcing a missile truck like the F-4 into a dogfight with a MiG-15 was a death sentence. You don't need a very active imagination to suppose how an F-35 fares in a guns-only dogfight against an Su-27.

FYSA, F-15Es and F-35 squadrons train to BFM all the time, and it happens in exercises all the time. The enemy gets a vote, and fog of war is real. I suspect the key piece you are missing is: If an engagement happens when you're in a stern WEZ, you may have to go to the merge.

Also, you are not carrying that many MRMs on an eagle unless it's the new one with quad packs.

F35s (I believe from the 134th fighter squadron of the VT Air Guard) train over my house regularly and I can confirm they do quite a lot of slow, close quarters dogfighting.

EDIT: I believe I've also seen F22s but I have no idea where they're from.

Depending on the fighter: redundant systems. Ie multiple independent Ring Laser Gyros, (viewable on multiple independent displays), backed up by analog "round dials" instruments.

If you project a line that crosses an aircraft instrument panel it's hard to imagine a line that didn't also go through pilot's body.

to be fair isn't the purpose of the F35 fairly different since it's extremely reliant on stealth and beyond visual range engagements?;Instead of getting close enough to be gunned down, it is supposed to strike from so far away that the enemy wouldn't know it's there.

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