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Comment by suid | Hacker News Reader

Not these fighter planes. They literally need both the propulsion and an active flight computer to fly stably. Without the flight computer, they are uncontrollable. Think balancing a pencil on your finger - if your finger is immobilized or loses control, that pencil will fall almost immediately. The plane's controls are much more complex and unforgiving.

And without propulsion, they are just flying rocks. No gliding.

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No. As long as it has electrical power and the flight controls are working it can remain stable and glide even with a complete engine failure. Of course the glide ratio is fairly low but it's totally possible for a skilled pilot to make a dead stick landing provided there's a suitable site nearby with acceptable weather conditions.

Is that true for those fighter planes? From a cursory investigation it seems like they’re not very flyable at low speeds without being in vtol mode.

Every plane has what is called a stall speed, which if you go below it it loses its ability to stay in the air. Above that, even 1kt above, the plane will still fly. Also, to make sure you can fly the longest possible distance to have time to troubleshoot any issues, planes also have what is called best glide speed. If you maintain that, you’re golden.

There are a lot of factors that come into play when you lose the engine, but unless there is a serious issue, you still have control over the flight surfaces.

That depends what you mean by "low". The F-35B (like any fixed-wing aircraft) is perfectly well flyable down to stall speed, and below stall speed it doesn't fly at all. For the conditions described, stall speed would probably be something close to 120kn (exact performance parameters are classified). (Some fighters can use thrust vectoring and other aerodynamic tricks to retain a limited amount of post-stall maneuverability but that doesn't really apply in this case.) In an engine failure situation, pilots are trained to trim the aircraft to the speed that will give the best glide ratio and that's going to be well above stall speed.

Vertical flight mode wouldn't be usable in a situation like this. They only transition to vertical flight at low altitude with the landing site in sight.

He was transitioning the aircraft from mode 4 (STOL) to mode 1 (normal flight) when he made the decision to bail. The wings were not generating lift - without computer control the aircraft could have rolled severely.

Pilots eject when the wings are level. If he was facing the possibility of severe uncontrolled roll (or believed he was) then ejecting now before the roll was a good call. At least so far as his wife and children are concerned.

The wings were generating lift and not stalled. Changing the flight control mode doesn't imply that the aircraft was in vertical flight.

Going from mode 4 to mode 1 on the F-35B (I don't know about the AV-8 family) has a significant portion of the flight below stall speed. I don't think that we know at what portion of the flight this happened.

And that's an insignificant detail in the rest of the post anyway, a nuance that does not invalidate the rest of the points made in the post you are replying to.

We do know at what portion of the flight this happened. It's right there in the report. The airplane was in stable forward flight, not stalled. You did not make any valid points.

> No. As long as it has electrical power and the flight controls are working it can remain stable and glide even with a complete engine failure.

I'm not so sure about that. I'm pretty sure that flight controls are directly tied to thrust, because it would be the engine that also drives the hydraulic system.

It's like that even on passenger jets. If you lose both engines, you also lose hydraulics (aside from whatever little hydraulic pressure the ram air turbine provides). I would not expect there to be a ram air turbine on a fighter jet, which would mean complete engine failure = complete loss of hydraulics = complete loss of flight controls.

Nope. While it's true that the F-35 lacks a ram air turbine (RAT), it does have an auxiliary power unit (APU) that can power the flight controls, avionics, and electro-hydrostatic actuators as long as fuel remains. It also has a battery that can power critical systems for a few minutes when all else fails.

https://www.lockheedmartin.com/content/dam/lockheed-martin/e...

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