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Comment by rootusrootus | Hacker News Reader

The A380 is pretty smooth, but I found that the way it cruises is not great for me. It tends to surge and glide in a way that prevents me from actually falling asleep, more so than on other smaller planes like a 787. While the 787 might not be as silky smooth taking off and landing, I prefer it for the long term comfort that matters for most of the flight.

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As I understand, the single greatest comfort improvement on the 787 is higher pressurisation: 6,000ft vs 7-8,000ft. The lower pressurisation on older planes is rough after you have experienced the 787. I felt much fresher after a long 787 flight compared to older planes.

Oh, I thought it was just me! All the Airbus planes have horrible autopilots that gradually rise and fall, in a barely noticeable way. I found myself feeling irritated and wished the source code was opensource so I could have a look at it.

Are you telling us this as a pilot or a coder? Calling it's autopilot is horrible is a lot of stretch.

Horrible may be a bit hyperbolic, but it underperforms other airliners.

I don't do well on flights, usually feeling slightly nauseous the whole time, and this made it worse. I could tell the difference from the Boeing jets.

That’s intentional, it allows the plane to do minor speed adjustments without altering engine speed that much by wandering a bit above and below the set altitude. The autopilot mode is called ALT CRZ (as opposed to just ALT).

In a similar vein, my boss complained that the cabin was too quiet, and he couldn't sleep hearing all the other sounds that are usually blocked out by ambient noise.

Is this how pilots are taught to operate it? Or how the engines automatically operate when the pilot is throttling "smoothly".

The pilot is not flying the plane at cruise, the autopilot is.

The autopilot can definitely have an effect on how smooth the flying feels, depending on how autothrottle and altitude hold control loops are implemented.

My understanding is that pilots frequently fly parts of the cruise so that they have adequate "stick time" to stay fresh and familiar with the machine.

Probably not the actual cruise (30k+ feet at M0.7+), but definitely some of the nicer approaches and departures. Hand flying an airliner in cruise within the tiny strip of air it’s allowed to fly in (google Reduced vertical separation minima) is no fun.

Pilots are still doing a job, and sometimes that job involves keeping their skills fresh and honed, or working around a partially non-functional or degraded autopilot. Sometimes it's even a matter of personal preference, with some pilots preferring more hands on time than others.

I’m not sure if you’re disagreeing with me, so I’ll expand on the previous post: most commercial flights cruise at altitudes where it’s not allowed to fly without autopilot. Not for honing the pilots’ skills, not because of a malfunction.

There are parts of the flight where hand flying is allowed, but those are the parts closer to the ground (or on very short hops where the cruise altitude is significantly lower than usual).

Flying an airliner by hand at cruise is dangerous and usually constitutes an emergency. ATC expects the plane to stay precisely at its assigned altitude, especially in RVSM airspace. It's difficult to keep that altitude by hand at speed. Cruise is also normally done close to the edge of the plane's abilities, so small deviations can have catastrophic effects (overspeed or stall).

Airline pilots routinely do takeoffs/departures/approaches/landings by hand to practice their skills, but not cruise. See this Airbus doc: https://safetyfirst.airbus.com/high-altitude-manual-flying/

> While the 787 might not be as silky smooth taking off and landing, I prefer it for the long term comfort that matters for most of the flight.

Cyclists generally prefer carbon fiber over aluminum because the former is smoother than the latter. 787 is carbon fiber, A380 is a fiberglass/aluminum composite. I wonder if that's why the 787 is smooth.

I'm not an expert on planes but I'm not aware of another commercial airliner that's carbon fiber.

I can feel that glide too. You are flying along, then feel a slight gliding fall, then a wobble. You always feel any turbulence during the glides too.

Sorry for the highly technical terms but I agree it is unique to the A380.

Apart from this they comfortable to travel and sleep on.

What are "glides"?

The flying equivalent to a car coasting.

I think it's the slight (unexpected and short duration) change in altitude. That sensation of ground falling under your feet, with a slight sense of suspension. As if the craft is sliding down. (Glide as in gliding down a slope.)

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