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Comment by aberoham | Hacker News Reader

Did anybody notice this 737 Max-7 test on Tuesday? Quite an interesting altitude and speed pattern --

https://flightaware.com/live/flight/BOE1/history/20190312/16...

When I replayed the flight on this map I noticed that the airplane lost a little bit altitude when it made a turn. And some turns are very narrow. It is normal for an aircraft to lose a altitude when turning.

Could you explain to a layman like me the interesting parts?

Check the 'detailed track log' - you have to click to show it on mobile - for the altitude & speed graphs.

A normal flight (https://flightaware.com/live/flight/QFA804) goes up smoothly. This one very much does not, and the patterns shown bear a resemblance to a layman like me to the published flight patterns of the Lion Air flight.

Note the very steep climb on this flight also. Who knows what that means.

People who know way more than I do, please step in!

The apparent difference in steepness arises from different scaling in both altitude ("typical flight" reaches almost 12 km, while "test flight" reaches almost 6 km) and time (the 5 minute intervals are twice as large in the "typical flight" graph).

The actual time to reach 6 km was around 6.5 minutes in the "typical flight" and around 5 minutes in the "test flight", as can be seen by scaling both graphs to the same proportions. (I've done it quickly with Paint here: https://i.imgur.com/IZyYoCl.png)

Is that 1.5 minute difference really that high? Honest question, I really don't know anything about this topic.

EDIT: Sorry, this should have been a reply to @rkagerer's comment.

If a test aircraft, it is probably very light, Boeing Field is probably under noise abatement procedures and they might just be optimizing for minimal flight time to get to test altitude. Would have to compare to normal test/aircraft checkout flights and not airline tracks.

But no doubt they would be flight testing the reputed MCAS changes at this time so it’s a reasonable guess.

I would assume they were testing flight overide logic... which takes some balls...

Yeah, I can hardly imagine being the crazy/gutsy person actually doing a test of failure modes on a plane in the air. I mean, what exactly are your options if it goes wrong? Maybe you can parachute, but seems like a long shot given altitude and the plane itself (just aim it at an uninhabited area before you jump?)

I'm just... gonna go back to my office job, I think.

The type of error that this appears to be is solved if you know what it is, you can just turn the MCAS system off and hand-trim the plane no problem. So testing the failure at a high altitude is of a relatively low risk, you've specifically briefed and likely practiced in a simulator exactly how to turn these systems off. The pilot not flying the plane almost certainly has their hands right on the switches and or fuses.

Note, though, that as soon as you do that, you're flying an airplane with flight characteristics that are unlike any other aircraft you've ever flown (unlike any ever built before); an unstable aircraft with extreme stall characteristics you've never encountered - not a normal airliner. And you're close to the ground already.

Serious question:

WHY has not Boeing turned every single aircraft of theirs into a drone-capable device?

They should have a person, like we have with air traffic control, sitting monitoring all planes in flight, but that person is sitting in a pit on the ground.

They have to monitor X number of craft - and in the event of any anomolous data.... be ready to take over control of the machine in the air.

Imagine if all pilots had a life sensor on them, and should they fail - control of the craft auto switches to ground control.

We can already kill millions of people with dron pilots in nevada. Why not make drone pilots fly airliners.

Heck, in a few years - you just need a few technicians in the cock pit to be sure there are not physical issues - and let the ground pilots do all the work - but the air pilots can take over if the ground connection is lost...

Here are two obvious reasons:

1. Lack of low-latency communication. The Ethiopian Airlines crash flight occurred when flightradar24 couldn’t see the plane. Two-way communication is even harder than just receiving transponder signals.

2. How, exactly, is a random Boeing employee going to help? They’re thrown into a situation in which sensors are faulty and they can’t see out the windshield.

What makes you believe that a ground pilot will be more competent than the existing air pilots?

It is very rare for crashes to occur because the pilots both become incapacitated. I do remember a crash that occurred because the pilots allowed the cabin to become depressurized and failed to diagnose the problem. Eventually everyone, including the pilots, fell unconscious and the plane circled on autopilot until it ran out of fuel.

Arguably this should be possible for cars as well, as a transitional stage towards full self-driving capability.

With planes you could argue that the additional complexity of implementing something like this would be a safety liability in itself. It's not 100% clear what problem it would solve. On the other hand, plenty of people would pay to not have to do the driving themselves.

I freaking love this idea with cars.

Pay disabled people to GTA 5 you home....

(aside: japanese cafes are employing disabled-driven robots....)

Dont be so hard on yourself, office jobs crash and burn at a much higher rate.

I suppose if the hazard pay is enough to set my family up for life...

There is literally no amount of money that compensates for an absent parent. YMMV, of course, and the calculus is different if you're single or something.

That's like saying money can't buy happiness. Technically it's true but money can buy you things that make the difference imperceptible.

Perhaps the steep climb has to do with how the incident airports were setup?

“Data released by the Sweden-based service suggested the aircraft had climbed almost 1,000 feet after taking off from Addis Ababa, a hot and high-altitude airport whose thinner air requires extra effort from an aircraft's engines.” https://af.reuters.com/article/worldNews/idAFKBN1QR07Z

Extra effort from the engines? That sounds a little silly, like they just need to be motivated to work a little harder. Take-off power is take-off power.

Reduced air density just means the engines don't produce as much power and the wings don't generate as much lift; a double-whammy of lower available engine thrust and greater speed required for the same takeoff roll.

> Take-off power is take-off power.

I don't think it is anymore - not with noise abatement rules. You can take off in X meters with 100% throttle, or 2X with 80% - but the runway is 4X meters, so you takeoff with reduced throttle to make things quieter for the neighbors.

I don't know whether there are really regulations for that but as a pilot (which I am not) I would not want this as this would lower the decision velocity (I think it's v2) after which the start can't be aborted.

It has some interesting dips that seem to be testing some form of sudden dip in altitude which could be seen as related to the system under scrutiny, a safety system designed to prevent stalls which could in some cases "send the plane into a fatal descent if the altitude and angle information being fed into the computer system is incorrect"

(not that any of this confirms that the MAX has issues or this is what they were actually testing)

Illustrating the answers from snek and jen729w to help clarify: https://i.imgur.com/p8uEwMh.png

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