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Comment by biot | Hacker News Reader

I've had a similar experience while driving on a highway at night in foggy conditions. All of a sudden my car started slowing down and was rapidly losing power. I checked and it wasn't fuel, so I figured the engine was dying somehow. It wasn't until I tried gearing down that I realized I had been on a steep hill and fifth gear wasn't powerful enough. But even afterward, I couldn't sense that I was on an incline.

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I have a simple trick for that: I know the consumption of my car on a level road in 5th gear at 90 km/h, so when I'm in doubt about whether or not I'm going up, down or level I look at the fuel consumption indicator.

If it is higher than 6.6L/100km then I'm going up, less is down.

If you don't have a fuel consumption indicator then that will not work but lots of cars have them these days and I think using them as a level is a useful unintended application.

This is the first I've heard of fuel consumption indicators. What kind of car is it?

Citroen C8/Peugeot 807 (same car, different badge). It's built into the trip computer.

All car computers know this even if they don't display it to you. The computer directly controls the flow in the injectors and the computer knows their flow rate (unless you swap them out, of couse).

First I saw was in a Saab 9000, around 1991.

My Subaru Liberty has one.

No offense intended, but this scares me.

They are ~everywhere~ for a long time around me. Quite a lot of driving instructors (specializing in 'reduced fuel consumption' trainings) use them as a general guideline to "see" how your behavior drives the consumption up.

Heck, mum and dad use that thing for years and drive even slower since they first saw that they could make their car use less gas.

You need to get a new car.. :)

My car is only 14 years old and still too reliable to need replacing, but I've seen a few newer cars with no fuel consumption gauge.

Another trick might be using star alignment. A fixed position camera on the top of the plane could sense pitch by tracking which stars are in view. Or similarly, if you boxed a sensitive GPS receiver so that it could not detect signals from the sides, the satellite IDs which are in view could possibly indicate alignment of the plane as well. The best model would tie in as many observations as possible to maximize the probability that it is right.

EDIT: What about fuel sensors in the wing? If the computer knew the volume of the remaining fuel and the altitude was not dropping, it could determine the orientation of the plane if there were sensors inside the tanks to detect which were submerged.

Unless the wind is blowing toward you.

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