future methods of determining height?

[liam548]

Is using pressure related instruments still the most accurate and best way of reading your altitude/height in aircraft?

Is GPS not accurate enough now to replace it or if not will it ever be?

It seems it would avoid some of the problems related to pressure related instruments..

Interested in your views and opinions.

Liam

[SNS3Guppy]

Liam,

Barometric altimeters work just fine. They're also fairly inexpensive.

As aircraft complexity increases, barometric altimetry is supplemented by the input from air data computers; this is standard for aircraft operating in reduced vertical separation airspace (RVSM). At low altitudes, radar or radio altimetry is also utilized.

For a light airplane doing every day run-of-the-mill kind of flying, a simple barometric altimeter works just fine.

[IO540]

GPS is much more accurate but for historic reasons we use barometric altimetry, which works fine for relative traffic separation.

Nothing is likely to change in the foreseeable future.

[robin]

Is using pressure related instruments still the most accurate and best way of reading your altitude/height in aircraft?

Is GPS not accurate enough now to replace it or if not will it ever be?

It seems it would avoid some of the problems related to pressure related instruments..

Interested in your views and opinions.

Liam

I quite agree, Liam. Lots of what we do is antiquated in the modern world. Perhaps we can dump that 400-year old anachronism of gravity next.

[C172 Hawk XP]

Perhaps we can dump that 400 year old anachronism of gravity

Well, I'm d*mned . . . . is it really only 400 years old ?
So is this a possible explanation for the "ascension", then ?

[liam548]

Originally Posted by robin

I quite agree, Liam. Lots of what we do is antiquated in the modern world. Perhaps we can dump that 400-year old anachronism of gravity next.

Seems that aviation lags behind the rest of the world. From engine designs / safety features to use of analogue AM radio and HF radio whereas the rest of the world is in the digital age.

But then again in other areas I suppose aviation is way ahead..

[Fg Off Max Stout]

If it ain't broke don't fix it.

A traditional barometric altimeter is:

• Relatively cheap.
• Virtually indestructible.
• Needs no power source. Draws no load from the aircraft electrical system, battery or engines.
• Will work after a complete electrical failue.
• Sufficiently accurate to provide safe separation.
• Easily adjustable between required datums: QFE, QNH, SPS etc.
• Pressure altitude not true altitude is directly relevant to many aircraft performance calculations.
• Many users of the atmosphere do so without any electrical systems (eg some vintage aircraft, microlights, balloons, airships, parachutists, skydivers, mountaineers! etc etc.
• Transponder altitude reporting is based on pressure altitude on the 1013 datum not true altitude.
• Robust. GPS signals can be easily jammed or spoofed.

From experience in aviation some of the guiding principles are: if it ain't broke don't fix it, keep it simple and avoid change for the sake of change.

In my personal experience GPS altitude is often not particularly accurate and is sometimes not available at all.

Now given what I've written, perhaps you could offer some good reasons why the industry should choose to use GPS altimeters instead of barometric altimeters. Go on... give me ten good reaons.

(I can think of a few, but a baralt still does exactly what it says on the tin and I think is overall the best option.)

[BackPacker]

Someone also pointed out (but you may have missed it) is that above a certain altitude, the only thing that's important is relative altitude. Which means: not the altitude above terrain, but the altitude that's between me and that other airplane (or other user of the air).

Pressure drops as altitude goes up. I don't think anybody disputes that. So the best way to ensure separation from other aircraft is to assign each aircraft a different air pressure level on which to operate.

Now for convenience we add a few gears and things, and represent that pressure level as an altitude but that's just to prevent us from having two separate dials in the cockpit.

Unless you found another simple, reliable and foolproof method of ensuring separation between two aircraft, barometric altimetry is here to stay.

Is using pressure related instruments still the most accurate and best way of reading your altitude/height in aircraft?

If height above terrain is a critically important factor, eg. on a ILS Cat-III autoland approach, you'll find that the barometric altimeter is NOT accurate enough and has already been replaced with, for instance, a radar altimeter.

[Mariner9]

future methods of determining height?

Being a pedantic git, I'd say a barometric altimeter is pretty useless for determining height, which was the question posed in the title

Radar altimeter or GPS with super accurate terrain database is what you need.

Not many (if any) of the former fitted to GA aircraft, some modern a/c fitted with TAWS though

[Fright Level]

I fly all over the world with the altimeter set on 1013.25 most of the time. The altitude source is from a static source fed via an air data computer (the standby altimeter is a traditional device and shows errors of around 400-500 feet at FL300+). With MNPS over large areas of the world, we cross opposite direction traffic at a closing speed of 1,000kts and as we pass, the TCAS display shows them exactly 1000' above or below. Occasionally the radio altimeter blips as they go under and that shows a separation of 1,000' so the method of using a static source with 1013.25 set via an air data computer is pretty consistent with airlines all over the world. It works very well so why change?

[Mikehotel152]

I heard that the lead-line in not making a comeback...



I'll get my coat...

[batninth]

I heard that the lead-line in not making a comeback...

The problem with the lead line when used from an aircraft is the temperature differential, it was found that trying to account for the 2C change per 1000 feet made the lead expand and thus the readings difficult...

I agree with FOMS - it seems hard to reconcile taking a simple and well proven solution & then replacing it with something significantly more complicated and thus more at risk from failing parts.

[BackPacker]

The problem with the lead line when used from an aircraft is the temperature differential, it was found that trying to account for the 2C change per 1000 feet made the lead expand and thus the readings difficult...

On the other hand, the lead line would make navigation easier. Fishermen in the old days used to feel and taste the silt that came up with the lead weight, and used that to determine wherever they were.

I can imagine that being useful today. Throw the lead weight out and smell, taste, feel when it is brought back in. Wet - you must be over water. Covered in glass shards - you must be above an area with lots of greenhouses. Smelling of weed - you must have been above Amsterdam. Cleaner than when you threw it down - you must be over Switzerland. And so forth.

[eharding]

Originally Posted by BackPacker

I can imagine that being useful today. Throw the lead weight out and smell, taste, feel when it is brought back in. Wet - you must be over water. Covered in glass shards - you must be above an area with lots of greenhouses. Smelling of weed - you must have been above Amsterdam. Cleaner than when you threw it down - you must be over Switzerland. And so forth.

I wouldn't use it over Somalia - throw out lead weight, pause, almighty jerk on line, massive rate of descent, spend a couple of months waiting for insurers to negotiate release of crew and repatriation of airframe. Rookie mistake.