[jf1981]

Originally Posted by raaaid

do you know what turbulences are?

sub and overpresures, they happen all the time so the climbing indicator goes crazy

It makes no big deal, even today's airplane set their instrument to the standard pressure passed a certain heigh. That means they effectively do not fly at a constant height from the ground, depending upon environmental pressure, but they accurately fly on a so called "flight level" or FL. All aircrafts in the same area have the same reference, this is all that matters when flying high.

the elemental way to fix this flaw is to link airspeed and angle of climb to have a precise climbing rate reading

Altimeter and vertical speed indicator both use the same pressure, the only error is height/altitude because we do not know the local pressure unless we ask for it. Again that's not a problem at all since we just fly on a standard reference passed 3000 ft AGL. We make a little bit of yoyo if the local pressure changes across our path but it does'nt change that much and that fast where you could notice from inside it has changed. It's so smooth that it does'nt affect the flight.

its an educated guess wflying really low the altitude gauge can even read negative :O

Yes true, but that's why we always need to know the local pressure when getting below 3000 ft agl. That's not talking about cliffs of dover because we don't care doing belly landings anyway

Basically, you should set your gage before taking off to either actual field altitude or zero if you would like to have a correct reference. If your field is close from the sea level and today's local pressure is very low, you may well read a negative number in the first place. If you would like to land where the local pressure may be very much different, you better ask for the local pressure before going low.


There's no other logical way than having VSI and altimeter using the same references, either both based on local pressure measurement, or both on calculus, if not, they would could show different things eg altimeter climbing but zero vsi. And there's no way to base altimeter on your method. You also forget that such VSI does'nt know the vertical winds, if you pass through a "wind pump" shortly before landing, the instrument would'nt recognize it. Could be dangerous. If you add the facts that such an instruments needs to know angle of attack ... more complicated, error induced if there's vertical wind locally, requires accurate measurement of pitch and angle of attack, needs true air speed (ias is not enough, so it also needs to know ias + altitude) ???

basically, the design you called for requires :

- Altitude
- Indicated air speed
- Pitch angle from gyro (with very good accuracy)
- Angle of attack (very good accuracy)

To go into one instrument, the VSI, out of what it can calculate only vertical speed but would'nt show the correct value if there is vertical wind.
Preferably, the instrument should not need electricity, if it would, please add to "requirements", and if so, an electrical failure would make for the VSI failure.

I think Einstein said "as simple as can be, but not more". That is what we currently have. I would ask you to design other aircraft systems, unless you really understand the statement in italic. Things sometimes look simple when they are not.

Just a touch of humour if you allow me, it makes me think of George Clooney's words "Gyro VSI, what else ... does it need ?", the standard instrument does only need one static pressure source if I'm right.