the climbing rate gauge should have HUGE variations caused by atmosphere

[raaaid]

if i were to build a climbing rate gauge i would do it base on vertical angle of heading and air speed

but as this was made by science people i bet they linked the altitude gauge based on atmospheric pressure and its gradient be the climbing rate

but now think that when your flying your going from high to low pressure though you dont change altitude

so my question: shouldnt realistic altitude gauges oscillate A LOT both climbing rate and height?

[bolox]

Try the manual for the original to see how it works
http://www.mediafire.com/download.php?awc18q83pf6w8q0

[raaaid]

thanks :)

from your link:

The K.B.B. Rate of Climb Indicator
Mark IB* is a simple means of measuring
the rate of change of atmospheric pressure
due to change in altitude of the
aircraft in which the instrument is fitted

as i predicted this scienpriests went for the obvious path

do you know what turbulences are?

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

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

edit:

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

[gabuzomeu]

Absolutely,
except perhaps if IAS <>TAS and the air itself does move up and down very fast (let's say we could call this phenomenon.... wind?)
;-)

[raaaid]

oh but the vertical wind maybe a maxium of 20 kph while the horizoantal whcih measures the plane +-400 so the error is much less than with the flawed transformed barometer

[Skoshi Tiger]

You could use your radar altimeter? Might be more accurate but would be dependant on the terrain beneath you, or a GPS, or inertal navigation system, or one of those laser gyroscope dodads. It would just be a data gathering and programming issue.


Hmmmm! What did they teach in the BAK syllabus? "High to low lookout below?"

[bolox]

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

However the ASI is part of the same Pitot Static system and thus prone to the same errors

http://www.myairlineflight.com/images/pitot-staticsyslg.jpg

[raaaid]

well but at least you agree with me that altitude needles in the game should oscilate and the climbing rate one a lot :)

[5./JG27.Farber]

Was there not German method where the needles didnt jump around? - electrical gauges or something? In clod V1 the red sides needle used to jump around but the reds whined till it was fixed. Even though as you say it was realistic........... So it was there but they took it out because a vocal part of the red side didnt want that realistic factor. ;)

[jcenzano]

well but at least you agree with me that altitude needles in the game should oscilate and the climbing rate one a lot :)

pitot-static VVI´s do not oscilate a lot, but they have LAG and they are somehow sluggish.

if i were to build a climbing rate gauge i would do it base on vertical angle of heading and air speed

and can you tell me how would you build a VVI gauge based on these with WWII technology???

because to get a "highly acurate" verical angle of climb/descent you need an INS or a pretty good attitude indicator and they did not have neither of these back then

on the other hand your "inquietudes científicas" generate pretty interesting posts :)

[zipper]

As a pilot I can say I haven't really noticed any wobbly oscillations of a VSI ... ever. Atmospheric pressure variances do not occur with the great horizontal or vertical rapidity that would be required to make it do so. Remember, it's just a bourdon tube with a calibrated leak.

:grin:

[gabuzomeu]

By the way, the same scientific maffia introduced gyro scop driven artificial horizon, while a glass of water is a good reference for horizontal in daily experience...

[janpitor]

By the way, the same scientific maffia introduced gyro scop driven artificial horizon, while a glass of water is a good reference for horizontal in daily experience...

Try the glass of water in a turn and you will see why this principle is not used

[mazex]

if i were to build a climbing rate gauge i would do it base on vertical angle of heading and air speed


Well -that's how a computer game designer would think maybe ;)

For a starter - even if it was a good idea, how would you calculate a "vertical angle of heading"? How about AOA (angle of attack) for example? And if you could get the real "vertical angle of heading" - it would have to no use as the aircraft "longitudinal angle" would only be related the air that surrounds the aircraft... And what if that air is moving up or down (which is the thing that happens up there IRL accept a dead calm winter day)? What good would then the fact that the aircraft "moves at an angle of 2 degrees at 200 Mph" do you if the air surrounding the aircraft moves down at 8 m/s? What is the real rate of climb (or descent) then?

Do some reading on variometers as there are a lot of parameters to consider accept the 1940 versions that actually only worked on atmospheric pressure rise/drop that gave many problems...

Start here for example:

http://en.wikipedia.org/wiki/Variometer

EDIT: And no - if you climb through non-turbulent air they don't oscillate (accept for engine vibrations ;))... In turbulent air the problem is mostly that they oscillate to little compared to reality ;)

[raaaid]

Try the glass of water in a turn and you will see why this principle is not used

neither the gyro work on this conditions due to precesion :)

well i admit i was wrong if it works dont cahnge it though find it surprising, i guess they dont oscilate to the price of precision

[5./JG27.Farber]

Just totally ignore me...

I guess you guys were not there.........................................


mazex - what about that radar / command fighter thing your too busy to work on? any news?

[IvanK]

Why Water couldn't be used a Bob Hoover classic:

https://www.youtube.com/watch?v=Xp2Uc9XvmjY

[SQB]

Why Water couldn't be used a Bob Hoover classic:

(video here)

Dangit, you beat me to it! This video demonstrates that non-aerodynamic (simple relative mass * gravity systems) do not give correct readings of attitude and roll. Precession, while annoying for sure, is *extremely* minor when compared to this. Gyroscopes can be re-centred using balance magnets, negating the effects of precession anyway.

To answer Raaaids initial question, I ask you "how would you, using as simple a device as possible, figure out what components of any vertical incoming air is wind (which can be much faster than 20km/h (~5ms^-1) at higher altitudes) and what is the climbing rate." Remember that in normal flight (i.e. when you are actually looking at the climbing rate gague) you climb or descend at ~2-5 thousand feet per minute which is ~25.5ms^-1, not too different from your conservative estimation of wind.


Also, using a pressure based system, pressure changes by ~33hPa per thousand feet, whereas the most brutal low fronts will change pressure by 10-15hPa over the course of several hours. Small variations in pressure at ground level have surprisingly large effects, so it's easy to forget that by climbing in an a/c you travel through a huge range of pressures.

[raaaid]

well you make a mechanism that makes this calculation:

airspeed*cos pitch angle=climbing rate

if your going at 500kph and theres a vertical wind of 20 kph your making an error in just that your real speed will be the hipothenusa of the rect triangle: 20-500-x

so then your horizontal airspeed would be maybe 490 with which the error would be minimum

also planes have artificial horizonts to know your picth angle

edit:

doesnt actually a gyro artificial horizont also go crazy in hard manoubers?

[IvanK]

"doesnt actually a gyro artificial horizont also go crazy in hard manoubers?"

Depends on the gyro system. If its a full 360 degree in pitch and roll it works just fine no matter what you do. Few if any in WWII would have had this capability though.

[raaaid]

yeah then this guy was right:

the human balnce system works like the level glass of water, even nature is flawed spin for a while on yourself ;)

perfect for a loop to do it cooridnated

and in case of thick fog perfect to go level

its the same than developing a trillion dollar biro to write in zero g

fork use a pencil

i hate the sciencepriests thinking the truth is democratic

edit:

also dont you wonder why they didnt paint the artificial horizont blue where it should be?

as it is its a totally pos for what you know you could be upside down and not be able to tell by the gauge

well the colour of the sky is a forbidden colour for macho men

maybe even more than pink you will never see a macho soldier dreess in this colour, so they didnt even paint the gauge like that

is a relaxing colour and calming like pink

http://www.doggifts.com.mx/imagesnew/6/7/7/0/9/AZUL%20CIELO%20CON%20ROSA%202.jpg

[mazex]

Just totally ignore me...

I guess you guys were not there.........................................


mazex - what about that radar / command fighter thing your too busy to work on? any news?

I did put it on the shelf waiting for that last patch that before the summer was thought to include an SDK etc... So it's been on the shelf a lot longer than I thought ;) And quite frankly I'm starting to lose in getting a decent patch these last weeks...

[SQB]

"doesnt actually a gyro artificial horizont also go crazy in hard manoubers?"

Depends on the gyro system. If its a full 360 degree in pitch and roll it works just fine no matter what you do. Few if any in WWII would have had this capability though.

Disregarding precession that is, no system imparts force perfectly.

[jf1981]

if i were to build a climbing rate gauge i would do it base on vertical angle of heading and air speed
That means accurately knowing you angle of attack and pitch angle. In aeroplanes, the simpler and more reliable design prevails.

but as this was made by science people i bet they linked the altitude gauge based on atmospheric pressure and its gradient be the climbing rate
You don't understand how complicated it is to have accurate pitch and angle of attack values. Both required if you would calculate the VS. Not to mention the fact that such instrument has 3 input, aoa, pitch and speed, it needs to makes sinus (aoa+pitch) x speed, how to you make such an instrument ? Pratcically, I don't see, and if electric failure what happens ? Want to design such an instrument with just mechanics ... not so easy.

but now think that when your flying your going from high to low pressure though you dont change altitude
Answered in next post.

so my question: shouldnt realistic altitude gauges oscillate A LOT both climbing rate and height?
Wether systems dynamic is much slower than aircraft dynamics, hence it does'nt affect the flight.
We prefer to change height when local pressure changes by maintaining the same pressure altitude (that is far from the ground, when flying "flight level" which are reffered to standard ground pressure 1013,25 / 29.92). Close from ground, calibrating the altimeter is needed, but the VSD is not affected by local pressure changes because it is too slow. So answer is no for climb rate, yes for altitude but we do with that no big deal (below 3000 ft agl), and we just don't mind above that altitude (altimeter set to std reference pressure).

In real life airlpanes do not fly at constant height, they follow the pressure lines ;) yes that's what you just discovered through your initial question.

[jf1981]

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.

[zipper]

Actually, pressure can change a lot at a particular level, that's why Altimeters are adjustable (barometric setting knob). This setting is most easily found when on the ground, just turn the knob till you have set the airfield elevation on the instrument. In flight, corrections must (practically) be sent by radio from weather or control centers and be relevant for the aircraft's location. Corrections are then, obviously, periodically needed during changing weather conditions. None of this really has any bearing on the vertical speed instrument, as it reacts to level altitude pressure changes (as while sitting on an airfield) much too quickly to register any vertical speed errors. Sit in a parked aircraft while a storm blows through and you won't see the VSI move at all.

[jf1981]

In flight, corrections must (practically) be sent by radio from weather or control centers and be relevant for the aircraft's location.

Above 3000 ft agl we use standard reference 1013,25 (29.92), there would no point keeping accurate true altitude (some areas of the world, even impossible to know local pressure), only accurate pressure altitude is needed.

[nadasero]

Because of this I am using altimeters on my bike since about 20 years. They are very precise if it goes for altitude changes. They measure in steps of one Meter and if you hold them over your head, you get usually two meters more than on the ground.

Today I'm using a GPS-System (Garmin Edge 705). It has a barometric altimeter in addition to the GPS because this is more precise for small altitude changes. It gives precise readings for the steepness of a climb and the climbing speed.

The absolute precision is not that good. Over a day, the error can grow up to 100 meters if the weather changes. Typically it is less than 20 meters. A plane, flying from one weather system to the next can see changes of more than 50 mbar which can add up to an error of 500 meters at see level.

[zipper]

Above 3000 ft agl we use standard reference 1013,25 (29.92), there would no point keeping accurate true altitude (some areas of the world, even impossible to know local pressure), only accurate pressure altitude is needed.


Interesting. Here in the US we use pressure altitude (QNE) only for all aircraft above 18000 ft MSL. Below that the combination of not wanting aircraft flying into the ground (unintentionally) during airport operations with reduced visibility and having those aircraft (below 18000 ft), both terminal and en-route, synchronized vertically requires that they all set their altimeters to their local pressure settings (QNH). Any air traffic controller or Flight Service Station can provide local pressure information, and will give it (and winds, etc) spontaneously after querying intentions.

[jf1981]

Interesting. Here in the US we use pressure altitude (QNE) only for all aircraft above 18000 ft MSL. Below that the combination of not wanting aircraft flying into the ground (unintentionally) during airport operations with reduced visibility and having those aircraft (below 18000 ft), both terminal and en-route, synchronized vertically requires that they all set their altimeters to their local pressure settings (QNH). Any air traffic controller or Flight Service Station can provide local pressure information, and will give it (and winds, etc) spontaneously after querying intentions.

Yes, in France depending upon where you are, the transition altitude varies, if not indicated 3000 ft used, but currently eg 5000 ft may be used instead in controlled areas. Apparet from that, it's flat land so in mountainous areas I really don't know what rules are applied there, we have some cities in the alps. Have to have a look at it.