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Uh-1h huey altitmeter


Vinny002

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Hi, guys!

 

I noticed something in the uh-1h Huey is not right. The uh-1h Huey altimeter is definitely wrong! For example at McCarran int'l airport the uh-1h Huey altimeter should show 2,181 feet not 0 feet what the uh-1h Huey shows now. Does anybody notice this? Thanks!

 

Cheers,

Vincent

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Just a thought. Isn't the airfields using QFE as the reference and not the QNH?

(both being the baro value you should set)

If the QFE is used (I believe it is in DCSW) the reference is the airfields elevation and the altimeter will read 0.

If the QNH is used the reference is mean sea level and the altimeter will read airfields elevation.

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Since I don't have NTTR I can't reproduce that at all, but I somehow don't get what you said about the barometric setting there:

 

Hi, CrazyPandaPilot!

 

When the altimeter reads 0 feet the baro is like 31.00+. Any solutions to this problem? Thanks!

 

Cheers,

Vincent

 

Be that as it may, what does the barometer read when the altimeter is set to the 2181ft? What does the mission and/or ATC tell you what the altimeter setting should be?

 

I never noticed the altimeter being wrong in any way on Caucasus yet.

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It's a bug with starting on the runway, I believe. It also affects Caucasus, but there the error is only a few dozen feet.

 

The getBarometricAltitude() function returns 0 when you're at runway altitude, and the scaling at altitude is wrong if you start in this mode. If BST is using something like this internally, it may suffer from that as the root cause.

 

A cold start or parking hot start works correctly, I believe. It only affects runway starts.

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I don't know what is used on the NTTR map, but coming in for landing on the Caucasus map you get QFE from ATC. Maybe DCSW use QFE as standard?

Anyhow, if you don't like it, read the manual about how to set the barometer/altimeter and tune it to show airfield elevation before leaving the ground. As simple as that.

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Hi, Holton181 and somebody!

 

It's not the matter of liking it, it is the matter of realism. Question for you, the DCS uh-1h huey is the newer version of the uh-1h huey which have the radar altimeter which shows altitude AGL, right, and the uh-1 huey have a lot of variants, right? Thanks!

 

Cheers,

Vincent

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I guess having the altimeter adjusted to QFE is not that unrealistic, but having it adjusted to QFE where it can't be adjusted that way, is. In NTTR most, if not all airfields are off scale for QFE.

 

The good thing is that you can adjust it yourself, to your liking. :D

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... Question for you, the DCS uh-1h huey is the newer version of the uh-1h huey which have the radar altimeter which shows altitude AGL, right, and the uh-1 huey have a lot of variants, right?

...

 

I must admit I don't really understand the question here. What do the radar altimeter have to do with the main altimeter?

Radar altimeters are only supposed to be used for close-to-the-ground flying, giving you a fairly exact AGL value (i.e. your height, not altitude).

The baro altimeter is the main instrument for your vertical position. It will give you the altitude if QNH is set, and height AGL if QFE. But it will not give you an exact reading exept on ground, if air pressure is modeled correctly within DCSW. It doesn't give you an exact reading IRL. It's not it's purpose either.

 

About realism, having 0 on your altimeter is perfectly realistic, if QFE is used, witch seems to be the case with DCSW. But since the Huey is a western aircraft, it's altimeter has it's scale adopted for QNH mainly, witch may give you off-scale settings for the Kollsman window (your preasure setting, QNH/QFE) depending on location. But it's perfectly realistic behavior.

But I agree that on the NTTR QNH should be used. Guess it's a question for ED.

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Well, that question was a rhetorical question. The answer is: No, the radar altimeter has nothing to do with the main (barometric) altimeter. I don't need to be a Huey pilot to know that (I am a real life helicopter pilot though).

I'm sorry if I confused you.

 

You only mentioned the altimeter in your original post, and I and the other guys trying to help you assumed you ment the main (barometric) one. Then all of a sudden you start talking about the radar altimeter.

And just for notice:

1) The Huey isn't a modern helicopter.

2) All manned aircrafts, civil and military, old and modern, even aircrafts under development, MUST have certain instruments installed, including the ones belonging to the pitot-static system like the barometric altimeter. Even fighter jets, Airbus A380 and of course the Huey.

 

I suggest you do some googleing and read up on these things, especially the pitot-static system. The "International Standard Atmosphere" (ISA) is another good thing to know about as a pilot.

 

Over and Out

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I think the whole thing about the Radar Altimeter is that we already have one instrument that shows height above ground (at least at lower altitudes) and it is standard in the US to use QNH altitudes on our altimeter. Since this IS a US aircraft, it should be used that way and the default should at least set the altimeter to standard pressure (29.92) and adjusted from there.

 

I spend a lot of cycles of the knob to get it to the correct altitude as is since the knobs do not adjust more than a few hundred feet at a time with the mouse. Even using the keyboard is a slow adjustment. I have gotten used to it but it would be good if we can get at least an option in the settings to default to QFE or QNH would be great!

 

Just my two cents,

 

Highspeed

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...it would be good if we can get at least an option in the settings to default to QFE or QNH would be great!...

 

Indeed it would!

But the original question was expressed as there was an error about the altimeter, and we have tried to explain it's not and why. But my impression is that the OP can't really accept that. I might have gotten it wrong though.

 

Also, the QFE setting isn't nonsense even if equipped with a radio altimeter.

The barometric one is a completely different instrument than the radio one, they are used for different things and behaves differently.

The barometric is used mainly for vertical separation between aircrafts and to keep altitude. With the use of QNH it can also be used to keep safe above known obstacles and pronounced terrain features like hilltops.

The radio is for keeping a determined heigt above ground for sling loading etc. or flying low. "Radio altimeter" is actually a rather bad name for it, it doesn't measure your altitude. "Radio height meter" would be more correct.

 

A small simple test to demonstrate the difference:

Start at whatever airfield you like, preferably surrounded with uneven ground, with both altimeters reading zero.

Liftoff to an barometric altitude of like 200-300ft and keep it steady.

Watch the radio altimeter. It will change according to the ground, but you will still be at the same altitude.

I just flew around LAS, and while being east of the airfield I had negative altitude but was 350-400ft above ground...

 

But to your defense, it's not always possible to set the Kollsman window to the correct preasure value when QFE is used. Always at startup it will give you an altitude of zero, but fiddle with the knob and you might not get it back to zero...

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Thanks for you clarification as well Holton181. Great to have such good discussion. I always learn (and a good pilot is always a student) from such talks.

 

To that end, I do still prefer QNH setting on my altimeter as that gives me terrain clearance indications as you mentioned. Also, at 18000 (FL180) transition to standard pressure setting (29.92) is required (for bigger birds that can actually fly that high) so that is all the more reason to be flying the altimeter at indicated altitude instead of height above ground.

 

I realize that QFE is used in other parts of the world but it seems to me that outside of the immediate vicinity of the airfield it would not be providing me with any meaningful information as the terrain changes.

 

I do agree that there's not an error with the altimeter and understand that the OP might be giving that impression. I was just pointing out my understanding of his reference to the RA as a comparison not a tie-in.

 

Your description of the RA and altimeter differences with terrain changes is exactly why I like QNH on my altimeter. I just wish it could be adjusted more quickly or at least set closer to airfield elevation (as an option) and adjusted from there just like I do in my real world flying. (The last pilot set it to the then current barometric pressure which has now changed and I need to adjust for the changes.)

 

Thanks again for the wonderful discussion.

 

Highspeed

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And thank you Highspeed

I, too, like the QNH better for the same reasons as you.

/H


Edited by Holton181

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  • 1 year later...

This thread is old, but the problem still exists: The UH-1H is set by default at start up to the bottom of the Kollsman window scale, 28.10 inHg, in an attempt to have it set to QFE.

Suggested Solution: Provide a global preference setting in DCS for "Default to QFE" or "Default to QNH" or a 3rd option "Default to 29.92". Aircraft modules will then need to respect this option so that they default the aircraft's altimeter setting to the preference selected. Obviously, though, for NTTR the QFE setting is probably never going to work unless the Kollsman window scale in a non-US aircraft goes that far.

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  • 3 weeks later...

The Huey altimeter is working correctly. I think there's a bug in the weather parameters of the NTTR map or DCS World. I just checked all of the airports on the NTTR map using Quick Mission and they were all extremely low for those particular missions (I checked both summer and winter). They were well below 29.00"Hg, like near 26.00"Hg. Checking the other three maps I got settings for QFE above 31.00"Hg, but not by much. I used cloudy weather and didn't try using the other weather types to see if that had any effect on the pressure.

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