Altitude questions

[SonofEil]

Maybe this is the first time I've actually listened to ATC, but he keeps giving me an altimeter setting that sets airfield elevation zero, when he should be giving me sea level altimeter.

 

Second, also related to altitude I think: I'm now having a problem dropping bombs in CCIP. I think it happens when I try to drop bombs at a location with a significant altitude difference from my starting point.

Example: Campaign 1, Mission 1. I'm tasked to drop CBU-97's on a tank column, but when I get there I will never get a solid PBIL and the reticle never appears. I've tested the weapons system just after takeoff and I'll get a solid PBIL in the vicinity of the airfield, but once I get on target, it no work-y. I've tried approaches to target at different altitudes and pitches, but I am having no luck. I've been dropping bombs in CCIP successfully since beta 1, so what gives?!?!

[Qazme]

You want the airport elevation at 0 that way you know how high off the runway you are! If they gave you see level 2992 the it would read off from the actual elevation from the ground you are at, at the time.

 

As far as the PBIL and designations I've not had that issue. Post a track and maybe someone can help you out.

[SonofEil]

There are actually very few situations where a pilot would set their airfield elevation to zero (local aerobatics/airshow displays are all that comes to mind), and they certainly wouldn't get a current altimeter report from ATC saying a 1500ft. elevation airport is at 0ft. elevation.

[WildFire]

I believe they give you the setting in accordance with IMC conditions guidelines. If you were flying blind you would have your face placed squarely in front of the altimeter, HSI, and all the other analog instruments making sure your not hitting the ground. It does not matter what elevation (Edit* the airport*) is actually at, that is required information for the pilot before he ever leaves destination.

[EtherealN]

There are actually very few situations where a pilot would set their airfield elevation to zero (local aerobatics/airshow displays are all that comes to mind), and they certainly wouldn't get a current altimeter report from ATC saying a 1500ft. elevation airport is at 0ft. elevation.

 

"Very few" situations such as all aviation in all of Russia and the former soviet union? ;)

[lobo]

I believe they give you the setting in accordance with IMC conditions guidelines. If you were flying blind you would have your face placed squarely in front of the altimeter, HSI, and all the other analog instruments making sure your not hitting the ground. It does not matter what elevation (Edit* the airport*) is actually at, that is required information for the pilot before he ever leaves destination.

 

Well in North America (in the civilian world), you ALWAYS set your altimeter to read the airport elevation. You DO NOT set it so that it zeros at the field. In IMC you descend to the MDA or DA which is at field elevation plus the limits. Unless you are on a Cat II when DA is based off of radar altimeter which WILL zero at ground. I understand that this is not universal...

[bluepilot76]

QNH is altitude above sea level, and would mean that for example your altimeter would read 700feet on a runway that is 700feet above sea level. This is what is most commonly used around the world. AFAIK every civilian Instrument approach is calibrated for QNH. so the Decision Altitude (typically 200feet above runway threshold) for a runway at 700feet amsl would be on the plate as 900feet. I think this is what quincidence is referring to. HOWEVER, this is not civilian operations. Certainly the RAF use QFE for altimeter within the UK. In this case your HEIGHT is given above runway elevation, so you would set your altimeter to 0 on the runway, you would transition to QNH (altitudes) or standard pressure setting 1013mb / 29.92in for flight levels when away from the vicinity of your departure or arrival airfield.

However Im not sure what the RAF would do when they arrive somewhere with a high runway elevation, as they wouldnt be able to unwind enough millibars off the altimeters to reach 0feet. I think all the runways in this sim are relatively low though.

For the other problem, I think its related. There is something to do with the weapons system where it checks your height on takeoff and this information is somehow used for the bomb aiming process. I expect its explained in the manual, but have seen it mentioned on here a couple of times, thats something I cant help you with yet.

Edited June 5, 2011 by bluepilot76
spelling as usual.

[SonofEil]

"Very few" situations such as all aviation in all of Russia and the former soviet union? ;)

 

I learn things!!

Russian controllers, russian rules!

All i can say is those controllers in Nevada better shout out field elevation MSL!!

(My memory is also jogged that this isn't the first thread on the airport altitude debate! Apologies!)

 

Attached is a track of the actual problem I'm having. You can see that I'm unable to get a solid PBIL when approaching the target in level flight at around 1500 radar altitude. It also shows me successfully testing CCIP just after takeoff.

CCIP.trk

[EtherealN]

Georgia is included in "the former soviet union". ;)

 

Regarding the CCIP question, please ensure your systems are in DTS mode. See the following from the FAQ:

 

Q: Why do I sometimes get a CCIP INVALID message?

A: In order for the IFFCC to compute a CCIP solution, it must know the elevation under the CCIP pipper (gun, rocket, bomb, etc.). This can either be a HOT elevation based on the Steerpoint elevation, or DTS elevation stored in the digital map database system. If not in DTS and the steerpoint is at a higher elevation than the CCIP pipper, you will get a CCIP INVALID message. Unless you have a DTS failure, you should always use DTS, as indicated on the HUD in the data block. If you do not see DTS, press the DATA rocker on the UFC and then the SEL rocker until DTS appears.

 

http://forums.eagle.ru/showthread.php?t=67747

[BlueRidgeDx]

If the US were fighting a war in Georgia, it's a safe bet that USAF Combat Controllers would be zipping around on the airfields on ATV's, giving US standard phraseology; or there would be no ATC at all. I doubt seriously that civilian Georgian controllers would be handling ATC.

 

You don't need QFE when you have a radar altimeter to tell you how far off the ground you are. Further, charted features such as MSA's, obstructions like cell phone towers and such, as well as mountainous terrain are all depicted in MSL. So if you set your altimeter to QNH, you have an immediate reference for comparing your altitude to these values. Not so much with QFE...

 

The adoption of Soviet/Russian/Georgian practice is a concession of reality. Not really a big deal in Eastern Europe, but it hopefully will not exist in CONUS.

[EtherealN]

I doubt seriously that civilian Georgian controllers would be handling ATC.

 

The scenario is unlikely, this is a bit of a nitpick, and I don't know if this doctrine is used by Georgia as it is used here, but at least over here there is no such clear demarcation between "civilian controllers" and "military controllers". All controllers are trained for the military role such that, in the event of a war, they can handle the military flights.

 

You don't need QFE when you have a radar altimeter to tell you how far off the ground you are.

 

Only true on flat terrain. Remember what happened to the plane carrying the polish president.

 

SlackerD, nice find, I'll have to dig up the AIP at some point and check it out.

[BlueRidgeDx]

True on all accounts, EtherealN.

 

I'm just pointing out that there's no reason to set the barometric altimeter to field elevation when you have a radar altimeter that does that for you automatically. Neither one will save your bacon in mountainous terrain.

 

In the classroom, I use several CFIT accidents similar to the one you mentioned in order to highlight SA and CRM concepts.

 

Interesting about the civilian/military controllers in Georgia. I wasn't aware of that.

 

@Slacker, I made the point about the QNH standard many moons ago (before I was invited onboard as a tester), and I think I linked to (or at least referenced) the Georgia AIP back then. It turned into a flame war, so I let the issue go. It does deserve attention, though.

Edited June 6, 2011 by BlueRidgeDx
i no spell no good

[SonofEil]

Regarding the CCIP question, please ensure your systems are in DTS mode. See the following from the FAQ:

 

Ahhh, the FAQ. I'll admit, it's been a while since I've visited that dusty tome of knowledge!

I'll give it a fresh scour tonight. (I did check the manual, ran through a bunch of different user checklists and performed a forum search before posting though, so I'm not a total dirtbag!)

As for the answer, it certainly sounds like that could be the cause my problem. I'll give the DTS a look when I get home from work.

Thanks!

 

...I made the point about the QNH standard many moons ago (before I was invited onboard as a tester), and I think I linked to (or at least referenced) the Georgia AIP back then. It turned into a flame war, so I let the issue go. It does deserve attention, though.

 

Yeah, it's not a big deal to me. I'll just go back to ignoring the controller and setting my altimeter to the published field elevation.

[bluepilot76]

If anyone wants to use QNH instead of QFE it is easy enough to convert it yourself. 1mb (hPA) equals 30feet (rule of thumb), so if ATC gives you QFE 1002 at an airfield with 500ft amsl, all you need to do is divide 500 by 30, approx 17. so ADD 17 mb onto 1002, hey presto QNH 1019.

 

Not having the sim to hand, can anyone confirm that the airfield altitude is given on the DIVERT page?

[Kaiza]

Sure is

[159th_Viper]

 

Not having the sim to hand, can anyone confirm that the airfield altitude is given on the DIVERT page?

 

No - CDU DIVERT page contains waypoint number, waypoint identifier, magnetic heading and range, and TTG for the 4 closest divert airfields.

[Kaiza]

No - CDU DIVERT page contains waypoint number, waypoint identifier, magnetic heading and range, and TTG for the 4 closest divert airfields.

 

Errr yeah true. Once you select the airfield the elevation comes up with the airfield data.

[SonofEil]

Just as an update, it looks like my problem was that I was using steerpoint altitude, which was zero, instead of DTS altitude. Thanks for the heads-up EtherealN.

I've also checked other missions, and it looks like I've just been getting lucky this whole time with my bomb drops! None of them have been using DTS altitude!

Soooo, back to the books!