Q Codes

ppragman

FLIPY FLAPS!
Really? You don't see the danger of only knowing your absolute altitude relative the airport but no other terrain? You can do the math, but that could be an awful lot of math as it's constantly changing.
And realistically given cold weather corrections, it could legit be scary in mountainous areas. In Siberia with relatively "short" mountain ranges with a fairly low transition altitude I think QFE makes perfect sense, especially with limited infrastructure because once you get close just use the radar altimeter for everything, but with lots of mountains... there could be pretty significant issues, especially on off airway routings down low.
 

z987k

Well-Known Member
And realistically given cold weather corrections, it could legit be scary in mountainous areas. In Siberia with relatively "short" mountain ranges with a fairly low transition altitude I think QFE makes perfect sense, especially with limited infrastructure because once you get close just use the radar altimeter for everything, but with lots of mountains... there could be pretty significant issues, especially on off airway routings down low.
It's about as dumb as having your transition altitude/level at 5000, but terrain within 50 miles is close to 18k. How high are we above the terrain? Um, well let me get my calculator out and the VFR chaaaaa oh ya don't have those so no one knows.
Situational awareness is by design very low in these instances. Which is dumb.
 

dustoff17

Well-Known Member
The "Q's"!
We used these in the Army but called these RAT(T?) codes. It's an acronym but I can't for the life of me remember what it stands for...…..I hate getting old.
 

Stone Cold

Well-Known Member
It's about as dumb as having your transition altitude/level at 5000, but terrain within 50 miles is close to 18k. How high are we above the terrain? Um, well let me get my calculator out and the VFR chaaaaa oh ya don't have those so no one knows.
Situational awareness is by design very low in these instances. Which is dumb.
99.9% of the places I've flown into with QFE were relatively flat. The ones that weren't, well, you're only below transition for a short time. Then, you're on QNE...and all on the same pressure plane, all with the same information.

If you had said the altimeter setting only goes so high, I would have given you internet points for that, but just because you say the terrain goes high, and you'd have to pull out VFR charts, well wouldn't the same apply to QNH? You have a MSA in the terminal environment, and after the TA/TL you are on QNE, so you're never on QFE long enough to deal with the mountains outside of the MSA. Usually, it's a low TA/TL, so everybody is on the same pressure plane after your transition. Think about this...in the US, you could have converging traffic, one talking to one sector, one on another with different altimeter settings all the way up to 18,000'. I prefer to have everybody on the same setting while in the lower altitudes. You're not going to be doing QFE ops in the rockies, well, because the baro setting would be too low.
 

z987k

Well-Known Member
99.9% of the places I've flown into with QFE were relatively flat. The ones that weren't, well, you're only below transition for a short time. Then, you're on QNE...and all on the same pressure plane, all with the same information.

If you had said the altimeter setting only goes so high, I would have given you internet points for that, but just because you say the terrain goes high, and you'd have to pull out VFR charts, well wouldn't the same apply to QNH? You have a MSA in the terminal environment, and after the TA/TL you are on QNE, so you're never on QFE long enough to deal with the mountains outside of the MSA. Usually, it's a low TA/TL, so everybody is on the same pressure plane after your transition. Think about this...in the US, you could have converging traffic, one talking to one sector, one on another with different altimeter settings all the way up to 18,000'. I prefer to have everybody on the same setting while in the lower altitudes. You're not going to be doing QFE ops in the rockies, well, because the baro setting would be too low.
So QNE isn't very intelligent below terrain either. Flying pressure plains is bad for terrain clearance unless you're just so far above it the local pressure would have to be something that just doesn't happen on this planet. Like in the power 48 where it's 4k between the highest peak and QNE. Up north, where many peaks go into the flight levels and pressures can get both really high and low, it makes flight levels unusable at times through 250. That works because you'll be in ATC contract at those altitudes and that can route you around or advise a climb, but even then, I think the transition in those areas should be at least FL220.
The reason being, is if you are relying on ATC solely to keep you from hitting the rocks, you're doing it very wrong. You need to be able to know not only exactly where you are but how far above the terrain you are currently over, headed towards and is just in your general area. If you are in QNE below terrain, you have almost no way of knowing your height relative terrain. If you are in QFE, you only know your height above the airport, and would need figure out the difference between airport elevation, mountain peak elevation and then just general elevation of the area relative the airport as well. I guess they could publish approach charts with heights relative the airport rather than sea level, but barring that it's quite the extra step to keep the same situational awareness that you easily get with QNH.

It's not a big deal if ATC is perfect. But that's not how anyone operates, we trust, but verify every single altitude and heading right? Especially with foreign controllers where you'll encounter QNE below terrain.
 
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