Must be. Note 1. says you need their permission to use it.Is that the Honeywell developed approach for ASE?
Must be. Note 1. says you need their permission to use it.
Density altitude isn’t a limit for an approach procedure, AFAIK. Its Rob ably above the performance limit for a lot of airplanes, but that would be determined from airplane charts, not the approach procedure itself.The DA for the procedure is 8274. With a temp of 46C the density altitude is like 14,000 feet.
Density altitude isn’t a limit for an approach procedure, AFAIK. Its Rob ably above the performance limit for a lot of airplanes, but that would be determined from airplane charts, not the approach procedure itself.
Wouldn’t the other approaches have the same limitation?IAS vs TAS.
Ok, I give. What’s your explanation for the restriction?Wouldn’t the other approaches have the same limitation?
Ok, I give. What’s your explanation for the restriction?
RNAV (RNP) approaches, like the LNAV/VNAV line of minima on RNAV (GPS) approaches, use barometric altimetry for calculating a glidepath. As you learned in your Private Pilot ground school, altimeters are affected by non-standard temperature. With a high temperature, it means the aircraft will be higher than the indicated altitude. So if the FAF is charted at 3000, on a hot day you may actually be at, say 3300 True altitude. This means that your descent to the runway will be steeper. At some temperature, that descent to the runway can exceed the limits for an approach for the highest Category aircraft charted on the procedure. For example Cat D on most procedures. The maximum glidepath angle for Cat D is 3.50 degrees. Therefore, at or above some temperature, the actual flown GPA will exceed 3.50 degrees, and the approach is NA above this temperature.
Now, lots of notes:
- The limit used to be 3.10 degrees for Cat D. Many procedures still have temperature limits based on 3.10 deg. Just in case you're doing math.
- When the limit changed to 3.50 degrees, it would actually take a really high temperature to exceed 3.50 deg on a procedure designed for a nominal 3.00 deg. The maximum charted temperature by policy is 54 deg C, which effectively makes it a non-issue for most procedures, as 54 C is 129 deg F.
- The note reads "For uncompensated Baro-VNAV systems...". If your system is compensated, the limits do not apply.
- EVERY (*) RNAV (RNP) procedure in the U.S. will have a similar note. And ALMOST EVERY RNAV (GPS) procedure with an LNAV/VNAV line of minimums will have a similar note too, because the temperature reasons and criteria are almost identical.
* There's always an exception I suppose, but I don't know of any.
Sorry, I reject your explanation. High temps does = high altitude, but it doesn’t effect the safety of the approach. If you are high at the FAF due to temperature, you will also be high at DA. When temps are very cold, this presents a safety issue.
Except that the error starts at ground level, not sea level. 47 degrees above ISA x 4 =188 feet per thousand, and DH is just over 500 feet, for an error of about 90 feet.The correction is 4ft per 1°C difference from ISA per 1000ft
So isa temp should be -1°c. So for 46°c you have a difference of 1500ft at the minima and 2000 at the FAF
For others following along, the error starts at reporting station's elevation because the reported altimeter setting has already accounted for the error due to non-standard temperature from sea level up to field elevation. It is only when you continue above the reporting station's field elevation that indicated altitude starts to diverge from true altitude again.Except that the error starts at ground level, not sea level.
For others following along, the error starts at reporting station's elevation because the reported altimeter setting has already accounted for the error due to non-standard temperature from sea level up to field elevation. It is only when you continue above the reporting station's field elevation that indicated altitude starts to diverge from true altitude again.
High temp isn’t going to get you to close to the rocks like low temp can. Getting too close to the rocks is a definite safety issue. But the high temp thing could be too. It can be argued that creating a situation where a pilot will have to fly extreme rates of descent to get down is a safety issue. Yeah, the pilot shouldn’t fly rates of descent that can get him in an unsafe situation. But why create an Approach where he is probably going to have to make that decision to descend at extreme rates of descent to get down.Sorry, I reject your explanation. High temps does = high altitude, but it doesn’t effect the safety of the approach. If you are high at the FAF due to temperature, you will also be high at DA. When temps are very cold, this presents a safety issue.
So, at the FAF which is maybe 1500 feet above the airport, the error may be a couple hundred feet on a really hot day.
I wouldn't worry too much. Many pilots have only a cursory understanding of altimeter errors. I didn't fully understand it until I was an ATP with nearly 8,000 hours. It's not something that came up very often, except in areas with extremely cold temperatures, before RNAV/VNAV approaches became common.Thats the problem with coming from a small country with the max elevation is 2277ft