I'm going to throw a new question out there.

I would like to - very occasionally - fly to Canada/Mexico. I am currently doing Section 9 domestically. I am starting down the path of getting an RVSM LOA, which I have viewed as a one-time paperwork exercise. BUT - maybe I should consider whether it causes me any exposure that I don't want. In particular, this quote from Jim's excellent Q&A post above.


So if I get an LOA, I'm no longer under Section 9, I guess. Does this mean I have to do things I don't do currently?

Actually, an interesting way to think of it is the converse. My RVSM airworthiness is part of the aircraft inspection program currently. Under section 9, since performance is all that matters, could I skip that inspection and still be legal? And by going LOA then be again required to do that inspection regime?

This is academic to me. But gets at the heart of what kind of change Section 9 as a "performance standard" really implies.

Wow, that is a surprising answer. Do they plan to clarify this in writing?

Agreed that Section 9 is vague (and it is the rule), but AC 91-85B is pretty clear that it should certified (ACs are guidance, not rules). I don't see how that could be construed as allowing just flying in RVSM airspace.

The other thing to consider, is Jim's plane may not be too far off in ASE error to be out of bounds, but many other aircraft won't meet the performance rules of +-200'. My TBM at FL290 has an SSEC correction of about 130' and the tolerance at the 2 year check is up to 72' beyond that each way. So if I tried to fly RVSM without the RVSM SB applied then I could be extremely close to the limit. If I used standard Part 43 Appendix E altimeter limits I could be well beyond it.

Do you know what the P-180 SSEC curve looks like? It may be even more extreme.

Something still smells fishy to me. It wouldn't be the first time one branch of the FAA doesn't have a clue about the can of worms they are opening.

Absolutely. There's no doubt I got lucky with a low ASE. It's possible that the B200 one serial number away from mine has an unacceptable ASE.

BTW, I also got lucky that they revealed my ASE to me - their policy is not to reveal individual ASEs in order to cut down on the volume of communications. I already had ongoing email communications and someone let it slip. They also decided they couldn't publish ASEs across the board for privacy reasons, and they are technically blocked from doing the green/yellow/red system.

So it's possible you could have a first flight with an error of 199' and get on the list, and then have a 201' error and fail on your next flight. The system isn't perfect. If you really want to sleep well, an engineering firm may be your best bet.

No idea. But the Piaggio is RVSM certified, so… kind of moot to me. And domestically I’m fine with operating under section 9 (i.e. without LOA). But I want to include the possibility of Canada/mexico. So i guess i need a LOA.

But Jim’s post made me wonder whether the Section 9 changes made other changes possible. While I’m not advocating skipping airframe inspections, it is an example of the kinds of legal hoops that the Section 9 change might affect. And also whether if i get an LOA whether it would impose requirements that i do not have now. Not that I know of any, but it does open the question.

Bravo, Jim! Outstanding!That explains so much! The confusion is deliberate, bureaucrats that lost the argument trying to scare everyone away from doing what they lost the fight to prohibit.

Key phrase "evaluation by the operator".

I don't see the word "certified" in what you posted, which would imply evaluation by the FAA.

Mike C.

Brilliant.

Nothing like the hard truth. Thanks for doing that.

The rule is very clear, meet PERFORMANCE objectives and you can FLY in RVSM airspace. You don't need to be certified. The reason it SEEMS like you need to be certified is that the part of the FAA that puts out guidance wanted it to be that way, and thus they insinuate that it is required without actually stating that CLEARLY. Thus they are obfuscating the fact you don't need to be certified.

Most ASE errors flagged by the FAA are certified systems, BTW. The usual issue is some fault in the system that needs to be corrected (static leak, bad sensor, etc). Airliners regularly show up on the list.

Here is a presentation on the ASE "Watch List":

https://www.faa.gov/sites/faa.gov/files ... ist%20.pdf

The advent of ADS-B makes the RVSM system VASTLY safer than the periodic AGHME station test method that was used before. Now you have real time, accurate, checking of ASE.

There is a way you can compare your ASE to other aircraft. Using an ADS-B tracker like adsbexchange, find the time your airplane was flying. Note the GPS altitude and the reported baro altitude. Now find airplanes at your altitude nearby at around the same time. Compare their baro and GPS altitude to yours. If you end up having similar offset of baro to GPS altitude, then your ASE is pretty good.

Some may argue this is only a relative test, but ultimately, the ability to not hit each other is a relative outcome. Indeed, I believe the FAA monitoring relies on the ability to average a large number of planes to get "truth" and then compare individuals against that average.

Mike C.

Interestingly, there have been several statements to the effect it is not truly real-time (albeit still timely enough to enhance overall safety). The watch list presentation supports that. On the “Conclusions” page it states “ASE analysis cannot be conducted solely through automation.” Unclear whether it’s referring to the case by case analysis in there or broader analysis too.

I wonder whether that has evolved since that presentation.

It is continuous, but not real-time.

The RVSM approval list that is available today only includes data from flights up to and including October 31.

That presentation is for AGHME monitoring, not ADS-B

What a great idea Mike!

https://www.flightradar24.com/ has a good playback tool (on bottom center toolbar).
I believe you need an account to go back more than a few days. You need the date and time you were flying, and then you'll need to find your plane on the map.

The quickest way I've found to find the exact time and location on a flight is with https://globe.adsbexchange.com/.
Search your tail number on the right side. On the left side click the + beside history and start scrolling through previous days. You can then click on the flight path and put the plane where you want to get the time stamp at that exact position. Take the date and time to flightradar24 and it's easy to pick out your plane on the map. Change the playback speed to 1x and start clicking on planes around you. Sometimes it takes a minute for the gps altitude to populate.

You may be able to do all of that with only adsbexchange, but I haven't figured out how.

You can arbitrarily replay tracks using:

https://globe.adsbexchange.com/?replay

At the bottom is date, hours, minutes, and playback speed, so you can pick any time and any place to playback the history.

For example, here is my departure from KSRQ this past Sunday:

https://globe.adsbexchange.com/?replay= ... 59&zoom=10

You can also filter the display for altitudes, say I do that for FL390 to FL410 and then watch my last flight.

I went to somewhere in middle GA and saw my plane cross under N250AD. The numbers were:

N250AD: FL410 (baro), 42,250 ft (GPS)
N618K: FL400 (baro), 41,175 ft (GPS)

The baro difference was 1000 ft, the GPS difference was 1,075 ft. Given the true altitudes were higher by 3%, a perfect true altitude difference would have been 1,030 ft, so my altimetry compares very nicely to the reference airplane, less than 50 ft error. We are not going to hit.

You do this for a number of airplanes near you on your route and you will develop a pretty good sense of how your altimetry is working compared to the norm. In some sense, you are doing what the FAA is doing on a wider scale.

My plane appears in the monitored list as well, of course.

Mike C.

DOH! Missed that detail, thanks. So perhaps the ADSB monitoring lends itself to better automation.

Uh, I am missing where the 3% comes from?