Good luck with that!

Not by any means relying solely on typical equipment in your airplane.

Test flights use calibrated air data booms or trailing static cones to do this.

FAA uses 3 different monitoring methods:

GPS Based Monitoring Unit (GMU), which collects data and is post processed AFTER the flight to determine what the ASE was.

Aircraft Geometric Height Measurement Element (AGHME), which are a few specific locations across the country with ground based means to measure height. RVSM aircraft were required to fly by one of them every 2 years under certain circumstances to maintain RVSM status.

And now ADS-B Height Monitoring, a real time monitoring using ADS-B geometric and baro heights.

Here is more info

https://www.faa.gov/air_traffic/separat ... ssions.pdf


Without a model of the current atmosphere around you, you can't do it in the cockpit. Your pressure height is basically the weight of the air below you and that varies with temperature, altimeter setting, and even the speed of the air movement.

Mike C.

Not by any means relying solely on typical equipment in your airplane.

Test flights use calibrated air data booms or trailing static cones to do this.

FAA uses 3 different monitoring methods:

GPS Based Monitoring Unit (GMU), which collects data and is post processed AFTER the flight to determine what the ASE was.

Aircraft Geometric Height Measurement Element (AGHME), which are a few specific locations across the country with ground based means to measure height. RVSM aircraft were required to fly by one of them every 2 years under certain circumstances to maintain RVSM status.

And now ADS-B Height Monitoring, a real time monitoring using ADS-B geometric and baro heights.

Here is more info

https://www.faa.gov/air_traffic/separat ... ssions.pdf


Without a model of the current atmosphere around you, you can't do it in the cockpit. Your pressure height is basically the weight of the air below you and that varies with temperature, altimeter setting, and even the speed of the air movement.

Mike C.

For a pre 1997 certified airplane without TCAS:

1. Two independent altitude measuring systems (may imply two static ports as well as two altimeters).
2. AP holds altitude +/- 130 ft in smooth air.
3. Altitude alerter +/- 300 ft.
4. ADS-B 1090ES.

The ASE statement is NOT an equipment requirement, but an OPERATIONAL one.


I don't think you need to query ATC at all. Get the equipment required and go fly. If your ASE is off, ATC will tell you and clear you out of RVSM airspace.

That's what the rule implies as I read it.

Mike C.

Thanks Mike, that's my read as well! Now we get to see how it is applied.

Not clear when this doc was written, but it kind of implies they are keeping a database of altimetry data for individual aircraft, see page 19 talking about a statistical process and QC monitoring. It also talks about RVSM approvals database. It does not say what it would take to get the approval via any new ASE/ADSB monitoring system, but it implies there may be some process.

BUT - no idea how old this doc is. It could be referring only to the “old” system of RVSM approval.

Just for fun I sent a request to AOPA to see what they had to say about it. This is the response I got:

Hello John,

Thanks for your patience on this. I brought your issue to my co-worker in our Washington D.C. office because he works more closely with the FAA on issues such as this. He wasn't able to get to consult with the FAA due to the government shut down but was able to discuss it with GAMA and NBAA. It is our agreement that the aircraft certification requirements will remain the same, the rule change only changes the need for an LOA if the aircraft is equipped with a certified ADS-b and does not change the other equipment requirements that would be needed to bring the aircraft into RVSM compliance, such as through the applicable appropriate Service Bulletins (SB), Service Letters (SL), Engineering Change Orders (ECO), or Supplemental Type Certificates (STCs). The best way to answer your question about legacy aircraft is if your aircraft is not certified to fly in RVSM airspace currently, getting ADS-b will not change that, it would still need to meet all the RVSM equipment requirements spelled out in Appendix G to Part 91 Operations in RVSM airspace. I hope that answers your question, feel free to contact us if you have more questions or comments.

Fly Safe!
Mark Milkovitz
Senior Aviation Technical Specialist, AOPA Pilot Information Center

...which includes an entirely new section 9 which DOES NOT use section 2 and 3 covering AIRCRAFT and OPERATORS.

Section 9 has a simple list of equipment you must have. No RVSM certification.

If the FAA meant the new rule to require the OLD way, they would have written it to REQUIRE the section 2 AIRCRAFT approval.

It does not.

It says that VERY clearly in the opening sentence of the OLD way:

Section 2. Aircraft Approval

(a) Except as specified in Section 9 of this appendix, an operator may be authorized to conduct RVSM operations if the Administrator finds that its aircraft comply with this section.

In section 9, there is no "Administrator" language. This means no RVSM certification.

Section 9. Aircraft Equipped With Automatic Dependent Surveillance—Broadcast Out

An operator is authorized to conduct flight in airspace in which RVSM is applied provided:

(a) The aircraft is equipped with the following:

(1) Two operational independent altitude measurement systems.

(2) At least one automatic altitude control system that controls the aircraft altitude—

(i) Within a tolerance band of ±65 feet about an acquired altitude when the aircraft is operated in straight and level flight under nonturbulent, nongust conditions; or

(ii) Within a tolerance band of ±130 feet under nonturbulent, nongust conditions for aircraft for which application for type certification occurred on or before April 9, 1997 that are equipped with an automatic altitude control system with flight management/performance system inputs.

(3) An altitude alert system that signals an alert when the altitude displayed to the flight crew deviates from the selected altitude by more than—

(i) ±300 feet for aircraft for which application for type certification was made on or before April 9, 1997; or

(ii) ±200 feet for aircraft for which application for type certification is made after April 9, 1997.

(4) A TCAS II that meets TSO C-119b (Version 7.0), or a later version, if equipped with TCAS II, unless otherwise authorized by the Administrator.

(5) Unless authorized by ATC or the foreign country where the aircraft is operated, an ADS-B Out system that meets the equipment performance requirements of § 91.227 of this part. The aircraft must have its height-keeping performance monitored in a form and manner acceptable to the Administrator.

(b) The altimetry system error (ASE) of the aircraft does not exceed 200 feet when operating in RVSM airspace.

If anyone says the new rule requires section 2 aircraft approval process to fly in RVSM airspace, they are reading it wrong.

Mike C.

And yet in the comments section, the FAA says:

One commenter stated the use of ADS–B technology will deconflict aircraft within RVSM airspace without the need for expensive altimetry instruments. The FAA notes that for an aircraft to be eligible for operations in RVSM airspace it must meet strict height-keeping performance standards. ADS–B Out provides information used to determine an aircraft’s ASE. ADS–B alone does not provide operators with the requisite height-keeping capability to conduct operations in RVSM airspace safely. Accordingly, the installation of a qualified ADS–B Out system in an aircraft that does not have the altitude keeping capability necessary to meet RVSM performance requirements would not permit that aircraft to operate in RVSM airspace.

Altitude keeping cabability is part of the RVSM cert. The new rules do not remove that cert requirement.

Show me where the rules require it.

The new rule says you may operate in RVSM airspace if:

(2) The aircraft—

(i) Has been approved and complies with Section 2 this appendix; or

(ii) Complies with Section 9 of this appendix.

Section 9 is just the list of equipment you need, note the lack of the word APPROVED. Section 9 aircraft do NOT need to be approved.

Mike C.

And yet in the comments section, the FAA says:

One commenter stated the use of ADS–B technology will deconflict aircraft within RVSM airspace without the need for expensive altimetry instruments. The FAA notes that for an aircraft to be eligible for operations in RVSM airspace it must meet strict height-keeping performance standards. ADS–B Out provides information used to determine an aircraft’s ASE. ADS–B alone does not provide operators with the requisite height-keeping capability to conduct operations in RVSM airspace safely. Accordingly, the installation of a qualified ADS–B Out system in an aircraft that does not have the altitude keeping capability necessary to meet RVSM performance requirements would not permit that aircraft to operate in RVSM airspace.

Altitude keeping cabability is part of the RVSM cert. The new rules do not remove that cert requirement.

There's nothing you can do to be sure your ASE is within bounds before you go fly in RVSM airspace, EVEN for aircraft with RVSM kits approved under the old section 2 method.

The ASE is a requirement for OPERATING in RVSM airspace. A real time, in the moment check of your ASE. You can't do that on board, ATC can do that with the FAA algorithms.

I think this will be much like a mode C stop squawk ATC command. Your mode C differs from your real altitude by too much, so they command you to stop mode C squawk. For RVSM, it would be cleared out of RVSM airspace (FL280 or FL430).

Mike C.

There's nothing you can do to be sure your ASE is within bounds before you go fly in RVSM airspace, EVEN for aircraft with RVSM kits approved under the old section 2 method.

The ASE is a requirement for OPERATING in RVSM airspace. A real time, in the moment check of your ASE. You can't do that on board, ATC can do that with the FAA algorithms.

I think this will be much like a mode C stop squawk ATC command. Your mode C differs from your real altitude by too much, so they command you to stop mode C squawk. For RVSM, it would be cleared out of RVSM airspace (FL280 or FL430).

Mike C.

Maybe, maybe not.

Most of the folks talking about the new RVSM method are trying to get just into the low 30s. They are like MU2s certified to FL310 for which no RVSM STC exists and probably never will. In those cases, we're not talking about much of an extra altitude step and the basic instruments might do it. We are only talking about 10% thinner air.

For the aircraft that go into the low 40s, very different story, much harder. But then, those do have RVSM equipment you can buy, so you can get it installed and then go fly under the new rules. Most will already meet that requirement since they are almost all section 2 aircraft by now anyways.

Mike C.

I ran some numbers assuming your altimeter has a constant error in pressure.

A 200' error at 310 is the equivalent of a 179' error at 280.

A 200' error at 350 (for a 441 say) is equivalent to a 153' error at 280.

Assuming I did my math right and my constant pressure error assumption is a good one, if you can be within 100' at 280 you can be within 200' at 350.