As far as I can tell, TCAS II isn’t an option on the SF50.
This would support the theory that RVSM equipment requirements have changed.

Makes you wonder if the SF50 G2 announcement may have been correlated with the change in RVSM requirements.

TCAS II has never been required for RVSM.

The only requirement is *IF* you have TCAS II, it has to be version 7.0 or later.

For example, Cessna 441 can be RVSM (about 15% of the fleet has it). I doubt any of them have TCAS II.

The reason TCAS II version 7 is required is that TCAS II produces automated resolution advisories (RAs). The software in the two planes figures out how to avoid a conflict. In RVSM airspace, you need version 7 since it fixes certain RA issues that were deemed important to operate in RVSM.

If you have any other form of TCAS (TCAS I, TAS, etc), those do NOT produce RAs, thus are not a concern in RVSM airspace. They merely provide traffics advisories (TAs).


Doubt it.

Mike C.

Static Source Error Correction is a big part of ASE. A great example would be a TBM. The ports are on a flat spot at the back of the fuselage. The SSEC curve at 29,000 feet is very sharp. At 120 KIAS the correction is 77 feet. Bump airspeed to 150 and the correction jumps to 113 feet. Correction at 300 KIAS is 447. A mechanical altimeter cannot adjust for airspeed and is therefore clearly not accurate enough.

You can guess all you want, but without the actual data you really don't know if your airplane is good to go in RVSM airspace.

Static Source Error Correction is a big part of ASE. A great example would be a TBM. The ports are on a flat spot at the back of the fuselage. The SSEC curve at 29,000 feet is very sharp. At 120 KIAS the correction is 77 feet. Bump airspeed to 150 and the correction jumps to 113 feet. Correction at 300 KIAS is 447. A mechanical altimeter cannot adjust for airspeed and is therefore clearly not accurate enough.

You can guess all you want, but without the actual data you really don't know if your airplane is good to go in RVSM airspace.

The SSEC for a Mustang is actually really low. At 30,000 feet and 180 KIAS the correction is only 21.8 feet. 235 KIAS correction is 41.6. It makes sense since that aircraft was designed in the RVSM era.

Most of the older airplanes as designed have an ASE greater than 200 feet. Without SSEC data and an air data computer to compensate, previously non-compliant airplanes are still non-compliant.

At FL290, that's 459 knots true. Mach 0.78. Definitely getting into compressibility effects which is why the static ports go wonky at that point. That's the divergence you are noting, operating at high mach numbers.

No TBM does that speed, however.

AC 91-85A says upper speed for testing ASE is speed limited by cruise thrust. For TBM, that's about 210 KIAS, 328 KTAS, Mach 0.56. Very different when it comes to compressibility effects.

Mike C.

At FL290, that's 459 knots true. Mach 0.78. Definitely getting into compressibility effects which is why the static ports go wonky at that point. That's the divergence you are noting, operating at high mach numbers.

No TBM does that speed, however.

AC 91-85A says upper speed for testing ASE is speed limited by cruise thrust. For TBM, that's about 210 KIAS, 328 KTAS, Mach 0.56. Very different when it comes to compressibility effects.

Mike C.

Here is the response I got from my PAI(Principal Avionics Inspector)after I showed him the new regulation.


Mr. Witt,

I have reviewed the information you supplied. You are correct, you no longer need to apply for Authorization to operate in RVSM. However, you do have to meet all the requirements to operate in RVSM airspace. The systems required to operate in RVSM airspace still have to be in full operation and ICA's complied with. This just removes the requirement to apply to operate in the airspace.

If you have any more question in this or any other matter, feel free to give me a call.

I agree with all that.

Section 9 gives the requirements to operate without approval. The equipment has to be maintained and functional.

Mike C.

One other note on this subject. All of this is for U.S. Domestic Airspace only. You will still need a Letter of Authorization to overfly Canada, The Caribbean, Gulf of Mexico, etc.

The Draft AC referenced above talks about this in Ch. 4, Sec. 4.3. Without pasting it all, some tidbits that seem relevant (but there's a decent amount, one should read it oneself if interested):

4.3 Height-Keeping Performance Monitoring For RVSM Aircraft Equipped
With ADS-B Out. The goal of height-keeping performance monitoring is to
ensure safe and efficient operations and determine aircraft compliance on an
ongoing basis.
...
4.3.3 Aircraft equipped with qualified ADS-B Out systems will be height
monitored during normal operations at RVSM altitudes when operating in airspace
where sufficient ADS-B data is available to the FAA to determine RVSM performance.
...
4.3.5 The height-keeping performance must be monitored as follows:

1. The initial RVSM operation of an aircraft must be in airspace where sufficient
ADS-B data will be collected for the FAA to evaluate RVSM performance.
...

2. The aircraft’s height-keeping performance must have been monitored within
the previous 24 months in airspace the FAA can monitor the aircraft ADS-B
Out signal and found to be in RVSM compliance.

3. The aircraft must continue to meet the height-keeping performance specified
in part 91 appendix G, section 9(b).

4.4 RVSM Height-Keeping Performance Website. U.S.-registered operators may obtain
monitoring performance from the FAA height-keeping performance website at
https://www.faa.gov/air_traffic/separat ... ds/naarmo/.

4.4.1 If the operator does not meet the monitoring requirements specified in paragraph
4.3.5, the operator must file as non-RVSM aircraft until the issue is resolved. Common
resolution actions include:

Basically, the FAA states that they have some kind of monitoring in place and the operator can get the results of that monitoring (and is supposed to do so periodically). This seems conceptually like the request for ADS-B compliance report that they have available for ADS-B equipment. That said, they imply one is somehow supposed to be compliant before initial flight in RVSM airspace.

To test the ASE, it seems like a procedure for the FAA to allow a one-time, monitored flight into RVSM airspace for the purposes of generating their monitoring report would be easy to implement and ultimately the most definitive, but they don't outline such a procedure. Somehow the aircraft is expected to be RVSM compliant, including the ASE since that's part of the section 9 performance spec, before the initial RVSM flight. It does not state that one must have any specific form of certification of meeting that performance spec, only that one must do so. Perhaps today's RVSM equipment testers could simply run the equivalent of a pitot-static system test on an aircraft and see if it meets requirements.

For now.

As the world builds out ADS-B, one can imagine this changes.

Mike C.

1. The initial RVSM operation of an aircraft must be in airspace where sufficient ADS-B data will be collected for the FAA to evaluate RVSM performance.

I think that's the key step.

Check off you meet the section 9 equipment list, then have an initial flight in RVSM airspace with sufficient ADS-B monitoring. That would be most anywhere in the CONUS one would think.

Then you check how you did and if aren't good, stop going into RVSM:

4.4 RVSM Height-Keeping Performance Website. U.S.-registered operators may obtain monitoring performance from the FAA height-keeping performance website at

https://www.faa.gov/air_traffic/separat ... ds/naarmo/.

4.4.1 If the operator does not meet the monitoring requirements specified in paragraph 4.3.5, the operator must file as non-RVSM aircraft until the issue is resolved.

So they seem to allow for the fact a flight might come back as non compliant.


Section 9 says you need a list of equipment that meet certain criteria. I don't think it says you must prove, prior to flight, that you have +/- 200 ft ASE.


I think it really is a "try it" thing.

Note this wording:

Operators must ensure compliant performance prior to operations in RVSM airspace outside U.S.-controlled airspace (see paragraph 4.4).

Note the distinction for outside US airspace, suggesting assured compliance is not necessarily required for operations inside US airspace on initial flight.


You can't. You can only test ASE in actual operation at the various altitudes and airspeeds in RVSM airspace. This is why RVSM compliance monitoring is difficult.

Mike C.

Well.... it’s a bit convoluted with references within that AC document. Ch 4 Intro states:

4.1 Introduction. This chapter discusses RVSM operations for operators and pilots seeking to conduct flight in RVSM airspace under the provisions in part 91 appendix G, section 9.

4.1.1 Operators and pilots seeking to operate in RVSM airspace under the provisions in part 91 appendix G, section 9 are not required to apply for authorizations. The operator or pilot needs to ensure all applicable requirements in part 91 appendix G to operate in RVSM airspace are met. The operator or pilot should:

1. Determine the aircraft is RVSM compliant (see Chapter 2);

But then if you go read Chapter 2, the beginning says this:

2.1 Introduction. This chapter provides guidance on how operators can determine if their
aircraft is compliant and eligible for operations in RVSM airspace.
2.2 Aircraft Eligibility. An aircraft is an “RVSM-Compliant Aircraft” when:
1. The aircraft design ensures the aircraft will meet RVSM performance requirements, and

2.2.1 Aircraft may be produced RVSM-compliant or brought into compliance through the application of appropriate Service Bulletins (SB), Service Letters (SL), Engineering Change Orders (ECO), or Supplemental Type Certificates (STCs). For airworthiness guidance, see Appendix A.
2.2.2 To determine eligibility for RVSM operations the limitations section of the Airplane Flight Manual (AFM) or AFM Supplement should indicate the aircraft has been determined to be capable of meeting the RVSM performance requirements of part 91 appendix G.

This all seems to imply a requirement for some kind of prior documentation that the aircraft meets RVSM design criteria through one of the various design certification methods.

Appendix A, FWIW, is also a detailed dive into some of those design criteria. It seems largely held over from the part 91 appendix G section 2 stuff, but it is kind of incorporated by reference in the AC’s Chapter 2 text above.

Clear as mud. BUT - as you have noted previously, the text in 2.1 says it is providing “guidance”, not the only mechanism. So there is still a little wiggle room for another mechanism such as a simple flight test to get the FAA generated report. But I’m still thinking I’ll let someone else try it first.

This is totally ripe for someone with a friendly FSDO to establish a program to flight test individual aircraft, sign it off on a 337 if the test works, generate the appropriate AFM supplement, and charge owners a dollar or two for it.

The whole point of section 9 is to NOT require approval to enter RVSM airspace and to change the process from one of design compliance to monitoring compliance.

Note that under the old section 2 criteria, people HAD to go fly candidate RVSM aircraft in RVSM to test them. There's NO WAY you can develop an RVSM STC WITHOUT flying the airplane in RVSM airspace. This is true even for NON GROUP airplanes, that is individual serial numbers.

So there is precedent for flying an airplane into RVSM airspace which isn't a priori approved.


Or an outfit that simply tests your airplane to section 9 criteria and signs it off as being compliant with that.

Mike C.