Things to just replace in a Commander 900

[igm05270]

Thank you all for being so kind while letting me know that a pressurized piston is just a poor decision for what I am trying to accomplish.If any of you have had any experience with Pam Brown from Twin Commander LLC Technical Support and Jim Worrell. In doing so I am entering the unknown realm ( at least to me ) of turbine aircraft. With this being the case I am trying to be cautious. With my experience with piston powered aircraft, if you want good reliability, the first thing you replace is vacuum pump, overhaul or replace the magnetos, the battery, tires/brakes, if any of these items are beyond 40% of their useful life. Is there items, engine or airframe specific, that even though they may be functioning, that should be overhauled or replaced to ensure (as much as you can) reliability?

[donv]

First of all, congratulations! A 900 is a great airplane.

I think you raise a good question, and in return I would ask if the airplane has been flying regularly or has been sitting. On an airplane which has been flying regularly and has good records, I would just keep going and see what happens.

My 980, when I got it, had only flown about 10 hours the previous year, even though it was very well maintained and always in annual. As a result, the sort of issues I had related to valves sticking and that sort of thing. So exercise all of the valves-- fuel shutoff, fuel interconnect, those are the main ones. Avionics can be an issue, but that really depends on what it has in it. If it's been upgraded and has reasonably new Garmin stuff, then it's probably fine. If it's the old original radios, then audio panels can be troublesome.

Also, if it has a Sundstrand, I can't emphasize enough the importance of keeping the oil level up by topping it every 25 hours, and if you don't have good records, I would change the filters. They are ridiculously expensive, so if you have good records and they don't need to be changed then don't, but if you have any doubt, then change them.

Other than that, 900s tend to be solid, reliable airplanes.

[igm05270]

I am in the process of looking into finding a 900 but haven't made the final jump yet but am hoping to make it soon. I realized I should have proofread my last post. Both Pam and Jim have been a wealth of knowledge and I hope to find a 900 that has been flying regularly but also understand that with the market being so hot I may be stuck with what is out there, but I am willing to hold off and fish around for a while but the 900 fits the bill of what I am trying to accomplish. I plan on having a Garmin setup installed for the longevity and weight reduction but other than that am looking to mostly do cosmetic upgrades and spend money upfront for at a minimum a feeling or reliability. With that being said, do you guys feel that there are any STC's that are worth every penny and/or ones that are not worth it?

[donv]

I assume you want one with -10 engines, although depending on what you want to do with it and the price, maybe -5s would work.

There will be a big debate about whether you want the Enviro environmental system or want the Sundstrand... and you may not have a choice. Personally, I really like the Sundstrand, but I am in the minority. If you are operating in hot and humid places like Florida or the Bahamas a lot, then Enviro might be a better choice.

In either case, I would want to have freon air conditioning (it comes as part of the Enviro system). Even in my relatively temperate Pacific Northwest climate, the freon air is really nice to have in the summer.

Other than that, the usual updates that Twin Commander has come up with are generally good things. I really like my S-Tec 3100 autopilot, although a 900 might have the Collins APS-80 (I think?) which was a pretty darn good autopilot as well.

[igm05270]

Yeah I think that the Enviro system may be a good choice as I believe there will be people that are looking to fly down to the Florida, Louisiana, Tennessee area where that will probably be needed. As for the engines, to begin with, I am probably going to just operate what come on the aircraft until TBO then consider an upgrade  to possibly the -10s. Like I said, I am new to turbines and understand it is going to be a steep learning curve. I have a mechanic that will be going on this adventure with me and is planning on going to the initial 5 day maintenance course that Twin Commander offers to make sure that I have some who knows what they are doing. As for the engines, I know that Pistons, if treated right, can go to and beyond TBO. Are -5's and -10's the same way or do they tend to peter out before TBO?

[donv]

The -10s are happy going to TBO and beyond (if you are part 91). There are some STCs which can get you to a 7000 hour TBO for the -10 (but with some calendar limitations which make it impractical for a normal corporate user), so 5000 (or 5400) is no big deal. I keep hoping that the 7000 hour TBO will become a reality for us, but I really don't know if that will happen. -10s have a lot of margin, and are much more robust.

The -5s can run into issues at hot section, depending on how they are operated. Often they will start making less power before the hot section interval, requiring an early hot section. This is usually a problem if you are running them hard or going into hot and high airports frequently. On a 900, you would be running the -5s pretty hard, so I would say they probably will make it, but I have less confidence than I do with the -10. We had fairly regular issues with the -5s on the air ambulance operation I flew for, but we did a lot of hot/high operations, and had a lot of different pilots cycling in and out of our fleet.

[donv]

A couple of other thoughts: First, you are unlikely to find a -5 900 anyway, at this point. I know I haven't heard of one in years. The -10T conversion just makes too much sense for the 900.

Second, I believe the 900 needs some sort of STC or custom kit to raise the max altitude to FL350... I would probably do this.

Third, if you get a 900 with -10s, I think it really makes sense to get one with RVSM, or add that. The airplane really does perform well at FL290 and above.

[JimC]

If you're part 91 and not flying RVSM internationally, it makes sense to use Section 9.

https://www.law.cornell.edu/cfr/text/14/appendix-G_to_part_91

[donv]

Section 9 allows you to do is to skip the height monitoring requirement-- where you have to fly over an approved height monitoring facility, and also, I believe, eliminates the requirement for an LOA or Ops Specs, which is a big pain.

See the FAA's FAQ on this topic:

https://www.faa.gov/air_traffic/separation_standards/rvsm/documents/FAQs_RVSM_ADSB_v5_09162019.pdf

The aircraft still has to be properly equipped and certified for RVSM operation, though. See this from Duncan Aviation:

https://www.duncanaviation.aero/intelligence/2019/December/clarifying-the-relationship-between-ads-b-and-rvsm

If you're part 91 and not flying RVSM internationally, it makes sense to use Section 9.

https://www.law.cornell.edu/cfr/text/14/appendix-G_to_part_91

[igm05270]

The business model that is trying to be attempted is fractional ownership using a commander 900. It will be operated under part 91, which will help avoid some expensive regs but I want the airframe to be well maintained. I will look into the RVSM requirements. Is there anything else that should be looked into to do a venture like this that is aircraft specific?

[JimC]

https://www.duncanaviation.aero/intelligence/2019/December/clarifying-the-relationship-between-ads-b-and-rvsm

I'm going out on a limb, but I think Duncan has the order wrong. I went through a series of RVSM monitoring flights doing this, and had direct communication with both the FSDO and NAARMO when I did section 9.

You do not have to tell NAARMO anything before your RVSM test flight. You do have to advise ATC that you are negative RVSM. I had one controller tell me that I couldn't enter RVSM airspace if I wasn't RVSM. This isn't true - the controllers can deny your request if they're saturated, but you are allowed in with ATC approval. ATC will need to provide extra separation for you since you're not RVSM. FL290 is fine - you don't have to go any higher for your monitoring flight. You must fly 15 minutes level at FL290 (or FL300) without changing altitudes. I just said "NXXXX requests FL290 for 15 minutes, RVSM test flight, negative RVSM."

Ask NAARMO to evaluate your flight *after* it's over. In late 2020, they were about 60 days behind on producing these reports. It looks like they're farther behind now.

If you pass, you'll show up on the approved Part 91 aircraft list. It's here:
https://www.faa.gov/air_traffic/separation_standards/rvsm/documents/US_MASPS/US_ADSB_SEC9_A.pdf
"All Aircraft present in this segment of the database have obtained RVSM Airworthiness approval."

At that point, you're done. You will continue to be automatically monitored on future RVSM flights, and if you don't meet standards they will let you know quickly. You must continue to fly RVSM once every 24 months to stay on the list of approved aircraft.

If you fail, take the report to your avionics tech.

The ADS-B performance report will NOT tell you if your plane is RVSM-qualified. You should pull it BEFORE your RVSM flight, not after. If there are any problems on this report you have no chance of passing the RVSM monitoring flight and you're just wasting time.