Question MOSAIC, LSA, and your Piper

Re: Why Vs1 and not Vs0?

It's unclear to me why the FAA has chosen Vs1 (clean stall speed) over Vs0 (landing configuration stall speed). It would seem to me that Vs0 would be a more suitable measure of an aircraft's potential energy (and thus, safety risk) during the critical phases of flight where accidents are most likely to occur. I have a hard time believing that a PA-28-140 with 150 hp and weighing 2,150 pounds, is a greater safety risk than an early Cessna 182 with 230 hp and weighing 2,650 pounds.

Secondly, it's confusing. When this proposal first came out, many, myself included, assumed the 54-knot limit was Vs0, because, well, that's what we pilots use on an everyday basis when flying. I can tell you the Vs0 of most of the airplanes I fly (at least in IAS), but I don't have a clue offhand about the Vs1 for any of them as it's simply not a configuration I give much thought to. 

Using Vs1 kcas also presents some challenges for vintage aircraft which lack comprehensive documentation. Some early Pipers, for example, have documentation which lists Vs1 stall speeds in IAS, but not CAS. Other vintage aircraft flight manuals only list Vs0. Hopefully the FAA will release a list of conforming models with the final rule.

As far as where the 54-knot limit came from? My understanding is that it is drawn from the highest previously approved Vs1 exemption for an LSA. That is the explanation provided in the MOSAIC proposal. I've been trying to follow up with a couple of members of the working group, but they are somewhat tight-lipped at the moment. Perhaps I'll get clarification eventually.
 

Good question, Steve. For someone in your position, the immediate advantages are relatively minor. If your Comanche were to be included as an LSA, you'd get:

1. The ability to fly it using Sport Pilot privileges. As long as you were willing to accept the corresponding Sport Pilot limitations (one passenger, no night flight, no flight above 10,000 msl, no international flight), you would not ever need to do another FAA medical (or BasicMed exam). This is a benefit for those who have current Private or higher certificates and medical issues not severe enough to prevent them from flying, but severe enough to be a certification hassle.

2. A slight increase in resale value versus a non-LSA aircraft. Assuming that these new regulations allow more pilots to keep flying longer (in LSA-classified aircraft) and also help bring a few more new faces into aviation (who seek a Sport certificate as the default entry-level certificate), we now have a segment of buyers who are going to be looking exclusively for LSAs. 

Bigger picture, the expansion of the acceptance of consensus certification standards means that if/when you decide to sell your Comanche and buy something else, you will have the option to purchase a factory-new aircraft certificated under the expanded LSA umbrella. Some of the designs out there that meet these requirements (but not the current US LSA rules) are pretty impressive; modern, fast, safe, and affordable (relatively) airplanes. I'd imagine more will hit the tarmac in the next couple of years as MOSAIC moves forward.
 

Hey Scott,
I would love to see the Vs1 upped a few knots so my Comanche 24 (180) would fit into the category.

At least I think I would. I'm not sure of the advantages of having my airplane in the LS category would render. How would it help me? 

The LS world is not one I know much about. 

Sorry I haven't kept up with this thread--I'm sort of a one trick pony; when I'm on a topic I my focus narrows.

Thanks,
S

James,

I am going to totally make a guess here...
If you do some pretty creative stuff you can make a wing that will have a very low stall speed in the landing configuration but has a fairly high stall speed in cruise configuration. When I say this I remember the 727 with all it's fancy devices that made the wing practically dis-assemble itself on landing. At any rate, the point here is that if the wing is "clean" it will be much higher performance but not as safe for engine out landings or unintentional stall-spin. So my guess is they want to ensure the plane stays in a certain performance range that is considered safe whether the wing is configured for landing or for cruise.

I wonder why they don’t define this off of full flap configuration?