Sport Pilot Talk

You'll never actually be able to test Vh under defined conditions, because even if you are at 15 C and 29.92, at sea level you'll be on the water, thus the humidity will not be zero!

Just because I feel like being pedantic , at Furnace Creek in Death Valley (L06), flying at 210 ft AGL you're at sea level. I'm pretty sure 0% humidity is very common. Not too sure how easy it is to get 29.92 and 15 C, but I gotta believe it's possible.

Actually, I thought about Death Valley. But even better is Bar Yehuda Airfield, LLMZ, between Masada and the Dead Sea (I was there a dozen years ago). At traffic pattern altitude, you're still 240 feet below sea level! It's only a 3700 foot runway, but the air is so dense that Beech Barons jump into the air. I would suggest that it's the perfect place for Vh testing - a standard atmosphere is actually possible there in early morning.

Masada is a bucket list if you haven't done it. The Masada mini-series from 1981 is worth viewing. I need to fly the Sling 2 over Masada...I'll work on that. I think a beefed-up 912ULS would make it a better experience! Here is a pic I took in 2017(which does not do justice to what you see when you are there)

drseti wrote:

MrMorden wrote:
There is no requirement for the pilot to maintain 120kt or less.

True, but...

That is a requirement for manufacturers to get their airplanes certificated as SLSA or ELSA, or for legacy airplanes to be considered "light sport aircraft".

Partially true. 120 knots is the Vh limit. The definition of Vh (max horizontal speed) is very narrowly defined as:

Max continuous power (in this case, 5500 RPM)
Flight at sea level
Standard atmosphere (15 C, 29.92 in Hg, zero relative humidity)

You cannot, however, make an alteration that takes the airplane out of LSA performance parameters. But unless you did calibrated sea level flight testing, how would you know?

You'll never actually be able to test Vh under defined conditions, because even if you are at 15 C and 29.92, at sea level you'll be on the water, thus the humidity will not be zero!

I’m aware of those requirements, but they’re not germane to my point that the 120kt limit is a manufacturer limitation and not an operational one.

Isn’t it the case that if you are ELSA , then you are the manufacturer and any modifications like for instance a 150 hp big bore , are then on you ?

Warmi wrote:Isn’t it the case that if you are ELSA , then you are the manufacturer and any modifications like for instance a 150 hp big bore , are then on you ?

It’s not like E-AB, the manufacturer is still the company that built the airplane (or kit), since even a kit built ELSA must be built exactly as the kit manufacturer specifies.

Once built or converted, the owner does have some leeway on making major modifications like props and engines. But the FSDO has to be notified of the change, and you cannot make any change that takes the airplane out of LSA performance limitations.

You might be able to use a 150hp bigbore kit, but depending on the aircraft type you might have to amend the operating limitations to specify a very flat prop pitch to make sure that you don’t exceed the LSA Vh limit.

MrMorden wrote: I’m aware of those requirements,

I rather figured you were, Andy. My comments were for the benefit of those here who may not be.

drseti wrote:

MrMorden wrote: I’m aware of those requirements,

I rather figured you were, Andy. My comments were for the benefit of those here who may not be.

When you say “partially true” in response it sure sounds like you are correcting me. My statement was completely factual. Adding a bunch of technical info about what is meant by the 120kt limit adds confusion to, rather than clarifies, the point of who has to abide by it.

IMO of course.

Well, Andy, no correction was intended - what you said was entirely factual. What I did was expand upon your statement (for the benefit of those students who wanted extra credit - old schoolteacher habits die hard)