turbo-normalize

Has anyone decided, or even thought about trying to turbo-normalize? If so are there any guesses as to what sort of performance you would get out of doing it?
Sid

I'm doing a Subaru 3.3L flat 6 twin turbo. We project 190 knots TAS at 75% at 18,000 feet. Unfortunately you need O2 up here. I would not expect to see more than 175-180 knots TAS at 10-12,000 feet with a normalized 540 so it might not be worth the trouble/ weight/ complexity. If you have the IFR ticket, O2, add an intercooler and went to 18,000-25,000 feet you should see 190-205 knots TAS but remember Van's Vne is 200 knots TAS, not IAS. Watch the extra weight in the nose and better cabin heating might be required at these altitudes.

Of course you know how Van's feels about this...

rv6ejguy said:

... but remember Van's Vne is 200 knots TAS, not IAS. ...

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I know this has probably been beaten to death somewhere or another but I believe that all of the V speeds are IAS not TAS. (elsewise why mark them on the Indicator)

Van's may have a recommended TAS speed limit (I don't know this) but it shouldn't be designated as Vne because it becomes confusing.

-Mike

The Vne TAS issue is one of the main reasons why Van's is not keen on turbo versions of their aircraft. At the sub 10,000 feet altitudes most RVs fly, 200 knots IAS is within the 10% over factor tested to. At 18 or 25,000 feet, 200 knots IAS is way over 200 knots TAS. This limitation appears to be as a result of flutter concerns rather than air load concerns as on certain other aircraft. Probably best to abide by Van's recommendation of 200 knots TAS here. Not a good area to find out- oops there goes the left aileron.

As with any major deviation from the plans or factory recommendations- think all the pros and cons through carefully before proceeding. I'm not sure what cowling/ cooling mods might be required as well at altitude or in hotter climates as there is not too much RV10 flight experience to draw from yet.

"Indicated airspeed is useful in aircraft operation as in straight and level flight and at a given weight that the aircraft will always stall at the same indicated airspeed, regardless of its true airspeed. Note that a stall can occur in any indicated airspeed, because it doesn't depend on speed but on the angle of attack, so for a given angle of bank, or a pull out, either of which increase the g factor, the stall will occur at a higher indicated airspeed, but this IAS will be constant regardless of density altitude (except under icing conditions). Other important speed points such as maximum speed with flaps and maximum structural airspeed (if less than the speed of sound) are also relative to IAS and are marked on the dial card with colored lines."

"True airspeed is the speed of an aircraft relative to the airmass in which it flies, i.e. the magnitude of the vector difference of the velocity of the aircraft and the velocity of the air."

So IAS is used for V speeds not TAS.
Sid

Van's doesn't like turbos. On the other hand a IO-390 with a turbonormalizer might be a good setup for a -10 if you don't mind giving up a bit of initial climb.

Sid said:

"True airspeed is the speed of an aircraft relative to the airmass in which it flies, i.e. the magnitude of the vector difference of the velocity of the aircraft and the velocity of the air."

So IAS is used for V speeds not TAS.
Sid

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What you say is true but not the entire story. As density altitude increases, the the air density acting on the control surfaces is decreasing. This produces a reduced resistance on control movement. So, as you increase in altitude and have performance (turboed) to have true airspeeds as fast or faster than you get down low, you are getting much closer to the critical flutter speed, even though your indicated may be well down in the green arc range.

IAS does not give you a direct indication of your speed margin above flutter.

As already suggested, anyone considering Flying an RV-10 at high altitude should be sure to read the artical published in the RVator on this subject.

Scott

rvbuilder2002 said:

As already suggested, anyone considering Flying an RV-10 at high altitude should be sure to read the artical published in the RVator on this subject.

Scott

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Is this on line? I would be very interested in reading it.
Sid

Here is a article on why not to turbo. http://www.vansaircraft.com/pdf/hp_limts.pdf

Sid

I believe to some extent, Van's is overly concerned about this issue (which isn't an issue on ANY certified GA airplane, including the Cirrus and Lancair 400).

There is a certification issue with I think the Lancair 400. Richard Collins did an article on it a couple months back in Flying mag. The Vne lowers as altitude increases. First time I have ever heard of that with piston airplanes.

I read it, it WASN't VNE that was being lowered, but where the yellow arc started, otherwise known as the "Smooth air only" speed or VNO. And it had to do with Mach .4 and above at something like 268kts at altitude. Different discussion altogether.