Carbureted O-320 and CS-VLA compliance

[Camillo]

Hi.

I'm trying to obtain an IFR VMC permit to fly for my RV9A.

Italian amateur build regulation states that the builder has to comply to CS-VLA rules (subparts E and F).

§CS-VLA 1093 states as follows (from subpart E):

CS-VLA 1093 Induction system icing
protection
(a) The reciprocating engine air induction
system must have means to prevent and
eliminate icing. Unless this is done by other
means, it must be shown that, in air free of
visible moisture at a temperature of -1°C –
(1) Each aeroplane with a sea-level
engine using a conventional venturi carburetorhas a preheater that can provide a heat rise of
50°C with the engine at 75% of maximum
continuous power;
(2) Each aeroplane with an altitude
engine using a conventional venturi
carburettor has a preheater that can provide a
heat rise of 67°C with the engine at 75% of
maximum continuous power;
(3) Each aeroplane with an altitude
engine using a carburettor tending to prevent
icing has a preheater that, with the engine at
60% of maximum continuous power, can
provide a heat rise of 56°C;
(4) Each aeroplane with a sea-level
engine using a carburettor tending to prevent
icing has a sheltered alternate source of air
with a preheat of not less than that provided
by the engine cooling air downstream of the
cylinders.

Now, I installed a muffler - bought on Wicks aircraft (EC100-020) - much bigger than that which Van's catalog supplies, but I seriously doubt that it can rise temperature of 50°C (see point #1 above).

The engineer says that I will have to give evidence of that temperature rise OR give evidence that our carburetor falls in the #4 point (carburetor tending to prevent icing).

Does someone know if the Precision carburetor which comes with the stock Lycoming O-320 D1A is "a conventional venturi carburetor" (point #1) or a "carburetor tending to prevent icing" (point #2)? I may answer yes to #1, but maybe its particular displacement (attached to the wet sump) makes possible to answer yes also to #2.

Second question. If the answer to the first question is only 1, is the particular position of the carburetor in the O-320 (attached to the wet sump) and the narrow gap with the cowl enough to state that: "(a) The reciprocating engine air induction system has means to prevent and eliminate icing"?

Thanks a lot.
Camillo

Edit: sorry for the angry smile. It came out for mistake

[L.Adamson]

All I can say............is that the fact, the the Lycoming carbs are attached directly to the oil sump, does have an effect on pre-heating the carb. This is why older Cessna's with Continentals always used carb heat for landing, while Pipers with Lycomings..........specified using carb heat only when required. There is also reference to this in Lycoming manuals.

L.Adamson --- RV6A

edit: A bit of additional info...

http://www.sacskyranch.com/crbice.htm

[Camillo]

Thank-you.

I searched on the web but found nothing more.
On Saturday I will look at my engine manual.

Ciao.
Camillo

[Mel]

Originally Posted by Camillo

Thank-you.
I searched on the web but found nothing more.
On Saturday I will look at my engine manual.
Ciao.
Camillo

Section 3-8 covers use of carburetor heat.

[Camillo]

Yesterday I got up to FL90 (OAT 2? Celtius) and applied carburetor heat while @ 20 MAP. Rise in temperature was only 10? Celtius (instead of 50? required from CS-VLA).

I am thinking of removing the Wicks muffler I installed
http://www.wicksaircraft.com/catalog...813/index.html
and buying this one
http://www.aircraftspruce.com/catalo...sheatmuffs.php

[Alan Carroll]

What is the absolute carburetor temperature you are measuring? Some probes installed in the location provided in the Marvel/Precision carb read higher than the ambient air, due to the heating of the carb throat by contact with the oil sump. If this is the case then maybe you could use this information as evidence that your carb "tends to prevent icing"?

[Finley Atherton]

Camillo,

I also have the Wicks SS heat muff and I think with some minor modification it could produce much more heat. I have thought about fabricating a baffle blocking off a large part of the gap so that air would be drawn in from smaller gaps at each end. This means that incoming air would be forced to travel around a greater length of exhaust pipe. The baffle could be a piece of sheet SS or aluminum that attaches to the outside of the heat muff with screws/nutplates.

Another thing you could do is to increase the surface area that heats the air by wrapping a stretched spring all around the exhaust pipe in the whole area covered by the heat muff. You can make your own long "spring" by coiling 0.041" SS safety wire (lockwire) around some rod or dowel. Obviously the spring must be secured at each end to keep it firmly wrapped around the exhaust pipe.

Finally, for the purposes of measuring the temp rise with carb heat, I suggest you temporally install the temperature probe so it is measuring the temperature of the air before it enters the carb. I suggest securing the entire probe in the carb air filter box just in front of the air filter (on the outside of the filter so it can't get sucked into the carb). Don't forget to block off the hole for the carb temp probe in the carb body.

Fin 9A

[Finley Atherton]

Camillo,

Have a look at what Vern Little did to seal his carb heat valve to stop cold air being mixed with the hot air. See the last 3 photos at the bottom of the page HERE

Fin
9A

[L.Adamson]

Have a look at what Vern Little did to seal his carb heat valve to stop cold air being mixed with the hot air. See the last 3 photos at the bottom of the page HERE

\

I do believe that the flange for additional air from the sides, was added after this accident. I'd leave as is...


"According to the Van's Aircraft construction and operating manual, one method of building the
internal carburetor heat system is to "run a 2-inch air hose from a heat muff and position it to
feed into the alternative air inlet of the carb[uretor] air box without being attached and closed."
According to the FAA inspector who examined the aircraft following the accident, this is the
method by which the pilot constructed the airplane. According to the inspector, the 2-inch hose is
not large enough to adequately supply enough heat to the carburetor to sufficiently melt the ice."

L.Adamson --- RV6A

[E. D. Eliot]

Check with others there and see what they did in order to certify their aircraft. Check the experimental and the certified aircraft in your area.

I suggest that you make friends with a certified aircraft mechanic - maybe they can help you. Please let us know what you find out.