Carenado 206 descent/landing

[Guest RiddlePilot]

>Hi Guys, very nice to have a couple of real 206 pilots here! >This is my favorite GA aircraft. There is only one thing I>have a question about, the ammeter. Can one of you guys>confirm it works correctly in Carenado's version? It doesn't>seem quite right. Here's what I see:>>Start cold and dark. >>battery on: ammeter shows large dischage -ok>turn on avionics switch: ammeter shows charge. Is this>correct? How can it show charge before the engine/alternator>are brought online? (I know that the avionics switch should>not be turned on until after engine start, but still...)>>turn off avionics switch, turn on pitot heat, nav lights,>beacon: once beacon is on ammeter goes from discharge to>charge. Is this right (same as above)?>>It's really the only niggle I have with the package. >I know a bit about gauge programming and it seems this would>be an easy fix, but unfortunately the gauge is in C so I>cannot edit it. I've emailed Carenado and they initially said>they would look into it, but have not responded to follow-up>emails.>>Oh, sorry, one other thing. In Carenado's checklists they say,>under takeoff, "MIXTURE -lean for field elevation per fuel>flow placard". Unfortunately I cannot find the fuel flow>placard published in any of the documentation or on the>aircraft itself. Would one of you be so kind as to post a pic>of the real placard? It would be very helpful as I usually>fly out of high elevations in the Rockies.>>thanks in advance!>>RyanWithout looking at the gauge in the Carenado bird, are you sure its not a voltmeter? That would indicate a "charge" as you say, but really its showing a "load".

[Guest RiddlePilot]

>Could someone explain thermal shock to me please, I've heard>of it, but don't know anything about it other than it's not>good. Why does it happen in say a plane and not a car? Surely>if the engines banging away in there then it's still pretty>darned hot?You make a comparison to a car. Remember, a car is a liquid cooled engine, as opposed to the airplane which relies on air flowing through the cowling to provide the cooling. It is much harder to regulate the temperature of the engine if it is air cooled.To explain shock cooling, you must understand the above. During cruise, and engine is typically running between 2200 and 2700 RPM. This is near the maximum power setting allowed for the engine. We know that more power equals more heat. The concentration of the heat that we are concerned with when dealing with shock cooling is the Cylinder Head Temperature, or CHT. The cylinder head is where the spark plugs are located, and thus where the combustion takes place. At the cruise power settings mentioned above, the CHT temperatures are up around the 200-400 degree celcius mark, which is pretty darn hot. As we know, metal, especially steel (which cylinders are typicically made of), expands and contracts with changes in temperature. If the changes are too rapid, it will cause an expansion or contraction that is greater than what the material is designed to tolerate and will cause a crack in the metal. This is when we blow cylinders off the side of the engine.From a practical standpoint, what happens is that we've established a specific CHT during cruise. We then realize that we're too high and too close to our destination, so we pull the power back to idle and point the nose down. Now we're in a cooling situation by pulling the power alone. Factor in the increased airflow through the cowling, and being up at four or five thousand feet where the air is cold, and the cooling effect is exaggurated greatly. Soon you will see the CHTs drop to the bottom of the gauge much more quickly than you'd like, and you realize you just shock cooled the engine.

[ztimbre 0]

Hi Travis, thanks for the reply. Without seeing the code I can't be certain if they programmed it as a voltmeter or as a ammeter. However, all the documentation refers to it as an ammeter, also it is marked DIS/0/CHG. The more electrical items I turn on the more discharge it shows, until it passes the lower 'end' of the scale, then it swings up to 'charge'. I think they just programmed the 'scale' of the needle wrong. Also, when the alternator is brought online, it seems to behave correctly and shows a small charge or small discharge depending on how many electrical items I have turned on.Does that clarify things at all? :)regards,Ryan

[lcseale53 0]

Ryan,The placard is located on the instrument panel typically near the fuel flow indicator. I cannot recall the numbers as I rarely focus on the thing (doing most of my flying from near sea level). But if you are operating out of fairly high airports, arbitrarily five thousand feet or better, use a common technique that will maximize your power. With the mixture full rich, prop full forward, apply full throttle - then - begin leaning until you see a slight drop in RPM. At that point ease the mixture back in to regain the lost RPM (and maybe another turn on the vernier for insurance). At that point you will be at your maximum power setting for the altitude. Release brakes and go.After take-off refer to the chart included in the POH for altitude/manifold pressure/mixture settings.Regards,Leon

[lcseale53 0]

Kind of depends on the mission. Keep the CHT in the green and you will be fine. Gradual descents are preferred, but power-on spirals work if you need to accelerate your descent. The 206 is a pretty draggy airplane so you can also ease the nose over somewhat and maintain a pretty good rate of descent without overspeeding the airplane. You can also slow the plane down, reduce power, and set up a pretty good rate of descent using pitch (up), or flaps (get the nose down though).A technique a friend of mine with a Glasair uses (well...used until the FAA set up a field office) was to ask ATC for the option (to land or not) and set up a cruise-power descent to the approach end of the runway. Indicating near 200 knots he would level at about 20' above the deck and at mid-field pull to the vertical and roll onto the downwind leg. At that point the airspeed was in check and he would pull the power to fly the approach to a landing. No shock cooling because the airflow was greatly reduced at pattern speed. But what a rush!Regards,Leon

[ztimbre 0]

Hey thanks Leon, that's very helpful! I had been doing something similar with the EGT, leaning until rpms drop but EGT continues to rise, then going back rich until the EGT just begins to drop and I am on the rich side of peak. BUT, I had not been doing it at full power. I seem to remember this method from what my grandfather taught me way back when, but sadly I have not flown since then, so maybe I got it wrong. In any case, I will use your method from now on. Thanks again!Ryan

[Guest cleetus vandamm]

Thanks much.