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Posted (edited)

I am curious about a few things, maybe someone can enlighten me :

1) the engine monitor thing in the middle (the one that looks like an equalizer display, or an audiogram, well, you now, the graphics thing), I can tell Y is the temperature, but what is X ? i.e. what temperature is this indicating ? Why six separate readings ? (okay, I must confess my laziness, I did not turn the "instrument description" option on)

As mentioned before, each cylinder has a head temperature sensor in it. Remember, this is just a mechanical object and each cylinder doesn't know the other 5 are there. Many temp analyzers will show "peak" and hold a bar at the top to aid in leaning procedures.

2) It is the first plane I fly where you can only select one tank at a time. So I am curious as to the practical reason that makes a plane manufacturer decide not to include a "both" fuel selector. Also, what is good practice with this ? Do you switch tank a) when you notice a tendency to roll, b ) when above a given difference in fuel quantity c) every so many minutes ?

General aviation aircraft rely on their fuel to be gravity fed to the fuel pumps. In a high wing aircraft, such as a Cessna, a "BOTH" selector is available because not only are both wings able to supply gravity assisted fuel to the pump, but also have a feeder tube running between both tanks to keep the pressure equal. In a low wing aircraft, because there is much LESS, and sometimes NO gravity to assist the fuel to the pump. In the event the tank runs dry, or fuel sloshes away from the pickup, the pump will more likely suck air (less resistance) from the empty tank than from the full tank. Since high-wing aircraft have the gravity assist, the pump will always have a constant pressure of fuel flowing to it.

A secondary effect, as mentioned before, was in order to isolate a tank in the case of bad fuel.

3) What about the landing light : it looks very dim, my bedside table is brighter than that. I doubt anyone can spot the plane on approach on a rainy day with this kind of light. Is that an issue with the original ACF or some setting gone wrong in plane-maker ?

Just the way it was modeled, probably

4) What max-altitude can you hope to fly at in a non-pressurized aircraft such as this one (supposing you are not equipped with any kind of oxygen supply) ? 15,000 ft (wild guess) ?

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/ba9afbf96dbc56f0852566cf006798f9!OpenDocument

14 CFR 91.211 states:

a) General. No person may operate a civil aircraft of U.S. registry--

(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;

(2) At cabin pressure altitudes above 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen during the entire flight time at those altitudes; and

(3) At cabin pressure altitudes above 15,000 feet (MSL) unless each occupant of the aircraft is provided with supplemental oxygen.

5) Below the fuel pump switch it says that take-off and landings do not require the pump on, but only if fuel pressure drops below green (and at start-up, of course). But when would that happen ? When the tank is almost depleted ? In case of carburetor icing ? If the fuel line gets clogged ? Also, where is this pressure measured exactly ?

I've lost engine-driven fuel pumps in flight. Many GA aircraft require you to put the fuel pump on (and sometimes CARB HEAT) during takeoff and landing due to the fact you're going to be in atmospheric conditions you'll most likely find Carburetor icing. Further, the extra fuel pressure, particularly in carburated aircraft will provide extra fuel to the engine in the event of an abrupt power increase (such as a go-around). The fuel pump should also be put on whenever you are switching tanks.

Hope this helps. I'm currently learning how to teach this stuff, so if you have any more questions, let me know!

Edited by flyinhawaiian
Posted

Oh boy, it is so nice to log in and find so many great answers, I am starting to love this forum.

Ok, thank you for the info on the graphical temperature monitor and the fuel tanks. I have many questions about this.

Re the landing light, it looks dim in the day, but it illuminates the runway alright at night. I will tweak it in planemaker anyway, just for the looks. The taxi light, however, is useless, it illuminates the taxiway about 50 meters ahead, so you are totally in the dark (ha ha) when turning corners. I will tilt it down, and spread out the cone, not just for looks this time.

About the altitude thing, the ceilings seem pretty low. I guess it is to minimize risks. I mean, tourists go from sea level to Bolivia every year and don't suffer hypoxia. I suppose you cannot allow a pilot to feel even light headed for a few minutes.

Okay, now onto this temperature thing. I am trying to understand the influence of engine controls on temperature. So, three controls for the engine : throttle, mixture, and rpm through the indirect effect of propeller blades pitch.

What I know so far (ok, what I think I know) is that with throttle you control the admission of fuel/air in the cylinders which will detonate and produce work and heat. Work is measured by the manifold pressure, heat by the temperature probe.

If I increase prop pitch the engine will output more work, so I suppose produce less heat.

If I have a rich mixture I increase the combustion reaction and produce more heat, until the point where oxygen becomes insufficient, choking the cylinder so engine efficiency decreases and I guess heat as well. When I lean the mixture, temperature should go down as well.

With throttle, it seems straightforward : the higher the throttle the higher the temperature. But this will affect airspeed, which probably has an influence in cooling down the cylinder head ?

Ok, now, what I would like to know is the effect of all three combined. It is probably engine specific, but surely there are some general principles worth knowing ?

Also, what is rich of peak and lean of peak ? Is rich of peak the peak in temperature for a rich mixture, i.e. the most you can ask of your engine before it chokes on unburnt fuel ?

And, how do you tune your mixture by using the temperature readings (my current strategy is to lower the mixture in cruise flight until the engine faults and then increase it a tiny bit) ?

More tricky now : lets say I am cruising at 8500ft, lean mixture, low rpms (2100 ish), 80% throttle doing 150kts IAS (that was yesterday night). Then, because of some stupid guy that put mountains between california and nevada I had to climb to 10500ft. I applied full throttle and adjusted attitude to reach Vx (yeah, those mountains suddenly popped up in the close distance, I mean, come on !). Then I saw engine temperatures rising high. Now, what should I do to try to keep the temp low and not loose speed (or worse, height) ?

Hmmm, do I talk too much ?

Thanks guys.

E.

p.s. @Steven, unfortunately, this is indoors painting, I need another excuse ;-)

Posted

Hey, hello !

I bought it today and love it ! First time I see on Carenado's product a kind of " Genuine X-Plane GA ACF ", the prop is now like every other prop in X-Plane ( they turn accordingly to the compression of the engine ) whereas on planes like 152 or Saratoga, it looked like FS engine-prop animation ( when starting and shutdown ).

About 152, the Flight Model is actually Off, I fly the real one quite often, they are quite easy to get in voluntary spins, in X-Planes, that is just impossible ..

Posted

Emalice,

Some time ago I have written a guide, which has the answers for your questions:

Part 1:

Part 2:

Short (and insufficient) answer would be: you can't isolate throttle from propeller from mixture, all of them have influence on engine's performance and happiness and must be used in conjunction. When you see a sudden increase in temperature, then something is going very wrong - usually the engine is working too hard. Applying full throttle at low rpm could earn you gliding practice ;)

James,

Have you tried X-Aviation's C152?

Posted

Emalice,

Short (and insufficient) answer would be: you can't isolate throttle from propeller from mixture, all of them have influence on engine's performance and happiness and must be used in conjunction.

Hi.

Yes, that is exactly my problem : I think I get a grasp of what individual controls do, but have no real clue as to what their combined effect will produce on the engine.

I will read your tutorials avidly and probably experiment a lot.

And yesterday's adventure did grant me some nice gliding practice ; I thought it was some overheating while climbing over those mountains, but it turned out that X-plane decided to fail my plane (to be more precise, I had the "jet-A in prop engine" failure). Now I am not sure if the consequence of the failure was an overheating which I did not address properly and led to the burn-up, or if it was directly an engine shutdown.

Unfortunately, there are not many airports in the south Rockies and my gliding practice ended the hard way.

E.

Posted

Hello Lukasc

No, I didn't tried him, just find it less beautiful.. But from What I've heard, the flight model is just .. lovely !

I should give it a try one day.

Carenado is not the king about Flight Model, they really should start to think about it, X-Plane is not FSX, a graphic showcase... If they make the X-Plane flight model reputation decrease ..

Posted

Emalice,

The temperature rise was caused by too much throttle at too low rpm, but that won't fail the engine in X-Plane as it is. Some plugin is required to do that and I don't know if Bonanza has something like that - probably not. So far only freeware An-2 and payware T-28 monitor engine stress and will fail if exceeded. Dreamfoil Bell 206 also has some failures built in (overtorque for example). Improper fuel failure was most probably caused by X-Plane itself, not related to your flight, as it will trigger random failures after certain amount of time has passed (mean time between fails option).

James,

Stock Bonanza flies similar to real plane, not bad at all, but there is a room for improvement. Mine already flies as good as it looks ;)

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