Engine Management Techniques

[VulcanB2 5]

Hi,

I have a few queries regarding management of the engines.

1) The manual (and checklist, 40s version) states climb at 2300 RPM and 35" MP. I've however read in the forum that climb is conducted at 2700 RPM and 42" MP.

The latter would make more sense with the floats extended as she seems to lack performance with anything less?

2) The manual also states that at 50 ft, setting the props to full results in the RPM staying at 1800 RPM. This suggests a lower power setting than I'm using currently. I think I see 2050 RPM as I aim to be at idle power as the mains touch down, starting to retard the throttles at ~30 ft with a slight flare. Is this correct technique?

3) When doing closed circuits, is it permissible to keep the props at 2700 RPM or could damage result?

4) Not strictly engine-related, but when doing circuits on water, are the floats left extended, or are they needed to be retracted to reduce drag and improve performance? The sim feels to have a bit too much drag with them extended and the cowl flaps fully open, and climb rate is severely degraded.

Best regards,

Robin.

[fliger747 0]

This is a well done aircraft, so the developers might comment authoratatively on how it is set up in the sim. I will comment only on general aircraft good operating technique, which I think the Cat will respect. I would pull the prop RPM's back for the bumps and circuits. Remember always to reduce MP, then RPM, conversely, up with the RPM and then increase the MP.

For seaplanes, training if sufficent water space is available, often will do several takeoffs and landings in a row, in a straight line, only climbing to several hundred feet. For such a situation I would leave the floats extended. For a complete liesuerly pattern, they were probably exercised to make sure a complete normal flow of events was completed, itself a good training habit.

For your sim training, getting into the habits of normal complete sequence will make flying the airplane both a pleasure and more natural.

Cheers: Tom

[Finn 873]

All the recommended engine settings are recomendations only - just arough estimate of what should work.

The most important thing is not to exceed engine temperature. As long as Oil temp and CHT is within limits, Your engine settings are fine.

On the DC-3 (and other aircrfat) there was a rule not to set manifold pressure below square. This means that if Your RPM is 2050, never let MAP go below 20,5 Inhg.

Cowlflaps are not necessary needed to be opened fully before the final apparoach phase. This is done to prepare for a go-around.

The drag of the floats might be a bit excessive, but it was added, cause during beta testing we found it too hard to slow down the Cat for landing.

The exact amount of drag is not known, but lowering the floats will reduce lift a bit, requiring a small amaount of backpressure on the Yoke, wich will increase drag - probably more than the drag of the floats themself. The floats in down position will also cause a pitch down moment - again requireng a bit of ack pressure / trimming.

Just to re-state - The numbers on the power table is not written in stone, but just a guideline. What works for You is the right thing to do

Finn

[Jigsaw 20]

I also have a question regarding engine management: I did some flights recently in ground temperatures around 8° Celsisus and rainy conditions (high humidity). In these conditions I wasn't able to follow the manual instructions to switch off Carb Heat before take off, because when I did that the engines died on me before I could start the take off roll. I wasn't even able to start the engines properly without maxing out Carb Heat on the ramp (primer was on). Am I doing something wrong is that something that pilots may have to do with the real Catalina as well?

[VulcanB2 5]

Hi,

I've noticed that carb heat is too effective, too soon. Given that it requires heat from the exhausts, just after start they will still be cold even though the actual exhaust gases themselves will be hot (unless I miss understood something?).

To be able to switch them off for takeoff, apply the brakes, open the throttles to approx. 30" then close the carb heat. Carb icing readily occurs at lower powers, but at high powers the water vapor doesn't have time to "stick" to the carb and accumulate (although that is not to say you couldn't get carb icing still - you're stuffed if that's the case).

Best regards,

Robin.

[Finn 873]

The exhaustpipes arer only made of thin metal, so right after startup they will become very hot quickly.

With relative low RPM's present right after startup, there will also be a relative low rate of airflow through the inlet duct of the heat exchanger, so the air will become hot fast.

For calculating the heat effect for the carbheat, we use a function of OAT and CHT, so the heat buildup should really not be too fast.

Consider that at low RPM's a lower massflow of air has to be heated, though with colder exhaustpipes.

When increasing RPM, the amount of air flowing drawn through the engine is much higher. This increase in flow requires more heat, but at higher RPM's the exhaustpipes also get's hotter.

Finn