C414 Power Reduction Technique

[noslonlo]

The airplane is a Cessna 414A with Ram 4 conversion. I was taught to reduce the manifold pressure 2" every 2 minutes. Another guy recently told me 1" per minute would be better. Any thoughts?

 

[banned username 2]

The airplane is a Cessna 414A with Ram 4 conversion. I was taught to reduce the manifold pressure 2" every 2 minutes. Another guy recently told me 1" per minute would be better. Any thoughts?

I was once flying a C-414 with one of our pilots who used to fly mainly King Air's... It was the coldest night of the year (around -12°F on the ground) and we were screaming towards the airport for a visual, he then realizes he is much closer than he thought and pulled the power from about 33" to basically idle... I was like "Oh sh!t!"... Nothing happened to the engines, they were fine...

Now I certainly wouldn't recommend this guy's "technique" by a long stretch... But on the other hand, I think 1" per minute may be a little on the exaggerated side (in the other direction)... Nice smooth power changes, and allow for some cooling and you'll be fine... a few inches a minute should be perfectly safe...

Just my $0.02...

 

[flydaddy0499]

I have about 1000 hours in 400-series Cessna and about 400 in C-414's. I have always used the 2 for 2 method. If memory serves correctly, 300 degrees on the CHT is your target. Anything less than that and I was told that shock-cooling was not an issue. Also, keep in mind that the greatest temperature shock to the system is usually on take-off. Either way, if you baby your motors and maybe cruise an inch or two under the book, the motors should take you to TBO every time. Of course, I think that RAM builds the cheapest POS motors around. Everyone will have their opinions but I believe everyone will agree that extra care will keep the boss happy come maintenance time.

 

[MauleSkinner]

The airplane is a Cessna 414A with Ram 4 conversion. I was taught to reduce the manifold pressure 2" every 2 minutes. Another guy recently told me 1" per minute would be better. Any thoughts?

I used to use a 2-3" initial reduction, with an inch a minute after that...I don't know what the guys before me were doing, but when I started flying the airplanes, they quit having to replace cylinders and cases.

One thing about the 414...gear and full flaps down a 3-degree glidepath requires about 29-30" MP...One of the pilots I replaced in the airplane went from there to idle on every landing. Again, maintenance reduced when that pilot quit flying it.

Fly safe!

David

 

[JimG]

I've got a 340, with brand new RamVI's.

I was told by mechanics, seasoned twin Cessna drivers, and even FlightSafety the 1"/1min rule.

I set the Garmin 430 for an 800/min rate of decent approach, and when I reach that distance, start down at that rate, but I use a clock to figure the altitude/manifold pressure settings to give me that 1/1 all the way down.

Sometimes Center doesn't want/can't give me that rate/distance, so if I can't go lower....I go slower. If they don't like it....I tell them my situation with new engines and have always received cooperation.

 

[DGdaPilot]

I always did 1 to 2" every 2 miles. I guess that probably works out to what everyone has said above.

 

[USMCmech]

If the CHT is bellow 300 there is nothing to worry about, the engine is already "cooled". Yank it back to idle if you wish.

Above that 2" every 2 mins is a good rule of thumb. Also, have amechaninc find out why your engine is running so hot. There isn't any reason to regualary run over 350 CHT

Even the 2/2 rule is almost certianly overkill, if you are performing a normal constant airspeed descent at 500-800 FPM.

Better yet buy a engine monitor and watch the CHTs. If they don't show a nice gradual cooldown, then reduce your airspeed a little.


"shock cooling" has gone from a freak occurance usually brought on by gross abuse of the engine, to a boogy man waiting to devour engines if the pilot makes one wrong move. In fact plenty of scientific evidence points to there being no such thing.

Consider the abuse that many engines go through, yet have long lives, most making TBO.

Skydiver ops: climb at Vy and max power for 20 minutes (HOT!!!!), followed by a mere 2 minutes of cool down then a Vne descent at nearly idle. Repeat up to 12 times per day.

Areobatic airplanes: full power with very LOW airspeed, followed imeaditely by idle and high airspeed, over and over and over again.

If shock cooling was that much of a problem these planes would constantly be falling out of the sky. CHTs simply don't move that rapidly in real life. The cylinder head of your engine in not like that glas plate you took out of the oven and put under the sink (my mom was pissed when I did that). Aluminum is not nearly that brittle.

Also about 50% of the total cooling comes from the engine oil. Since most planes have dry sump oil systems, airspeed and power changes have little imeadiate effect on oil tmeps. So in effect, the engine is partialy liquid cooled. The oil alone will useually keep things warm no matter what you do with power or airspeed. Some old big radials had "oil cooler doors" to regulate the oil tmeps.


Takeoff and climb is FAR more stressfull that descent ever will be.

Either way, if you baby your motors and maybe cruise an inch or two under the book, the motors should take you to TBO every time.

Good rule for cruise, but DO NOT take off at anyting other than full throttle (or max power setting on turbocharged engines). At full throttle, the "power enrichment valve" opens up and enrichens the mixture to aid in cooling durring the critical moments of takeoff and climb. "Babying" your engines durring take off is actually destroying them. I recomend climbing at full throttle all the way to your cruise altitude, and doing so at a "cruise climb" airspeed once you get a little altitude.

 

[Lead Sled]

Good post USMCmech. If you guys do a search on Avweb you'll find some articles on engine operation by John Deakin. It's good stuff and ought to be required reading.

'Sled

 

[dhc8fo]

I use the initial 2" reduction, then 1" per minute at 10 minutes out. Works great for the 340 I have now and the 421 I used to fly made it TBO each time (has over 10K hours on it!).