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xender

How long should the engines last?

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Hi guys!

Im wondering, how long should the engines last in green before going yellow? I can manage to get like 10 hours or so (not in continuous operation but in multiple flights) and after that they start to get yellow.

Is that ok or im mismanaging them? (This is all manual, without AFE).

Also, lets say im climbing to FL200. At what point should i switch to auto lean mixture? Right now i leave the mixture at auto rich until i real cruise altitude and then switch to auto lean. Is that how it should be done?

Thanks!

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3 hours ago, xender said:

Hi guys!

Im wondering, how long should the engines last in green before going yellow? I can manage to get like 10 hours or so (not in continuous operation but in multiple flights) and after that they start to get yellow.

Is that ok or im mismanaging them? (This is all manual, without AFE).

Also, lets say im climbing to FL200. At what point should i switch to auto lean mixture? Right now i leave the mixture at auto rich until i real cruise altitude and then switch to auto lean. Is that how it should be done?

Thanks!

Hi Juan:  The engines should give you hundreds of hours.  I'm not sure if they stay green for a typical TBO but it will be much greater than 10 hrs.  FL200 is an unusually high cruise altitude, why so high?  This isn't a jet that gets better performance and economy at altitude. I fly around 8000 or higher as required for terrain.  Make sure you power back from takeoff to METO after takeoff and power back to climb once at climb speed of 160-170 KIAS.  Keep it auto rich and in climb speed after you level off at cruise and let the excess power accelerate you to the book cruise value. Then set a power according to book and then auto lean and cowls 0.

Always stick to book values for power settings.  You have a choice of the original Douglas charts that use BMEP or you can use the additional charts PMDG added from operators flying her today that use MP.  Either one, but stick to the numbers.

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Thanks Dan.

I usually fly at FL200 because that's what pfpx tells me to do when i do my flight plans. Maybe that's killing them prematurely 

 

Thanks

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It is not unknown for a Pratt & Whitney R-2800 Double Wasp to go 1,400 hours before it needed a major overhaul, but certainly it should last a 1,000 hours before needing anything really major doing to it if operated properly, but, if it has been mismanaged and damaged, then subsequently operating it properly will not mean it will then last for that length of time because the damage has probably already been done. Note that this is not true of all P&W Double Wasps, as there are very many different models of it and some are more resilient than others, but as a general guide, if you are getting problems after ten hours of operation, then that is indicative of it not being operated properly, actually at about ten hours the real thing probably won't even have been run in properly.

Like most air cooled engines, if it appears to be using a lot of oil, that's usually an indication that it has been operated incorrectly, so that's a good guide. It isn't just the settings you put it on for flight either which you have to watch, it's how you manage cooling it for a descent too, and since you've been taking it up to 20,000 feet, that means an air cooled radial like the R-2800 would be particularly at risk of shock cooling on the descent, this is where the engine gets throttle back and also goes down into thicker air, meaning more airflow goes over it and in combination with it being throttled back, it cools down too quickly, this leads to damage such as cooling fins cracking and cylinder heads warping, which then blows the cylinder head gasket, which reduces compression meaning it will develop less power and run unbalanced and it makes the oil leak too. To avoid shock cooling with radial air cooled engines, in addition to using the cooling gills, you may need to occasionally put the revs up even on the descent so it doesn't cool down too quickly. To be honest you should do that anyway occasionally as it helps to prevent the plugs fouling from oil build up on them when throttled back for extended periods.

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2 hours ago, xender said:

Thanks Dan.

I usually fly at FL200 because that's what pfpx tells me to do when i do my flight plans. Maybe that's killing them prematurely 

 

Thanks

Don't let PFPX select your cruise altitude. That alone will not injure the engines but never go that high unless there is a really good reason.  This isn't a jet.

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20 hours ago, Chock said:

...that means an air cooled radial like the R-2800 would be particularly at risk of shock cooling on the descent...

If shock cooling is a risk then are those effects also seen in cold climates sub zero temperatures on shutdown? It appears that would be the greatest shock cooling area because of no heat production. And with a massive fleet of piston powered airlines we have yet to see any evidence which is statistically relevant to support shock cooling. Yes damage can happen if there are flaws in the metallurgy but that is the root cause not the high cooling rate theory.

I highly suggest reading Pelican's Perch by Jonn Deakin https://www.avweb.com/news/pelican/182102-1.html

He has a wealth of information and we used it at our flight school as a foundation to engine management, especially for those looking to get into the big bore high performance engines.

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2 hours ago, CrashTronic said:

If shock cooling is a risk then are those effects also seen in cold climates sub zero temperatures on shutdown? It appears that would be the greatest shock cooling area because of no heat production. And with a massive fleet of piston powered airlines we have yet to see any evidence which is statistically relevant to support shock cooling. Yes damage can happen if there are flaws in the metallurgy but that is the root cause not the high cooling rate theory.

Agree, while shock cooling is a concern in our TSIO-520s on the Chancellor, there is little concern for that in the big round ones. Primary emphasis is on keeping a positive BMEP indication which means the props are not turning the engine.  Typical descent is at 25 inHg MP.

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@downscc What's the problem with the props turning the engines? Isn't that the same as a car going downhill in low gear?

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31 minutes ago, xender said:

@downscc What's the problem with the props turning the engines? Isn't that the same as a car going downhill in low gear?

Good question.  No it is different. In general, geared aircraft engines will be damaged if the prop turns the engine.  They are not designed for the negative torque.  In some cases you will see damage very quickly.  Even the geared turboprops like the J41 keep the torque positive.

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Then that must be my problem. I use idle power. I even have to push the gear button to silence the gear horn. That must be it.

thanks!

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You will have more fun flying the aircraft after reading through the manual and look at the traffic patterns to give you a feel.

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The rule is to keep MAP min equal RPM/100 as a wind change may change the load on the props. The faster you fly the better to keep an additional margin like 22 over 2000.

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1 hour ago, metzgergva said:

The rule is to keep MAP min equal RPM/100 as a wind change may change the load on the props. The faster you fly the better to keep an additional margin like 22 over 2000.

Can you explain better this interesting rule? Thanks.

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The rule is good, the BMEP indicators are better and way more easier. :biggrin: Just keep a positive reading on your BMEP instruments (over 60) and you'll be fine. For descending, I keep my BMEP readings between 80 and 100. That's a setting of about 25" @ 2250RPM. 

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Good topic... descents require planning.  Not at all like waiting for TOD based on some distance rule of thumb, but you actually should be calculating time distance and speed even if only in your head.  A good example was my recent trip in the C118 from Lake Tahoe KTVL to Montery KMRY.  Tahoe is on the edge of a 6000 ft elevation lake surrounded by mountains and Montery on Southwest about an hour on the coast.  Departure requires a climb above 11000 to clear the mountains, and I climbed to 12500 in VMC conditions. Once over the central valley, it is time to start a 500 fpm descent and that put me at just over 3500 ft crossing Salinas SNS with enough room to slow down, get dirty and land on the LOC28L.  In summary, this flight is essentially one constant descent.  It is also very beautiful with Orbx and AS16, and a basic familiarity with the area (I got my PPL in Sacramento in 1975).

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If you run the engines at 2000 rpm your manifold ptressure should be above 20 in. If you fly 130 kts with that setting it is fine. If you do a descent with 200 kts you should add a bit more MAP, like 22 in.

All this to avoid that the airflow will drive the prop to drive the engines with not enough power from lack of throttle position. 

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On ‎10‎/‎17‎/‎2017 at 7:20 PM, metzgergva said:

If you run the engines at 2000 rpm your manifold ptressure should be above 20 in. If you fly 130 kts with that setting it is fine. If you do a descent with 200 kts you should add a bit more MAP, like 22 in.

All this to avoid that the airflow will drive the prop to drive the engines with not enough power from lack of throttle position. 

Alexander... I have noted that the plane is quite difficult to slow down to max flap speed (174 kt) from speeds above 220/230 knots with power settings at 25/2050. Sometimes it requires more thn 15 Nm in level flight to slow down from 230 to 174 in order to select flaps 20. Is the real DC-6 that hard to decelerate? Is it acceptable to reduce the RPM to, let's say, 1800 RPM in order to help it to lose speed more quickly? 

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5 hours ago, RonnieDuck said:

2050 RPM reduce more drag than 1800RPM due to the prop pitch!

I can confirm that from my experience. Higher RPM equals to more drag, which results in faster deceleration. One part of the before landing checklist is to set the props to 2400 RPM. You could do this step earlier than on final approach to slow the Six down. But you have to keep an eye on the BMEP gauges and your throttle settings when increasing RPM, as the BMEP will drop quite a bit. So you might have to add a more power to stay in positive range. But it will still help you to slow down a little bit faster. A RPM setting of 1800 will make you even faster in descent, as there is less drag from the props. Proper descent-planning in the Six is crucial. I mostly use the TOD calculator of the GTN650, works pretty well with a programmed descent rate of 500 FPM. And I always try to go for the lowest possible altitude on a STAR. Once I had to tell a VATSIM-ATC that my descent rate is limited to 500 FPM, after I called for an early descent and he thought that it is way too early. I think I have to add an additional RMK to the flight-plan. :laugh:

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First rule is to keep the engine settings as described. Going down to 1800/20 is a valid procedure and good if you are light to slow down. 

RW pilots said that they calculate 10 NM to slow down from 200 to 175 in level flight approaching the airport. If you take that into your decent calculation you are fine.

Typical decent rates in cruise are 300 ft/min and max 500 ft/min. If you want to fly an ILS (todays procedure not in the 50s) you need to slow down to 110 kts and be configured with gear down and flaps 30 to maintain speed on the glide and have 500 ft/min descent rate. Final slow down by applying flaps down to full for landing.

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21 hours ago, metzgergva said:

RW pilots said that they calculate 10 NM to slow down from 200 to 175 in level flight approaching the airport. If you take that into your decent calculation you are fine..

Interesting to read that part, because from my experience in the sim, I ended up calculating 5 to 10 NM level flight before the IAF for slowing down from about 200 to 175 KIAS. Thats why I always use the lowest possible altitudes on STARs, so I end up getting some level-flight sections. And as soon my KIAS drops below 175, I drop the flaps to 20°. Because in many flights I've ended up way too high and too fast on approach after waiting for too long with dropping flaps and gear. And when the ATC messes up my calculated descent-profile, I mess up his traffic flow by requesting a hold to slow down. :laugh:

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When we fly first times with our DC-3 into GVA we messed up the approach every time and we are 80 in the glide. Now ATC knows the plane and typical gives us radar vector in parallel and low or a short visual, but still then it happen that we have 3-5 five waiting for departure...

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