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scandinavian13

[08SEP16] Flight Planning Tools

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In case some of you didn't know, there is actually a performance profile for PFPX included in the documentation folder of the DC-6. If you need help on where to put the files, look to the Intro Manual in the same folder.

 

All the same, some prefer to use the free - and very well put together - SimBrief site to plan their flights. Have a look at the aircraft list near the bottom. They now have a DC-6 profile available for your flight planning needs.

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I was just looking at SimBrief the other day in the hopes that they would include the DC-6 profile. Thanks so much for the heads up!

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I really like SimBrief, however they seem to always put my cruise at FL120, no matter how long/short the flight...

 

When do you guys stay down low, when do you climb higher?

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Stefan,

 

The DC-6 is a prop, not a jet. While it has superchargers, it doesn't get anywhere near the compression that a jet does, so efficiency is actually lost at higher altitudes. It is most efficient from about 8000 to about 12000 feet. You can see this reflected in the performance tables if you do a little math on the fuel numbers.

 

It does possess the capability to go much higher than that, but in the case of a piston engine, capability does not mean efficiency. Cases where you'll climb higher: wind is more favorable, terrain, low weather (clouds below you containing ice, etc.).

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This topic was of interest to me during testing, because the DC-6 performance is not analogous to the turbocharged C-414 that I've flown for a decade.  The difference supercharging vs turbocharging.  The supercharger is engine driven and has conventional throttle to control manifold pressure.  It takes a lot of air to feed those big radials and I don't think turbochargers were a thing yet.  However, with turbocharging the waste gas (exhaust) drives the air pump and manifold pressure is controlled by a waste gate, close the gate and MP rises. The waste gate dumps the air from the pump overboard that is not required to sustain the desired MP.  By the way, there is plenty of air to also pressurize the aircraft. The supercharged engine looses MP with altitude, and you continue to open throttle to maintain a setting until 'critical altitude' whereas the turbocharger automatically adjusts the waste gate to hold MP all the way to aircraft ceiling.  This allows the turbocharged engine to perform the same a sea level as it does at FL250 and since the air is thinner the TAS increases significantly.  Set power at 75% and I'd get about 160 KTAS at 8000 ft but go up to FL230 and the same power and fuel I'd get 200 KTAS.  The DC-6 cannot take advantage of this TAS increase because the engines feel the effect of altitude.

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I remember years ago in DC-6 Basic First Officer new hire school our instructor on power plants drove the point home quite well as to the difference between the DC-6 and the DC-7.

"Well, the best way to tell the difference between a DC-6 and a DC-7 when they're taxiing on the ground at a distance is if the plane is being followed by fire trucks it's  probably a DC-7."

The DC-7 had what was, at least at that time, the most powerful and complicated propeller engine in history. It had an engine power optimizer lacking on the DC-6 which allowed it to operate economically at much higher altitudes. The engine section that permitted this increase in altitude was called the "Power Recovery Turbine or "PRT".

It had the unfortunate habit of "melting down" and catching fire with not uncommon regularity...............very expensive  to repair!

This is one of the reasons that the DC-6 flew for three or four years longer with my airline than the DC-7.

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