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GrizzlyAir

Planning a step climb

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Stupid question time:  I am trying to figure out the charts at the end of the POH to plan my step climb to my cruise alt to pick up some speed.  

I cannot figure out what charts charts to use to figure out my climb power and the service ceiling for the particular weight to maximize my climb.  

Climbing to a higher altitude in a prop isn’t going to add to your range like in a jet.  Your fuel burn is roughly the same at altitude, but I will have a higher TAS, so to maximize efficiency, I want to maintain the highest TAS I can for my weight at a given moment.   So I want to climb to my service ceiling for the weight I am and then climb again when I’ve shed enough fuel weight to raise the ceiling.  How can I plan that and how do I use those charts?  

one Set of charts says METO then 1500, 1400 etc   So meto maximum except takeoff power, maximum cruise power essentially for the climb, what are the other numbers?  Not v/s

 

 

then there are a set of charts that are listed as torquemeter horsepower   What are those for?

 

thanks   Sorry for asking a stupid question, I’m sure it’s obvious to you prop geniuses  i just can’t find the answer 

 

 

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No stupid questions Grizzly (make sure to include your real name in the PMDG support forum), only stupid silences!

Unless you want to run your engines incredibly hard, METO is generally not an acceptable climb power setting. The numbers you see reference the BHP the engines will produce. 1500 Climb = a climb power setting which results in 1500hp per engine. 1400 Climb = 4x1400hp in climb. In these aircraft, you(or the operator) will make economic choices between higher power and performance, or decreased performance and with reduced engine wear in lower power. There are many different ways to fly the DC-6B, but my suggestion is to use the "Speed Altitude Table" on p.285 to compare your weight and chosen cruise horsepower to find an appropriate altitude. Then, use the power chart at your chosen horsepower to determine the MAP/RPM/BMEP settings required to deliver the desired power output.

Robert Toten

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And how do you determine horsepower?  It’s not bmep, right?  

 

 

 

Brian Smith

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Posted (edited)

I prefer using the charted constant HP charts on p. 300-312, or you can use the engine settings depicted on the "Level Flight Cruise" Charts on p.290-293 (HP is depicted in the chart title). If you really want to be accurate, you can use the DC-6 Power curve chart on p.287.

In all cases, what you're doing is finding your desired power output, and then using the charts to determine the MAP/BMEP/RPM combinations which will produce the desired horsepower. There is not gauge in the aircraft which measures HP directly, you have a fair amount of discretion in engine operation (within limitations).

 

Robert Toten

Edited by randomTOTEN

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Thank you!   I think I understand now.  Appreciate it.  So it I want to climb at 1100 BHP, for example, and takeoff at sea level, and the OAT is 11 C, and the carb temp is 31C, I use BMEP of 37.4 during my climb...right?

 

 

Brian Smith

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Posted (edited)

What chart are you using to get this answer? I think there might be some problems with your example, but it would be helpful to understand how you got this solution.

 

Robert Toten

Edited by randomTOTEN

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Hallo Brian,

I would say: 37´´ MAP/2000 rpm/154 BMEP with LOW Blower (see Chart p 304)

Robert correct me if I´m wrong.

Rainer Burg

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POH page 278 DC6 Power Curve, note the enroute climb is 2400 RPM 185 BMEP (1400 BHP).  Be sure to open the cowls to 3 deg and set auto rich mixture.

As for step climbs.... not normally done.  In fact you want to be a low as possible for the best speeds.  Opposite of what you're used to in a turbofan.  Even the C-414 goes fast the higher you go but it is turbocharged and the DC6 has superchargers. Big difference.  Normal operations you only go as high as you need to for terrain or weather avoidance.  Some current operators have stripped the pressurization out of the aircraft altogether.

I usually fly her at 1100 BHP with a power setting  from page 291 POH.  I always use BMEP for setting power, I think there is a bug in the manifold pressure that will be fix but isn't yet.  BMEP is directly related to BHP by this formula:  BMEP = (BHP * 282.45) / RPM.  In fact, the BMEP gauge is actually a torque meter in disguise which is why the formula includes a time (RPM) variable to get from torque to power.  So for a typical flight over the plains I'll be at 7500 - 8500 and my power will be 2010 RPM 155 BMP 500 lbs/hr burn/engine and I might see about 240 KTAS.  Note on the chart that your fuel consumption increases with altitude, not decrease as does a jet.

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Posted (edited)

I'll get to Dan's statements in the next post, but I'll address some other stuff here:

Grizzly I've noticed you've made no mention of RPM settings in this discussion (especially your attempted calculation) I just want to reiterate that the position of the propeller master control is just as important as that of the throttles and mixtures, and you should remember that they are essential in setting the correct cruise or climb power. You must set the correct RPM! As Dan has mentioned, BHP is defined by both a torque and RPM.

Ranier,

I agree with your calculation, although I couldn't find a BMEP value using chart p.304. I did use the "Level Flight Cruise (1100 hp)" chart on p.291 and got a value of 155, so I consider that value to be accurate as well. But there's one more imporant thing I want to highlight in this discussion,

On 7/6/2018 at 8:36 PM, GrizzlyAir said:

So it I want to climb at 1100 BHP, for example

Grizzly you're going to be frustrated if you try and climb with 1100BHP. That's a cruise power setting, not a climb power one. Use 1400, 1500, or METO (not recommended for long periods).

Just to clarify, you would maintain level flight using your desired cruise power. Once you determine (using p.285-286 for example) that you can maintain a higher altitude, you will then transition to your chosen climb power...climb to the new desired cruising altitude... then reduce to the newly calculated cruise settings (likely same cruise HP) once the aircraft has accelerated beyond the lower climb speed.

 

Dan, I disagree with you on the benefits of flying at low level in the DC-6B vs. high altitude. I can either make the argument in this thread or a new one if you like.

Suffice to say that Douglas Aircraft installed a very capable and expensive pressurization system, and complex (expensive) highly supercharged piston engines..  it makes little sense that they or their operators would spend all this money so original customers would cruise around at 7,500' MSL. With scarce parts, and many pressurization cycles I can understand why modern examples would have inoperative pressurization and high supercharger gears.. but flight simulation users which desire to replicate period operations shouldn't need to be burdened by these restrictions.

 

Robert Toten

Edited by randomTOTEN

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Hello Robert,

thank you for your feedback.

for the BMEP number I just took the last specified # for BMEP on p. 302 (166) minus the specified "BMEP DROP" (= 12) on p.304: 166-12 = 154 for BMEP @1100 HP.

Of course you are right, that are no climb figures but cruise settings.

Cheers Rainer Burg

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