Announcement

Collapse

PMDG Forum Rules

1) SIGN YOUR POSTS. Since 1997, we have asked users to sign their real name, first and last, to all posts in the PMDG forum. We do this in order to keep conversations personal and familiar. You took the time to be here, we want to get to know you. This is one of the few rigid rules that we enforce regularly. We do so because we feel that forums in which users must engage one another personally are generally warmer, more collegial and friendly. Posts that are unsigned will be quietly removed without comment by the moderators, so to make your life easy- we recommend enabling your forum signature so that you never need to remember. Do this by clicking the username pull-down at the top right, then selecting "User Settings." You will find the signature editor on the ACCOUNT tab, about half way down the page. Look for "Edit Post Signature." Be sure to click the "Show Signatures" box.

2) BE NICE. We are all simmers here and no matter our differences of opinion, we share a common love of aviation, computing and simulation. Treat everyone else in the forum with respect even when you disagree. If someone frustrates you, walk away from the conversation or ask for a moderator to get involved. Speaking of Moderators, they prefer not to be treated as "The Thought Police" but if any behavior infringes on the enjoyment of another user or is otherwise considered to be unacceptable in the moderator's judgment, it will be addressed in keeping with our view of ensuring that this forum remains a healthy environment for all simmers.

3) BE LAWFUL: Any behavior that infringes upon the law, such as discussion or solicitation of piracy, threats, intimidation or abuse will be handled unsympathetically by the moderators. Threats and intimidation may, at the moderator's discretion, be provided to law enforcement for handling.

4) BE FACTUAL: When you post, always be factual. Moderators will remove posts that are determined not to be factually accurate.

5) RESPECT COPYRIGHTS: Posting of copyrighted material such as flight manuals owned by Boeing or various airlines is not allowed in this forum. If you have questions related to copyrighted material, please contact a forum moderator for clarification.

6) RESPECT PMDG: We love to hear what you like about our products. We also like to hear what you think can be improved, or what isn't working. Please do tell us and we will always treat your feedback with value. Just be sure to treat the team respectfully, as they do put a significant amount of effort into building and maintaining these great simulation products for you.

7) RESPECT PMDG DEVELOPERS: All of the developers will spend some time here. Given the ratio of developers-to-users, it simply isn't possible for us to answer every post and private message individually. Please know that we do try to read everything, but developer workload is simply too high to manage personal contact with tens-of-thousands of users simultaneously. In most cases, members of the development team will stick to conversations in the forum and will not answer private messages.

8) RESPECT OTHER DEVELOPERS: PMDG has always advocated for a strong development community and we have many friends within this community. Every developer offers something unique that helps to make the simming community larger and more vibrant. We insist that you treat our friends respectfully.

9) RESPECT MODERATORS: Moderators have a tough job, and none of them enjoy having to stomp out negativity. If a moderator has to weigh in to keep a thread peaceful, please respect that effort and refrain from giving the moderator any grief.

10) If you require official support for any of our products please open a support ticket through the support portal, https://support.precisionmanuals.com

11) This forum is designed primarily as a vehicle for the PMDG development team to interact with our customers, and for customers to interact with one another in a manner that is positive, supportive and assists in the general advancement of understanding the simulation and helping to make this and future simulations better. Any other use of this forum is not permitted, including but not limited to discussion of pricing policies, business practices, forum moderating policies, advertising of non-PMDG products, promotion of events, services or products that are not approved in advance by PMDG or any other topic deemed unacceptable by any forum administrator

12) HAVE FUN: This is the whole point of it all.
See more
See less

Maxumum range flight - which flight level and engine settings are applied in reallity?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Maxumum range flight - which flight level and engine settings are applied in reallity?

    Hello,

    I've been trying to figure out, which FL and engines settings should I apply for the flight to maximal range (4100 nm). "DC-6 operation manual" at "Level flights cruise charts" (pages 290-293) advices me flight levels up to FL70 if I would like to get minimal fuel consumption per mile (8,1...7,4 lbs. per mile depending of gross weight).

    Is it right advice and how it compare with behavior of DC-6 in real life?

    As for me, it looks strange when maximal range flight of DC-6 possible up to FL70 only. I belive in real life it is uncomfortable and not so safe to flight at quite big passenger craft so low. As I've read, pilots of DC-6, DC-7 and Connie in 50-60-th preferred FL190-FL210 for commercial flights.

    If talking about PMDG DC-6 in MFS2020, I've tested PMDG DC-6 at different FL from FL100 up to FL230 with engine settings: 2000 RPM, 30 psi Manifold Pressure, Lean. And I got the best cruise fuel consumption per mile (7 lbs. per mile) at FL190! It is better than advices me POH at FL70, and with better speed too (13% faster).

    The question is: which data in closer to real behavior of original DC-6: information from POH or digital model of DC-6 from PMDG?

    May be somebody already figured out in this topic before.
    Last edited by Darkhip; 11Sep2021, 14:07.
    Dmitry Arkhipov

    #2
    Welcome to the PMDG forums, please note the rule you agreed to when joining was that we all must sign our full name on all posts. You can set a signature with your profile options to all appear automatically.

    Please cite your source for DC-6 flights to have been conducted between FL190-210. My copy of the PAA Pan Amercian Operations Book uses 18000 for maximum altitude for routes exceeding 1200 - 1800 nm with 1100 BHP cruise power, and 16000 ft for routes greater than 1800 nm. None of the DC-6 routes in the operations book exceeded 2000 nm, the longest being LAX - Guatemala.

    Look again at your cruise power chart. If you do the math using TAS (in sm/hr) and Time to burn 5,000 lb fuel you will see that the best specific fuel burn rate is at 9000 ft density altitude and decreases with altitude even as the TAS increases. You go high to avoid terrain, some weather or catch a favorable tail wind but you don't go higher to increase range. The DC-6 is not a jet.

    The reason for the increase in fuel use with altitude is simply due to being supercharged. The supercharger requires more and more power from the engine as the air density decreases to maintain adequate manifold pressure. That power drain comes from your fuel tanks.

    By the way, I have no way of checking your claim because I have no idea what 2000/30 provides in terms of BHP. I only fly using power settings from the POH.
    Dan Downs KCRP
    i7-10700K 32GB 3600MHz 2080Ti

    Comment


      #3
      Hello Dan,

      Thank you for your responce!

      Originally posted by DDowns View Post
      By the way, I have no way of checking your claim because I have no idea what 2000/30 provides in terms of BHP. I only fly using power settings from the POH.
      You could very easy to check my math in fuel consumption at FL190 just run the PMDG DC-6 with my engine settings. I guess BHP doesn't matter in this case - I guess for real DC-6 there shouldn't was any possibility to get better fuel consumption in comparison with "cruise level charts" in POH. From my point of view, the better settings should be in POH. Otherwise, why is this book needed?

      Or I'm wrong and for real DC-6 there was really possible to get better performance than it was cite in charts of "operation manuals"?
      Last edited by Darkhip; 11Sep2021, 22:01.
      Dmitry Arkhipov

      Comment


        #4
        Originally posted by Darkhip View Post
        Hello Dan,

        Thank you for your responce!



        You could very easy to check my math in fuel consumption at FL190 just run the PMDG DC-6 with my engine settings. I guess BHP doesn't matter in this case - I guess for real DC-6 there shouldn't was any possibility to get better fuel consumption in comparison with "cruise level charts" in POH. From my point of view, the better settings should be in POH. Otherwise, why is this book needed?

        Or I'm wrong and for real DC-6 there was really possible to get better performance than it was cite in charts of "operation manuals"?
        Uh? The POH cruise power tables include TAS and time required to burn 5,000 lbs. It's not rocket science to find the optimum no-wind density altitude. Take for example 1100 BHP at 9000 ft where TAS is 250 mph at light weights (67500-72500 lbs) and it takes 2.5 hr to burn 5,000 lbs. Convert mph to knots and yo get about 217 nm per hour. So that 5,000 lbs of fuel will get you 542.5 nm. Take your 19000 density altitude where TAS is 274 mph (238 kts) and that 5,000 lbs of fuel gets is burned in 2.27 hr so you only get 540.3 nm. Your distance flown on the same amount of fuel is less in no-wind conditions. As a matter of fact, the best specific fuel consumption is at 9,000 ft density altitude regardless of power setting.
        Dan Downs KCRP
        i7-10700K 32GB 3600MHz 2080Ti

        Comment


          #5
          Originally posted by DDowns View Post

          Uh? The POH cruise power tables include TAS and time required to burn 5,000 lbs. It's not rocket science to find the optimum no-wind density altitude. Take for example 1100 BHP at 9000 ft where TAS is 250 mph at light weights (67500-72500 lbs) and it takes 2.5 hr to burn 5,000 lbs. Convert mph to knots and yo get about 217 nm per hour. So that 5,000 lbs of fuel will get you 542.5 nm. Take your 19000 density altitude where TAS is 274 mph (238 kts) and that 5,000 lbs of fuel gets is burned in 2.27 hr so you only get 540.3 nm. Your distance flown on the same amount of fuel is less in no-wind conditions. As a matter of fact, the best specific fuel consumption is at 9,000 ft density altitude regardless of power setting.
          It's clear. If looks to "cruise charts" the best fuel consumption is at 9,000 ft, I don't argue with it.

          But when I climb "digital" DC-6 in MFS2020 to FL190 with disabled weather without wind and temperature influence, with 2000 RPM and 30 MP (Lean) I get 242kt GS (it's equal 242kt TAS in no-wind case, right?) and fuel flow about 430 lbs/hour. You can check my results. It's better than 217kt and 500 lbs/hour from "cruise charts" at 9000ft and this can't be in reality, right?

          It turns out that the "digital model" of DC-6 is unrealistic?
          Last edited by Darkhip; 11Sep2021, 23:39.
          Dmitry Arkhipov

          Comment


            #6
            No, the model is very realistic. This is an area we worked on extensively during beta to get it right. I reproduced your test run using standard atmosphere no-wind conditions. At 19000 ft density altitude -22.64C OAT 2003 RPM / 30 inHg MP / 138 psi BMEP, weight at beginning of test trimmed at altitude 71,000 lb. Indicate airspeed of 185 kts calculates out to 249 kt TAS. Timed the fuel burn for 5 min resulting is 147 lb total burn, equivalent to 1764 lb/hr or 441 lb/hr per engine.

            Knowing BMEP and RPM the formula for BHP is (BMEP * RPM) / 282.45 = 978.6 BHP.

            The nearest power chart is for 1000 BHP where power setting is 2070/133 psi with 495 lb/hr burn rate and TAS 263 sm/hr (228.5 kts).

            Comparing your speed at 979 BHP of 249 kts with 1000 BHP 229 kts indicates an 8.7% improvement over book value. Not bad but not unrealistic either.

            Comparing your burn rate of 441 lb/hr with 1000 BHP book value of 495 lb/hr indicates a 10.9% improvement. That is bordering on too much improvement for a 2% decrease in power.

            The test run will burn 5,000 lb fuel in about 2.83 hr, compared to 1000 BHP time of 2.53 hr. At least that is in the ballpark.
            Dan Downs KCRP
            i7-10700K 32GB 3600MHz 2080Ti

            Comment


              #7
              Originally posted by DDowns View Post
              No, the model is very realistic. This is an area we worked on extensively during beta to get it right. I reproduced your test run using standard atmosphere no-wind conditions. At 19000 ft density altitude -22.64C OAT 2003 RPM / 30 inHg MP / 138 psi BMEP, weight at beginning of test trimmed at altitude 71,000 lb. Indicate airspeed of 185 kts calculates out to 249 kt TAS. Timed the fuel burn for 5 min resulting is 147 lb total burn, equivalent to 1764 lb/hr or 441 lb/hr per engine.

              Knowing BMEP and RPM the formula for BHP is (BMEP * RPM) / 282.45 = 978.6 BHP.

              The nearest power chart is for 1000 BHP where power setting is 2070/133 psi with 495 lb/hr burn rate and TAS 263 sm/hr (228.5 kts).

              Comparing your speed at 979 BHP of 249 kts with 1000 BHP 229 kts indicates an 8.7% improvement over book value. Not bad but not unrealistic either.

              Comparing your burn rate of 441 lb/hr with 1000 BHP book value of 495 lb/hr indicates a 10.9% improvement. That is bordering on too much improvement for a 2% decrease in power.

              The test run will burn 5,000 lb fuel in about 2.83 hr, compared to 1000 BHP time of 2.53 hr. At least that is in the ballpark.
              Thank you for your detailed answer!

              I will be imagine I've got best engines from stock and filled it improved oil and high-quality fuel
              Dmitry Arkhipov

              Comment

              Working...
              X