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Post by charliealfatango on Mar 25, 2021 23:03:28 GMT -5
Greetings
Need some directions. In the fsx reference for 737-800 it says the landing speed for 180,000 lbs gross weight at flaps 30 should be 109 KIAS. I tried that and I don't think that is accurate. Its too slow and the aircraft pitches up at an awkward angle. The landing speed at flaps 40 setting is listed at 157 KIAS which is a little fast specially when you try to flare about 50ft above the runway, the aircraft starts to climb.
Where can I find the correct numbers to configure the aircraft for an approach. The weight of the aircraft with fuel is 174,000 lbs. Trying my test landings at KUKF about 7,000 ft runway.
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Post by peter on Mar 26, 2021 3:47:53 GMT -5
Hello Charlie,
this sounds like you are using the default 737 in FSX? If so, then you should simply ignore any numbers you may find since the default model is grossly inaccurate. I recall, for instance, that fuel burn is about twice as much as that of the real airplane.
As for the speed: you are right, 109 Kts is too slow for an airplane of that size. Generally, there is no fixed landing speed for airplanes, it depends on the actual weight of the airplane, air temperature, and altitude of your destination. High-end models like the PMDG 737-800 simulate this quite accurately, and they come with extensive documentation (the manuals have 2000 pages or so) where you can find this information. If you are landing at sea level and normal temperatures (10-20 C), a landing speed of 135-150 Kts should be ok.
If you plan to use the airplane for a lot of flights, I suggest to find out a good landing speed by trial and error. As a rule of thumb, if you are too fast, the airplane will likely bounce. If you are too slow, you can't see the runway anymore with the normal view point.
Cheers,
Peter
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Post by charliealfatango on Mar 26, 2021 7:39:09 GMT -5
Hello Charlie, this sounds like you are using the default 737 in FSX? If so, then you should simply ignore any numbers you may find since the default model is grossly inaccurate. I recall, for instance, that fuel burn is about twice as much as that of the real airplane. As for the speed: you are right, 109 Kts is too slow for an airplane of that size. Generally, there is no fixed landing speed for airplanes, it depends on the actual weight of the airplane, air temperature, and altitude of your destination. High-end models like the PMDG 737-800 simulate this quite accurately, and they come with extensive documentation (the manuals have 2000 pages or so) where you can find this information. If you are landing at sea level and normal temperatures (10-20 C), a landing speed of 135-150 Kts should be ok. If you plan to use the airplane for a lot of flights, I suggest to find out a good landing speed by trial and error. As a rule of thumb, if you are too fast, the airplane will likely bounce. If you are too slow, you can't see the runway anymore with the normal view point. Cheers, Peter Thanks, trial and error is what I ended up doing. Target kias turned to be 145 with flaps 40. KUKF is a runway that is almost at the limit for 737-800 - it is only 7000 feet, I wanted to land and stop without using the auto-brakes. But I guess the heavier the plane the faster the landing speed, which means either I will need to use the auto-brakes on short runway. I wonder where they came up with 109 kias @ flaps 30. |
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Post by peter on Mar 27, 2021 3:30:11 GMT -5
Hi Charlie, I am glad you found a good landing speed. I have done a lot of data analysis for FSCaptain configuration files and I was surprised just how often there are basic mistakes in flight sim models. Even well known third-party developers often don't get the numbers right. My wild guess for the 109 Kts entry is that they first modelled a 8-15 seat turboprop or light business jet (that's the type of airplane that has such a landing speed) and then copied the files for the 737 without reviewing it properly. Yes, landing and takeoff speed depend on weight and temperature as well. The lift force created by the wings is (mostly) what needs to overcome the weight force. Since the list force grows with speed, larger weight means larger takeoff and landing velocities. Lift is basically generated by wings pushing air molecules downwards. Warmer air, as well as the air at high-altitude airports, is less dense, so there are fewer molecules to be pushed. Hence, the plane needs to be faster to generate enough lift. Yep, 7000' is not very long for a 737-800, but it should be fine for landing. Generally, brakes work better at decelerating a plane than engines at accelerating it, so the takeoff distance is more critical (unless you want to retire the airplane at KUKF  ). In the FSCaptain dispatch release, you may find an estimate for the takeoff roll that takes into account weight and air density (under "remarks"). My guess would be that to depart from KUKF, you need to limit the amount of payload for your next flight. Cheers, Peter |
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Post by alaskanflyboy on Mar 28, 2021 5:21:31 GMT -5
You would use manual brakes on a short runway as max manual braking is always shorter than max auto. You can land the 737 on some short runways (KMDW comes to mind), but you need to be on the money with flaps 40, speedbrakes armed to deploy on touch down, and ready to stomp the brakes and deploy thrust reverser at full thrust as soon as the nose wheel touches down (hit brakes fully too soon and you're prone to slam the nose down and cause damage). At least with the default B738, you don't have to worry about the brake temps as you do with the PMDG NGX/NGXu. Unfortunately, the default 737 is poorly modeled, but you can try using the free 737 OPT at www.737efb.online. The Onboard Performance Tool is what a real 737 crew would use to calculate reference speeds and landing distances. The "Landing - Dispatch" page will give you your landing weight limits for pre-flight planning while the "Landing - Enroute" page will give you calculated landing distances for each auto brake mode and max manual braking. This is all typically calculated before decent, but I don't remember if the default 737 has much of an FMC to determine current and anticipated weights. I always plan with my ZFW plus the anticipated fuel at my destination from the Progress page on the FMC to run the calculations. Say my ZFW is 123.8 and my expected fuel at the destination is 7.4, I'll enter 131200 lbs in the OPT. |
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Post by Travis on Mar 29, 2021 12:29:44 GMT -5
John's correct of course on short runways. Step heavily on the brakes when you make contact and go to full reversers ASAP; have your speedbrakes already armed and ready. My ISG gauges give me an estimate of fuel at my arrival, so I'll give that online calculator a try when I next use my tricked-out default B738. But overall, when it comes to any discussion of flight sim aircraft performance, I keep thinking back to the joke from the 1950s or 1960s.... Question: "How do you get to Carnegie Hall?"
Answer: "Practice, man, practice!" www.carnegiehall.org/Explore/Articles/2020/04/10/The-JokePractice is always a good thing - repetitive attempts to achieve a goal... but always with a measurable goal in mind.... There are two shareware programs which I've used to help me in landing medium to large aircraft. One is a "landing practice" add on that helps to test various landing conditions. The other is a "master braking controller" to help achieve a runway-exiting speed against a specified runway exit location. Soon after I became an FSCaptain (that was in 2010, so I'm thinking of sometime in 2011 or 2012) I came across a shareware program which simulated an RAAS module, and I was impressed with its utility and simplicity. A year or so later I noticed its author had a shareware "landing practice" add on which allowed you to specify the airport, the runway, the distance from the runway to begin, and possibly an offset angle. I started using the landing practice module with the strange-to-me name of "Lord of the Landing". The way I used the "landing practice" add on was to turn off all AI (so no one would bother my practicing), and spawn on the runway I wanted to test for landing. I would then set up all my Nav frequencies and courses, heading, etc. and let the add-on know that I was ready to go. It would then zap my aircraft to the position in question, where I would stabilize things and proceed with my plans for flaps, speeds and braking. Capture the localizer and then the glideslope if an ILS is in use, and fly down to the runway watching AOA and speed.... Eventually for my default 737-800 I settled on a basic approach with Flaps 30 or 40 at 142kts Vref. My flaps setting and braking / reversers choices would depend on the runway length and winds as the "landing practice" add-on would guide me. It's good to test different weather conditions as well - especially "max crosswind" conditions! Years later, the author came up with another add-on to simulate the "Brake to Vacate" software on newer Airbus aircraft. This add-on asks you to specify the airport and runway you wish to land upon, and also to specify the intended taxiway for runway departure along with the groundspeed you wish to have upon exiting the landing runway. You would need to refer to a chart or an EFB to see the taxiway exits for the runway where you intend to land. This add-on appears to automatically manage the braking pressure needed to bring you to the selected groundspeed at the distance calculated for the selected taxiway. Autobrakes aren't necessary, and use of speedbrakes and reversers certainly help the process. (If your aircraft have them!) Yes it's a bit of a cheat for those of us not flying Airbuses, but as I'm flying pandemic-ly modified CRJs with 40% capacity ( albeit with business class seating!) I assume that my airline can afford wizardly technical upgrades.  All of these add-ons work with FSX and P3D 4.5. The author's name is Dongjin Shin. (And FWIW, we've never conversed.) Best, |
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Post by Travis on Apr 1, 2021 23:32:30 GMT -5
At least with the default B738, you don't have to worry about the brake temps as you do with the PMDG NGX/NGXu. We should chat about this sometime. "Brake temps" are an irritant of mine.  Not the only one, either.... Best, |
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). In the FSCaptain dispatch release, you may find an estimate for the takeoff roll that takes into account weight and air density (under "remarks"). My guess would be that to depart from KUKF, you need to limit the amount of payload for your next flight.
