mserin

I checked the trim. The problem is the runway lenght . The acceleration is much slower as the engine fails and by the time I am at the middle of my rotation like say 6-7 degrees I am at the end of the runway.

Thank you Vagabondo. Your advices were very helpful. If this is the case than the engines are a little bit under powered to practice a V1 CUT at the field limit weight. But I can lift off before the end of the runway when the engine failure occurs at VR. That could depend on your field limit weight that is listed in the performance dispatch section in 737 flight crew operation manual. If you took off from 17R/35L in a standart day with flaps 5 the field limit weight is 63 tons. So if you were at this and took off safely with an engine faliure at V1 weight than maybe I am doing something wrong.

I did another test today with the same settings but and this time I used VR CUT in FMC Failures section and was able to climb out safely. Then I realised that V1 was 147 and VR was 148. So I thought 1 knots of difference shouldn't make a difference that much.I than did a V1 CUT again and I realised that engine failure happened before V1 at about 142 knots. So the problem maybe not in the performance of the engines but in the simulation of V1 CUT. Other than that I think PMDG 737 NGX is one of the the most realistic simulations ever. Almost good enough to be used in training.

I would like to practice non-normal procedures like v1-cut,Rejected takeoff, In flight engine fire. So the performance realism is important. Yes I was using maximum TO power with 737-800. (no derate or assumed tempature)

So a real 737 pilot shouldn't practice with pmdg! Do you know if there a high fidelity and accurate simulation of 737-800 for PC that a training pliot can practice at home with?

Have you ever tried V1 cut at field limit weight ? I have tried v1 cut with a runway of 2200 m. lenght. For that runway at sea level ONH 1013 14 degrees celcius field limit is 74.000 kgs for maximum takeoff thrust of 26k engine. I tried to takeoff with engine failure at V1 and I couldn't get off before the end of runway. The engines maybe producing less power than they should be at maximum takeoff thrust. (The definition of field limit weight states that in case of a v1 cut the plane should be able to rotate and climb 35 feet above ground level by the end of the runway) Do you have any idea regarding what might be wrong?

I have a pilot friend who works for an airline. He is flying 737-400 and 737-800 aircraft. I was able to get a QRH(quick reference handbook) for 737-800 for CFM56-7b26 engine from him.In the "long range cruise section control" section for 75.000 kg gross weight at 31.000 ft the N1 setting should be 87.4 at 0.778 mach and the fuel flow for each engine should be 1414 kg. If you leave the thrust scalar at 1.0 you can get this values with PMDG 737-800. But if you change the thrust scalar to 1.18 than the N1 value becomes something like 79 for the same condition.Also for the climb stage the QRH manual states that around 20.000 ft. with 70.000 kg of gross weight with maximum climb thrust set the vertical speed should be around 2100 ft./per minute for 0.76/280 climb on a standart day. If you leave the thrust scalar at 1.0 you can get this value approximately. But if you change the thrust scalar to 1.18 for the same conditions the vertical speed becomes something like 3000 ft/per minute.

I did a calculation depending on Ron Marks calculation that the thrust is actually 21.900 lbs per engine in PMDG 737-800. It seems that the thrust in reality should be 26.000 lbs per engine. 26.000/21.900 is 1.18. So the thrust should be 1.18 times more than it is now. So in the aircraft.cfg file I replaced the following number with this number:[jet_engine]thrust_scalar=1.0 ( I deleted this number and replaced it with 1.18)With this number replaced I think that the takeoff performance becomes more realistic. But this time I realised that the climb and cruise performance becomes unrealisticly higher than it should be :(

Thank you very much Ron Marks. I am very impressed with your calculations.

I have been thinking of a way to check whether the TO roll thrust is realistic in 737 PMDG or not. I believe that I come up with a solution at last. Every 2 engine jet aircraft must be able safely climb out ( at least to 2000 ft so you can go back to the airport and land) in the event of an 1 engine failure at V1 with the maximum gross weight. So I tried this in 737-800 PMDG. You can also try it yourself. At V1 shutdown one of the engines and try to climb to a safe altitude. I was not able to climb :( At maximum gross weight plane can not climb out safely in the event of an engine failure at V1!! . I believe this should prove that the takeoff thrust in the simulation lower than it should be.

Thanks for the calculations. This is exactly my point. I should be able to takeoff with 75 tons gross weight safely. But in the simulation I can leave the ground at the very end of the runway. I don't believe that in real world this would be considered safe. In case of rejected takeoff just before V1 it wouldn't be possible to stop safely before the end of runway.

I am sorry for the double post . I am new in this forum I did it by mistake. I am calculating the trim setting with the help of the TOPCAT software. I think it's the most accurate and realistic way to calculate trim. But still the acceleration of the aircraft is too slow.

I have been flying PMDG 737-800 in my FS9 for a while.I believe that PMDG has done a great job. I have a problem with the takeoff performance. I have read from the real 737-800 CFM56-7B26 operations manual and have used TOPCAT takeoff performance calculation tool to check my takeoff performance. I should be able to takeoff from LTBA Istanbul airport runway 06(runway length:2300 m.elevation:93ft. ) with no winds, QNH 1013 and 15 degree celcius temperature with maximum 75.000 kg of gross weight. Air conditioning is on and anti ice is off. The optimum flap setting should be 5 degree flap and trim setting (actually depends on the CG) is about 6.0. N1 is 98.1 %. Rotation speed is 151 kt. But in the the simulation even when I make the air condition and engine bleed off the takeoff is most often at the very end of the runway when there's only about 50 meters of pavement is left which is neither acceptable or can be considered safe. I live in Istanbul and I see lots of 737-800s which are I believe at least 70.000 kg ( because I know that some of them have destinations at least 2000 nm away) can takeoff on a standart day at the middle of the runway 06. Only after about 1200 meters takeoff roll they can reach rotation speed.

I have been flying PMDG 737-800 in my FS9 for a while.I believe that PMDG has done a great job. I have a problem with the takeoff performance. As I have read from the real 737-800 CFM56-7B26 manual and have used TOPCAT takeoff performance calculation tool I should be able to takeoff from LTBA Istanbul airport runway 06(runway length:2300 m.elevation:93ft. ) with no winds, QNH 1013 and 15 degree celcius temperature with maximum 75.000 kg of gross weight. Air conditioning is on and anti ice is off. THe optimum flap setting should be 5 degree flap and trim setting (actually sepends on the CG) is about 6.0. N1 is 98.1 %. Rotation speed is 151 kt. But in the the simulation even when I make the air condition and engine bleed of the takeoff is most often at the very end of the runway when there's only about 50 metres of pavement is left which is neither acceptable or can be considered safe. I live in Istanbul and I see lots of 737-800' which are I believe at least 70.000 kg ( because I know that some of them have destinations at least 2000 nm away) can takeoff on a standart day at the middle of the runway 06 only after about 1200 metre takeoff roll they reach rotation speed.