GDex wrote on Feb 11^th, 2011 at 3:50am:

Michael I have downloaded your B727-200 mod package, but I have a question. I compared the data in the current aircraft.cfg file and the one you propose. I notice that you have reduced the weights (max, empty and max_zf to nearly the same values as the -100. Is that necessary? Does that represent the real -200? In the first place, what drew me to your post in the forum were the problems I am having with controlling this aircraft, which is new to me. I was trying to do a flight from Toronto (CYYZ) to Montreal (CYUL), about a 1-hour flight. My payload was as follows: •      155 passengers at 180 lbs = 27,900 lbs •      4 3,000 lbs containers (2 front, 2 aft) = 12,000 lbs. •      Crew = 510 lbs •      Total payload = 40,410 lbs I loaded 18,500 lbs of fuel, spread equally amongst the 3 tanks. The problems I encountered are: •      Climbing beyond 25,000 ft. was very difficult. I managed to reach only 31,000ft in about 18 minutes from takeoff. •      Once in the cruise portion, I tried to maintain a constant speed of M0.8, but the speed kept changing up and down, so I constantly had to adjust the throttle. I was on real weather, but the winds were pretty constant. I never have such variations in other planes (C-130X, B-52). •      When descending, I found it hard to slow the airplane and had to use the speed brakes to reduce the speed once I got below 10,000 ft. (Incidentally, the speed brake lever does not work. I had to use a keystroke. Is that a known bug?) •      In the turn from the base leg onto final, it slowed down very rapidly from 150 Kts and I lost it; it stalled and crashed. My flaps were at 15° when I was at 150 Kts. Is this the normal behaviour for this plane? Or am I doing something wrong? Or is it something that your mod would fix?

All of the information I used comes from Boeing and airline manuals for the real aircraft, and some material taken from the engine manuals as well.  As for the weights, they are accurate.  The 727 200 Advanced had a significantly higher maximum weight, but that is not the aircraft I modeled. See page 5 of the following document from Boeing as to weights:

http://www.boeing.com/commercial/airports/acaps/727sec2.pdf

Your total weight was 194,000 lbs which was more than 20,000 lbs in excess of the maximum takeoff weight.  In the readme I noted that it quite easy to overload the basic 200 model and that you should check to see that you haven't done so in the FSX fuel and payload dialog.

I don't have detailed climb performance charts for the 200 with JT8D-9 engines, but I do for the 100 and for a 727-100 starting at 170,000 lbs with JT8D-7s, the climb to FL310 is 21 minutes at standard temperatures, so I am not sure why you perceive your results to be a problem.   If anything the climb performance may be too good based on your figure, although I wonder if you used more than maximum climb power since you perceived the performance as deficient?

My figures are from a Boeing performance manual.  Climb above 25,000 feet is only going to be around 1000' feet per minute.  That is the performance of the real aircraft.

As for the cruise behaviour, there is nothing in the flight model that could cause varying speed with a constant power setting.  And I have yet to experience "pretty constant" winds aloft with any of the weather programs I have tried.  Try again with "clear" weather, which has no wind at all, to see if in fact you really have a problem with this.

I can't use the mouse to operate the speed brake lever either -- I have to either use a key or a joystick slider, but I haven't done anything to cause that problem.

I don't find that I need speedbrakes to slow down. I start descending at 2,500 fpm at 290 knots at 55% N1 (which is the desired behaviour). I set the autopilot for that rate of descent and reduce it to about 2000 fpm at 20,000 feet and 1,500 fpm at 15,000 and then 1000 fpm under 10,000.  You will not need speed brakes if you do that.

With flaps 15 in level flight you need a fair amount of power.  I have two unreliable airspeed charts for the 727-200.  The one says you need an N1 of 74 and 7' of pitch at 150 kias at a typical weight.  The other chart is more detailed and shows for a weight of 160,00 lbs:  EPR of 1.43/N1 of 74 and 7' pitch at 160 kias.  I have tweaked my flight model to approximate these figures.  And of course if you are turning with a lot of bank angle you are going to have to increase your power from those figures in the turn.

So I think that yes, you are doing something wrong.