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JSACKS

Reasonable thrust fix for 737-200 by FFX

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I've been thinking about what to do with the gorgeous new B732 FFX model because the IAS decays severely during climb to cruise especially with heavy fuel. Somebody kindly responded to my post recently and suggested I change the Turbine Engine Data to 22900 in the aircraft.cfg file. I didn't do this since it struck me that this would overpower the 732 quite massively.Since then, I've fiddled with some alterations and after experimenting, I have settled on a thrust entry in the turbine engine data field of 18000 (compared with the default 15900). This allows me to climb a typical profile with heavy fuel without losing IAS on the way up. I think 18000 is optimal for this a/c. As an example, using FSNavigator, with the following: Commanded Cruise FL=330; climb speed=IAS 270; VS (average)=2000 fpm. Departing KIAD with 90% fuel (ToW of about 102K lbs), this allows you to reach FL330 at IAS 263-264 (FSNav seems to climb one slightly below the commanded IAS). My observation is that as soon as N1 exceeds 90-91% and is rising with high altitude climb, then IAS starts to decay with this aircraft. I reached N1 of 90% at around FL300, if I recall correctly. At about FL315, IAS started to decay a fraction. It had been steady at 264 from around FL230 and it fell 2 knots during the next 1000 feet of climb, recovering rapidly as we approached FL300 and the a/c pitch eased forward.Now cruising at FL330 where the N1=75% and fuel flow=2270-2280 per engine. These data are lower than they were with the default thrust setting of 15900 (which incidentally cruised me at textbook data that was impressive), but tolerable. Fuel flow at the current weight of 100K lbs would be around 2500 lbs per engine, about 10% higher than me and also at Mach 0.72 whereas my IAS now equals Mach 0.75.OK, so it's not perfect but it was more important to me not to bleed IAS on the way up than it is to cruise with perfect data. Prior to this, my IAS had bled off to IAS 231 by the time I reached cruise which was an unacceptable speed bleed. Two caveats with this engine adjustment: I shall now have to rotate somewhat quicker and pitch up more on climbouts; and I shall have to approach with lower N1 to compensate for greater engine power now. Nothing I can't manage quite easily.Overall, however, this is a good solution for me with no real work so I wanted to post it for others who are interested.Cheers!JS

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Sorry, made an error above in text. I meant to say:Climbing at IAS 264 from FL230, IAS remained constant to around FL315 and recovered the 1-2 knots it had lost just before levelling off fully at FL330.Too much data in the post...!JS

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I've noticed the same problem as well. I agree the models are spectacular, but they don't even get to cruise speed. Mine stay at about mach .65.I have a book on the 737-200 that shows the JT8D-9A engines as providing 14,500 lb of thrust. This is what the FFX models come with. The later more powerful variants were the JT8D-15 at 15,500, the JT8D-17 at 16,000 and the JT8D-17R at 17,400 lbs. of thrust.Perhaps we can just upgrade the model to one of the later engines using the Aired program.By the way, I've put the new Ariane analog panel on my FFX 737-200s, a great fit!Lee

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The problem with the FDE is not the thrust rating at all, but rather the inlet area was kept the same as the default 737-400 (19.6) which is typical of CFM56 engines, but the old P&W jt8d9a's were a much smaller engine with a much smaller inlet area. I have been perfecting my FDE for the YeoDesigns 732v2 and have the Turbine Engine Data set up as it should be. A number of 9.5 in the inlet area seems to be a perfect combination for the 14,500 lb thrust rating.Regards,Van LatendresseYeoDesigns Panel/FDE Designer

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Van:Sorry, what are you implying that the inlet area does if you shrink it to 9.5 for the B732? Does the existing YeoDesigns 732 suffer from a similar speed decay on climb as the FFX type?JS

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From reading all this, its apparent that your still using the old dynamics that came with the aircraft on its original release and still being put out there on the repaints. There is a new updated flight dynamics file in the library. You must've missed it. Be sure to read all the notes I put in there. This will prevent my getting emails about not being able to do stuff.mike@sgair.nethttp://sgair.net/images/member_name_banners/mike_small.jpg

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If the inlet area is much larger than the thrust rating you get serious performance problems, especially at higher altitudes. The original FDE of the YeoDesigns 732v2 had these problems and they have been resolved since I took over as the FDE designer.Regards,Van LatendresseYeoDesigns Panel/FDE Designer

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Mike:Thanks for the advice. Didn't know that.The AVSIM library search function remains almost as bad as in the good ol' days. I'll try to find the update ....but won't be surprised if I can't !Cheers!JS

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OK, just to be sure we're on the right track: the file I downloaded originally was called "b7320fx.zip" and it was 13.9MB and had about ten aircraft in it. It had 345 files in it and unpacked was 71.6MB. The cfg file was dated 3/16/2003.Has there been a subsequent update of this huge file that I've missed?If so, what file should I be looking for?Appreciate advice, thanks!JS

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Mike,Separate but related question. Using the update file, is there a way to change the number of weight stations and keeping the airplane stable. I've attempted is using ACLoader, but it results in the airplane sitting on its tail. I've both reduced and increased the number of passengers in it. Dave Vega

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In reference to Van's post above, the change of the inlet area to 9.5 does the trick. I tried and was able to get mach .74 at FL230 without any problem. Finally the solution. Thank you Van.Lee

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I did the update above and can hit mach .83 no problem at FL330.Whats now happening though is that I have a nose up attitude withthe airplane in level flight at speed. Any reason why that mightbe or how to fix? (im using the Ariane payware B732 panel.)I have to say btw, that this is a fabulous bird. I especially love Hornits awesome Piedmont scheme, which is my favorite.ThanksEric

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Mike:Thanks again.I've downloaded it.Sheesh, look at those station loads! Now I am trying to figure out the default ZFW of this bird...JS

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David,In V3.4 you can change the cockpit location in ACL which will move the loading forward or aft as needed. However, all these problems have been fixed in V4. The main issue with V3.4 is that when the CoG is shifted, I wrote the new info to the ref datum point, thus changing everything in the plane. I saw the error of my ways and fixed it in V4 along with loading in general, and true load and balancing.

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Scott,Thank you for responding. I do not understand your explanation. Using FFX 732's original .air file and ACLoader 3.4, I can add and remove passengers with apparently no problems. With the newer .air file, right after I make any modifications, the airplane just sits on its tail. I am not trying to change the cockpit location, just varying the number of passengers. Are you saying that varying the number of passengers/cargo with ACLoader 3.4 changes cockpit location? Dave Vega

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Dave,No, I'm saying that you can move the cockpit location in ACLoader v3.4 to make a work-around for the problem in v3.4. The main problem in 3.4 is that the balance was not correctly calculated. There is also a problem with galley positions in 3.4 not being correct in relation to cabin length, and they could be placed outside the aircraft. And there are some issues regarding cargo hold locations. This does not affect all aircraft, but some react poorly, as you have noticed. It depends on the air file.This has all been solved in v4.

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OK Scott, thanks for the explanation. I just purchased ACLoader V4 and will try it with the FFX 732 as soon as I get my registration number.Regards,Dave Vega

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Dave,Great. Thanks. Number's sent.I hope you like this version a lot better. If you need any help or have suggestions, you can use any of the references in the program. ;-)

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