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Post by walterleo on Apr 26, 2011 18:57:04 GMT
Hi everybody: The CV 990 is a nice airplane & simulation, but it flies at a nose high attitude like Concorde (10 deg up) even at 160 kts full flaps (around 30 to of fuel), which is not realistic. What can be done about that?
Kind regards
Walter
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Post by Dan K. Hansen on Apr 26, 2011 19:40:44 GMT
The attitude is dependant of numerous things.... Altitude, speed, weight etc. etc. So just from your current description it's very difficult to say what you are doing wrong... If you have full flaps and 160 kts, it sounds like you are in approach mode .... and then a nose up attitude is exspected, still depending on weight, speed, etc. etc ... I don't understand the meaning of "around 30 to of fuel" ...?
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Post by aerofoto - HJG Admin on Apr 26, 2011 21:05:11 GMT
Myself and Camilo have this afternoon taken an HJG CV990-A up to FL310 on a test flight .... in response to your report. We maintained a cruising speed of 374 KIAS .... or .... 559 TAS / 0.953 MACH throughout our test flight. The AI in our HJG CV990 panel indicated a 2* degree nose up attitude during our entire cruise. In exterior FS viewing mode this was confirmed by the simulation showing a similar/shallow nose-up attitude in .... as per the following image .... REMEMBER .... the CV990 was a "super-fast" jetliner .... much faster than its contemporary B707 and DC8 counterparts. The CV990 was in fact the CONCORDE of its day .... and cruising airspeeds of between 0.92 to 0.97 MACH were quite normal/ordinary for this particular aircraft .... albeit for absolutely horrendous fuel burn rates whivh never were resolved adequately and were one, of a number of factors, which contributed toi this aircrafts commercial failure. "IF" .... the CV990 is flown too slow .... like at typical B707/DC8 speeds of around 0.80 to 0.83 MACH .... then this aircraft will begin to fly/cruise at an increased AOA/nose-up pitch attitude. I suspect this may be the cause of your problem/observation .... SO .... just keep the speed "UP" in the cruise .... but .... try'n avoid avoid "ringing the bell" ! Mark C BOG/CO
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Post by Herman on Apr 27, 2011 3:18:08 GMT
Dan....I think what Walter means by 30 to is that he has 30 Tons of fuel on board and as you said by the numbers he has given us ie. full flaps and 160kts, he is in the approach phase of flight.
30tons of fuel equates to 60,000lbs appx. which I believe is still fairly high for our jetliners.
I usually try to have about 20% fuel in the tanks for landing and for the CV-990 that would be around 20,000lbs.
I have'nt flown the 990 for a while, so I can't recall what the attitude was for the approach, but I think Walter should try the approach with much less fuel.
Herman
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Post by aerofoto - HJG Admin on Apr 27, 2011 9:56:19 GMT
"IF" .... this´s more of an approach to landing issue rather than a cruise attitude one then "speed" is what could still be causing any nose high AOA. SHIFT+ENTER and SHIFT+BACSPACE keyboard commands (I think it is .... I´m using a Spanish keyboard at the moment which is slightly different) can be used to raise and lower the horizon to improve the RWY during aproaches to landing .... if necessary .... BUT .... if the approach airspeed is good and the simulation properly trimmed too then RWY visibility during approaches to landing should not be any problem Both the CV880 and CV990 had much highrer approach speeds than either the B707 or DC8. In fact the approach to landing airspeed for an unmodified CV880 was around 160-165 KIAS .... according to reference data I´ve seen. When the CV880 was modified with leading eadge slats (resulting in the CV880-M) this then had the effect of reducing approach airspeeds by some 10 KTS .... but .... these aircraft were still very "quick" over the the threshold in comparison with their B707/DC8 counterparts. Flying the CV990 .... and aided by no more than contempory pilot reports only .... I generally fly my approaches to landing at between 155-160 KTS and which results in the following external profile .... which seems "about right" .... The following image represents the CV880-M panel (it's the only one I have accesible at the momentr .... since I don't have time to produce another CV990 specific image), but, it shows that "IF" the speed is about right (high), and the simulation trimmed OK, then RWY visibility should not be any problem .... I can't remember if the above panel image might have been influenced by those recommended SHIFT+ keyboard commands .... I don't think it was though ! Mark C BOG/COL
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Post by walterleo on Apr 27, 2011 13:06:43 GMT
Hi thanks for the quick anserws, what I will try is land it with 10 to of fuel (20.000 p), but in the meantime I made a comparison with HJG DC 8 and found in aircraft.cfg one point which I corrected to 0. Its the line in airplane geometry: pos apex-lon=30. In the DC 8 the value is 0. In the Tu 154M (PT) (another fast plane with high wingsweep) its 4,4 and in the Tu 144 its 34,5. Therefore I think for the CV 990A 30 its too high, for the moment I have put it to 0. Tried out with 1o to of fuel flown at 160 kts its now much better. The 10 to of fuel were only in centertank and the main-tanks. And y changed the zoomfactor of the view from 1 to 0,7. Changing the eye-line with shift enter or shift backspace has its limits, cause after landing you see only concrete in front of you. Kind regards
Walter
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Post by aerofoto - HJG Admin on Apr 27, 2011 13:50:06 GMT
That can happen .... if either of those keyboard commands are struck more than the "once", so, don't do so more than the recommended "once only" .... if at all necessary Those edits you mention are "intersting" .... but will .... of course .... considerably among FS aircraft. I recommend planning fuel loads for each flicght .... so as to avoid landing with much more than a 20% total fuel load remaining fuel load aboard the simulation. Mark C BOG/CO
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Post by christrott on Apr 27, 2011 13:54:00 GMT
Walter, the Wing Apex Position needs to remain 30. The "Wing Apex Pos" is based off the model reference point. Many designers, including Dee (who did the DC-8) use the physical center of the model for that reference point because it's easy to define. However, Erick Cantu, who did the CV880 and CV990, always used the real world Aircraft Reference Point, which is usually the bottom of the nose bulkhead (so the only thing in front of it is the radome). As such, all items that reference off of it will look different from aircraft that use the "central reference point" because of it.
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Post by walterleo on Apr 27, 2011 14:57:44 GMT
Hi: Without provoking a neverending story: I have put in the AoA of the PT Tu 154M and flown the 990A at 150 kts you getwith 8 to of fuel remaining and with the default load alpha 9 deg (the Tu flies on final 6 deg alpha at 265 km/h ) at max landing weight of 80 to. Next try will be wing apex 30 again, lets see, but its clear: This bird should be flown fast and light to the RWY.
Thanks to everybody!
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Post by Herman on Apr 27, 2011 18:07:16 GMT
Just to support some of the previous observations , I took a CV-990 for a circuit at KSEA accompanied with a few screen shots. On the downwind to Rwy34L...clean at 225kts....fuel 27,000lbs. On final, info at top of image On final, full flaps Touchdown The thing that I thought was off somewhat is the low power settings required. Herman
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Post by Mike Monce - HJG on Apr 27, 2011 21:30:46 GMT
walter, Be VERY careful about changing the wing position in the cfg file! This will affect the CoG position and, as you are seeing, affect the flight attitude. However, this can lead to all sorts of other stability and handling issues. If the wing sweep is wrong that also will greatly affect the handling. Comparing the position to other aircraft is the wrong way to go. It depends on the actual aircraft, as well as where the modeler put the reference datum. It's one of the critical parameters in the cfg. I ALWAYS work off of scaled 3 view drawings to set the wing position, but before doing that it must be determined where the ref. datum is as all other measurements are from that position. Without doing all the above things can go bad quick. Mike
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Post by walterleo on Apr 28, 2011 13:46:38 GMT
Hi Thanks, will change back to apex 30, the visibility problem can be solved by Zoom 0.70 or less and the bird has to be flown fast to the RWY. Thanks again
Walter
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Post by aerofoto - HJG Admin on Apr 28, 2011 14:09:17 GMT
One of the "GREAT/OUTSTANGING" performance aspects of the CV880 and CV990 is .... that engine power was available very quickly on these aircraft .... more quickly than was the case in respect of the P&W and RR type engines of the period .... and .... for all of their great speed (despite their horrendous fuel economy for it .... as well as the payload disadvantage impoosed by their naorrower fuselage crossections too) these aircraft could still be slowed "very quickly" too. Even so .... their approach airspeeds were still a lot faster than their B707/DC8 counterparts anyway.
I was reading an article written by a DELTA AIR LINES ex CV880 captain .... published at around the time of DELTA´s withdrawal of their CV880 fleet from service. In this article, this old captain commented, that before the implimentation of airspeed restrictions around mostly US airports ....¨"it was not uncommon to fly approaches, right up to the Outer Marker, with the ASI pointer right on the barber pole .... the aircraft going flat out/as fast as it could go .... before reducing speed at that point, and then still make a perfectly normal landing on the RWY". This old captain also commented additionally that .... "point to point speed records were broken almost daily by DELTA CV880 crews". He also went on to comment, in relation to flying approach speeds fast .... "one FAA inspector apparently one day left a DELTA CV880 quite pale-faced in the light of what he's seen demonstrated .... and that he (the inspector) never, apparently, wrote-up the incident either, fearing nobody would believe what he´s just seen demonstrated in the line of what was, then, routine operations".
Mark C BOG/COL
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