B707-320C Porpoises

[bluestar]

I have just installed the HJG Boeing 707-320C v6 with the cathay_pacific-707-351cvr-hjg-1975 texture and the b707-323c.1970 panel. While level at FL340 with the autopilot on hold the aircraft will draft between FL339 and FL341 in a one minute osculation. The airspeed is M0.82. I did not change the fuel load and weight and balance from the default. Everything is working correctly except the altitude hold.

I'm running FSX SP1 with Vista at 30 fps.

Is there a cargo fde for this aircraft?

Bill

[benh]

Hmmm........wrong panel for that model I notice there.........

Ben

[bluestar]

Ben

>Hmmm........wrong panel for that model I notice there......... <

It also porpoises with american_airlines_707-323C_n8402_1979 which would be the correct panel.

Bill

[aerofoto - HJG Admin]

It shouldn't porpoise at all .... and to be perfectly honest this's the first report I've seen by anyone regarding any tendancy of our B707's/720's to porpoise !

The only other porpoising act I immediately recall is one which affected "some" (though not all) of our C135 aircraft .... and which was resolved way back in August.

The only minor tendancy to temporarily porpoise is discussed within my "B707 PANELS INSTALLATION - IMPORTANT NOTES" posting which appears on all forum pages. Admittedly these are focussed on FS2004 performance observations, but as I implied above, this is the very first report of any such performance I've seen regarding these aircraft when used with there current version FDE and panels.

You need to be sure you are using our most current gauges/core files package .... that which is now downloadable from our website and not earlier versions of these.

You need to be sure you are using our most current Aircraft Base Packs and FDE .... again that which is currently downloadable from our website and not earlier versions of these .... and additionally for FSX operations you need to be certain you have activated the FSX PANEL.CFG file within your B707 panel folders and not the default FS2004 version, as well as activating the FSX AIRCRAFT.CFG file rather than the default FS2004 version.

Regarding panel/aircraft combinations: You should be using the "B707-320B ADVC" panel with B707-320C type aircraft. The B707-323C 1965 & 1970" panels are intended for use with our AMERICAN AIRLINES B707-323B & C aircraft only .... featuring 2 turbocompressors on the F/E panel as per realworld AA configuration. For further information regarding this kindly view our B707 AIRCRAFT/PANEL information on the "ABOUT HJG AIRCRAFT" page of this forum.

PLEASE NOTE: We will very soon be updating our B707/720 gauges/core files package .... not that there's anything wrong with the version we currently host .... because there isn't anything wrong with it that I can determine. This upddate simply adds a few more nice features to what we currently have. For further information regarding this please refer to the "NEW B707 GAUGES/CORE FILES" posting appearing on the "NEWS" page of this forum.

Mark C
AKL/NZ

[bluestar]

Mark,

As I have stated in my earlier message I am using -

1. HJG Boeing 707-320C v6
2. cathay_pacific-707-351cvr-hjg-1975 texture
3. american_airlines_707-323C_n8402_1979 texture
3. b707-323c.1970 panel - date of the gauge file is 8/9/2007

These are the latest files that are on the HJG website.

As I have stated above, all features of the panel are working including the INS. The aircraft flies fine when not on autopilot. It flies fine when on autopilot except when the altitude hold is activated.

I have already redownloaded and reinstalled all files, but I have not been able to solve the problem.

Bill

[aerofoto - HJG Admin]

Bill .... please remember I can't see what you've actually done there .... of course !

I can only state what I've stated above .... albeit at length .... and with the suggested cross-checks and revisions to perform.

Again .... I can only say it shouldn't porpoise and I've not experienced any of that myself.

And once again .... this's the first report I recollect seeing on such performance associated with any of our B707/720 models.

I'll leave this thread open for our FSX representative to comment further upon when he has time to do so

Mark C
AKL/NZ

[aerofoto - HJG Admin]

Bill ....

Studying this very carefully I think I now know what's going on here to produce the condition you've experienced ....

"IF" one isn't too cautious when engaging ALT HLD at precise increments of altitude it can cause the aircraft to porpoise throughout the cruise.

Allow me to explain properly as follows ....

"IF" one selects ALT HLD "on" at precise increments of altitude .... for e.g 35,000 .... 35,100 .... 35,200 .... 35,300 .... 35,400 .... or 35,500 etc etc etc .... then stable flight is normally ensured.

However .... "IF" one is less cautious and selects ALT HLD "on" at altitude increments of 35,010 .... 35,020 .... 35,030 .... 35,040 .... 35,050 .... or 35,060 etc etc etc .... then this will cause a constant slight porpoising effect much like what you have described.

One needs to be precise when engaging ALT HLD.

It's essential to reduce one's ROC/D to less than 500FTPM during the last 1000FT of any climb/descent to altitude .... and 100-200FTPM is preferrable during the last 500FT of climb/descent to altitude.

It is also essential to pay extremly close attention to the altimeter needles during those last few feet of climb/descent and engage ALT HLD when precise increments of altitude are indicated .... as described above.

Cautious/slow ROC/D during those critical last few feet of climb/descent will both ensure precise increments of altitudecan be captured whenever ALT HLD is engaged .... and promote stable flight too .... barring any meteorological influences you may have programmed into FS and your flights

Mark C
AKL/NZ

[sentry50]

Just out of curiosity...why would it make a difference what altitude you engaged it at? If I engage at 35028, then why wouldn't it try to maintain 35028?

[aerofoto - HJG Admin]

I can't answer that

I'm not a gauge programmer

I can only state what I know it does and from what I've studied and observed myself .... which is as previously explained above

Mark C
AKL/NZ

[bluestar]

Mark,

[at precise increments of altitude .... for e.g 35,000 .... 35,100 .... 35,200 .... 35,300 .... 35,400 .... or 35,500 etc etc etc .... then stable flight is normally ensured]

I have been doing this. Tonight I held the aircraft at FL320 manually for a couple of minutes before engaging the autopilot. Again it held the altitude for about a minute than started the porpoise. I also installed the new gauge pack and there was no change.

I then installed the default B747-400 panel and the porpoise stopped.

Bill

[aerofoto - HJG Admin]

This is odd Bill .... I agree absolutely !

It's even more odd because, despite what I've suggested .... and on the basis of what I've observed and experienced myself during our own extensive pre-release testing periods, you still seem to be the only person experiencing/reporting this issue so far.

PLEASE NOTE: I am by no means implying the problem is in being caused by anything you've done.

To try an understand if there's perhaps any other particular contributing factor applying to your case then please tell us about your PC .... and your Windows Operating System in particular.

In the meantime .... I address the following query to Dan HANSEN .... HJG FSX representative.

Dan .... have you experienced this problem yourself throughout your own very thorough FSX testing ?

Mark C
AKL/NZ

[Dan K. Hansen]

Hi both of you, I'll take a thorough look at this a.s.a.p.

Bill have you turned on the Yaw-dampers? And have you renamed the panel.fsx.cfg to panel.cfg? You may have noticed that there are two versions of the panel.cfg. One for FS9 and one for FSX

Btw, Chris: I see to reason not to be able to hold any odd number of FL as long as you use the correct approach in engaging the ALT HLD. (bit by bit that is) But as you know this is NOT standard according to all aviation rules ;-) But feel free to cruise at FL342,5 if you want. I wont be hunting you for that... :-)

Bill: I'll look into it and see if I get the same problem. I'll try Cathay with the adv panel, and the American Airlines with the AA-configurated panel.

[Dan K. Hansen]

So Bill.

I have now taken American Airlines up to FL340 using the AA-configured panel "panel.b707-323c.1970" as suggested. I climbed steadily up to FL330 and then decreased the trim gradually along with adjusting the throttles to keep a constant IAS at approx. 280 knots. At reaching FL340 exactly I did turn the ALT HLD on (the trim was set to 0 just seconds before) and she levelled out quite nicely.

I let her stay here on a firm course, and sat back..... no fluctuation at all. So I have a nasty feeling of something isn't quite right in your set-up.

To get to the button of this I would suggest you send me the content of your panel.cfg and aircraft.cfg (I presume that you are using the FSX-version of both). either here in a post or better, through PM.

At the same time I would like you to tell me how you switch between your two panels (if you do at all) or how you are sure that you use the mentioned panel.

Another thing would be... which gauge did you take the date from? As each panel uses different gauges.

I would also like to know how you ensure that you are using the correct model for AA and CHX respectively.

Last thing: As FSX SP2 is now freely available from fsinsider.com I would suggest you install the update, as there are several performance improvements amongst other bug-corrections involved in this service pack.

Let's hope we can get to the bottom of this, as you apparently are "one of a kind" ;-)

[aerofoto - HJG Admin]

Thanks for that analysis Dan.

What you've reported there is perfectly I line with my experience too.

Bill .... please provide Dan the information requested so we can try'n pin-point precisely why your experience is different from that of everyone else we're aware of.

Mark C
AKL/NZ

[Dan K. Hansen]

NP.

Once again today. FL340 steady on..... no problems.

Mind you I have real weather set, and it updates every 15 minutes, and we all know how "good" the FS weather engine is.... at the same time I've ticked "Download winds a loft"

These changes in winds forces the trim-wheel/AP to work heavily sometimes, but it always recovers. Not quick as a F16, but nice and slow like......a....... well..... like a B707! ;-)