Re: [Flightgear-devel] f16 speedbrakes

2008-09-07 Thread Jon S. Berndt
This would be good to see in a plot. Can you do that? Jon -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Alex Romosan Sent: Saturday, September 06, 2008 5:06 PM To: FlightGear developers discussions Subject: Re: [Flightgear-devel] f16

Re: [Flightgear-devel] f16 speedbrakes

2008-09-07 Thread Alex Romosan
Jon S. Berndt writes: This would be good to see in a plot. Can you do that? i guess jsbsim can do it but i never tried it. any pointers? --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | |

Re: [Flightgear-devel] f16 speedbrakes

2008-09-06 Thread Fabian Grodek
On Fri, Sep 5, 2008 at 11:54 PM, Erik Hofman [EMAIL PROTECTED] wrote: I also see that (I'm only looking at the speedbrakes effects). Two things are unclear for me: 1. The values of alpha in f16.xml are exactly half those in NASA's TP1538 report. 2. The values of the coefficients are

Re: [Flightgear-devel] f16 speedbrakes

2008-09-06 Thread Alex Romosan
Jon S. Berndt writes: I don't know if this matters, but remember that not too long ago we added the ability to enter aero coefficients in several coordinate systems - including BODY and WIND, etc. so if i were to represent the wind tunnel data in x,y,z axis then the drag due to horizontal

Re: [Flightgear-devel] f16 speedbrakes

2008-09-05 Thread Fabian Grodek
On 9/4/08, Alex Romosan [EMAIL PROTECTED] wrote: Erik Hofman writes: Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 i've been looking at it but i can't figure out the relationship between the number in the

Re: [Flightgear-devel] f16 speedbrakes

2008-09-05 Thread Erik Hofman
Fabian Grodek wrote: On 9/4/08, *Alex Romosan* [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: Erik Hofman writes: Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 i've

Re: [Flightgear-devel] f16 speedbrakes

2008-09-05 Thread Jon S. Berndt
Of course you need to transform the data from body axes to wind axes first.. Erik I don't know if this matters, but remember that not too long ago we added the ability to enter aero coefficients in several coordinate systems - including BODY and WIND, etc. Jon

Re: [Flightgear-devel] f16 speedbrakes

2008-09-04 Thread Alex Romosan
Erik Hofman writes: Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 i've been looking at it but i can't figure out the relationship between the number in the report and the numbers in the flightgear model. if

Re: [Flightgear-devel] f16 speedbrakes

2008-08-31 Thread Fabian Grodek
On 8/30/08, Erik Hofman [EMAIL PROTECTED] wrote: ... But I don't see any pitching moment effect; from what I see in NASA TP 1538 http://hdl.handle.net/2002/11034 I understand there is a pitch-down effect from the speedbrakes. It looks like you don't have the latest version of the

Re: [Flightgear-devel] f16 speedbrakes

2008-08-31 Thread Ron Jensen
On Sun, 2008-08-31 at 12:31 +0200, Fabian Grodek wrote: On 8/30/08, Erik Hofman [EMAIL PROTECTED] wrote: ... But I don't see any pitching moment effect; from what I see in NASA TP 1538 http://hdl.handle.net/2002/11034 I understand there is a pitch-down

Re: [Flightgear-devel] f16 speedbrakes

2008-08-30 Thread Erik Hofman
Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build

Re: [Flightgear-devel] f16 speedbrakes

2008-08-30 Thread Erik Hofman
Fabian Grodek wrote: Erik, In the F16 aero config file I see there's indeed an increase in lift for certain speedbrakes deflection, accompanied by the expected huge increase in drag. But I don't see any pitching moment effect; from what I see in NASA TP 1538

Re: [Flightgear-devel] f16 speedbrakes

2008-08-30 Thread Alex Romosan
Erik Hofman writes: Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 thanks. --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible

Re: [Flightgear-devel] f16 speedbrakes

2008-08-29 Thread Erik Hofman
Alex Romosan wrote: i hate to bring this up again but i still think the speedbrakes don't work as they should, instead generating quite a lot of lift. i've tested this on final approach at about 160-170 knots, speedbrakes on; i can keep the plane level. retract the speedbrakes, the plane

Re: [Flightgear-devel] f16 speedbrakes

2008-08-29 Thread Alex Romosan
Erik Hofman writes: Believe me, this is correct behavior, and this is why: i found a nice article about flying in an f16: http://www.avweb.com/news/skywrite/181916-1.html this is the part about the speed brakes: Here's where the speed brakes come in handy, I'll open em up. And you'll

Re: [Flightgear-devel] f16 speedbrakes

2008-08-29 Thread Erik Hofman
Alex Romosan wrote: Erik Hofman writes: Believe me, this is correct behavior, and this is why: i found a nice article about flying in an f16: http://www.avweb.com/news/skywrite/181916-1.html this is the part about the speed brakes: Here's where the speed brakes come in handy,

Re: [Flightgear-devel] f16 speedbrakes

2008-08-29 Thread Alex Romosan
Erik Hofman writes: Alex Romosan wrote: I felt what happens! It seemed my face was being pulled from my skull. I couldn't believe how effective those speed brakes were. An F-16's speed brakes are located at the back of the fuselage either side of the engine nacelle, and really look

Re: [Flightgear-devel] f16 speedbrakes

2008-08-29 Thread gerard robin
On ven 29 août 2008, Erik Hofman wrote: Alex Romosan wrote: Erik Hofman writes: Believe me, this is correct behavior, and this is why: i found a nice article about flying in an f16: http://www.avweb.com/news/skywrite/181916-1.html this is the part about the speed brakes:

Re: [Flightgear-devel] f16 speedbrakes

2008-08-29 Thread Erik Hofman
gerard robin wrote: A Only my 2 cents, if the question is not stupid :) How does the fly-by-wire, regarding the speedbrake lift effect ? What happens (with regard to the fly-by-wire system) is this: Speedbrake deflection causes a pitching moment which the FCS automatically compensates

Re: [Flightgear-devel] f16 speedbrakes

2008-08-29 Thread Erik Hofman
Alex Romosan wrote: Erik Hofman writes: Alex Romosan wrote: I felt what happens! It seemed my face was being pulled from my skull. I couldn't believe how effective those speed brakes were. An F-16's speed brakes are located at the back of the fuselage either side of the engine

Re: [Flightgear-devel] f16 speedbrakes

2008-08-29 Thread Alex Romosan
Erik Hofman writes: Sorry, I got the data from windtunnel test data performed by NASA. can you give me a pointer as to where i could get this data? thanks. --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible

Re: [Flightgear-devel] f16 speedbrakes

2008-08-14 Thread Erik Hofman
Ok, I think I have most of it figured out. I might even consider upgrading the status to 'production' the way it is now. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest

Re: [Flightgear-devel] f16 speedbrakes

2008-08-14 Thread Alex Romosan
Erik Hofman writes: Ok, I think I have most of it figured out. I might even consider upgrading the status to 'production' the way it is now. hmm, i don't know how the real f-16 behaves but i still find the current behaviour a bit strange. level flight, ~350 knots extend the brakes the

Re: [Flightgear-devel] f16 speedbrakes

2008-08-14 Thread Erik Hofman
Alex Romosan wrote: hmm, i don't know how the real f-16 behaves but i still find the current behaviour a bit strange. level flight, ~350 knots extend the brakes the aircraft pitches up slightly and really starts to climb (no effect on the speed at all). push the nose down (quite a lot) to

Re: [Flightgear-devel] f16 speedbrakes

2008-08-14 Thread Erik Hofman
Ok, tested it again. The only way I could reproduce your scenario is not to have the throttle near idle. As I did state earlier, the speeedbrakes of the F-16 are quite small and as it turns out the engine can easily produce enough thrust to overcome the increased drag. Erik

Re: [Flightgear-devel] f16 speedbrakes

2008-08-14 Thread Alex Romosan
Erik Hofman writes: Ok, tested it again. The only way I could reproduce your scenario is not to have the throttle near idle. As I did state earlier, the speeedbrakes of the F-16 are quite small and as it turns out the engine can easily produce enough thrust to overcome the increased drag.

Re: [Flightgear-devel] f16 speedbrakes

2008-08-12 Thread Alex Romosan
Erik Hofman writes: You were right, I had to map speedbrake-pos-norm to speedbrake-pos-rad/deg by using an aerosurface scale section. i think there is still something wrong with the speedbrakes but i am not sure how to quantify this. basically i think they provide way too much lift (which

Re: [Flightgear-devel] f16 speedbrakes

2008-08-12 Thread Erik Hofman
Alex Romosan wrote: i think there is still something wrong with the speedbrakes but i am not sure how to quantify this. basically i think they provide way too much lift (which makes me suspect there is a sign problem somewhere). the effect is more pronounced at slower speeds (250 - 300 knots

Re: [Flightgear-devel] f16 speedbrakes

2008-08-01 Thread Erik Hofman
Alex Romosan wrote: i noticed that on the f16 the speedbrakes have no effect at all and i managed to track it down to the fact that the various coefficients use fcs/mag-speedbrake-pos-rad on input which never gets set anywhere (so it is always 0). digging through the cvs logs i found that

Re: [Flightgear-devel] f16 speedbrakes

2008-08-01 Thread Alex Romosan
Erik Hofman writes: Looking at the code it looks like setting speed-break-pos-norm should be the same as setting speed-break-pos-rad so the patch shouldn't have any effect. look at aero/coefficient/CDDsb or fcs/mag-speedbrake-pos-rad in the property browser. when you deploy the speed brakes

Re: [Flightgear-devel] f16 speedbrakes

2008-08-01 Thread Erik Hofman
Alex Romosan wrote: Erik Hofman writes: Looking at the code it looks like setting speed-break-pos-norm should be the same as setting speed-break-pos-rad so the patch shouldn't have any effect. look at aero/coefficient/CDDsb or fcs/mag-speedbrake-pos-rad in the property browser. when

Re: [Flightgear-devel] f16 speedbrakes

2008-08-01 Thread Erik Hofman
Alex Romosan wrote: Erik Hofman writes: Looking at the code it looks like setting speed-break-pos-norm should be the same as setting speed-break-pos-rad so the patch shouldn't have any effect. look at aero/coefficient/CDDsb or fcs/mag-speedbrake-pos-rad in the property browser. when

[Flightgear-devel] f16 speedbrakes

2008-07-31 Thread Alex Romosan
i noticed that on the f16 the speedbrakes have no effect at all and i managed to track it down to the fact that the various coefficients use fcs/mag-speedbrake-pos-rad on input which never gets set anywhere (so it is always 0). digging through the cvs logs i found that in version 1.17 of f16.xml