Sustained turn rate at 31.5 °/s with flaps on!? - Page 5 - ED Forums
 


Notices

Reply
 
Thread Tools Display Modes
Old 02-15-2020, 02:50 PM   #41
captain_dalan
Senior Member
 
captain_dalan's Avatar
 
Join Date: Mar 2015
Posts: 1,036
Default

Quote:
Originally Posted by Figaro9 View Post
Well, 280kts is not low speed at all. Where in your math is increased drag of flaps?
You only computed lift increase due to weight and flaps (but wrong, 24% boost instead of 14%) and a too high boost due to drag index reduction.

Wings full spread, what is max. aoa according your tunnel test? Config? Thx.
It is slightly more then 225-250, so i decreased the effective L/D for an "arbitrary" value (IIRC about 5-10% - my calcs are at work, so i can't access them now).

What did you use to factor in the full flap effect? I used the decrease in approach speeds with the flaps down. For the same T/W ratio (a rough but plausible estimate considering the small air speed range we are working with here), the extra weight you can lift should be roughly equivalent to the increase in L/D.

Max AoA should be about 32-33 degrees true with wings at 22 degrees sweep.
captain_dalan is offline   Reply With Quote
Old 02-16-2020, 09:05 AM   #42
Figaro9
Junior Member
 
Figaro9's Avatar
 
Join Date: Aug 2016
Location: CH
Posts: 61
Default

I do not want to turn this in a math discussion. I am not a physician and not competent enough in aerodynamics to calculate such complicated things. That is fortunately Devs work. Your simplified math is not a proof that the fm is right nor are your (mis-) calculations a proof that it is wrong. It is still a black box and work in progress, as stated by hb.
I only checked your math and think there are probably mistakes in it. If you want to check/correct, check my post #36.

Natops state that at an oao greater than 25 units (=20 degrees true), lateral control inputs cause the aircraft to feint into the desired direction and then roll/yaw in the opposite direction.
Negativ directional instability at higher speeds occur at 20 units already.
Higher aoa are possible at slow speeds if lift is replaced by engine power... But in a turn we are talking about, critical aoa (lift limit) should be at ~25 units.
Figaro9 is offline   Reply With Quote
Old 02-16-2020, 01:29 PM   #43
captain_dalan
Senior Member
 
captain_dalan's Avatar
 
Join Date: Mar 2015
Posts: 1,036
Default

Dude, i just gave you the equation, you can do the math yourself wit the data you have in the manual

And, lift limit is by no means at 20 degrees, for any wing sweep angle. Not in the sim, not in the wind tunnel data, not in the high AoA study that you can find on google.
captain_dalan is offline   Reply With Quote
Old 02-16-2020, 03:39 PM   #44
Figaro9
Junior Member
 
Figaro9's Avatar
 
Join Date: Aug 2016
Location: CH
Posts: 61
Default

Quote:
Originally Posted by captain_dalan View Post
Dude, i just gave you the equation, you can do the math yourself wit the data you have in the manual

And, lift limit is by no means at 20 degrees, for any wing sweep angle. Not in the sim, not in the wind tunnel data, not in the high AoA study that you can find on google.
Yeah , guestimations and false, simplified math like you did (forgetting drag for flaps and aoa, false readouts, false estimations), that could do just everybody, me too. But it does not help at all. Doing your math gives me ~1g less, dude.

But serious calculations like engineers do , and that is what I was talking about, thats an other story, sorry.

If critical aoa in the sim is above ~25-27units, then I am surprised again, since that is the critical angle for f14a and f14d according natops. Just search for f14 accelerated stall and critical aoa. Search for F14 aoa indexer too. Lot of good reads, have fun.
Figaro9 is offline   Reply With Quote
Old 02-16-2020, 04:00 PM   #45
captain_dalan
Senior Member
 
captain_dalan's Avatar
 
Join Date: Mar 2015
Posts: 1,036
Default

Do you even know what the quotes you posted mean?
The natops figures that is.

Extra points for:

If a plane has approach speed of 150 knots at 50000pds of weight with no flaps, and 150 knots at 55000pds of weight with flaps, then what is the effect of the flaps on the L/D?

Last edited by captain_dalan; 02-16-2020 at 04:03 PM.
captain_dalan is offline   Reply With Quote
Old 02-16-2020, 04:12 PM   #46
HAAUK
Junior Member
 
Join Date: Mar 2019
Posts: 16
Default

i wonder if they modeled different penalities for different flaps positions.... sinced the flaps are analgoue in positioning
HAAUK is offline   Reply With Quote
Old 02-16-2020, 05:32 PM   #47
FWind
Member
 
Join Date: Jul 2011
Posts: 229
Default

Quote:
Originally Posted by captain_dalan View Post
Do you even know what the quotes you posted mean?
The natops figures that is.

Extra points for:

If a plane has approach speed of 150 knots at 50000pds of weight with no flaps, and 150 knots at 55000pds of weight with flaps, then what is the effect of the flaps on the L/D?



Last edited by FWind; 02-16-2020 at 10:26 PM.
FWind is offline   Reply With Quote
Old 02-16-2020, 06:02 PM   #48
Figaro9
Junior Member
 
Figaro9's Avatar
 
Join Date: Aug 2016
Location: CH
Posts: 61
Default

Quote:
Originally Posted by captain_dalan View Post
...
Judging by the effect of full flaps on approach speeds (about 24% boost), with the full flaps down these 4.4 become 5.456...
Nice last ditch dude.

Nope, I am IMC, please make a talk down. ????
Entire quick math, all read outs with reference to natops flight manual pages.

Thanks for your kind help.
Figaro9 is offline   Reply With Quote
Old 02-16-2020, 07:22 PM   #49
captain_dalan
Senior Member
 
captain_dalan's Avatar
 
Join Date: Mar 2015
Posts: 1,036
Default

Quote:
Originally Posted by Figaro9 View Post
Nice last ditch dude.

Nope, I am IMC, please make a talk down. ????
Entire quick math, all read outs with reference to natops flight manual pages.

Thanks for your kind help.
Then enlighten us all, what do roll reversal and negative directional stability have to do with maximum lift?

Quote:
Originally Posted by HAAUK View Post
i wonder if they modeled different penalities for different flaps positions.... sinced the flaps are analgoue in positioning
They said they will increase the drag values for deployed flaps at higher speeds, but i don't know if it made into the latest patch, nor did i had do chance to test the new flight model (apparently changes in the high and low air speed parts of the envelope)

Last edited by captain_dalan; 02-16-2020 at 07:30 PM.
captain_dalan is offline   Reply With Quote
Old 02-17-2020, 04:31 PM   #50
Figaro9
Junior Member
 
Figaro9's Avatar
 
Join Date: Aug 2016
Location: CH
Posts: 61
Default

Quote:
Originally Posted by captain_dalan View Post
Then enlighten us all, what do roll reversal and negative directional stability have to do with maximum lift?
Accelerated stall lines, or lines of maximum lift, represent the maximum load factor that an airplane can produce based on airspeed. The accelerated stall lines are determined by CLmax AOA. They are the curving lines on the left side of the V-n diagram. If one tries to maintain a constant airspeed and increase lift beyond the accelerated stall lines, the airplane will stall because we have exceeded the stalling angle of attack.

At high load factors, the sudden loss of lift from one wing (whichever stalls first ) creates a much larger rolling moment than with a 1-g stall. The result is a violent departure that resembles a snap roll.
Some aircraft tend to roll rapidly toward the outside of the turn, because the the outside wing stalls before the inside wing.
During a rapid departure from controlled flight, the normal CLmax may be momentarily exceeded and as a result, the aircraft could be overstressed or damaged below the corner speed.
Figaro9 is offline   Reply With Quote
Reply

Tags
f-14, f-14 tomcat, f-14a+, f-14b, turn performance

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT. The time now is 08:47 PM. vBulletin Skin by ForumMonkeys. Powered by vBulletin®.
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.