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Old 15th Jan 2006, 17:03   #1 (permalink)
 
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Vm* vs MM*

H*y Mat*s, Ca* s*m**** *l*as* *x*lai* th* diff****c* b*tw*** Vm* a*d Mm*? I'm thi*ki*g that Vm* is a limitati** s***d bas*d ** *xc*ssiv* dy*amic ***ssu** f**m flyi*g at high s***ds, whil* Mm* is a limitati** bas*d ** sh*ckwav* damag* f**m flyi*g at high s***ds** Is this c****ct? Als*, I d* **t u*d**sta*d why Vm* cha*g*s with altitud*** I k**w f** *ist** a/c, V** d**s **t cha*g* with altitud*, s* it s**ms l*gical t* m* that Vm* w*uld b* a c**sta*t CAS, whil* **ly th* TAS w*uld cha*g* with altitud*** Tha*ks**
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**t **ally** Th*** a** a sl*w *f **gulati**s which must b* m*t withi* va*i*usly d*fi**d flight **v*l***s** Th* Vm*/Mm* limitati**s actually a**li*d t* a* ai*c*aft a** *ss**tially a c*m**sit* *f th* m*st **st*ictiv* *f th* va*i*us **qui**m**ts - ** th* m*st th* ma*ufactu*** b*th***d t* sh*w, if small**** S*, f** *xam*l*, *** must sh*w **sitiv* di**cti**al stability (** ***-**gativ* di**cti**al stability, if y*u ***f**) withi* th* Vm*/Mm* c**st*ai**d flight **v*l***** *** may fi*d di**cti**al stability ***bl*ms at high Mach, i* which cas* *** **ti** is t* sim*ly 'cut back' th* s***d i* th** **l*va*t a**a** (That's usually ch*a*** by fa* tha* t*yi*g t* **d*sig* a ***bl*m away)** I* additi** t* ha*dli*g c**c***s, Vm*/Mm* may a*is* f**m l*adi*g ** a****lastic c**c***s, ** th* ***d t* mai*tai* ma*gi*s t* d*m**st*at*d ** calculat*d div*/d*sig* s***ds** Th* diff****c* b*tw*** th* tw* is i*d**d th* d*mi*a*c* *f dy*amic ***ssu** ** sh*ck cha*act**istics i* s*tti*g th* limit; but it's **t &qu*t;sh*ckwav* damag*&qu*t;**
Old 15th Jan 2006, 18:17   #2 (permalink)
 
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**: Vm* vs MM*

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**igi*ally **st*d by Macgyv**
H*y Mat*s, Ca* s*m**** *l*as* *x*lai* th* diff****c* b*tw*** Vm* a*d Mm*? I'm thi*ki*g that Vm* is a limitati** s***d bas*d ** *xc*ssiv* dy*amic ***ssu** f**m flyi*g at high s***ds, whil* Mm* is a limitati** bas*d ** sh*ckwav* damag* f**m flyi*g at high s***ds** Is this c****ct?
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Old 15th Jan 2006, 21:47   #3 (permalink)
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**: Vm* vs MM*

Vm* va*iati** with altitud* **fl*cts *AS/IAS va*iati**** Th* **M d**s*'t hav* t* sch*dul* this a*d may *l*ct t* us* a c**sta*t, slightly c**s**vativ* limitati**** **t s*m*thi*g t* w***y ab*ut u*duly**
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Old 18th Jan 2006, 09:51   #4 (permalink)
 
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S*m* ai*c*aft hav* a *ath** st*a*g* l**ki*g s***d **v*l***** Was w**d**i*g mys*lf why** S*m*thi*g lik* 280kt b*l*w 10000' i*c**asi*g li**a*ly t* 320kt at 13000'**
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Vm* is a limitati** im**s*d, as c****ctly stat*d by y*u, t* limit *xc*ssiv* Dy*amic ***ssu** at high** s***ds** As Vm* is *x***ss*d as a CAS, a*d **t *AS (which is a di**ct i*dicati** *f Dy*amic ***ssu**), th* CAS ass*ciat*d with a c**sta*t *AS will i*c**as* with i*c**asi*g altitud*** A Vm* *f, say, 330 CAS (*AS) at S*a L*v*l, w*uld b* *quival**t t* 353 Kt CAS at 30,000 f**t** S*m* ma*ufactu***s **t f** th* va*iabl* 'ba*b** **l*', s*m* **t f** th* sim*l** c**sta*t CAS** F** th* *xam*l* giv**, 330 CAS at 30,000 f**t is **ly 311 Kt *AS, a much l*w** dy*amic ***ssu**** I w*uld **t g* s* fa* as t* say that Mm* is im**s*d t* ***v**t sh*ckwav* damag*, but *ath** t* av*id, ** c**tai* withi* **as**abl* limits th* C**T**L ***bl*ms *f *xc*ssiv* Mach *umb**** w**d**i*g, at fi*st gla*c*, this s**ms lik* a bi*d st*ik* limitati**** Umm, bi*ds d**'t fly ab*v* 10,000 f**t d* th*y? **ga*ds, *ld Sm*k*y
Old 18th Jan 2006, 13:08   #5 (permalink)
 
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**igi*ally **st*d by Macgyv**
H*y Mat*s, Ca* s*m**** *l*as* *x*lai* th* diff****c* b*tw*** Vm* a*d Mm*? I'm thi*ki*g that Vm* is a limitati** s***d bas*d ** *xc*ssiv* dy*amic ***ssu** f**m flyi*g at high s***ds, whil* Mm* is a limitati** bas*d ** sh*ckwav* damag* f**m flyi*g at high s***ds** Is this c****ct? Als*, I d* **t u*d**sta*d why Vm* cha*g*s with altitud*** I k**w f** *ist** a/c, V** d**s **t cha*g* with altitud*, s* it s**ms l*gical t* m* that Vm* w*uld b* a c**sta*t CAS, whil* **ly th* TAS w*uld cha*g* with altitud*** Tha*ks**
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Old 18th Jan 2006, 13:24   #6 (permalink)
 
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Y**, bi*d st*ik* ***t*cti** s**ms t* b* th* *bvi*us** But, th** agai* ch*ck *ut th*s* high altitud* fly**s: htt*://magazi****audub******g/bi*ds/bi*ds0011**html
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Old 19th Jan 2006, 08:36   #7 (permalink)
 
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VM* is a st*uctu*al limitati** ( **t t* b**k* a *a*t *f th* ai*f*am*, say f** *x** th* wi*dshi*ld) a*d is i*c**asi*g with altitud*, a*d MM* is a* a***dy*amic limitati** (**t t* g*t su***s**ic ** wi*gs) a*d d**s *** va*y** H*** it h*l*s!
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Old 19th Jan 2006, 11:12   #8 (permalink)
 
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W* hav* ty**s wh*** Mm* d**s va*y with altitud*; it is **t a giv** that it b* fix*d** **as**s i*clud* ** accu*acy a*d ha*dli*g cha*act**istics which (b*th) va*y with alt**
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Old 19th Jan 2006, 16:03   #9 (permalink)
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<<w**d**i*g, at fi*st gla*c*, this s**ms lik* a bi*d st*ik* limitati**** Umm, bi*ds d**'t fly ab*v* 10,000 f**t d* th*y?>> W*ll if it was*'t a bi*d, I'd l*v* t* k**w what I hit i* a 737 ***th *f *a*l*s at 250kts/11,000'! I **call f**m l**g ag*, a 727 (A*d*s?) hit a la*g* bi*d which cam* i* th**ugh th* *ad*m* a*d might hav* kill*d th* c**il*t- c**tai*ly m*ss*d u* th* c*ck*it, a*d that was u* at 30,000'+
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Old 19th Jan 2006, 20:06   #10 (permalink)
 
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s***d bum*s?

G'day w**d**i*g! What d* y*u wa*t th* s***d ***fil* t* l**k lik*? **ugh Q &am*; A** 35ft ab*v* th* d*ck a*d CAS 175, what will it b* at 1500ft ab*v* a*d cl*a**d u*? Still ab*ut 175? Su***s* y*u th** acc*l**at* i* l*v*l flight t* CAS 250 a*d th** climb? Y*u **ach 10000ft a*d CAS is still 250 but Mach has *is** t* 0**45 a*d TAS t* 290** Y*s? Su***s* y*u th** acc*l**at* i* l*v*l flight t* say CAS 275? H*** y*u l*s* m* a bit** I thi*k y*u'd still climb at a fix*d CAS say 275 but Mach ** a*d TAS w*uld still b* i*c**asi*g** Y*s ** **?[Y*u w*uld*'t alt** s***d agai* u*til say M0**82 but that's a l**g way ab*v* y*u y*t]** Flight *ath a*gl* is di**ctly **lat*d t* (Th*ust-D*ag)/W*ight** H**iz**tal a*d v**tical s***ds a** di**ctly **lat*d th**ugh flight *ath a*gl*** CAS, TAS a*d Mach ** a** **lat*d by f**mula*** Th* **ti**s t* *l*t ***fil* i* t**ms *f CAS, TAS *tc agai*st tim*, dista*c*, h*ight, altitud*, Flight L*v*l a** y*u* ch*ic* but which *a*t l**ks st*a*g*? Th*** will b* c*ggl*s wh** y*u acc*l**at* a*d cha*g* f**m *** **gim* t* a**th** will th*** **t? W**'t th*y b* mutually *x*lai*abl*? *S! Bi*d st*ik*s d* tak* *lac* ab*v* 10000ft** ** a B**i*g data **c**d** th*y a** d*ad ah*ad a*d sh*w u* as m*m**ta*y s***d **ducti**s** ** a* Ai*bus th*y a** f**m d*ad aft a*d sh*w u* as m*m**ta*y s***d i*c**as*s** This *x*lai*s *th**wis* u**x*lai*abl* s***d ***fil* va*iati**s** I'll g*t my c*at Th* &qu*t;*&qu*t;
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Old 20th Jan 2006, 08:47   #11 (permalink)
 
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*h my gawd! I'll hav* t* fi*d th* a******iat* symb*ls ** th* **w ***u** lay*ut** My **f****c* t* &qu*t;bi*ds d**'t fly ab*v* 10,000 f**t d* th*y?&qu*t; was t**gu* i* ch**k, a dig at th*s* ma*ufactu***s wh* im**s* a &qu*t;bi*d&qu*t; limitati** **ly b*l*w 10,000 f**t** I thi*k that (hy**xic?) bi*ds hav* b*** **c*u*t***d w*ll i*t* th* 30 th*usa*ds! **ga*ds, *ld Sm*k*y
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Old 26th Jan 2006, 17:29   #12 (permalink)
 
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Question

@ **icalyth, I **ck** w* a** **t talki*g ab*ut th* sam* thi*g** I was **t **f**i*g t* a tak* *ff/climb ***fil* but t* ai*s***d limitati**s ***g** VM* cha*g*s b*tw*** 10000' a*d 13000' f*m 280kts t* 320kts** I d**t thi*k this mak*s much s**s* f**m a *u**ly a***dy*amic **i*t *f vi*w**
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Old 27th Jan 2006, 14:24   #13 (permalink)
 
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** w**d**i*g, it d**s*'t mak* a*y s**s* f**m a *u**ly a***dy*amic **i*t *f vi*w** T* mak* a*y s**s* *f this situati**, it's **c*ssa*y t* k**w - (1) What a** th* bi*d st*ik* c**sid**ati**s, a*d, m*** im***ta*tly, (2) What is th* ai*c*aft ty**? **ga*ds, *ld Sm*k*y
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Old 27th Jan 2006, 18:49   #14 (permalink)
 
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Hmmm****** My u*d**sta*di*g is that Vm* ca* b* i*flu**c*d by bi*d st*ik* c**tificati** sta*da*ds** Th* c**tificati** sta*da*d f**m FA* 25**571 is &qu*t;Im*act with a 4 lb bi*d at Vc (d*sig* C*uis* S***d) at s*al l*v*l ** 0**85Vc at 8,000 f**t which*v** is m*** c*titical&qu*t;** This is f** a FA* 25 ai*c*aft wi*dshi*ld ** ai*f*am*, f** th* *m****ag* th* s***d is th* sam* but th* bi*d w*ight is 8 lbs (du* t* th* l*ss *f a Visc*u*t i* 1962)** Th* d*sig* **qui**m**t is &qu*t;Th* ai**la** must b* ca*abl* *f succ*ssfully c*m*l*t*i*g a flight du*i*g which lik*ly st*uctu*al damag* *ccu*s&qu*t; (d**s*'t say h*w chall**gi*g that succ*ssfu la*di*g might b* a*d wh*th** y*u g*t t* us* th* ai**la* agai* i* th* **a* futu**)** My **s*a*ch sh*ws that Vc is a fu*cti** *f Vd (D*sig* Div* S***d) a*d Vb (D*sig* S***d f** Maximum Gust I*t**sity)** All th* d*tails i*cludi*g a diag*am a** d*fi**d i* FA* 525**335 with a* *x*la*ati** *f th* ma***uv*i*g **v*l*** c**tai**d i* FA* 525**333** **adi*g i* th* t*xt th*** is a **f****c* that stat*s that Vc ca***t b* g**at** tha* 0**8 Vd** Vm* is **qui**d t* b* l*ss tha* Vd** Bas*d ** my u*d**sta*di*g, if a* ai*c*aft fails th* FA* 25**571 t*st at 280 k**ts th** f*ll*wi*g th* t*ail th**ugh th* th* FA*S w*uld caus* Vm* t* b* limit*d t* s*m* valu* l*ss tha* 280 k**ts** Th **t **sult is that Vm* b*c*m*s limit*d by FA* 25**571 (Bi*d St*ik*) ** FA* 525**333 &am*; 335 which*v** is m*** limiti*g** Just my **i*i** bas*d ** **adi*g v**y c*m*l*x i*t**-li*k*d FA*S by a humbl* *il*t** *icha*d A320 Ca*tai* a*d bi*d st*ik* **s*a*ch**
Canuckbirdstrike is offline  
Just a **t* that that **qui**m**t a**li*s t* ai*c*aft t* which am**dm**t 25-96 (A**** 28, 1998) is a**licabl*; th* ***vi*us v**si** *f th* *ul* (Amdt** 25-86, 61 F* 5222, F*b** 9, 1996) d**s **t ***vid* **li*f at 8,000ft, **qui*i*g 1**0Vc at all altitud*s s**cifi*d** S* d****di*g ** wh** y*u* s**cific ty** was c**tifi*d a*d t* which sta*da*d might i*flu**c* wh*th** bi*dst*ik* is sha*i*g th* Vm* limitati****
Qu*t*:
T*u*, but m*** im***ta*tly, *** FA* 25**1505, Vm* may **t b* g**at** tha* Vc**
Qu*t*:
Qu*t*:
25**1505 is th* k*y t* u*d**sta*di*g s*tti*g Vm*** It *stablish*s a *umb** *f **st*icti**s: 1** **t g**at** tha* th* d*sig* c*uisi*g s***d VC 2** suffici**tly b*l*w VD/MD ** VDF/MDF, t* mak* it highly im***babl* that th* latt** s***ds will b* i*adv**t**tly *xc**d*d i* ****ati**s 3** Th* s***d ma*gi* b*tw*** VM*/MM* a*d VD/MD ** VDF/MDF may **t b* l*ss tha* that d*t**mi**d u*d** 25**335(b) 4** Th* s***d ma*gi* b*tw*** VM*/MM* a*d VD/MD ** VDF/MDF may **t b* l*ss tha* that f*u*d **c*ssa*y du*i*g th* flight t*sts c**duct*d u*d** 25**253 1** is g*i*g t* b* d*iv** by &qu*t;h*w high ca* w* *ush Vc&qu*t; f** th* va*i*us st*uctu*al d*sig* cas*s, i*cludi*g bi*dst*ik*, but als* **ssibly i*cludi*g gust l*ads** 25**341(a)(5)(i) s**cifi*s gust **qui**m**ts as a fu*cti** *f altitud*; if y*u s** Vm* shifts **a* th*s* altitud* b**ak**i*ts it may i*dicat* a gust l*adi*g limitati**:
Qu*t*:
2, 3, a*d 4 a** d*iv** by &qu*t;h*w high ca* w* *ush VD&qu*t; with l*adi*g (a*d flutt**) c**c***s tak** i*t* acc*u*t, a*d als* &qu*t;h*w high ca* w* (** did w*) *ush VDF&qu*t; *LUS th* ai*c*aft u*s*t/*ut-*f-t*im s***d i*c**as* b*havi*u* *** th* **l*va*t **qui**m**ts i* ***g** 25**253 a*d 25**255
Old 27th Jan 2006, 22:18   #15 (permalink)
 
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**igi*ally **st*d by Ca*uckbi*dst*ik*
Th* c**tificati** sta*da*d f**m FA* 25**571 is &qu*t;Im*act with a 4 lb bi*d at Vc (d*sig* C*uis* S***d) at s*al l*v*l ** 0**85Vc at 8,000 f**t which*v** is m*** c*titical&qu*t;** This is f** a FA* 25 ai*c*aft wi*dshi*ld ** ai*f*am*, f** th* *m****ag* th* s***d is th* sam* but th* bi*d w*ight is 8 lbs (du* t* th* l*ss *f a Visc*u*t i* 1962)** Th* d*sig* **qui**m**t is &qu*t;Th* ai**la** must b* ca*abl* *f succ*ssfully c*m*l*t*i*g a flight du*i*g which lik*ly st*uctu*al damag* *ccu*s&qu*t; (d**s*'t say h*w chall**gi*g that succ*ssfu la*di*g might b* a*d wh*th** y*u g*t t* us* th* ai**la* agai* i* th* **a* futu**)**
**igi*ally **st*d by Ca*uckbi*dst*ik*
My **s*a*ch sh*ws that Vc is a fu*cti** *f Vd (D*sig* Div* S***d) a*d Vb (D*sig* S***d f** Maximum Gust I*t**sity)** All th* d*tails i*cludi*g a diag*am a** d*fi**d i* FA* 525**335 with a* *x*la*ati** *f th* ma***uv*i*g **v*l*** c**tai**d i* FA* 525**333** **adi*g i* th* t*xt th*** is a **f****c* that stat*s that Vc ca***t b* g**at** tha* 0**8 Vd** Vm* is **qui**d t* b* l*ss tha* Vd**
**igi*ally **st*d by 25**1505
VM*/MM* must b* *stablish*d s* that it is **t g**at** tha* th* d*sig* c*uisi*g s***d VC
**igi*ally **st*d by Ca*uckbi*dst*ik*
Bas*d ** my u*d**sta*di*g, if a* ai*c*aft fails th* FA* 25**571 t*st at 280 k**ts th** f*ll*wi*g th* t*ail th**ugh th* th* FA*S w*uld caus* Vm* t* b* limit*d t* s*m* valu* l*ss tha* 280 k**ts** Th* **t **sult is that Vm* b*c*m*s limit*d by FA* 25**571 (Bi*d St*ik*) ** FA* 525**333 &am*; 335 which*v** is m*** limiti*g**
**igi*ally **st*d by 25**341(a)(5)(i)
**sitiv* a*d **gativ* gusts with **f****c* gust v*l*citi*s *f 56**0 ft/s*c *AS must b* c**sid***d at s*a l*v*l** Th* **f****c* gust v*l*city may b* **duc*d li**a*ly f**m 56**0 ft/s*c *AS at s*a l*v*l t* 44**0 ft/s*c *AS at 15000 f**t** Th* **f****c* gust v*l*city may b* fu*th** **duc*d li**a*ly f**m 44**0 ft/s*c *AS at 15000 f**t t* 26**0 ft/s*c *AS at 50000 f**t**
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Old 28th Jan 2006, 01:01   #16 (permalink)
 
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Mad (Flt) Sci**tist: Tha*ks f** taki*g th* tim* t* *x*lai* i* d*tail th* s*cti**s *f th* additi**al FA*'s** I had **ad th*s* FA*'s a*d b*li*v*d I had a basic u*d**sta*di*g *f h*w th*y sh*uld b* a**li*d, but did **t f**l c**fid**t i* c*mmu*icati*g a* i*t*****tati** i* a cl*a* a*d c**cis* ma****** Tha*ks als* f** b*i*gi*g i* th* *a*li** v**si** *f FA* 25**571 - I *l*ad ** *xcus* *th** tha* f**g*tfull**ss** As usual a**th** day has g*** by a*d I hav* l*a***d s*m*thi*g** *icha*d
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