View Full Version : 747.400 Vmca?
kerosen
10th Sep 2004, 08:04
:confused: As I do not know anythings about 747.400 is there any nice boeing pilot to answer thse terrible questions for me?
What is higher Vmcg or Vmca on B 747/400? ( I never imagined it could be something else than vmcg<vmca, but...)
Is there any interrest to teach young student Vmca on airplane rather than simulator?
Thanks to those who could alight my brain!:cool:
windtalker
10th Sep 2004, 10:19
as far as i believe this is a Cathay question.
i did ask a lot of guys, and all comfirmed that Vmca is always higher, in all airplanes
, if i am wrong plz let me know,
Thanks
Windtalker.:zzz:
Capt Fathom
10th Sep 2004, 11:11
747-400:
VMCG
118 - 124 kts
VMCA
112 - 117 kts 1 Engine Out
152 - 160 kts 2 Engines Out
Very simply, VMC calculations generally allow for a slight bank into the live engine. Obviously you cannot bank while still on the ground, you only have rudder, so the VmcG is slightly higher than Vmca1.
Capt Fathom
Please advise if the IASs have been determined after the customary 2 seconds delay following failure before intitiating recovery action.
Mad (Flt) Scientist
10th Sep 2004, 12:22
Vmca is always higher, in all airplanes
This myth again :)
There is nothing which requires that Vmca be either smaller or larger than Vmcg. They are the result of different manoeuvres/tests, at rather different aerodynamic conditions. Therefore there is no way you can point at a single factor and draw the conclusion that one or other must be larger.
It doesn't even have to be consistent on a single airframe for two different flap configurations.
oldebloke
11th Sep 2004, 17:19
Milt,I 'm possably confused but to recover from VMCA is Immediate(once one runs out of rudder control)...
The only time the 2 seconds apply is in the ASDA DISTANCE evaluation...NOT in the recognition/reaction by V!....
Or am I totally at sea???
Cheers:ok:
oldebloke
The reason we TPs use a 2 second delay is to account for an 'average' reaction time to a rapidly deteriorating situation.
This is based on the 'slower reactors' in the system.
If you can beat the 2 seconds you are getting up there towards the above average.
Of course in determining a reasonable Vmcg things can get decidedly pear shaped!!