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-   -   747.400 Vmca? (https://www.pprune.org/tech-log/144272-747-400-vmca.html)

kerosen 10th Sep 2004 08:04

747.400 Vmca?
 
: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

vmca
 
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.

Milt 10th Sep 2004 11:36

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:

Milt 12th Sep 2004 00:44

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!!


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