c5load
Topic Author
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Takeoff Nomenclature

Sat Dec 11, 2010 9:01 pm

I work on the C-5 Galaxy and when taking off, the word "Go" is pronounced instead of "V1, rotate." Is there really any difference between the two, or is it simply military and civilian?

I also notice that the flight engineer, while on takeoff roll will throw out what sound like times. He will say, "15, 20, time" then after a few seconds the pilot will say go. What does this mean?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
flyinTLow
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RE: Takeoff Nomenclature

Mon Dec 13, 2010 12:55 am

I was told that the word "go" is used just for the rather dumb reason that it is shorter to say. Also it is more of a command to the CM that holds the thrust levers to let go of them in order to avoid an inadvertant takeoff abort.

Just my 2 cents...
- When dreams take flight, follow them -
 
XFSUgimpLB41X
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RE: Takeoff Nomenclature

Mon Dec 13, 2010 7:28 am

V1 is the equivalent of saying "go" as that is the speed above which you can't safely abort.

"rotate" means to begin to bring the nose up which is separate from "V1," and sometimes (not too often though) there can be a difference between V1 and Vr of around 10 or even 15 knots.


The 15, 20 time thing I dont have a clue. We have callouts of "80 knots, throttle hold, thrust normal" which denotes the 80 knots regime change between highspeed and low speed abort, the autothrottle mode change into "throttle hold" when the servos disengage, and "thrust normal" denotes that the engines are set to the appropriate thrust setting and parameters are normal.
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flyinTLow
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RE: Takeoff Nomenclature

Mon Dec 13, 2010 11:54 am

We have the same thing with 100 with the Airbus aircraft. Apart from it seperating the low speed from the high speed regime, it also serves as an IAS/pitot-static probability check. It helps recognize an unreliable airspeed event early.
- When dreams take flight, follow them -
 
Mir
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RE: Takeoff Nomenclature

Mon Dec 13, 2010 1:06 pm

Quoting c5load (Thread starter):
He will say, "15, 20, time" then after a few seconds the pilot will say go. What does this mean?

Could be an acceleration check - I've heard of the military using this for fighters, so they might use it for cargo aircraft as well. Basically, you calculate how long it should take you to get to a certain speed, and if you hit that speed at or before that time (or, alternatively, if the time comes and you are at or above that speed), you know that your engines are performing the way they should be (or better), which in turn means that your V-speed calculations are good. If you don't have the acceleration you think you do, and you try and abort just before V1, you may not have enough room to stop, since you used up more runway that you thought you would to get up to V1 (if that makes sense). Thus, failing to reach that speed in the allotted time would be cause for an abort.

But it seems to me that if you wanted a really good answer, couldn't you just ask the flight engineer?  

-Mir
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spudsmac
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RE: Takeoff Nomenclature

Tue Dec 14, 2010 6:47 pm

Quoting Mir (Reply 4):
Could be an acceleration check - I've heard of the military using this for fighters, so they might use it for cargo aircraft as well. Basically, you calculate how long it should take you to get to a certain speed, and if you hit that speed at or before that time (or, alternatively, if the time comes and you are at or above that speed), you know that your engines are performing the way they should be (or better), which in turn means that your V-speed calculations are good. If you don't have the acceleration you think you do, and you try and abort just before V1, you may not have enough room to stop, since you used up more runway that you thought you would to get up to V1 (if that makes sense). Thus, failing to reach that speed in the allotted time would be cause for an abort.

But it seems to me that if you wanted a really good answer, couldn't you just ask the flight engineer?

-Mir

2

I was thinking the same thing.
 
411A
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RE: Takeoff Nomenclature

Wed Dec 15, 2010 7:47 am

Quoting spudsmac (Reply 5):
I was thinking the same thing.

Your thinking is quite correct, I believe.
This was confirmed by my neighbor, who used to fly B47 bombers, and used similar callouts for an acceleration check during takeoff.

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