High V1 speed?

[Thundervil 0]

Hello everybody, 

I have noticed that the 777 calculates pretty high V1 speeds especially when I am really heavy, is this normal? For example, below is a picture of me taking off from KSFO RW 28R inbound OMDB (lot of fuel) and fully loaded in passengers and cargo. As you can see I am taking off with 95% thust and I had flaps 15. I would expect for my VR and V2 to be so high but what about V1? Can someone explain? Here are my V-speeds calculated by the FMC.
V1: 171
VR: 171
V2: 173
I am 100% sure I wouldn't be able to stop with that little RW left ahead of me if I aborted takeoff at let's say V1-1 knot.
Thanks in advance.

[Fabo 213]

The FMC does not know about runway length. It will not calculate a V1 that makes sure you will be able to stop.

 

The FMC computes a "balanced field" V1, which is, after V1, it will take exactly the same legth to stop as to take off.

It is then your responsibility as a captain to ensure balanced field length for your conditions is less than actual field length.

[Thundervil 0]

So the only solution is to calculate the takeoff speeds on my own?

[AlphaDawg141 71]

Weights?

[Thundervil 0]

I don't exactly remember, my ZFW was 290.1 and my FOB was around 127 Tons, so my weight was around 417 tons.

[Chrjs 61]

Max Takeoff Weight of the 777-200LR is 347,45t - so any questions of why your V-Speeds are that high left.....?

 

http://www.boeing.com/boeing/commercial/777family/pf/pf_lrproduct.page

[Thundervil 0]

Something must be wrong. Note that I am not complaining about my V-speeds, only about my V1
Anyway, the thing is that in my flightplan, (created using simbrief) my ramp fuel was around 127 tons if I remember correctly (in FMC it was shown around 85%) and I had selected full payload and I did not get any errors. I suppose if it couldn't take off wouldn't it have said "V-speeds not available?" or something? Also I didn't get a warning that I had passed my MTOW.

[scandinavian13 5,192]

 

 

I am 100% sure I wouldn't be able to stop with that little RW left ahead of me if I aborted takeoff at let's say V1-1 knot.

 

As mentioned, it calculates "balanced field" v-speeds.  This is not a runway-specific measurement.  As such, your picture isn't at all surprising to me.

Further reading: http://en.wikipedia.org/wiki/Balanced_field_takeoff

 

To calculate runway-specific V₁, you will need to use a program like TOPCAT.

[Thundervil 0]

As mentioned, it calculates "balanced field" v-speeds.  This is not a runway-specific measurement.  As such, your picture isn't at all surprising to me.

Further reading: http://en.wikipedia.org/wiki/Balanced_field_takeoff

 

To calculate runway-specific V₁, you will need to use a program like TOPCAT.

Any freeware tools would be appreciated (if available). I am low on cash, saving for the -300ER expansion Thanks.

[scandinavian13 5,192]

 

 

Any freeware tools would be appreciated (if available).

 

I'm not aware of any, though I'm sure there are a few out there.  I'll leave it up to others to post with recommendations.

[dmayan 1]

So, why the FMC doesn't give any V speed until you fill in the departure runway? Only for fun or to take the runway lenght into the calculation?

 

Diego Mayán

[Tabs 2,790]

Needs to be pointed out that TOPCAT doesn't support the 777 as of yet though. I wouldn't buy it expecting that.

[scandinavian13 5,192]

Needs to be pointed out that TOPCAT doesn't support the 777 as of yet though. I wouldn't buy it expecting that.

 

haha - yeah, good point!  I was just addressing the topic of calculating runway specific speeds in general and blanked on the particular plane we were talking about.  It's definitely Friday...

[amalishkin 10]

are you doing derated takeoff?  and if so 1 2 or temp based drate?  might have to recalc your drates.

 

 

Thanks Andrei.

[thepilot 570]

I noticed that the QRH reference speed for V1 I get with the 737NG is usually lower than the speed TOPCAT computes. I thought this was quite odd.

 

Not sure if TOPCAT is working on a performance file for the 777, but http://www.aurasim.com/ apparently is; as heads-up to whom it may concern.