Jump to content

Archived

This topic is now archived and is closed to further replies.

Thundervil

High V1 speed?

Recommended Posts

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.
R8nOQN8.jpgThanks in advance.


GIANNIS RAPTIS
Boeing777_Banner_Pilot.jpg

 

Share this post


Link to post
Share on other sites

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.


--Peter Fabian 
RTFM.jpg

Share this post


Link to post
Share on other sites

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


GIANNIS RAPTIS
Boeing777_Banner_Pilot.jpg

 

Share this post


Link to post
Share on other sites

Something must be wrong. Note that I am not complaining about my V-speeds, only about my V1 :P
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.


GIANNIS RAPTIS
Boeing777_Banner_Pilot.jpg

 

Share this post


Link to post
Share on other sites

 

 


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.


Kyle Rodgers

Share this post


Link to post
Share on other sites

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.


GIANNIS RAPTIS
Boeing777_Banner_Pilot.jpg

 

Share this post


Link to post
Share on other sites

 

 


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.


Kyle Rodgers

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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...


Kyle Rodgers

Share this post


Link to post
Share on other sites

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

 

 

Thanks Andrei.


Andre Malishkin

 

- I am not a real pilot, but i did stay at holiday inn express -

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.


    50%
    $12,660.00 of $25,000.00 Donate Now
×
×
  • Create New...