Dreamflight767

EFB vs. FMS VREF

Recommended Posts

Hello Folks:

When calculating my VREF speed, the EFB and FMS have displayed two different VREF speeds.  Today, the EFB was showing a VREF of 166 while the FMS was saying 145.

I copied the data from the FMS to the EFB but I couldn't get the two figures to agree.

I know...I must be doing something wrong.

Thanks.

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

you can overwrite the values in the FMC if you so choose to. Make sure that the conditions for the calculations are correct. My guess your wind is not entered to either or just one.

Share this post


Link to post
Share on other sites
5 hours ago, Dreamflight767 said:

I copied the data from the FMS to the EFB but I couldn't get the two figures to agree.

There shouldn't be such a difference. Make sure all the data fields on the EFB are the same as in the FMC.

Share this post


Link to post
Share on other sites

166 is the calculated speed with max landing weight (or at least a calculated higher value.) you need to correct your weight by using the inflight data. I can‘t tell you the exact wording now as I am not at my PC but there is an option in the EFB on the right side when you are on the landing calculation page.

Share this post


Link to post
Share on other sites

Marc is referring to the fact that there are two landing calculations, Dispatch and Enroute.  It defaults to Dispatch, change it to Enroute to calculate landing when you are doing your predescent flows.

Share this post


Link to post
Share on other sites

OK.  I'll make that change.  Thanks.  Just out of curiosity, if I uploaded the FMS data to the EFB, why do I have to change from dispatch to enroute?  Weight and weather are the same so why does the EFB calculate differently. 

Share this post


Link to post
Share on other sites
31 minutes ago, Dreamflight767 said:

OK.  I'll make that change.  Thanks.  Just out of curiosity, if I uploaded the FMS data to the EFB, why do I have to change from dispatch to enroute?  Weight and weather are the same so why does the EFB calculate differently. 

Because the regulations are different. 

For planning purposes (ie before dispatch) the aircraft must be able to land within 60% of the available landing distance for a dry runway -- this means you take the actual landing distance at the planned landing weight, multiply this distance by 1.67 and this figure must be less than the available landing distance. If it is not you must reduce the weight until it is. For a wet runway, the factor is 1.92.

Once you are airborne, however, these requirements no longer apply and all that is required is that the commander is satisfied that a safe landing can be made (ie actual unfactored LDR <= LDA).

  • Upvote 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now