assumed temp
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
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From: UK
Smokey
- I'm hoping you did not misread my post there!
Mutt - I think most airlines do it the alexban way for simplicity? Yes, it is the 'wrong' V1, Vr and V2 but as OS says - its a compromise.................
One comment buried within the responses makes me acutely uncomfortable
Mutt - I think most airlines do it the alexban way for simplicity? Yes, it is the 'wrong' V1, Vr and V2 but as OS says - its a compromise.................
Joined: Jun 2004
Posts: 1,843
Likes: 0
From: Australia
No BOAC, it was nothing that you said, but actually one of alexban's where he quoted "The assumed 50C guarantees you'll stop for a TOW of 53T if you use the V1 for 53T.If you're lighter than 53T shouldn't you use corresponding v1?". My discomfort arose from the possible hint within the statement that the lower V1 might be used with the higher Vr/V2.
Quite possibly he was not inferring this, but I wanted to jump on it before someone thought it was a good idea. (See other forums, some have).
The background to some of the differences between Mutt's and my own company's approach is that, as Mutt has indicated on other occasions, his company does not take credit for Stopway and/or Clearway, and directly use the Balanced Field speeds for the actual weight directly from the FMC. We, however, do take credit for Stopway / Clearway, i.e. a non-balanced field which is not acommodated in the FMC, and consequently obtain this V-speed data from the Airport Analysis. For unbalanced field operations, the Airport Analysis is the only PRACTICAL source of data.
Regards,
Old Smokey
Quite possibly he was not inferring this, but I wanted to jump on it before someone thought it was a good idea. (See other forums, some have).
The background to some of the differences between Mutt's and my own company's approach is that, as Mutt has indicated on other occasions, his company does not take credit for Stopway and/or Clearway, and directly use the Balanced Field speeds for the actual weight directly from the FMC. We, however, do take credit for Stopway / Clearway, i.e. a non-balanced field which is not acommodated in the FMC, and consequently obtain this V-speed data from the Airport Analysis. For unbalanced field operations, the Airport Analysis is the only PRACTICAL source of data.
Regards,
Old Smokey
ECON cruise, LR cruise...
Joined: Apr 2002
Posts: 569
Likes: 0
From: MIRSI hold - give or take...
Hi Alex et al...
Had me physics book out in broad daylight for the first time in many years. No matter how I tried to set up the equation - it always came out with mass on one side and mass on the other side as well. I therefore - perhaps falsely
- see them cancelling eachother out exactly, i.e. when comparing braking force available with braking force required, the mass is not a factor, only mju & speed squared. Trying to do the calculation for the same speed (the V1 for 53 T) and mju, but varying the mass (48 T vs. 53 T), I always come up with brake force required being less than brake force available when keeping the speed for 53 T.
The lower V1 for 48 T - well, AFAIK, the FCOM will give you only data for V1min or V1improved, depending on what table you use, whereas the GWC will give you the relevant speed for the particular rwy (i.e. only use V1min when absolutely necessary due field length or close-in obstacles), and as OS said, take into account unbalanced T/O etc. In that way, we are perhaps comparing oranges and apples here?
And regarding the tank - yes, especially firing the gun with level barrel straight ahead & a set of new tracks will do the trick
- you think I could have those as a re-fit on the Merc? 
Brgds from
Empty
Had me physics book out in broad daylight for the first time in many years. No matter how I tried to set up the equation - it always came out with mass on one side and mass on the other side as well. I therefore - perhaps falsely
- see them cancelling eachother out exactly, i.e. when comparing braking force available with braking force required, the mass is not a factor, only mju & speed squared. Trying to do the calculation for the same speed (the V1 for 53 T) and mju, but varying the mass (48 T vs. 53 T), I always come up with brake force required being less than brake force available when keeping the speed for 53 T.The lower V1 for 48 T - well, AFAIK, the FCOM will give you only data for V1min or V1improved, depending on what table you use, whereas the GWC will give you the relevant speed for the particular rwy (i.e. only use V1min when absolutely necessary due field length or close-in obstacles), and as OS said, take into account unbalanced T/O etc. In that way, we are perhaps comparing oranges and apples here?
And regarding the tank - yes, especially firing the gun with level barrel straight ahead & a set of new tracks will do the trick
- you think I could have those as a re-fit on the Merc? Brgds from
Empty
