V2 and V2 min ???
Hi,
I'd like to know if someone could explain the meaning of V2 min used on DC-10 and MD-11. What's the difference between V2 and V2 min? Thanks |
Certification requirements specify only minimum values for V2. Manufacturers and operators often choose to use the minimum value of V2 because it will get the aircraft airborne in the shortest distance.
The disadvantage of using the minimum value of V2 is that, for a jet, it may lie on the wrong side of the drag curve and not offer the best climb angle. Some aircraft use 'increased V2' procedures where a V2 higher than the minimum is used giving better climb gradients but taking longer distances to get airborne. The benefit of improved climb gradient can either be used to improve obstacle clearance or to increase the climb limited TOM, sometimes called the WAT limited TOM. |
Yes, that's correct. Airbus is doing it. They call it variable kvs-factor. Performancecalcs are therefore sometimes a little bit hazy.
regards |
V2 MIN = 1.2 X Vs or 1.1 X Vmca, whichever is the higher. Utilised as the lowest V2 allowed, and useful for short field operations, or Takeoff at less than maximum weights for the runway, with the 2nd segment OEI gradient suffering as a result of being at less than "Best Gradient Speed" (Vmd for jets).
Increased Speed V2 = A process of optimisation of 2nd segment OEI gradient generally up to Vmd (for jets) but no upper limit is specified. Field performance suffers as a result of the use of "Increased Speed V2", and therefore it's application is useful only on longer runways. Although no upper limit is specified by the regulations, it is usually approximately 1.4 X Vs at the highest. A fully optimised Airport Analysis may choose a speed between V2 MIN and the optimum OEI best gradient speed, an equal trade-off between Field and Obstacle performance. Leave that one to computerised RTOWs, too hard for humans with sharp pencils. Old Smokey |
At the risk of being labelled a pedant ... a few qualifications to Old Smokey's post, above.
|
All times are GMT. The time now is 04:32. |
Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.