Nubboy
20th Sep 2010, 13:30
As part of the approach and landing brief on the A320 family, we always look at the perf pages and compare the various speeds. Vapp and Vls are, normally 5kts apart.
Trundling down the last bit of the approach, on a nice calm day and groundspeed mini not sticking it's 2 cents worth in, quite often on the speed tape Vapp and Vls have a much smaller split, say 2 or 3 kts.
My understanding is that the Vapp on the tape is the managed value calculated from the weight data entered into the FMC before engine start, and is therefore only as accurate as the standardised weights given to you on the load sheet, and Vls is measured from the airdata sensors, especially the AoA vanes. Some colleagues suggest adding a few knots to Vapp to make at least a 5kt split on the tape. Others that, in normal law, we have full protection and to leave the speeds as they are.
Following the thread about the Perpignan test flight crash, with frozen or stuck AoA vanes, has anyone any comments. On a normal runway it possibly makes no odds, but short or hot and high, then the energy differences start to add up.
Grateful for your thoughts.
Trundling down the last bit of the approach, on a nice calm day and groundspeed mini not sticking it's 2 cents worth in, quite often on the speed tape Vapp and Vls have a much smaller split, say 2 or 3 kts.
My understanding is that the Vapp on the tape is the managed value calculated from the weight data entered into the FMC before engine start, and is therefore only as accurate as the standardised weights given to you on the load sheet, and Vls is measured from the airdata sensors, especially the AoA vanes. Some colleagues suggest adding a few knots to Vapp to make at least a 5kt split on the tape. Others that, in normal law, we have full protection and to leave the speeds as they are.
Following the thread about the Perpignan test flight crash, with frozen or stuck AoA vanes, has anyone any comments. On a normal runway it possibly makes no odds, but short or hot and high, then the energy differences start to add up.
Grateful for your thoughts.